Which of the following is the most dangerous cardiac rhythm?

Ventricular fibrillation is considered the most dangerous cardiac rhythm due to its chaotic electrical activity in the ventricles, leading to a loss of effective heart contractions. In this state, the heart is unable to pump blood, which results in a rapid loss of consciousness and, if not treated immediately, can lead to death.

In contrast, while ventricular tachycardia can be serious, it may still allow for some degree of blood circulation depending on the rate and duration. Atrial flutter, although irregular and potentially leading to other complications like stroke, does not typically cause immediate cardiac arrest. Bradycardia, characterized by a slower than normal heart rate, can be concerning but is generally less acute in its effects compared to the rapid onset of danger presented by ventricular fibrillation. Thus, ventricular fibrillation stands out as the rhythm that requires immediate intervention to restore a normal heart function and prevent fatal outcomes.