Relationship of Extreme Cold Weather and Implantable Cardioverter Defibrillator Shocks.

Cold weather to 0°C has been implicated as a risk factor for ventricular arrhythmias and implantable cardioverter defibrillator (ICD) shocks. The effect of more extreme cold weather on the risk of ventricular arrhythmias and ICD shocks is unknown. We sought to describe the relationship between extreme cold weather and the risk of ICD shocks. We retrospectively identified patients seen at the Pacemaker and Defibrillator Clinic at St. Boniface Hospital in Winnipeg, Manitoba, Canada between 2010 and 2015 with an ICD shock. We excluded multiple shocks occurring on the same day in a single patient. We collected weather data, and evaluated the relationship between ICD shocks and weather on the same day as the shock using Negative Binomial regression. Three hundred and sixty patients experienced a total of 1,355 shocks. When excluding multiple shocks occurring in a single patient on the same day, there were 756 unique shocks. The daily high (DH) was the strongest predictor of receiving an ICD shock. Compared with the warmest days (DH above 10°C), shocks were 25% more common on the coldest days (DH below -10°C), and 8% more common on cold days (DH between -10°C and 10°C). This linear trend was statistically significant, with a p-value of 0.04. In conclusion, we found an association between extreme cold weather and ICD shocks.