Winter cold harder on people with implantable heart defibrillators, research suggests

Cold weather could come with a set of risks for some people with existing heart conditions, new research suggests.

People with implantable cardioverter defibrillator 'shocked' more often during frigid temperatures

Patients with implantable cardioverter-defibrillators may be more at risk of getting shocks during the coldest parts of the year, new researcher suggests.

Cold weather could come with a set of risks for some people with existing heart conditions, new research suggests.

Winnipeg cardiology resident Dr. Justin Cloutier and a team of researchers recently presented their findings at the Canadian Cardiovascular Congress in Montreal.

Their results seem to indicate that as the temperatures plummet during the coldest winter months, those with implantable cardioverter defibrillators (ICDs) are more likely to receive uncomfortable shocks to the chest.

ICDs are similar to pacemakers, but instead of controlling the pace of the heart, they deliver shocks when rhythms deviate from the typical "lub-dub" beat and get into more dangerous or erratic patterns, Cloutier said.

While they do save lives, defibrillator shocks can pack a painful wallop, too.

"They cause a lot of trouble for patients," he said. "Some people have described it as like getting kicked in the chest by a horse."

In a previous study, Cloutier and others found there was a relationship between heart attacks and cold weather, which influenced their decision to look at whether the risks of ICD jolts and the cold were related.

"No one has ever really described the association between shocks from defibrillators and cold weather" he told CBC News. "We're sort of well-situated to look at this in Winnipeg, given our climate"

The team compared weather data over a six-year period from Environment Canada against clinical data from people with ICDs who reported being shocked between January 2010 and December 2015.

Over that time period, 360 ICD patients experienced 756 "unique" shocks.

Researchers found that patients were 26 per cent were more likely to get zapped during the most extreme cold days of the year (–10 C or colder), and about nine per cent more likely on days when temperatures were between –10 C and 10 C.

The preliminary results from the study are important, Cloutier said, because they could push researchers and medical health professionals to better understand why people have heart rhythm problems and risks for shock therapies.

As for what people with ICDs should take away from the study, Cloutier says going into hibernation and avoiding the cold at all costs isn't the answer.

"I by no means would tell people to stay inside during cold winter months, because we know that being outside, being physically active is important for your heart health. I think you have to exercise common sense, and when it's really cold outside make sure you're bundled up appropriately."

About the Author

Bryce Hoye


Bryce Hoye is an award-winning journalist and science writer with a background in wildlife biology. Before joining CBC Manitoba, he worked for the Canadian Wildlife Service monitoring birds in Manitoba, the Northwest Territories, Nova Scotia and Alberta. Story idea? Email

With files from Ismaila Alfa and Nadia Kidwai