<prompt> Amyloidosis causes which type of cardiomyopathy?ConstrictiveRestrictiveHypertrophicAny of the above  <response>: 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 FractionMechanisms of Heart FailureCausesIndirect Myocardial Dysfunction Not CardiomyopathyDilated40Impairment of contractility systolic dysfunctionIdiopathic; alcohol; peripartum; genetic; myocarditis; chronic anemia; doxorubicin AdriamycinIschemic heart disease; valvular heart disease; hypertensive heart disease; congenital heart diseaseHypertrophic50 to 80Impairment of compliance diastolic dysfunctionGenetic; Friedreich ataxia; storage diseases; infants of diabetic mothersHypertensive heart disease; aortic stenosisRestrictive45 to 90Impairment of compliance diastolic dysfunctionIdiopathic; 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. 