Basic Principles

Dilated cardiomyopathy presents clinically as heart failure with reduced ejection fraction (HFrEF). Typically, all four chambers are enlarged, and there is impaired systolic function of both the left ventricle (LV) and right ventricle (RV), due to a wide range of underlying causes (Table 9-1). The physiology of dilated cardiomyopathy (Fig. 9-1) is characterized predominantly by:

Clinically, patients most often have heart failure, with initial complaints ranging from symptoms of pulmonary or systemic venous congestion to symptoms of low forward cardiac output. Functional mitral regurgitation frequently is present secondary to LV and mitral annular dilation. In addition, pulmonary hypertension develops in many patients in response to the chronic elevation in left atrial (LA) pressure. Typically, LV diastolic dysfunction coexists with systolic dysfunction, although separating the hemodynamic effects of diastolic dysfunction from concurrent systolic dysfunction is challenging.

Echocardiographic Approach

The echocardiographic approach to the patient with heart failure symptoms should start with an evaluation of LV size, wall thickness, and systolic function (Figs. 9-2 and 9-3). Echocardiographic imaging from standard windows allows evaluation of the size and function of all four cardiac chambers using two-dimensional (2D) or three-dimensional (3D) imaging (Fig. 9-4): .

In addition to 2D and 3D imaging, other signs of poor LV systolic function include:

The increase in E-point to septal separation is due to a combination of LV dilation and reduced mitral leaflet motion caused by low transmitral flow rates. Reduced anteroposterior aortic root motion reflects reduced LA filling and emptying (Fig. 9-5). A reduced aortic ejection velocity indicates a reduced stroke volume, although compensatory mechanisms (including LV dilation) often result in a normal stroke volume at rest. A slow rate of rise in velocity of the mitral regurgitant jet indicates a reduced rate of rise in LV pressure in early systole (dP/dt).

The cause of functional mitral valve regurgitation (with an anatomically normal valve) is related to malalignment of the papillary muscles, ventricular systolic dysfunction, and annular dilation. Regurgitant severity ranges from mild to severe, as assessed with Doppler techniques (Fig. 9-6), although functional mitral regurgitation is considered severe with a smaller regurgitant orifice area and regurgitant volume than for primary mitral valve disease (see Table 12-6). Pulmonary pressures usually are elevated and can be estimated from the velocity of the tricuspid regurgitant jet, as described in Chapter 6.

The echocardiographic appearance of a dilated cardiomyopathy is fairly uniform despite a wide range of disease processes. Exceptions include fulminant myocarditis, in which there may be little ventricular dilation, despite severe systolic dysfunction. In Chagas heart disease, an LV apical aneurysm is seen in about half of patients; there is often thrombus formation, although global hypokinesis is typical with advanced disease (Fig. 9-7). Tako-tsubo cardiomyopathy is an acute, transient, stress-induced cardiomyopathy characterized by “apical ballooning” with apical dilation and dyskinesis but preserved dimensions and function of the cardiac base (Fig. 9-8).

Diastolic dysfunction typically accompanies systolic heart failure in patients with a dilated cardiomyopathy, and noninvasive estimates of filling pressures may be helpful in clinical management. When systolic dysfunction is present, the elevated end-systolic volume results in a shift along the pressure-volume curve to a steeper segment. This means that, for a given diastolic pressure-volume relationship, compliance is reduced at higher LV volumes. Thus the expected pattern of diastolic filling in dilated cardiomyopathy is that of reduced compliance: a high E velocity, rapid deceleration slope, low A velocity, and an E/A ratio >1 (Fig. 9-9). When filling pressures are elevated, the E/E′ ratio is increased to 15 or higher, and the pulmonary vein a-wave velocity and duration are increased. The M-mode finding of a delayed rate of mitral valve closure, termed a “B-bump” or “AC-shoulder” also correlates with an elevated end-diastolic pressure (see Fig. 9-5). However, patterns of diastolic dysfunction can be complex in patients with a dilated cardiomyopathy and vary with volume status, medical therapy, and phase of the disease course.

When significant LV systolic dysfunction is present (ejection fraction <35%), a careful search for apical LV thrombus is indicated, although prevalence is low with current medical therapy (Fig. 9-10). Details on the technical aspects of identifying an LV thrombus are given in Chapter 8.

Limitations and Technical Considerations

Echocardiography rarely can establish the etiology of a dilated cardiomyopathy, even though it is instrumental both in confirming the presence of ventricular dysfunction and in providing prognostic data. The accuracy of measures of ventricular volumes and ejection fraction depend on attention to data acquisition and analysis as discussed in Chapter 6. In addition to the technical aspects in the evaluation of diastolic dysfunction, as discussed in Chapter 7, diastolic and systolic function are inseparable parts of cardiac performance. Isolating the effects of diastolic dysfunction from the altered loading conditions related to systolic dysfunction can be problematic. Most patients have combined systolic and diastolic dysfunction with both contributing to clinical symptoms and outcomes.

Clinical Utility

Echocardiography plays a key role in the evaluation and management of patients with heart failure. The correlation between echocardiographic findings and specific causes of heart failure is shown in Table 9-2. If an echocardiography shows no significant impairment of LV systolic dysfunction, other possible diagnoses include:

Whenever the clinical presentation suggests heart failure, a comprehensive examination of systolic and diastolic function is needed, even when the core echocardiographic examination does not show obvious evidence of dysfunction. If the echocardiogram is consistent with the clinical diagnosis of dilated cardiomyopathy, detailed information on ventricular function, chamber sizes, associated valvular disease, and pulmonary artery pressures should be obtained.

Periodic echocardiography is essential for optimal care of patients with dilated cardiomyopathy. The detailed assessment available by echocardiography aids in the appropriate tailoring of medical therapy. In addition, repeat echocardiography may be helpful when a change in clinical status suggests an interval change in ventricular function. The role of echocardiography in a selection of patients for cardiac resynchronization therapy is in evolution. Myocardial dyssynchrony can be evaluated by tissue Doppler and speckle tracking techniques (Fig. 9-11) as discussed in Chapter 4 and in Suggested Reading 1. After resynchronization with biventricular pacing, benefit can be measured by the reduction in LV size, improvement in systolic function, and decrease in mitral regurgitant severity.

In patients with dilated cardiomyopathy in the intensive care unit, echocardiographic evaluation can be helpful in to assess LV function, pulmonary artery pressures, the degree of coexisting mitral regurgitation, and to estimate LV filling pressure. Evaluation of an individual patient’s response to afterload reduction therapy can be performed by repeat ejection fraction measurements or by sequential noninvasive measurements of pulmonary pressures and cardiac output (Fig. 9-12).

Alternate Approaches

Evaluation of a patient with new onset heart failure typically includes a careful clinical evaluation and laboratory data. In many patients with dilated cardiomyopathy, an exact etiology cannot be identified, even when all diagnostic modalities are used. Coronary angiography may be appropriate to evaluate for an ischemic cause. If exact measurement of pulmonary vascular resistance is needed (e.g., in a heart transplant candidate), cardiac catheterization is indicated because noninvasive approaches provide only an estimate of pulmonary vascular resistance.

Basic Principles

Hypertrophic cardiomyopathy is an autosomal dominant inherited disease of the myocardium (with variable penetrance) related to abnormalities in genes coding for contractile proteins. Characteristic anatomic features of this disease (Fig. 9-13) include:

Other important clinical features of this disease are a high risk of sudden death (especially during exertion); symptoms of angina, exercise intolerance, and syncope; a high prevalence of atrial fibrillation; and a systolic murmur on cardiac auscultation.

The pattern and degree of LV hypertrophy in patients with hypertrophic cardiomyopathy can be quite variable (Fig. 9-14). The septum may be primarily hypertrophied at the base with a sigmoid shape of the septum, or there can be severe septal hypertrophy with bulging into the LV chamber. With apical hypertrophic cardiomyopathy, there is severe hypertrophy confined to the LV apex, sometimes with near obliteration of the LV cavity in systole. The common feature of all these hypertrophy patterns is normal thickness (or “sparing”) of the basal posterior LV wall.

Hypertrophic cardiomyopathy is classified as:

With dynamic obstruction, there is an increase in flow velocity, and corresponding pressure gradient, proximal to the aortic valve, in association with systolic anterior motion of the mitral valve toward the hypertrophied ventricular septum (Fig. 9-15). Obstruction is dynamic rather than fixed, both in the sense that it occurs only in mid to late systole and in the sense that the presence and severity of obstruction can be altered by loading conditions. These features contrast with the relatively fixed obstruction of aortic valve stenosis, which persists from the onset to the end of ejection and in which the severity of the stenosis is relatively insensitive to changes in loading conditions. Dynamic outflow obstruction in hypertrophic cardiomyopathy typically has a pattern of onset in mid-systole, with the maximum LV to aortic pressure gradient occurring in late systole.

Obstruction can be diminished by maneuvers that increase ventricular volume—such as an increase in preload or a decrease in contractility—or by maneuvers that increase afterload. Conversely, the degree of obstruction is increased by:

Each of these physiologic changes results in a decrease in LV volume and an increase in the degree of dynamic obstruction, with a louder murmur and an increased Doppler velocity.

Dynamic outflow obstruction usually is associated with mitral regurgitation because the systolic anterior motion of the leaflets disrupts normal coaptation. A posteriorly directed mitral regurgitant jet of mild to moderate severity originates at the malcoapted segment of the leaflets (Fig. 9-16).

LV systolic function typically is normal in patients with hypertrophic cardiomyopathy. However, LV diastolic function is abnormal, with impaired relaxation and decreased compliance, accounting for many of the heart failure symptoms in patients with hypertrophic cardiomyopathy.

Echocardiographic Approach

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