This is an angiogram of a left coronary artery (LCA). The circumflex artery, labelled CX, is dominant, meaning that it connects to the posterior descending artery and perfuses the posterior and inferior walls of the left ventricle. Approximately 15-18% of the population has a dominant circumflex artery. In about 80-85% of people, the right coronary artery (RCA), perfuses the inferior wall.
This ECG was obtained from a patient who suffered an obstruction of the circumflex coronary artery. Unfortunately, he was in the approximately 15-18% of the population in whom the circumflex artery is dominant. That means that it connects with the posterior descending artery, perfusing not only the lateral wall of the left ventricle, but also the posterior and inferior walls. In this case, the obstruction is in the midportion of the artery, and the high lateral wall is spared.
This ECG is from an 81 year old woman with an extensive history of coronary artery disease. She was experiencing chest pain at the time of the ECG. We can clearly see ST elevation in Leads II, III, and aVF, indicating an inferior wall ST-elevation M.I. (STEMI). There are reciprocal ST depressions in Leads I and aVL. There are subtle and less specific ST changes in V1 (flat ST and T), V2 (ST depression), V3 (ST elevation and inverted T wave), and V4 through V6 (slight ST elevation).
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