Minimally Invasive Implantation of a Micropacemaker Into the Pericardial Space

Abstract

Background: Permanent cardiac pacemakers require invasive procedures with complications often related to long pacemaker leads. We are developing a percutaneous pacemaker for implantation of an entire pacing system into the pericardial space.

Methods: Percutaneous micropacemaker implantations were performed in 6 pigs (27.4-34.1 kg) using subxyphoid access to the pericardial space. Modifications in the implantation methods and hardware were made after each experiment as the insertion method was optimized. In the first 5 animals, nonfunctional pacemaker devices were studied. In the final animal, a functional pacemaker was implanted.

Results: Successful placement of the entire nonfunctional pacing system into the pericardial space was demonstrated in 2 of the first 5 animals, and successful implantation and capture was achieved using a functional system in the last animal. A sheath was developed that allows retractable features to secure positioning within the pericardial space. In addition, a miniaturized camera with fiberoptic illumination allowed visualization of the implantation site before electrode insertion into myocardium. All animals studied during follow-up survived without symptoms after the initial postoperative period.

Conclusions: A novel micropacemaker system allows cardiac pacing without entering the vascular space or surgical exposure of the heart. This pericardial pacemaker system may be an option for a large number of patients currently requiring transvenous pacemakers but is particularly relevant for patients with restricted vascular access, young children, or those with congenital heart disease who require epicardial access.

Keywords: adult; cardiac pacing, artificial; child; heart block; models, animal.

Figure 1

Epicardial micropacemaker system. A. During implantation, the sheath is held inside the pericardial membrane by the extended wire loops while the corkscrew iridium electrode (far right) is screwed into the myocardium by rotating the plastic sleeve that grips its disc-shaped base. B. The micropacemaker and its coil-spring flexible lead are deployed by pushing it out of the sleeve and into the pericardial space, followed by retracting the loops of the sheath and removing it with the sleeve and pushrod. The micropacemaker includes an epoxy-encapsulated, relaxation-oscillator circuit that generates fixed-rate pulses, a lithium ion cell and an inductive coil that captures energy from an extracorporeal RF electromagnetic field (6.78 MHz) to recharge the cell as required.

Figure 2

Fluoroscopic view (lateral) of dummy micropacemaker system just after implantation. The securable sheath is seen with loops extended. The miniature fiberoptic camera was advanced through the sheath to view the device after placement.

Figure 3

Fluoroscopic view (anterior-posterior) of micropacemaker system just after implantation.

Figure 4

View at necropsy of dummy micropacemaker device with electrode implanted into epicardial surface.

Figure 5

Myocardium at site of implantation from pig #6 demonstrating the path of the electrode (seen as round / elliptical voids). The histology demonstrates histiocytes, fibrosis and chronic inflammatory changes consistent with a foreign body reaction.