Impact of body mass index on outcome of Endovascular Thrombectomy with or without Intravenous Alteplase in Acute Stroke in China：A post-hoc Analysis of DIRECT-MT Trial

OBJECTIVE: The impact of body mass index (BMI) on outcomes after mechanical thrombectomy (MT) for large vessel occlusion acute ischemic stroke (LVOS) has been a subject of controversy, mainly due to the so-called "obesity paradox". The obesity paradox refers to the phenomenon where, contrary to expectations, overweight or obese individuals seem to have better clinical outcomes in certain disease states. This study aimed to investigate the relationship between BMI and the clinical prognosis of patients with LVOS treated with endovascular thrombectomy (EVT) combined with or without intravenous alteplase in DIRECT-MT. METHODS: This is a post-hoc analysis of the DIRECT-MT randomized trial. Patients were randomly allocated to undergo EVT after alteplase intravenous thrombolysis (IVT) (IVT+EVT group) or EVT alone (EVT group) at a 1:1 ratio. Among 656 randomized patients, 645 with baseline BMI information were included, The BMI was analyzed as a categorical variable, all patients were categorized according to their BMI into 3 groups: 18.5 ≤ BMI ＜ 24 kg/m2 (normal weight), 24 ≤ BMI＜28 kg/m2 (overweight), BMI ≥ 28 kg/m2 (obese). The primary outcome was the 90-day modified Rankin Scale (mRS) score analyzed as a continuous variable. Multivariable ordinal logistic regression with an interaction term was used to estimate treatment allocation and the BMI subgroups. RESULTS: A total of 645 patients were enrolled in this study, 373 (57.8%) were normal weight, 208 (32.2%) were overweight and 64 (10.0%) were obese. 175 (46.9%) normal weight patients, 114 (54.8%) overweight patients and 31 (48.4%) obese patients underwent direct EVT. Patients in the three groups were statistically different in age (71 versus 68, 66), time from randomization to groin puncture (31 versus 32, 39.5), time from randomization to revascularization (101.5 versus 92, 116), and time from admission to groin puncture (84 versus 83, 98.5). Other baseline and procedural characteristics were comparable. No significant difference for the ordinal mRS or 90 days mortality was observed by BMI [adjusted common odds ratio (acOR) was 0.92 (95% CI 0.64 to 1.32) for normal weight, 1.36 (95% CI 0.83 to 2.22) for overweight, and 1.09 (95% CI 0.45 to 2.64) for obese] and treatment allocation interaction [the adjusted P value for interaction was 0.335 (normal weight versus overweight), 0.761 (normal weight versus obese) and 0.733 (overweight versus obese)]. For the procedural complications and other clinical and imaging outcomes, no significant differences were observed between the BMI and treatment allocation. CONCLUSION: The results demonstrated that BMI had no association with final outcome whether the patient with LVOS underwent EVT alone or plus IVT for Chinese adults. Thus, the obesity paradox does not appear to pertain to EVT alone or plus IVT. Further studies are needed to confirm the finding.