Abstract Background Determining the optimal HV interval cutoff for predicting the need for pacemaker (PM) implantation has been a recent focus of research. Current ESC guidelines recommend HV &amp;gt; 70 msec based on initial studies; however, new data suggest that a cutoff of &amp;gt;60 msec could appropriately identify patients at high risk for requiring PM implantation. While previous studies have indicated that women with bundle branch block (BBB) have a lower risk of AV block (AVB), gender differences in the optimal cutoff for considering a positive EPS have not been thoroughly investigated. Methods This cohort study included consecutive patients with unexplained syncope and BBB, enrolled from January 2010 to October 2021, with a median follow-up time of 3 years. Patients underwent a stepwise workup protocol involving an electrophysiological study (EPS) and long-term follow-up with an implantable cardiac monitor (ICM). Results Of the 503 patients in the study, 185 (38%) were women. The median age was 78 years (IQR 71-83), the median LVEF was 58% (IQR 50-62), and 110 (22%) had ischemic heart disease. The ECG showed LBBB in 194 (39%) patients and RBBB in 287 (57%). Among these, 177 (35%) also had left anterior hemiblock. The median HV interval was 60 msec (IQR 52-73), and EPS was diagnostic in 252 (50%) patients, with the majority (221, 44%) for AVB. In 91 patients with initially negative EPS, a diagnosis was made during follow-up with an ICM, and in 35, AVB was documented. In patients with negative EPS, an HV interval &amp;gt;60 msec was associated with an increased risk of AVB during follow-up (HR 2.5, 95% CI 1.6-4). However, significant gender differences were found. The risk of AVB was 2.5 times higher in men (95% CI 1-6) (Figure 1). Furthermore, sensitivity, specificity, PPV, and NPV for the cutoff of 60 msec were 47%/84%/51%/82% in men and 21%/78%/21%/78% in women. The AUC to predict AVB was 0.72 (95% CI 0.6-0.8) in men and 0.51 (95% CI 0.4-0.6) in women (Figure 2). Conclusions In patients with initially negative EPS, an HV interval &amp;gt;60 msec was associated with a higher risk of AVB during follow-up; however, significant gender differences were observed in diagnostic accuracy. In women, a cutoff of HV interval &amp;gt;60 msec presented poor diagnostic accuracy compared to men. Moreover, the HV interval did not adequately predict the development of AVB in women with a basal HV interval &amp;lt;70 msec, suggesting it may not be suitable for considering PM implantation in female patients.FIGURE 1FIGURE 2

HV interval cutoff should be different in women and men with syncope and bundle branch block