In Sudden Cardiac Death, Time Is Memory

Early defibrillation is a critical step in the treatment of out-of-hospital cardiac arrest (OHCA), as it can significantly increase the chances of survival for the person experiencing the cardiac arrest. Cardiac arrest is a sudden loss of heart function, which can be caused by various underlying conditions such as a heart attack or abnormal heart rhythms (arrhythmias). When a person experiences cardiac arrest, their heart stops effectively pumping blood to the body, and the individual will rapidly lose consciousness. Without prompt treatment, the lack of oxygen to organ systems is catastrophic.

The brain is particularly at risk. And while advanced care such as pacemakers can facilitate physiological resuscitation, cognitive function remains a central determinate for a functional recovery.

Simply put, time is memory.

One of the most effective treatments for cardiac arrest is defibrillation, which involves using a device to deliver an electrical shock to the heart. The shock can potentially restore a normal heart rhythm and allow the heart to start pumping blood again. Interestingly, the process of defibrillation doesn’t “shock the heart” back to a normal rhythm.

The electric current that passes through the heart provides a uniform depolarization that “turns off” the multiple and chaotic impulses of ventricular fibrillation to allow a normal beating mechanism (that usually starts in the atrium and called sinus rhythm) to take over in a synchronous, effective cardiac contraction. Without defibrillation, the heart remains as a quivering mass of muscle unable to correct itself.

The sooner defibrillation is performed, the greater the chances of survival. In the case of OHCA, early defibrillation by trained lay responders or emergency medical services (EMS) can significantly improve outcomes. And the value of the automated external defibrillator that are widely available in public places is tremendous, but sadly, often either not used or used too late.

For optimal results, defibrillation should be performed within the first few minutes of cardiac arrest. This is because the longer the heart goes without pumping blood, the more damage is done to the body. After about 10 minutes of cardiac arrest, the chances of survival decrease significantly. The data are compelling.

“When time from collapse to first EMS defibrillation was analyzed as a continuous variable, each 1-min delay was associated with a significant decrease in the likelihood of good neurological recovery.”

It is important for people to be trained in basic life support (BLS) including CPR and to have access to automated external defibrillators (AEDs) in order to provide early defibrillation in the event of an OHCA. By acting quickly and providing appropriate treatment, it is possible to save the life of a person experiencing cardiac arrest. But beyond the knowledge, the practical application of technology—particularly the defibrillator—is at the cornerstone of managing OHCA. And outcomes are clearly a function of speed. Situational awareness of available technology and prompt action are essential. The automation of defibrillation with today’s AED can turn any citizen from a bystander to a lifesaver!