Evidence for reduced susceptibility to cardiac bradycardias in South Asians compared with Caucasians.

OBJECTIVES: To investigate ethnic differences in susceptibility to bradycardias in South Asian and white European patients in the UK by determining rates of permanent pacemaker (PPM) implantation for sinus node dysfunction (SND) and atrioventricular block (AVB) in each ethnic group. METHODS: We carried out a retrospective cohort study into new PPM implantation during the period from 1 May 2006 to 31 March 2014, in patients of South Asian and Caucasian ethnicity resident in Leicestershire, UK. Numbers of individuals at risk in each ethnic group were derived from UK National Census data of 2011. Crude, and age-standardised incidence rates and risk ratios per 1000 population of PPM implantation were calculated for Caucasians and South Asians. RESULTS: During the study period, 4883 individuals from the Leicestershire population of 980 328 underwent PPM implantation, a cumulative implantation rate of 4.98/1000 population. The population cumulative PPM implantation rate for SND was 1.74/1000, AVB 2.83/1000 and other indications 0.38/1000 population. The crude incidence in Caucasians (6.15/1000 population) was higher than in South Asians (1.07/1000 population) and remained higher after age standardisation (5.60/1000 vs 2.03/1000, P<0.001). The age-standardised cumulative PPM implantation rates were lower in South Asians for both SND (0.53/1000 in South Asians; 1.97/1000 in Caucasians, P<0.001) and AVB (1.30/1000 in South Asians; 3.17/1000 in Caucasians, P<0.001). Standardised risk ratios (95% CI) for PPM implantation in South Asians compared with Caucasians for all pacing indications, SND and AVB were 0.36 (95% CI 0.36 to 0.37), 0.27 (95% CI 0.27 to 0.28) and 0.41 (95% CI 0.41 to 0.42), respectively. CONCLUSIONS: Rates of PPM implantation are lower in South Asians residing in the UK, compared with Caucasians. This observation raises the possibility of lower inherent susceptibility to bradycardias in South Asians compared with Caucasians. Studies aimed at identifying underlying mechanisms, including possible genetic differences, are warranted.