Coronary Anatomy for the Interventionalist
A thorough knowledge of normal and abnormal coronary anatomy is essential for the interventional cardiologist. The direct application of this knowledge base helps in the selection of the appropriate catheter for coronary engagement in both diagnostic and intervention procedures. Knowledge of anatomy also facilitates the selection and interpretation of angiographic views during cardiac catheterization. Finally, because interventional therapy may be needed in several unusual circumstances, a working knowledge of coronary artery anomalies is also essential. This chapter addresses coronary artery anatomy and related technical issues pertinent to the interventional cardiologist.
The coronary arterial system can be divided into the large vessels, or the epicardial coronary arteries, and the small vessels, or the microvasculature. The microvasculature consists of arterioles, which measure less than 200 μm and are poorly visualized with routine coronary angiography. These arterioles feed a broad capillary network that delivers oxygenated blood to the myocardium. They also regulate coronary pressure and flow through their ability to vasodilate and constrict in response to a variety of stimuli. The importance of the microvasculature in determining patient outcomes in both the acute setting, such as myocardial infarction, and the chronic setting has been highlighted.1
Both the right and left coronary artery ostia arise from their respective aortic sinuses. Both ostia are located more than half the distance between the sinotubular junction and aortic valve annulus (Fig. 2-1). The left main coronary artery originates with an elliptic ostium measuring approximately 3.2 ± 1.1 mm × 4.7 ± 1.2 mm.2 This coronary artery continues at an acute angle and travels parallel to the aortic sinus wall, coursing between the pulmonary artery and the left atrium in the region of the left atrial appendage. The length of the left main artery ranges from 0 mm (“double-barrel ostium”) to 20 mm. However, in most cases, the length of the left main coronary artery is between 6 and 15 mm, with an average diameter ranging from 3 to 6 mm.3 In two-thirds of cases, the left main coronary artery bifurcates into the left anterior descending (LAD) and circumflex arteries (Fig. 2-2); in one-third of cases, it trifurcates into the LAD artery, the circumflex artery, and a ramus intermedius artery, which follows a course similar to either the first diagonal artery from the LAD artery or first obtuse marginal artery from the circumflex.4
Anterior (A) and posterior (B) view of the coronary arterial and venous system. AIV, anterior interventricular vein; CFX, circumflex coronary artery; CS, coronary sinus; GCV, great cardiac vein; LAD, left anterior descending artery; MCV, middle cardiac vein; PDA, posterior descending artery; RCA, right coronary artery; SCV, small cardiac vein.