Obesity paradox and perioperative myocardial infarction/injury in non-cardiac surgery.

Background: The impact of obesity on the incidence of perioperative myocardial infarction/injury (PMI) and mortality following non-cardiac surgery is not well understood.

Methods: We performed a prospective diagnostic study enrolling consecutive patients undergoing non-cardiac surgery, who were considered at increased cardiovascular risk. All patients were screened for PMI, defined as an absolute increase from preoperative to postoperative sensitive/high-sensitivity cardiac troponin T (hs-cTnT) concentrations. The body mass index (BMI) was classified according to the WHO classification (underweight< 18 kg/m, normal weight 18-24.9 kg/m, overweight 25-29.9 kg/m, obesity class I 30-34.9 kg/m, obesity class II 35-39.9 kg/m, obesity class III > 40 kg/m). The incidence of PMI and all-cause mortality at 365 days, both stratified according to BMI.

Results: We enrolled 4277 patients who had undergone 5413 surgeries. The median BMI was 26 kg/m (interquartile range 23-30 kg/m). Incidence of PMI showed a non-linear relationship with BMI and ranged from 12% (95% CI 9-14%) in obesity class I to 19% (95% CI 17-42%) in the underweight group. This was confirmed in multivariable analysis with obesity class I. showing the lowest risk (adjusted OR 0.64; 95% CI 0.49-0.83) for developing PMI. Mortality at 365 days was lower in all obesity groups compared to patients with normal body weight (e.g., unadjusted OR 0.54 (95% CI 0.39-0.73) and adjusted OR 0.52 (95% CI 0.38-0.71) in obesity class I).

Conclusion: Obesity class I was associated with a lower incidence of PMI, and obesity in general was associated with a lower all-cause mortality at 365 days.