SMuRF-less ST-segment elevation myocardial infarction in contemporary Japanese practice: Clinical characteristics and prognostic implications from the Japan acute myocardial infarction registry

Background: Standard modifiable cardiovascular risk factor (SMuRF)-less myocardial infarction, defined as the absence of diabetes, dyslipidemia, hypertension, and smoking, may have different clinical implications in East Asian patients because coronary pathophysiology and preventive treatment patterns differ from those in Western populations. We hypothesized that SMuRF-less ST-elevation myocardial infarction (STEMI) is associated with poorer outcomes despite contemporary primary percutaneous coronary intervention (PCI). Methods: A total of 2310 STEMI patients (Male/Female: 1759/551; mean age: 67.2 years) from the Japan AMI Registry were stratified by SMuRF status and followed for one year. The primary endpoint was major adverse cardiovascular events (MACE), defined as cardiovascular death, non-fatal myocardial infarction, and non-fatal stroke. Results: Among eligible patients, 136 (5.9%) were SMuRF-less. Compared with SMuRF-positive patients, SMuRF-less patients were older, more often female, had lower body mass index, and a higher prevalence of atrial fibrillation. Despite similarly high primary PCI use, evidence-based secondary preventive therapies at discharge were less frequently prescribed in SMuRF-less patients. During a median follow-up of 358 days, MACE occurred more frequently in the SMuRF-less group (log-rank P < 0.01), and landmark analysis showed excess risk beyond the acute phase (log-rank P = 0.03). After adjustment for established prognostic factors, SMuRF-less status remained associated with unfavorable outcomes. A sex-stratified analysis suggested a more pronounced adverse association in men. An exploratory sex-stratified analysis suggested a more pronounced association in men. Conclusions: In the contemporary primary PCI era, Japanese SMuRF-less STEMI patients represent a distinct high-risk phenotype characterized by lower implementation of secondary preventive therapies and poorer 1-year outcomes extending beyond the acute phase.