Echocardiographic recognition of cardiomyopathies

INTRODUCTION — Cardiomyopathy is defined as a disease of heart muscle. Cardiomyopathies include a variety of myocardial disorders that manifest with various structural and functional phenotypes with familial and nonfamilial types. This topic will review the echocardiographic features of the various types of cardiomyopathy. The general evaluation of the patient with heart failure or cardiomyopathy is discussed separately. (See "Determining the etiology and severity of heart failure or cardiomyopathy".)

CLASSIFICATION — The classification of cardiomyopathies is reviewed separately. In summary, morphological and functional attributes have been described by the 2006 American Heart Association and 2008 European Society of Cardiology classification systems (table 1A-B) [1,2]. Heart disease secondary to coronary artery, valvular, or congenital heart disease is excluded from the cardiomyopathy classification. However, in clinical practice, the terms "ischemic," "valvular," and "hypertensive cardiomyopathy" have been used commonly. There are five types of cardiomyopathy that are each recognized by echocardiography [1,2]. In the MOGE(S) classification endorsed by the World Heart Federation, cardiomyopathy is categorized by the following characteristics: morphofunctional (M), organ involvement (O), genetic or familial inheritance (G), etiological annotation (E), and stage (S) [3]. (See "Definition and classification of the cardiomyopathies".)

The five types of morphofunctional cardiomyopathy are as follows (table 1A-B) [2]:

●Dilated cardiomyopathy arising as primary myocardial disease of unknown etiology or as disorders of toxic, familial, or infective origin. In clinical practice, ischemic cardiomyopathy is frequently viewed as a type of dilated cardiomyopathy, although current major society classification systems exclude it [1,2]. (See "Causes of dilated cardiomyopathy" and "Familial dilated cardiomyopathy: Prevalence, diagnosis and treatment".)

●Hypertrophic cardiomyopathy, including various causes of increased left ventricular (LV) wall thickness not caused by hypertension or valve disease (see "Hypertrophic cardiomyopathy: Clinical manifestations, diagnosis, and evaluation"). Restrictive cardiomyopathy, including cardiac amyloidosis and endomyocardial fibrosis. (See "Restrictive cardiomyopathies" and "Endomyocardial fibrosis" and "Cardiac amyloidosis: Epidemiology, clinical manifestations, and diagnosis".)

●Arrhythmogenic right ventricular cardiomyopathy. (See "Arrhythmogenic right ventricular cardiomyopathy: Anatomy, histology, and clinical manifestations".)

●Restrictive cardiomyopathy. (See "Restrictive cardiomyopathies".)

●Unclassified cardiomyopathy, including ventricular noncompaction and stress cardiomyopathy. (See "Isolated left ventricular noncompaction in adults: Clinical manifestations and diagnosis" and "Clinical manifestations and diagnosis of stress (takotsubo) cardiomyopathy".)

Cardiomyopathies should be differentiated from exercise-induced cardiac remodeling (EICR), or so-called athlete’s heart. EICR may be characterized by mild and symmetric wall thickening associated with cavity dilatation, and with high mitral inflow E velocities [4]. Right ventricular enlargement has been observed in Olympic athletes, meeting a criterion for ARVC in 32 percent, and caution must be utilized not to classify these individuals as abnormal. Left atrial enlargement may also occur with EICR [5]. Doppler tissue imaging and speckle tracking show promise in identifying normal function in EICR [4]. (See "Hypertrophic cardiomyopathy: Clinical manifestations, diagnosis, and evaluation", section on 'Athlete's heart'.)

As noted above, ischemic heart disease is not considered a type of cardiomyopathy in formal classification systems, although the term "ischemic cardiomyopathy" is commonly used clinically to describe significantly impaired LV function that results from coronary artery disease. Wall motion abnormalities may be due to previous myocardial infarction and/or associated with multivessel coronary artery disease. In both ischemic and idiopathic forms, LV wall motion abnormalities and the intensity of scarring can be segmentally variable or heterogeneous. Ischemic cardiomyopathy is often associated with regional remodeling, which is characterized by local segments that have their own radius of curvature. Ischemic cardiomyopathy also tends to have areas of endocardial brightening or scarring in infarcted areas.

Diagnosis of ischemic cardiomyopathy is discussed separately. (See "Determining the etiology and severity of heart failure or cardiomyopathy" and "Evaluation of hibernating myocardium" and "Clinical syndromes of stunned or hibernating myocardium".)

CONDITIONS ASSOCIATED WITH REGIONAL WALL MOTION ABNORMALITIES — Regional wall motion abnormalities are commonly associated with ischemic heart disease but may also be seen with a variety of other conditions including sarcoidosis, arrhythmogenic RV cardiomyopathy (which may also involve the LV), stress cardiomyopathy, Chagas disease, and tuberculosis, as well as in some cases of dilated cardiomyopathy. (See "Clinical manifestations and diagnosis of cardiac sarcoidosis" and "Arrhythmogenic right ventricular cardiomyopathy: Anatomy, histology, and clinical manifestations" and "Management and prognosis of stress (takotsubo) cardiomyopathy" and "Chronic Chagas cardiomyopathy: Clinical manifestations and diagnosis" and "Tuberculous pericarditis", section on 'Myopericarditis'.)

Chronic Chagas cardiomyopathy is discussed separately. In relatively early stages of cardiac involvement, diastolic dysfunction due to fibrotic myocardium and segmental wall motion abnormalities may be seen, most commonly at the apex and inferior to inferolateral walls. LV apical aneurysm has been described as the hallmark lesion in Chagas heart disease, which helps differentiate it from other cardiomyopathies [6]. More advanced disease is characterized by global ventricular dilation, diffuse hypokinesis, and longitudinal strain abnormalities. (See "Chronic Chagas cardiomyopathy: Clinical manifestations and diagnosis".)

DILATED CARDIOMYOPATHY — Dilated cardiomyopathy (DCM) is characterized by dilatation and impaired contraction of one or both ventricles [7]. DCM is readily identified by echocardiography when it is fully developed but is more difficult to detect in its early stages. Without the clinical history, patient examination, and other diagnostic test results, echocardiography alone is often unable to establish the cause of myocardial disease. Causes of dilated cardiomyopathy are discussed separately. (See "Causes of dilated cardiomyopathy".)

Echocardiographic findings — The most distinctive two-dimensional (2D) echocardiographic findings in a DCM are LV spherical dilatation, normal or reduced wall thickness, poor systolic wall thickening, and/or reduced inward endocardial systolic motion (figure 1 and image 1A-D). All of the systolic indices are reduced, including LV fractional shortening, fractional area change, and ejection fraction (movie 1A-C). Four chamber cardiac enlargement is often present (image 1B-D).

On M-mode echocardiography, additional features related to systolic dysfunction are increased separation of the mitral leaflet E point from the septum, poor mitral valve opening, poor aortic valve opening and early closure from a reduced stroke volume, and poor systolic aortic root motion (figure 1 and image 1D-G) [8]. M-mode echocardiography offers valuable information due to its fast frame rate, especially when 2D images are suboptimal.

A 2D image of a normal heart in a young athlete with a slow heart rate may qualitatively suggest DCM. However, the M-mode will be normal and not display any of the above features.

Left ventricular volume — Based on the American Society of Echocardiography guidelines, quantitative measurements should be obtained for accurate evaluation of cardiac chamber sizes. While linear (M-mode) measurements are useful, they may not reflect true cardiac dimensions, especially in distorted ventricles. For this reason, linear derived volumetric measurements are no longer recommended [9]. In patients with DCM, the LV end-diastolic volume index often exceeds 100 mL/m² (upper normal is 74 mL/m² in men and 61 mL/m² in women) [9,10]. The LV ejection fraction (LVEF), derived from the end-systolic volume (ESV) and end-diastolic volume (EDV) determinations can, at times, fall below 20 percent, but is usually between 20 and 40 percent (normal ≥52 percent in men and ≥54 percent in women) (image 2 and figure 2A-B) [9].

Despite the reduced LVEF, cardiac output calculations (stroke volume times heart rate) are frequently normal. There are two reasons for this finding. First, patients with cardiomyopathy frequently have elevated heart rates. Second, since the stroke volume is equal to the product of the LV end-diastolic volume and ejection fraction, the effect of a low ejection fraction can be counterbalanced by an elevation in end-diastolic volume. As an example, a patient with an end-diastolic volume of 200 mL, an ejection fraction of 30 percent, and a heart rate of 100 beats per minute has a cardiac output of 6 L/min. In large hearts, accurate measurement of volume and their reproducibility are enhanced by using a microbubble contrast agent to improve detection of the boundary between the myocardium and blood pool.

We routinely measure the LV end-systolic volume index (ESVI) because it provides important information in several clinical settings.

●An ESVI that rises progressively from normal (<31 mL/m² in men and <24 mL/m² in women is an important clinical indicator of deteriorated global function [11].

●In patients with ischemic cardiomyopathy who have global dysfunction with segmental evidence of infarction, an ESVI of 45 mL/m² identifies patients with a poor outcome [12].

●In the later Heart and Soul study, the risk of an adverse outcome began to increase sharply once the end systolic volume exceeded 25 mL/m² [11].

Strain echocardiography — Global longitudinal strain (GLS) is a sensitive measure of LV contractility and is an independent predictor of all-cause mortality in patients with systolic heart failure [13]. In cardiomyopathy patients with recovered LVEF, abnormal GLS predicts recurrent reduced LVEF [14]. GLS is used clinically to detect changes in LV function, which may become apparent independent of LVEF. The role of strain imaging in assessing cardiotoxicity with anthracyclines is discussed separately. (See "Tissue Doppler echocardiography", section on 'Strain and strain rate imaging' and "Risk and prevention of anthracycline cardiotoxicity", section on 'Left ventricular function assessment'.)

Right ventricle — Involvement of the right heart has important implications, with right ventricular (RV) failure most commonly caused by pulmonary hypertension and/or a pathologic process involving the RV myocardium. The prognosis is considerably worsened when there is RV dilatation and/or a reduced RV ejection fraction [15,16]. A useful and easily obtained measurement of RV function is the tricuspid annular plane systolic excursion, also called tricuspid annulus plane systolic excursion, an expression of longitudinal muscle function or descent of the RV cardiac base. In one report, an excursion ≤14 mm added significant prognostic information to other clinical and echocardiographic findings in DCM [17]. (See "Predictors of survival in heart failure with reduced ejection fraction", section on 'Right ventricular function'.)

Gradients of tricuspid regurgitation and end diastolic pulmonary regurgitation correlate with pulmonary artery systolic and diastolic pressures, and have been shown to predict heart failure hospitalization and mortality in patients with coronary artery disease [18].

Left atrium — The left atrial end-systolic volume index may be increased and often exceeds 50 mL/m² (upper limits of normal approximately 34 mL/m²) [9]. Data suggest that minimal atrial volume (at ventricular end-diastole) may be more predictive of outcomes than maximal left atrial volume (at ventricular end-systole) [19]. Left atrial volume estimates from biplane 2D measurements are more accurate than single linear dimensions for measuring left atrial size [20].

Doppler echocardiography — Doppler has been used in DCM to measure decreased stroke volume. The velocity time integral of the LV outflow tract is decreased (<18 cm) in this disorder (image 3) [21]. In addition, acceleration or deceleration of the mitral regurgitant jet can be used as an analog of dP/dT (ie, the change in LV pressure over time) [22]. As an example, one study of 61 patients found that dP/dT <600 mmHg/second and -dP/dT <450 mmHg/second identified a high risk group with a reduced event-free survival [23].

Mitral regurgitation is a constant feature of DCM and is usually mild to moderate in severity but, on occasion, may be severe. The pathophysiology of mitral regurgitation in DCM is usually not due to organic leaflet disease but rather due to abnormal leaflet tethering mandated by the change in LV shape from ellipsoid to spherical. As cardiomyopathy progresses, the point of leaflet coaptation migrates from its normal basal location to a spot deeper in the LV cavity. (See "Echocardiographic evaluation of the mitral valve".)

Evaluation of mitral inflow patterns can identify patients with restrictive physiology due to diastolic dysfunction (waveform 1 and figure 3) [24] (see "Echocardiographic evaluation of left ventricular diastolic function in adults"). Restrictive or pseudonormal diastolic inflow patterns connote a poor prognosis and aid in guiding treatment [25-29]. Patients with DCM have abnormally low diastolic suction and blunted capacity to recruit suction [30].

The pulmonary vein flow signal should always be sought as an adjunct to the mitral inflow pattern. Abnormal pulmonary venous systolic flow patterns have been shown to correlate with future development of pulmonary hypertension [31]. Loss of the systolic dominant flow pattern suggests elevated filling pressure. Pulmonary venous flow reversal duration minus mitral inflow duration at atrial contraction >30 ms predicts mortality and hospitalization [32]. Similarly, Doppler tissue imaging has patterns associated with elevated LV filling pressures. (See "Predictors of survival in heart failure with reduced ejection fraction", section on 'Concomitant diastolic dysfunction'.)

Features of specific types of dilated cardiomyopathy — Although echocardiography cannot distinguish the specific cause of DCM, certain types of disease processes have characteristic echocardiographic features. Dilated LVs may occur after chemotherapy; peri-partum; or may be tachycardia-mediated, premature ventricular complex/contraction-mediated (premature ventricular complex/contraction [PVC; also referred to a premature ventricular beats or premature ventricular depolarizations]; generally >20,000 PVCs in 24 hours or >10 percent of recorded beats on Holter monitor), pacing-induced [33], thyrotoxic, or muscular dystrophy-associated cardiomyopathy, among other causes. (See "Causes of dilated cardiomyopathy".)

HYPERTROPHIC CARDIOMYOPATHY — Hypertrophic cardiomyopathy (HCM) is a genetically determined heart muscle disease characterized by LV hypertrophy of various morphologies. Diagnosis of HCM, including echocardiographic features, is discussed separately. (See "Hypertrophic cardiomyopathy: Clinical manifestations, diagnosis, and evaluation" and "Hypertrophic cardiomyopathy: Morphologic variants and the pathophysiology of left ventricular outflow tract obstruction".)

RESTRICTIVE CARDIOMYOPATHY — Restrictive cardiomyopathy is characterized by a nondilated (or small, end-diastolic volume index <40 mL/m²) LV with abnormal ventricular diastolic function [34] (see "Echocardiographic evaluation of left ventricular diastolic function in adults", section on 'Diagnosis of diastolic dysfunction'). Hypertrophy is typically absent, although infiltrative disease (such as amyloidosis) and lysosomal diseases (such as Fabry disease) [35] may cause an increase in LV wall thickness. Systolic function usually remains normal, at least early in the disease. This entity is a subset of what has been referred to as heart failure with preserved ejection fraction (HFpEF) [36]. Causes of restrictive cardiomyopathy include infiltrative disease, storage disease, and endomyocardial processes [37]. (See "Definition and classification of the cardiomyopathies", section on 'Restrictive cardiomyopathy'.)

Restrictive cardiomyopathies are more difficult to diagnose with echocardiography than dilated or hypertrophic cardiomyopathies, and may be challenging to distinguish from constrictive pericarditis. (See "Restrictive cardiomyopathies".)

Echocardiography, including Doppler interrogation, is the most effective noninvasive means for the recognition of this group of conditions. Restrictive cardiomyopathy is characterized by a low or normal diastolic volume, normal or only mildly reduced LV ejection fraction, atrial enlargement, normal pericardium, and abnormal diastolic function. Diastolic dysfunction is frequently restrictive, with an elevated peak mitral inflow velocity, rapid early mitral inflow deceleration, and reduced Doppler tissue imaging early annular velocity. (See "Differentiating constrictive pericarditis and restrictive cardiomyopathy".)

Echocardiographic findings may help differentiate between restrictive cardiomyopathy and pericardial constriction among individuals with HF symptoms and normal LV ejection fraction. (See "Differentiating constrictive pericarditis and restrictive cardiomyopathy".)

Diabetes mellitus — Perhaps the most common restrictive cardiomyopathy is the small, stiff heart of diabetes in which diastolic dysfunction is the predominant functional abnormality [38]. In the majority of diabetics, this condition is clinically unapparent [39,40]. Quantitation of LV function reveals a normal ejection fraction and LV volumes that are lower than expected. This condition is suspected as a predisposing factor when, for example, diabetics with critical coronary artery stenosis and normal LV systolic function develop pulmonary congestion in association with angina or acute myocardial infarction. (See "Heart failure in patients with diabetes mellitus: Epidemiology, pathophysiology, and management".)

Amyloid cardiomyopathy — Amyloid cardiomyopathy can present as a restrictive cardiomyopathy with increased wall thickness that may be confused with hypertrophic cardiomyopathy (HCM). The clinical manifestations and diagnosis of cardiac amyloidosis are discussed separately. (See "Cardiac amyloidosis: Epidemiology, clinical manifestations, and diagnosis".)

Diastolic dysfunction is the most common, earliest, and most important echocardiographic abnormality in cardiac amyloidosis [41].

Echocardiography in patients with overt cardiac amyloidosis frequently demonstrates symmetric LV wall thickening, typically involving the interventricular septum, small ventricular chambers, thickening of the atrial septum, pericardial effusion, and dilated atria (image 4A-B and movie 2A-C) [41,42]. Increased right ventricular (RV) wall thickness, when present, may be associated with RV diastolic dysfunction, which can be demonstrated by Doppler examination [42]. Disproportionate RV enlargement may also occur [43].

Another common echocardiographic finding in cardiac amyloidosis is a granular, "speckled" appearance of the myocardium, resulting from the presence of amyloid and collagen nodules in the heart (movie 2A) [41,44-46]. This finding alone is relatively nonspecific [47] but the combination of these refractile echoes, atrial septum thickening, and low ECG voltage are highly suggestive of cardiac amyloid [44].

Apparent preservation or exaggeration of contractile function in a subgroup of patients with amyloid cardiomyopathy is explained by very low wall stress, which is the ultimate expression of afterload and is greatly reduced by the combination of thickened walls, very small cavity, and low generated systolic pressure (arterial hypotension). When contractile function is preserved, amyloid cardiomyopathy can be mistaken for HCM, and diagnosis can be delayed. A patient with low blood pressure, low ECG voltage, valvular thickening, pericardial and pleural effusions, and the above features should immediately arouse suspicion of the advanced stage of this form of infiltrative cardiomyopathy. Early disease may be difficult to differentiate from other forms of cardiac disease and may only be manifest upon serial echocardiograms.

Strain echocardiography may be helpful in diagnosing amyloid cardiomyopathy. A systolic septal longitudinal base-to-apex strain ratio >2.1 has an 88 percent sensitivity and 85 percent specificity in differentiating amyloid cardiomyopathy from other causes of LV hypertrophy [48]. Polar maps (so-called "bull's-eye" maps or apical sparing pattern) facilitate recognition of this unique pattern (image 5). Relative regional strain ratio with apical sparing has both diagnostic and prognostic implications in patients with cardiac amyloidosis [49].

Endomyocardial fibrosis — Endomyocardial fibrosis is a cause of restrictive cardiomyopathy in North Africa and South America. The condition is associated with eosinophilia in approximately 50 percent of those afflicted, and may overlap with eosinophilic endocarditis also known as Loeffler's or Davies disease when encountered in North Africa.

The recognition of endomyocardial fibrosis depends on a high level of clinical suspicion and characteristic echocardiographic appearance [50,51]. There are mass-like apical lesions in the LV, resulting from a thrombotic fibrocalcific process. These lesions are associated with restriction of LV and RV filling due to obliteration of one or both cardiac apices (image 6). Mitral and tricuspid valve leaflet tethering may occur, resulting in regurgitation. In addition to the unique appearance of the apices, the atria are strikingly enlarged. As the condition progresses, more and more of the LV cavity is obliterated, leading to a progressively restrictive physiology (image 7). (See "Endomyocardial fibrosis".)

Endomyocardial fibrosis can be differentiated from apical HCM by left-sided echo contrast, which demonstrates obliteration of the apical cavity in the former and apical hypertrophy in the latter.

ARRHYTHMOGENIC RIGHT VENTRICULAR CARDIOMYOPATHY — Arrhythmogenic right ventricular cardiomyopathy (ARVC), also known as arrhythmogenic right ventricular dysplasia, is a category of cardiomyopathy characterized by fibrous or fibro-fatty replacement of myocardium in the inflow tract, outflow tract, and/or apex of the RV (table 1A-B). Echocardiography is one of several modalities utilized to aid in the diagnosis of ARVC as discussed separately. (See "Arrhythmogenic right ventricular cardiomyopathy: Diagnostic evaluation and diagnosis", section on 'Echocardiography'.)

UNCLASSIFIED CARDIOMYOPATHY — LV noncompaction and stress (takotsubo) cardiomyopathy lie in this category.

Stress cardiomyopathy is an often reversible form of cardiomyopathy that may present with slight troponin elevation and electrocardiogram abnormalities. Apical ballooning and/or midventricular hypokinesis is usually seen. (See "Clinical manifestations and diagnosis of stress (takotsubo) cardiomyopathy".)

Isolated LV noncompaction is a cardiomyopathy characterized by prominent trabeculae and deep intertrabecular recesses, with a noncompacted to compacted myocardial ratio of at least 2:1. LV morphologic criteria for noncompaction should be applied with caution since the specificity of imaging criteria may be low in some populations such as athletes. Left-sided contrast with a proper mechanical index can be used to delineate the endocardial border and improve the diagnosis of LV noncompaction [52]. (See "Isolated left ventricular noncompaction in adults: Clinical manifestations and diagnosis".)

SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Cardiomyopathy".)

SUMMARY AND RECOMMENDATIONS

●Echocardiography is the primary diagnostic modality for identification and differentiation of the various types of cardiomyopathy (table 1A-B). (See 'Introduction' above.)

●The five types of cardiomyopathy are dilated cardiomyopathy (DCM), hypertrophic cardiomyopathy (HCM), restrictive cardiomyopathy, arrhythmogenic right ventricular cardiomyopathy, and unclassified cardiomyopathy. (See 'Introduction' above and "Definition and classification of the cardiomyopathies", section on 'Definition and classification'.)

●The most distinctive 2D echocardiographic findings in a DCM are left ventricular (LV) spherical dilatation, normal or reduced wall thickness, poor systolic wall thickening, and/or reduced inward endocardial systolic motion (figure 1 and image 1A-D). (See 'Dilated cardiomyopathy' above.)

●Restrictive cardiomyopathy is characterized by nondilated ventricles with abnormal diastolic function. Hypertrophy is typically absent, although infiltrative disease (such as amyloidosis) and storage disease (such as Fabry disease) may cause an increase in LV wall thickness. (See 'Restrictive cardiomyopathy' above and "Definition and classification of the cardiomyopathies", section on 'Restrictive cardiomyopathy'.)