Cardiomyopathies, once defined as “heart muscle diseases of unknown cause,” are now classified by their dominant pathophysiology or pathogenetic factors. These classifications include dilated cardiomyopathy, hypertrophic cardiomyopathy, restrictive cardiomyopathy, arrhythmogenic right ventricular cardiomyopathy, and unclassified cardiomyopathies (Table 33.1) (1). Some diseases may present with features of more than one type of cardiomyopathy.

Specific cardiomyopathies describe heart muscle diseases that are associated with cardiac or systemic disorders (1). Ischemic cardiomyopathy for example presents as a dilated cardiomyopathy with impaired contractile performance not explained by the extent of coronary artery disease or ischemic damage. Valvular cardiomyopathy presents with ventricular dysfunction that is out of proportion to the abnormal loading conditions. Hypertensive cardiomyopathy often presents with left ventricular hypertrophy in association with features of dilated or restrictive cardiomyopathy with cardiac failure. Inflammatory cardiomyopathy is defined by myocarditis (diagnosed by established histological, immunological, and immunohistochemical criteria) in association with cardiac dysfunction. Inflammatory myocardial disease may be idiopathic, autoimmune, or infectious, and is involved in the pathogenesis of dilated cardiomyopathy and other cardiomyopathies. Metabolic cardiomyopathy may be caused by a wide variety of etiologies, including endocrine disorders, familial storage diseases, and/or infiltrations, deficiency syndromes, and amyloid diseases, among others. Cardiomyopathy may also be caused by general system disease, muscular dystrophies, and/or neuromuscular disorders. Sensitivity and toxic reactions may also induce cardiomyopathy and include reactions to alcohol and catecholamines, among others. Finally, peripartal cardiomyopathy may first manifest in the peripartum period.

Dilated cardiomyopathy is characterized by dilation and impaired contraction of the left ventricle or both ventricles (2). It may be idiopathic, familial/genetic, viral and/or immune, alcoholic/toxic, or associated with recognized cardiovascular disease in which the degree of myocardial dysfunction is not explained by the abnormal loading conditions or the extent of ischemic damage. Myocardial histology
is nonspecific. All patients with dilated cardiomyopathy should have their immediate family members screened for the disease because of the high incidence of familial dilated cardiomyopathy (3). Goerss and associates revealed that at least 24% of patients with dilated cardiomyopathy have familial disease and that there appears to be no demonstrable differences in clinical or pathological findings between familial and nonfamilial disease, other than confirmed family history (3). Clinical presentation is usually with heart failure, which is often progressive. Arrhythmias, thromboembolism, and sudden death are common and may occur at any stage. End-diastolic and end-systolic dimensions and volumes are typically increased and all variables of systolic function, such as ejection fraction, stroke volume, and cardiac output are uniformly decreased (Fig. 33.1) (2). While left ventricular mass is uniformly increased, wall thickness varies among patients and typically is within normal limits. Ventricular contractility is usually globally reduced, yet superimposed regional wall motion abnormalities can also be present if substantial coronary artery disease exists. These similar findings occur despite the wide variety of etiologies of dilated cardiomyopathy. Other two-dimensional echocardiographic features of dilated cardiomyopathy include dilation of the mitral valve annulus, leading to incomplete coaption of the anterior and posterior leaflets, causing functional mitral insufficiency, enlarged left and/or right atrial chambers, and apical ventricular thrombi (Fig. 33.2).

Patients with dilated cardiomyopathy exhibit global systolic dysfunction, with some patients having only mild symptoms whereas others exhibit signs of chronic heart failure. Doppler and color-flow imaging provides important hemodynamic information (ejection fraction, fraction area change, stroke volume, cardiac output, and ventricular filling pressures) that can assess management strategy. Intracardiac pressures (intraatrial, intraventricular, and pulmonary artery) can be assessed with the Bernoulli equation. All four phases of diastole can be assessed by using pulsed wave Doppler interrogation of mitral flow velocity between the valve leaflet tips (Fig. 33.3). Based on the Doppler velocity patterns, diastolic filling abnormalities can be classified into three broad categories. Abnormal relaxation (decreased E/A ratio) is present with decreased preload, myocardial ischemia, and/or the normal effects of aging. Restrictive physiology (increased E/A ratio) is present with left ventricular failure (decreased compliance) and/or volume overload. Pseudonormalization (normal E/A ratio) represents a transition period when diastolic dysfunction (both abnormal relaxation and restrictive physiology coexist) is present yet the E/A ratio is normal. If a patient is suspected of having diastolic dysfunction yet the E/A ratio is normal, one must assess pulmonary venous flow patterns. If true diastolic dysfunction is present, abnormalities of pulmonary venous flow will also be present. If diastolic function is normal, pulmonary venous flow will be normal as well. While analysis of the mitral inflow velocity curve provides useful information regarding diastolic function, mitral inflow is dependent on multiple interrelated factors. To overcome these limitations, other Doppler parameters have been used to assess diastolic function, including pulmonary venous velocity curves, color M-mode, and the response of the mitral inflow to altered loading conditions. Perhaps the most promising of these new techniques of assessing diastolic function is tissue Doppler imaging of mitral annular motion, which has been proposed to correct for the influence of myocardial relaxation on transmitral flows (4 ).

Patients with dilated cardiomyopathy who are clinically compensated demonstrate a relatively normal stroke volume and cardiac output and an abnormal relaxation
(decreased E/A ratio) inflow profile. When patients begin to decompensate, stroke volume and cardiac output decrease and a restrictive physiology (increased E/A ratio) inflow profile predominates because of decreased left ventricular compliance and increased left ventricular filling pressures (5). St. Goar and associates evaluated patients with idiopathic-dilated cardiomyopathy and severe heart failure who were undergoing cardiac catheterization during evaluation for heart transplantation (5). Simultaneous echocardiographic evaluation revealed that the transmitral flow velocity pattern was characterized by normal peak early filling velocity, low normal isovolumic relaxation time, shortened acceleration and deceleration times of early diastolic flow, decreased early flow velocity integral, and absent or decreased filling during atrial contraction (5). This pattern reflects interaction between elevated transmitral driving pressure and the compromised relaxation and compliance of a left ventricle, functioning on an elevated pressure-volume curve (5). The evolution of diastolic dysfunction from abnormal relaxation to restrictive physiology has been reliably reproduced in animal models of dilated cardiomyopathy (6). Ohno and associates measured left ventricular and left atrial pressures and left ventricular volume, and calculated left ventricular and left atrial stiffness during the development of congestive heart failure produced by rapid pacing in awake, unsedated dogs (6). They revealed that early in congestive heart failure, slowing left ventricular relaxation reduced the maximal early diastolic left atrial-left ventricular pressure gradient, decreasing the peak early filling rate (6). As congestive heart failure progressed, this was overcome by an increase in left atrial pressure that augmented the early diastolic left atrial-left ventricular pressure gradient, increasing peak early filling rate (6). Increasing left ventricular stiffness during the development of congestive heart failure progressively shortened the early filling deceleration time and augmented the early filling deceleration rate (6). These observations suggest that the early filling deceleration time reflects left ventricular stiffness (6). Clinical studies indicate that, of the wide variety of variables derived from mitral inflow velocity profile, deceleration time has the most prognostic value because shorter deceleration time (restrictive physiology) portends a worse prognosis (7,8). Rihal and associates examined the clinical and echocardiographic characteristics of patients with the clinical diagnosis of dilated cardiomyopathy to determine the prognostic implications of these characteristics (7). Patients with severe congestive heart failure had lower indices of systolic function and were more likely to have significant mitral regurgitation and greater left atrial and right ventricular dilation (7). Left ventricular diastolic filling abnormalities were prominent and independently associated with severe symptoms, with a restrictive-type filling pattern (increased E/A ratio, short deceleration time) being common (7). Xie and associates confirmed that patients with congestive heart failure with poor prognosis can be identified by a restrictive transmitral flow pattern, female gender, and advanced functional class (8). Of these, the restrictive transmitral flow pattern appears to be the single best predictor of mortality over two years (8). In patients with dilated cardiomyopathy, the deceleration time increases, and the mitral inflow velocity profile becomes less characteristic of restrictive physiology as congestive heart failure symptoms are treated with medication. Improvement in these indices of diastolic dysfunction is associated with a high probability of clinical improvement and survival (9,10). Pinamonti and associates evaluated patients with dilated cardiomyopathy at presentation and after three months of medical treatment (9). They found that persistence of restrictive filling at three months was associated with a high mortality and transplantation rate, whereas patients with reversible restrictive filling had a high probability of clinical improvement and excellent survival (9). Similarly, a retrospective analysis by Lee and associates revealed that, in patients with congestive heart failure, the initial restrictive diastolic filling pattern can be altered to a nonrestrictive filling pattern with medical therapy and a change in diastolic filling to a nonrestrictive pattern is associated with improved survival (10). Another useful prognostic indicator in patients with dilated cardiomyopathy is the status of pulmonary artery pressure as estimated from tricuspid regurgitation velocity (11). Abramson and associates evaluated patients with dilated cardiomyopathy and found that patients exhibiting a high velocity of tricuspid regurgitation (> 2.5 meters/second) had more hospitalizations for congestive heart failure and a higher mortality rate when compared to patients exhibiting a lower velocity of tricuspid regurgitation (< 2.5 meters/second) (11). Peak velocity of tricuspid regurgitation was the only prognostic variable that predicted overall mortality, mortality due to myocardial failure, and hospitalization for congestive heart failure (11). Higher tricuspid regurgitation velocities are usually seen in patients with dilated cardiomyopathy and a restrictive physiology mitral inflow velocity profile. The presence of a restrictive physiology mitral inflow velocity profile and high velocity tricuspid regurgitation identifies patients with dilated cardiomyopathy who are at increased risk for development of heart failure and death.

Hypertrophic cardiomyopathy is characterized by left ventricular and/or right ventricular hypertrophy, which is usually asymmetric and involves the interventricular septum. It is a familial disease, with predominately autosomal dominant inheritance. Just as the inheritance of hypertrophic cardiomyopathy is heterogenous, so are the
phenotypic manifestations, even in a single family cohort with the same molecular genetic defect. The extent of hypertrophy at any given site can vary greatly and bears importantly on the manifestations of the disease. Mutations in sarcomeric contractile protein genes cause the cardiomyopathy. Typical morphological myocardial changes include myocyte hypertrophy and disarray surrounding areas of increased loose connective tissue. Abnormal thickening of coronary arteries may also occur. Arrhythmias and premature sudden death are common.

Although asymmetric septal hypertrophy is the most common type of morphologic pattern, hypertrophic cardiomyopathy can present with concentric, apical, or free wall left ventricular hypertrophy (12,13,14,15). The left ventricular outflow tract becomes narrowed because of the hypertrophied basal septum, providing conditions for dynamic obstruction (Figs. 33.4 and 33.5). The narrowed left ventricular outflow tract increases the velocity of blood flow during systole and produces a Venturi effect. Traditionally, it has been thought that because of the Venturi effect, the mitral valve leaflets and support apparatus are drawn toward the septum during systole (systolic anterior motion), obstructing the left ventricular outflow tract (contact with interventricular septum many occur). However, controversy exists regarding the contribution of the Venturi effect secondary to the increased ejection velocity (13). Most likely, this Venturi effect is the consequence rather than the origin of the left ventricular outflow tract gradient (13). It is believed that the narrow left ventricular outflow tract, caused by the ventricular septal hypertrophy and the anterior displacement of the papillary muscles and mitral leaflets, is important to the development of the obstruction, as is the fact that the mitral leaflets are elongated and coapt in the body of the leaflets, rather than at their tips, as is normal (15). That part of the anterior leaflet distal to the coaptation point is subjected to Venturi and/or drag forces, resulting in systolic anterior motion and subsequent mitral leaflet-septal contact, causing the subaortic obstruction (Fig. 33.6) (15). The systolic anterior motion of the anterior mitral leaflet also results in a failure of coaptation of the mitral leaflets, and it is through this funnel-shaped interleaflet gap that the mitral regurgitation is directed posteriorly into the left atrium (Fig. 33.7) (15). The obstruction is dynamic, may occur at the papillary muscle (midventricular) level as well as subaortic level, and depends on left ventricular loading conditions, left ventricular size, and left ventricular contractility. Because the left ventricular outflow tract obstruction is dynamic, patients in whom the disease is suspected, who do not have a gradient at rest, should undergo provocation maneuvers with agents such as dobutamine
to determine the severity of the gradient. If pressure gradients of greater than 30 mm Hg at rest are present, the potential for further hypertrophy and deterioration is highly likely (13). Obstruction of the left ventricular outflow tract may cause the aortic valve to close early (premature midsystolic closure). Systolic anterior motion of the mitral valve apparatus distorts mitral valve configuration, resulting in mitral insufficiency. Thus, varying degrees of mitral insufficiency almost invariably accompany the obstructive form of hypertrophic cardiomyopathy.