Although many quarts of blood pass through the heart each day, the heart cannot
utilize the blood within itself, but rather is sustained by branches of arteries originating externally. These coronary arteries can become blocked by the deposition of fatty
material (inlcuding cholesterol), connective tissue fibers, and calcium deposited in the
vessel walls. If the blockage is severe, numerous heart muscle cells become oxygen
starved and the heart stops. In less sever cases, only part of the heart muscle dies as
a result of the blockage. The dead muscle is replaced by scar tissue and the heart
continues to function, though less efficiently. Diet, stress, smoking, and alcohol all
contribute to the problem of heart attacks. Interestingly, although fats in the diet are
often blamed for the heart attacks, about 70% of the heart’s energy requirement
normally is derived from oxidation of fatty acids. -Biology by Norstog and Meyerriecks
Coronary arteries can become blocked by