Abstract Body (Do not enter title and authors here): INTRODUCTION: Smoking and air pollution produce carbon monoxide (CO), which sharply reduces blood oxygen carrying capacity and may worsen myocardial infarction (MI). We aimed to assess the prognostic value of expiratory CO level in patients hospitalized for MI.
METHODS: In this prospective nation-wide cross sectional study, expiratory CO levels were measured upon admission in consecutive patients hospitalized for MI across 39 centers. In accordance with previous studies, a CO threshold of 11 ppm was defined to classify patients as low or high CO level. The primary outcome was in-hospital major adverse events (MAEs: death, severe ventricular arrythmia, cardiogenic shock and mechanical ventilation). The secondary outcomes were 1-year MACEs (cardiovascular death and recurrent MI) and 1-year all-cause mortality. The importance of CO in determining events was stratified using machine learning (ML) analysis.
RESULTS: Among 717 patients (64±13 years; 75% males; 33% active smokers; 43% ST elevation MI), 11% of the population had elevated expiratory CO level (> 11 ppm). Among patients with CO > 11 ppm, there was a significant trend between CO level and rate of in-hospital MAEs (10% in the 1st tertile and 55% in the 3rd tertile of elevated CO levels; p for trend=0.002; Figure 1). After adjustment for confounders, including smoking status, elevated CO levels were independently associated with a significant increase in MAEs: odds ratio (OR) [95% confidence interval]: 7.5 [3.5-16.7] adjusting for comorbidities, 14.0 [6.1-33.3] for parameters of in-hospital severity, and 12.7 [5.6-29.6] for respiratory parameters. Elevated CO levels were associated with 1-year MACEs and all-cause deaths after adjustment for confounders (Figure 2). No significant differences in coronary angiographic characteristics were noted in patients with elevated CO levels. ML analysis showed that elevated CO level was the most ranking predictor of MAEs as well as one of the best predictors of 1-year MACEs and all-cause mortality (Figure 3). When CO was compared to the predictive value of the parameters used to calculate the GRACE score in our population, it ranked as the strongest predictor of in-hospital events.
CONCLUSION: This is the first prospective study to show that elevated expiratory CO levels upon admission were associated with a significant increase in in-hospital MAEs, 1-year MACEs and all-cause mortality in patients with MI. ML analysis ranked CO as a powerful predictor of these events.