Body mass index and outcomes of in-hospital ventricular tachycardia and ventricular fibrillation arrest

Background: Due to higher transthoracic impedance, obese patients may be less likely to be successfully defibrillated from ventricular tachycardia or ventricular fibrillation (VT/VF) arrest. However, the association between patient body mass index (BMI), defibrillation success, and survival outcomes of VT/VF arrest are poorly understood. Methods: We evaluated 7110 patients with in-hospital VT/VF arrest at 286 hospitals within the Get With The Guidelines^®-Resuscitation (GWTG-R) Multicenter Observational Registry between 2006 and 2012. Patients were categorized as underweight (BMI < 18.5 kg/m²), normal weight (BMI 18.5-24.9 kg/m²), over-weight (BMI 25.0-29.9 kg/m²), obese (BMI 30.0-34.9 kg/m²), and extremely obese (BMI ≥ 35.0 kg/m²). Using generalized linear mixed regression, we determined the risk-adjusted relationship between BMI and patient outcomes while accounting for clustering by hospitals. The primary outcome was successful first shock defibrillation (a post-shock rhythm other than VT/VF) with secondary outcomes of return of spontaneous circulation, survival to 24 h, and survival to discharge. Results: Among adult patients suffering VT/VF arrest, 304 (4.3%) were underweight, 2061 (29.0%) were normal weight, 2139 (30.1%) were overweight, and 2606 (36.6%) were obese or extremely obese. In a risk-adjusted analysis, we observed no interaction between BMI and energy level for the successful termination of VT/VF with first shock. Furthermore, the risk-adjusted likelihood of successful first shock termination of VT/VF did not differ significantly across BMI categories. Finally, when compared to overweight patients, obese patients had similar risk-adjusted likelihood of survival to hospital discharge (odds ratio 0.786, 95% confidence interval 0.593-1.043). Conclusions: There was no significant difference in the likelihood of successful defibrillation with the first shock attempt among different BMI categories.