Review Question - QID 217181

This young man presents with syncope during strenuous activity, ECG evidence of left ventricular hypertrophy, and a systolic murmur that reduces with passive leg raise (which increases preload), in addition to a family history of sudden cardiac death, suggesting a diagnosis of hypertrophic obstructive cardiomyopathy (HOCM). First line treatment for HOCM is a beta-blocker.

Hypertrophic obstructive cardiomyopathy is an autosomal dominant disease characterized by disorganized myocardial muscle fibers, resulting in structural abnormalities including asymmetric thickening of the interventricular septum and subsequent systolic anterior motion of the mitral valve. During strenuous activity or in states of dehydration, left ventricular outflow tract obstruction worsens and can precipitate lightheadedness, syncope, or fatal dysrhythmias causing sudden cardiac death. Physical exam may reveal a systolic crescendo-decrescendo cardiac murmur that improves when preload is increased (such as with passive leg raise or fluid administration) or afterload is increased (such as with handgrip). The diagnosis is made with the clinical presentation in combination with echocardiographic findings of ventricular hypertrophy. Treatment consists of proper hydration and a negative inotropic agent such as a beta-blocker.

Veselka et al. review the epidemiology, pathophysiology, clinical presentation, and treatment of HOCM. The authors highlight the dangers associated with verapamil, a calcium channel blocker, which can paradoxically worsen left ventricular obstruction due to its vasodilatory effects. Beta-blockers do not share this risk and thus are preferred as the first-line negative inotropic agent in treating HOCM.

Incorrect Answers:
Answer 2: Calcium channel blockers such as verapamil are negative inotropic agents commonly used in the treatment of hypertension, atrial fibrillation, and even HOCM. However, due to the potential for side effects such as AV block, calcium channel blockers are reserved for patients with contraindications to beta-blockers or who are refractory to beta-blocker therapy.

Answer 3: Furosemide is a loop diuretic that can be used to reduce symptoms in heart failure. Heart failure would present with dyspnea on exertion, jugular venous distension, pulmonary crackles and wheezes, and lower extremity edema. It would reduce preload in HOCM and worsen symptoms.

Answer 4: Implantable cardioverter-defibrillator (ICD) placement is primarily indicated in patients at high-risk for sudden cardiac death despite optimal medical management. Although this patient has an increased risk of sudden cardiac death due to his diagnosis of HOCM and family history, the first step in management is to initiate appropriate medical therapy with a beta-blocker. This would be an appropriate intervention subsequently for this patient.

Answer 5: Surgical septal myectomy is an invasive procedure indicated for patients with HOCM who continue to have symptoms of heart failure or recurrent episodes of syncope despite optimal medical therapy. It is not a first-line treatment.

Bullet Summary:
The first-line treatment for hypertrophic obstructive cardiomyopathy is proper hydration and a beta blocker.