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Originally published by 2 Minute Medicine® (view original article). Reused on AccessMedicine with permission.

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1. In a self-controlled case series, patients were observed to have increased incidence of hospital admissions for acute myocardial infarction (MI) within seven-days of respiratory virus detection.

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2. Cases of MI hospitalization after respiratory virus detection trended towards higher rates in older adults and patients with a confirmed influenza B compared to influenza A infection.

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Evidence Rating Level: 4 (Below Average)

Study Rundown:

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While previous studies have demonstrated an association between respiratory illnesses and MI, many were subject to bias or did not have laboratory confirmation of the type of viral infection. This study used laboratory-confirmed indices to determine the presence of influenza-like respiratory illnesses. The primary outcome of the study was incidence of acute MI hospitalizations for patients that presented seven days after laboratory diagnosis of a viral respiratory infection compared to patients who were hospitalized at any other time within one year before or one year after their laboratory diagnosis. It was noted that the incidence of acute MI was significantly higher during the seven-day risk interval following viral infection detection compared to the control interval. Researchers concluded that this result supports the presence of an association between influenza-like illnesses and acute MI.

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Strengths of this study include use of a population with complete health history, including data on respiratory virus detection, while a significant limitation is lack of discernable onset of clinical respiratory infection in these patients. These results can provide clearer evidence of viral respiratory infection effects on cardiovascular health.

In-Depth [case series]:

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This self-controlled case series study evaluated an Ontario, Canada patient registry, with data assessed from 2008 and 2015, for all patients older than the age of 35 who had recorded history of undergoing testing for 1 or more respiratory viruses and a history of a hospitalization for acute myocardial infarction within 1 year of respiratory virus detection. Patients were assessed according to their date of respiratory infection detection, with hospitalization of MI within 7 days of virus detection occurring within a risk interval and hospitalizations occurring outside of this risk interval occurring within a control interval; the risk category was comprised of patients who were hospitalized for acute MI within 7 days of receiving laboratory confirmed testing for influenza A, influenza B, RSV, adenovirus, coronavirus, enterovirus, parainfluenza virus, or human metapneumovirus. The control category comprised patients who were hospitalized for acute MI within a year before or a year after their lab testing excluding the 7-day risk window. A total of 364 hospitalizations for acute myocardial infarction were included for analysis. MI’s occurred in the risk-interval at a significantly higher rate compared to during the control-interval (incidence ratio, 6.05; 95% confidence interval, 3.86 to 9.50). Higher incidence ratios were observed closer to the date of viral detection (days 1 to 3 and 4-7) than those outside the risk interval (days 8 to 14). Subgroup analyses trended towards increased incidence of acute MI hospitalization for adults 65 or older compared to adults aged 35-64, as well as increased hospitalization for patients presenting with influenza B compared to influenza A. Both interactions were non-significant (p = 0.14 and p = 0.19, respectively).

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