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<0.001). Nearly all HRmaxHRM spikes preceded Holter-documented arrhythmias. CONCLUSION: Many characteristics point to true arrhythmias as the cause of HRmaxHRM recordings with paroxysmal spike morphology: they are rare, do not occur randomly across athletes, and cosegregate with clinically documented arrhythmias. Whether they represent malignant arrhythmias or an extreme athletic cardiac phenotype remains to be determined and is relevant to the role of HRMs as surveillance tools. HRmaxHRM tracings with spike morphology should not be dismissed as artefact but require work-up to determine clinical relevance.