What is the role of terazosin or amlodipine (calcium channel blocker) in the management of Hypertrophic Cardiomyopathy (HCM)?

Terazosin and Amlodipine in HCM: Avoid Both

Amlodipine (a dihydropyridine calcium channel blocker) is potentially harmful in HCM patients with resting or provocable left ventricular outflow tract (LVOT) obstruction and should not be used. 1 Terazosin (an alpha-blocker) is similarly contraindicated as it causes vasodilation that can worsen LVOT obstruction and precipitate hemodynamic collapse. 1

Why These Agents Are Harmful

Dihydropyridine Calcium Channel Blockers (Amlodipine)

• Class III: Harm recommendation from ACC/AHA guidelines explicitly states that nifedipine and other dihydropyridine calcium channel blockers are potentially harmful for treating symptoms in HCM patients with resting or provocable LVOT obstruction. 1
• These agents cause peripheral vasodilation, which reduces afterload and can paradoxically worsen LVOT gradients, leading to increased obstruction and symptoms. 1
• The vasodilatory effect can precipitate syncope, hypotension, and acute decompensation in obstructive HCM. 1

Alpha-Blockers (Terazosin)

• Terazosin causes vasodilation through alpha-1 receptor blockade, similar to the mechanism that makes dihydropyridines harmful. 1
• In acute hypotension with obstructive HCM, guidelines specifically recommend pure vasoconstrictors (phenylephrine), not vasodilators, highlighting the danger of agents like terazosin. 1
• Vasodilating agents reduce systemic vascular resistance, which worsens the dynamic LVOT gradient and can trigger cardiovascular collapse. 1

Appropriate Calcium Channel Blocker Use in HCM

Non-Dihydropyridine Calcium Channel Blockers Are Safe

• Verapamil and diltiazem (non-dihydropyridines) are Class I recommended alternatives when beta-blockers fail or are contraindicated. 1
• These agents work through negative chronotropy and inotropy rather than vasodilation, slowing heart rate, improving diastolic filling, and reducing myocardial oxygen demand. 1
• Verapamil can be titrated up to 480 mg/day for symptom control in both obstructive and nonobstructive HCM. 1

Critical Verapamil Precautions

• Use verapamil with extreme caution in patients with high LVOT gradients, advanced heart failure, or systemic hypotension. 1
• Verapamil is potentially harmful (Class III: Harm) in obstructive HCM patients with systemic hypotension or severe dyspnea at rest. 1
• Monitor for bradycardia and atrioventricular conduction block, especially when combining with beta-blockers. 1

Evidence-Based Treatment Algorithm for HCM

First-Line Therapy

• Beta-blockers are the primary first-line agents for symptomatic HCM (both obstructive and nonobstructive), titrated to resting heart rate <60-65 bpm. 1
• Beta-blockers should be the primary therapy in neonates and children. 1

Second-Line Therapy

• Verapamil or diltiazem (non-dihydropyridines only) when beta-blockers are ineffective, not tolerated, or contraindicated. 1
• Recent real-world data from 600 HCM patients showed no significant difference in adverse cardiovascular outcomes between beta-blocker and verapamil therapy over median 3.9-year follow-up. 2

Third-Line Options for Persistent Symptoms

• Mavacamten (cardiac myosin inhibitor) for adults with persistent NYHA class II-III symptoms despite beta-blockers or calcium channel blockers (Class I recommendation). 1, 3
• Disopyramide combined with beta-blocker or verapamil for obstructive HCM with persistent symptoms. 1
• Septal reduction therapy at experienced centers for severe drug-refractory symptoms with LVOT obstruction. 1

Management of Hypertension in HCM Patients

• When HCM patients require antihypertensive therapy, prefer beta-blockers and non-dihydropyridine calcium channel blockers in those with obstructive physiology. 1
• ACE inhibitors and ARBs have uncertain benefit and are potentially harmful in patients with resting or provocable LVOT obstruction. 1
• A 12-month trial of losartan versus placebo in 124 HCM patients showed no benefit on LV mass, fibrosis, or functional class, though it was not harmful. 1

Common Pitfalls to Avoid

• Never prescribe dihydropyridine calcium channel blockers (amlodipine, nifedipine, felodipine) for HCM patients, especially those with obstruction. 1
• Avoid all vasodilators including alpha-blockers (terazosin, doxazosin), nitrates, and hydralazine in obstructive HCM. 1
• Do not confuse verapamil/diltiazem (safe) with dihydropyridines (harmful)—they have fundamentally different mechanisms and effects in HCM. 1
• In acute hypotension with obstructive HCM, use phenylephrine (pure vasoconstrictor), never vasodilators or inotropes like dopamine or dobutamine. 1