In cases of clinical failure in patients hospitalized for community-acquired pneumonia, acute myocardial infarction (AMI) "should be considered as a possible etiology," investigators report in the July issue of Clinical Infectious Diseases.
"The symptoms of pneumonia, such as chest pain and difficulty breathing, are the same symptoms for AMI," lead investigator Dr. Julio Ramirez of the University of Louisville, Kentucky, commented during an interview with Reuters Health. "Unless the doctors suspect AMI, they may consider that the symptoms are from the baseline pneumonia."
Dr. Ramirez and colleagues conducted an observational, retrospective study involving 500 patients hospitalized at the Veterans Hospital of Louisville with community-acquired pneumonia (CAP).
The researchers defined clinical failure as the development of respiratory failure or shock. AMI was diagnosed by abnormal troponin levels and electrocardiogram findings.
On admission, AMI was present in 13 (15 per cent) of the 86 patients with severe CAP. "During hospitalization, AMI was present in 13 (20 per cent) of 65 patients who experienced clinical failure," the team reports.
"Some patients arrived at the hospital with both pneumonia and AMI. In other patients AMI developed after they were hospitalized," Dr. Ramirez pointed out. "We think that first the patients developed pneumonia and then AMI."
After adjusting for risk, AMI was significantly associated with the pneumonia severity index score and with clinical failure.
"The link is probable," the Louisville investigator continued. "First, a patient has coronary artery disease, with a plaque in the coronary arteries, but he is clinically stable. Second, the patient develops pneumonia. Third, due to the pneumonia, the heart rate increases. The more work to the heart, the more the oxygen level decreases."
"Less oxygen going to the heart, plus the extra work of the heart, plus a previous partial obstruction of the arteries (results in) the AMI," Dr. Ramirez said.
"Physicians should be aware that every patient that develops pneumonia, who has some problem with atherosclerosis, is automatically at increased risk of AMI," he concluded.
Clin Infect Dis 2008;47:182-187
