Cardiomyopathies, Hypertensive and Pulmonary Heart Disease

Basic Principles

Dilated cardiomyopathy manifests clinically as heart failure with reduced ejection fraction (HFrEF). Typically, all four chambers are enlarged, and impaired systolic function of both the LV and right ventricle (RV) occurs, due to a wide range of underlying causes ( Table 9.1 ). The physiology of dilated cardiomyopathy ( Fig. 9.1 ) is characterized predominantly by:

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  Impaired LV contractility

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  Reduced cardiac output

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  Elevated LV end-diastolic pressure

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. Secondary 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 ):

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  LV systolic function

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    Qualitative global and regional systolic function

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    Quantitative end-diastolic and end-systolic dimensions or volumes

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    Ejection fraction

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  RV systolic function

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    Qualitative size and systolic function

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    Pulmonary artery systolic pressure and estimated resistance

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  LA size

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    Qualitative size and linear dimensions

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    Quantitation of LA volumes

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

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  M-mode

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    Increased mitral E-point to septal separation (EPSS)

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    Reduced anteroposterior aortic root motion

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    Delayed mitral valve closure

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  Doppler

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    Reduced aortic ejection velocity

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    Reduced rate of rise in ventricular pressure (dP/dt)

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    Secondary mitral regurgitation

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    Diastolic dysfunction

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 secondary mitral valve regurgitation (with an anatomically normal valve) is related to misalignment 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 ; see Table 12.8 ). 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 dilated cardiomyopathy is fairly uniform despite a wide range of disease processes. Exceptions include fulminant myocarditis, in which little ventricular dilation is present, despite severe systolic dysfunction. In Chagas heart disease, an LV apical aneurysm is seen in about half of patients; thrombus formation is often seen, 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 dilated cardiomyopathy, and noninvasive estimates of filling pressures are 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 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 function 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 echocardiography shows no significant impairment of LV systolic dysfunction, other possible diagnoses include:

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  Coronary artery disease

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  Valve disease

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  Hypertensive heart disease

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  Pericardial disease

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  Pulmonary heart disease

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 is helpful when a change in clinical status suggests an interval change in ventricular function. Myocardial dyssynchrony can be evaluated by tissue Doppler and speckle tracking techniques ( Fig. 9.11 ) although the role of this information in clinical practice not well established.

In patients with dilated cardiomyopathy in the intensive care unit, echocardiographic evaluation can be helpful in to assess LV function, pulmonary artery pressures, and 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. Cardiac magnetic resonance imaging provides evaluation of myocardial fibrosis and inflammation. The possibility of an ischemic cause of LV systolic dysfunction relies on visualization of coronary anatomy by computed tomography or at cardiac catheterization. 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:

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  Asymmetric hypertrophy of the LV

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  Normal LV systolic function

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  Impaired diastolic LV function

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  Dynamic subaortic LV outflow obstruction

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 often is primarily hypertrophied at the base with a sigmoid shape of the septum, or severe septal hypertrophy can occur, with bulging into the LV chamber. With apical hypertrophic cardiomyopathy severe hypertrophy is 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:

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  Nonobstructive (about one third of patients) if the outflow gradient at rest and with provocation is <30 mmHg

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  Obstructive if the gradient at rest is ≥30 mmHg (>2.7 m/s)

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  Provocable or latent if the resting gradient is <30 mmHg but obstruction occurs with exercise (or other maneuvers)

With dynamic obstruction, one sees 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 (e.g., an increase in preload or a decrease in contractility) or by maneuvers that increase afterload. Conversely, the degree of obstruction is increased by:

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  Reduced preload

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  Increased contractility

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  Decreased afterload

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, thus accounting for many of the heart failure symptoms in patients with hypertrophic cardiomyopathy.

Echocardiographic Approach

Asymmetric Left Ventricular Hypertrophy

Evaluation of the pattern and extent of LV hypertrophy is made from multiple tomographic 2D image planes. In the parasternal long-axis view, particular attention is focused on the posterior basal wall between the papillary muscle and the mitral annulus. Although the wall in this region is not thickened in most patients with hypertrophic cardiomyopathy, it is thickened in patients with concentric hypertrophy due to other etiologies (e.g., hypertension, infiltrative cardiomyopathy). 2D guided M-mode tracings are used for the measurement of septal and posterior wall thickness, by using both long- and short-axis views to ensure that the measurements are perpendicular to the LV wall and to avoid inclusion of RV trabeculation in the septal wall thickness. Careful measurements of diastolic septal thickness provide prognostic information (e.g., risk of sudden death) and are essential for decision making about septal reduction procedures.

The parasternal long-axis view also offers the best opportunity to define the exact relationship between the pattern of septal hypertrophy and the outflow tract. This is important when a surgical approach, such as septal myectomy, is being considered because surgical visualization usually is retrograde across the aortic valve, thereby allowing only limited direct inspection of the septal endocardium and little information on the extent of septal thickening or the degree of septal curvature. The extent and pattern of hypertrophy also are relevant if alcohol septal ablation is being considered. Parasternal short-axis views from base to apex allow assessment of the medial to lateral extent of the hypertrophic process.

It is important to recognize that some degree of bulging of the septum into the LV outflow tract, often called a septal “knuckle,” is seen in normal older individuals. This apparent septal prominence most likely is due to increased tortuosity of the aorta that results in a more acute angle between the basal septum and aortic root. Most patients with this anatomy do not have convincing clinical features of hypertrophic cardiomyopathy.

Apical views are essential for complete visualization of the pattern and extent of hypertrophy. Diagnosis of apical hypertrophy can be difficult because endocardial definition may be poor, and the endocardial surface (which is located up to one third the distance from the apical epicardium to the base) is missed if image quality is suboptimal ( Fig. 9.17 ). In some cases, the epicardium is mistaken for the apical endocardium . A careful examination, when the referring physician has alerted the echocardiographer to this possible diagnosis, avoids this potential pitfall. Color or pulsed Doppler examination is helpful in demonstrating the absence of blood flow in the “apical” region, which is occupied by the hypertrophied myocardium. If needed, echo contrast can be used to define the endocardial border more clearly. Qualitative and quantitative evaluations of LV systolic function are performed using standard approaches (see Chapter 6 ).

Dynamic Subaortic LV Outflow Tract Obstruction

In about 70% of patients with hypertrophic cardiomyopathy, subaortic obstruction is present, at rest or with exercise, and characterized by:

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  Systolic anterior motion of the mitral leaflet

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  Mid-systolic closure of the aortic valve

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  Late-peaking, high-velocity flow in the outflow tract

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  Variability in the severity of obstruction with maneuvers:

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    Post-premature ventricular contraction beats

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    Valsalva maneuver

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    Exercise

Imaging

In a patient with dynamic LV outflow tract obstruction, long-axis images show the classic finding of systolic anterior motion of the mitral valve with apposition of the mitral leaflet and septum in mid to late systole. M-mode recordings are helpful in that, with pathologic systolic anterior motion, the rate of anterior leaflet motion is more rapid than the anterior motion of the posterior wall in systole ( Fig. 9.18 ). A “contact lesion” on the ventricular septum at the site of mitral leaflet impingement is seen in some patients.

Short-axis views also show the systolic anterior motion of the mitral valve leaflets. Frame-by-frame analysis shows the cross-sectional area of the outflow tract throughout systole.

Apical 2D views are helpful for demonstrating the abnormal mitral leaflet motion, especially the apical long-axis and the anteriorly angulated four-chamber views. Note that the degree of systolic anterior motion is not always uniform from medial to lateral across the mitral leaflets, so imaging in multiple planes with slight adjustments in transducer angulation are needed to demonstrate the presence and extent of dynamic outflow obstruction.

The aortic valve shows normal leaflet opening in early systole, followed by mid-systolic abrupt partial closure with coarse fluttering of the aortic valve leaflets in late systole due to late systolic dynamic outflow obstruction. Again, these rapid leaflet movements are best documented on M-mode recordings. Often the aortic leaflets themselves are sclerotic because of the long-term effect of a turbulent jet as a result of subaortic obstruction, with some degree of coexisting aortic regurgitation.

Doppler Evaluation

Doppler studies provide a more direct evaluation of the presence, location, and degree of dynamic subaortic obstruction than do imaging techniques. With conventional pulsed or color flow imaging, the site of obstruction is identified based on the location of the poststenotic turbulence. Both parasternal and apical long-axis views are useful for this examination.

Using pulsed Doppler from an apical approach, the sample volume is slowly moved from the apex progressively toward the base, recording the velocity curve at each step. Proximal to the outflow obstruction, velocities are normal. At the site of obstruction, the velocity increases abruptly to a velocity reflecting the degree of obstruction (as stated in the Bernoulli equation). This approach, using stepwise evaluation with pulsed Doppler ultrasound, is advantageous in that intracavity gradients due to apical hypertrophy or apposition of the papillary muscle with the septum will be recognized and not mistaken for subaortic dynamic obstruction.

Continuous-wave (CW) Doppler from an apical approach typically shows a late-peaking, high-velocity systolic jet in patients with a dynamic LV outflow tract obstruction ( Fig. 9.19 ). The shape of this curve is distinctive, corresponding to the temporal course of the LV to aortic pressure gradient (see Fig. 9.15 ).

Latent Outflow Obstruction

Some patients with hypertrophic cardiomyopathy have dynamic outflow obstruction with exercise but not at rest. Traditionally, maneuvers to “provoke” outflow obstruction at rest were performed during the echocardiography examination. A spontaneous premature ventricular contraction (PVC) results in an increased degree of obstruction on the post-PVC beat due to increased LV contractility. The strain phase of the Valsalva maneuver increases obstruction by decreasing preload (smaller LV cavity size), but it is difficult to perform simultaneously with echocardiography because of changes in cardiac position and lung interference as the patient performs the maneuver. In the past, amyl nitrate inhalation was used to induce a brief decrease in preload (venodilation) and decrease in afterload (arterial dilation), both of which increase the degree of obstruction. However, these maneuvers are no longer recommended because of low reproducibly and limited clinical value.

The optimal approach to evaluate for provocable obstruction is a supine bicycle or upright treadmill exercise stress test. CW Doppler outflow velocity recordings are made at rest and immediately after exercise to assess for inducible outflow obstruction, defined as an exercise outflow tract gradient ≥30 mmHg (velocity ≥2.7 m/s) ( Fig. 9.20 ). Pharmacologic stress testing with dobutamine is not recommended because it is nonspecific (mid-cavity obstruction is seen even in normal individuals) and does not provide information on exercise capacity or the relationship of symptoms to exertion.

Limitations and Technical Considerations

When a high-velocity outflow signal is detected with CW Doppler, other techniques are needed to determine the depth of origin of the signal because velocities are measured along the entire length of the ultrasound beam. In some patients with hypertensive heart disease or hypovolemia, the combination of LV hypertrophy and hyperdynamic systolic function results in a late-peaking, high-velocity systolic waveform ( Fig. 9.21 ) similar to that seen in hypertrophic cardiomyopathy. However, in these patients the site of obstruction is not subaortic; it is closer to the apex, at the mid-ventricular level.

The distinction between hypertrophic cardiomyopathy and a hyperdynamic concentrically hypertrophied ventricle can be made by careful attention to the 2D images (sparing of the basal posterior wall in hypertrophic cardiomyopathy) and by evaluating the depth of origin of the high-velocity jet using conventional pulsed, high pulse repetition frequency (HPRF), and color Doppler techniques. The patient's clinical and family histories also are important for making this distinction. Genetic testing is increasingly a routine part of the diagnostic evaluation.

Distinguishing between the signal due to dynamic subaortic obstruction and mitral regurgitation can be challenging because both are common with hypertrophic cardiomyopathy, and both are high-velocity systolic signals directed away from the apex. The two features that are helpful in this distinction are: (1) the shape of the velocity curve (late peaking with subaortic obstruction versus a rapid early systolic rise in velocity with mitral regurgitation) and (2) the timing of flow (mitral regurgitation is longer in duration, starting earlier and ending later in the cardiac cycle) ( Fig. 9.22 ).

Clinical Utility

Monitoring of Alcohol Septal Ablation

Echocardiography plays a key role in patient selection for catheter septal ablation procedures and for monitoring the procedure in the catheterization laboratory. In the patient being considered for alcohol septal ablation or surgical treatment for hypertrophic cardiomyopathy, knowledge of the extent, distribution, and curvature of septal hypertrophy determines the location and size of the muscle segment to be removed or ablated. In the catheterization laboratory, contrast is injected during echocardiographic imaging, with the catheter positioned in a septal coronary branch to show the specific location and extent of the area perfused by that vessel before the delivery of the ablation agent ( Fig. 9.23 ). Baseline and postprocedure Doppler data are used in conjunction with invasive hemodynamics to assess the reduction in outflow obstruction. After the procedure, sequential echocardiographic studies may show continued improvement in the extent of outflow obstruction due to healing and fibrosis of the infarcted septal myocardium.