Heart Attack Pathology: Photo Essay (cont.)
What causes a Heart Attack?
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
What happens to the heart muscle after a person survives a Heart Attack?
According to medical studies, 50% to 75% of people survive their first heart
attack The others die during the heart attack because the decreased coronary
blood flow causes a severe abnormal heart rhythm or extensive death of heart
muscle. Figure 4 shows the heart of a patient who died 5 days after a heart
attack. The photos show his myocardial infarction as it appears on the surface
of the left ventricle and when the heart is sliced to view the muscle wall.
About 90% of myocardial infarctions involve only the left ventricle (LV), which
pumps oxygen-rich blood that comes from the lungs to the entire body. The other
10% also involve the right ventricle (RV), which pumps the blood to the lungs.
Figure 4: Myocardial Infarction Caused by Heart Attack
Views of Heart Surface and Slice Across Heart
If a person survives a heart attack, the heart muscle may return to normal or
become a region of dead heart muscle (the myocardial infarction). The amount and
health of the remaining heart muscle is the major determinant of the future
quality of life and longevity for a patient after a heart attack. A heart attack
can interrupt the normal electrical wiring of the heart, leading to abnormal
heart rhythms. The heart attack can also weaken the pumping action of the heart
causing shortness of breath due to heart failure. Each of these complications of
a heart attack can occur at any time during the recovery period as a result of
dead, dying, or scarring heart muscle.
Next: Can a person have more than one Heart Attack? »
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