Pneumonia patients at increased risk of acute cardiac events

June 29, 2007

Houston, TX - A new study has found that almost 20% of patients hospitalized with bacterial pneumonia also had one or more major cardiac events at the time of admission[1]. This frequent coexistence of conditions is often missed by doctors, however, say Dr Daniel M Musher (Veterans Affairs Medical Center, Houston, TX) and colleagues in their paper published in the July 15, 2007 issue of Clinical Infectious Diseases.

"Physicians tend to look for a single, unifying diagnosis," Musher told heart wire . "If a patient is admitted with chest pain, they are thinking of heart attack and are not paying attention to the white-cell count or the chest X ray. . . . But a surprising amount of patients with acute cardiac events may have pneumonia, too," he says, adding that he believes cardiologists and generalists in particular have tunnel vision when it comes to this issue.

Musher says he believes this paper is one of the most important he has written and says it was initially rejected by the American Journal of Medicine, which "didn't even consider it." But this topic needs airing, he believes, for patients to receive better care.

Those with pneumonia and cardiac events had higher mortality

Musher and colleagues studied 170 patients admitted to the Michael E DeBakey Veterans Affairs Medical Center in Houston with pneumococcal pneumonia during a five-year period from 2001 to the end of 2005.

They found that 33 (19.4%) had one or more associated major cardiac events. Because some patients with MI also had arrhythmias and CHF and some who had arrhythmias experienced worsening congestive heart failure, there were a total of 46 major cardiac events observed in these 33 patients

Adding a note of caution, however, the authors acknowledge that the population—made up of veterans—was relatively elderly, with a high prevalence of tobacco abuse, and as such, they may have had a higher likelihood of underlying CAD.

Nonetheless, they found that the concurrence of a cardiac event with pneumonia strongly correlated with in-hospital death—those with pneumonia and cardiac events had a significantly higher mortality than those with pneumonia alone (p<0.008).

Major cardiac events in 170 consecutive patients admitted for pneumococcal pneumonia

Event Patients, n
MI 12
New arrhythmia 2
New or worsening CHF 5
New arrhythmia 8
New or worsening CHF 6
New or worsening CHF 13
Total patients with cardiac event 33

"The concurrence of pneumonia and a new cardiac event was often unrecognized, especially in the first 12 to 24 hours of hospitalization, resulting in some patients not receiving antibiotics for pneumonia and others not receiving cardiac monitoring or anticoagulant therapy," Musher and colleagues observe.

They add that although an association between cardiac events and pneumonia was noted in the first half of the 20th century, "the recent medical literature has generally not addressed the concurrence of pneumonia and new cardiac events."

One exception to this, however, was a recent study[2] that specifically sought noncardiac conditions in patients who had acute MI, which found that 7.2% of the patients had pneumonia, they note, adding that those authors also emphasized the tendency of admitting physicians to confine their assessment to a single diagnosis.

Several mechanisms may explain link

Several mechanisms may explain the association between pneumonia and acute cardiac events, the researchers note.

Infection is analogous to extreme physical stress, which has been associated with a two- to 10-fold increased risk for acute MI in epidemiologic studies, they explain. Infection also increases levels of C-reactive protein (CRP), fibrinogen, and inflammatory cytokines, which may increase the risk for thrombogenesis and which independently predicts an increased likelihood for acute coronary syndromes.

The pathogenesis of arrhythmia and CHF in pneumonia is also multifactorial, they state, and includes increased myocardial demand for oxygen, lowered blood-oxygen levels, and suppression of ventricular function by elevated levels of cytokines.

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