COMPARE OUTCOMES AMONG PATIENTS WHO UNDERWENT CORONARY ARTERY BYPASS GRAFTING IN RELATION TO THEIR BODY MASS INDEX

Abstract

Background: Body mass index (BMI) is an established predictor of cardiovascular risk and has been increasingly recognized as a factor influencing postoperative outcomes following coronary artery bypass grafting (CABG). Although obesity is associated with multiple cardiovascular comorbidities, its impact on postoperative morbidity and mortality remains controversial. Previous studies have reported conflicting findings, with some demonstrating increased postoperative complications among obese patients, while others have described an "obesity paradox," suggesting comparable or even better survival among overweight and obese individuals. This study compared postoperative outcomes among patients undergoing CABG according to different BMI categories.

Methods: A descriptive longitudinal study was conducted at the Department of Cardiothoracic Surgery, Tabba Heart Institute, Karachi. A total of 410 patients aged 55–75 years who underwent elective isolated CABG were enrolled using consecutive sampling. Patients were categorized according to the World Health Organization BMI classification into underweight (<18.5 kg/m²), normal weight (18.5–24.9 kg/m²), and overweight/obese (≥25 kg/m²) groups. Demographic characteristics, perioperative variables, postoperative morbidity, including prolonged hospital stay (>7 days), surgical site infection, cerebrovascular accident (CVA), prolonged mechanical ventilation (>48 hours), postoperative renal dysfunction, and mortality within one month of surgery were recorded. Data were analyzed using IBM SPSS version 17.0. Comparisons between BMI groups were performed using the Chi-square test and Fisher's exact test, with a p-value of <0.05 considered statistically significant.

Results: Among the 410 patients included in the study, the mean age was 63.8 ± 6.4 years, and 298 (72.7%) were male. Of the total participants, 52 (12.7%) were underweight, 183 (44.6%) had normal BMI, and 175 (42.7%) were overweight/obese. Obese patients demonstrated significantly higher rates of prolonged hospital stay (24.0% vs. 12.6%, p=0.008), surgical site infection (13.7% vs. 5.5%, p=0.014), prolonged mechanical ventilation (10.9% vs. 4.9%, p=0.031), and postoperative renal dysfunction (9.1% vs. 3.8%, p=0.039) compared with patients of normal BMI. The incidence of postoperative cerebrovascular accident did not differ significantly among BMI groups (p=0.447). One-month mortality was observed in 14 (3.4%) patients and showed no statistically significant association with BMI category (p=0.618).

Conclusion: Higher BMI was significantly associated with increased postoperative morbidity following CABG, particularly with regard to wound infection, prolonged hospitalization, respiratory complications, and renal dysfunction. However, BMI was not significantly associated with short-term postoperative mortality. These findings suggest that obesity contributes to postoperative complications without adversely affecting early survival after CABG. Careful perioperative optimization and targeted postoperative management of overweight and obese patients may improve clinical outcomes and reduce postoperative morbidity.