A heart attack is caused when blood flow through one or more of the heart (coronary) arteries that supply blood to the heart is cut off. While blood flow can be blocked if the artery spasms and obstructs flow, for example, the majority of heart attacks are caused by blood clots (thrombosis) that form around ruptured plaques. A plaque is a build-up in the artery wall of a fatty material containing cholesterol, calcium and other substances. When plaque ruptures, the material within the plaque can attract red blood cells and platelets, which can then increase the chance of a blood clot forming. When a blood clot forms around a ruptured plaque, it blocks off blood flow through the artery and starves the heart muscle of necessary oxygen and nutrients.

A Systemic Problem

Plaque builds up in our arteries as we age, and not just in the arteries that supply blood to the heart. This build-up of plaque, or “hardening of the arteries,” is called atherosclerosis, and it is the same disease process that causes coronary artery disease, carotid artery disease and peripheral artery disease (PAD). Blockages in the carotid arteries in the neck can cause strokes. Peripheral artery disease (PAD) is a condition in which blockages are present in the legs, feet or arms, or in the arteries leading to the kidneys (more specifically called kidney artery disease or renal artery disease).

Anyone who has been diagnosed with coronary artery disease is also at risk for carotid artery disease and peripheral artery disease, and vice versa. For example, according to the American Heart Association, people with peripheral artery disease are four to five times more at risk for heart attacks and strokes.

Risk Factors for Heart Disease

To lower your risk of a heart attack, you will want to reduce the risk factors that contribute to coronary artery disease (CAD), as well as cardiovascular disease throughout your body. SecondsCount features in-depth information on the Causes of Coronary Artery Disease and strategies for Risk Factor Modification.

Triggers for Heart Attack

A trigger is something that starts a heart attack, but it’s not a cause in the same way as an underlying risk factor, such as heredity, or a disease process, like atherosclerosis (“hardening of the arteries”). Rather, a trigger is the event that starts a heart attack in the presence of existing disease.

Here are some common heart attack triggers, although there are others as well.

• Vigorous activity. Strenuous exercise or physical labor increases demands placed on the heart. If someone has narrowed or blocked coronary arteries, blood flow will not be sufficient to support vigorous activity and heart functioning.

• Shoveling snow. This is a form of vigorous activity, but it is worth listing separately, as it is a common heart attack trigger. The weight of snow on a shovel, combined with the extra strain put on the heart by cold temperatures, and the fact that many people who attempt to shovel snow do not normally exercise, makes this a particularly dangerous activity. Learn tips for taking care of your heart when it gets cold.

• Circadian variation. Circadian rhythms are biological processes in the body that follow a roughly 24-hour schedule in response to daylight and darkness. Each process might be most active at a different time. Biological processes that are most active in the first hours upon waking – such as the heart’s need for more oxygen, increased cortisol levels and higher blood pressure – seem to make the early morning hours a trigger for heart attacks.

• Stress. Stress is a known heart attack trigger, though more research is needed to figure out exactly why. Research suggests that stress hormones and a stress-related elevation in blood pressure may trigger heart attacks. Extreme emotional or physical stress can also lead to broken heart syndrome, or takotsubo syndrome.