The role of echocardiography versus
cardiac magnetic resonance in the
cardiovascular diseases assessment
Echokardiografia a magnetyczny rezonans serca w diagnostyce kardiologicznej
stud. Natalia Wiligórska
1, stud. Diana Wiligórska
1, Olga Możeńska, MD
1;
Jacek Bil, MD, PhD
2; Dariusz A. Kosior, MD, PhD, FESC, FACC
1,31 Department of Cardiology and Hypertension, Central Research Hospital of the Ministry of Interior, Warsaw, Poland 2 Department of Invasive Cardiology, Central Research Hospital of the Ministry of Interior, Warsaw, Poland 3 Department of Applied Physiology, Mossakowski Medical Research Centre, Polish Academy of Sciences, Warsaw, Poland Pracę otrzymano: 5.02.2016 Zaakceptowano do druku: 18.02.2016 “Copyright by Medical Education”
INTRODUCTION
Echocardiography is one of the most widely used im-aging modalities in cardiology. Echocardiography pro-vides a large amount of important information about a patient’s cardiovascular status. It plays an important role in confirming the diagnosis, assessing the severi-ty and the prognosis of cardiac diseases, improving the diagnostic accuracy, and revealing the etiology of unex-plained hypertension; it helps in modifying the therapy. Many life-threatening conditions, such as acute myo-cardial infarction, can be defined based on echocardi-ography [1]. It surpasses other imaging modalities in its mobility, handheld devices and the possibility for obtain-ing real-time visualization. There are no limitations in performing echocardiography – it can be performed at the bedside, in the cardiac catheterization laboratory, in the intensive care unit or in the emergency department [2]. This modality provides instantaneous information about the structure, function and hemodynamics of the heart with no need to use contrast enhancement or ion-izing radiation. Echocardiography is a safe technique, with a minimal discomfort or risk for the patient. Its easy repeatability is the unquestionable advantage, especial-ly when there is an alteration in the patient’s status or a need to monitor previously identified disorders [3].
On the other hand, cardiac magnetic resonance (CMR) is well recognized for its value in the initial assessment and monitoring of the wide range of heart and mediastinum diseases [4]. Cardiac magnetic resonance should be used when the results of echocardiography are discrepant or when the quality of echocardiography imaging is inade-quate. When values provided by echocardiography are borderline or ambiguous, CMR is helpful in confirming or changing the echocardiography data before making any clinical decisions [5].
Moreover, CMR has more unquestionable advantages. No application of ionizing radiation or the administration of radioactive isotopes or the iodinated contrast is need-ed to acquire the image. This rneed-educes the risk of devel-oping complications. There are fewer limitations caused by body habitus compared with echocadiography. Car-diac magnetic resonance allows for multiple parameters of the cardiovascular anatomy, structure and function of the heart muscle to be assessed and the myocardial tissue composition to be characterized. By using spectroscopic techniques, it enables visualization and quantification of the myocardial perfusion; it is also possible to define the course and orientation of coronary arteries. Cardiac magnetic resonance is characterized by a relatively high
spatial and temporal resolution, which allows for dis-crimination between normal and abnormal pathologic conditions [6].
TECHNICAL ASPECTS
Echocardiography
In echocardiography, ultrasound beams reflected by in-ner structures are used to visualize cardiac anatomy in one (M [motion]-mode), two (two-dimensional), or three (three-dimensional) dimensions. The use of doppler ex-amination and color flow imaging may be helpful in evalu- ating hemodynamics and the blood flow [7]. The intra-venous administration of contrast agents may be used to depict structures on the left side of the heart more pre-cisely and to show real-time myocardial perfusion [8]. The standard echocardiographic procedure starts with real-time, two-dimensional imaging, which enables us to obtain not only high-resolution images of cardiac struc-tures, but also their movements. Usually the transducer is located in four places of the chest, namely parasternal, apical, subcostal, and suprasternal locations (tab. 1) [9].
Table 1. Projections in echocardiography.
Transducer location Type of projection Parasternal Parasternal long-axis view
Parasternal right ventricular inflow view Parasternal short-axis view
Apical Apical four-chamber view Apical two-chamber view
Subcostal Subcostal four-chamber view Subcostal short-axis view
Suprasternal Suprasternal long-axis view Suprasternal short-axis view
It is possible to measure cardiac dimensions, the area and the volume from two-dimensional images or M-mode re-cordings derived from two-dimensional images [9]. New-er transducNew-ers enable us to obtain three-dimensional or multidimensional images. The full-volume three-dimen-sional echocardiography image can reduce the exami-nation time and minimize variation in the acquisition of images due to the ability to obtain customized, as well as preformatted images [10].
The motion of cardiac structures is visualized by M-mode recording, which is derived from two-dimensional tomo-graphic images. It allows for measurement of the cardiac chambers size and the duration of different phases of the cardiac cycle as well as for visualization of abnormalities of cardiac movements. To measure cardiac dimensions, a M-mode cursor is delineated as a straight line from the transducer position in any direction in the sector to re-cord the motion of a particular cardiac structure. If the ultrasound beam is oblique to the visualized structure, the dimensions can be overestimated [10].
Doppler echocardiography
This modality measures blood flow velocities using the Doppler effect. The ultrasound beam of the known fre-quency is produced by the transducer and transmitted to the heart. Then it is reflected by red blood cells (RBC). The frequency of the reflected ultrasound waves changes according to the direction of RBC motion. Blood flow velocities can be helpful in the assessment of hemody-namic data. Two forms of Doppler echocardiography are distinguished: the pulsed-wave and the continuous-wave form. In pulsed-wave Doppler, a single crystal sends ul-trasound beams with a pulse repetition frequency and re-ceives beams reflected from RBC in a specified location (it is location-specified). In continuous-wave Doppler, ultrasound beams are sent continuously by two separate crystals. Opposite to pulsed-wave Doppler, it measures all frequency shifts and is used to detect the highest flow velocity available.
Color flow imaging or color Doppler
It is a form of pulsed-wave Doppler that displays blood flow or myocardial velocities visualized in different colors, according to the velocity, direction, and turbu-lence. M-mode of color flow imaging can be used to de-termine the timing of different phases of cardiac cycles and to assess the diastolic function or the flow propaga-tion velocity.
Tissue Doppler (TDI) and strain imaging
Tissue Doppler is a modality that is helpful in visualizing motion of tissue or other structures moving with the ve-locity or the frequency shift lower than that of the blood flow.
Both these methods are helpful in evaluating the regional and global systolic and diastolic function and
determin-ing cardiac timdetermin-ing intervals, which are important in the assessment of the cardiac function and the left ventricle (LV) intraventricular mechanical dyssynchrony [11]. Tis-sue Doppler plays a relevant role in assessing diastolic function and estimating diastolic fi Tiss pressures [12, 13].
Contrast echocardiography
There are two modalities in contrast echocardiography. The first one uses agitated saline and it is helpful in iden-tifying a right-to-left intracardiac shunt and improving Doppler signal from the right chambers of the heart. The second one uses gas-filled microbubbles, which are able to pass through the pulmonary circulation improving the definition of the LV endocardial border and the evalua-tion of myocardial perfusion [14].
Three-dimensional echocardiography
Presently, standard echocardiographic examination can visualize heart structure not only in two, but also in three dimensions. It can be done easily by switching between 2D and 3D probes or by switching between 2D and 3D modalities available in the same probe. In 3D echocardio- graphy, it is possible to visualize moving structures in the beating heart thanks to volumetric scanning.
There are two methods which enable us to obtain the three-dimensional image of the heart: the “real-time” mode (or “live” 3D) and the multi-beat 3D mode.
In the real-time mode, data are obtained in a similar way as in conventional 2D echocardiography. A thin sector of a pyramidal 3D volume data set is visualized during the heartbeat. It allows for showing images in several modes, as narrow volume, zoom, wide-angle (full-volume) and color-Doppler modalities. It shows heart dynamics with instantaneous on-line volume rendered reconstruction. There is no need to use reference system, ECG and res-piratory gating and all data are obtained quickly from a single acoustic view that can encompass the entire heart. Data acquisition and analysis with the use of this modal-ity is quick and time-saving. The main disadvantage of real-time mode is a relatively poor spatial and temporal resolution. Nevertheless, this mode is not dependent on arrhythmias or respiratory motion limitations.
In the multi-beat mode, data are acquired with the use of sequential acquisitions of narrow smaller volumes ob-tained from several ECG-gated consecutive heart cycles
(from 2 to 6). To maintain a single volumetric data set, the acquisitions are subsequently stitched together. This method is characterized by a high temporal and spatial resolution and is able to provide large data sets. Howev-er, more artifacts may occur due to patient or respiratory motion, or irregular cardiac rhythms.
Thanks to 3D echocardiography, cardiac structures can be visualized from any desired perspective, irrespective of their orientation and position within the heart, because data sets can be sectioned in several planes and rotated. However, there is a problem with rendering 3D images on flat 2D monitor. In 3D echocardiography, images can be shown in three display modalities: volume rendering, surface rendering and tomographic slices. Volume ren-dering modality uses different colors to convey the depth perception to the observer: lighter colors are used for structures closer to the observer, while darker are used for deeper structures. In surface rendering modality, three-dimensional images are obtained by manual trac-ing or by ustrac-ing automated border detection algorithms on multiple 2D cross-sectional images of the structure of interest. It can be particularly helpful in the assessment of the shape, the geometry and the dynamic function dur-ing the cardiac cycle. There is also a possibility to slice py-ramidal data set in several tomographic views simultane-ously displayed. Cut planes can be orthogonal, parallel or free (any given plane orientation), which can be chosen in order to obtain optimized cross-sections of the heart to solve specific clinical problems and to make accurate measurements [15].
Cardiac magnetic resonance
The basis of this method is imaging of water (and fat, to a lesser extent) because of its abundance in the body. In the absence of external magnetic field (B0), the hydro-gen nuclei (spins) in water or fat molecules are chaot-ically oriented. In the presence of an external magnetic field inside the CMR scanner, the spins pan out parallel or antiparallel to it. The detectable magnetic resonance signal, which is a basis of the created image, is obtained from the difference between the parallel and the antipar-allel spins [16].
Inside a CMR scanner, there is a homogeneous B0 field that has the same strength along each of the three or-thogonal directions (x, y, z) and it is controlled by the computer.
Absorbed electromagnetic energy is released in two mechanisms: longitudinal magnetization recovery and transverse magnetization decay. Longitudinal magneti-zation recovery is characterized by the time constant T1 and is defined as the time to recover 63% of the original longitudinal magnetization vector (z direction). The ra-diofrequency pulse of an appropriate frequency (Larmor frequency) excites protons, which, while returning to the previous state, emit energy in the form of a radiofre-quency (RF) signal. Time T1 is also defined as a spin-lat-tice relaxation.
The transverse magnetization, characterized by the time constant T2, is defined as the time to lose 63% of the transverse magnetization and represent the interac-tion between neighbouring spins (spin-spin interacinterac-tion), which results in exponential loss of the transverse com-ponent of the net magnetization vector. Both T1 and T2 are tissue-specific. Different tissues have various T1 and T2 times, which enables us to obtain images. Only T1 is influenced by the field strength of the scanner [10].
Contrast agents
Intravenous injection of a gadolinium-based contrast agents (GBCAs) can be used during CMR. Perfusion CMR and magnetic resonance angiography are per-formed during first-pass phase (15–30 seconds after the contrast agent injection, during a first pass through the cardiac chamber and blood vessels, before the contrast diffuses into the extracellular space). A second phase is distinguished 10–15 minutes after the injection, when there is a balance between the contrast agent washing into the extracellular space and washing out to the blood pool. Late gadolinium enhancement (LGE) images are obtained during second phase [10].
Contraindications
Not every patient can undergo CMR examination be-cause there are some contraindications, such as: having cochlear implants, neurostimulators, hydrocephalus shunts, metal-containing ocular implants, pacing wires, Swan-Ganz catheters or metallic cerebral aneurysm clips. However, CMR can be safely performed at 1.5 T and even 3 T in patients with devices such as sternal wires, mechanical heart valves and annuloplasty rings, coronary stents, nonmetallic catheters, and orthopedic or dental implants. The problem of patient’s claustro-phobia can be solved by using oral sedation or by
per-forming examination in a scanner with an expanded di-ameter [10].
Permanent pacemaker or cardioverter-defibrillator
Performing CMR in patients with permanent pacemaker or automated implantable cardioverter-defibrillator (ICD) poses a risk and may cause some complications. The metallic hardware can be the source of the electrical current and the magnetic fihar can induce device move-ment. During this examination, inappropriate discharg-ing, sensdischarg-ing, and heating may appear [17]. The tempo-rary pacemaker is an absolute contraindication to CMR and other imaging modalities should be performed in these patients. However, evidence and data from com-bined reports and experienced centres indicate that CMR at 1.5 T or less can be safely performed in a controlled setting among patients with pacemakers produced after 1999 [18].
CONDITIONS
Stable coronary artery disease and acute coronary syndrome (ACS)
The resting two-dimensional and Doppler transthoracic echocardiography (TTE) can estimate the structure and the function of the cardiac muscle. It is particularly rel-evant in visualizing the impaired motion of the heart muscle segments, which increases the probability of coronary artery disease (CAD). Echocardiography can be used also to exclude other causes of patient’s com-plaints, such as valvular heart disease or hypertrophic cardiomyopathy. It can estimate the global ventricular function, which is a useful parameter in estimating the prognosis of patients with stable CAD. Echocardiogra-phy plays a major role in diagnosing patients with mur-murs, symptoms and signs of heart failure or patients who have already suffered myocardial infarction (MI) [19]. Performing echocardiography during acute chest pain can be useful in confirmation or exclusion of my-ocardial ischemia or infarction. When the LV wall mo-tion abnormalities are not visualized, it can, with a high probability, exclude MI. Detecting regional wall motion abnormalities during chest pain can confirm the diag-nosis of MI with a high sensitivity, however with a low specificity [20]. According to visually assessed contrac-tile function of each segment of LV wall, the special score is created: 1 = normal (> 40% thickening with systole);
2 = hypokinesis (10% to 40% thickening); 3 = severe hy-pokinesis to akinesis (< 10% thickening); 4 = dyskinesis; and 5 = aneurysm. Sixteen or seventeen segments are as-sessed also according to this scale. This data allow us to calculate a wall motion score index (WMSI), which can be helpful in semiquantitation of the extent of regional wall motion abnormalities:
WMSI of the healthy LV is 1 and it becomes higher with more severe wall motion abnormalities [10]. Addition-ally, echocardiography can be helpful in the assessment of the ventricular function which is an important part of the risk stratification. The amount of myocardium at risk and the final infarct size after the reperfusion ther-apy can be evaluated with this modality. It can detect complications of MI and evaluate the myocardial viabil-ity. Among patients with nondiagnostic electrocardio-graphic findings and with acute chest pain, echocardi-ography can be helpful in the diagnosis and exclusion of acute MI.
If there are some difficulties in showing akinesis in standard echocardiography procedure, it is possible to perform advanced echocardiography methods with the use of low-dose dobutamine or contrast as well as strain imaging to demonstrate the myocardial viability [21]. Heart failure with preserved ejection fraction (EF) can be detected with the use of tissue Doppler imaging and strain rate measurements. The impaired diastolic filling may indicate an active ischemia and may suggest the microvascular dysfunction.
Echocardiography should be performed in every patient who presents with symptoms of stable CAD for the first time. However, repeating echocardiography is not nec-essary in patients with stable CAD without changes in the clinical status. Resting TTE is recommended (class I, level of evidence B) to: exclude alternative causes of an-gina, identify regional wall motion abnormalities, which may suggest CAD, measure LVEF for the risk stratifica-tion and to evaluate the diastolic funcstratifica-tion [19]. More- over, while performing echocardiography, ultrasound of carotid arteries can also be done with the use of the ap-propriate probe [19].
Conventional 2D echocardiography can only show sin-gle tomographic plane and it is not able to reflect pre-cisely the pathologic involvement of the entire heart. It can help to assess the 3D topography of the risk and infarct volumes. Often because of limited number of acoustic windows in adult patients it can be difficult to obtain parallel cross sections. Simple geometric models are often insufficient in the calculation of risk and infarct volumes due to abnormalities in the shape and function of the heart affected by ischemia. The use of 3D echo-cardiography enables us to make these measurements accurately [22]. Three-dimensional echocardiography can show entire myocardial volume in multi-slice panel, which allows for a thorough evaluation of the whole LV circumference, while conventional 2D echocardiography gives information only about the limited part of myocar-dium. Three-dimensional echocardiography is able to show even limited wall motion abnormalities, localized in regions difficult to visualize in 2D echocardiography. Moreover, the comparison of the regional volume vari-ation of each pyramidal-shaped LV segment during the cardiac cycle is used to make a quantitative analysis of LV regional function. In addition, there is a possibility to use 3D echocardiography while performing stress echo-cardiography in ischemic heart disease. With the use of endocardial 3D surface reconstruction it is possible to evaluate simultaneous LV shape (when ventricle be-comes globular, the sphericity index approaches unity). The sphericity index in 3D echocardiography is better as it can predict LV remodelling earlier than other clinical, echocardiographic or electrocardiographic markers [15]. Three-dimensional echocardiography can be particu-larly helpful when diagnosing RV myocardial infarction. Three dimensional echocardiography allows to evaluate RV geometry, volume, RVEF. It is able to visualize entire RV: inflow and outflow tracts and RV apex [23].
On the other hand, CMR allows us to obtain high resolu-tion images in any plane with no need to use ionising ra-diation, assess both global and regional cardiac function, depict myocardial perfusion, myocardial viability, char-acterize cardiac tissue and visualize proximal coronary arteries anatomy. Due to its multi-parametric approach, CMR is exceptionally important in the detection of CAD. CMR can be used to stratify the risk in patients with CAD and to guide treatment and revascularization because of its ability to detect and localize ischemia, estimate ischemic
burden and assess myocardial viability. In stable CAD, CMR allows for assessment of the volume and function of LV, stress and rest perfusion for myocardial ischemia. Also, it can delineate the scar and assess the viability with the use of late gadolinium enhancement (LGE).
LGE imaging is one of the most precise non-invasive method in quantifying the infarct size and the heart mor-phology [24]. It can be used to confirm the presence of ischemia, determine its size and location because of the differences in contrast distribution in the normal and in-jured tissue [25]. There is a correlation between MI size or MI transmurality visualized with LGE and the level of MI markers (serum creatine kinase), time to treatment as well as incomplete electrocardiographic ST-segment resolution [26]. Regions of microvascular obstruction, visible as a dense hypoenhanced area within the core of a bright region of infarction, can be detected with LGE imaging performed within the first 5 minutes after con-trast injection [18]. Thanks to its high spatial resolution and a high contrast-to-noise-ratio, LGE imaging sur-passes single-photon emission computed tomography (SPECT) or positron emission tomography (PET) in de-tecting subendocardial MI, which can be unrecognized by these two modalities [27]. Among patients with clin-ically recognized MI, LGE can be used as a prognostic factor. LGE scar transmurality index may be a strong in-dependent predictor factor of death or cardiac transplan-tation, which also indirectly gives prognosis to LVEF [28]. Visualization of the tissue inhomogeneity in LGE im- ages can indicate the substrate of arrythmias, which often complicates MI [29].
Moreover, vasodilatory or inotropic stress agents can be used to demonstrate hypoperfusion and detect CAD. CMR is a valuable tool in diagnosing both patients after ST-segment and non-ST-segment elevation ACS. It sur-passes traditionally used LVEF in predicting the outcome due to the ability to estimate the probability of the func-tional recovery after revascularization, to evaluate the area of myocardium at risk (myocardial edema), to dis-tinguish acute from chronic infarction and to visualize microvascular obstruction (MO) and intramyocardial hemorrhage (IMH).
CMR surpasses echocardiography in identifying ven-tricular thrombi, which appear as dark filling defects on
early gadolinium enhancement (EGE) or LGE imaging. CMR may also be useful in detecting other complications of MI, such as ventricular aneurysm, pseudoaneurysms, ventricular septal perforation and mitral regurgitation. Furthermore, the high spatial resolution of CMR allows us to estimate right ventricular involvement in acute MI [25]. CMR may provide precise information about athero-sclerotic plaque of the carotid artery and descending aorta. It can describe its structure and activity. Two con-trast-weighted imaging sequences are used to visualize carotid plaque fibrous cap, hemorrhage, calcifications, and loose matrix. Moreover, LGE T1-weighted imaging may be used to distinguish fibrous cap from necrotic or lipid core [30].
Cardiomyopathies
Hypertrophic cardiomyopathy (HCM)
Two-dimensional and Doppler echocardiography are first-line methods to diagnose HCM, to evaluate the disease distribution and to assess its functional conse- quences [31]. However, they are associated with some technical limitations. Adequate acoustic window has an impact on delineation of LV wall thickness in a reliable way. Moreover, cross-sectional images can be obtained with the obliquity due to the fact that an echocardiograph-ic transducer is located on the anterior chest wall [32]. The deformational geometry of the LV outflow tract (LVOT) and the mechanics of systolic anterior motion (SAM), which are characteristic for HCM, can be ac-curately visualized with the use of 3D echocardiogra-phy [33]. Mainly the medial segments of the mitral valve are involved in SAM, which causes laterally located nar-rowing of LVOT [34]. Three-dimensional echocardiogra-phy enables to evaluate LVOT area after alcohol ablation or surgical myectomy. It is also helpful in assessment of the left atrial mechanical function, the estimation of LVEF and the LV mass [35]. Moreover, the location and the ex-tent of LV cavity obliteration can be delineated more pre-cisely with the use of live 3D echocardiography [36]. On the other hand, images obtained with CMR are high-resolution and nonoblique. The contrast at the en-docardial borders is uniform, all levels and regions of the LV are encompassed and it is possible to make complete reconstruction of the chambers. Because of these proper-ties, CMR is able to visualize segmental wall thickening in
any area of the LV wall, even small ones and can be the source of additional morphological information to the findings obtained in TTE [32]. CMR imaging allows for the localization of the hypertrophy precisely, especially at the apex of LV. CMR myocardial tagging is useful in vis-ualizing abnormal patterns of strain, shear and torsion. LGE CMR can show areas of fibrosis, which is associated with a higher risk of sudden death and the development of LV dilation and heart failure. CMR is relevant in screen-ing the relatives of probands due to its accuracy and the possibility to detect abnormal myocardium, which is re-sponsible for the increased risk of cardiac events. It should be particularly recommended in patients in whom the re-sults of TTE are technically unsatisfactory [31].
Dilated cardiomyopathy (DCM)
Although there are various causes of DCM, the idiopath-ic DCM is the most frequently observed one. TTE is cru-cial in establishing diagnosis of DCM. The most charac-teristic feature seen during echocardiography examina-tion is LV dilataexamina-tion and/or dysfuncexamina-tion. Dilataexamina-tion may occur earlier than dysfunction, and it is important to pay attention to chamber dimensions, indexed according to body surface area. It is especially helpful in long-term fol-low-up, while evaluating DCM progression and response to treatment [37].
There are the following echocardiographic criteria in di-agnosis of DCM:
1. Ejection fraction of the left ventricle < 0.45 (> 2 SD) and/or factional shortening < 25% (> 2 SD), as ascer-tained by echocardiography radionuclide scanning or angiography.
2. Left ventricular end-diastolic diameter > 117% of the predicted value corrected for age and body surface area, which corresponds to 2 SD of the predicted nor-mal limit + 5%.
To diagnose idiopathic DCM, it is necessary to exclude the following criteria:
• systemic arterial hypertension (> 160/100 mmHg do-cumented and confirmed at repeated measurements and/or evidence of target-organ disease)
• coronary heart disease (obstruction > 50% of the lu-minal diameter in a major branch)
• history of chronic excess of alcohol consumption with remission of dilated cardiomyopathy after 6 months of abstinence • clinical, sustained and rapid supraventricular arrhy-thmias • systemic diseases • pericardial diseases • congenital heart disease • cor pulmonale.
The diagnosis of familial DCM is established, when the following criteria are fulfilled:
• the presence of two or more affected individuals in a single family
• the presence of a first-degree relative of a DCM pa-tient, with well documented unexplained sudden death at < 35 years of age [38].
It may be difficult to use these criteria in some cases, especially in young patients, and apply only short axis dimensions. However, it has been suggested to screen family members with the use of the cut-off point of left ventricular end diastolic dimension at > 117% of predict-ed values to increase specificity [38].
In some patients with DCM, conventional 2D echocar-diography may be suboptimal in the evaluation of the geometry, function of the LV and localized abnormal-ities such as ventricular aneurysm. Then, 3D echocar-diography may be performed as it for assessment of the cardiac function in a faster way and at a lower cost than CMR [39]. Furthermore, 3D echocardiography can be helpful in the accurate determination of LV mass when 2D echocardiography is not sufficient due to assump-tions of the ventricular geometry and image plane posi-tioning. Measurements of LV mass obtained with the use of 3D echocardiography demonstrate significantly better correlation with CMR than these obtained with 2D echo-cardiography [40, 41]. Therefore, 3D echoecho-cardiography may be considered in clinical practice in patients with DCM [41]. In addition, real-time 3D echocardiography is a simple and feasible method for quantifying the LV re-gional systolic function and dyssynchrony [42].
The method of choice to determine the etiology of DCM is CMR. It can easily visualize the morphological and functional abnormalities of this condition; however, these findings may not be easily differentiated from oth-er forms of LV dysfunction, such as that resulting from CAD [31]. For this reason, CMR study in DCM should always include LGE images, which can provide
informa-tion relevant in tissue characterizainforma-tion and useful to dis-tinguish DCM and other causes of dilated LV. CMR with LGE sequences can be also used to evaluate the degree of fibrosis and the prognostic significance of the fibrosis in patients with DCM [43]. In addition, CMR is superior in depiction of dilation of the RV, which is possible in DCM. CMR can also assess the quantitative effects of therapy [31].
Arrythmogenic right ventricle cardiomyopathy (ARVC)
Arrythmogenic right ventricle cardiomyopathy is an un-common disease, which affects myocardium. Ventricu-lar arrhythmias, sudden cardiac death, heart failure, and the replacement of myocytes by fibro-fatty tissue, mostly in the area of RV, are characteristic for ARVC. Diagno-sis is based on several major and minor criteria, which concern family history, arrhythmias, abnormalities in electrocardiography, genetic disorders, tissue characteri-zation, and functional and/or structural abnormalities on imaging [44].
Due to availability, low cost, ease of performance and interpretation of the results, TTE is commonly used to establish the diagnosis of ARVC. It is able to show both functional and structural abnormalities: wall motion abnormalities, global RV impaired systolic function, RV global and/or segmental dilatation, aneurysms, sac-culations, wall thinning, moderator band hyperreflec-tivity, and trabecular derangement. Nevertheless, ob-taining appropriate echocardiography images and their evaluation depends on the operator, and therefore it is subjective and qualitative. The diagnosis based on TTE is difficult because of the lack of standardized echocardi-ographic criteria for ARVC. Valid criteria were proposed by the Task Force of the Working Group on Cardiomyo-pathies in 1994. They are divided into major and minor criteria. Histological, structural and electrocardiograph-ic parameters are evaluated to make the proper diagno-sis [45]. However, since then, new imaging modalities have appeared and it is possible to quantify findings in obtained images more precisely. Thus, diagnostic crite-ria have been modified and include new knowledge and technology, but they are based on quantitative parame-ters for Task Force criteria (tab. 2) [46].
Geometrical assumptions based on 2D acquisition may be insufficient for the RV assessment due to its retros-ternal location and complex crescent geometry.
There-fore, volumetric calculation cannot be done accurately. Three-dimensional echocardiography can overcome these limitations and it can evaluate RV volumes and EF, unlike CMR [47, 48]. It can reveal subtle global RV sys-tolic dysfunction in the early stages of ARVC and may be helpful in its early diagnosis [49]. The acoustic dropout of RV free wall and anterior wall in patients with dilated RV may be the limitation of the use of 3D echocardiogra-phy in some cases. Moreover, the abnormal RV shape in patients with ARVC and large saccular aneurysms may be caused by the current software algorithms. Therefore, in these patients this modality presents a low yield. To overcome these limitations, there is a possibility to use 3D-based RV reconstruction to assess RV volumes and function in these patients [50, 51]. Three-dimensional echocardiography is not routinely performed to make diagnosis of ARVC, because it is a new imaging meth-od and it is still developing [46]. However, the use of this method together with other modalities can prevent false-negative findings and can be useful in the evalua-tion of RV volume and funcevalua-tion [49, 52].
CMR is especially useful in the diagnosis of ARVC [44]. Diagnostic criteria of ARVC, which can be identified by CMR in the RV, include regional wall motion abnormali-ties, increased RV volumes with quantification, morpho-logical abnormalities (aneurysms, trabecular disarray) and fatty infiltration of myocardium [31]. It provides three-dimensional visualization of myocardial patholo-gies that may mimic ARVC, such as thoracic abnormal-ities, abnormal heart positions that can cause distortion of RV shape, false regional wall motion and ECG abnor-malities. CMR can also differentiate ARVC from sar-coidosis, RV infarction and left-to-right shunt leading to RV dilatation [44].
According to original Task Force Criteria, if 2 major, 1 major and 2 minor, or 4 minor criteria from different groups (global or regional dysfunction or structural al-teration, tissue characterization of wall, repolarization abnormalities, depolarization/conduction abnormali-ties, arrhythmias, family history) are fulfilled, ARVC can be diagnosed. The diagnosis of ARVC based on Revised Task Force Criteria can be made in the presence of 2 ma-jor, 1 major and 2 minor or 4 minor criteria from differ-ent categories. The diagnosis is borderline when 1 major and 1 minor or 3 minor criteria from different categories are fulfilled. It is possible to diagnose ARVC in the
pres-ence of 1 major or 2 minor criteria from different catego-ries [53].
Restrictive cardiomyopathy (RCM)
RCM is the least common type of cardiomyopathies. Unlike other cardiomyopathies, it is distinguished on the basis of functional, not morphological criteria. The characteristic feature of RCM is increased myocardi-um stiffness, which is the cause of a sudden increase in ventricular pressure with minimal increase in ventricu-lar volume [54]. The most common causes of RCM are:
amyloidosis, haemochromatosis, sarcoidosis, Fabry’s disease, and glycogen storage. There are also Loeffler’s cardiomyopathy, resulting from hypereosynophilic syn-drome and idiopathic RCM. Echocardiography is the first-line imaging tool used to diagnose RCM. Echocar-diographic features that should suggest RCM are: biatrial dilatation, hypertrophied ventricles with decreased com-pliance, small LV (normal or reduced ventricular diastolic volumes), and normal to depressed systolic function [55]. Partial LV or RV apical obliteration are characteristic of RCM in an echocardiography image [56]. During echo-cardiography examination the following phenomena may be seen: normal systolic contraction, rapid but ill-sus-tained ventricular filling seen on pulsed-wave Doppler (E-wave) and little or no late ventricular filling (A-wave). Restrictive physiology is the basis of this filling pattern [54]. Moreover, TTE may be helpful in the differential di-agnosis between RCM and constrictive pericarditis (CP). It is crucial since CP is curable by surgical pericardial re-section, as opposed to RCM [54]. Comparing respiratory changes in transvalvular flow velocities may be helpful in making proper differentiation [57]. During inspira-tion, the transmitral velocities are reduced (E-wave) and tricuspid velocities increased (E-wave) in CP, while they are unchanged in RCM [54]. Additionally, diastolic mi-tral and tricuspid regurgitations occur more frequently among patients with RCM (tab. 4) [57].
Table 2. Comparison of Original and Revised Task Force Criteria of ARVC. Modified, based on [46, 53].
Original Task Force Criteria Revised Task Force Criteria
MAJOR
• severe dilatation and reduction of RV ejection fraction with no (or only mild) LV impairment • localized RV aneurysms (aki-netic or dyski(aki-netic areas with diastolic bulging)
• severe segmental dilatation of the RV
By 2D echo:
• regional RV akinesia, dyskinesia, or aneurysm • and 1 of the following (end diastole):
• PLAX RVOT ≥ 32 mm (corrected for body size [PLAX/BSA] ≥ 19 mm/m2)
• PSAX RVOT ≥ 36 mm (corrected for body size [PSAX/BSA] ≥ 21 mm/m2)
• or fractional area change ≤ 33%
By MRI:
• regional RV akinesia or dyskinesia or dyssynchronous RV contraction • and 1 of the following:
• ratio of RV end-diastolic volume to BSA ≥ 110 ml/m2 (male) or ≥ 100 ml/m2 (female)
• or RV ejection fraction ≤ 40% MINOR
• mild global RV dilatation and/or ejection fraction reduction with normal LV
• mild segmental dilatation of the RV
• regional RV hypokinesia
By 2D echo:
• regional RV akinesia or dyskinesia • and 1 of the following (end diastole):
• PLAX RVOT ≥ 29 to < 32 mm (corrected for body size [PLAX/BSA] ≥ 16 to < 19 mm/m2)
• PSAX RVOT ≥ 32 to < 36 mm (corrected for body size [PSAX/BSA] ≥ 18 to < 21 mm/m2)
• or fractional area change > 33% to ≤ 40%
By MRI:
• regional RV akinesia or dyskinesia or dyssynchronous RV contraction • and 1 of the following:
• ratio of RV end-diastolic volume to BSA ≥ 100 to < 110 ml/m2 (male) or ≥ 90 to < 100 ml/m2 (female)
• or RV ejection fraction > 40% to ≤ 45%
Table 3. The diagnosis of ARVC based on Original and
Re-vised Task Force Criteria. Modified, based on [53]. The diagnosis
of ARVC Task Force Criteria Revised Task Force Criteria Certain 2 major criteria/
1 major + 2 minor criteria/ 4 minor criteria from different categories 2 major criteria/ 1 major + 2 minor criteria/ 4 minor criteria
from different categories
Borderline - 1 major + 1 minor criteria/ 3 minor criteria
from different categories
Possible - 1 major criterion/ 2 minor criteria from different categories
In patients with RCM, due to cardiac amyloidosis nov-el non-invasive modalities such as 3D echocardiography can be helpful in making a proper diagnosis when CMR cannot be performed, because of e.g. implantable devices. Three-dimensional echocardiography can evaluate LV function and quantify the dispersion of timing to peak systole among different ventricular regions, which deter-mines intraventricular dyssynchrony [58]. Dyssynchrony measured with the use of systolic timing among 16 seg-ments reflects systolic dysfunction [59, 60]. Furthermore, 3D speckle tracking echocardiography gives the oppor-tunity to differentiate cardiac amyloidosis, which leads to RCM, and HCM. It is possible due to basoapical radial strain gradient which differs in these two conditions. This suggests a “function-pattern-based” differentiation of amyloidosis and HCM [61].
CMR may be complementary to TTE in diagnosing RCM. The important value of CMR is the ability to delineate the presence of myocardial fibrosis, which may help in
assess-ing prognosis [54]. CMR is also able to distassess-inguish it from constrictive pericarditis. Both of these diseases are char-acterized by reduced ventricular filling and diastolic vol-umes; in constrictive pericarditis, pericardial thickening can be seen. Techniques such as cine-CMR assessment of diastolic ventricular septal movements and real-time cine-CMR evaluation of septal motion during respiration can differentiate these diseases even if the thickening in constrictive pericarditis is minimal. The differentiation is based on the fact that in RCM, septal convexity is main-tained in all respiratory phases, while in constrictive peri-carditis, septal flattening is visible in early inspiration [43].
Left ventricle noncompaction cardiomyopathy, left ventricular non-compaction (LVNC)
Echocardiography is the diagnostic test of choice for LVNC, but other imaging methods, including CMR may be used for the diagnosis [63]. Flow Doppler and two-dimensional echocardiographic criteria are used to diagnose LVNC: the absence of any coexisting cardiac
Table 4. Differential diagnosis of RCM and CP. Modified, based on [62].
Method Restrictive cardiomyopathy Constrictive pericarditis
Clinical
presen-tation • Kussmaul’s sign +/- , apical impulse +++• S3 (advanced), S4 (early disease), regurgitant murmurs ++ • Kussmaul’s sign+, apical impulse -• pericardial knock+, regurgitant murmurs -2D
echocardio-graphy • small LV cavity with large atria• increased wall thickness sometimes present (especially thickened interatrial septum in amyloidosis)
• thickened valves and granular sparkling (amyloidosis)
• normal wall thickness
• pericardial thickening, prominent early diastolic filling with abrupt displacement of IVS
Doppler studies : Mitral flow Pulmonary vein Tricuspid inflow
Hepatic vein Inferior vena cava
• no respiration variation of mitral inflow E-wave velocity, IVRT • E/A ratio ≥ 2, short DT, diastolic regurgitation
• blunted S/D ratio (0.5), prominent and prolonged AR • no respiration variation, D-wave
• mild respiration variation of tricuspid inflow E-wave velocity • E/A ratio ≥ 2, TR peak velocity, no significant respiration
change
• short DT with inspiration, diastolic regurgitation • blunted S/D ratio, increased inspiratory reversals • plethoric
• inspiration: decreased inflow E-wave velocity, prolonged IVRT • expiration: opposite changes, short DT, diastolic regurgitation • S/D ratio = 1, inspiration: decreased PV S and D waves • expiration: opposite changes
• inspiration: increased tricuspid inflow E-wave velocity, increased TR peak velocity
• expiration: opposite changes • short DT, diastolic regurgitation
• inspiration: minimally increased HV S and D
• expiration: decreased diastolic flow/increased reversals • plethoric
Color M-mode • slow flow propagation • rapid flow propagation (≥ 100 cm/s)
Mitral annular motion
• low-velocity early filling (< 8 cm/s) • high-velocity early filling (≥ 8 cm/s) Tissue Doppler
echocardiography • peak early velocity of longitudinal expansion (peak Ea) of ≥ 8.0 cm/s (89% sensitivity and 100% specificity) • negative
CT/MRI • pericardium usually normal • pericardium must be thickened or calcified
anomalies, the characteristic appearance of numerous, excessively prominent trabeculations and deep intertra-becular recesses, intertraintertra-becular spaces filled by direct blood flow from the ventricular cavity, as visualized on color Doppler imaging, a maximum end-systolic ra-tio of noncompacted to compacted layers of > 2 [64]. Contrast-enhanced echocardiography can be used as a non-invasive method, which enables us to visualize the endocardial blood-interface more precisely. This method is recommended in the diagnosis of LVNC because of better ability to depict the trabeculae and deep intratra-becular recesses, also the intertraintratra-becular spaces filled by microbubbles [65].
When images obtained with 2D echocardiography are ambiguous, 3D echocardiography can be used to make the final diagnosis of LVNC. Moreover, this mo-dality can be also helpful in detecting intertrabecular clots [66]. It enables us to make the proper diagnosis thanks to the detailed characteristics of the extent of the affected heart muscle in LVNC [67]. The differentiation between compact and noncompact LV myocardium can be easily made with the use of 3D echocardiography. In addition, it gives good, simultaneous visualization of the entire trabecular projections and intertrabecular recess-es. It can simultaneously reveal wall motion abnormal-ities in vast areas of myocardium. Data obtained with the use of 3D echocardiography surpass these obtained in 2D echocardiography, because pyramid-shaped visu-alization encompasses the entire LV. Left ventricle can be sectioned in many planes, which can be used multi-ple times and in various angles. There is a possibility to demonstrate intracavitary echodensities, which are sus-pected for trabeculations in many directions from base to apex. These images allow for showing entire trabec-ulation. Furthermore, 3D echocardiography provides the possibility to visualize deep intertrabecular recesses and the distinction between the prominent noncompact heart muscle and the thin compact layer of LV myocar-dium [68].
Although both 3D and contrast echocardiography can improve the assessment of this cardiomyopathy, CMR can also be useful in its diagnosis. Due to the spatial res-olution of CMR, its ability to assess function of heart muscle and the possibility to characterize tissue by the late-gadolinium hyperenhancement sequence, CMR can play a major role in the diagnosis of LVNC. LGE can
visualize myocardial fibrosis, which correlates with clini-cal severity and ventricular dysfunction in patients with LVNC and which can be used as a marker of poor prog-nosis in risk-stratification [69].
Takotsubo cardiomyopathy (TTC)
Echocardiography is usually the initial imaging method used to assess patients with TTC. It can provide relevant information about LV morphology and its regional and global function. Localization of wall motion abnormal-ities can help to distinguish different LV morphologic patterns. Abnormalities that affect midventricular seg-ments of the anterior, inferior, and lateral walls (so-called circumferential pattern) should suggest the diagnosis of TTC. Additionally, advanced echocardiographic tech-niques, such as speckle-tracking, myocardial contrast, and coronary flow studies, can be the source of informa-tion about the mechanism and pathophysiology of TTC. Echocardiography can help to identify potential compli-cations of TTC, such as LV outflow tract obstruction, reversible moderate to severe mitral regurgitation, RV involvement, thrombus formation, and cardiac rupture, which are significant in the management, risk stratifica-tion, and follow-up of patients with TTC [70].
There are some data describing that real-time 3D echo-cardiography can be used to assess LV function in pa-tients with TTC. Measurements of LV volumes and EF obtained with the use of 3D echocardiography are com-parable to these obtained with the use of conventional 2D echocardiography and LV angiography. Not only 3D echocardiography is able to visualize and estimate LV vol-umes in the presence of changes of apical, midventricular or basal motion, but also with the use of this modality su-perior qualitative assessment of pathologic wall motion can be made [71–73]. Moreover, it can be the source of advanced quantitative analysis of the course of recovery of regional wall motion abnormalities in TTC [74]. Nev-ertheless, further studies are needed to confirm the role of real-time 3D echocardiography in clinical practice in patients with TTC [70].
CMR can be used as a second-line imaging modality in patients in whom TTC is suspected, but with poor echocardiographic windows, or when there is a need to confirm the presence of viable myocardium in the akinetic regions [75]. Similarly to TTE, CMR visualizes the morphologic and dynamic assessment of the heart.
Moreover, it is able to show myocardial inflammation, and with the use of gadolinium, it can detect scarring. CMR is able to classify different subtypes of TTC. It can detect features of TTC such as apical ballooning or me-dio-basal wall motion abnormalities (WMA), presence of wall edema (which is the result of inflammation) and LGE characteristics. They are all critical in the diagnosis and characterization of this pathology [76]. Some CMR findings may also be relevant in the differential diagno-sis: intense delayed subendocardial or transmural hyper-enhancement in acute MI, patchy hyperhyper-enhancement in myocarditis, and edema in TTC [75].
Myocarditis
Although echocardiography is a widely available and safe method, its findings are usually not sufficient for diag-nosing myocarditis. Echocardiography allows for detec-tion of increased wall thickness and hyperechogenicity, often accompanied by conduction disorders; however, these findings are not common in clinical practice [77]. More frequent echocardiographic findings in patients with acute myocarditis are: localized wall motion ab-normalities including areas of hypokinesia, akinesia, and dyskinesia. Still, these changes are not specific and cannot be used to differentiate acute MI from myocardi-tis [78]. Echocardiography may have prognostic value in patients in whom LV dysfunction is accompanied by RV dysfunction (the prognosis is less favorable) [77].
The suspicion of myocarditis is one of the most frequent indications for CMR. In CMR it is possible to detect
char-acteristic features of myocarditis: inflammatory hyperae-mia and edema, necrosis or scar, contractile dysfunction, and accompanying pericardial effusion. Hyperaemia, edema and necrosis are the criteria necessary to diagnose myocarditis. Two out of three criteria should be fulfilled to indicate active myocarditis. Moreover, the presence of necrosis or scarring are prognostic factors since they can predict functional and clinical recovery or death in patients with myocarditis. In many patients, performing CMR may be essential for making therapeutic decisions. Among available imaging techniques, CMR seems to be the most comprehensive and accurate diagnostic modal-ity when there is clinical suspicion of myocarditis. It can verify or exclude myocardial inflammation and revers-ible/irreversible injury and allows for assessment of the activity and severity of myocarditis. CMR may be signif-icant in verifying the suspicion of myocarditis in patients with ACS with normal coronary arteries or with atypical symptoms as well as in patients with persisting symp-toms and heart failure [77].
Cardiac tumours/masses
TTE is particularly helpful in detecting ventricular throm-bi, atrial myxomas, and thrombi that protrude into the atrial cavity. It is less reliable for discovery of small tu-mours, laminated thrombi or thrombi in the atrial ap-pendages. Most commonly, intracardiac mass is detected by echocardiography as concomitant finding in imaging ischemic heart disease or HCM [79]. It can be difficult to distinguish large, mobile thrombi from tumour masses. Then, the presence of coexisting LV wall motion
abnor-Table 5. Characteristic features of cardiomyopathies in echocardiography and CMR. Modified, based on [56].
Cardiomyopathy Echocardiography Cardiac magnetic resonance
HCM • increased interatrial septum thickness
• increased atrioventricular valve thickness • increased RV free wall thickness • mild to moderate pericardial effusion
• ground-glass appearance of ventricular myocardium • concentric LVH
• extreme concentric LVH
• global hypokinesia (with/without LV dilatation)
• posterolateral LGE + concentric LVH • diffuse subendocardial LGE
• intense myocardial ‘avidity’ for Gadolinium
DCM • LV non-compaction
• postero-lateral akinesia/dyskinesia
• mild (absent) dilatation + akinetic/dyskinetic seg-ments with non-coronary distribution
• short T2*
• patchy, midwall LGE
• akinesia/dyskinesia + LGE at the anterobasal septum or papillary muscles
• fatty replacement (T1w FS) within LV wall
ARVC • coexistent LV segmental dysfunction • fatty replacement (T1w FS) within LV wall
malities, global or regional, may be useful in differential diagnosis. Characteristic features of myxoma can be also helpful: it is a rarely calcified, usually solitary mass, most commonly localized in the left atrium, often attached to the heart wall by a stalk. The use of contrast in echocar-diography may be the source of relevant supportive evi-dence to the thrombotic nature of an intracardiac mass. Intracardiac masses can be also detected by echocardi-ography due to the coexisting infective endocarditis with vegetation formation. Vegetations are usually visualized as mobile, irregular masses attached to cardiac valves [79]. The indisputable advantage of echocardiography in di-agnosing cardiac tumours is the ability to evaluate dy-namic characteristic of intracardiac masses. It allows for assessment of both the anatomic extent and the physio-logic consequences of the mass. This plays an important role because although most of primary cardiac tumours are benign, they can have significant physiologic conse-quences due to compression or obstruction of the blood flow. The main limitation of echocardiography in imag-ing heart tumours is bone and lung interference, which makes it a suboptimal diagnostic method in patients with chronic obstructive pulmonary disease or narrow rib spaces. Visualizing vascularity of cardiac tumours by echocardiographic contrast perfusion imaging may be helpful in distinguishing malignant, highly vascular ones from benign tumours or thrombi. Three-dimensional echocardiography may be the source of additional infor-mation and may help to visualize the mass better [80]. Nevertheless, echocardiography may often provide only limited information concerning tumour extent and tissue
characterization. Moreover, primary heart tumours are less frequent than metastatic masses, leading to the ne-cessity of excluding tumour manifestations more distant from the heart [81].
In some cases, it can be difficult to visualize cardiac mass with the use of 2D echocardiography because of the vari-able site of attachment, shape and size. A series of 2D im-ages should be done and then the clinician should “men-tally” reconstruct the tumor to define all morphologic details. The cognitive reconstruction of image planes and geometric assumption about the shape of a mass are not needed when 3D echocardiography is performed. This can be particularly useful in evaluation of complex shapes of intracardiac tumours. Moreover, 3D images can be sliced in many different ways with the possibility to rotate data sets in space and obtain views that are impossible to achieve with the use of 2D echocardiography. In addition, 3D echocardiography gives more information about the tumour location and its shape as well as precisely de-scribes the relationship with ambient structures [15]. CMR is considered the gold standard technique for char-acterization of a suspected cardiac mass. It provides an unrestricted field of view, high temporal resolution and non-invasive tissue characterization. Thus, CMR is rel-evant in making the diagnosis, assessment of the func-tional impact of a lesion, management planning and post treatment follow-up. TTE, which is usually the first line method, often provides incomplete evaluation of the mass because of its limited field of view and limited soft tissue resolution. The additional advantage of CMR is the lack of exposure to ionizing radiation [82]. Due to its larger field of view, CMR can provide more diagnostic information by visualizing extracardiac components of a tumour, such as infiltration into the pericardium and extension into adjacent great vessels. Additionally, CMR is relevant in excluding hiatus hernia, tortous descending aorta or bronchogenic cyst, which can imitate cardiac tumours. CMR findings can be useful in management guiding and planning operation. Unlike two-dimensional echocardiography, CMR has the potential for tissue char-acterization by comparing the T1 and T2 values of the mass to a reference tissue. The signal intensity of the mass depends on the tissue composition. Tissue charac-terization by CMR allows us to differentiate myxomas, fibromas, thrombi, pericardial cysts and fatty tissue. Malignant tumours cannot be diagnosed precisely due
Table 6. Differentiation between cardiac tumour and
throm-bus in echocardiography imaging. Modified, based on [79, 80].
Tumour Thrombus
Wall motion
abnormalities +
-Calcification - (rarely) +
Quantity usually solitary mass multiple
Localization most commonly in the
left atrium
various
Attachment attached to the heart
wall by a stalk not attached to the heart wall
Vascularity malignant: +
-to the signal features. However, there are some features which should suggest the diagnosis of malignant tumor: inhomogeneous appearance of signal enhancement af-ter administration of gadolinium contrast, the infiltrative components of a tumour and haemorrhagic pericardial effusion [83].
Valvular heart disease (VHD)
Echocardiography plays a major role in confirming the diagnosis as well as assessing the severity and prognosis of VHD. It should be performed in every patient with a murmur, in whom there is a suspicion of valve disease after clinical evaluation. Flow-dependent indices includ-ing mean pressure gradient and maximal flow veloc-ity are useful in the evaluation of valve area in stenoses and have a great prognostic value. Valvular regurgitation can be assessed with the use of different indices such as quantitative measurements: vena contracta and effective regurgitant orifice area (ERO), which is superior to color Doppler jet size because of its smaller dependency on flow conditions.
Nevertheless, there are some limitations in all quantitative evaluations. They are highly sensitive to measurement er-rors and highly dependent on the operator. While evalu-ating the severity of VHD one should focus not only on echocardiographic measurements, but also on the anato-my, the mechanisms of VHD and the clinical assessment. A comprehensive evaluation of all valves with respect to associated valve diseases and the assessment of aorta should be included in every echocardiography study [84]. Valvular heart disease can be visualized also with the use of 3D echocardiography. This method is especially helpful in the evaluation of mitral valve. It enables us to demonstrate the geometry of mitral annulus and leaflet surface. It can explain the pathophysiology of mitral re-gurgitation as it can delineate the relationship between the mitral apparatus and papillary muscles. Moreover, it can accurately visualize both mitral leaflets, commis-sures and the valve orifice. The possibility to show the perpendicular en-face cut plane of the mitral valve or-ifice in 3D echocardiography is the greatest advantage of this modality, because it gives the opportunity to pre-cisely measure the mitral valve area. The measurements are the most accurate when done from the ventricular view. The low intraobserver and intraobserver variabili-ty are the important advantages of these measurements.
Mitral regurgitation in nonischemic and ischemic car-diomyopathies can be well characterized with the use of this modality. Three-dimensional echocardiogra-phy revealed the association between functional mitral regurgitation and annular dilatation, reduced cyclic variations in annular shape and area. It can also differ-entiate 2 types of mitral rings – Duran and Carpentier rings [85]. The use of this modality to assess mitral valve pathology should be performed in routine clinical prac-tice since images obtained with 3D echocardiography give the best physiologic and morphologic information regarding the mitral valve [23]. However, there is only limited use in visualization of aortic valve in 3D echo-cardiography, because aortic leaflets are thinner and often strongly calcified; as a result, many artifacts may occur. The delineation of aortic valve by 3D echocar-diography is constantly improved and this method can be used to diagnose bicuspid aortic valve, valvular veg-etations, prosthetic aortic valve leaks and subaortic pa-thology [85]. When it is available, 3D echocardiography should be incorporated into evaluation of aortic steno-sis and to explain the mechanism of aortic regurgitation [23]. This modality can also show some abnormalities of tricuspid valve such as tricuspid stenosis, cleft tricuspid valve and fail tricuspid leaflet [85]. For assessment of tricuspid and pulmonary valves disease 3D echocardio- graphy is not required in routine practice as there is no current evidence supporting this approach [23].
In patients with poor visibility or incomplete results due to e.g. large body mass, associated chest deformities or the lack of echo windows, CMR can be performed to evaluate the severity of valvular lesions – particularly the regurgitant ones, though with caution regarding spatial and temporal resolution [84, 86]. Then, it can potential-ly play a valuable role in the individual follow-up of the severity of regurgitant lesions and the assessment of the effects of these lesions on ventricular volumes and the myocardium. CMR is also important when there are con-flicting results of echocardiography and cardiac cathe-terization [31]. CMR is a highly recommended method in the assessment of RV function, volume and the con-sequences of tricuspid regurgitation. Practically, it is not performed as a routine imaging due to its limited availa-bility and reasons mentioned above [84].
There are no contraindications for CMR in patients with prosthetic valves. It is safe because heart valve
prosthe-ses have no substantial interactions with the magnetic field and heating is negligible. Nevertheless, valve pros-theses produce focal artifacts and signal loss due to dis-tortion of the magnetic field by the metal contained in them. These artifacts can obscure small jets of signal loss due to paravalvular leakage [31].
Congenital heart disease
Echocardiography is the first-line imaging investigation for pediatric patients, because of its numerous advan-tages: it is portable, non-invasive and provides immedi-ate, high-resolution anatomical and physiological infor-mation about the heart. For patients with good acoustic windows, echocardiography is sufficient to determine the diagnosis, management and prognosis.
There is also a possibility to use 3D echocardiography in order to diagnose and visualize congenital heart defects. It can be useful in imaging complex heart anatomy, al-though it is applied mainly in relatively simple congenital defects such as atrioventricular canals or ventricular sep-tal defects for sizing. Moreover, real-time 3D echocardi-ography can be used as a fast modality with no need to sedate pediatric and infant patients. Three-dimensional echocardiography allows for a display of intraventricular abnormalities, congenital heart valvular disease, aortic arch and vascular abnormalities. In patients with congen-ital heart disease the most important part of examination is the assessment of RV volume, opposite to adult pa-tients in whom 3D echocardiography is used mainly for quantification of LV volume and mass. Accurate evalua-tion of RV funcevalua-tion is important in surgical planning and assessing patient status after surgery [85].
Nevertheless, when the acoustic window is poor, there is often a need to use some additional investigation, par-ticularly for the visualization of extra-cardiac vascular structures. More often CMR is replacing cardiac cathe-terization to obtain hemodynamic information and vis-ualize great vessels. CMR gives anatomical and physio-logical information, which cannot be provided by echo-cardiography and catheterization alone. It plays a crucial role in visualization of extra-cardiac anatomy, including the great arteries, systemic and pulmonary veins, which can be depicted with high spatial resolution. Moreover, it enables us to assess vascular and valvular flows, quan-tify shunts and assess myocardial function precisely with high reproducibility, regardless of ventricular morpho-
logy. CMR provides high-resolution, isotropic, three- -dimensional data sets that make it superior to both catheterization and echocardiography. CMR allows for reconstruction of data in any imaging plane and com-plete visualization of complex cardiac anomalies, with no need to use ionizing radiation. CMR should be consid-ered in any pediatric patient in whom echocardiography does not give sufficient information for monitoring, de-cision-making or surgical planning [87]. However, small children usually require sedation and in critically ill in-fants monitoring is needed when performing CMR. This makes echocardiography superior to CMR in diagnosing small children, neonates and infants [31].
The inability to obtain complete diagnosis with TTE in many adults with congenital heart disease provided the incentive to evaluate the role of CMR as so-called second-line technique [86].
Both simple and complex congenital heart disease can be described by CMR in a very effective way due to three-dimensional contiguous data sets. An additional advantage of performing CMR in adult population is the lack of ionizing radiation, especially when the diagnostic procedures are performed in young adults. CMR is a first line-technique in adults, adolescents, older children and in patients after surgery regardless of age when echocar-diography procedures may be difficult to perform be-cause of the body habitus and interposition of scar tissue and lungs. The use of CMR before interventional proce-dures can reduce the need for them as well as the dura-tion and risks of diagnostic catheterizadura-tion. Using CMR for precise depiction of cardiac and great vessel anatomy may also decrease the duration and radiation dose asso-ciated with interventional procedures [31].
Anomalies of the viscero-atrial situs
Anomalies such as situs solitus, situs ambiguus, dextro-cardia and levodextro-cardia are usually easily identified by con-ventional diagnostic methods, such as echocardiography. Nevertheless, in some cases in which there are addition-al lesions, such as atrioventricular or ventriculoarteriaddition-al discordance, anomalous pulmonary or systemic venous connections, it may be difficult to define the topographic relations of the major cardiac segments. Data obtained by CMR imaging are easily related to the surrounding struc-tures, which makes the diagnosis reliable. CMR can give important information in patients with complex
anom-alies before catheterization, therefore it may be used as a primary imaging technique [31].
Anomalies of the atria and venous anomalies
Echocardiography is the first-line diagnostic method, which provides both diagnosis and quantification of atrial septal defects (ASD). The first finding indicating the presence of ASD may be RV volume overload, which is the best parameter to characterize the hemodynamic relevance of the defect. TTE is not sufficient to diagnose sinus venosus defects and to evaluate secundum defects, which can be more accurately detected by transesopha-geal echocardiography (TEE) [88].
CMR is relevant in identification of ASD. It allows for assessment of the shunt size favourably to some other techniques. Morphology of interatrial septal defects is visualized most precisely by TEE. In infants, TTE is a pri-mary method; however, by using this method it is diffi-cult to evaluate anomalous pulmonary venous return. That leads to the use of CMR in infants as a second-line technique.
CMR is the best non-invasive method to assess anato-my of pulmonary veins. It surpasses both echocardio- graphy or X-ray angiocardiography, because they can-not depict such a complete image of pulmonary veins. CMR is particularly useful in identifying partial anoma-lous venous return in patients with ASD and in identify-ing partial anomalous pulmonary venous connection in patients with enlarged, hypertrophic or failing RV. CMR plays a major role in visualizing pulmonary venous sten-oses or occlusions after operation or after ablation. It can demonstrate stenoses of intraatrial baffles after repair of transposition of great arteries and identify systemic ve-nous anomalies (bilateral superior cava, interrupted infe-rior cava) [31].
Anomalies of the atrioventricular connections
CMR can demonstrate discordant and crisscross atri-oventricular connections because it can precisely de-fine morphology of atrias and ventricules. The first-line method to visualize double inlet ventricle, straddling atri-oventricular valve, tricuspid atresia, and mitral atresia is echocardiography; however, CMR surpasses echocardi-ography in evaluating ventricular volumes which can be decisive in guiding management [31].
Anomalies of the ventricles – ventricular septal defect (VSD)
Echocardiography is the most suitable, non-invasive imaging modality in the diagnosis and the evaluation of the disease severity. It is relevant in providing informa-tion about the locainforma-tion, number, and the size of defects [88]. TTE is performed to assess hemodynamic impact of VSD, show elevated pulmonary artery pressure, ob-struction localized in RV outflow tract, insufficient aortic valve and deformation of the valve apparatus. TEE may be helpful when the quality of images obtained by TTE is not reliable. Three-dimensional echocardiography is used to quantify shunt and when it is difficult to depict defect by two-dimensional echocardiography [89]. CMR is a highly specific technique for the quantification and detection of VSD. It can be particularly useful in giv-ing additional information about shunt volume, when the diagnosis is already established by echocardiography. This kind of information may be relevant before making the decision about surgery. CMR is crucial in visualizing ven-tricular anatomy in complex anomalies such as tetralogy of Fallot, pulmonary atresia, tricuspid atresia, and univen-tricular hearts. In double outlet ventricles CMR can de-scribe the location of VSD in relation to great vessels [31].
Anomalies of the great arteries and conduits
Echocardiography with Doppler allows for diagnosis and estimation of the hemodynamic severity of coarctation of the aorta in infants. However, in older children and adults it is favorable to reach the diagnosis based on CMR im-aging [31]. CMR is an effective and non-invasive method for evaluating morphology of coarctation of the aorta. It is superior to echocardiography because it accurately de-picts both the location and the degree of narrowing, the collateral circulation as well as the shape and size of the ascending aorta. Nonetheless, this morphological infor-mation does not necessarily indicate the hemodynamic consequences of the narrowing. The use of velocity map-ping can provide evaluation of hemodynamic severity of the coarctation. Information about the pressure gradient across the coarctation and the volume of collateral flow is important for planning surgery [90]. This imaging mo-dality plays an important role in the evaluation of sinus of Valsalva aneurysm, aortic dilatation, aneurysm associ-ated with Marfan and Ehlers-Danlos syndromes. It may also be used to monitor aortic dimensions over time in general. It is the first-line method in diagnosing vascular rings. Patent ductus arteriosus in infants is depicted with
