Potential impact of cold water immersion on arrhythmogenesis: a pilot exploratory study surrounding the Geneva christmas cup

Abstract Background Cold-water immersion (CWI) is gaining popularity and is regulated by sports federations with guidelines for various cold temperature ranges. Small studies suggest cardiovascular and stress reduction benefits from regular CWI, yet acute effects and cardiac risks remain underexplored. Purpose This study aimed to assess the impact of CWI on arrhythmogenesis among participants of the 2023 Geneva Christmas Cup, the world's largest cold-water swimming event. Methods Volunteers aged 45 and older were recruited through the organizing committee. Each underwent baseline cardiovascular risk assessment 10 days prior to the event, including medical interviews, physical exams, blood tests, and 12-lead ECGs. A waterproof ECG recorder (BodyGuardian Mini®) was attached to participants, monitoring them for 10 days up to the end of the race. An activity diary recorded training sessions, CWI exposure, and any symptoms. Data from BodyGuardian Mini® were analyzed for CWI-induced arrhythmias and conduction disturbances. The local ethics committee approved the study. Results Twenty volunteers (11 women, mean age 56 ± 6.4 years) participated. Their mean SCORE2/SCORE2-OP was 4 ± 1.8%, with 60% at low to moderate and 40% at high cardiovascular risk. Average weekly training was 5.5 ± 2.9 hours. Lake temperature was 7.0 degrees. One participant could not race but all completed CWI training and wore ECG recorders for an average of 226 ± 32 hours. Sixteen participants (80%) exhibited non-sustained atrial tachycardia (average 12.4 ± 8.8 events), and four (20%) had non-sustained ventricular tachycardia events (average 1.2 ± 0.5), with no significant pauses or >1st degree AV block observed. No arrhythmic events were directly linked to CWI. Conclusion This exploratory study of active, middle-aged participants with moderate cardiovascular risk found no association between CWI and arrhythmias. Further, larger-scale studies are necessary to conclusively determine CWI's safety.