Experts think the risk is greatest during the first week after detection of a laboratory-confirmed outbreak.
The findings have reinforced the need for those at high risk to be immunised.
Scientists discovered a “significant association” between acute respiratory infections, particularly influenza, and acute myocardial infarction, the medical name for a heart attack.
They also found an elevated risk – although not as high as for flu – for infection from other respiratory viruses.Study lead Dr Jeff Kwong, of the Institute for Clinical Evaluative Sciences and Public Health Ontario, Canada, said: “Our findings are important because an association between influenza and acute myocardial infarction reinforces the importance of vaccination.
“Our findings, combined with previous evidence that influenza vaccination reduces cardiovascular events and mortality, support international guidelines that advocate for influenza immunisation in those at high risk of a heart attack.”
Research published in the New England Journal of Medicine looked at nearly 20,000 adult cases of laboratory-confirmed influenza infection between 2009 to 2014 and identified 332 patients who were hospitalised for a heart attack within a year of a lab-confirmed flu diagnosis.
It suggests the risk may be higher for older adults, patients with influenza B infections, and patients experiencing their first heart attack.
The most virulent flu strain is influenza B which includes H3N2, or Aussie flu – thought to have killed Bethany Walker, 18, of Applecross in the Scottish Highlands, earlier this month.
This winter’s confirmed flu death toll stands at 120 with significantly more deaths among the over-65s than usual.
Experts said this year’s season was the worst since 2010-11, when swine flu became part of normal winter illness after the 2009 pandemic.
It comes as latest figures show a 150 per cent increase in patients turning up at their GP with “flu like symptoms” since the start of the year, according to analysis by the Royal College of GPs.An estimated 31,300 patients in England attended between January 8-14 – up more than 9,000 on the previous week.
Professor Helen Stokes-Lampard, Chair of the RCGP, said: “General practice continues to face huge winter pressures with a significant increase in patients presenting with influenza, and high numbers of patients continuing to present with other common winter illnesses.
“Wintertime always brings challenges for the health service and GP practices have prepared well in order to deliver the best possible care for patients.
“But patients can also help in keeping themselves safe and well during the cold weather.
“The best prevention for flu, other than observing good hygienic practices, such as regular hand washing, is for people, particularly those in at-risk groups, including patients with long-term conditions and pregnant women, to get their flu jab.
“It is not too late to receive some benefit from vaccination.
“If someone does have the flu, unfortunately there is no cure, but patients can assist their own recovery through taking plenty of rest and drinking lots of fluids as it is easy to become dehydrated.”
Dr Kwong added: “People at risk of heart disease should take precautions to prevent respiratory infections, and especially influenza, through measures including vaccinations and hand washing.”