What is the management plan for a patient with hypertrophic cardiomyopathy (HCM) and significant left ventricular outflow tract obstruction?

Management of Hypertrophic Cardiomyopathy with Left Ventricular Outflow Tract Obstruction

Beta blockers should be initiated as first-line therapy for this patient with hypertrophic cardiomyopathy, significant left ventricular outflow tract gradient, septal hypertrophy, and mitral regurgitation. 1

Initial Pharmacological Management

First-Line Therapy

• Beta blockers (Class 1, Level B-R recommendation)
  • Mechanism: Negative inotropic effects reduce contractility and attenuate adrenergic-induced tachycardia
  • Prolongs diastolic filling period, improving diastolic function
  • Titrate to achieve physiologic evidence of beta-blockade (suppression of resting heart rate)
  • Continue until symptom benefit is observed 1

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

• Non-dihydropyridine calcium channel blockers (Class 1, Level B-R recommendation)
  • Options: Verapamil or diltiazem
  • Mechanism: Similar negative inotropic and chronotropic effects as beta blockers
  • Caution: Avoid in patients with severe resting gradients (>100 mm Hg), elevated pulmonary pressures, or hypotension 1

Advanced Management for Persistent Symptoms

If symptoms persist despite optimal first-line therapy:

Pharmacological Options

• Add myosin inhibitor (mavacamten) in adult patients (Class 1, Level B-R recommendation)

  • Recently approved medication that directly addresses the pathophysiology
  • Improves LVOT gradients, symptoms, and functional capacity in 30-60% of patients
  • Requires monitoring due to risk of decreased LVEF in 5.7-10% of patients 1

• Add disopyramide (with AV nodal blocking agent) (Class 1, Level B-R recommendation)

  • Can provide symptomatic benefit in patients who failed first-line therapy
  • Must be combined with beta blocker or calcium channel blocker 1

Invasive Options

• Septal reduction therapy (SRT) (Class 1, Level B-R recommendation)
  • Consider when symptoms persist despite optimal medical therapy
  • Options include:
    1. Surgical septal myectomy (preferred for younger patients, those with greater septal thickness)
    2. Alcohol septal ablation (alternative for patients with comorbidities or advanced age)
  • Should be performed at experienced centers with demonstrated excellence in these procedures 1, 2

Management of Mitral Regurgitation

• Mitral regurgitation in HCM is typically secondary to LVOT obstruction causing systolic anterior motion of the mitral valve
• Primary approach is to treat the underlying LVOT obstruction with the therapies outlined above
• In cases where mitral regurgitation persists despite LVOT gradient reduction, mitral valve repair or replacement may be considered during surgical myectomy 3, 4

Additional Management Considerations

Medications to Avoid

• Discontinue vasodilators (ACE inhibitors, ARBs, dihydropyridine calcium channel blockers)
• Avoid digoxin due to positive inotropic effects
• Avoid high-dose diuretics which can worsen LVOT obstruction 1, 2

Cautious Use

• Low-dose diuretics may be considered in patients with persistent dyspnea and evidence of volume overload (Class 2b, Level C-EO) 1

Acute Management

• For acute hypotension: IV phenylephrine or other vasoconstrictors without inotropic activity (Class 1, Level C-LD)
• Avoid inotropic agents which can worsen obstruction 1

Monitoring and Follow-up

• Assess symptom response rather than measured gradient to determine medication effectiveness
• Echocardiography to monitor LVOT gradient, mitral regurgitation, and ventricular function
• Exercise stress testing to evaluate exercise tolerance and provocable obstruction 1, 2

Pitfalls to Avoid

1. Failing to recognize that LVOT obstruction is dynamic and may only be evident with provocation in some patients 5
2. Underestimating the importance of volume status - hypovolemia can significantly worsen LVOT obstruction 6
3. Using vasodilators or positive inotropic agents which can exacerbate obstruction 1, 2
4. Delaying referral to specialized HCM centers for patients with refractory symptoms who may benefit from advanced therapies 1