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What Every Coronary Patient Needs to Know About Flu Season

What Every Coronary Patient Needs to Know About Flu Season

United States: Acute Myocardial Infarction (MI) has been associated with Influenza infection, especially among individuals who have sought treatment in a hospital for coronary artery disease (CAD). The research was done using a Dutch observational case series study.

The modified comparative occurrence of acute myocardial infarction within the span of 1 to 7 days subsequent to laboratory-confirmed influenza infection (termed the risk period) versus the control period of 1 year prior and 51 weeks succeeding the risk interval was found to be 6.16 (95% CI 4.11-9.24), as explained by Patricia Bruijning-Verhagen, MD, PhD, of Utrecht University in the Netherlands, and her associates in NEJM Evidence.

The relative incidence of acute MI for individuals who has not been hospitalised for CAD was around 16.60 (95% Cl 10.45-26.37). The stats were compared to those who were hospitalised for CAD, the stats were at 1.43 (95% Cl 0.53-3.84).

Bruijning-Verhagen stated, “I was not surprised to find that influenza infection increases the short-term risk of acute myocardial infarction. What did surprise me was the finding that the risk was most elevated for persons without a history of hospitalization for cardiovascular disease,” as highlighted by MedPage Today.

She highlighted that the study was conducted on cases that were severe enough to require medical attention and urgent testing. She was quoted saying, “We do not know whether the findings also apply to milder influenza infections.”

The situation was also addressed by MBBS, PhD, of the University of New South Wales Sydney – C. Raina MacIntyre who mentioned that the major risk have been noticed among the people who are have been suffering with undiagnosed and underlying CAD.

The experts were quoted saying, “[Influenza] vaccination is low-hanging fruit for people at risk of acute myocardial infarction who have not yet had a first event. It is time that we viewed influenza vaccine as a routine preventive measure for ACS [acute coronary syndrome] and for people with CAD risk factors, along with statins, blood pressure control, and smoking cessation,” according to reports by MedPage Today.

MacIntyre and colleagues discussed a recent study that found getting a flu shot shortly after a heart attack or for people with high-risk heart conditions lowers the chances of death, heart attacks, or clotting in stents. They also mentioned other studies showing flu shots can reduce heart attacks by 29%. However, their study couldn’t use national data to directly compare heart attack rates in vaccinated and unvaccinated people.

Infections induced by respiratory pathogens other than influenza were likewise linked with an escalated relative occurrence of acute myocardial infarction (MI) and “might extend to all acute respiratory infections severe enough to necessitate microbiologic examination,” Bruijning-Verhagen and collaborators elucidated, according to the reports by MedPage Today.

Regarding Respiratory Syncytial Virus (RSV), the relative incidence of acute MI stood at 3.38 (95% CI 1.07-10.71), while it was 4.06 (95% CI 2.27-7.25) for other respiratory viruses. Among those presenting upper respiratory symptoms aligned with a viral infection but exhibiting negative virus test outcomes, the relative incidence reached 4.56 (95% CI 2.99-6.94).

This investigation solely incorporated pre-COVID-19 pandemic data, yet evidence intimates that infection with SARS-CoV-2 is likely correlated with adverse cardiovascular repercussions.

Bruijning-Verhagen and peers postulated that the amplified risk of acute MI subsequent to acute influenza and other respiratory infections is attributable to heightened metabolic demand and effects on inflammatory and coagulation pathways, culminating in atherosclerotic plaque destabilization and subsequent blockage.

The authors further conjectured that prophylactic treatment with antihypertensive and antithrombotic medications might abate the risk of acute MI post-influenza infection, remarking that a posthoc analysis suggested an elevated risk of acute MI in individuals with influenza not on preventive medications compared to those who were, as per reports by MedPage Today.

Nonetheless, in a separate editorial, Lori Dodd, PhD, of the National Institute of Allergy and Infectious Diseases, questioned whether the correlations between flu and acute MI in the study signify a genuine causal link “or point to another (unadjusted) factor connecting the two.”

“One plausible elucidation is the impact of workup bias, a propensity to test and identify preexisting conditions … among patients with an acute infection who have preexisting risk factors,” Dodd articulated, noting that the study also found a significant association between influenza and hospitalization for diabetes, without a clear rationale. “The heightened surveillance for other diagnoses would result in estimations of increased risk post-influenza,” she proposed.

This observational, registry-based study employed a self-controlled case series design and included adults aged 35 and older who were tested for respiratory viruses from January 2008 through December 2019. The researchers identified 158,777 PCR tests for influenza from 16 laboratories across the Netherlands and linked the data to national medication, hospitalization, mortality, and administrative databases. Of the PCR tests, 23,405 were positive for influenza, representing unique illness episodes.

A total of 401 episodes were identified with acute MI occurring one year before and one year after confirmed influenza infection and were included in the analysis; 25 cases occurred 1 to 7 days post-influenza infection, and the remaining cases transpired during the control period. Over 60% of influenza infections were attributed to influenza type A.

The median age of the study cohort was 74 years; 64% were male, and 64% had a history of hospitalization with coronary artery disease. Within a year post-influenza infection, 35% had succumbed (all causes).

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