Myocardial ischemia and infarction are associated with elevated Chlamydia pneumoniae IgA levels

Purpose: A growing body of literature has implicated the obligate intracellular bacterium, Chlamydia pneumoniae (CP), in the pathogenesis of atherosclerotic coronary artery disease (CAD). The purpose of the present study was to determine whether patients who rule in for myocardial ischemia or infarction are more likely to have serologic evidence of recent CP infection than those ruling out. Methods: Between August 1997 and February 1998, 70 patients were placed on the rule-out myocardial infarction (MI) protocol at our institution. Serum samples were drawn and analyzed for the presence of IgG, IgA and IgM antibodies to CP using a microimmunofluorescence assay. Patient demographics and risk factors for CAD were recorded in a database. Results: CP IgA levels were elevated in 21 of 70 patients (30%). Patients with elevated IgA levels were more likely to rule in for myocardial ischemia than those with normal titers (43% vs. 14%, p < 0.025). The relative risk of having myocardial ischemia with elevated IgA levels was 3.00. Of the 70 patients, 16 patients (23%) had objective evidence of myocardial ischemia or infarction (Group 1), while 54 patients (77%) did not (Group 2). CP IgA levels were more likely to be elevated in Group 1 patients (p < 0.025), although CP IgG levels, presence of hypertension (HTN), and hyperlipoproteinemia (HLP) were comparable between the groups. GROUP 1 n = 16 GROUP 2 n = 54 P value HIGH IgA 56% 22% < 0.025 HIGH IgG 81% 83% NS HTN 94% 72% NS HLP 62% 35% NS NS = Not Significant (P > 0.05) Conclusions: Elevated CP IgA titers are significantly more likely to be present in patients with objective evidence of myocardial ischemia or infarction. Clinical Implications: Acute infection or re-infection with Chlamydia pneumoniae may destabilize atherosclerotic plaques. Subsequent plaque rupture may result in myocardial ischemia and/or infarction.