Weather and Triggering Ventricular Arrhythmias in Patients with Implantable Cardioverter Defibrillators

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Background Several studies have examined the association between outdoor ambient weather and ventricular arrhythmia (VA) with mixed results. Because people spend most of their time indoors, we hypothesized that weather-related arrhythmia risk is linked to indoor temperature and water content, a property of outdoor air that is conserved indoors. Aims We examined the association between weather and VA using three weather measures – outdoor ambient temperature, estimated indoor temperature, and outdoor absolute humidity. Methods The clinical records of 203 patients implanted with a cardioverter defibrillator at Tufts Medical Center (Boston, Massachusetts, USA) between June 1, 1995 and December 31, 1999 were abstracted for VAs between 1995 and 2002. We used case-crossover methods to link National Weather Service measurements made at Boston Logan International Airport to the date and time of VAs (specifically ventricular tachycardia and ventricular fibrillation). Indoor temperature was estimated from the outdoor temperature using results from an indoor weather study that characterized the relationship between indoor and outdoor temperature in Boston. We matched on month, day of the week, and hour, and adjusted for barometric pressure, ozone, and particulate matter in conditional logistic regression models. Results Among 84 patients who experienced 787 VAs (mean follow-up = 3.5 years), lower estimated indoor temperature (odds ratio (OR) = 1.16, 95% confidence interval (CI): 1.06 - 1.27 for an interquartile range (IQR) (0.97°C) decrease in the 24-hour average) and lower absolute humidity (OR = 1.37, 95% CI: 1.21 - 1.56 for an IQR (2.7 g/m3) decrease in the 96-hour average) were associated with increased risk. Lower outdoor temperature increased risk only in warmer months, likely attributable to the poor correlation between outdoor and indoor temperature during cooler months. Conclusions We observed associations between lower indoor temperature and drier air with increased onset of VA among patients with implantable cardioverter defibrillators.