Voltage. Cardioversion means using a stimulus to change the heart's beat from an abnormal rhythm to a normal one. Certain drugs can be used, or electricity, usually only a low voltage is required unless the abnormal rhythm is a very dangerous one called ventricular fibrillation. When the rhythm is ventricular fibrillation, usually more voltage (electricity) is needed, and it is called defibrillation.
Cardiovert. Cardioversion is the process of converting an abnormal cardiac rhythm to normal. It encompasses any means of doing that. Defibrillation is a subset of cardioversion. It is when a fibrillation rhythm, atrial or ventricular is converted to a more normal rhythm.
Yes. Cardioversion encompasses defibrillation. Technically, if one is not in a fibrillating rhythm, the proper term for the act of delivering a shock to convert the rhythm back to normal is cardioversion, not defibrillation. In practice, the two terms are often used interchangeably however.
Not really. Technically yes, cardioversion is synchronized, defib is not.
Cardioversion. We use electrical cardioversion to convert tachyarrhythmias to normal rhythm when appropriate. When the rhythm we are shocking is atrial or ventricular fibrillation, we call the cardioversion defibrillation.