How to Recognize and Respond to a Heart Attack

Heart attack — myocardial infarction — is the most common cause of death in the United States. Each year, approximately 805,000 Americans have a heart attack; one occurs every 40 seconds. Yet approximately 50% of cardiac deaths occur before emergency medical services arrive — many in people who delayed calling 911 because they weren't sure their symptoms were serious. Recognizing a heart attack and responding immediately are among the most life-saving skills anyone can develop.

What Happens During A Heart Attack

The heart muscle requires a continuous supply of oxygenated blood delivered by the coronary arteries. A heart attack occurs when a coronary artery is suddenly blocked — typically by rupture of an atherosclerotic plaque followed by blood clot (thrombus) formation at the rupture site. The blockage cuts off blood flow to the downstream heart muscle. Without oxygen, heart muscle cells begin dying within 20–40 minutes and can continue dying for hours.

Time is muscle: The more quickly blood flow is restored, the less heart muscle is permanently damaged. Modern treatment — primary percutaneous coronary intervention (PCI, or coronary stenting) — can open the blocked artery, but every minute of delay results in more irreversible muscle damage. The goal is "door-to-balloon time" (from hospital arrival to artery reopening) under 90 minutes — achievable only when patients call 911 promptly.