Electrocardiographic findings during balloon angioplasty of the left circumflex coronary artery – influence of location of the ischemic segments with respect to the obtuse margin of the left ventricle

Background Acute left circumflex coronary artery (LCx) occlusion is not easily detected by the standard 12-lead electrocardiogram (ECG). Methods In 16 patients continuous ECG recording was performed during balloon occlusion. The treated lesions were divided into proximal and distal based on the location of the ischemic segments with respect to the left obtuse margin of the heart. Results Mean ΔST (=ST amplitude during inflation - pre-inflation ST) ≥0.5 mm in both leads I and aVL predicted a proximal occlusion site with sensitivity of 62.5% (95% confidence interval [CI] 24.9–91.5%), specificity 100% (95% CI 63.1–100%), positive predictive value 100% (95% CI 47.8–100%), and negative predictive value 72.7% (95% CI 39–94%). In lead III, mean ΔST was +0.3 mm in the distal and −0.2 mm in the proximal group, respectively (p = 0.036). Conclusions ST elevation in leads I and aVL is associated with myocardial ischemia at or proximal to the left obtuse margin.