Prevalence of Physiological Electrocardiographic Findings in a Brazilian Cohort of Young Football Players: B-Pro Foot ECG Pilot Study

Type of funding sources: Foundation. Main funding source(s): Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Hospital de Clínicas de Porto Alegre Research and Event Incentive Fund (FIPE-HCPA)

The 12-lead electrocardiogram (ECG-12) is a useful tool in the assessment of athletes, and it may present findings compatible with physiological adaptations to regular exercise. ECG-12 findings in Brazilian soccer players are unknown.

To describe the prevalence of physiological ECG-12 findings in young Brazilian soccer players based on the "2017 International Criteria for Electrocardiographic Interpretation in Athletes".

Continuous variables were displayed as mean and standard deviation or median and interquartile range, while prevalence’s with 95% confidence intervals, and stratified by race. Intra-group differences were estimated by linear models or binomial and multinomial logistic regressions. Type I error was set to set a at 0.05. An additional margin of 0.025 was considered at the discretion of the statistician conditioned to the quality of the model. All analysis were running in Stata version 16.0.0.

2,581 athletes from 27 clubs (mainly first division), aged 15-35 years (median: 18 years) were evaluated. 1,268 (49.1%) were Caucasians, 796 (30.8%) Mixed-race (MR) and 517 (20.1%) Afro-Brazilians (AB). In this sample from across the country, we identified the following findings and its respective prevalence: sinus bradycardia (50%), ectopic atrial rhythm (1.4%), junctional rhythm (0.3%), incomplete right bundle branch block (23.7%), first-degree atrioventricular (AV) block (3.0%), Mobitz type I AV block (0.1%), and increase QRS voltage for left or right ventricular hypertrophy (35.2% and 17.3%, respectively). The mean PR interval was 153.9±28.7 ms, corrected QT interval 399.2±28.0 ms, and QRS duration 96.0±14.0 ms. ST elevation followed by T-wave inversion in leads V1–V4 was identified in 11/517 (2.1%) of AB athletes. Early repolarization was present in 828 athletes (32.1%), being more prevalent in AB when compared to MR and Caucasians (P = 0.003). Likewise, AB had a greater PR interval in comparison to MR and Caucasians (P <0.001 and P = 0.007, respectively). On the other hand, Caucasians had a significant longer QRS duration compared to AB. For all remaining variables there was no difference among races.

To the best of our knowledge, this is the first large study to describe the prevalence of physiological electrocardiographic finding in young Brazilian soccer players, according to "2017 International Criteria for Electrocardiographic Interpretation in Athletes". Future studies comparing the frequency of these findings with the prevalence observed in other cohorts are welcome.