ABSTRACT
The literature on caval syndrome has highlighted a central role that the presence of large numbers of adult Dirofilaria immitis in the thoracic, posterior vena cava was thought to play in the pathogenesis of caval syndrome. Jackson et al., while speculating on the pathophysiology of caval syndrome, questioned why large numbers of D. immitis were found in dogs presented with caval syndrome. Selective, plasma-hemoglobin sampling the site of artificial threads in the model of caval syndrome showed that hemolysis was associated with the flow of blood through the mass of threads. In the experimental model, dogs with caval syndrome did develop thrombocytopenia and did develop bizzare platelet forms suggestive of platelet activation and aggregation. At necropsy of caval syndrome cases large numbers of worms are seen, usually in the right-atrial area, the dogs have evidence of intravascular hemolysis and have a variable degree of routine pathology due to D. immitis.
