Effect of obesity in minimally invasive mitral valve surgery

Obesity has tripled worldwide over the past 50 years. Existing evidence depicts conflicting relationships between body mass index and operative risk in cardiac surgery. Some large analyses have showed a shaped relationship between obesity and peri-operative mortality; others have found an inverse relationship, a so-called obesity paradox.

We aimed to outline the effects of obesity on early outcome in minimally invasive mitral valve (MV) surgery.

One-thousand-seven-hundred-twenty consecutive patients who underwent mini-thoracotomy MV surgery at a single tertiary care academic centre since 2006 were retrospectively analysed. Multivariable logistic regression served to identify predictors of 30-day outcomes.

Obesity (n=149/1695, 8.8%) was predictive of 30-day mortality (5.4% vs. 1.8%; p=0.010; odds ratio [OR] 3.14, 95% CI 1.36-7.27), but not when excluding patients with associated coronary and/or extracardiac arteriopathy (n=255/1695, 15%). Conversely, obesity was the sole predictor of death in this subgroup (4.3% vs. 1.9%; p=0.015; OR 3.65, 95% CI 1.01-13.17). Other predictors in the entire cohort were age, creatinine, reoperation and arteriopathy. Obese patients had more comorbidities and less degenerative MV prolapse, and parallel higher probability of MV replacement (p<0.001). Cardiopulmonary bypass time, but not cardioplegic arrest time, was longer (p=0.007). Morbidity, primarily driven by respiratory and wound complications, was also higher, with longer intensive care and hospital length-of-stay (p<0.001).

Obesity confers additional operative risk in MV surgery despite a minimally invasive approach. However, increased risk is confined to patients with concomitant arteriopathy and atherosclerotic burden, for whom weight loss is advisable in a nonurgent scenario.