Background: Venoarterial Extracorporeal Membrane Oxygenation (VA-ECMO) is used to support patients with cardiac and respiratory failure. The relationship between obesity and VA-ECMO outcomes is unknown.

Objectives: To determine the relationship between all-cause mortality and morbidity in patients treated with VA-ECMO, and to further assess whether this relationship is mediated via patient factors, complications, or treatments.

Methods: Using the ELSO Registry, VA-ECMO runs from 2015 to 2021 were retrospectively analyzed. The patient demographics, ECMO indication and complications for survivors and decedents were univariately compared. Logistic regression with fractional polynomials was then used to elucidate the relationship between body mass index (BMI) of VA-ECMO patients to both mortality and complications.

Results: 22,825 VA-ECMO runs met inclusion criteria for analysis. The mean BMI for survivors is 28.4 +/- 6.5 kg/m2. The mean BMI for decedents is 29.5 +/- 6/9 kg/m2. BMI was significantly associated with mortality (P <.001), with the odds of mortality increasing with increasing BMI. 47% of underweight patients died, progressing to 50% for normal range, to 53%, 56%, 58%, and 65% for preobese, Class-1, Class-2, and Class-3 obese patients respectively. Relative to a BMI of 25, a BMI of 35 had an odds ratio of 1.15 (1.09; 1.18), and a BMI of 45 an odds ratio of 1.46 (1.25; 1.57). BMI was significantly associated with increased mechanical, cardiovascular, pulmonary and renal complications.

Conclusions: In patients undergoing VA-ECMO, increasing BMI was associated with increasing all-cause mortality and complications. The odds of mortality increased as BMI increased.