Cardioversion is treatment for an irregular heartbeat, called arrhythmia. Arrhythmias happen when the delicate internal electrical system of the heart stops working correctly. For example, in atrial fibrillation the heart muscle makes short, fast, quivering movements instead of contracting. When the heart beats out of rhythm, it does not pump blood effectively, which can be dangerous. Cardioversion restores a normal heartbeat using electrical stimulation or medications.
When electrical stimulation is delivered from outside the body, the procedure is called external cardioversion. External cardioversion is performed when a person’s heart is beating so poorly that serious damage is likely to occur without intervention. It may be done as either an elective procedure or in an emergency situation. If done as an elective procedure, the patient would receive the treatment during a scheduled appointment with his or her physician. The patient is given blood thinners to reduce the risk of blood clots, as well as sedatives to help keep him or her comfortable. Two electrical paddles or electrode patches are applied to the chest, and sometimes also to the back. A quick electrical shock is applied, which resets the beating of the heart. It may take more than one shock. The whole procedure takes less than 30 minutes, and recovery is quick. The heart is carefully monitored for the next 24 – 48 hours to make sure it is beating correctly.
Electrical stimulation may also be delivered from inside the heart. This type of treatment is called internal cardioversion. During internal cardioversion, the shock is given via catheter, or a thin, flexible tube, that is inserted in a vein in the leg and threaded to the heart. The patient is asleep during the procedure. The electrical shock from internal cardioversion is much smaller compared to the shock from external cardioversion.
Cardioversion may also be administered in the form of medications, called anti-arrhythmics. These medications alter the flow of electricity through the heart, which can help it contract effectively. Anti-arrhythmics may be given by mouth at home or through an IV in the hospital. In both cases, the heart is carefully monitored to make sure the treatment is working.
If cardioversion is unsuccessful, an implantable device such as a pacemaker or ICD may be used. These small devices are placed under the skin of the chest, and they use a battery and small wires to keep the heart beating on time.