Heart Rate Monitor Instead of Ablation? Atrioventricular Nodal Re-Entrant Tachycardia in a Leisure-Time Triathlete: 6-Year Follow-Up.

This study describes a triathlete with effort-provoked atrioventricular nodal re-entrant tachycardia (AVNRT), diagnosed six years ago, who ineffectively controlled his training load via heart-rate monitors (HRM) to avoid tachyarrhythmia. Of the 1800 workouts recorded for 6 years on HRMs, we found 45 tachyarrhythmias, which forced the athlete to stop exercising. In three of them, AVNRT was simultaneously confirmed by a Holter electrocardiogram (ECG). Tachyarrhythmias occurred in different phases (after the 2nd-131st minutes, median: 29th minute) and frequencies (3-8, average: 6.5 times/year), characterized by different heart rates (HR) (150-227 beats per minute (bpm), median: 187 bpm) and duration (10-186, median: 40 s). Tachyarrhythmia appeared both unexpectedly in the initial stages of training as well as quite predictably during prolonged submaximal exercise-but without rigid rules. Tachyarrhythmias during cycling were more intensive (200 vs. 162 bpm, p = 0.0004) and occurred later (41 vs. 10 min, p = 0.0007) than those during running (only one noticed but not recorded during swimming). We noticed a tendency (p = 0.1748) towards the decreasing duration time of tachycardias (2014-2015: 60 s; 2016-2017: 50 s; 2018-later: 37 s). The amateur athlete tolerated the tachycardic episodes quite well and the ECG test and echocardiography were normal. In the studied case, the HRM was a useful diagnostic tool for detecting symptomatic arrhythmia; however, no change in the amount, phase of training, speed, or duration of exercise-stimulated tachyarrhythmia was observed.