Q. Can you explain Relation between Coronary Artery and Myocardial supply?

Ans.

There is a well-established relation between a given epicardial coronary artery and its myocardial supply. Generally, the basal half of the ventricular septum and the anterior left ventricular free wall are prefused by the LAD coronary artery. A dominant right coronary artery perfuses anterior, lateral and posterior right ventricular myocardium. The posterior coronary artery (most commonly arising from the RCA) supplies blood to the posterior quarter of the ventricular septum and posterior left ventricular free wall. The LC coronary artery usually perfuses the lateral wall of the left ventricle (defined as that portion of ventricular myocardium located between anterolateral and posteromedial papillary muscles). The basal most portion of the ventricular septum is usually perfused by branches of the PDA. The apical third of the posterior left ventricle may be predominantly perfused by the LAD. LAD artery and its branches supply the right and left bundle branches, and the anterolateral papillary muscle of the left ventricle. When the PDA is provided by the circumflex artery, the entire ventricular septum is vascularized by the left coronary system. The LAD artery can also provide collateral circulation to the anterior right ventricle via the circle of Vieussens, to the posterior ventricular septum by the septal perforators and to the PDA from the distal LAD artery or a diagonal branch. Kogel's artery arises from the proximal RCA or LC or, rarely, the LM; it passes posteriorly into the lower portion of the atrial septum and anastomoses with the AV node artery.

Although the large epicardial coronary arteries are capable of constriction and relaxation, in healthy persons they serve as conduits and are referred to as conductance vessels. They can cause severe ischaemia from constriction in Prinzmetal's angina. The intramyocardial arterioles normally exhibit changes in tone and are therefore referred to as resistance vessels. Abnormal constriction or failure of normal dilation of the coronary resistance vessels can also cause ischaemia. This condition is referred to as microvascular angina.