BACKGROUND: Right-sided ST-segment elevation is typically associated with inferior myocardial infarction; however, the clinical significance of synthesized right-sided ECG leads in anterior ST-segment elevation myocardial infarction (STEMI) remains unclear. AIMS: This study investigated the clinical implications of ST-segment elevation in the synthesized V4R lead in patients with anterior STEMI undergoing primary percutaneous coronary intervention (PCI). METHODS: We retrospectively analyzed patients with anterior STEMI who underwent primary PCI and had synthesized right-sided ECG leads recorded on admission. Patients were classified according to the presence or absence of ST-segment elevation in synthesized V4R. Clinical characteristics, angiographic findings, and in-hospital outcomes were compared between groups. RESULTS: Patients with synthesized V4R ST-segment elevation exhibited significantly higher peak creatine kinase levels, indicating larger infarct size. They also had a higher incidence of ventricular tachyarrhythmias and cardiogenic shock requiring mechanical circulatory support. In an additional stratified analysis limited to patients with higher peak creatine kinase levels, ventricular arrhythmias and cardiogenic shock remained more frequent in the V4R-positive group despite comparable peak creatine kinase levels and left ventricular ejection fraction between groups. Furthermore, a right ventricular branch originating from the left anterior descending artery was more frequently observed in patients with V4R elevation. CONCLUSIONS: Synthesized V4R ST-segment elevation in anterior STEMI is associated with larger infarct size and an increased risk of ventricular tachyarrhythmias and cardiogenic shock. This finding may help identify patients who are particularly vulnerable to acute electrical and hemodynamic instability during the early phase of myocardial infarction.
Watanabe et al. (2026) studied this question.