Sudden cardiac arrest and heart attacks are different:
Different symptoms: A heart attack and SCA produce different symptoms in their victims.
Sudden Cardiac Arrest symptoms:
Collapse and loss of consciousness;
Loss of pulse and blood pressure;
Cessation of normal breathing; and
Unresponsiveness
Heart attack symptoms:
Uncomfortable pressure, fullness, squeezing, or pain in the center of the chest lasting more than a few minutes
Pain spreading to the shoulders, neck, or arms
Chest discomfort with lightheadedness, fainting, sweating, nausea, or shortness of breath
Atypical chest pain, stomach, or abdominal pain
Nausea or dizziness
Shortness of breath and difficulty breathing
Unexplained anxiety, weakness, or fatigue
Palpitations, cold sweat, or paleness
Different causes:
A heart attack (or myocardial infarction) occurs when a blockage slows or stops blood flow to some part of the heart muscle. If the blockage is severe or if it is left untreated, that part of the heart muscle can die. Heart attacks do not necessarily cause cardiac arrest or sudden cardiac death, although those conditions could result.
By contrast, SCA is usually the result of a congenital abnormality, but can result from a blow to the chest, a phenomenon called commotio cordis
Different treatments:
CPR may be an effective treatment for a heart attack until paramedics arrive
CPR is not effective for an SCA victim, for whom early defibrillation with an AED is essential, and the most important link in the Chain of Survival.