New study will explore advanced pacemaker techniques in canine heart patients

A University of Florida study aimed at discovering better ways to place pacemakers in dogs with complete heart block has received a $100,000 boost through a grant from the Morris Animal Foundation. The study, under way at UF's Veterinary Medical Center, already has six dogs enrolled.

Complete heart block occurs when normal rhythms between cells within the heart are blocked so that normal impulses are not delivered. Other cells overcompensate to ''rescue'' the heart and keep it beating, but work ineffectively, leading to clinical signs of fatigue, exercise intolerance and even congestive heart failure.

''In traditional treatment, one lead is placed within the right-sided ventricle to electrically control the heart rhythm,'' said Amara Estrada, D.V.M., an assistant professor of veterinary cardiology at UF's VMC. ''Occasionally, an additional lead will also be placed within the right atrium as well. Looking back over the last 20 years of pacing therapy, we now realize that this approach is less than ideal and in fact can lead to worsening heart disease in about 10 percent of the dogs and people treated in this way.''

The new study will focus on the relative effectiveness of placing pacemakers within the right and the left ventricles as well as from both ventricles simultaneously.

''We're trying to get as close to natural cardiac physiology as possible,'' Estrada said. ''Pacing equipment has gotten so advanced that we can get very close to imitating what happens normally in the heart.''

Estrada said UF's study will be ''slightly ahead'' of what's currently being performed clinically in human cardiology to treat complete block in people and will hopefully provide information that will be crucial not just for veterinary patients but also for human patients requiring pacing therapy.

''The actual surgical procedure is no different than what we're doing now,'' Estrada said. ''We're just placing more leads.''

The UF veterinary cardiology team has already flown out to Minneapolis-based Medtronic, a company that manufactures pacemakers, to learn the new techniques for pacing. In addition, UF veterinarians have visited Cornell University to teach veterinary cardiologists there the clinical technique, and plan to demonstrate the technique to Texas A&M University veterinary colleagues in the future as well.

''We hope to include 36 dogs in the study and will evaluate them both in the short term and in the long term for any potential clinical benefits of this new pacing technique,'' Estrada said.

Symptoms of complete, or third degree, heart block include exercise intolerance, collapse episodes, abdominal swelling and coughing. The VMC's cardiology service sees one or two cases of dogs with complete heart block every month, Estrada said, adding that letters are being sent to referring veterinarians in an effort to recruit additional study candidates.

The study will cover all costs to patients associated with the procedure, and follow-up care during the three-year study period. Study candidates will be screened and if they qualify, treatment includes a two-day hospital stay and rechecks.

For more information about the study, contact the cardiology service through the VMC's main number, 352-392-4700, ext. 4700. Referring veterinarians should contact Megan Van Rysdam at ext. 4875 for an appointment or ask to speak to any member of the cardiology service for more information.