Which is the culprit artery?

A 59-year-old woman had been treated at another hospital for unstable angina for 5 days. One day after discharge , she returned with prolonged chest pain, and an electrocardiogram was recorded (Figure 1). The most notable features of the electrocardiogram are ST and T changes in leads V 1 through V 4. Superficially, these changes suggest a left anterior descending lesion with anterior subendocar-dial ischemia and/or injury, but closer inspection indicates otherwise. Minimal ST-segment elevation and slight terminal T-wave inversion are seen in lead III, and the reciprocal of these changes is noted in aVL, where ST depression and a negative/positive diphasic T wave are apparent. Thus, there is evidence of trans-mural inferior injury (1). A second look at V 2 through V 4 sug-Figure 1. The electrocardiogram recorded on the patient's second admission. gests ST depression and negative/positive diphasic T waves similar to those seen in aVL, implying that these changes are reciprocal to ST elevation and slight terminal T-wave inversion over the posterior wall of the left ventricle. Thus, the electrocardiogram indicates not anterior but posterior and inferior transmural injury. Either right or left circumflex coronary artery occlusion can produce posterior and inferior injury. Because the ST and T changes are most marked in V 1 through V 4 and because these changes are typical of left circumflex occlusion, that seems the likely culprit (2, 3). The ST is depressed in aVL, suggesting that the lesion is distal to the first obtuse marginal branch. Angio-grams made 4 days later at The Medical Center of Louisiana in New Orleans show complete occlusion of the left circumflex dis