Infection and coronary heart disease.

A large body of evidence exists that implicates a number of microbial agents in the pathogenesis of coronary heart disease (CHD). This, if proven, may have far-reaching implications for the prevention and treatment of CHD and other atherosclerotic disease. The histopathology of atherosclerosis and its natural history suggest infectious causation at many points along the progression of disease, particularly with regard to CHD, and a number of pathogens have been the focus of study. Viral agents implicated include Coxsackie B4 virus, for which tenuous sero-epidemiological associations exist, and the Herpesviridae. The animal herpesvirus causing Marek's disease in chickens causes atherosclerotic lesions in these animals. Herpes simplex virus I and II have been found in aortic smooth muscle and produce changes in vitro in smooth muscle that are similar to those seen at the beginning of atherosclerosis and which may also explain some of the features of atherosclerotic complications. Cytomegalovirus is implicated more strongly sero-epidemiologically by in-vivo detection in atherosclerotic lesions and by its links with post-cardiac transplant vasculopathya syndrome similar to atherosclerosis. Bacteria have also been shown to have links with CHD. Chlamydia pneumoniae and Helicobacter pylori have both been associated sero-epidemiologically with CHD, and these findings have been consolidated by recent work showing their presence in atherosclerotic lesions in adults. Bacterial infections in general lead to many changes in lipid, thrombic and other acute-phase protein metabolism, and some of these changes occur with both C. pneumoniae and H. pylori infections. The ubiquity and similar epidemiological features to CHD of all these microbial pathogens make the resolution of the causative issue impossible by retrospective means. All that can be shown at present are a variety of weak and strong links, the significance of which can only be determined by large and perhaps lifetime prospective studies.