A Little Dog With A Lot Of Heart: Texas A&M Veterinarians Help Chihuahua Overcome Life-Threatening Heartworm Complication

Story by Megan Bennett, VMBS Marketing & Communications

June 26, 2025

An 8-pound Chihuahua named Petey McPherson holds a new record at the Texas A&M Small Animal Teaching Hospital (SATH) after having 58 heartworms surgically removed from his tiny heart.

This overwhelming number of heartworms would have been fatal for Petey if his loving owner, Don McPherson, had not rescued him as a stray and ensured he received veterinary care. 

Petey’s road to recovery was rough, but thanks to care from his primary veterinarian and a team of veterinary cardiologists at Texas A&M, he has proven that even the smallest of dogs can achieve great victories.

A Difficult Beginning

McPherson, who lives in Bullard, Texas, has always had a heart for saving animals. 

“I was born into a family that loved animals of all kinds,” he said. “I’m happy to help when I can. If not me, then who?”

So, when he came across a photo of a tiny stray dog in the nearby town of Troup, he didn’t hesitate before coming to its rescue.

“He was so emaciated and just looked pitiful,” McPherson said. “I had a feeling that he was going to have some medical problems since he had been out on the streets, but I didn’t want him to end up at an animal shelter.”

McPherson drove Petey straight from Troup to his primary veterinarian, Dr. Roy Wilmeth ’14 of Kingdom Veterinary Clinic in Flint. 

“He was heartworm-positive, had horrible hookworms and some other worms, and was anemic,” McPherson said. “I just told them to start treating.”

Wilmeth treated Petey’s hookworms, began treating the heartworms, and improved his iron levels enough that he could be neutered. But not long after surgery, blood in his urine indicated a bigger problem.

Wilmeth performed an echocardiogram and saw a “massive cluster of heartworms” in the right side of Petey’s heart, indicating a life-threating heartworm complication known as caval syndrome. 

Recognizing the urgency of the condition, he recommended that McPherson take Petey to Texas A&M for surgery, the only chance at saving the dog’s life. McPherson made the two-and-a-half-hour drive to College Station that same night.

A Whole Can Of Worms

Caval syndrome is the final and worst stage of heartworm disease in dogs. 

“Heartworms usually live in the pulmonary arteries (which carry blood from the heart to the lungs), but if there are enough, they sometimes start backing up into the heart and cause obstruction to blood flow,” said Dr. Sukjung Lim, a first-year veterinary resident at the SATH. “The worms also damage red blood cells, which can cause discolored urine and anemia.”

Caval syndrome is nearly always fatal if not treated with heartworm removal surgery, a minimally invasive but complex procedure only available at select veterinary hospitals with board-certified cardiologists like Dr. Sonya Wesselowski, an associate professor at the Texas A&M College of Veterinary Medicine & Biomedical Sciences.

Wesselowski and Lim, alongside the rest of the cardiology and anesthesia teams, prepared Petey for surgery the morning after his arrival. They anticipated no more than roughly ten or fifteen heartworms inside the tiny dog. Once they began the procedure, however, they were shocked by how many they had to remove. 

“We went in through the jugular vein, which is the large vein in the neck, and fed tiny equipment down into the right side of the heart so we could grab the worms and pull them out,” Wesselowski said. “We were pulling longer than we expected to because there were just so many worms in Petey. My previous record was 55 worms removed from a Labrador Retriever, so the fact that we got more than that out of this tiny little Chihuahua was really crazy.”

Continuing Care

After an hour and 12 minutes, Wesselowski and Lim had finally removed all of the heartworms from the inside of Petey’s heart. Some worms remained out of reach within the blood vessels of his lungs, however, so Petey is now undergoing the standard multi-month heartworm treatment process.

This includes a course of antibiotics, two months of heartworm prevention to kill larvae, and a series of three injections to kill adult heartworms. During this time, he’ll need to be on crate-rest to avoid developing any other complications.

“Dogs with heartworm disease are always at risk of having blood clots or fragments of worms dislodge and suddenly block an artery in the lungs, causing a pulmonary thromboembolism (PTE),” Wesselowski said. “Strenuous activity and exercise increase the risk of PTEs, and the highest risk is around the time they get their adulticide injections.”

As a consequence of the heartworms, Petey may have mild pulmonary hypertension — high blood pressure in the lungs — for the rest of his life.

“Heartworms live in the arteries inside the lungs, causing irritation and inflammation,” Wesselowski said. “That can damage the blood vessels and make them get stiffer over time, which causes high blood pressure.”

Fortunately, Petey’s hypertension is mild enough that it most likely won’t ever impact his quality of life or require medication for treatment.

A Lasting Legacy

During his time at Texas A&M, Petey played an important role in helping teach fourth-year veterinary students about the symptoms and dangers of heartworms. 

“It was such a wonderful teaching case for our students because the heart murmur you hear with caval syndrome is very distinct,” Wesselowski said. “All the veterinary students on the rotation got to hear that murmur and see his case through from start to finish. He taught them a lot about heartworm disease.”

Petey’s story will also be used to remind dog, cat, and ferret owners about the importance of heartworm prevention.

“Heartworms are so easy to prevent,” Lim said. “You just need to give a pill once a month, and it’s really not expensive, especially compared to surgery or heartworm treatment.”

Heartworm preventatives are also available as topical and injectable medications, and some even include additional protection against intestinal worms, fleas, and ticks.

Petey’s case also will help educate pet owners by allowing them to visualize the impact of heartworms — all 58 will be preserved in a jar at Wilmeth’s clinic.

“Petey may be the luckiest dog I have ever met,” Wilmeth said. “He is such a sweetheart and one of our clinic favorites. He could not have found a better home; Mr. McPherson has always gone above and beyond for his animals, and it is a privilege to be his veterinarian. I am so thankful for the doctors at Texas A&M who were able to help save Petey’s life.”

A Bright Future

McPherson is looking forward to seeing Petey’s true personality continue to emerge once he finishes heartworm treatment. 

“He’s close to being as smart as my Jack Russell,” McPherson said. “You can watch his brain work and see him figure things out. I can’t wait to see him totally done with the heartworm treatment because he’s got so much energy.”

McPherson is also excited to see Petey play with his other dogs, who have quickly become his new best friends. 

Despite his challenging past, Texas A&M veterinarians agree that Petey has a bright future just around the corner.

“Petey just hit the jackpot on finding an owner who was willing to go the distance with him,” Wesselowski said. “It’s a big commitment to take on any dog, let alone a dog that comes with health problems. Petey’s owner was willing to see him through everything, including his big surgery and heartworm treatment. Petey’s going to have a great outlook on life, and not everybody would have given him that chance.”

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For more information about the Texas A&M College of Veterinary Medicine & Biomedical Sciences, please visit our website at vetmed.tamu.edu or join us on Facebook, Instagram, and X.

Contact Information: Jennifer Gauntt, Director of VMBS Communications, Texas A&M College of Veterinary Medicine & Biomedical Sciences, jgauntt@cvm.tamu.edu, 979-862-4216

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