Each year, over a million Americans suffer from a heart attack, and approximately 460,000 of those heart attacks are fatal. Nearly half of those deaths occur within 1 hour of the start of symptoms and before the person even arrives at the hospital.

These figures are important, because they demonstrate just how crucial it is that a person get immediate medical attention if they believe they’re having a heart attack.

Our hearts work 24 hours a day, 7 days a week, pumping oxygen and nutrient-rich blood throughout the body. Just like all of our muscles and organs, the heart itself needs blood to function. Coronary arteries supply blood, and therefore oxygen and nutrients, to the heart.

When a patient has coronary artery disease, plaques form and build up inside the walls of the coronary arteries, leading to atherosclerosis. These plaques can fragment and form a blood clot that can block the flow of blood to the heart.

If a blood clot suddenly cuts off most or all blood supply to the heart, a heart attack may occur. Cells in the heart muscle that don’t receive enough oxygen and nutrient-rich blood begin to die. This can cause the affected area of the heart’s wall to contract abnormally. The more time that passes without treatment to revive the flow of blood, the greater the damage to the heart.