Case Studies In Small Animal

Cardiovascular Medicine

Home Up Follow-up Ishihara

Second Visit

Case 33

Clinical Diagnoses

bulletClass III heartworm infection with severe pulmonary hypertension
bulletHeartworm extraction

Plans and Progress Notes

bulletFirst Day 20:00 Problem #1 Heartworm w/ pulmonary hypertension-S/O: See pertinent history and physical examination. T=100.5, P=160, R=pant. Heartworm antigen test today was weak positive. Echocardiogram showed increase in chamber size of right atrium and right ventricle, along with right ventricular free wall concentric hypertrophy. Septal flattening is evident in systole and diastole. Pressure gradient across the tricuspid valve=70 mmHg, which indicates severe pulmonary hypertension. Heartworms were visualized in right pulmonary artery on echo. ECG shows S waves indicative of right ventricular enlargement. Thoracic radiographs show severely dilated pulmonary arteries (main, right and left branch). Also see radiopaque areas in lung which are suggestive of emboli. Fisher had a good appetite tonight and appeared comfortable in his run. A: Class III heartworm disease causing severe pulmonary hypertension and clinical signs of coughing and lethargy. Enlarged right heart chambers along with hypertrophied RVFW, systolic flattening of the interventricular septum, and the increased pressure gradient across the tricuspid valve indicate a severe acquired pressure overload due to pulmonary hypertension. ECG changes consistent with right ventricular hypertrophy. Dilated pulmonary arteries consistent with presence of heartworms. P: Surgically remove as many worms as possible from pulmonary arteries via right jugular vein. Pre-treat with prednisone 30 mg PO tonight and 15mg PO BID starting in AM. Also start diphenhydramine 2mg/kg BID. No food after midnight, NPO after 6 AM.
bulletFirst Day 20:00 Problem #2 Melena-S/O: Feces appeared dark and tarry on walk this afternoon. A: Most likely due to coughing up blood (hemoptysis) and swallowing it. The hemoptysis is indicative of small pulmonary artery rupture. P: Continue to monitor feces.
bulletSecond Day 08:00 Problem #1 Heartworm w/pulmonary hypertension-S/O: T=100.8, P=112, R=pant. Mild coughing. No harsh lung sounds ausculted. Given 15mg prednisone PO, 12.5 mg diphenhydramine PO. A: Stable and comfortable. P: Surgical removal of heartworms today. Induction planned for 10:00.
bulletSecond Day 08:00 Problem #2 Melena-S/O: No sign of blood in feces this morning. A: Has not been coughing much since being hospitalized, which may mean less/no blood being swallowed. P: Problem resolved.
bulletSecond Day 20:00 Problem #1 Heartworm w/pulmonary hypertension-S/O: Still sedate, T=99.7, P=96, R=36. Fisher was anesthetized. A surgical cutdown of the right jugular vein was performed. An Ishihara flexible alligator forceps as used to successfully remove 8 heartworms from the pulmonary arteries (2 male worms and 6 female worms; 6 from the right and 2 from the left). No complications were encountered during surgery and anesthesia and recovery was uneventful. Owner visited and Fisher was still too sedate to go home. Given 15mg prednisone PO. Urinated and defecated normally. No redness, swelling or discharge at incision site. A: Successful recovery of eight worms from the pulmonary arteries. Resting comfortably in run. P: Discharge tomorrow. Prescribe prednisone 15mg PO BID until recheck on 2/10/03.
bulletThird Day 08:00 Problem #1 Heartworm w/pulmonary hypertension-S/O: BARH, T=101.3, P=120, R=pant. Incision looks good. Appetite good-fed 1 cup dry dog food and 1/4 can P/D. Urinated on walk, no feces. A: Recovering well from surgery. Stable and comfortable. P: Discharge at noon today. Recheck and initiate medical heartworm treatment in one week. Send home with prednisone 15mg PO BID.


bulletEchocardiogram: Severe pulmonary hypertension secondary to heartworm disease causing mild, high-velocity tricuspid regurgitation, large dilated pulmonary arteries, septal flattening from elevated right ventricular systolic pressure; diastolic septal flattening due to right heart failure, and a severely enlarged right heart. Heartworms were not seen around the tricuspid valve but were observed in the right pulmonary artery branch.
bulletECG: regular rhythm. Deep S waves present in leads I, II, III, and aVF, indicative of right ventricular hypertrophy.
bulletHeartworm antigen test: weak positive
bulletThoracic radiographs: severely enlarged/dilated pulmonary arteries and pulmonary vasculature. Lung parenchyma does not appear significantly affected.
bulletConclusion: Severe pulmonary hypertension due to class III heartworm infection.
bulletTreatment consisted of a small incision to expose his right jugular vein and subsequent introduction of a flexible alligator forceps into his pulmonary arteries to remove the worms. The procedure was successful and eight worms were removed. Fisher's right jugular vein was ligated and will remain non-functional for life. Fisher recovered uneventfully. He was sent home the next day on prednisone at 15 mg PO BID (0.5mg/kg) for one week.
bulletFisher's CBC showed a regenerative anemia (HCT=31%) and an eosinophilia of 2,992/uL. His chemistry panel revealed a hypoalbuminemia (2.1 gm/dl) and an increased globulin (5.4 gm/dl). Urinalysis showed SG=1.023 and 3+ proteinuria. Generally the most effective treatment for heartworm-induced glomerular disease is eradication of the adult worms.

Mark D. Kittleson, D.V.M., Ph.D. All rights reserved.