Which method delivers nonsynchronous energy to the myocardium?

• A. Cardioversion
• B. Defibrillation
• C. Pacing
• D. Cardiomyopathy therapy

Answer: (B)

Nonsynchronous energy is used when the goal is to rapidly depolarize the heart without timing the shock to a specific point in the cardiac cycle. This approach seeks to reset chaotic electrical activity, allowing the heart’s natural pacemaker to resume a normal rhythm. That is why defibrillation is the correct choice: it delivers a high-energy shock that is not synchronized to the ECG, effectively terminating ventricular fibrillation or pulseless ventricular tachycardia.

In contrast, synchronized energy is applied in cardioversion, where the shock is timed to the R wave to avoid hitting the vulnerable period and to restore a stable rhythm when a pulse is present. Pacing delivers regular, small electrical impulses at a set rate (or on demand) to maintain heart rate, not to terminate a life-threatening arrhythmia. Cardiomyopathy therapy describes treatment for the underlying heart muscle disease rather than a method of delivering energy to halt an arrhythmia.