Guest Author - Denise Howard, M.D., M.P.H.

Heart disease is the #1 cause of death in women. It is also preventable in many cases. One cause is a heart attack or myocardial infarction. Exactly what is a heart attack and what causes it?

Myocardial infarction (MI) or heart attack occurs when the blood flow to a portion of the heart is suddenly stopped. The tissue in that area then dies (infarcts) since it is no longer receiving oxygen supplied by the blood. If a small area is affected then the heart can continue to function. If a larger area is involved the consequence might be a degree of heart dysfunction. If a very large area is involved in the infarction then sudden death may result.

The blood that supplies the tissue of the heart flows through vessels called the coronary arteries. These arteries branch into smaller vessels to supply the tissue. These smaller vessels are called the microvasculature. This is similar to the branches of trees branching off to twigs. The coronary arteries can become coated with material over time that results in narrowing of their lumen. This is artherosclerotic disease and the coated areas are referred to as plaques. Sudden clotting of the plaques can lead to an acute obstruction of the vessel, blockage of the blood flow and death of the tissue: Heart Attack. During times of physical stress such as exercise or emotional stress such as anger the heart beats faster to supply the body with the increased oxygen it needs. The faster the heart beats the more oxygen it too needs. Vessels that are narrowed by artherosclerosis are unable to meet the demand for more blood. This too can lead to a heart attack. In some cases, the blood vessels can spasm resulting in a temporary decrease in the size of the lumen and a decrease in the blood supplied. This can happen in the microvasculature also. Chest pain may result, giving the appearance of a heart attack.

A heart attack typically occurs in the setting of increased activity or emotional stress that leads to an increase in the heart rate. Exercise, sexual activity, anger and fear are examples. Symptoms of a heart attack include chest pain or pressure, abdominal pain, arm pain or numbness, shortness of breath, sweating, dizziness, and nausea. The symptoms can sometimes be vague. The symptoms may resolve and recur before the actual infarction occurs. This is described as angina and is a warning of a pending attack. It is important to seek medical care immediately to identify the cause of the symptoms and potentially prevent a life threatening event.

Future articles will discuss other aspects of heart disease, risk factors and prevention.