What is the management of Hypertrophic Obstructive Cardiomyopathy (HOCM)?

Management of Hypertrophic Obstructive Cardiomyopathy (HOCM)

Nonvasodilating beta blockers are the first-line therapy for symptomatic patients with HOCM, followed by calcium channel blockers if beta blockers are ineffective, and then advanced therapies including cardiac myosin inhibitors, disopyramide, or septal reduction therapy for persistent symptoms. 1

Pharmacological Management Algorithm

First-Line Therapy

• Beta blockers (metoprolol, bisoprolol, or propranolol)
  • Target resting heart rate <60-65 bpm
  • Titrate to dose where symptom benefit is observed
  • Do not declare failure until physiologic evidence of beta-blockade is demonstrated 1
  • Recent evidence suggests cardiac myosin inhibitors like aficamten may be superior to beta blockers as monotherapy 2

Second-Line Therapy (if beta blockers ineffective or not tolerated)

• Non-dihydropyridine calcium channel blockers (verapamil or diltiazem)
  • Start at low dose and titrate up to 480 mg/day for verapamil 3
  • Caution: Avoid in patients with severe dyspnea at rest, hypotension, very high resting gradients (>100 mm Hg), and children <6 weeks of age 1

Advanced Therapies (for persistent symptoms)

1. Cardiac myosin inhibitors (mavacamten, aficamten) in adult patients

   • Improves LVOT gradients, symptoms, and functional capacity in 30-60% of patients
   • Requires risk evaluation and mitigation strategy due to potential decrease in LVEF <50% 1

2. Disopyramide

   • Must be used in combination with beta blocker or calcium channel blocker
   • Caution: Can enhance conduction through AV node, potentially leading to rapid conduction with AF 1

3. Septal Reduction Therapy (SRT) at experienced centers

   • Surgical myectomy or alcohol septal ablation
   • Indicated when symptoms persist despite optimal medical therapy
   • Should be performed at comprehensive HCM centers with demonstrated excellence 1, 4

Special Clinical Scenarios

Acute Hypotension in HOCM

• Medical urgency requiring immediate intervention
• Treatment approach:
  • Maximize preload and afterload
  • Avoid increases in contractility or heart rate
  • Administer IV vasoconstrictors (phenylephrine)
  • Consider beta-blockade in combination with vasoconstrictors 1, 3

Volume Overload/Congestion

• Cautious use of low-dose diuretics if signs of congestion persist despite optimal therapy
• Warning: Aggressive diuresis can worsen LVOT obstruction by decreasing preload 1, 3

Concomitant Conditions

• Avoid medications that may worsen LVOTO:
  • Pure vasodilators (dihydropyridine calcium channel blockers, ACE inhibitors, ARBs)
  • High-dose diuretics
  • Digoxin 1

Monitoring Recommendations

• Transthoracic echocardiogram every 1-2 years to assess:
  • Degree of myocardial hypertrophy
  • Dynamic LVOT obstruction
  • Mitral regurgitation
  • Myocardial function 3
• 12-lead ECG and 24-48 hour ambulatory monitoring in initial evaluation and every 1-2 years 3

Important Pitfalls to Avoid

1. Do not use verapamil in patients with severe obstruction, advanced heart failure, or high resting gradients (>100 mm Hg)
2. Do not use disopyramide alone in patients with atrial fibrillation
3. Do not use high-dose diuretics in any patient with HOCM
4. Do not declare beta blocker failure until physiologic evidence of beta-blockade is demonstrated
5. Do not perform septal reduction therapy in asymptomatic patients with normal exercise capacity 1

Emerging Therapies

Recent research shows cardiac myosin inhibitors like aficamten may be superior to traditional beta blockers in improving peak oxygen uptake, hemodynamics, and symptoms in patients with obstructive HCM 2, 5. This represents a potentially significant advancement in HOCM management that may alter the treatment algorithm in the future.