Chronic Infection May Contribute to Stroke Risk
Abstract & Commentary
Synopsis: The association between H pylori and acute cerebrovascular disease seems to be due to a higher prevalence of more virulent H pylori strains in patients with atherosclerotic stroke.
Source: Pietroiusti A, et al. Cytotoxin-associated gene-a-positive Helicobacter pylori strains are associated with atherosclerotic stroke. Circulation. 2002;106:580-584.
It is well known that chronic inflammation is a significant contributor to atherosclerotic disease. Serologic positivity for Chlamydia pneumoniae and Helicobacter pylori have been associated with atherosclerosis independent of other vascular risk factors. These organisms have been linked to disease in the coronary arteries, carotid system, and peripheral vasculature. Although H pylori often presents as peptic ulcer disease and chlamydia rarely produces pneumonia, these chronic infections are usually entirely asymptomatic and thus are rarely treated.
In the current report, Pietroiusti and colleagues present data linking a particularly virulent H pylori strain (bearing the cytotoxin-associated gene A [CagA]) with stroke due to atherosclerosis. Dividing stroke patients into etiologic subtypes, 138 patients with large vessel stroke were compared to 61 patients with cardioembolic infarcts and 151 healthy controls. H pylori infection in general was highly prevalent in all groups, occurring in approximately 70% of patients. The prevalence of CagA-positive strains, however, was much higher in patients with large vessel strokes (43%) than among patients with cardioembolism (20%) or controls (18%)—P < 0.001 for either comparison. C-reactive protein levels, indicating an inflammatory state, were also significantly higher in the presence of CagA.
Comment by Alan Z. Segal, MD
By dividing infarcts into specific subtypes, rather than treating them as a lump sum, Pietroiusti et al were able to make significant insights into stroke pathophysiology. These data indicate that inflammation appears to play a role in strokes mediated by atherosclerosis, but not strokes related to cardiac thrombi. Similarly, stroke is not associated with all H pylori infections (an exceedingly common phenomenon), but rather with a specific more virulent (and less common) strain.
In a related article, Franceschi and colleagues (Circulation. 2002;106:430-434) further elucidate this interesting link. In an ex vivo, immunochemical model, they demonstrate that Anti-CagA antibodies specifically bind to epitopes on atherosclerotic blood vessels. H pylori may, therefore, promote atherosclerosis through a much more discrete process than merely nonspecific inflammation. Antibodies made against CagA may cross react with antigens expressed by cells involved in atherogenesis such as vascular smooth muscle, fibroblasts, or endothelial cells.
While mass treatments with antibiotics to prevent stroke and myocardial infarction are not yet justified, there is compelling evidence that particular chronic infections may significantly contribute to vascular disease.
Dr. Segal is Assistant Professor, Department of Neurology, Weill-Cornell Medical College, Attending Neurologist, New York Presbyterian Hospital.
The association between H pylori and acute cerebrovascular disease seems to be due to a higher prevalence of more virulent H pylori strains in patients with atherosclerotic stroke.
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