ELEVATED CHLAMYDIA-PNEUMONIAE ANTIBODIES, CARDIOVASCULAR EVENTS, AND AZITHROMYCIN IN MALE SURVIVORS OF MYOCARDIAL-INFARCTION

Background The clinical significance of the association between elevat ed anti-Chlamydia pneumoniae (Cp) antibody titres and coronary heart d isease (CHD) is unclear. We explored the relationship between antibodi es against Cp and future cardiovascular events in male survivors of my ocardial infarction (MI). The effect of azithromycin antibiotic therap y was assessed in a subgroup of post-MI patients. Methods and Results We screened 220 consecutive male survivors of MI for anti-Cp antibodie s. Of these, 213 patients were stratified into three groups: group Cp- ve (n=59), no detectable tip antibodies; group Cp-I (n=74), intermedia te titres of 1/8 to 1/32 dilution; and group Cp+ve (n=8), seropositive at greater than or equal to 1/64 dilution. Patients with persisting s eropositivity of greater than or equal to 1/64 were randomized to eith er oral azithromycin (Cp+ve-A, 500 mg/d for 3 days [n=28] or 500 mg/d for 6 days [n=12]) or placebo (Cp+ve-P, n=20). Cp+ve-NR (n=20) represe nted patients not recruited into the antibiotic trial. The incidence o f adverse cardiovascular events (over a mean follow-up period of 18+/- 4 months) was recorded and shown to increase with increasing anti-tip titre: Cp-ve, n=4 (7%); Cp-I, n=11 (15%); Cp+ve-NR, n=6 (30%); and Cpve-P, n=5 (25%). Cp+ve-NR and Cp+ve-P groups had a fourfold-increased risk for adverse cardiovascular events compared with the Cp-ve group ( odds ratio [OR], 4.2; 95% confidence interval [CI], 1.2 to 15.5; P=.03 ). In contrast, the OR for cardiovascular events in patients receiving azithromycin (Cp+ve-A, single or double course) was the same as in th e Cp-ve group (OR, 0.9; 95% CI, 0.2 to 4.6, P=NS). Patients receiving azithromycin were more likely to experience a decrease in IgG anti-Cp titres than were these in the placebo group (P=.02). Conclusions An in creased anti-Cp antibody titre may be a predictor for further adverse cardiovascular events in post-MI patients. Taking a short course of az ithromycin may lower this risk, possibly by acting against Cp.