Be­gin­ning of a flu in­fec­tion can in­crease the risk of heart at­tack

A flu vac­cine may be the best form of heart at­tack in­surance ac­cord­ing to the New Eng­land Jour­nal of Medicine.

The Standard Journal - - LOCAL - By Karen Ka­plan

Not into the flu shot? Think of it as a heart at­tack vac­cine in­stead.

That’s be­cause the first week or so of a flu in­fec­tion ap­pears to make you much more sus­cep­ti­ble to a heart at­tack, ac­cord­ing to a new study in the New Eng­land Jour­nal of Medicine.

The find­ings are based on 148,307 cases of pa­tients who were tested for in­fluenza. Among all of those tests, 19,729 turned up pos­i­tive for the flu. And among those cases, there were 332 pa­tients who had at least one heart at­tack in the year be­fore or after their flu spec­i­men was tested. (The study au­thors tal­lied 364 hos­pi­tal­iza­tions for acute my­ocar­dial in­farc­tion over­all, mean­ing that some un­lucky folks had two or more heart at­tacks dur­ing the two-year ob­ser­va­tion pe­riod.)

Twenty of those heart at­tacks oc­curred within one week of a pos­i­tive flu test. That, of course, was a rate of 20 heart at­tacks per week.

The other 344 heart at­tacks hap­pened some other time in the twoyear ob­ser­va­tion pe­riod. That worked out to 3.3 heart at­tacks per week.

That means the risk of a heart at­tack was six times greater in the first week after flu test­ing than at other times when the flu was much less likely to be a fac­tor.

The re­searchers re­did their anal­y­sis by split­ting up that dan­ger week into two parts. They found that heart at­tack risk was 6.3 times greater dur­ing the first three days after a flu test and 5.8 times greater in days four through seven.

About one- quar­ter of the pa­tients in the study were 65 years old, and the rest were older. When the re­searchers ex­am­ined those two groups sep­a­rately, the link be­tween flu in­fec­tion and heart at­tack risk held up only for the older group.

There was no sign of an in­creased heart at­tack risk in the rest of the first month after get­ting a flu test.

The re­searchers, led by Dr. Jef­frey C. Kwong of the Univer­sity of Toronto, ac­knowl­edged that they couldn’t do their anal­y­sis based on the date when pa­tients were ac­tu­ally in­fected with the in­fluenza virus, or when they first be­gan hav­ing symp­toms, be­cause that in­for­ma­tion was not avail­able. How­ever, in cases where pa­tients get a flu test, they have typ­i­cally been sick for only one or two days first.

Also, not all flu cases are se­vere enough to prompt pa­tients to go and get test- ed. That means the re­sults of this study may not ap­ply to peo­ple with milder ill­nesses, they added.

The re­searchers did no­tice that when flu test re­sults came back pos­i­tive for cer­tain other kinds of res­pi­ra­tory in­fec­tions in­stead of for in­fluenza, there was still an in­creased (though smaller) short-term risk for heart at­tacks. That sug­gests that it’s not the flu it­self that’s the prob­lem — it’s the bi­o­log­i­cal im­pact of a res­pi­ra­tory in­fec­tion.

For in­stance, an in­fec­tion can cre­ate con­di­tions that make blood clots more likely to form and cause blood ves­sels to con­strict. In­fec­tions also cause in­flam­ma­tion and can re­duce blood pres­sure. All of these are risk fac­tors for a heart at­tack, Kwong and his col­leagues wrote.

The study re­sults sug­gest that peo­ple who want to avoid a heart at­tack should be sure to get a flu shot — and that doc­tors and pub­lic health of­fi­cials should en­cour­age them to do so.

“Car­dio­vas­cu­lar events trig­gered by in­fluenza are po­ten­tially pre­ventable by vac­ci­na­tion,” the re­searchers wrote.

Vac­cines for other kinds of res­pi­ra­tory in­fec­tions should be em­braced as well, they added. Even sim­ple ac­tions like wash­ing your hands, block­ing your cough and keep­ing germy sur­faces clean may re­duce your risk of a heart at­tack.

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