The heart is a very specialized organ that we take for granted. Did you know that the heart is a muscle that can contract on its own? The heart has its own supply of nerves that cause it to contract and pump blood through the body. These nerves are normally controlled by a cluster of nerves called the SA node (sinoatrial node) in the top part of the heart. The SA node is commonly called the natural “pacemaker” of the heart and therefore controls the rate.

Sometimes the nerves in the heart fire in a chaotic pattern called ventricular fibrillation preventing the heart muscle from contracting properly in order to pump blood. During ventricular fibrillation, the patient will not have a pulse and will ultimately die unless the heart receives a shock. Defibrillation delivers a high dose of electricity to the heart to stop the chaotic nerve firing in order to allow the natural pacemaker of the heart to take over again. It is important to remember that not every patient in cardiac arrest is in ventricular fibrillation. That is why defibrillation is only useful for some of the patients in cardiac arrest.

Another interesting fact is that ventricular fibrillation will only last a few minutes before the electrical activity ceases completely and the heart muscle dies. This is due to decreased circulation of oxygenated blood to the body. Studies have shown that initiating CPR (cardio pulmonary resuscitation) shortly after cardiac arrest increases the chances of survival. This further emphasizes the need for the community to learn CPR.