May
18
2005

Placing pacemakers, a common practice for veterinary cardiologists, may soon entail the placement of dual chamber pacemakers with biventricular leads compared with the current practice of placing one lead in the right ventricle, said Amara Estrada, DVM, DACVIM, assistant professor at the University of Florida. Estrada is in charge of a new study that tests the procedure on client dogs. The process of placing more than one pacemaker lead will add about a half hour to the surgical procedure. It is expected to produce a more normal heartbeat in dogs and reduce the chance of congestive heart failure, which can occur in about 2 percent of patients, Estrada said. A similar study in people is starting in Italy.

Carroll Loyer, DVM, DACVIM in cardiology, places an average of six pacemakers annually at the Veterinary Referral Center in Colorado and is intrigued by the study. He has placed two leads in about four dogs, one in the right atria and another in the right ventricle, to regain the 15 to 20 percent heart output that can be lost if the heartbeat isnt synchronized, he said. He also uses variable rate pacemakers, which range from 60 heartbeats per minute when dogs are asleep to 140 beats per minute when they are active. Referring to the University of Florida study, Carroll said, "It sounds pretty advanced, and it would technically be more difficult to pace the left ventricle, which is why nobody does it. My question is would the difficulty be worth the difficulty?"

Estrada has successfully performed the operation, which would normally cost $2,000, on one client dog and hopes to enroll 36 dogs with complete heart block in the study. Four follow-up visits are required. Dogs will be rechecked until 18 months post-pacemaker implantation, which would normally cost about $500 in addition to surgery fees, she said. Estrada hopes to obtain grants to pay for all client expenses. For the first client dog, Estradas team made a small incision over the jugular vein, isolated and nicked the vein and while watching on fluoroscopy, placed leads into the beating heart in the right atrium and left ventricle through the coronary sinus.

Heart failure affects dogs of all breeds and ages, Estrada said. Depending on funding and enrollment in the study, she hopes to present preliminary findings at the ACVIM meeting in 2006. Long-term follow-up data will take about two to three years to compile.

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