From WFTV: the best SCA vs AMI explanation I've seen in the media - too often they write "heart attack" when they mean SCA.

Cardiac Concerns: Saving Kids from Sudden Death

FLORIDA — WHAT CAUSES SUDDEN CARDIAC ARREST:Sudden cardiac arrest (SCA) is a condition in which the heart suddenly and unexpectedly stops beating. If this happens, blood stops flowing to the brain and other vital organs. SCA is not the same as a heart attack. A heart attack occurs if blood flow to part of the heart muscle is blocked. During a heart attack, the heart usually doesn't suddenly stop beating. SCA, however, may happen after or during recovery from a heart attack. People who have heart disease are at higher risk for SCA. However, SCA can happen in people who appear healthy and have no known heart disease or other risk factors for SCA. Certain diseases and conditions can cause the electrical problems that lead to SCA. Examples include coronary heart disease (CHD), also called coronary artery disease; severe physical stress; certain inherited disorders; and structural changes in the heart. (Source: nhlbi.nih.gov)

SIGNS OF SCA: Usually, the first sign of sudden cardiac arrest (SCA) is loss of consciousness (fainting). At the same time, no heartbeat (or pulse) can be felt. Some people may have a racing heartbeat or feel dizzy or light-headed just before they faint. Within an hour before SCA, some people have chest pain, shortness of breath, nausea (feeling sick to the stomach), or vomiting. (Source: nhlbi.nih.gov)

PREVENTION AND TREATMENT: If you’ve already had SCA, you’re at high risk of having it again. Research shows that an implantable cardioverter defibrillator (ICD) reduces the chances of dying from a second SCA. If you’re at high risk for a first SCA, your doctor may prescribe a type of medicine called a beta blocker to help lower your risk for SCA. Other treatments for CHD, such as angioplasty or coronary artery bypass grafting, also may lower your risk for SCA. If you have no known risk factors for SCA, CHD seems to be the cause of most SCAs in adults. CHD also is a major risk factor for angina (chest pain or discomfort) and heart attack, and it contributes to other heart problems. Following a healthy lifestyle with diet and exercise can help you lower your risk for CHD, SCA, and other heart problems. Also, try quitting smoking, losing weight, and treating other issues like high blood pressure, cholesterol, and diabetes. To treat SCA, defibrillation is needed within minutes to keep them alive. You should give cardiopulmonary resuscitation (CPR) to a person having SCA until defibrillation can be done. People who are at risk for SCA may want to consider having an AED at home. If you survive SCA, you'll likely be admitted to a hospital for ongoing care and treatment. In the hospital, your medical team will closely watch your heart. They may give you medicines to try to reduce the risk of another SCA. (Source: nhlbi.nih.gov)