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- Patient Comments: Heart Attack Pathology - Signs and Symptoms
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- What is a Heart Attack?
- What are the structures and functions of a normal coronary artery?
- What happens to the coronary artery in atherosclerosis?
- Who gets coronary artery plaques and what happens to the plaques?
- What happens to the heart muscle after a person survives a Heart Attack?
- Can a person have more than one heart attack?
What happens to the coronary artery in atherosclerosis?
In coronary artery disease (coronary atherosclerosis), injury to the intima of the artery leads to the formation of plaques, which are regions of thickening on the inner lining of the artery. How then do the plaques form? In response to the injury, the smooth muscle cells (SMCs) from the media and perhaps from the adventitia move (migrate) into the intima. In the intima, these SMCs reproduce themselves (divide) and make (synthesize) connective tissue. These processes of migration, division, and synthesis, which collectively are referred to as intimal proliferation (buildup), cause thickening of the intima. When cholesterol, other fats, and inflammatory cells, such as white blood cells, enter the proliferating, thickened intima, the result is an atherosclerotic plaque. Then, as these plaques grow, they accumulate scar (fibrous) tissue and abundant calcium. (Calcium is the hard material in our teeth and bones.) Hence, the plaques are often hard, which is why atherosclerosis is sometimes referred to as "hardening of the arteries."
Who gets coronary artery plaques and what happens to the plaques?
Most adults in industrialized nations have some plaques (atherosclerosis) on the inner (lumenal) surface of their coronary arteries. Autopsy studies of young soldiers who died in World War II, the Korean War, and the Vietnam War showed that even young adults in their 20s usually have coronary arteries that exhibit localized (focal) thickening of the intima. This thickening is the beginning of intimal proliferation and plaque formation. The distribution, severity (amount of plaque), and rate of growth of the plaques in the coronary arteries vary greatly from person to person. Figure 2 shows a coronary artery with an uneven (asymmetric), stable atherosclerotic plaque. A stable plaque may grow slowly, but has an intact inner (lumenal) surface with no clot (thrombus) on this surface.
Figure 2: Coronary Artery with Stable Atherosclerotic Plaque; Cross-sectional Microscopic View
Rupture of a stable plaque in a coronary artery is the initial pathological event leading to a heart attack. When the rupture occurs, a clot suddenly forms in the lumen (channel) of the artery at the site of the rupture. Bleeding into the plaque often accompanies the rupture. The clot then blocks (occludes) the artery and thereby decreases the blood flow to the heart. This sequence of events in the coronary arteries is the basic problem in over 75% of people who suffer a heart attack. In some patients, more often women, there is just an erosion or ulceration of the plaque surface, rather than a full rupture that leads to clot formation in the coronary artery. Figure 3 shows an atherosclerotic plaque rupture and a clot in a coronary artery.
Figure 3: Rupture of Atherosclerotic Plaque in Coronary Artery; Cross-sectional Microscopic View