Abstract
BACKGROUND: Arrhythmia, particularly atrial fibrillation, is on the rise globally. While increased surveillance, aging populations, and other risk factors partially explain this rise, emerging risks such as extreme heat from climate change are underexplored. METHODS: We used Product Surveillance Registry by Medtronic (2016-2023) in the United States to examine patients with implantable cardioverter-defibrillator or cardiac resynchronization therapy defibrillator devices. We identified first arrhythmic episodes (atrial tachycardia/fibrillation [AT/AF] or ventricular tachycardia/fibrillation) recorded by devices. Events were matched to ambient temperatures from local weather stations. We used a case-crossover design where each arrhythmia event hour was matched with multiple control hours from the same patient, within the same day of week, month, and year. Conditional logistic models were then pooled across all climate zones in the United States to obtain nonlinear dose-response between temperature and arrhythmia. RESULTS: Our analysis included 3079 individuals across 103 cities. Fewer AT/AF and ventricular tachycardia/fibrillation events occurred during early morning hours (1 am-8 am) compared with daytime hours (9 am-4 pm) (P <0.001). AT/AF episodes were also fewer on weekends compared with weekdays (P <0.001). We found a significant dose-response relationship between high outdoor temperatures and AT/AF events. Relative to an optimal temperature (19 °C), odds ratios for AT/AF events increased substantially at temperatures of 39 °C (odds ratio, 2.41 [95% CI, 1.37-4.25]), 40 °C (odds ratio, 2.60 [95% CI, 1.38-4.89]), and 41 °C (odds ratio, 2.81 [95% CI, 1.40-5.63]). No significant association between temperature and ventricular tachycardia/ ventricular fibrillation was observed. Lagged temperature exposures did not change the results. CONCLUSIONS: Extreme hot outdoor temperatures were significantly associated with higher odds of AF episodes.