UC Davis veterinarians remove heartworm from cat's femoral artery


The cat, which had history of heartworm disease, presented with rear leg lameness.

Image courtesy of UC Davis.

Stormie, a 4-year-old female Siamese cat with a history of heartworm disease since being adopted at 1 year of age, recently underwent a novel procedure to remove a heartworm from her femoral artery at the University of California, Davis, according to a university release.

Stormie and her owner live in Los Angeles but were visiting family in the the Bay Area when one of Stormie's rear legs became lame. Fearing an injury, the owner took Stormie to a veterinary emergency practice in Berkeley and informed the veterinarian of her heartworm history. After an ultrasonographic examination showed a suspected heartworm in the arterial system and a strong positive result was found on a heartworm antigen test, the veterinarian advised the client to take Stormie to the specialists at UC Davis, the release states.

The cardiology service at UC Davis confirmed the referring veterinarian's diagnosis and performed an echocardiographic examination to determine the exact location of the worm and form a treatment plan. The test showed a heartworm in the pulmonary artery, and the veterinarians also saw evidence of pulmonary hypertension associated with heartworm disease.

An abdominal ultrasound confirmed that the heartworm extended into Stormie's abdominal aorta and down her leg into the right femoral artery. The worm was cutting off the blood supply to the right leg and needed to be addressed promptly to avoid amputation.

Next, the anesthesia/critical care and diagnostic imaging teams anesthetized Stormie to perform a computed tomography (CT) angiography scan. While the scan didn't reveal any additional heartworms, it did show abnormalities in the soft tissues of Stormie's right rear leg, likely secondary to the decreased blood flow caused by the worm. It also showed evidence of inflammation in the lungs likely caused by the heartworms, the release notes.

Catherine Gunther-Harrington, DVM, DACVIM (cardiology), and Ingrid Balsa, MEd, DVM, of the soft tissue surgery service, assisted by cardiology resident Maureen Oldach, DVM, collaborated to remove the 13-cm heartworm from Stormie's right femoral artery without breaking it, the release states. After the worm was removed there was normal blood flow through the artery and the leg tissue still looked healthy, so the doctors repaired the artery and decided that amputation was not necessary at that time. However, the release notes, amputation of the leg may be required in the future if the nerves and muscle don't heal properly, which could take months.

This process of removing a heartworm via the femoral artery has been reported on just a few occasions in dogs, but never in cats, the release states. Because of this, Dr. Oldach is writing up the case for submission to a scientific journal.

Stormie stayed in the intensive care unit at UC Davis for four days so the team could monitor her recovery. In addition to pain and anti-inflammatory medication, she was given an antibiotic to help weaken any remaining heartworms in her system. As the worms die they will break into small pieces that could lodge in the lungs or elsewhere in the circulatory system. To prevent this doctors prescribed a medication to help break up blood clots and prevent new clots from forming. Stormie has also been placed on a monthly heartworm preventive that she will continue for the rest of her life, the release states.

Stormie is also going through physical rehabilitation to strengthen her leg, and her owner is hopeful that she will continue to improve.

UC Davis has published a video of the heartworm removal here.

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