Medication Summary
Beta-blockers and calcium channel blockers are used to treat children with hypertrophic cardiomyopathy (HCM). In individuals with significant tachyarrhythmias, amiodarone and other class III-type antiarrhythmic agents have also been used.
Beta-Adrenergic Blocking Agents
Class Summary
Beta-blockers may decrease outflow obstruction and increase ventricular compliance. No clear evidence indicates that they decrease sudden death. Approximately one half of patients who use beta-blockers feel improvement in symptoms.
Propranolol (Inderal LA)
Propranolol is a nonselective beta-blocker with a long record of use and relative safety. The treatment dose is titrated to produce clinical effect (ie, a reduction in perceived symptoms). Blunting of the maximal heart rate during exercise testing is a good marker for beta-blocker effect. Although propranolol is generally a short-acting agent, long-acting preparations are available. A stable liquid preparation is available and can be used to treat infants.
Atenolol (Tenormin)
Atenolol selectively blocks beta1 receptors, with little or no effect on beta2 types. It may be better tolerated than propranolol (it has more favorable pharmacokinetics and frequently has equivalent efficacy).
Calcium Channel Blockers
Class Summary
Calcium channel blockers are an alternative to beta-blockers. They improve diastolic filling by improving diastolic relaxation and decreasing outflow gradient due to depression of cardiac contractility.
Verapamil (Calan, Isoptin, Verelan)
During depolarization, verapamil inhibits calcium ion from entering slow channels or voltage-sensitive areas of the vascular smooth muscle and myocardium. It may have a better effect on exercise performance. Sustained release formulations with daily dosing are available.
Antiarrhythmics, Miscellaneous
Class Summary
Amiodarone is categorized as a class III antiarrhythmic agent but has antiarrhythmic effects that overlap all 4 Vaughn-Williams antiarrhythmic classes. Its use is generally reserved for potentially life-threatening ventricular arrhythmias.
Amiodarone (Cordarone, Pacerone)
Amiodarone is a complex and potent antiarrhythmic agent with multiple effects on cardiac action potential, exceedingly complex pharmacokinetics, and extracardiac pharmacodynamics. Oral efficacy may take weeks. With the exception of disorders of prolonged repolarization (eg, long QT syndrome), amiodarone may be the drug of choice for life-threatening ventricular arrhythmias refractory to beta-blockade and initial therapy with other agents.
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