Abstract
In ordef to examine the changes in hemodynamics inducing heartworm migration from the pulmonary artery, the pressures of the right ventricle and pulmonary artery and right cardiac output were measured after administration of 1.5mg/kg body weight of milbemycin D (Milbe) in 6 heartworm-infected dogs under general anesthesia. The heartworms migrated from the pulmonary artery to the tricuspid valve orifice and right atrium from 50 to 105 min after Milbe administration in 4 of the dogs. After Milbe administration, heart rate increased transiently, then subsequently decreased. Systolic right ventricular and mean pulmonary pressures did not show uniform changes in heartworm-migration cases. The right cardiac output decreased clearly before heartworm migration in all such cases. Stroke volume (right cardiac output/heart rate), cardiac index (right cardiac output/kg body weight) and stroke index (stroke volume/kg body weight) also decreased in heartworm-migration cases. The heartworm migration from the pulmonary artery towards the right atrium may be associated with the decreases of blood flow volume and velocity in the right heart.
