In Hypertrophic Obstructive Cardiomyopathy (HOCM), which medication is more important, Angiotensin Receptor Blockers (ARBs) or beta blockers?

Beta-Blockers Are More Important Than ARBs in HOCM

Beta-blockers are the first-line and most important medication for HOCM, while ARBs are contraindicated and should be discontinued in patients with obstructive disease. 1, 2

Why Beta-Blockers Are Essential

Non-vasodilating beta-blockers are considered first-line therapy for symptomatic obstructive HCM and should be titrated to achieve physiologic beta-blockade (resting heart rate suppression). 1

The beneficial effects of beta-blockers work through multiple mechanisms:

• Decrease heart rate, prolonging diastole and improving passive ventricular filling 1
• Reduce LV contractility and myocardial oxygen demand 1
• Prevent exercise-induced LVOT obstruction—beta-blockers can abolish or substantially reduce post-exercise gradients in 85% of patients 3
• Particularly effective for patients with outflow gradients present only with exertion 1

Why ARBs Are Contraindicated

ARBs must be discontinued in HOCM because their vasodilatory effects worsen LVOT obstruction, exacerbate symptoms, and can precipitate hemodynamic collapse. 1, 2

The mechanism of harm is clear:

• ARBs decrease systemic vascular resistance, reducing the afterload that normally opposes the outflow gradient, thereby worsening the pressure gradient across the LVOT 2
• They allow more vigorous ejection into a dilated arterial system, exacerbating angina and dyspnea 2
• The ACC/AHA guidelines explicitly recommend discontinuation of vasodilators including ARBs as they worsen symptoms from dynamic obstruction 1, 2

Treatment Algorithm for HOCM

Step 1: Eliminate Harmful Medications

Immediately discontinue ARBs, ACE inhibitors, dihydropyridine calcium channel blockers, and high-dose diuretics if LVOT gradient ≥30 mmHg is confirmed. 1, 2

Step 2: Initiate First-Line Therapy

Start non-vasodilating beta-blockers (propranolol, atenolol, metoprolol, or nadolol) and titrate to target resting heart rate <60-65 bpm. 1, 2

Step 3: Alternative First-Line Options

If beta-blockers fail or are not tolerated (e.g., asthma), use verapamil or diltiazem (non-dihydropyridine calcium channel blockers) up to 480 mg/day. 1

Critical caveat: Exercise extreme caution with verapamil in patients with very high resting gradients (>80-100 mmHg) and severe symptoms, as vasodilating properties can cause pulmonary edema and cardiogenic shock. 1

Step 4: Second-Line Therapies

For patients who remain symptomatic despite optimal first-line therapy, escalate to mavacamten (cardiac myosin inhibitor), disopyramide, or septal reduction therapy. 1, 4

Critical Pitfalls to Avoid

Do not continue ARBs "for renal protection" or concurrent hypertension in obstructive HOCM—the risk of worsening LVOT obstruction outweighs theoretical benefits. 2

Do not combine beta-blockers with verapamil/diltiazem for HCM-directed therapy, as there is no evidence this is more advantageous than either drug alone. 1

Do not declare beta-blocker failure until achieving physiologic evidence of beta-blockade (suppressed resting heart rate)—inadequate dosing is a common error. 1

Important Exception

ARBs may be used only in non-obstructive HCM with systolic dysfunction (LVEF <50%) and loss of obstruction, where guideline-directed HFrEF therapy is appropriate. 2