What is the critical determinant of survival from cardiac arrest?

The interval from collapse to defibrillation is indeed the critical determinant of survival from cardiac arrest. This is primarily due to the nature of how the heart responds to a lack of effective blood flow and the importance of restoring normal rhythm as quickly as possible. When a person experiences a cardiac arrest, the heart may go into a lethal rhythm such as ventricular fibrillation or pulseless ventricular tachycardia. The chances of successful defibrillation decrease significantly with time; for every minute that passes without defibrillation, the likelihood of survival diminishes by approximately 10%.

Timely defibrillation can effectively convert these abnormal rhythms back to a normal heart rhythm, thereby restoring effective circulation and increasing the chances of survival. While other factors such as the duration of CPR, the amount of oxygen delivered, and the promptness of advanced care are also important in the broader context of cardiac arrest management, they do not hold as critical a role as the time interval to defibrillation. This makes early defibrillation the key focus in improving outcomes for patients experiencing a cardiac arrest.