The impact of body mass index on short- and long-term mortality in cardiac valve surgery: A systematic review

INTRODUCTION: Obesity poses a growing challenge in cardiac valve surgery. Although traditionally regarded as a risk factor, evidence suggests a paradoxical association between elevated body mass index (BMI) and lower short-term surgical mortality, known as the "Obesity Paradox." Its validity in isolated valvular procedures remains insufficiently investigated.

Method

A systematic review was conducted following PRISMA 2020 guidelines, with a comprehensive search across CENTRAL, MEDLINE, PubMed, VHL, and SciELO databases (January 2016 to July 2025). Studies comparing mortality between overweight/obese patients (BMI ≥25 kg/m²) and normal-weight individuals undergoing valve surgery were included. Risk of bias was assessed using the Newcastle-Ottawa Scale, certainty of evidence was evaluated with the GRADE approach, and a narrative synthesis was performed following SWiM guidelines.

Results

Twenty-three studies comprising over 100,000 patients were included. Short-term mortality (≤30 days) was consistently lower among overweight and mildly obese patients, particularly in aortic valve procedures (risk reduction of 19–44%). In mitral surgery, findings were heterogeneous, with similar mortality but higher rates of acute kidney injury in obese patients. Long-term outcomes (>5 years) showed attenuation or reversal of the paradox, with mortality rates converging, especially when metabolic comorbidities were present.

Discussion

The perioperative benefit is mediated by metabolic reserve and the cardioprotective endocrine profile of adipokines. Minimally invasive techniques have eliminated elevated BMI as a technical contraindication, reducing infection-related complications. Over time, chronic low-grade inflammation and composite cardiovascular risk reverse the paradox, particularly in severe obesity associated with diabetes and smoking.

Conclusion

The Obesity Paradox in valvular surgery is a strictly timedependent phenomenon. Elevated BMI should not contraindicate surgical intervention but requires rigorous long-term metabolic monitoring to preserve perioperative survival benefits.