Influenza as a Cardiovascular Disease
Michael J. Bloch, MD
Associate Professor, University of Nevada School of Medicine
Medical Director, Vascular Care, Renown Institute for Heart and Vascular Health
President, Blue Spruce Medical Consultants, PLLC
Bloch MJ. Influenza as a cardiovascular disease. Consultant360. Published online December 2, 2021.
Anyone who has worked in a hospital acute coronary unit is well aware of the epidemiological link between influenza infection and cardiovascular (CV) events. Every winter, admissions for acute decompensated acute ischemic stroke, heart failure, and acute coronary syndromes tend to increase, and anecdotally it always seems that the worse the influenza season, the worse the CV admission rate. A landmark clinical trial published in the New England Journal of Medicine in 2018 objectively demonstrated that this effect is real and strong, with a 6-fold increase in the risk of myocardial infarction within 7 days of confirmed influenza infection.1
Acute influenza infection likely increases the risk of acute CV events in multiple ways.2 Like many other acute viral infections, acute influenza increases systemic inflammation, plasma viscosity, and sympathetic tone. It also leads to endothelial dysfunction and the release of prothrombotic cytokines. All of these effects can lead to acute plaque rupture in patients with vulnerable plaque. In addition, the psychological and physiological effects (including fever and dehydration) of acute illness can increase the risk of demand ischemia across fixed stenoses and hemodynamic instability in patients with left ventricular dysfunction.
This profound association and biological plausibility make the case for essentially universal influenza vaccination in patients with and at risk for CV disease. Yet, every year millions of Americans who are at risk for developing CV complications of influenza fail to get the vaccine. Previous studies have suggested that less than 50% of patients with established CV disease historically have received influenza vaccination.3,4 And, while data from the Centers for Disease Control and Prevention for the first part of the 2021-2022 season suggests that 58.5% of all adults have received or plan to receive the influenza vaccine this year,5 we still do not know the rate among older adults and those at higher risk. While rates are likely higher this year than historical averages, there are still millions of adults putting themselves at excess risk by not having an influenza vaccination plan.
A recent analysis published in the Journal of the American Heart Association highlights the potential benefits of influenza vaccination on CV morbidity and mortality.6 In this paper, the authors analyzed the results of 16 randomized controlled trials or observational studies involving 237,058 participants with CV disease at baseline. After a mean follow-up of 19.5 months, influenza vaccination was associated with a 25% lower risk of all-cause mortality, 18% lower CV mortality, and 13% fewer major CV events.
While lately being overshadowed by its distant cousin COVID-19, influenza remains a perennial seasonal threat that leads to excess CV risk. We will likely see an increase in influenza prevalence this year with the lifting of most COVID-19–related isolation precautions in the United States. Influenza vaccination remains a key component of the standard of care for patients with and at risk for CV disease. Health care providers need to remain relentless advocates for both a complete series of COVID-19 vaccination, COVID-19 boosters, and a seasonal influenza vaccine in all at-risk adults.
1. Kwong JC, Schwartz KL, Campitelli MA, et al. Acute myocardial infarction after laboratory-confirmed influenza infection. N Engl J Med. 2018;378(4):345-353. https://doi.org/10.1056/nejmoa1702090
2. Madjid M, Aboshady I, Awan I, Litovsky S, Casscells SW. Influenza and cardiovascular disease: is there a causal relationship? Tex Heart Inst J. 2004;31(1):4-13. http://www.ncbi.nlm.nih.gov/pmc/articles/pmc387426/
3. Singleton JA, Wortley P, Lu PJ. Influenza vaccination of persons with cardiovascular disease in the United States. Tex Heart Inst J. 2004; 31:22–27 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC387428/
4. Grandhi GR, Mszar R, Vahidy F, et al. Sociodemographic disparities in influenza vaccination among adults with atherosclerotic cardiovascular disease in the United States. JAMA Cardiol. 2021; 6:87–91. https://doi.org/10.1001/jamacardio.2020.3978
5. Weekly national flu vaccination dashboard. Centers for Disease Control and Prevention. November 16, 2021. Accessed: December 1, 2021. https://www.cdc.gov/flu/fluvaxview/dashboard/vaccination-dashboard.html
6. Yediapati SH, Khan SU, Talluri S, et al. Effects of influenza vaccine on mortality and cardiovascular outcomes in patients with cardiovascular disease: a systematic review and meta-analysis. J Am Heart Assoc. 2021;10(6):e019636. https://doi.org/10.1161/jaha.120.019636