How ECG leads are positioned

Coronary artery territories The main epicardial coronary arteries supply distinct regions of the myocardium, which can be mapped and assessed during an ultrasound examination. For standardization, the left ventricle (LV) is divided along its long axis into four quadrants: anterior, inferior, septal, and lateral. At the basal and midventricular levels, the septal and lateral walls are further subdivided into anterior and inferior segments. Each wall is then divided in short-axis views into basal, mid, and apical thirds. Beyond the LV cavity, the distal apex forms a cap segment. Altogether, this results in a total of 17 myocardial segments. Most of the heart’s blood supply comes from the left main coronary artery, which divides into the left anterior descending (LAD) and left circumflex (LCx) arteries. The LAD supplies most of the anterior ventricular wall, while its septal branches supply the anterior two-thirds of the interventricular septum. Its diagonal branches supply the anterolateral wall. In some cases, a large LAD may wrap around the apex and supply the distal portion of the inferior wall. The LCx travels in the atrioventricular groove, and its obtuse marginal branches supply the inferolateral wall. The right coronary artery (RCA) supplies the inferior third of the septum and the inferior wall, and it also provides blood to the right ventricle. Adapted from Bulwer BE, Rivero JM, eds. Echocardiography Pocket Guide: The Transthoracic Examination

The schematic illustrates optimal angiographic views to visualize different collateral circulations.

Understanding Angiographic Views for Left Coronary Artery (LCA): Proper angiographic projections are key to visualizing coronary anatomy. Here's how different views help evaluate segments of the Left Main (LM), LAD, and Circumflex (Cx) arteries: 1️⃣ LAO Caudal: "Spider view" best for LM bifurcation, proximal LAD, and Cx. 2️⃣ RAO Caudal: Good separation of LAD & Cx; visualizes mid/distal LAD and OM branches. 3️⃣ LAO Cranial: Best for entire LAD course, septals (S), diagonals (D), and LM. 4️⃣ RAO Cranial: Excellent for LAD and diagonal visualization with clear proximal Cx. These views guide precise intervention planning. Image credit: Dr. Annapoorna Kini, Icahn School of Medicine at Mount Sinai, NY