In which condition is CPR immediately required due to the complete absence of any cardiac rhythm?

The condition associated with the complete absence of any cardiac rhythm is Ventricular Asystole. In this situation, the heart is not generating any electrical impulses, resulting in no heartbeat and no blood circulation. This is a critical and life-threatening state where immediate cardiopulmonary resuscitation (CPR) is essential to try to restore some form of circulation and maintain perfusion to vital organs.

Other conditions listed, such as Ventricular Tachycardia and Atrial Fibrillation, involve the presence of electrical activity, although it may be abnormal. In these scenarios, CPR may not be necessary if there is some effective pumping activity, even if it is insufficient. First-Degree AV Block demonstrates slowed conduction through the heart's electrical system but does not result in a complete absence of cardiac rhythm; therefore, CPR is not immediately required in that instance as there could still be effective heartbeats.