Correct answer for yesterdays USMLE-style question is D! See explanation below. Any questions? Ask and well answer! D) This patient has hypertrophic cardiomyopathy (HCM). It is an autosomal dominant disease, typically of a beta-myosin heavy chain mutation, that causes myocardial fibers to be arranged in a tangled, disoriented, and hypertrophied manner. There is a degree of phenotypic variation amongst patients with HCM, however, the disease most commonly leads to an asymmetric concentric hypertrophy of the interventricular septum. The disease can be asymptomatic, however it is the leading cause of sudden death in young athletes. Mortality is almost always secondary to ventricular arrhythmia. On exam, the point of maximum impulse is in the normal location, however, the apical impulse is sustained. Auscultation reveals an S4 and a systolic murmur that increases with Valsalva. The murmur of HCM and of mitral valve prolapse are the only two murmurs that increase with the Valsalva maneuver. The recent gonorrheal infection treated and escitalopram are unrelated. Explanations of incorrect answers: A) A degree of concentric hypertrophy of the left ventricle may occur in hypertrophic cardiomyopathy (HCM), as the degree and distribution of the myocardial hypertrophy varies in patients with HCM. However, HCM is classically identified by its asymmetric nature. Concentric hypertrophy of the left ventricle is associated with conditions that increase left ventricular afterload over a long period of time, mainly hypertension and aortic stenosis. B) Apple-green birefringence when stained with Congo red is characteristic of amyloidosis. Cardiac amyloid causes restrictive cardiomyopathy, which presents with signs and symptoms of heart failure. The extracellular amyloid infiltrate impairs ventricular relaxation. Consequently, diastolic filling is incomplete. The exam of the patient in this vignette is not suggestive of restrictive disease, as a restrictive cardiomyopathy alone does not a cause a murmur (one would be appreciated if a patient had unrelated valvular dysfunction), nor would a restrictive cardiomyopathy lead to a sustained apical impulse. C) Non-caseating epithelioid granulomas is characteristic of sarcoidosis. Cardiac sarcoid is rare, but when present, is usually associated with conduction abnormalities. E) Eccentric hypertrophy is caused by chronic volume overload (in contrast to concentric hypertrophy, which is caused by longstanding pressure overload). Valvular abnormalities, such as aortic regurgitation, lead to volume overload. Cardiac sarcomeres lengthen (instead of thicken), and cause eccentric hypertrophy. While hypertrophic obstructive cardiomyopathy does cause asymmetric hypertrophy of the interventricular septum, it is not eccentric. firecracker.me
Posted on: Tue, 20 May 2014 15:50:45 +0000
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