Biomedical Engineering Reference
In-Depth Information
Despite major advances in diagnosis and prevention of heart disease, heart attacks
continue to be the major cause of morbidity and mortality in the industrialized world.
A heart attack, due to blocking of coronary artery, acute myocardial infarction, has
serious consequences. Within minutes, lack of oxygen in the tissue irrigated by the
coronary artery, causes cell death in the heart muscle. If thrombolytic treatment is
not administered immediately, the damage is irreversible. The adult heart lacks
reserve cells and cannot regenerate. Reperfusion injury including no-reflow phe-
nomenon may increase the infarct size and require cardioprotective strategies that
are mentioned later in this chapter. In the postinfarction phase, the remodeling pro-
cess is characterized by hypertrophy of myocardium and dilation of the left ventricle
with cardiomyocyte replacement by fibrous tissue. There is progressive loss of via-
ble tissue, and infarct extension eventually results in heart failure.
Current therapeutic options for myocardial infarction include medical therapy of
proven but limited benefit, and various surgical options, which have either restricted
applicability or unproven benefit. Various methods of treating heart failure include
long-term medication, temporary devices such as artificial pumps, and heart trans-
plants. Less than one in ten persons who need heart transplants will find suitable
donors. Although the current treatments for cardiovascular disease prevent heart
attack from occurring and/or alleviate its aftereffects, they do not repair the dam-
aged muscle that results, leaving sizably dead portions of heart tissue that lead to
dangerous scars in the heart. Damage done by a heart attack to heart muscle is
really the cause of all the serious complications of the disease: disturbances of heart
rhythm can lead to sudden cardiac death and decreased muscle pumping function
can lead to congestive heart failure. The ideal treatment is to repair the damage
done to the heart muscle and prevent these complications. This is the rationale for
cell/gene therapies to be described in later chapters of this report.
Angina Pectoris
Angina pectoris is a serious and debilitating heart condition marked by repeated
and sometimes unpredictable attacks of cardiac pain or discomfort. Angina attacks
are typically triggered by physical exertion or emotional stress and occur when the
heart is not receiving all the oxygen that it needs to function effectively. Usually
angina is associated with coronary artery disease, which is characterized by a
buildup of fatty plaques in coronary arteries that reduce the flow of oxygen-rich
blood through the heart. When the blood supply to the heart is inadequate and can-
not provide enough oxygen to meet the heart muscle's demand (a condition called
myocardial ischemia), an angina attack may occur.
Cardiomyopathies
Cardiomyopathies are disorders affecting the heart muscle that frequently result in
congestive heart failure. Five major forms are recognized: dilated, hypertrophic,
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