That's especially true this flu season, because influenza B strains have been circulating widely.
The report confirmed the relationship between the flu and heart problems that medical specialists have been aware of for years.
Across the United States, flu-related hospitalizations are spiking, according to the U.S. Centers for Disease Control and Prevention.
The study "should not be interpreted as evidence of a lack of vaccine effectiveness, because this study was not created to evaluate the effectiveness of influenza vaccines", the researchers said.
The researchers behind the study say those who are already at risk of heart attack should protect themselves by getting the flu jab.
"Our findings are important because an association between influenza and acute myocardial infarction reinforces the importance of vaccination", lead author of the study Doctor Jeff Kwong told the Daily Mail.
"If you really don't want to have a heart attack this is one other thing you can do", says Kwong. "All of these can increase the chance of having a heart attack", Dr Kwong said.
Previous studies have looked for - and found - increased rates of heart attacks during influenza season.
Flu season in the Southern Tier: Seven things you need to know
Warning signs of the flu include: high fever, headache, joint or muscle pain, cough, chills, sore throat, congestion and fatigue. CDC Director Brenda Fitzgerald told the newspaper that the flu shot is still the best way to protect yourself from getting sick.
The disease can cause swelling or inflammation in the coronary arteries, which can release plaque and trigger blockages, cutting off blood flow. That imbalance between demand and supply can tip a patient over the edge into a heart attack, she said.
Here is what a new study has found.
In the new study, the researchers analyzed information from almost 20,000 adults in Ontario who were ages 35 and older and had a laboratory-confirmed flu diagnosis from 2009 to 2014. For 76%, it was their first heart attack, technically known as an acute myocardial infarction.
The news about the flu seems to keep getting worse: A new study suggests that the risk of heart attack dramatically increases for people who are suffering from influenza.
The patients also faced a higher risk shortly after coming down with other respiratory infections, the findings showed.
But 20 were clustered in the seven days after a flu diagnosis, suggesting that there is a link between having the flu and having a heart attack - at least among people aged 35 and older.
The research team added that patients should not delay medical evaluation for heart symptoms particularly within the first week of an acute respiratory infection. "Even if the flu shot isn't flawless, it may protect at least somewhat and the flu could be less severe, although this study didn't address that". But, Kwong pointed out, "even some protection is better than no protection". Vaccinations and washing your hands are some of the suggestions he made. And everyone can help out by staying home when they are sick and not exposing others to their infection, Kwong advised.
"Address all of the traditional risk factors you have - obesity, high blood pressure, high cholesterol", he said. It's safe, you take it just one time and it has minimal side-effects.
The findings were published January 25 in the New England Journal of Medicine.