The enigma of the ‘smoker's paradox’: Results from a single-center registry of patients with STEMI undergoing primary percutaneous coronary intervention

Smoker's paradox usually refers to the observation of a favorable outcome of smoking patients in acute myocardial infarction. From April 2006 to December 2018 a population of 2456 patients with ST segment elevation myocardial infarction (STEMI) treated with primary percutaneous coronary intervention (pPCI) were prospectively enrolled in the MATRIX registry. Ischemic time, clinical, demographics, angiographic data, and 1-year follow-up were collected. Among 2546 patients admitted with STEMI, 1007 (41 %) were current smokers. Smokers were 10 years younger and had lower crude in-hospital and 1-year mortality (1.5 % vs 6 %, p < 0.0001 and 5 % vs 11 %, p < 0.0001), shorter ischemic time (203 147–299 vs 220 154–334 minutes, p = 0.002) and shorter decision time (60 30–135 vs 70 36–170 minutes, p = 0.0063). Smoking habit OR:0.37(95 % CI:0.18–0.75)-p < 0.01, younger age OR 1.06 (95%CI:1.04–1.09)-p < 0.001 and shorter ischemic time OR:1.01(95%CI:1.01–1.02)-p < 0.05 were associated to lower in-hospital mortality. Only smoking habit HR:0.65(95 % CI: 0.44–0.9)–p = 0.03 and younger age HR:1.08 (95%CI:1.06–1.09)–p < 0.001 were also independently associated to lower all-cause death at 1-year follow-up. After propensity matching, age, cardiogenic shock and TIMI flow <3 were associated with in-hospital mortality, while smoking habit was still associated with reduced mortality. Smoking was also associated with reduced mortality at 1-year follow-up (HR 0.54, 95 % CI 0.37–0.78; p < 0.001). Smoking patients show better outcome after PCI for STEMI at 1-year follow-up. Although "Smoking paradox" could be explained by younger age of patients, other factors may have a role in the explanation of the phenomenon.