Atherosclerotic CHD is by far the number-one killer not only in the United States but also in the world. In the United States, it is estimated that 1 person dies of CHD every minute. The number of women who die of CHD is 10 times that of women who die of breast cancer.
Abnormal cholesterol intake and metabolism leading to atherosclerosis are central factors in the development of ischemic heart disease (IHD). The “fatty streak,” an early sign of atherosclerosis, is an accumulation of lipids and lipid-laden macrophages, called foam cells, under the endothelium of the coronary arteries. These cells organize into a plaque, and as the plaque becomes calcified, the lumen of the vessel narrows. The plaque can also become unstable and rupture, leading to turbulence and activation of the coagulation cascade and, ultimately, to intravascular thrombosis. The result is partial or complete vessel occlusion, which causes the symptoms of unstable angina or MI.
Ischemia is defined as local, temporary oxygen deprivation associated with inadequate removal of metabolites due to reduced tissue perfusion. IHD is typically caused by decreased perfusion of the myocardium secondary to stenotic or obstructed coronary arteries. The balance between arterial supply of and myocardial demand for oxygen determines whether ischemia occurs. Significant coronary stenosis, thrombosis, occlusion, reduced arterial pressure, hypoxemia, or severe anemia can impede the supply of oxygen to the myocardium. On the demand side, an increase in heart rate, ventricular contractility, or wall tension (which is determined by systolic arterial pressure, ventricular volume, and ventricular wall thickness) may increase utilization of oxygen. When the demand for oxygen exceeds the supply, ischemia occurs. If the ischemia is prolonged, infarction and myocardial necrosis result. The necrotic process begins in the subendocardium, usually after approximately 20 minutes of coronary obstruction, and progresses to transmural and complete infarction in 4–6 hours.
Excerpted from BCSC 2020-2021 series: Section 1 - Update on General Medicine. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.