Cardiomyopathies, Hypertensive and Pulmonary Heart Disease

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Cardiomyopathies, Hypertensive and Pulmonary Heart Disease




DILATED CARDIOMYOPATHY



HYPERTROPHIC CARDIOMYOPATHY



RESTRICTIVE CARDIOMYOPATHY



OTHER CARDIOMYOPATHIES



ADVANCED HEART FAILURE THERAPIES



HYPERTENSIVE HEART DISEASE



PULMONARY HEART DISEASE



SUGGESTED READING


Cardiomyopathy is defined as a primary disease of the myocardium, excluding myocardial dysfunction due to ischemia or chronic valvular disease. There are several possible approaches to the classification of cardiomyopathies, such as etiology or anatomy, but a physiologic classification is most useful clinically. The three basic physiologic categories of cardiomyopathy are:



The disease process in an individual patient may correspond closely with one of these physiologic categories; however, overlap between these categories (particularly between dilated and restrictive) can occur. Echocardiographic evaluation focuses on confirming the diagnosis and type of cardiomyopathy present and on defining the physiologic consequences of the disease process in that individual.


While hypertensive and pulmonary heart disease are not primary diseases of the heart muscle, they are included in this chapter because their clinical and echocardiographic presentation may mimic a cardiomyopathy. In addition, evaluation of patients receiving advanced heart failure therapies is outlined. End-stage coronary disease resulting in LV systolic dysfunction, sometimes referred to as “ischemic cardiomyopathy,” is discussed in Chapter 8.



Dilated Cardiomyopathy



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).





Hypertrophic Cardiomyopathy



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



Left Ventricular Asymmetric 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 posterobasal 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). Two-dimensional guided M-mode tracings are used for the measurement of septal and posterior wall thickness, 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, 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 is relevant if percutaneous catheter ablation is being considered. Parasternal short-axis views from base to apex allow assessment of the lateromedial 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 resulting in a more acute angle between the basal septum and aortic root. There is no convincing evidence that this septal contour pattern is inherited or associated with clinical events, so these patients should not be considered to have hypertrophic cardiomyopathy.


Apical views again allow 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 may be located up to one third the distance from the apical epicardium to the base) may be missed if image quality is suboptimal (Fig. 9-17). In some cases, the epicardium may be 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 better define the endocardial border. Qualitative and quantitative evaluations of LV systolic function are performed using standard approaches (see Chapter 6).



Jul 10, 2018 | Posted by in CARDIOLOGY | Comments Off on Cardiomyopathies, Hypertensive and Pulmonary Heart Disease
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