Got a Bad Heart – Beware of the Flu!

Researchers from the University of Texas in Houston say a bout of flu can increase your risk of dying from a heart attack by nearly a third. A large scale study by the researchers has come up with shocking results – flu epidemics also sharply raise the number of sudden coronary deaths.

Doctors have been urging people at risk from heart disease to get vaccinated against the flu each year. In the UK, the NHS covers all heart patients in its annual flu jabs campaign; however not all heart patients take advantage of this.

The new large scale study covering more than 35,000 people was conducted by Professor Mohammad Madjid and colleagues. The researchers investigated deaths during flu outbreaks in the Russian city of St. Petersburg between 1993 and 2000. They used autopsy reports instead of relying upon death certificates to get to the actual cause of death. This allowed them to find details about any symptoms of heart attacks in patients suffering from flu and pneumonia which otherwise would have been missed.

Considering the time period and the location covered under the study, very few people in the study population had received flu vaccine or cholesterol-lowering medications. This allowed the scientists to observe what happened naturally to all the subjects.

They found that a total of 11,892 patients died due to heart attacks, and 23,000 from chronic ischaemic heart disease (IHD). It was also observed that number of deaths in both conditions peaked in the period when flu and accompanying respiratory diseases were in epidemic proportions. The researchers did not find any difference between the death risk for men and women, either during the epidemic or the non-epidemic weeks.

Further analysis brought researchers to the conclusion that the risk of dying from a heart attack increased by a third during the weeks when flu was at its height; the risk for IHD patients increased by a tenth. The researchers believe this increase might be on account of inflammations caused by the flu that destabilise “silent” clots in the arteries.

A bout of flu can cause acute inflammation which in turn can destabilise atherosclerotic plaques in the arteries. These plaques are actually hardened deposits of cholesterol and fibrous tissue which collect on the blood vessel walls. When they rupture, they can cause release of blood clots that may block blood flow to the heart and lead to a heart attack.

Study leader Prof. Madjid said, “Our research has shown that influenza epidemics are associated with a rise in coronary deaths. This study shows that flu is an important trigger of heart attacks because flu is a severe infection, with high incidence rates and readily preventable.

“This calls for more intensive efforts to increase the vaccination rate in people at risk of coronary heart disease. This may be especially important in an influenza pandemic when we would expect to see high mortality amongst the elderly and those suffering from heart problems or who have multiple coronary risk factors” he added.

Prof. Madjid estimates that around two-thirds of American heart patients get vaccinated for the flu each year; if however all of them took a jab, it could save nearly 90,000 lives each year. He added, “My public health message is that flu is an important killer in cardiac patients. If people can recognise that the flu vaccine has specific cardioprotective effects, then high-risk people will be more likely to make sure that they receive the influenza vaccine every year.”

“We know from our other research that one in three people with heart disease do not consider themselves at high risk for heart-related complications from influenza and therefore do not receive the annual flu shots. Currently, people are not practising as we preach, and doctors need to work to change this.”

Cathy Ross, Heart Nurse at the British Heart Foundation (BHF) said, “This study adds to evidence from an important BHF-funded study at University College London – that flu can cause inflammation in our blood vessels and can go on to trigger a heart attack or stroke in people at increased risk.”

“People considered to be at increased risk are those who already have heart or circulatory disease. For this reason, heart patients in the UK are already offered flu jabs as a high priority. Making sure people at risk are given flu vaccinations, along with appropriate heart-protective medication such as statins, is vital to help to reduce the number of heart attack victims,” she added.

The study findings have been published in the European Heart Journal.

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