Risk factor paradox in STEMI-related sudden cardiac arrest

Abstract Background Cardiovascular risk factors (CVRF) are associated with an increased risk of atherosclerosis and ST-segment elevation myocardial infarction (STEMI). Sudden cardiac arrest (SCA) is currently the most feared complication of STEMI. The impact of CVRF on the rate of SCA is still unknown. Purpose To assess the association between CVRF and pre-hospital SCA during acute STEMI. Methods Data were taken between 2006 and 2014 from the e-MUST study that enrolls all STEMI managed by EMS in the Greater Paris Area, including those dead before hospital admission. Characteristics of patients who presented SCA were compared to those of patients who did not, and multivariable logistic regression was developed including all variables that differed between the two groups, in order to identify characteristics associated with an increased risk of SCA. Results Over the study period, 13,253 STEMI patients were included (median age 60.1 [51.4 - 73.0], 78.1% males). Among them, 7,513 patients (58.1%) had ≥2 CVRF, 3,979 (30.8%) had 1 CVRF, and 1,432 (11.1%) did not present any CVRF. Pre-hospital SCA witnessed by emergency medical services occurred in 749 (5.6%) patients. SCA victims were younger compared to the non-SCA group (58.0 vs. 60.3 years (P<0.001), with a higher proportion of patients without known CVRF (17.2 vs. 10.7%, P<0.001). There was no statistical difference in sex ratio (77.5% vs. 78.2%, P=0.69) and presence of past history of coronary artery disease (18.7% vs. 19.5%, P=0.56). Patients with ≥2 CVRF had the lowest rate of SCA (4.6%), while the highest SCA rate occurred among patients without CVRF (8.9%). On multivariate analysis, the presence of ≥2 CVRF was associated with a twice-lower risk of SCA (OR 0.52, 95% CI 0.41–0.65, P<0.001, when the group without risk factors was taken as a reference group). Conclusion The prevalence of CVRF is high among patients presenting STEMI. However, once STEMI has occurred, presence of CVRF is associated with a lower rate of SCA per STEMI, creating a risk factor paradox in STEMI-related SCA.