Non-Vasodilating Beta Blockers for Hypertrophic Obstructive Cardiomyopathy (HOCM)
Nonvasodilating beta blockers are the first-line pharmacological therapy for patients with symptomatic obstructive hypertrophic cardiomyopathy (HOCM) and should be titrated to effectiveness or maximally tolerated doses. 1
Specific Non-Vasodilating Beta Blockers for HOCM
The following beta blockers are considered non-vasodilating and appropriate for HOCM management:
- Metoprolol - Cardioselective beta-1 blocker
- Atenolol - Cardioselective beta-1 blocker
- Nadolol - Non-selective beta blocker
- Propranolol - Non-selective beta blocker
- Bisoprolol - Highly selective beta-1 blocker
Mechanism of Action in HOCM
Non-vasodilating beta blockers work in HOCM by:
- Decreasing heart rate and contractility
- Reducing early LV ejection acceleration
- Decreasing systolic pushing force on mitral leaflets
- Allowing more time for ventricular filling
- Preventing exercise-induced LVOT obstruction
Dosing and Titration
- Start with low doses and gradually increase
- Target a resting heart rate between 50-60 beats per minute 2
- Titrate to maximally tolerated doses or until symptoms improve
- Continue until there is demonstrated physiologic evidence of beta-blockade (suppression of resting heart rate) 1
Clinical Evidence
Beta blockers have been shown to:
- Prevent development of LVOT obstruction during exercise 3
- Reduce postexercise LVOT gradient from 87 ± 29 mm Hg to 36 ± 22 mm Hg (p <0.001) 3
- Abolish or substantially blunt exercise-induced obstruction in 85% of patients 3
When Beta Blockers Are Ineffective
If beta blockers fail to control symptoms:
- Ensure adequate dosing with physiologic evidence of beta blockade
- Consider substitution with non-dihydropyridine calcium channel blockers (verapamil, diltiazem) 1
- For persistent symptoms, consider adding:
- Myosin inhibitors (adult patients only)
- Disopyramide (in combination with beta blockers)
- Septal reduction therapy at experienced centers 1
Important Cautions and Contraindications
Use beta blockers with caution in patients with:
- Sinus bradycardia
- Severe conduction disease
- Bronchospastic disease
Avoid vasodilating beta blockers (e.g., carvedilol, nebivolol) as they may worsen LVOT obstruction
Discontinue vasodilators that may worsen LVOT obstruction:
- Angiotensin-converting enzyme inhibitors
- Angiotensin receptor blockers
- Dihydropyridine calcium channel blockers
- Digoxin 1
Special Populations
Children and adolescents: Beta blockers can be used but monitor for side effects including depression, fatigue, and impaired scholastic performance 1
Patients with high BMI: May have reduced response to beta blockers (hazard ratio 2.03/1 kg/m², 95% CI 1.2 to 3.4) 3
Comparative Efficacy
In head-to-head comparisons:
- Disopyramide > beta blockers > verapamil for lowering gradient 4
- No significant differences in long-term outcomes between beta blockers and verapamil in low-risk patients with HCM 5
Beta blockers remain the cornerstone of pharmacological management for HOCM symptoms due to their effectiveness, safety profile, and extensive clinical experience.