What Is a Synchronized Electrical Cardioversion?

Cardioversion is typically used to terminate a life-threatening or unstable tachycardic arrhythmia.

Synchronized electrical cardioversion is a medical procedure in which an electric current is passed through a person’s chest to convert abnormal heart rhythm (arrhythmia) to normal heart rhythm. The direct current (DC) shocks to the heart has long been used successfully to convert abnormal heart rhythms back to normal rhythms. The use of an electric current as a rescue method dates back to the eighteenth century when electricity was used to revive a hen from lifelessness. Dr. Beck was the first physician to use a DC to treat arrhythmia in a 14-year-old boy during cardiac surgery in 1947.

Cardioversion is typically used to terminate a life-threatening or unstable tachycardic arrhythmia (arrhythmias with an increased heart rate such as unstable ventricular and supraventricular rhythms). In synchronized electrical cardioversion, the electrical discharge from the cardioversion machine is synchronized with the electrical activity of the patient’s heart. During an arrhythmia, the heart does not pump enough blood to the body. Irregular heart rhythms if left untreated can lead to more serious conditions such as a heart attack or stroke.

Synchronized electrical cardioversion is done to restore normal heart rate and rhythm, so the heart can pump blood as it should. The procedure is required in cases when the heartbeat is too fast or irregular, which may cause the following symptoms:

• Chest pain or discomfort
• Light-headedness or dizziness
• A pounding or fluttering in the chest
• Shortness of breath
• Chest discomfort
• Extreme fatigue

The various types of arrhythmias that may be managed with synchronized electrical cardioversion are

• Supraventricular tachycardia (SVT) due to re-entry
• Atrial fibrillation (AF, afib)
• Atrial flutter
• Atrial tachycardia (AT, atrial tach)
• Monomorphic ventricular tachycardia with pulses

• Synchronized electrical cardioversion may be scheduled (elective procedure) or done as an emergency procedure. 
• It is typically an outpatient procedure that means you can go home on the same day.
• In case of a scheduled or planned procedure, before the procedure, your doctor may
  • Order some blood tests and imaging studies
  • Ask about any allergies you may have
  • Ask you about any long-term health conditions you may have
  • Ask you about any medications you are on
  • Explain the procedure in detail along with the risks involved
  • Ask you to shave any hair on the chest
  • Take your consent for the procedure
  • Ask you not to eat or drink anything for at least eight hours before the procedure
• During the procedure
  • You will be asked to wear a hospital gown.
  • The doctor will attach an intravenous (IV) line and administer sedatives and painkillers.
  • The doctor will place several electrodes (sticky patches) and adhesive cardioversion pads on your chest and sometimes on the back.
  • The electrodes are connected to a cardioversion machine through wires.
  • The cardioversion machine records the heart rhythm and delivers shocks to the heart to restore a normal heart rate and rhythm.
• Once you are sedated, the procedure usually takes a few minutes to complete.
• After the procedure, you will be monitored in the recovery room for any complications before you are allowed to go back home.

Both synchronized cardioversion and defibrillation are performed to restore a normal heart rhythm. However, they differ in some respects:

• In synchronized cardioversion, the electric current is synchronized or timed with the electrical activity of the patient’s heart (the QRS complex in electrocardiography [ECG]). The synchronized shock is delivered at a precise moment to avoid causing or inducing a certain type of arrhythmia (ventricular fibrillation). The defibrillation procedure, on the other hand, delivers an unsynchronized electric current to the heart.
• Although synchronized cardioversion is often performed in stable patients, defibrillation is typically done in unresponsive patients in a cardiac arrest.
• Synchronized cardioversion delivers a low energy shock to the heart, whereas during defibrillation, a high-energy shock is delivered without the need to time the shock to the unstable rhythm.