Pathophysiology

Knowledge of the anatomy of the coronary arteries is essential to understand the effects of myocardial ischemia and why some complications are more common with anterior or inferior wall myocardial infarction. ( Fig. „47-1). The left coronary artery arises from the ascending aorta in the left sinus of the aortic valve. It courses through the atrioventricular sulcus on the left side and divides into the left circumflex and the left anterior descending branch. The left anterior descending branch courses down the anterior aspect of the heart around the inferior margin and anastomoses with the posterior diagonal branch of the right coronary artery. It is the main blood supply to the anterior and septal regions of the heart. The circumflex branch continues around the atrioventricular sulcus, where it anastomoses with the right coronary artery. It supplies blood to some of the anterior wall and a large portion of the lateral wall of the heart. The right coronary artery arises from the right sinus of the aortic valve and runs in the atrioventricular sulcus between the right atrium and right ventricle. It gives off a marginal branch near the lower aspect of the heart and terminates as the right posterior descending artery. The right coronary artery supplies the right side of the heart with blood and it provides some perfusion to the inferior aspect of the left ventricle through the posterior descending artery.

FIG. 47-1. Schematic diagram of the coronary arteries.

The atrioventricular (AV) conduction system receives blood supply from both the AV branch of the right coronary artery and septal perforating branch of the left anterior descending coronary artery. Similarly, both the right bundle branch and the left posterior division obtain a dual blood flow from the left anterior descending and right coronary arteries. The posteromedial papillary muscle receives blood supply from only a single coronary artery, usually the right coronary artery.

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