With most of Canada expected to experience more snow than usual this winter, a Toronto cardiologist is warning of the dangers of shovelling after a storm.
Mali Worme, an attending cardiologist at University Health Network’s Peter Munk Cardiac Centre, told TorontoToday there is a significant increase in heart attack events after a major snowfall.
In winter, colder temperatures have an effect on the cardiovascular system that can lead to increased heart rates and higher blood pressure. Mix in the need to shovel driveways and it creates a perfect storm, Worme said, especially for those with pre-existing coronary disease.
Worme said exposure to the cold can constrict or narrow the coronary arteries around the heart, leading to a rise in blood pressure. A major concern with constrictions is that they result in less blood flow to the heart.
“Now you're in a situation where the cold means your heart needs more oxygen delivery, because your heart rate and your blood pressure are higher, but the cold also means you're getting less oxygen delivered to your heart,” Worme said. “In a way, it’s a perfect milieu for a coronary event.”
Attempting to shovel snow in these conditions is especially dangerous because most people often go from being totally at rest to engaging in significant physical exertion, Worme said.
The cardiologist said a study showed the strain created by shovelling snow is more than what occurs in a treadmill exercise test at the doctor, in which patients run until their heart rates are above 85 per cent of their maximum predicted heart rate — “a simple equation based on your age,” she said.
To put that in perspective, heart rates can approach 100 per cent of a person’s maximum predicted heart rate while shovelling snow, according to Worme.
Who is most at risk?
The Public Health Agency of Canada says that one in 12 Canadian adults aged 20 and over live with diagnosed heart disease, which is the second leading cause of death across the country.
The biggest risk population is men who either have a personal history of coronary heart disease — such as a prior bypass surgery or heart attack — or anyone with a significant family history of disease at a young age, Worme said.
According to the American Heart Association, children and older adults are also at increased risk because they may have impaired mobility or limited ability to communicate.
Older adults may also have lower subcutaneous fat and thus be unable to sense temperature, leading to hypothermia without realizing.
Preventative measures
The City of Toronto says safe snow shovelling requires preparation, proper tools and good technique.
People who have had a heart attack or other forms of heart disease, have high blood pressure or cholesterol levels, or who smoke or live a sedentary lifestyle should “think twice” before going outside to clear the driveway, according to the city’s website.
Worme said one method to reduce risk is to use mechanical snow removal methods, though she said evidence has been found that using a snow blower can still be dangerous due to the pushing and pulling motions.
Another method to prepare for shovelling is to go for a walk or warm up inside beforehand, she said. Going from the couch to immediately shovelling snow should be avoided.
The city said marching in place for several minutes beforehand is a good warm up.
Once outside shovelling, frequent breaks should be taken to allow for blood pressure and heart rates to come down, Worme said. The city recommends shovelling for five to seven minutes, then resting for two to three.
Snow should also be pushed — not lifted — and the shovel should be held close to the body, according to the city. In deep snow, small amounts of one to two inches should be removed at a time.
When it comes to warning signs and symptoms, Worme said the common ones to look out for are chest pain, pressure, tightness and squeezing.
The cardiologist said that in the emergency room, patients with heart attacks will often describe a heaviness or a tightness, and that “the classic description is an elephant is sitting on my chest.”
She said it's important to educate people that “just because it doesn't feel like a pain, doesn't mean that it's not your heart.”
Other warning signs include lightheadedness, as well as the heart continuing to beat rapidly and shortness of breath after stopping the exercise.
The city said 911 should be called immediately if these symptoms are experienced. The city’s website can be visited for more tips about shovelling snow.