Anterior STEMI mimic: Isolated right ventricular infarction secondary to proximal RCA occlusion.

Anterior ST-segment elevation is conventionally attributed to acute occlusion of the left anterior descending (LAD) artery. However, isolated right ventricular myocardial infarction (RVMI), though exceedingly rare, may present with a similar electrocardiographic pattern, thereby posing a diagnostic challenge. We describe a 44-year-old male patient who presented with acute retrosternal chest pain and exhibited dome-like ST-segment elevation in leads V1-V4, without reciprocal ST-segment depression in the inferior leads. Despite initial suspicion of anterior ST-elevation myocardial infarction (STEMI) due to presumed LAD involvement, emergent coronary angiography revealed a complete proximal occlusion of the right coronary artery (RCA), which gave rise to a well-developed posterior descending artery (PDA) following recanalization, alongside a small PDA from the left circumflex artery, consistent with a balanced-dominant coronary circulation. A diagnosis of isolated RVMI was subsequently confirmed. This case emphasizes the need to consider RVMI in the differential diagnosis of anterior ST-segment elevation, particularly in patients with balanced-dominant anatomy, where dual-PDA supply may obscure classic inferior infarct patterns and lead to diagnostic confusion.