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Part 2 book “Essential echocardiography - A companion to braunwald’s heart disease” has contents: Restrictive and infiltrative cardiomyopathies, echocardiography in assessment of cardiac synchrony, echocardiography in assessment of ventricular assist devices, stress echocardiography and echo in cardiopulmonary testing,… and other contents.
24 Restrictive and Infiltrative Cardiomyopathies Vikram Agarwal, Rodney H Falk INTRODUCTION Restrictive cardiomyopathy (RCM) refers to either an idiopathic or a systemic myocardial disorder in the absence of underlying atherosclerotic coronary artery disease, valvular disease, congenital heart disease, or systemic hypertension, which is characterized by abnormal left ventricular filling, and is associated with normal or reduced left ventricle (LV) and right ventricle (RV) volumes and function.1 The term is not precise, but it incorporates infiltrative and fibrotic cardiac pathology, which are dealt with in this chapter While the majority of patients with infiltrative and fibrotic cardiomyopathies develop a restrictive filling pattern, especially in the later stages of the disease, it is important to differentiate the pathology from a restrictive filling pattern, which can be associated with other types of heart disease, such as dilated cardiomyopathy In patients with dilated cardiomyopathy the restrictive filling pattern is often a reversible phenomenon, related to worsening heart failure, and morphologically the ventricle is dilated, usually with severe reduction in ejection fraction Although the clinical presentation of RCM may be similar to dilated cardiomyopathy, the nondilated, stiff ventricles often result in highly sodium-sensitive heart failure symptoms, associated in the late stage of the disease with a low cardiac output due to the small stroke volume Because of the restriction to diastolic filling and an associated impaired ability to augment cardiac output at higher heart rates, these patients may also present with symptoms of exercise intolerance Diastolic dysfunction in the presence of preserved left ventricular ejection fraction (LVEF) is the key component of pathophysiology of RCM Initial stages of RCM demonstrate preserved LVEF with noncompliant walls that impair the normal diastolic filling of the ventricle This restriction can be isolated to either ventricle, or show biventricular involvement Biventricular volumes are either normal or reduced Over a period of time, the chronically elevated LV diastolic pressure leads to increased atrial size, which may be considerable Although severe biatrial enlargement without valve disease is a classic finding of RCM, this is a nonspecific feature, as it may occur in other conditions, particularly if associated with long-standing atrial fibrillation In later stages of the disease, as the compliance of the LV decreases, a small change in LV volume is associated with a steep rise in LV pressure A reduced ejection fraction may occur in the very late stages of the disease It is important to recognize that, although the left ventricle may show diastolic dysfunction with a normal ejection fraction, longitudinal systolic function may be significantly impaired, and thus a normal ejection fraction should not be considered synonymous with normal systolic function (Videos 24.1 and 24.2) SPECTRUM OF RESTRICTIVE CARDIOMYOPATHY RCM can be considered as either “primary” RCM or RCM secondary to other conditions such as infiltrative disorders and storage disorders Infiltrative disorders primarily affect the interstitial space of the myocardium, whereas storage diseases are associated with deposits within the cardiac myocytes In addition, endomyocardial involvement, leading to restriction, may occur in a variety of uncommon conditions (Box 24.1) Diagnosis of Restrictive Cardiomyopathy Due to the varied pathophysiology and clinical manifestations of the underlying systemic process, a systematic approach, beginning with a comprehensive history and detailed systemic evaluation, can help guide further management Among patients with suspected idiopathic and familial RCM, a comprehensive family history should be obtained, as the condition is increasingly being recognized as familial Clinical screening of first-degree relatives should be considered, and abnormalities, if present, may include hypertrophic and dilated cardiomyopathy Comprehensive genetic screening should also be considered, particularly if family members with suspicious cardiac abnormalities are identified ECHOCARDIOGRAPHY IN RESTRICTIVE CARDIOMYOPATHY Cardiac imaging plays a pivotal role in establishing the diagnosis of RCM Despite the availability of multiple cardiac imaging options, including cardiac magnetic resonance (CMR) imaging and nuclear cardiology, echocardiography remains the initial imaging method of choice among patients with suspicion of RCM Echocardiography not only assesses the anatomy and function of the cardiac chambers, but it can also provide vital clues to the diagnosis of the underlying etiology The first step in cardiac assessment when interpreting an echocardiogram in suspected restrictive heart disease involves a thorough evaluation of the overall and regional anatomy of the left ventricle with regard to underlying wall thickness, altered myocardial texture, and wall motion abnormality LV mass assessed by using threedimensional (3D) echocardiogram is more reproducible, and mirrors the mass obtained by cardiac MR more closely Similarly, while the quantitative assessment of overall left ventricular volumes and systolic function assessment are usually performed using the biplane method of disks (modified Simpson’s rule), the use of 3D-based volumes and ejection fraction, when feasible and available, is encouraged since it does not rely on underlying geometric assumptions leading to superior accuracy and reproducibility Nevertheless, two-dimensional (2D) echocardiography can give extremely useful diagnostic information, and the use of contrast for better delineation of the endocardium when two or more contiguous LV endocardial segments are poorly visualized in apical views improves accuracy and reduces interreader variability of LV functional analyses In “primary” RCM, ventricular wall thickness is usually normal, whereas the myocardium in patients with cardiac amyloidosis is usually thickened, and may show increased echogenicity It is also important to evaluate the right ventricular wall thickness and function, as involvement of right ventricle may have prognostic significance in a number of diseases Doppler Features Diastolic functional assessment of myocardium plays an important role in the diagnosis of RCM In the early stages of restrictive heart diseases, the myocardial relaxation (e′) is reduced, resulting in septal e′ less than cm/s and lateral e′ less than 10 cm/s (Fig 21.1A and B) In early stages of the disease, the mitral inflow pulse-wave Doppler shows an abnormal relaxation pattern, is characterized by an E/A ratio of ≤0.8, an increased mitral inflow E-wave deceleration time (≥240 ms), and an increased isovolumic relaxation time (>90 ms) At this stage of the disease, the left atrium is usually normal or mildly dilated in size, and the patient is rarely symptomatic As this pattern is common in older patients in the general population, it is nondiagnostic even in a gene-positive patient With progression of disease, the mitral inflow pulse wave Doppler pattern shows pseudonormal filling pattern, where the E/A ratio is 0.8–2, and this ratio reverses with Valsalva maneuver Due to the elevated left ventricular 245 246 Echocardiography for Diseases of the Myocardium filling pressures, there is an increase of the E/e′ ratio (≥10) and the left IV atrial volume index is elevated, ≥34 mL/m2 There is also a reversal in the pulmonary vein Doppler velocity pattern, with gradual blunting of the systolic wave and dominance of the diastolic wave (S/D 1; see Fig 24.1C and D) With further deterioration of BOX 24.1 Cardiac Diseases Associated With Restrictive Pathophysiology Primary RCM • Idiopathic and familial RCM • Mitochondrial cardiomyopathy Infiltrative Diseases • Amyloidosis • Mucopolysaccharoidoses (Hurler syndrome, Gaucher disease) Storage Diseases • Anderson-Fabry disease • Glycogen storage disorders • Hemochromatosis (may present with restrictive or, more commonly, dilated phenotype) Endomyocardial Involvement • Endomyocardial fibrosis and Lưffler endocarditis • Carcinoid syndrome • Postradiation • Postchemotherapy • Lymphoma • Scleroderma • Churg-Strauss syndrome • Pseudoxanthoma elasticum RCM, Restrictive cardiomyopathy e′ A ventricular compliance, advanced diastolic dysfunction develops, characterized by a restrictive filling pattern, namely an E/A ratio greater than 2, and a short (50% (5–10) mm Hg if IVC diameter ≤21 mm and collapses 21 mm and collapses >50% 15 mm Hg if IVC diameter >21 mm and collapses