The heart lies at the center of the circulatory system, functionally speaking, and is responsible for circulating blood throughout the body. Since cells depend on blood supply to receive nutrients and oxygen, heart disease that affects the function of the circulatory system can be quite dangerous. There are a number of effects that heart disease can have on the circulatory system itself.
Reduced Blood Flow
Some forms of heart disease, like congestive heart failure, limit the ability of the circulatory system to send blood to all of the body cells. The American Heart Association says that congestive heart failure may be the result of any number of processes. Regardless of how it comes about, however, it represents a weakened capacity for pumping by the heart muscle. Treatments generally include pharmaceuticals designed to assist the heart in delivery of blood, including vasodilators, which widen the blood vessels so the heart doesn't have to work as hard to push blood through the arteries. Also, beta blockers, which help increase the heart rate and strength of the heartbeat, can help the heart perform adequately to prevent circulatory failure.
Some forms of heart disease actually increase the likelihood of other negative effects on the heart. Atherosclerosis, for instance, is a common form of heart disease that involves hardening and narrowing of the arteries. According to Gary Thibodeau in his book, "Anatomy and Physiology," atherosclerosis increases the likelihood of myocardial infarction, or heart attack. Since atherosclerotic plaques form most commonly in the large arteries near the heart, they are subject to high-pressure blood pulsing through them regularly. This can tear plaques and lead to bleeding, which causes the formation of a blood clot. The heart muscle feeds itself blood via smaller arterial branches that break off the main arteries. If a clot dislodges and makes its way into one of these smaller branches, it can block the heart's own blood supply, leading to heart muscle death. This reduces the ability of the heart to function.
Another possible circulatory system effect of heart disease is the lodging of clots, most commonly formed in the arteries of patients with existing heart disease, in blood vessels in the brain. Thibodeau notes that if diseased arteries bleed under stress and form clots, the clots frequently break off and travel through the bloodstream until they reach a vessel through which they are too large to pass. Early branches off the arteries include smaller arteries that lead up to the brain, which requires a constant blood supply. If arterial clots travel up these passages into the brain, they quickly become lodged as arteries branch and narrow. This prevents blood flow to a portion of the brain, which causes brain cell death, or a stroke. Depending on the part of the brain that dies, strokes can result in loss of movement, speech or sensation. They may also be fatal.