Can This One Deadly Disease (Pneumonia) Trigger Another (MI)?

Acute bacterial infections can elevate the risk for cardiac events, but the question of whether or not invasive pneumococcal disease (IPD) can trigger acute myocardial infarction (AMI) remains unanswered.

Not that experts aren’t looking for answers. In a new retrospective cohort study, authors at Vanderbilt University Medical Center conducted a self-controlled case series study exploring the short- and long-term associations between IPD and AMI.¹ The authors used state laboratory- and hospital-based surveillance data to review 324 cases of laboratory-confirmed IPD that occurred within a year before or after patients were admitted for an AMI episode. This data spanned from 2003 to 2019.

When is the risk of AMI the highest?

The risk of AMI spiked during active IPD episodes compared to non-IPD control episodes, particularly in the first week of infection. The incidence of AMI was significantly higher in the seven days before IPD was detected (incidence rate ratio [IRR] 10.29), as well as during the current IPD period (IRR 92.95), which lasted seven days after specimen collection. More than 85% of patients with IPD had a specimen collected on the day they were admitted for an AMI episode.

Lead author Andrew Wiese, PhD, MPH, an assistant professor in the Department of Health Policy at Vanderbilt University Medical Center, commented on this finding: “Based on prior work for other infection types, we hypothesized that there would be an increased risk of heart attacks, but were surprised by the degree of the association,” he says. “We also found it interesting that the increased heart attack risk was not restricted to older adults, either, as we saw consistent findings among adults both younger and older than 65 years of age.”

AMI risk: timing is everything

The timing of AMI relative to invasive infection was a key finding, which indicates that the risk of heart attack is elevated even before active IPD infection can be validated via laboratory results. Dr. Wiese and his colleagues also emphasize that, in acute experimental myocarditis, myocardial injury can occur before inflammation, suggesting that infection can cause cardiac harm even before clinical warning signs appear.

In addition, it’s likely that the heightened risk for AMI persists both in the intermediate-term (8 to 28 days) and long-term periods (29 to 365 days) post-IPD. Compared with controls, AMI was seen more frequently 29 to 365 days after infection (IRR 2.95). Dr. Wiese highlights the takeaway of these results for clinicians: “Serious pneumococcal infections, such as pneumonia and sepsis, increase the risk of heart attacks. The increased risk is highest during the first week of the infection, but an elevated risk persists thereafter.” 

What mechanisms lie below?

The hypothesis that AMI can be triggered by IPD is rooted in prior work exploring other infections. Past studies have suggested a causal relationship between pneumonia and short-term heart attack risk, having investigated the cardiac threat of influenza and community-acquired pneumonia. The proposed mechanisms underlying these relationships, Dr. Wiese and his fellow researchers argue, may also induce AMI in the setting of IPD. 

While the literature drives at a relationship between pneumonia and cardiovascular events, the etiology of pneumonia in such studies remains an open question. In addition, the Vanderbilt authors point out, whether cardiovascular events can be caused by distinct pneumonia etiologies is a fertile area for prospective research. “Future work will be necessary to better understand the association between IPD and specific AMI types, as well as to identify the subgroups of patients with IPD and pneumococcal pneumonia at highest risk for cardiac events,” the authors wrote.¹

A call for vaccination 

Vaccination against IPD may serve the dual purpose of both curbing IPD and lessening the risk of major acute cardiovascular events.

“Physicians should ensure their patients are properly vaccinated to help prevent pneumococcal infections and their potential serious cardiovascular complications,” advises Dr. Wiese. He and his co-authors call for future studies to explore whether pneumococcal vaccination can safeguard patients against specific cardiac outcomes. Another avenue of research, they suggest, is whether various treatment strategies to target infection might actually increase the risk of subsequent cardiac events.

Published: June 09, 2023