High heart rate peaks from chest-strap recordings in athletes: prevalence, characteristics, and clinical relevance

AIMS: Evaluate the prevalence, morphology, and clinical relevance of transient, extreme heart rate (HR) spikes on heart rate monitors (HRMs) in endurance athletes. METHODS: HRM training sessions (n=57,282) from 251 endurance athletes (167 Pro@Heart; 84 Master@Heart), were analysed. Individual physiological maximal HR (HRmaxTan) was determined using the kernel density of peak HR values. Extreme HR events were defined as sessions exceeding this limit (HRmaxHRM). Tracings were visually classified; paroxysmal spikes were considered to be potential tachyarrhythmia. Incidence was estimated with Kaplan-Meier analysis. Demographic, training, and device predictors were tested with a generalised linear mixed model (GLMM). Clinical and Holter data were reviewed for arrhythmia documentation. RESULTS: Extreme HR values occurred in 1.0% of sessions across 133 athletes (53.0%). Paroxysmal spikes represented 28.1% of cases, occurred in 0.27% of sessions and 23.9% of athletes, cumulative incidence was 33.8% (95% CI 26.1-41.4%) after 291 sessions. The GLMM identified no significant predictors. Paroxysmal spikes were observed in 71.4% of athletes (10/14) with arrhythmia versus 21.1% without (50/237) (p