Several previous studies have shown a significant association between ischemic heart disease and various infective agents including Cytomegalovirus and Chlamydia pneumoniae. However, information regarding the association between Helicobacter pylori and ischemic heart disease has been contradictory. This might be explained by the genetic polymorphism of H. pylori. The more virulent strains of H. pylori bear the cytotoxin-associated gene-A (CagA), which is associated with severe forms of gastroduodenal diseases, including peptic ulcer and gastric cancer. Pasceri and associates conducted a controlled study to assess the prevalence of infection by the more virulent strains of H. pylori bearing the CagA antigen in patients with ischemic heart disease.

A total of 88 consecutive patients with severe unstable angina (27 patients), acute myocardial infarction (34 patients) or chronic stable angina (27 patients) for longer than one year were included in the study. All patients had angiographically confirmed ischemic heart disease. Eighty-eight control subjects were also recruited. Specific anti– H. pylori was measured by use of a commercial enzyme-linked immunosorbent assay (ELISA). Anti– H. pylori IgGs were detected in 55 of 88 patients with ischemic heart disease, compared with 35 of 88 control subjects. The prevalence of infection with H. pylori was similar in patients with acute myocardial infarction, unstable angina and chronic stable angina. A total of 38 of 88 patients and 15 of 88 control subjects were infected by CagA–positive H. pylori. CagA–negative strains of H. pylori had a similar prevalence in both groups and were not associated with increased risk of ischemic heart disease.

Results indicate that infection with more virulent CagA–positive strains of H. pylori is significantly associated with ischemic heart disease, whereas CagA–negative strains have a similar prevalence in both patients and control subjects. The possible mechanisms are unknown, but recent studies have demonstrated that the presence of an inflammatory response has a prognostic value in patients with unstable angina and may predict the long-term risk of cardiovascular events in patients with chronic stable angina and in healthy men. The results suggest that CagA–positive H. pylori cannot directly induce coronary atherosclerosis but may need the presence of other cofactors to stimulate progression of ischemia.

The authors conclude that an association between ischemic heart disease and chronic infection with virulent strains of a microorganism is apparent. This finding supports the hypothesis that the pathogenetic link between chronic infections and ischemic heart disease may be the chronic inflammatory response caused by these infections.