A heart attack is caused when blood flow to the heart is blocked due to a clot in one of the coronary arteries. Sudden cardiac arrest occurs when the heart malfunctions and suddenly beats irregularly.
Think of it as the difference between a plumbing and an electrical problem. The heart attack is a plumbing issue where blood flow to the heart is restricted. SCA is a short circuit of the electrical system which interrupts the heart's regular rhythm and keeps it from pumping blood through the body.
While a heart attack victim risks death, a sudden cardiac arrest victim has a greater chance of immediate death unless the heart is shocked promptly.
Physiology of the heart
An adult heart beats 60 to 100 beats per minute. This is called ‘normal sinus rhythm’ . This very regular pattern feeds oxygen-rich blood to the entire body and is managed by the sinoatrial (SA) node and the atrioventricular (AV) node. Electrical impulses leave the SA node and travel to the AV node. In concert, these nodes maintain 'normal sinus rhythm'.
Similar to the electrical wiring in your home, there can be a short circuit. When this happens, there is an abrupt loss of heart function - sudden cardiac arrest. Instead of pumping regularly, the heart quivers uncontrollably and blood is not circulated. This is called ventricular fibrillation.
Death follows unless emergency treatment is provided quickly. The only definitive way to return the heart to its regular normal sinus rhythm is by performing cardiopulmonary resuscitation (CPR) and applying an electrical shock from an Automated External Defibrillator (AED).
There are risk factors that can increase the chances of SCA such as:
- A previous heart attack
- Coronary artery disease
- Family history of SCA
- Congenital heart defect
However, 50% of people who experience an SCA reported no prior symptoms of heart disease.