What is the optimal rate control strategy in patients with Hypertrophic Obstructive Cardiomyopathy (HOCM)?

From the Guidelines

Rate control in patients with hypertrophic obstructive cardiomyopathy (HOCM) should focus on beta-blockers as first-line therapy. Metoprolol (25-200 mg twice daily), atenolol (25-100 mg daily), or bisoprolol (2.5-10 mg daily) are preferred options due to their ability to slow heart rate, reduce myocardial oxygen demand, and decrease left ventricular outflow tract (LVOT) obstruction, as recommended by the 2014 AHA/ACC/HRS guideline for the management of patients with atrial fibrillation 1. These medications improve diastolic filling time and reduce symptoms like dyspnea, chest pain, and syncope. Non-dihydropyridine calcium channel blockers such as verapamil (120-480 mg daily in divided doses) or diltiazem (120-360 mg daily in divided doses) can be used as alternatives in patients who cannot tolerate beta-blockers, as stated in the executive summary of the 2014 AHA/ACC/HRS guideline 1. However, they should be used cautiously in severe LVOT obstruction due to their vasodilatory effects. Disopyramide (100-300 mg twice daily) may be added in refractory cases for its negative inotropic effect, as suggested by the guideline 1. Importantly, avoid digoxin, dihydropyridine calcium channel blockers, and vasodilators as they can worsen LVOT obstruction. Regular monitoring of heart rate (target 60-70 bpm), blood pressure, and symptoms is essential, with dose adjustments as needed. In patients with atrial fibrillation and HOCM, rhythm control strategies may be preferable to rate control alone, considering the potential benefits of antiarrhythmic medications and catheter ablation, as mentioned in the guideline 1.

Some key points to consider in the management of HOCM include:

• The use of beta-blockers as first-line therapy for rate control
• The cautious use of non-dihydropyridine calcium channel blockers in patients with severe LVOT obstruction
• The potential benefits of disopyramide in refractory cases
• The importance of regular monitoring and dose adjustments to achieve optimal rate control
• The consideration of rhythm control strategies in patients with atrial fibrillation and HOCM.

It is essential to prioritize the patient's individual needs and clinical presentation when making treatment decisions, and to consult the relevant guidelines and evidence-based recommendations, such as those provided by the 2014 AHA/ACC/HRS guideline 1.

From the Research

Rate Control in Patients with HOCM

• The treatment of symptomatic patients with high LVOT gradients (≥ 50 mm Hg) is pharmacotherapy with nonvasodilating beta-blockers or non-dihydropyridine-type calcium channel antagonists 2.
• Beta-blockers alleviate dyspnea and improve patients' quality of life, while verapamil can increase physical resilience 2.
• Mavacamten, a myosin inhibitor, is a further option that lowers the LVOT gradient and improves quality of life 2.
• In patients with HOCM, management encompasses activity restriction, prevention of sudden cardiac death, control of symptoms, and screening of relatives 3.
• Pharmacologic treatment of symptoms in patients with HOCM consists of negative inotropic drugs, namely beta blockers, and disopyramide; a nondihydropyridine calcium channel blocker (CCB), usually verapamil, may be used in patients with noncardiac side-effects of beta blockers 3.

Comparison of Beta Blockers and Verapamil

• A study found no significant differences in the primary end point (cardiovascular death, hospitalization for heart failure, and hospitalization for atrial fibrillation) between patients treated with beta blockers and verapamil 4.
• Another study found that metoprolol was effective in reducing LVOT and improving the quality of life in patients, while verapamil showed variable effects on both exercise capacity and baseline hemodynamics 5.
• Verapamil therapy was not associated with a higher incidence of adverse events than β-blocker therapy in a real-world cohort of low-risk patients with HCM 4.

Alternative Treatment Options

• Dual-chamber pacing has been introduced as an alternative treatment option for symptomatic patients with HOCM who fail to respond to medical therapy 6.
• Placement of a permanent DDD pacemaker decreased the left ventricular outflow tract gradient and improved functional status in selected patients with symptomatic HOCM 6.
• Septal reduction treatments, such as septal myectomy or alcohol septal ablation, can be considered if drug therapy fails 2, 3.