Status of electrical instability of the myocardium in highly qualified athletes of acyclic sports

Objective. To study state dynamics of the cardiovascular system of athletes in acyclic sports against the background of submaximal physical activity to identify individuals at high risk of cardiovascular complications, including sudden cardiac death

Materials and methods. The survey was conducted among athletes of acyclic sports. Number of people examined: 50, average age 20.0±3.5 years old. Of these, 30 (60%) were men, average age 19.9±3.4 years old; women – 20 (40%), average age 21.0±3.8 years old. Qualification of athletes: CMS, MS, MSIC.

Results. At rest, instability of the depolarization phase is indicated by two ECG markers: a fragmented frQRS complex and a spatial QRS-T angle of more than 105º. Fragmented frQRS was detected in 73% of young males and 33% of young females. The average values of the QRS-T angle were within the physiological norm: 63±23º in young males and 40±14º in young females. Electrical ventricular systole, expressed by the Q-T interval, was 373±26 ms in young males and 385±35 ms in young females. The average value of the second indicator of repolarization instability Q-T interval dispersion was 50.7±12.8 ms in young males and 39.3±14.6 ms in young females. The average TWA amplitude in young males was 21.0 (18; 24) μV, and 20.5 (14; 25) μV in young females. Analysis of ECG markers of dysfunction of autonomic nervous regulation showed that the slowdown in heart rate DC was 19.0 (14.8; 31.5) ms in young males, 19.5 (11.8; 21.5) ms in young females. The acceleration of heart rate AC in young males was 19.8 (13.8; 26.0) ms, and 19.5 (11.5; 21.5) ms in young females.

After the load, no statistically significant changes in the frequency of detection of fragmented frQRS were observed in young males (p = 0.7472), while in young females a statistically significant increase in the frequency of detection of frQRS was detected (p = 0.0226). The average value of the QRS-T angle increased significantly – from 63±23º
to 85±25º in young males (p = 0.0117), while it did not change significantly in young females – from 40±24º to 55±26º  (p = 0.2606). Q-T dispersion in afterload compared to rest increased from 50.7±12.8 ms and reached 72.8±25.0 ms (p = 0.000) in young males and from 39.3±14.6 ms to 68.2 ±10.7 ms in young females (p = 0.0029). Deceleration (DC) and acceleration (AC) of heart rate decreased significantly in young males. For young males – by 77.7 and 82.3%, respectively (p < 0.0001), and for young females – by 84.9 and 80.0%, respectively (p < 0.0001).

Conclusion. At rest, we identified only 10 markers of electrical instability of the myocardium, and 38 markers after exercise, that is, almost 4 times more. This suggests that even in highly qualified athletes, load causes a trend towards electrical instability of the myocardium, mainly in the repolarization phase and in relation to autonomic nervous regulation.

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