UW Health Heart, Vascular and Thoracic Care specialists in Madison, Wisconsin, perform cardioversion, a brief procedure in which in a synchronized electric shock is delivered to the heart to convert an abnormal rhythm back to normal.
Most elective or "non-emergency" cardioversions are performed to treat atrial fibrillation or atrial flutter, which are benign rhythm disturbances that originate in the upper chambers (atria) of the heart. In emergency situations, cardioversion can be used to correct a rapid abnormal rhythm associated with faintness, low blood pressure, chest pain, difficulty breathing or loss of consciousness.
These abnormal rhythms represent circular electrical currents that keep the heart muscle, or parts of it, twitching in an uncoordinated fashion. In patients with atrial fibrillation, the atria quiver due to chaotic electrical signals that circulate throughout both upper chambers of the heart. This typically results in a fast and irregular heartbeat.
The electric shock administered in cardioversion stops the current from circling and allows the natural pacemaker (the sinus node) to take over. Medications are often given before the procedure to increase the likelihood of maintaining sinus rhythm.
There are two types of cardioversion:
- Chemical cardioversion: This type of cardioversion involves the use of antiarrhythmia medications to restore the heart's normal rhythm. The medications work by modifying the heart's electrical properties to reduce the frequency of the abnormal rhythms and to help restore normalcy.
- Electrical cardioversion: Also known as "direct-current" or DC cardioversion, electrical cardioversion involves a perfectly timed electric shock that is delivered through the chest wall to the heart. The shock is delivered through the chest and back using special electrodes or paddles that are connected to an external defibrillator by a cable. The shock causes all the heart cells to simultaneously contract, thereby interrupting and terminating the abnormal electrical rhythm - without damaging the heart. Then, the heart's electrical system is able to regain control and restore a normal heartbeat.
Intravenous sedation will be administered since the shock can be painful. Patients typically awaken quickly without any recollection of the shocks. The procedure itself usually takes less than 30 minutes, but you will need to be monitored for at least several hours.