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Text sizeHouston, TX -A distinguished group of experts in influenza, virology, atherosclerosis and cardiovascular disease, public health policy, and epidemiology gathered recently in Houston, TX to discuss the role of influenza in the development of atherosclerosis and the effect of influenza vaccination in preventing MI.
The First Symposium on Influenza and Cardiovascular Disease: Science, Practice, and Policy held at the Texas Heart Institute in Houston on April 26, 2003 brought together US and international physicians; representatives from the Centers for Disease Control and Prevention, the Department of Health and Human Services, and the National Heart, Lung, and Blood Institute; and several industry leaders to share their expert opinions.
The goal of the symposium, said faculty cochair Dr Mohammad Madjid (University of TexasHouston Health Science Center), was to discuss the need for better vaccination policies and the benefits of increased vaccination rates in high-risk cardiac patients.
We know that the flu vaccine is safe and effective, it is inexpensive, and it can save lives. However, it is also tremendously underutilized.
"In the past two years, new data have emerged about the health benefits of receiving the flu shot, especially for patients with heart disease," said Madjid. "We know that the flu vaccine is safe and effective, it is inexpensive, and it can save lives. However, it is also tremendously underutilized."
Conference cochair Dr Ward Casscells (University of TexasHouston Health Science Center) told heartwire the idea for the conference emerged from clinical practice.
"Time and time again, we were seeing people in our practice who had had an upper-respiratory problem and then suffered a heart attack," said Casscells. "When we dug into the literature we saw reports that many heart attacks, as many as 35%, were preceded by an upper-respiratory problem. We also saw that patients who had received their flu shots were less likely have a heart attack."
An old idea revisited
According to a recently published study in the Journal of the American Medical Association, influenza, on average, is associated with 8097 pneumonia-influenza deaths, 36155 underlying respiratory and circulatory deaths, and 51203 all-cause deaths every year.1 The Houston conference was developed to highlight new evidence linking cardiovascular disease and the influenza virus and to look for ways to promote vaccination use in high-risk cardiac patients.
In an interview with heartwire, Madjid said the inflammatory origin of atherosclerosis has recently brought infection back into limelight. A virus of remarkable morbidity and mortality, influenza is an acute, recurring, prevalent disease associated with a massive release of cytokines, which may contribute to the increased risk of MI and stroke in unvaccinated patients, said Madjid.
Other potential mechanisms have been suggested, including the role acute influenza infection may have in causing the exacerbation of inflammation in plaques. The inflammation destabilizes vulnerable plaque, leading to thrombosis and triggering MI. Flu-related release of endogenous catecholamines, endothelial dysfunction, platelet aggregation, and plasma viscosity and the ability of the virus to damage the anti-inflammatory properties of HDL particles have all been theorized as potential mechanisms underlying the link between the virus and CVD.
Healthy People 2010, the national health prevention strategy, has recommended that 90% of the US population over the age of 65 be vaccinated against the influenza virus by the year 2010. Current vaccination rates still fall well short of this goal, especially in patients with heart disease.
"Physicians often will check blood pressure, check cholesterol, ask about exercise, and discuss other risk factors, but for some reason they often stop just short of telling patients to get their flu shot," said Madjid. "We have had some difficulty getting the message out, both with physicians and with patients."
Casscells and Madjid agreed there is a need for prospective randomized trials to determine whether the flu vaccine is protective against MI. Small case-controlled studies have suggested the association exists but definitive proof is still lacking. Large observational studies, however, continue to point to an intriguing association between vaccination and reductions in MI.
One study, published recently in the New England Journal of Medicine and presented in Texas by Dr Kristin Nichol (VA Medical Center and the University of Minnesota, Minneapolis) suggests the influenza vaccine may significantly reduce the rate of hospitalization for cardiac disease and stroke as well as dramatically reduce all-cause mortality.2 The observational, double-cohort study involved more than 280000 patients.
Astonishing results with very little fanfare
According to Casscells, the cardiology community needs to work harder to make physicians aware that their patients over the age of 65, and especially those with risk factors for CVD, should be vaccinated against influenza. The Nichol study and others from around the world continue to make a case for vaccination to protect against cardiovascular events, said Casscells. However, he admits there is little financial incentive to ensure the vaccination message isn't "lost in the noise."
If you had to choose between a lifetime supply of ACE inhibitor, beta blocker, statin, or a flu shot, you're going to choose the annual flu shot.
"My guess is that getting the flu shot probably reduces the risk of heart attack, stroke, or sudden death by 20% or 25%. This is in the same range as aspirin and beta blockers and in the same realm as ACE inhibitors, but it is much, much more cost effective. If you had to choose between a lifetime supply of ACE inhibitor, beta blocker, statin, or a flu shot, you're going to choose the annual flu shot."
Social and policy issues, such as a lack of physician remuneration for giving the flu shot and financial biases in favor of more expensive medications, as well as an inability to effectively target minorities for vaccination prevent widespread inoculation, said Casscells.
