Which ventricular rhythm is considered life-threatening and requires immediate intervention?

Ventricular fibrillation is considered life-threatening because it is a chaotic and irregular electrical activity in the ventricles that prevents them from contracting effectively. This results in the heart's inability to pump blood, causing a rapid loss of consciousness and death if not treated immediately. The need for immediate intervention, such as defibrillation or advanced cardiac life support, is critical to restore a normal heart rhythm and maintain circulation.

In contrast, while ventricular tachycardia can also be serious and may require treatment, it sometimes can be stable and may allow for some blood circulation. Atrial flutter, though it can lead to complications, is generally not as immediately dangerous as ventricular fibrillation. Paget's disease is unrelated to cardiac rhythms and does not pose a life-threatening risk in this context. Thus, the urgency of addressing ventricular fibrillation makes it the most critical condition requiring immediate intervention.