The prevalence of short PR interval in adolescent athletes and non-athletes

Abstract

Abstract Funding Acknowledgements Type of funding sources: Private grant(s) and/or Sponsorship. Main funding source(s): Malta Heart Foundation and Beating Hearts Background Little is known about the prevalence and clinical relevance of an isolated short PR interval in young individuals. Objectives To explore the PR interval in adolescent athletes and non-athletes and determine possible association with sex, age, ethnicity, athletic ability and sporting discipline. Methods Between 2017-2018, school children aged 14-17 years were invited to participate in a National cardiac screening programme comprised of a health questionnaire and a resting 12-lead ECG. An athlete was defined as an individual participating in >4 hours/week of organised sports. Sport disciplines were categorised as skill, power, mixed and endurance. A short PR interval was defined as <120ms. Results A total of 1619 (61.0%) non-athletes and 1036 (39.0%) athletes (median age 15 years, 50.5% females, 93.0% Caucasian) participated in the screening program. Most athletes participated in mixed sports (62.2%). The mean PR interval was shorter in non-athletes compared to athletes (136.65 ± 19.00ms vs 139.93 ± 19.86ms p < 0.001) and in females compared to males (135.98 ± 18.39ms vs 139.93 ± 20.20ms, p < 0.001). An isolated short PR interval was present in 405 (15.3%) individuals. Associated pre-excitation was present in an additional 5 cases (0.2%). A short PR interval was commoner in females (18.7% vs 11.7%, p < 0.001) and in non-athletes (16.6% vs 13.2%, p = 0.020). Age (p = 0.657) and ethnicity (p = 0.115) did not influence the presence of a short PR interval. The presence of a short PR interval in adolescent athletes was independent of the sporting discipline category (p = 0.071), in both males (p = 0.400) and females (p = 0.233). The absolute PR interval did not differ significantly between sporting categories (p = 0.065), in both genders (males, p = 0.202, females, p = 0.279). Symptoms that were suggestive of arrhythmias were present in similar proportions of individuals with short and normal PR intervals (18.8% vs 17.1%, p = 0.393). Conclusion An isolated short PR interval was a frequent finding in this cohort, with a predilection for females and non-athletes. The high frequency of short PR in young individuals suggests that in the absence of pre-excitation or symptoms, further evaluation is not warranted. Long-term follow-up studies may further elucidate the clinical relevance of this phenomenon.