What are the treatment guidelines for Hypertrophic Obstructive Cardiomyopathy (HOCM)?

Treatment Guidelines for Hypertrophic Obstructive Cardiomyopathy (HOCM)

Beta-blockers are the first-line treatment for symptomatic patients with HOCM, with a goal of achieving a resting heart rate of less than 60-65 bpm. 1, 2

First-Line Medical Management

• Beta-blocking drugs are recommended as initial therapy for symptomatic patients with both obstructive and nonobstructive HCM (Level of Evidence: B) 2
• Titrate beta-blockers to a resting heart rate of less than 60-65 bpm using maximum tolerated doses 2, 1
• Beta-blockers should be used with caution in patients with sinus bradycardia or severe conduction disease 2
• Beta-blockers have been shown to prevent exercise-induced LVOT obstruction in up to 52% of patients and substantially blunt it in another 33% 3

Second-Line Therapy

• Verapamil (starting at low doses and titrating up to 480 mg/day) is recommended for patients who:
  • Do not respond to beta-blockers 2, 1
  • Have side effects from beta-blockers 2
  • Have contraindications to beta-blockers 2
• Verapamil should be used with extreme caution in patients with:
  • High gradients 2
  • Advanced heart failure 2
  • Sinus bradycardia 2
  • Systemic hypotension 4
  • Severe dyspnea at rest 4

Refractory Symptoms Management

• Disopyramide combined with a beta-blocker or verapamil is reasonable for patients with obstructive HCM who don't respond to first-line therapy 2, 1
• Disopyramide should not be used alone without beta-blockers or verapamil in patients with atrial fibrillation, as it may enhance atrioventricular conduction 2, 1
• Oral diuretics may be added with caution when congestive symptoms persist despite optimal therapy with beta-blockers or verapamil 2, 1

Septal Reduction Therapy

• Septal reduction therapy should be performed only by experienced operators in comprehensive HCM clinical programs 2
• Indications for septal reduction therapy include:
  • Severe drug-refractory symptoms 2
  • LVOT obstruction with gradients ≥50 mm Hg 2
• Two main options for septal reduction therapy:
  • Surgical myectomy - highly effective with >90% relief of obstruction 5
  • Alcohol septal ablation - less invasive alternative with comparable results in selected patients 5
• Consultation with centers experienced in both procedures is reasonable when discussing treatment options 2

Medications to Avoid in HOCM

• Dihydropyridine calcium channel blockers (e.g., nifedipine) are potentially harmful in patients with resting or provocable LVOT obstruction 2, 1
• Vasodilators (ACE inhibitors, ARBs) should be used cautiously or avoided in obstructive HCM 1
• Digitalis is potentially harmful in the treatment of dyspnea in patients with HCM without atrial fibrillation 2
• Dopamine, dobutamine, norepinephrine, and other intravenous positive inotropic drugs are potentially harmful for treating acute hypotension in obstructive HCM 2

Special Considerations

• Intravenous phenylephrine (or another pure vasoconstricting agent) is recommended for acute hypotension in patients with obstructive HCM who don't respond to fluid administration 2
• Low-intensity aerobic exercise is reasonable as part of a healthy lifestyle for HCM patients 2, 1
• Comorbidities that may contribute to cardiovascular disease (hypertension, diabetes, hyperlipidemia, obesity) should be treated according to relevant guidelines 2

Emerging Therapies

• Recent research shows that aficamten (a cardiac myosin inhibitor) as monotherapy is superior to metoprolol in improving peak oxygen uptake, hemodynamics, and symptoms in patients with symptomatic obstructive HCM 6
• Mavacamten, another myosin inhibitor approved in Germany in 2023, has been shown to lower LVOT gradient and improve quality of life, though in 7-10% of patients there is a reversible reduction of left ventricular ejection fraction to less than 50% 7

Important Pitfalls to Avoid

• Septal reduction therapy should not be performed in asymptomatic patients with normal exercise capacity, regardless of gradient severity 1
• Verapamil should not be used in patients with obstructive HCM who have systemic hypotension or severe dyspnea at rest 2, 4
• Avoid administering beta-blocking drugs with either verapamil or diltiazem due to potential for high-grade atrioventricular block 2