Case Studies In Small Animal
Artificial Pacemaker Implantation
Following the placement of the temporary pacemaker, we anesthetized Houdi and a permanent artificial pacemaker was implanted using a transvenous approach via the jugular vein. All of our pacemaker generators and leads are donated to us by Medtronics, a pacemaker company in Minnesota. They donate generators that have gone off "shelf-life" which means they have set on the shelf too long to be placed in a U.S. citizen (FDA rules). The company then has the option of selling them to physicians in countries where the rules aren't quite so stringent or donating them, some of them to veterinarians. Because they are donated, we cannot guarantee how long the battery will last but most of the generators we receive are relatively new models and most generators outlive the patient. Also because they are donated to us, we can generally implant a pacemaker for around $2500.
The pacemaker lead was placed into Houdi in much the same way as shown in the diagram of lead placement in a human above. The major difference is that Houdi's lead was placed through the jugular vein.
The figures below were taken from videotape of the fluoroscopy taken during the procedure.
The ventral lead is the temporary pacing lead. Its tip is sitting in the apex of the right ventricular chamber. The dorsal lead is the permanent lead that is being advanced. It has been advanced into the caudal vena cava. Consequently, it must be retracted and the metal stylus that is placed down the center of the lead must be bent so that the end of the lead has a curve that can be advanced toward the tricuspid valve.
The lead has been withdrawn and advanced again toward the tricuspid valve. The tip is lodged against the tricuspid valve and is bending as force is applied.
The permanent lead has now crossed the tricuspid valve and the tip is lying in the apex of the right ventricular chamber along with the temporary lead.
The lead is now in a good position. The tip is angled caudally and there is enough force on the lead to keep it slightly bent so the tip is forced up against the myocardium. The tip has plastic tines that entwine in the trabeculae of the right ventricular wall. The position plus the force plus the tines should keep this lead in place and in this case it did. Leads most commonly dislodge when they do not have tines or are not actively fixed in the myocardium and when they are improperly positioned. The temporary lead has been withdrawn since the permanent lead can now be attached to the generator.
This picture from another dog shows the pacemaker generator attached to the lead. The lead has been tunneled subcutaneously from the neck (jugular vein) back to the lateral thorax. A skin incision has been made and a pocket created beneath the cutaneous trunci muscle to hold the generator.
©Mark D. Kittleson, D.V.M., Ph.D. All rights reserved.