Differences in sino-atrial and atrio-ventricular function with age and sex attributable to the Scn5a<sup>+/-</sup> mutation in a murine cardiac model
Jeevaratnam K., Zhang Y., Guzadhur L., Duehmke RM., Lei M., Grace AA., Huang CLH.
Aim: To investigate the interacting effects of age and sex on electrocardiographic (ECG) features of Scn5a+/- mice modelling Brugada syndrome. Methods: Recordings were performed on anaesthetized wild-type (WT) and Scn5a+/- mice and differences attributable to these risk factors statistically stratified. Results: Scn5a+/- exerted sex-dependent effects upon sino-atrial function that only became apparent with age. RR intervals were greater in old male than in old female Scn5a +/-. Atrio-ventricular (AV) conduction was slower in young female mice, whether WT and Scn5a+/-, than the corresponding young male WT and Scn5a+/-. However, PR intervals lengthened with age in male but not in female Scn5a+/- giving the greatest PR intervals in old male Scn5a+/- compared with either old male WT or young male Scn5a +/- mice. In contrast, PR intervals were similar in old female Scn5a+/- and in old female WT. QTc was prolonged in Scn5a +/- compared with WT, and female Scn5a+/- compared with female WT. Age-dependent alterations in durations of ventricular repolarization relative to WT affected male but not female Scn5a+/-. Thus, T-wave durations were greater in old male Scn5a+/- compared with old male WT, but indistinguishable between old female Scn5a+/- and old female WT. Finally, analysis for combined interactions of genotype, age and sex demonstrated no effects on P wave and QRS durations and QTc intervals. Conclusion: We demonstrate for the first time that age, sex and genotype exert both independent and interacting ECG effects. The latter suggest alterations in cardiac pacemaker function, atrio-ventricular conduction and ventricular repolarization greatest in ageing male Scn5a+/-. © 2010 Scandinavian Physiological Society.