Amyloidosis causes which type of cardiomyopathy?
Correct Answer: Restrictive
Description: Ans. B. Restrictive. (Ref. Robbins Basic Pathology 8th/ Table 11-5).Restrictive cardiomyopathy results in a stiff, noncompliant myocardium and can be due to depositions (e.g., amyloidosis and hemochromatosis), increased interstitial fibrosis (e.g., caused by irradiation), or to endomyocardial scarring. Myocarditis results from muscle injury caused by an inflammatory process that may be secondary to infections or immune reactions. Coxsackieviruses A and B are the most common causes in the U.S. Clinically, myocarditis may be asymptomatic, give rise to acute heart failure, or evolve into dilated cardiomyopathy.Cardiomyopathy is a term applied to intrinsic disease of the cardiac muscle; there may be specific causes, or it may be idiopathic. There are three general pathophysiologic categories of cardiomyopathy: dilated (90%), hypertrophic, and restrictive (least common). Dilated cardiomyopathy results in systolic (contractile) dysfunction. It may be acquired, for example, following myocarditis, toxic exposures (e.g., alcohol), or pregnancy (peripartum). In 25% to 35% of cases genetic defects in cytoskeletal proteins are causal. Hypertrophic cardiomyopathy results in diastolic (relaxation) dysfunction. The vast majority of cases are due to autosomal dominant mutations in the genes encoding the contractile apparatus, in particular ?-myosin heavy chain. RCM.Cardiomyopathy and Indirect Myocardial Dysfunction: Functional patterns and causes.Functional PatternLeft Ventricular Ejection Fraction*Mechanisms of Heart FailureCausesIndirect Myocardial Dysfunction (Not Cardiomyopathy)Dilated<40%Impairment of contractility (systolic dysfunction)Idiopathic; alcohol; peripartum; genetic; myocarditis; chronic anemia; doxorubicin (Adriamycin)Ischemic heart disease; valvular heart disease; hypertensive heart disease; congenital heart diseaseHypertrophic50% to 80%Impairment of compliance (diastolic dysfunction)Genetic; Friedreich ataxia; storage diseases; infants of diabetic mothersHypertensive heart disease; aortic stenosisRestrictive45% to 90%Impairment of compliance (diastolic dysfunction)Idiopathic; amyloidosisQ; hemochromatosis; sarcoidosis; radiation-induced fibrosisPericardial constriction# The heart in PCM is characteristically enlarged and flabby, with dilation of all chambers. Because of the wall thinning that accompanies dilation, the ventricular thickness may be less than, equal to, or greater than normal. Mural thrombi are common and may be a source of thromboemboli. By definition there is no primary valve pathology. Microscopically most myocytes are hypertrophied with enlarged nuclei, but many are attenuated, stretched, and irregular. There is variable interstitial and endocardial fibrosis.# The essential gross feature of HCM is massive myocardial hypertrophy without ventricular dilation. The classic pattern of HCM involves disproportionate thickening of the ventricular septum relative to the left ventricle free wall (so-called asymmetrical septal hypertrophy). On longitudinal sectioning, the ventricular cavity loses its usual round- to-ovoid shape and "banana-like" configuration. The characteristic histologic features in HCM are severe myocyte hypertrophy, myocyte (and myofiber) disarray, and interstitial and replacement fibrosis.# In idiopathic restrictive cardiomyopathy the ventricles are of approximately normal size or slightly enlarged, the cavities are not dilated, and the myocardium is firm. Biatrial dilation is commonly observed. Microscopically there is interstitial fibrosis, varying from minimal and patchy to extensive and diffuse. Restrictive cardiomyopathy of disparate causes may have similar gross morphology. However, endomyocardial biopsy can reveal disease-specific features (e.g., amyloid, iron overload, sarcoid granulomas).
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