Coronary blood flow is critical in supporting cardiac function. If disease states or acute events occur that obstruct coronary flow, consequences are commonly quite detrimental and/or fatal. For example, changes in electrocardiograms can be recorded within beats when there is inadequate blood flow delivered to a region of the heart. Whenever coronary blood flow falls below what is required to meet metabolic needs, the myocardium is considered ischemic; the pumping capability of the heart is impaired, and there are associated changes in electrical activity (e.g., increased risk of fibrillation). Prolonged ischemia can lead to myocardial infarction, commonly called a heart attack, which can cause irreversible myocardial cell death. Coronary artery disease, which is associated with obstruction of arterial blood flow (see figure), is the most common type of heart disease and the leading cause of death in the United States in both males and females.(1)

1. Alexander RW, Schlant RC, Fuster V, O'Rourke RA, Roberts R, Sonnenblick EH, eds. Hurst's the heart. New York, NY: McGraw-Hill, 1999.