Link between flu and heart complications grow stronger — large, 8-year study

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The link between influenza and serious heart conditions just grew stronger. A study looking at more than 80,000 adult patients hospitalised with flu over eight seasons found that sudden, serious heart complications were common, occurring in 12% of patients, or 1 in 8. “Previous to our study, there had been suggestions between the link, but our study shows just how common it is,” said lead author Eric Chow, an infectious diseases fellow at University of Washington School of Medicine. The study underscores the importance of getting a flu shot early.

“There are few respiratory viruses we have a vaccine for,” he said. “Our team motto is ‘Get a flu shot.'” Chow previously worked as an epidemic intelligence service officer, or “disease detective,” for influenza at the US Centres for Disease Control and Prevention.
The study found that 5% of patients hospitalised with the flu had a cardiac complication despite having no documented underlying conditions.

In the last month, there have been cases of otherwise healthy athletes showing signs of heart complications after recovering from COVID-19. For example, 27-year-old Florida State basketball player Michael Ojo, who recovered from COVID-19, died of an apparent heart attack at a practice.

Chow said he is not surprised this is happening to healthy people who have been infected with SARS-CoV-2, the virus that causes COVID-19. The virus can cause damage to the lungs and other organs, including the heart. Inflammation makes hearts vulnerable to potentially fatal arrhythmias during vigorous exercise.

In this study of adults hospitalized with flu, 12% had acute heart complications. Of these, 30% were admitted to the ICU and 7% died while in the hospital.

The CDC recommends that everyone 6 months and older get a flu vaccine every flu season. According to the CDC, flu vaccination is always considered important for people at high risk of developing serious flu complications, including people with heart disease. Flu shots are approved for people with heart disease, but people with heart disease should not receive the live attenuated influenza vaccine (LAIV, also known as the nasal spray flu vaccine).

However, any intramuscular flu shot, such as any inactivated or recombinant influenza vaccine, would be appropriate.

Background: Influenza may contribute to the burden of acute cardiovascular events during annual influenza epidemics.
Objective: To examine acute cardiovascular events and determine risk factors for acute heart failure (aHF) and acute ischemic heart disease (aIHD) in adults with a hospitalization associated with laboratory-confirmed influenza.
Design: Cross-sectional study.
US Influenza Hospitalisation Surveillance Network during the 2010-to-2011 through 2017-to-2018 influenza seasons.
Participants: Adults hospitalized with laboratory-confirmed influenza and identified through influenza testing ordered by a practitioner.
Measurements: Acute cardiovascular events were ascertained using discharge codes from the International Classification of Diseases (ICD), Ninth Revision, Clinical Modification, and ICD, 10th Revision. Age, sex, race/ethnicity, tobacco use, chronic conditions, influenza vaccination, influenza antiviral medication, and influenza type or subtype were included as exposures in logistic regression models, and marginal adjusted risk ratios and 95% CIs were estimated to describe factors associated with aHF or aIHD.
Results: Among 89 999 adults with laboratory-confirmed influenza, 80 261 had complete medical record abstractions and available ICD codes (median age, 69 years [interquartile range, 54 to 81 years]) and 11.7% had an acute cardiovascular event. The most common such events (non–mutually exclusive) were aHF (6.2%) and aIHD (5.7%). Older age, tobacco use, underlying cardiovascular disease, diabetes, and renal disease were significantly associated with higher risk for aHF and aIHD in adults hospitalized with laboratory-confirmed influenza.
Limitation: Underdetection of cases was likely because influenza testing was based on practitioner orders. Acute cardiovascular events were identified by ICD discharge codes and may be subject to misclassification bias.
Conclusion: In this population-based study of adults hospitalized with influenza, almost 12% of patients had an acute cardiovascular event. Clinicians should ensure high rates of influenza vaccination, especially in those with underlying chronic conditions, to protect against acute cardiovascular events associated with influenza.

Eric J Chow, Melissa A Rolfes, Alissa O’Halloran, Evan J Anderson, Nancy M Bennett, Laurie Billing, Shua Chai, Elizabeth Dufort, Rachel Herlihy, Sue Kim, Ruth Lynfield, Chelsea McMullen, Maya L Monroe, William Schaffner, Melanie Spencer, H Keipp Talbot, Ann Thomas, Kimberly Yousey-Hindes, Carrie Reed, Shikha Garg


University of Washington Health Sciences material


Annals of Internal Medicine abstract

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