Review Question - QID 217318

This patient presents with exertional dyspnea, multiple syncopal episodes during exertion, a family history of sudden cardiac death, and a harsh systolic heart murmur, which are consistent with hypertrophic obstructive cardiomyopathy (HOCM). Medications that decrease preload and/or afterload, such as nitroglycerin, worsen the murmur and symptoms of HOCM.

HOCM is characterized by cardiac muscle hypertrophy, especially at the interventricular septum. The systolic anterior motion of the mitral valve during systole causes left ventricular outflow tract obstruction. The severity of symptoms of HOCM is dependent on the degree of left ventricular outflow tract obstruction. Patients present with fatigue, exertional dyspnea, chest pain, palpitations, and syncopal episodes. HOCM is inherited in an autosomal dominant fashion, so a strong family history of sudden cardiac death is typical. A harsh crescendo-decrescendo systolic murmur is heard at the apex on cardiac auscultation. The murmur decreases with any increase in preload (e.g., squatting) or afterload (e.g., handgrip), which both increase left ventricular volume to relieve the obstruction. In contrast, the murmur increases with any decrease in preload (e.g., Valsalva, diuretics, nitroglycerin) and/or afterload (e.g., angiotensin-converting enzyme inhibitors, nitroglycerin).

Fifer and Vlahakes reviewed the management of hypertrophic cardiomyopathy. They note that the decrease in afterload with nitroglycerin worsens the left ventricular outflow tract obstruction.

Incorrect Answers:
Answer 1: Disopyramide is a negative inotropic agent that reduces the left ventricular outflow tract gradient in HOCM. Therefore, it would improve the murmur; it is used as a second-line agent for the treatment of HOCM, in combination with a beta blocker or non-dihydropyridine calcium channel blocker.

Answer 2: Metoprolol is a beta adrenergic blocker that reduces left ventricular outflow tract obstruction and is commonly used in the treatment of HOCM. It would improve the murmur of HOCM by relieving the obstruction.

Answer 4: Phenylephrine is an alpha adrenergic agonist that increases afterload. Increases in afterload reduce left ventricular emptying, helping to expand the left ventricle and relieve the left ventricular outflow tract obstruction. It is used in the treatment of hypotension in patients with HOCM and would improve the murmur.

Answer 5: Verapamil is a non-dihydropyridine calcium channel blocker that reduces left ventricular outflow tract obstruction. It is commonly used in the treatment of HOCM. By relieving the obstruction, it would improve the murmur.

Bullet Summary:
Medications that reduce preload and/or afterload worsen the murmur and symptoms of hypertrophic obstructive cardiomyopathy.