Development and resolution of radiographic lesions in canine heartworm disease

Thoracic radiography of 7 Beagles was performed before heartworm infection, during a 1-year heartworm infection, and for 1 year following appropriate treatment. Cardiac and vascular lesions on thoracic radiographs were compared with angiographic changes. Within 3 months of obstructed blood flow in the caudal lobar arteries, associated increased focal parenchymal densities were detected. These lesions were regarded as characteristic of heartworm disease. Although the most severe arteriographic changes were in the caudal lobar arteries, lobar arterial changes on a lateral view were best detected in the right cranial lobar artery. These arteries increased in size during infection and decreased in size after treatment. It was concluded that the dorsoventral view is best for evaluation of the caudal lobar arteries. The most marked parenchymal lesions were detected during the first 6 months following adulticide treatment. These lesions and the other radiographic alterations then decreased in severity. Persistence of the parenchymal lesions were related to persistence of heartworm infection.