Electrophysiological properties of the South Asian heart.

OBJECTIVE: The South Asian population has a lower burden of arrhythmia compared with Caucasians despite a higher prevalence of traditional cardiovascular risk factors. We aimed to determine whether this was due to differences in the electrophysiological properties of the South Asian heart. METHODS: We performed a retrospective cohort study of South Asian and Caucasian patients who underwent an electrophysiology study for supraventricular tachycardia between 2005 and 2017. Surface ECG, intracardiac ECG and intracardiac conduction intervals were measured and a comparison between the two ethnic cohorts was performed. RESULTS: A total of 5908 patients underwent an electrophysiology study at the Yorkshire Heart Centre, UK, during the study period. Of these 262 were South Asian and 113 met the eligibility criteria. South Asians had a significantly higher resting heart rate (p=0.024), shorter QRS duration (p=0.012) and a shorter atrioventricular (AV; p=0.001)) and ventriculoatrial (VA; p=0.013) effective refractory period (ERP). There was no difference in atrial or ventricular ERP. On linear regression analysis, South Asian ethnicity was independently predictive of a higher resting heart rate, narrower QRS and shorter AV-ERP and VA-ERP. CONCLUSIONS: South Asians have significant differences in their resting heart rate, QRS duration and AV nodal function compared with Caucasians. These differences may reflect variations in autonomic function and may also be influenced by genetic factors. Electrophysiological differences such as these may help to explain why South Asians have a lower burden of arrhythmia.