What is the initial management for Hypertrophic Cardiomyopathy (HCM)?

Initial Management for Hypertrophic Cardiomyopathy (HCM)

Nonvasodilating beta blockers are the first-line therapy for symptomatic patients with obstructive HCM, titrated to effectiveness or maximally tolerated doses. 1

Diagnostic Approach and Classification

Before initiating treatment, it's essential to determine whether the patient has obstructive or non-obstructive HCM:

• Obstructive HCM: Left ventricular outflow tract obstruction (LVOTO) with gradient ≥30 mm Hg at rest or with provocation
• Non-obstructive HCM: LVOTO gradient <30 mm Hg

Approximately 2/3 of HCM patients have obstructive physiology, which is a frequent cause of limiting symptoms 2.

Management Algorithm for Obstructive HCM

First-Line Therapy

• Beta blockers (non-vasodilating)
  • Titrate to achieve resting heart rate between 50-60 beats per minute
  • Continue until demonstrated physiologic evidence of beta-blockade is observed
  • Primary mechanism: Decrease heart rate, improve diastolic filling, reduce myocardial oxygen demand 1

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

• Non-dihydropyridine calcium channel blockers:
  • Verapamil or diltiazem
  • Important caution: Verapamil is potentially harmful in patients with:
    • Severe dyspnea at rest
    • Hypotension
    • Very high resting gradients (>100 mm Hg)
    • Children <6 weeks of age 1, 3

Third-Line Therapy (if symptoms persist despite first/second-line)

• Add one of the following:
  1. Myosin inhibitor (mavacamten) - adult patients only
  2. Disopyramide (must be combined with an AV nodal blocking agent)
  3. Septal reduction therapy (at experienced centers) 1

Additional Important Interventions

• Discontinue medications that may worsen LVOTO:

  • Vasodilators (ACE inhibitors, ARBs)
  • Dihydropyridine calcium channel blockers
  • Digoxin
  • High-dose diuretics 1

• For volume overload with persistent dyspnea:

  • Consider cautious use of low-dose oral diuretics 1

Management of Acute Situations

• For acute hypotension:
  • Intravenous phenylephrine or other vasoconstrictors without inotropic activity
  • Can be combined with beta blockers
  • Focus on maximizing preload and afterload while avoiding increases in contractility 1

Management of Non-obstructive HCM

• Beta blockers or calcium channel blockers may be used for symptom control, though evidence is less robust
• For younger patients (≤45 years) with pathogenic sarcomere variants and mild phenotype, valsartan may help slow adverse cardiac remodeling 1

Special Considerations and Pitfalls

Medication Cautions

1. Verapamil risks: Can cause severe hypotension, pulmonary edema, and sinus bradycardia in patients with severe obstruction 3

2. Disopyramide: Can enhance conduction through AV node, potentially leading to rapid conduction with onset of atrial fibrillation - always combine with beta blocker, verapamil, or diltiazem 1

3. Mavacamten: Requires risk evaluation and mitigation strategy due to potential decrease in LVEF <50% in 5.7-10% of patients; must be discontinued if persistent systolic dysfunction develops 1

4. Combination therapy: Using calcium channel blockers with beta blockers specifically for HCM management is not supported by evidence, though may be appropriate for managing concomitant hypertension 1

Monitoring Recommendations

• Regular assessment of symptom response rather than measured gradient (outflow obstruction varies throughout daily life)
• Liver function monitoring with verapamil due to risk of hepatocellular injury 3
• LVEF monitoring with mavacamten therapy

By following this structured approach to initial management, most patients with HCM can achieve significant symptom improvement and maintain good quality of life.