What's a shock to the heart called? When someone delivers a shock to the heart to treat abnormal rhythms, what's that called?

See below. A shock used for cardiac arrest (ventricular fibrillation) is called defibrillation. All other shocks are called synchronized (direct current) cardioversions.
There . There are two types of shocks, where electrical energy is delivered to the heart to restore a normal heart rhythm. When somebody experiences cardiac arrest, the shock is called a defibrillation. This can be delivered by an external defibrillator applied by medical personnel or by a bystander. Many common areas such as airports and malls now have automatic external defibrillators (aeds) that can be applied by a layperson, and have been shown in research studies to increase the chances of survival after cardiac arrest. Some people at risk for cardiac arrest have defibrillators implanted in their body capable of recognizing abnormal rhythms and automatically delivering a shock. The other type of shock is called a synchronized cardioversion. This is performed when the heart is in an abnormal rhythm, but is still functioning fairly well and so is typically not performed in an emergency situation. Atrial fibrillation is the most common rhythm that requires cardioversion. This is a very safe and common procedure.