Heart Attack & SCA

Heart Attack & Sudden Cardiac Arrest:

Problems with the Heart's Plumbing & Electrical System

Your heart has two main systems that help it run efficiently. First, your heart is a pump. It has a network of pipes (blood vessels) along with some valves and pumping chambers. In addition, your heart is a complicated electrical system. The heart generates its own electricity and uses this electricity to run the pumps (upper and lower chambers, also called the atria and ventricles) causing them to contract and relax in the proper timing sequence.

A heart attack, also called a myocardial infarction (MI), is a problem with the heart's plumbing system. In a heart attack, a portion of the heart muscle stops working because it no longer receives blood. Generally, a heart attack occurs when plaque (fat, cholesterol and calcium) builds up and then ruptures in the coronary artery, creating a place where a blood clot can form. Eventually, this blood clot totally blocks the coronary artery. The clot stops blood flow, so the heart tissue beyond the point of the blockage does not get any blood and oxygen. If there's no blood flow to the tissue, the tissue dies, and the heart's muscle becomes damaged and unable to function. This causes serious consequences to the patient.

In contrast, Sudden Cardiac Arrest (SCA), is caused by an electrical accident in the heart. In SCA, ventricular tachycardia or ventricular fibrillation causes the heart to beat too fast. In this condition, the heart no longer beats effectively and cannot pump. As a result, blood flow is greatly impaired and may even stop. Often, this condition is deadly.

A recent study - Multi-center Automatic Defibrillator Implantation Trial II (MADIT II) - found that people who have survived a heart attack, yet who have extensive muscle damage, may be at risk for Sudden Cardiac Arrest due to the heart’s inability to pump enough blood. For many of these patients, physicians are recommending an implantable cardioverter defibrillator (ICD). As published in the New England Journal of Medicine, MADIT II showed a 31% reduction in the risk of death from Sudden Cardiac Arrest in those patients who received ICDs compared to those patients who did not.

The results of a second scientific study, Sudden Cardiac Arrest – Heart Failure Trial (SCA-HeFT), continued to show the benefits of ICD therapy by demonstrating a 23% reduction in death versus other treatment programs.