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CORONARY ARTERY DISEASE
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The coronary arterial circulation carries oxygenated blood from the ascending aorta to the myocardium. The left main and right coronary arteries begin their courses at the aortic root within the left and right sinuses of Valsalva, respectively (Figure 22–1). The left main coronary artery takes a short path (often < 2 cm) between the pulmonary artery and left atrial appendage before it divides into the left anterior descending artery (LAD) and the left circumflex artery, while the right coronary artery continues without significant division along its length. These three vessels are considered to supply the three main territories of the heart: anterior (LAD), lateral (left circumflex), and inferior (right). These main branches largely traverse the epicardial surface of the heart, leaving them prime for bypass targets.
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The LAD, or anterior interventricular artery, runs within the groove between the left and right ventricles on the anterior surface of the heart, generally terminating at the cardiac apex. The LAD gives off diagonal branches that extend over the anterolateral surface of the heart as well as septal perforating branches that feed the interventricular septum. The LAD is the largest of the three main coronary branches and carries approximately half of myocardial blood flow.
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The left circumflex artery courses posteriorly from its takeoff from the left main coronary artery to wrap around the heart within the atrioventricular groove. It gives off obtuse marginal branches that supply the lateral aspect of the heart. Approximately 15%-30% of individuals have a third branch of the left main coronary artery that runs between the LAD and left circumflex, supplying the anterolateral wall of the heart; this is termed a ramus intermedius.
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The right coronary artery extends anteriorly from the right sinus of Valsalva to traverse the right aspect of the atrioventricular groove. Along the acute margin of the heart, the right coronary artery provides branches to the ventricular outflow tract (conus branch), the anterior ventricle, and the acute margin. The posterior aspect of the heart is supplied by a posterior descending artery located within the posterior interventricular septum. In 80%-85% of individuals, this is a terminal branch of the right coronary artery, and this anatomy is termed a right-dominant system. In 5%-10% of cases, the posterior descending artery is the terminal branch of the left circumflex artery, making this a left-dominant system. A co-dominant system, in which posterior descending arteries come from both the right coronary and circumflex arteries, occurs in about 10% of the population. The right coronary artery also supplies blood to the sinoatrial and atrioventricular nodes of the cardiac conduction system in the majority of individuals.
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The coronary arteries ultimately continue as arterioles and then capillaries. The capillary-to-cardiomyocyte ratio is ...