What is the initial energy for synchronized cardioversion of an unstable tachyarrhythmia with a narrow QRS?

What is the initial energy for synchronized cardioversion of an unstable tachyarrhythmia with a narrow QRS?

• A. 5-10 J
• B. 200 J
• C. 360 J
• D. 50-100 J (biphasic)

Answer: (D)

When delivering synchronized cardioversion for an unstable tachyarrhythmia with a narrow QRS, use the energy appropriate for modern biphasic devices. The initial shock is typically 50–100 joules. Modern biphasic shocks achieve effective cardioversion at these lower energies, and starting here reduces the risk of myocardial injury and other complications while still rapidly restoring a stable rhythm. If this first attempt doesn’t work, you escalate to higher programmed settings on subsequent shocks, rather than jumping to very high energies from the start. The other options are not appropriate for the initial synchronized shock: too low a dose won’t reliably cardiovert, while higher energies listed are more associated with defibrillation or with older monophasic devices.

When delivering synchronized cardioversion for an unstable tachyarrhythmia with a narrow QRS, use the energy appropriate for modern biphasic devices. The initial shock is typically 50–100 joules. Modern biphasic shocks achieve effective cardioversion at these lower energies, and starting here reduces the risk of myocardial injury and other complications while still rapidly restoring a stable rhythm. If this first attempt doesn’t work, you escalate to higher programmed settings on subsequent shocks, rather than jumping to very high energies from the start. The other options are not appropriate for the initial synchronized shock: too low a dose won’t reliably cardiovert, while higher energies listed are more associated with defibrillation or with older monophasic devices.