Cardiology team saves street dog from deadly heartworm condition

Flyer is a Potcake, a mixed breed of feral dog found in the Caribbean islands.

Flyer, a mixed breed dog, has been rescued twice this year: once from Jamaican streets by a Canadian charity and a second time by a team of veterinarians at Cornell University’s Hospital for Animals (CUHA).

Flyer is a Potcake, the name given to feral Caribbean dogs with cocked ears who were traditionally fed the caked remains of a rice and pea dish. Flyer lived on the streets and in a sanctuary until Allison Shalla, co-president of Eastern Ontario Potcake Rescue, brought him back to Ottawa last February. Not having received any heartworm prophylaxis, Flyer began taking medication when tests on Valentine’s Day indicated heartworm disease.


Two weeks later Flyer became lethargic and produced rusty- colored urine, the telltale sign of caval (pronounced CAVE-uhl) syndrome: heartworms lodged in the vena cava (the vein bringing blood to the heart), right atrium and right ventricle. Tangles of worms ensnare and crush red blood cells, releasing hemoglobin, which discolors the urine.

Heartworms cause one of the most serious parasitic diseases for North American dogs; the disease has also been found in South America, Australia, the Middle East, and parts of Europe and Asia. An infected mosquito bites a dog (or less commonly, a cat) and injects larvae under the skin. Larvae grow for a few weeks, enter a blood vessel, and flow to the pulmonary arteries after traveling through the right side of the heart. Being too large to enter the lung capillaries, they usually remain in place, increasing the likelihood of pulmonary hypertension (high blood pressure in the lungs) and congestive heart failure. A female worm can grow up to a foot long, resembling spaghetti. The shorter male has a corkscrew tail.

Dr. Romain Pariaut, associate professor of cardiology at CUHA, says that caval syndrome is rare in the Northeast. Winter temperatures usually kill mosquitoes, resulting in fewer heartworm cases than in the southern states. In the past 18 months at Cornell, Pariaut has seen only three cases of caval syndrome.

Flyer’s new owner Shalla sought help outside Ontario because, as she explains, “Our vets here, including our emergency clinic, didn’t have the staff available to deal with caval syndrome.” So they arranged for surgery at CUHA. Patients with Flyer’s condition can die within two days if the worms are not extracted.

Dr. Romain Pariaut examines a radiograph with a colleague.

Surgery is risky, Pariaut explains, because dogs with caval syndrome have trouble breathing and are unstable, with poor cardiac output and blood flow. “Basically, they are the worst candidates for anesthesia,” says Pariaut. “Unfortunately many dogs will not make it through the surgery.”

Luckily for Flyer, Pariaut gained experience fishing for heartworms during his seven years at Louisiana State University. Then he returned to Cornell, where he had completed his residency 12 years earlier.


On Sunday, April 2, CUHA’s team of eight (including residents, Drs. Oxford, Giacomazzi, Porter, and Tseng, and student Austin) began a surgery that lasted for several hours. Pariaut made an incision in the jugular vein, then inserted into the cranial vena cava a sheath with a “basket” inside. When opened, the

Cardiology resident Eva Oxford DVM'12 

instrument resembled a wire whisk with several oblong loops at the end. Guided by live fluoroscopic and ultrasonic images, Pariaut’s team went fishing in the heart. They’d wait for about 30 seconds, pull the basket out to see how many they caught, then go back in. Breaking even one worm could have caused Flyer to go into shock and possibly die.

Their total catch? 86 worms.

“It was a good example of teamwork,” says Pariaut, describing how three services—cardiology, anesthesiology, and diagnostic imaging—helped each other.

Two days after the surgery, Flyer returned to Ottawa and continued medical treatment to eliminate worms remaining in the pulmonary arteries. Shalla recently reported, “his only complaint is the crate rest, but he is very patient.” Reducing physical activity during the recovery months decreases the possibility of dead worm fragments causing blockage in the pulmonary arteries.

According to the American Heartworm Society, heartworm infection is on the rise nationally, partly because pet owners skip doses or don’t administer preventive medications. Pariaut says it’s good for the

Flyer recovers from his surgery in his crate.

public to be reminded about heartworm disease. Owners should give preventive medication year-round. If heartworm disease is diagnosed, advises Pariaut, start medical treatment to eliminate the worms as quickly as possible.