Clinical studies on canine dirofilarial hemoglobinuria: relationship between the presence of heartworm mass at the tricuspid valve orifice and plasma hemoglobin concentration.

Abstract

A heartworm mass was confirmed by echocardiography at the tricuspid valve orifice of dogs with dirofilarial hemoglobinuria (caval syndrome). It disappeared by surgical heartworm removal, and the symptoms of "caval syndrome" also improved. The plasma hemoglobin concentration, which was very high before heartworm removal, decreased 30 min after heartworm removal. It fell progressively to almost the normal level 20 hr after heartworm removal. In 5 dogs developing the caval syndrome after milbemycin D administration, the presence of heartworms at the tricuspid valve orifice and the increase of plasma hemoglobin concentration were observed to occur simultaneously. These findings suggest that the heartworm mass at the tricuspid valve orifice may be a direct cause of the onset of this disease, and these heartworms may trigger the increased intravascular hemolysis.