Four types of medications can be used to treat arrhythmias, or abnormal heart rhythms. Which ones are prescribed for you depends on whether your disorder originates in the atrium or ventricles of the heart, as well as the characteristics and severity of the rhythm disturbance.
How Antiarrhythmics Work
All antiarrhythmics act on the heart’s ion channels, in which electrically charged molecules—sodium, potassium, magnesium and calcium—travel to stimulate the heart’s contractions. Each class of antiarrhythmics works in a different way. Many of the medications used to treat arrhythmias are also used to treat other cardiovascular conditions, including high blood pressure and heart failure.
Class I Antiarrhythmics
Class I antiarrhythmics block sodium ion channels, decreasing the rate at which the electrical signal travels from cell to cell in the heart muscle. There are three sub-classes, each of which works slightly differently.
- Class IA antiarrhythmics may be prescribed for supraventricular arrhythmias, which originate above the ventricle. They prolong the length of time it takes to “recharge” the heart after every beat. They include quinidine, procainamide and disopyramide.
- Class IB antiarrhythmics have the same effect as Class IA drugs, but are used primarily for ventricular arrhythmias. They include lignocaine, mixelitine and phenytoin.
- Flecainide, a class IC antiarrhythmic, slows nerve conductivity in the heart and is used primarily for atrial fibrillation and other supraventricular arrhythmias.
Class II Antiarrhythmics
These drugs, beta-blockers, are widely used to treat hypertension and angina, to prevent bleeding in people with liver disease, and to prevent complications from coronary artery bypass surgery. They regulate heartbeat by slowing the response to certain nerve impulses. They include propranolol and metoprolol.
Class III Antiarrhythmics
Probably the most successful in treating arrhythmias, class III medications lengthen recharge time without affecting the heart’s normal electrical conduction. They act in both the upper and lower chambers of the heart. This class includes amiodarone.
Class IV Antiarrhythmics
These medications, verapamil and diltiazem, are calcium channel blockers and are often used to treat high blood pressure. They work by dilating blood vessels and decreasing the heart’s pumping strength.
Special Considerations for Women
Tamoxifen, as well as some drugs to treat migraine and depression, when used in conjunction with amiodarone, may cause life-threatening rhythm disturbances. Be sure to give your doctor a list of all the medications you are taking.
Date Last Modified: January 21, 2011
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