Introduction:
Atrial fibrillation (AF) is responsible for substantial morbidity and mortality, yet little is known about the environmental factors that may trigger AF episodes. Weather has been proposed as a potential precipitant of paroxysmal AF.
Hypothesis:
We assessed the hypothesis that changes in outdoor ambient temperature and outdoor absolute humidity may trigger paroxysmal AF in the following 24 hours.
Methods:
Patients with dual chamber implantable cardioverter defibrillators (ICDs) living in eastern Massachusetts were enrolled between September 2006 and March 2010 from the Tufts Medical Center Cardiac Arrhythmia Clinic (Boston, Massachusetts) and followed prospectively for episodes of paroxysmal AF lasting at least 30 seconds. Arrhythmias documented by the ICD were reviewed and interpreted by an electrophysiologist masked to exposure. The date and time of AF episodes were linked to hourly weather data measured at Boston Logan International Airport. We examined the hypothesis using a time-stratified case-crossover analysis matched on calendar month, day of week and time of day and adjusted for air pollution and barometric pressure. To reduce the possibility of over-representation of clustered events and to reflect the averaging time of the exposure, incident AF episodes were included in the analysis if at least 24 hours had passed since the previous AF episode.
Results:
Of 200 patients enrolled, 49 experienced at least one AF episode (n = 328 episodes). After excluding events with missing exposure or covariate information, analyses were confined to 230 AF episodes among 47 patients. The 47 patients with paroxysmal AF were followed for an average of 1.9 years, and 32 (68%) were male, 45 (96%) were Caucasian, the mean age was 67 years, 24 (51%) had a history of prior AF episodes, 27 (57%) had a pre-implantation ejection fraction < 35%, and 29 (62%) received the ICD for primary prophylaxis. Outdoor temperature in the previous 24 hours was not associated with AF (odds ratio (OR) = 1.13; 95% confidence interval (CI): 0.89, 1.43, p = 0.32, per interquartile range (IQR) decrease of 6.3°C). Lower absolute humidity in the previous 24 hours was associated with a higher risk of AF onset (OR = 1.33; 95% CI: 1.02, 1.74, p = 0.04, per IQR decrease of 3.5 g/m
3
); this risk increased slightly for the previous 3 hours (OR = 1.39; 95% CI: 1.06, 1.82, p = 0.02, per IQR decrease of 3.7 g/m
3
).
Conclusions:
In conclusion, drier air was associated with a transiently higher risk of paroxysmal AF in the following 24 hours among patients with dual chamber ICDs.
Contribution of morphology discrimination algorithm for improving rhythm discrimination in slow and fast ventricular tachycardia zones in dual-chamber implantable cardioverter-defibrillators