Why are people with Coronary Artery Disease (CAD) at a higher risk of dying from influenza?

Why People with CAD Die from Influenza

People with coronary artery disease die from influenza because the viral infection directly destabilizes atherosclerotic plaques, triggers acute coronary syndromes, accelerates vascular inflammation, and causes hemodynamic stress that overwhelms already compromised cardiac function—making them more vulnerable to death from influenza than patients with any other chronic disease. 1

Direct Pathophysiologic Mechanisms

Plaque Destabilization and Acute Thrombosis

• Influenza infection promotes rupture of vulnerable atherosclerotic plaques, directly precipitating acute coronary syndromes in patients with established CAD 1
• The inflammatory response to viral infection produces autoantibodies to modified low-density lipoprotein, which accelerates atherosclerotic vascular injury and plaque progression 1
• Direct viral colonization of vessel walls initiates local autoimmune reactions by activating antigen-presenting cells, further destabilizing existing plaques 1

Systemic Inflammatory Cascade

• The systemic inflammatory response triggered by influenza exacerbates underlying coronary atherosclerosis by activating inflammatory pathways that worsen pre-existing disease 2
• This inflammatory activation leads to higher rates of complications, hospitalizations, and death compared to healthy individuals 1

Cardiac Decompensation Mechanisms

Hemodynamic Stress

• Influenza causes fluid overload and heart failure decompensation in patients with compromised cardiac reserve from CAD 1
• Viral pneumonia, secondary bacterial pneumonia, or co-infections place additional hemodynamic stress on diseased coronary circulation 1

Direct Myocardial Involvement

• Direct myocardial involvement presenting as myocarditis can occur during influenza infection, with clinical presentation varying from asymptomatic to fulminant myocarditis resulting in cardiogenic shock and death 3

Epidemiologic Evidence of Excess Mortality

Unique Vulnerability

• Influenza-related death occurs more frequently among individuals with cardiovascular disease than among patients with any other chronic condition, underscoring the unique vulnerability of this population 1
• Cardiovascular mortality increases during influenza epidemics in patients with pre-existing coronary artery disease 3
• Rates of myocardial infarction have been shown to increase following influenza outbreaks 3

Temporal Association

• An increasing number of epidemiologic studies have concluded that a temporal association exists between acute viral illnesses and myocardial infarction 2
• Influenza epidemics are associated with an increased rate of cardiovascular events 4

High-Risk Clinical Scenarios

Post-Acute Coronary Syndrome Period

• The period immediately following acute coronary syndromes represents particularly high vulnerability, as demonstrated by the FLUVACS trial showing 8% cardiovascular mortality in unvaccinated post-MI patients versus 2% in vaccinated patients at one year 1

Age-Related Compounding

• Patients at extremes of age with coronary artery disease face compounded risk from both age-related and disease-related factors 1

Protective Evidence Supporting the Mechanism

Vaccination Benefit

• Influenza vaccination reduces cardiovascular events with a relative risk of 0.64 (95% CI 0.48-0.86) in high-risk cardiovascular patients, with greatest benefit in those with more active coronary disease 1
• Decreases in cardiovascular mortality have been demonstrated following influenza vaccination in high-risk patients 3
• A meta-analysis demonstrated a pooled relative risk of 0.39 (95% CI 0.20-0.77) for cardiovascular death in vaccinated patients compared with placebo 2

Critical Clinical Pitfalls

Underestimating Severity

• Do not underestimate the severity of risk—coronary artery disease patients face higher influenza-related mortality than any other chronic disease population, requiring aggressive prevention 1
• The risk of influenza infection in an unvaccinated coronary artery disease patient is substantial and potentially fatal 1

Vaccination Implementation

• Despite Class I, Level B recommendations from the AHA/ACC for annual influenza vaccination in all patients with coronary and other atherosclerotic vascular disease, vaccination coverage levels among persons with CVD remain only 34% nationally 4, 5
• Influenza vaccination should be recommended with the same enthusiasm as control of cholesterol, blood pressure, and other modifiable risk factors 4