Response to "Electrocardiographic sexual differences in patients with atrial fibrillation"

We appreciate the Letter to the Editor [ 1 ] related to the article [ 2 ] recently published in this Journal. We acknowledge the lack of a group without atrial fibrillation (AF); however, the study main objective was to compare sex-related differences in ECG of patients with different forms of AF. Therefore, we do not believe that a control group would have a major impact on the study conclusions or it is even feasible without avoiding major confounding factors. We are not sure to have adequately understood the point raised by the Authors' letter concerning the QTc interval. Indeed, they indicated that “females have significantly shorter QTc intervals than males in the general population”. However, the adduced references report longer QTc intervals in females than in males [ 3 , 4 ]. Consistent with these results, we found a longer QTc in females in both subgroups of paroxysmal and persistent AF. Finally, we agree that baseline characteristics of study population revealed significant differences in age, height, weight and body mass index (BMI) between males and females. In order to adjust results accordingly, a linear regression model was used instead of the propensity-score-matched analysis. This model should be preferred when the number of events is at least 8 times the number of confounders, as in our dataset [ 5 ]. BMI was not considered in the model because it is a combination of height and weight. We thank the Authors' letter for pointing out these important issues which we hope to have satisfactorily addressed.