Introducing a new algorithm in inferior ST-segment elevation myocardial infarction to predict the culprit artery and distinguish proximal versus distal lesions.

OBJECTIVES: Inferior ST-elevation myocardial infarction (I-STEMI) caused by proximal occlusion of the left circumflex artery (LCx) or right coronary artery (RCA) is associated with poor outcomes. We tested two new electrocardiographic (ECG) algorithms to identify proximal RCA (P-RCA), proximal LCx (P-LCx), or distal RCA or LCx in I-STEMI.

METHODS: In 135 patients with I-STEMI, 115 (85.2%) had RCA occlusion [49 (36.3%) with P-RCA occlusion] and 15 (11.1%) had LCx occlusion [4 (2.9%) with P-LCx occlusion]. In the ECG algorithms, P-RCA occlusion was indicated by STE in lead III higher than lead II and no ST depression in V₁. P-LCx occlusion was indicated by STE in lead II higher than in lead III and no ST depression in aVL. One algorithm included an additional step: whether the ST-T pattern in aVL represents reciprocal changes to lead III (differences in the magnitude of ST deviation or T-wave direction were considered to indicate P-LCx occlusion).

RESULTS: The positive and negative predictive values of these algorithms were low (45.6 and 76.8% for P-RCA occlusion and 6.7 and 97.5% for P-LCx occlusion).

CONCLUSION: The ECG algorithms cannot reliably identify the culprit artery in I-STEMI. Right precordial leads may be needed to determine the site of lesion.