Abstract
Background: Electrocardiographic characteristics and diagnostic value of supplementary leads in patients with acute myocardial infarction due to left circumflex artery occlusion. Objectives: To describe the electrocardiographic characteristics and evaluate the diagnostic value of supplementary leads in patients with acute myocardial infarction caused by left circumflex artery occlusion. Methods: A cross-sectional descriptive study was conducted on 81 patients diagnosed with AMI with angiographically confirmed LCx as the culprit lesion. A standard 12-lead ECG and supplementary leads (V7-V9, V3R-V4R) were recorded upon admission. McNemar’s test was utilized to analyze the difference in diagnostic outcomes using paired data. Results: The mean age of the study population was 67.3 ± 13.0 years, with a male predominance (69.1%). Diagnosis based solely on STEMI criteria using the standard 12-lead ECG demonstrated a remarkably low sensitivity of 29.6%. With the addition of posterior leads (V7-V9), the detection rate of ST-segment elevation increased significantly to 61.7%. Discordance analysis revealed that the supplementary recording of V7-V9 successfully and accurately reclassified 33.3% of patients (27 cases) from NSTEMI to STEMI, showing high statistical significance (p < 0.0001; OR = 27). ST-segment elevation in V7-V9 was strongly associated with a mirror-image ST-segment depression in leads V1-V3 (peaking at V3 with a mean depression of −1.38 mm). Furthermore, ST-segment elevation in the right ventricular leads (V3R-V4R) was exceptionally rare (4.9%) and primarily associated with complex multivessel coronary artery disease accompanied by chronic total occlusion (CTO) in other vessels. Conclusion: The standard 12-lead ECG exhibits significant limitations and frequently underdiagnoses AMI due to LCx occlusion. Supplementary recording of V7-V9 leads provides superior diagnostic value, accurately reclassifying 33.3% of patients and establishing a critical basis for initiating urgent reperfusion therapy. Routine recording of 15- or 17-lead ECG is highly recommended in the emergency department setting.
