Protective effect of AF ablation on the renal function
Previously, several studies examined the protective effect of AF ablation on the renal function8,10,21. Takahashi et al.10 evaluated the change in the eGFR after AF ablation and reported that the eGFR increased three months after CA and was maintained until one year in patients free from AF recurrence, whereas the eGFR decreased over one year in patients with AF recurrences. In the present study, the HCM patients who underwent AF ablation had the maintenance of their renal function, however, the HCM patients without CA had a decrease in their eGFR over one year of follow-up. The number of patients, in whom pharmacotherapy changed during the study, was small in both groups and the incidence of hospitalizations due to heart failure did not differ between the two groups. These data indicated that those factors did not influence the change in the eGFR in this study. Therefore, we considered that the maintenance of the renal function was achieved by AF ablation. The mechanism of the protective effect of AF ablation on the renal function has been discussed in previous studies10,21. The improvement in the atrial contractile function after a successful ablation will increase the cardiac output, leading to the protection of renal function. An echocardiography and MRI study showed that a successful AF ablation was associated with LA reverse remodeling and LA functional recovery22,23. As an impaired LA function is associated with cardiovascular hospitalizations in patients with heart failure with a preserved ejection fraction24, the LA dysfunction may have a significant negative impact on the renal function in patients with HCM.
In the present study, another independent predictor of renal function improvement (increased eGFR) was a lower LVEF at baseline. The reason for the baseline lower LVEF predicting the renal function improvement remains unsolved. An elevation of central venous pressure, which is observed in patients with impaired LV systolic function and heart failure, lowers the gradient in the pressure across the arteries and veins of the kidneys which eventually reduces the renal function25,26. As CA of AF is associated with LVEF improvement27, the AF ablation might have lowered the central venous pressure and had a positive effect on renal function. The patients with reduced LVEF at baseline may receive more benefit from AF ablation than patients with normal LVEF. However, the data supporting the decrease in the renal venous pressure after the ablation was lacking in the present study.