Chlamydia pneumoniae in coronary plaques: Increased detection with acute coronary syndrome

Background and objective: There is seroepidemiologic and experimental evide nce for a link between Chlamydia (C.) pneumoniae and arteriosclerosis. Howe ver, the clinical importance and the pathogenic pathways implicated remain unclear. In the present study, we sought to evaluate the presence and the l ocation of C. pneumoniae in coronary atheroma, as well as a potential preva lence with unstable versus stable angina. Patients and methods: Retrospectively, coronary plaque material of primary lesions from 51 consecutive patients (44 men, 7 women, mean age 59,6 +/- 9, 4 years) was examined for the presence of C. pneumoniae by use of immuno-hi stochemistry and transmission electron microscopy. The findings associated with clinically acute coronary syndrome according to Braunwald's classifica tion (n=31)were compared to those with stable angina (n = 20) and regarded for potential relations to characteristic intimal features. Results: Immunoreaction for C. pneumoniae was found in 32 of 51 (63%) coron ary plaques. Signals (% prevalence of specific intimal features) were prese nt with necrotic areas (40%), sparse cellularity (40%), neo-vascularization (29%), thrombi (20%), ruptured plaque areas (19%), and fields rich in foam cells and calcifications (13%). Intimal hyperplasia and inflammatory infil trates showed no signals. As the central finding in this report, C. pneumon iae immunoreaction was more frequently (P < 0.001) found in 26 of 31 (84%) lesions associated with unstable angina or acute myocardial infarction, com pared to 6 of 20 (30%) lesions with stable angina (P < 0.001). Intact vesse ls devoid of arteriosclerotic disease, such as mammarial arteries and saphe nous veins, were without C. pneumoniae signals (negative controls). Ultrast ructurally, chlamydial elementary bodies were found in foam cells and phago cy-tosing macrophages, also in fragmented extracellular matrix adjacent to apoptotic and necrotic intimal cells. Conclusions: Chlamydiae pneumoniae were detected in 32 of 51 (63%) coronary primary lesions of symptomatic patients. Most importantly, there was a hig hly significant prevalence of lesions associated with acute coronary syndro me. Predilection sites of C. pneumoniae were areas that revealed small heal ing activity and (or) propensity to plaque rupture. The present in situ fin dings indicate a pathogenic role of Chlamydiae pneumoniae in human (coronar y) plaque rupture.