How sex affects the sinus rhythm heartbeat.

Background: There is increasing awareness of sex-specific differences in epidemiology and pathophysiology of atrial fibrillation (AF). It is, however, unknown whether males and females differ in atrial electrophysiological properties during sinus rhythm (SR). The aim of this study was therefore to investigate sex-based (regional) differences in electrophysiological properties during SR of the right (RA) and left (LA) atrium including Bachmanns Bundle (BB) and pulmonary vein region (PVA). Methods: Intra-operative, high resolution mapping during SR was performed in 53 matched females with males (without a history of AF), to measure lines of conduction block (CB), continuous conduction delay and block (cCDCB), conduction velocities (CV), total atrial activation times (TAT), unipolar potential voltages and percentage of low voltage areas (LVA). Results: Compared to males, females have significantly 1) lower unipolar potential voltages and slower CV at both RA and BB, 2) more LVAs, CB and cCDCB lines and longer CB and cCDCB lines at the RA only (all P < 0.05). Conclusions: Electrophysiological properties of the atria during SR differ between males and females. These sex-based differences are particularly present at the RA and to a lesser degree at BB. In females, both the RA and BB contained more areas of conduction disorders and low voltage potentials. Future studies are required to investigate whether these areas play a role in sex-based differences in vulnerability to arrhythmias such as atrial fibrillation.