Which rhythm is classified as shockable during cardiac arrest?

The rhythm that is classified as shockable during cardiac arrest is pulseless ventricular tachycardia. This condition is characterized by a rapid heart rate with no effective cardiac output, meaning the heart is beating too quickly to effectively pump blood to the body. When a patient is in this rhythm, immediate defibrillation is indicated to restore a normal heart rhythm and improve the chances of survival.

In contrast, the other rhythms listed do not elicit the same immediate need for defibrillation. Atrial fibrillation, while it can lead to serious complications, typically has some level of cardiac output and is not treated with shocks in an acute cardiac arrest situation. Bradycardia involves a slower than normal heart rate and may require other interventions, such as medication or pacing, rather than defibrillation. Ventricular escape rhythm is a form of intrinsic myocardial response that occurs when the heart's natural pacemaker fails, and while it indicates a serious condition, it is not considered a shockable rhythm.