Paradox of Low Body Mass Index

Low BMI has been reported to be associated with atrial fibrillation (AF) recurrence post-ablation, as well as with cardiovascular events and mortality. However, the previous studies have not fully accounted for baseline factors including age, nutritional status, anemia, and cardiac function. Thus, the potential risks inherent in patients with AF and low BMI remain unclear. AF patients who underwent primary ablation were enrolled. To exclude the effect of baseline factors including age, nutritional status, anemia and cardiac function, propensity score-matching was performed. The incidence of composite of heart failure (HF) hospitalization and all-cause death among the patients stratified by BMI was investigated. We finally analyzed 2396 patients. Low BMI was defined as < 18.5 kg/m² and normal/high BMI as ≥ 18.5 kg/m². The low and normal/high BMI groups consisted of 120 patients after 1:1 propensity score-matching, respectively. In propensity score-matched population, normal/high BMI had higher risk of late arrhythmia recurrence post-ablation than low BMI in persistent AF, while no significant difference in paroxysmal AF. Kaplan-Meier analysis showed incidence of the composite endpoint was significantly higher in patients with low BMI than those with normal/high in the overall and propensity score-matched populations (Log-rank P < 0.001 and P = 0.024, respectively). Cox proportional hazard analysis revealed low BMI had significantly and independently higher risk of the composite endpoint (HR = 2.43; 95% CI = 1.098-5.374). Despite a lower recurrence rate, patients with low BMI showed a paradoxically higher incidence of HF hospitalization and all-cause mortality, highlighting the need for further investigation into potential interventions targeting low BMI patients.