In‐Hospital Outcomes in Patients With Acute Myocardial Infarction and No Standard Modifiable Cardiovascular Risk Factors Across Varying Body Mass Index: Findings From the CCC‐ACS Project

Background Individuals who present with acute myocardial infarction in the absence of standard modifiable cardiovascular risk factors (ie, SMuRF‐less) seem to have a significantly increased risk of mortality; however, it remains unclear whether the “SMuRF paradox” would be influenced by patients' baseline body mass index (BMI) status. Methods Using data from the CCC‐ACS (Improving Care for Cardiovascular Disease in China–Acute Coronary Syndrome) project from November 2014 to July 2019, we analyzed patients with acute myocardial infarction with and without SMuRFs and categorized their BMI as underweight (<18.5 kg/m 2 ), normal weight (18.5–24 kg/m 2 ), overweight (24–28 kg/m 2 ), and obese (>28 kg/m 2 ). The primary outcome was in‐hospital all‐cause mortality. Multivariable logistic regression models were used to estimate BMI‐stratified associations between SMuRF‐less status and outcomes. Results The study included 44 538 patients with first‐presentation acute myocardial infarction, of whom 4454 were SMuRF‐less. The incidence of SMuRF‐lessness declined from 16.2% to 6.5% as BMI increased by category, and it prevailed more frequently among women and older people regardless of their BMI status. Patients who were SMuRF‐less had a significant increase in in‐hospital mortality than patients with ≥1 SMuRF (adjusted odds ratio [OR], 1.750 [95% CI, 1.057–2.896], P <0.001). The highest mortality rate was observed in the group who were SMuRF‐less and underweight (3.5%). Considering patients with ≥1 SMuRF and obesity as the reference group, the group who were SMuRF‐less underweight exhibited the highest increase in mortality (adjusted OR, 3.854 [95% CI, 2.130–6.973], P <0.001). Conclusions Among patients with first‐presentation acute myocardial infarction, compared with those with ≥1 SMuRF, patients who were SMuRF‐less have a significantly higher risk of in‐hospital mortality, especially in those underweight, whereas in‐hospital survival was the most favorable among patients with ≥1 SMuRF and obesity. Registration URL: https://www.clinicaltrials.gov ; Unique identifier: NCT0230661.