ICAAC-IDSA: Pneumonia Linked to Acute Coronary Syndrome
WASHINGTON, Oct. 27 -- Patients hospitalized with bacterial pneumonia have about eight times the risk of acute coronary syndrome as those admitted for other causes, a researcher said here. The risk is highest within 15 days of admission, said Vicente Corrales-Medina, M.D., of Baylor College of Medicine in Houston. The association -- found in a retrospective case-control analysis -- is "so striking" it suggested a causal relationship, Dr. Corrales-Medina said at the Interscience Conference on Antimicrobial Agents and Chemotherapy, held jointly with the Infectious Diseases Society of America meeting. "There is evidence that suggests that acute infections -- not just pneumonia -- can cause acute changes in atherosclerotic plaques," Dr. Corrals-Medina said. Such changes, combined with effects of pneumonia such as respiratory stress, might lead to acute coronary syndromes, including unstable angina or myocardial infarction, he said. Dr. Corrales-Medina and colleagues analyzed the records of 206 patients admitted to the Michael E. DeBakey VA Medical Center in Houston with a clinical, radiological, and bacteriological diagnosis of pneumonia from January 2000 through December 2006. Of those cases, 144 were caused by Streptococcus pneumoniae and 62 by Haemophilus influenzae, Dr. Corrales-Medina said. For a control group, the researchers identified 395 patients admitted with a diagnosis that was neither pneumonia nor acute coronary syndrome, who were matched by date and time of admission. When the two groups were compared, 22 of the pneumonia patients (10.7%) had acute coronary syndrome within 15 days of admission, compared with six (1.5%) of the controls, Dr. Corrales-Medina said. In a univariate analysis, he said, the odds ratio was 7.8, with a 95% confidence interval from 3.1 to 19.4, which was significant at P
<0.001. When the researchers adjusted for possible confounding factors, the pneumonia remained a significant factor, with an odds ratio of 8.5 (and a 95% confidence interval from 3.35 to 22.23), which was again significant at P
<0.001. In another analysis, the researchers looked at 36 patients who had suffered acute coronary syndrome at least once during the year before and the year after admission for pneumonia. In effect, the patients acted as their own controls, Dr. Corrales-Medina said. The analysis showed the coronary syndrome tended to cluster in the "at-risk" period of 15 days after admission, he said. Specifically, 21 (58%) of the events occurred during the at-risk period, for a relative incidence ratio of 47.6, with a 95% confidence interval from 24.5 to 92.5. "That's what you'd expect to see if the pneumonia was causing the syndrome," he said. But Dr. Corrales-Medina cautioned that further studies are needed to discern whatever mechanism is involved, he said, because his retrospective study can't prove there's a causal link. "The study is very neat because it gives a very, very clear practical message," said Lindsay Grayson, M.D., of the Austin Hospital in Melbourne, Australia, who was not part of the study. "If you've got someone with pneumonia, check that they haven't had a silent heart attack," he said. On the other hand, Dr. Grayson said, the study isn't able to pin down the cause, and it could be that patients with mild heart failure are more prone to pneumonia, which then triggers a more acute syndrome. "The question that came to my mind was: is it actually the other way around?" he said. The study by Dr. Corrales-Medina was one of two presented here that looked at the issue of heart outcomes in the context of community-acquired pneumonia. In the other, researchers at the University of Louisville found that at admission, 15% of 500 patients with severe pneumonia also had a myocardial infarction. During their stay in the hospital, 20% of patients who suffered clinical failure also had an MI. The researchers concluded that acute MI is common among patients admitted to the hospital with community-acquired pneumonia and should be suspected as an etiology in clinical failure. Dr. Corrales-Medina did not report any external support or any conflicts. Primary source: ICAAC-IDSA MeetingSource reference:Corrales-Medina VF, et al "Acute Bacterial Pneumonia is Associated with the Occurrence of Acute Coronary Syndromes" ICAAC-IDSA 2008; Abstract L-671. Additional source: ICAAC-IDSA MeetingSource reference: Peyrani P, et al "Acute Myocardial Infarction in Hospitalized Patients with Community-Acquired Pneumonia: Results from the CAPO International Study" ICAAC-IDSA 2008; Abstract L-914.