Assessment of the heart rate variability and cardiac biomarkers in young athletes: a cross-sectional study

Background: Active athletic activity can occasionally trigger the development of cardiovascular diseases, especially in highly dynamic sports. Athletes who perform their training in cold climatic conditions are at risk of exhaustion of the functional reserve of the body and the sports-associated overstrain. Aim: To determine the characteristics of heart rate variability (HRV) and cardiac biomarkers in young hockey and football players in the Far North, to search for predictors of pathological myocardial remodeling. Methods: This was an observational cross-sectional study in 160 boys aged 12 to 17 with health groups II to III performed in the Children's Health Center of the Novourengoy Central Regional Hospital in Spring 2022. We performed a standard electrocardiography (ECG) and 24-hour ECG monitoring, echocardiography (EchoCG), and blood sampling for markers of myocardial damage, endothelial dysfunction, and proteolysis. The study group consisted of 86 children involved in hockey and football, and the control group consisted of 74 teenagers not going in for active sports. Results: The median values of the primary waves and intervals on the standard ECG were within the normal range in both groups. The 24-hour ECG monitoring showed significant differences between the study groups for average heart rate (84 [78; 91] vs. 93 [83; 100], p 0.001) and maximal heart rate (150 [128; 159] vs. 159 [147; 184], p = 0.001). The proportion of children with reduced HRV in the control group was significantly higher than in the athlete group (64.2% vs. 36.4%). Median levels of the myocardial damage markers were within the reference ranges in all study children, with lactate dehydrogenase (p = 0.034), aspartate aminotransferase (p = 0.001), and troponin I (p = 0.011) levels being significantly lower in the athlete group. As for the EchoCG parameters, there was a 1.2-fold increase in the left ventricular mass index and the right ventricular systolic area in the athletes compared to the control group (p 0.001). According to the ROC analysis, the cut-off value of matrix metalloproteinase 2 predictive for the high risk of myocardial remodeling in the athletes was 337.49 ng/mL, with sensitivity of 75% and specificity of 87.2%. Conclusion: The matrix metalloproteinase 2 levels above 337.49 ng/mL and low HRV may be considered as risk factors for myocardial remodeling in athletes with borderline electrocardiographic and echocardiographic parameters.