We would like to thank Dr. Guo and his colleagues for their kind interest in our manuscript [1,2]. Several mechanisms may be responsible for impaired endothelial function in the context of atrial fibrillation (AF). Noris et al. [3] reported that the magnitude and dynamic nature of fluid shear stress have a major influence on endothelial cell nitric oxide (NO) synthesis. Laminar shear stress associated with sinus rhythm dose-dependently upregulates NO synthesis by cultured endothelial cells, whereas turbulent shear stress characteristic of AF has no effect on NO synthetic pathways. Minamino et al. [4] demonstrated that plasma levels of nitrite/nitrate and platelet cyclic guanosine monophosphate (cGMP) levels were decreased in patients with AF in association with the presence of abnormalities in hemostatic conditions. Furthermore, endothelial function improved after restoration of sinus rhythm from AF. Takahashi et al. [5] confirmed that endothelium-dependent vasodilation in response to acetylcholine was impaired in patients with AF and that this deficit was ameliorated after restoration of sinus rhythm via electrical cardioversion. Shin et al. [6] confirmed that AF patients have impaired brachial artery flow mediated dilatation (FMD), which can be reversed through induction and maintenance of sinus rhythm via catheter ablation. We did not explore whether antiarrhythmic drugs can restore endothelial function in our study as Dr. Guo and his colleagues stated in their letter [1]. However, endothelial function appears to improve after restoration of sinus rhythm irrespective of the strategy used to achieve conversion to sinus rhythm. Of note, previous studies examining the strategy of rhythm control versus rate control in the management of AF have not yet proven the benefit of a return to sinus rhythm [7]. Therefore, we agree with the suggestions by Guo and colleagues that our study would have benefited from inclusion of a rhythm control vs. rate control analysis to investigate whether antiarrhythmic drugs can restore endothelial function. We conclude that assessment of endothelial function may offer important information for AF patients who are scheduled to undergo conversion to sinus rhythm.