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.