Summary

Background: Recent studies have suggested a possible association between Chlamydia pneumoniae infection and coronary heart disease.

Objectives: To determine titers of antibodies to Chlamydia pneumoniae in patients with acute  myocardial infraction compared with titers in several control groups.

Methods: This prospective case-control study investigated 209 individuals. We assessed the serum IgG antibody titers to Chlamydia pneumoniae in 57 consecutive patients admitted with AMI to our intensive coronary care unit during a 4 month period. A serum sample was drawn upon admission after 6 weeks. Results were compared with those of four control groups: a) patients admitted with community-acquired pneumonia (n=18), b) patients with community-acquired urinary tract infection (n=42), c) patients with angiographically normal coronary artery disease (n=44), and d) patients with stable coronary artery disease (n=48). Serum immunoglobin G antibody titers to C. pneumoniae were determined using standard micro-immunofluorescene technology.

Results: Of 57 patients with AMI, 32 (56%) had a high lgG titer to C. pneumoniae (>=1:256) on the initial test, which remained unchanged (62%) after 6 weeks. The percentage of patients with high titers was significantly lower in the control groups: 5 of 18 patients (28%) in the pneumonia group (P<0.01), 11 of 42 (26%) in the urinary tract infection group (P<0.01), 11 of 44 (25%) with normal coronary arteries (P<0.01), and 17 of 48 (35%) with stable chronic ischemic heart disease (P<0.05).

Conclusion: The detection of high titers of lgG antibodies to C. pneumoniae in many patients with AMI, compared to control groups, suggest that chronic Chlamydia pneumoniae infection plays a role in the pathogenesis of atherosclerosis and acute ischemic events.