Within the interventricular septum, septal branches of the LAD freely anastomose with the septal branches of the PDA. In 10% of the cases, no such anastomoses exist. The terminal LAD anastomosis with the terminal branches of the posterior descending artery (PDA) in the posterior interventricular groove about 90% of the time. Multiple anastomoses exist between the coronary arteries. Usually, a couple of small right ventricular branches also arise from the LAD supplying small parts of the anterior right ventricle. Around the apex, the LAD anastomoses with the terminal branches of the posterior descending artery which is usually a branch of the right coronary artery.ĭepending upon the length of the LAD, the LAD is classified into four types: type-I – does not supply the left ventricular (LV) apex, type-2 – supplies part of the apex, the rest being supplied by the right coronary both, type3 – supplies the entire apex, and type-4 – supplies the apex and >25% of the inferior wall (wrap around).Ī small left conus branch usually arises from the proximal LAD and anastomoses with its counterpart from the right coronary artery around the aortic conus and also with the vasa vasorum of the aorta and the pulmonary artery. These are also numbered D1, D2, onwards starting from proximal to distal. The second set of branches course over the anterior aspect of the left ventricle and are called diagonal branches. These are numbered as S1, S2, onwards starting from base to the apex. The septal branches perforate the interventricular septum to supply the anterior two-thirds of the septum. The left anterior descending artery (LAD) is the largest coronary artery runs anterior to the interventricular septum in the anterior interventricular groove, extending from the base of the heart to the apex. The coronary arteries run on the epicardial surface of the heart to avoid being compressed by the cardiac muscle when it contracts. Just like any other capillary bed, the coronary circulation is controlled by local autoregulation mediated by demand dependent arteriolar dilatation. Therefore, the coronary flow is dependent on diastolic blood pressure. All coronary flow, therefore, occurs during diastole when the pressure from the cardiac contraction is not obstructing the blood flow. During systole, the heart muscle squeezes over the perforating arteriolar branches and causes complete cessation of flow. The LAD carries almost 50% of the blood carried by the coronary circulation.
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