MEDizzy - A patient is noted to have a crescendo-decrescendo

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Cardiovascular medicine

A patient is noted to have a crescendo-decrescendo midsystolic murmur on examination.The murmur is loudest at the left sternal border. The patient is asked to squat, and the murmur decreases in intensity. The patient stands and the murmur increases. Finally, the patient is asked to perform a Valsalva maneuver and the murmur increases in intensity. Which of the following is most likely to be the cause of this murmur?

ExplanationCauses of midsystolic murmurs include aortic stenosis, aortic sclerosis, hypertrophic cardiomyopathy (HOCM), coarctation of the aorta, and pulmonary valve stenosis. In the obstructive form of HOCM, maneuvers that increase the amount of outflow obstruction will increase the intensity of the murmur. Outflow obstruction is increased by decreasing preload, which occurs in standing, performing a Valsalva maneuver, or with the administration of vasodilators. Increasing preload by squatting or passive leg raise will lead to reduction of outflow tract obstruction and a diminished murmur.The murmur of HOCM will also decrease with increasing afterload (vasopressors) or decreasing contractility (beta blockers). The murmur of aortic stenosis is typically in the right second intercostal space and radiates to the carotids. Valsalva maneuver will classically lead to a decreased aortic stenosis murmur.The murmur of congenital pulmonic stenosis is in the right second intercostal space.There is often a parasternal lift. Mitral valve prolapse causes a late systolic murmur usually introduced by an ejection click. It does not cause a crescendodecrescendo murmur. Chronic mitral regurgitation causes a holosystolic murmur that radiates to the apex.