Caval syndrome is an acute manifestation of heartworm disease in which increased pulmonary hypertension and decreased cardiac output allows for the retrograde distribution of Dirofilaria immitis worms within the heart and vena cava. The patient of interest is a 9-year-old, female spayed, Pomeranian with a history of a cough, cyanosis and increased respiratory effort, among other significant abnormal physiologic and hematologic findings. She was diagnosed with heart-worm infection and was determined to be microfilaremic, via antigen testing and microscopic visualization of microfilariae in a single drop of blood, respectively. Diagnostic imaging con-firmed the presence of heartworms within the pulmonary artery and right heart as well as exten-sive cardiac changes including right-sided cardiomegaly and severe pulmonary hypertension. Medical management was used to improve cardiac output, followed by surgical extraction of the parasites. The remaining heartworms were treated following the American Heartworm Society’s treatment protocol. Two months following initiation of medical management and surgical extrac-tion of the worms, the patient had greatly improved physiologically and hematologically, and re-ceived her first adulticide injection.