Chronic congestive heart failure, usually right-sided, may ensue with edema of the legs, ascites and weakness. When a mass of worms lodge in the posterior vena cava the obstruction may lead to the vena caval syndrome, characterized by hemoglobinuria, anorexia, icterus and collapse. Death usually ensues within several days.
Among the pathologic changes seen in the various manifestations of heartworm disease are: pulmonary embolism, endocarditis of heart valves, glomerulonephritis due to immune complexes, pulmonary endoarteritis and eosinophilia even to pneumonia.