Impact of Body Weight on Atrial Fibrillation Recurrence and Adverse Clinical Events After Ablation　― Peculiarity in Japanese Patients―

Pulmonary vein isolation is a first-line catheter ablation therapy for atrial fibrillation (AF),¹ and is performed even in patients over 75 years old. Recent developments in both techniques and mapping systems have improved the effectiveness and safety of ablation.² Catheter ablation therapy for AF relieves symptoms and reduces the incidence of cardiovascular events, including heart failure and cerebral infarction.^3–5 However, the clinical factors involved in AF recurrence and the incidence of adverse clinical events (AEs) following catheter ablation are unclear.

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In this issue of the Journal, Watanabe et al⁶ describe the major determinants of both AF recurrence and the incidence of AEs after catheter ablation therapy for AF based on an analysis of retrospective multicenter Japanese registry data. Multivariate analysis revealed that female sex, persistent and long-lasting AF, and enlarged left atrial diameter (LAD) were significantly associated with AF recurrence (Figure 1, Left panel). On the other hand, age ≥75 years, low body weight (BW; <50 kg), diabetes, vascular disease, left ventricular dysfunction (ejection fraction <40%), enlarged LAD (≥44 mm), and renal dysfunction (creatinine clearance (CrCL) <50 mL/min) were independently associated with the incidence of AEs (Figure 1, Right panel). Furthermore, the association between post-ablation AF recurrence and the incidence of AEs was absent after adjusting for other relevant factors. Taken together, these results suggest that the mechanism of AE occurrence after catheter ablation may differ from that of AF recurrence.

Figure 1.

Main results from Watanabe et al.⁶ AF, atrial fibrillation; CrCL, creatinine clearance; EF, ejection fraction; LAD, left atrium diameter.

The BW of patients undergoing AF ablation differs greatly between Japan and Western countries. Japanese AF patients generally have low BW, especially elderly patients, whereas a large number of Western AF patients are obese. A recent worldwide meta-analysis demonstrated that obesity (body mass index (BMI) ≥28 kg/m²) was associated with higher AF recurrence and possibly with the incidence of AEs after catheter ablation (Figure 2, Left panel).⁷ However, whether BW is associated with AF recurrence and the incidence of AEs after catheter ablation in Japanese patients remains unclear. In this regard, Watanabe et al⁶ report an interesting finding. According to their univariate analysis of Japanese patients, BW ≥80 kg was a predictor of AF recurrence, whereas a BW <50 kg was an independent predictor of AEs (Figure 2, Right panel). The number of Western patients with low BW who undergo AF ablation is small, and the meta-analysis did not describe the results of patients whose BMI indicated low weight (<20 kg/m²).⁷ In the J-RHYTHM Registry study, which registered Japanese patients with nonvalvular AF, Inoue et al found that low BW was associated with higher risks of all-cause and cardiovascular death compared with normal BW.⁸ Interestingly, in a study conducted in the USA, Bunch et al.⁹ reported that catheter ablation therapy in AF patients with low BW reduced the risk of AF recurrence compared with obese patients, but the risk of negative cardiovascular outcomes, such as increased risk of stroke, remained high despite the lower AF burden. However, the study included 1,558 patients, and only 30 of them (1.9%) had low BW (i.e., BMI ≤20 kg/m²). In Japan, patients with low BW are often elderly and female, who also have reduced CrCL, blood hemoglobin, and muscle mass, all of which are all well-known risk factors for major bleeding, cardiovascular events, and high mortality in patients with AF.

Figure 2.

Difference in the impact of body weight on AF recurrence and the incidence of adverse clinical events after AF ablation by Pranata et al⁷ vs. Watanabe et al.⁶ AF, atrial fibrillation; BMI, body mass index.

Again, the impact of BW on AF recurrence and the incidence of AEs differs greatly between Japan and Western countries. In the latter, patients with BMI ≤20 kg/m² are rare. In Japan, the BMI of a virtual patient who is 150 cm tall and weighs 40 kg is 17.8 kg/m², and many lean patients undergo AF ablation. The results reported by Watanabe et al⁶ are noteworthy because they clarify that high BMI patients are at risk of AF recurrence, whereas low BMI patients are at risk of AEs after catheter ablation in Japan. Therefore, obese AF patients should be educated about the importance of reducing BW before catheter ablation therapy, and careful treatment to avoid AEs is needed when performing catheter ablation in lean AF patients.

Conflict of Interest

None.

Disclosure

N.T. is a member of Circulation Journal’s Editorial Team.

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