There are many causes of abnormal heart rhythms (arrhythmias). Some arrhythmias are harmless and do not need treatment. Sometimes arrhythmias stop on their own or with changes in lifestyle, such as avoiding alcohol, caffeine (in beverages and foods), and smoking. Other arrhythmias are dangerous or bothersome enough to need treatment. Antiarrhythmic drugs are one type of treatment. Other treatments for arrhythmias include insertion of a pacemaker or an implantable cardioverter-defibrillator (ICD), cardioversion-defibrillation, or destruction of a small area of heart tissue that is responsible for the arrhythmia (ablation).
Antiarrhythmic drugs are useful for suppressing fast arrhythmias that cause intolerable symptoms or pose a risk. No single drug suppresses all arrhythmias in all people. Sometimes several drugs must be tried until the response is satisfactory. Sometimes antiarrhythmic drugs can worsen or even cause arrhythmias. This effect is called proarrhythmia. Antiarrhythmic drugs may also cause other side effects.
There are many different antiarrhythmic drugs, which are divided into groups based on how they work. The main groups include beta-blockers, calcium channel blockers, potassium channel blockers, and sodium channel blockers.
Beta-blockers block the effects of the hormone epinephrine (adrenaline). In the heart, this blockade slows the natural pacemaker activity of heart cells and slows conduction of impulses through the heart's normal electrical pathways.
Calcium, potassium, and sodium are electrolytes that flow in and out of heart cells and are responsible for the heart's normal electrical activity. These electrolytes flow through the walls of heart cells through microscopic pores called channels. There are separate channels for each electrolyte. Blocking one of these channels can slow conduction through the heart's electrical system and/or decrease the natural pacemaker activity of heart cells.
