What is a sync cardioversion?

Shock synchronized: The electric shock is synchronized to the heart beat to avoid shocking at the wrong time in the cycle which could make problems worse.

Timing: It's an electrical shock applied to the heart which is synchronized to the instant of electrical depolarization (the electrical wave that initiates systole) which is the safest part of the cardiac cycle.

Timed shock: This is a cardioversion (shock) given to the heart that is timed to a certain point in the cardiac cycle so that the heart rhythm can be reset without causing further rhythm problems. This is the most common type of shock delivered for rhythms such as atrial fibrillation.