Intrapulmonary arteriovenous anastomoses in dogs with severe Angiostrongylus vasorum infection: clinical, radiographic, and echocardiographic evaluation

BACKGROUND: In both humans and dogs the pulmonary vasculature is able to recruit large-diameter anatomical intrapulmonary arteriovenous anastomoses (IPAVAs). In healthy people the opening of these anastomoses affects the degree of exercise-induced increase in pulmonary arterial pressure. The presence of these IPAVAs can be demonstrated using saline contrast echocardiography. OBJECTIVES: The aims of the present study were to characterize severely affected, naturally infected dogs with Angiostrongylus vasorum, to evaluate if these dogs can open IPAVAs, and to assess if the recruitment of such anastomoses affects the severity of pulmonary hypertension (PH). ANIMALS: Eight client-owned dogs with severe A. vasorum infection were recruited. METHODS: Dogs with A. vasorum infection that presented with severe dyspnea and/or syncope were prospectively screened by echocardiography for the presence of PH and IPAVAs. Only severely affected dogs, based on a combination of clinical, radiographic and echocardiographic abnormalities, were enrolled. RESULTS: Opening of IPAVAs could be demonstrated in three dogs with no to moderate PH, and could not be demonstrated in five dogs with severe PH. In two dogs thoracic radiographs showed only mild interstitial changes, while computer tomography and postmortem examination revealed severe pulmonary interstitial and vascular disease. CONCLUSIONS: These results suggest that dogs may open IPAVAs and that opening of such anastomoses may play a regulatory role in the development of PH. There may be a marked discrepancy between radiographic changes and disease severity in A.vasorum