SCA

Sudden cardiac arrest (SCA) is also known as Sudden Cardiac Death (SCD.) It is often the result of what is known as Ventricular Fibrillation. The point is the heart is still alive but is not pumping normally. This is due to an electrical malfunction within the heart itself. Normally, heart rhythm is regulated by the Sinus node that causes the upper and lower heart to contract resulting in a pumping action. This becomes erratic causing the heart tissue to fibrillate or vibrate but not pump. The lack of circulation causes the victim to collapse and become unresponsive.

CPR can be performed to manually circulate blood to brain tissue and also heart tissue as well. However, effectively performed CPR only provides about 30% of the perfusion that a beating heart performs. The New England Journal of Medicine stated that the purpose of CPR is to sustain the victim until he can be defibrillated. Within 4 minutes, brain cells begin to die. Hence, early defibrillation is essential to the chance of recovery. Generally, the chance of survival drops 7% to 10% every minute.

The purpose of defibrillation is to send a shock through the heart and stun it. That should stop the erratic electrical activity and allow the heart to restart itself properly. It might take several shocks and several sessions of CPR to do this.