Patients without conventional modifiable risk factors (SMuRFless) presenting with obstructive myocardial infarction face a significantly higher 30-day mortality

Abstract Background Patients with myocardial infarction (MI) who lack standard modifiable cardiovascular risk factors (SMuRFs), despite the absence of hypertension, diabetes mellitus, dyslipidaemia, or smoking, have higher early mortality. This disparity may occur for various reasons including unidentified pathophysiological mechanisms, emphasising the need to clarify modifiable factors. Methods Between June 2010 and October 2021, we prospectively studied 2,992 consecutive patients with ECG transmissions meeting Glasgow Algorithm (GA) for STEMI at Liverpool Hospital, Sydney. Patients were classified as SMuRFless if they lacked hypertension, hyperlipidaemia, diabetes mellitus, and smoking, and as SMuRF-positive if one or more were present. Baseline clinical, laboratory, and procedural data were extracted from the cardiology database. STEMI was adjudicated according to the 4th Universal definition of MI (4UDMI) and masquerading STEMI was defined as being GA positive but not meeting 4UDMI criteria. Thirty-day, two- and five-year mortality was evaluated using Kaplan–Meier survival analysis, and group differences were assessed by the log–rank test. A multivariable Cox proportional hazards model, adjusted for age and gender, was used to identify independent predictors of mortality (p 0.05 considered significant). Results Of the cohort, 1,439 (49%) patients had Masquerading STEMI and 1,553 (51%) had STEMI adjudicated. In the Masquerading STEMI group, 16.1% were SMuRFless compared with 11.5% in STEMI; SMuRFless patients were younger and had fewer prior interventions. Among SMuRFless patients, Masquerading STEMI was associated with higher 30-day survival compared to those with STEMI (99.1% vs 94.0%, p = 0.008), but not at 1 year (97.7% vs 94.0%, p = 0.08) or 5 years (95.7% vs 92.6%, p = 0.25). Conversely, in patients with ≥1 conventional risk factor, Masquerading STEMI had similar 30-day survival to STEMI (96.9% vs 97.7%, p = 0.22) but lower survival at 1 year (91.1% vs 96.3%, p 0.001) and 5 years (77.3% vs 91.9%, p 0.001). In SMuRFless patients, univariate analysis showed that STEMI conferred a substantially higher hazard of 30-day mortality (HR 6.62 95% CI 1.45–30.2, p = 0.015); this association persisted after adjustment for age and sex (HR 13.5 95% CI 1.71–107, p = 0.013). Conclusion Our study shows SMuRF-less MI patients have higher 30-day mortality compared with those possessing conventional risk factors. Further studies need to elucidate the ‘biological drivers’ of SMuRFless MI to facilitate targeting interventions that improve outcomes.