Final answer:
Elective cardioversion prevents disrupting the heart during the critical period of ventricular repolarization.
Step-by-step explanation:
Elective cardioversion is similar to defibrillation, but it waits to discharge until an R wave appears. This prevents disrupting the heart during the critical period of ventricular repolarization. Ventricular repolarization is the phase where the ventricles are getting ready for the next heartbeat. Disrupting this critical period can affect the heart's functioning.