Feasibility and efficacy of percutaneously delivered leadless cardiac pacing in an in vivo ovine model.

INTRODUCTION: In this in vivo ovine study, we describe the course of pacing and sensing parameters during follow-up as well as the gross and histopathological features at the implant site of the recently described leadless cardiac pacemaker (LCP). METHODS AND RESULTS: All sheep underwent LCP implantation in the right ventricular (RV) apex. Serial pacing/sensing thresholds were assessed. In the first cohort, 11 animals were followed up for a period of 3 months, followed by necropsy. In the second cohort, 7 additional sheep were followed for a period of up to 18 months. Mean pacing and sensing thresholds in the 3-month cohort were 1.0 ± 0.5 V and 9.0 ± 3.7 mV at implant, and 0.7 ± 0.2 V and 8.1 ± 3.9 mV at 90 days, respectively. At necropsy at 3 months, all devices were securely implanted at the RV apex without extrusion of helix beyond the RV wall. Besides endocardial reactive changes in the RV apex surrounding the distal portion of the LCP, there were no other grossly visible abnormalities. In the second cohort (7 sheep), mean pacing and sensing thresholds were 1.0 ± 0.5 V and 9.9 ± 3.8 mV at implant, and 0.86 ± 0.4 V and 4.25 ± 1 mV, respectively, at 18 months of follow-up. CONCLUSION: We demonstrate that after implantation of the LCP, pacing/sensing parameters remain adequate up to 18 months in follow-up. In addition, pathological changes at the implant site and within the RV are limited in severity at 90 days, supporting the efficacy and safety of this novel approach to pacing.

Percutaneous Retrieval of Implanted Leadless Pacemakers: Feasibility at 2.5 Years Post-Implantation in an In Vivo Ovine Model.

OBJECTIVES: This in vivo ovine study describes the feasibility and safety of retrieving implanted leadless pacemakers (LPs). BACKGROUND: Although LPs have been shown to be removable soon after implantation, there are no data on the feasibility of removing chronically implanted LPs. METHODS: This study was performed in 2 phases. In the mid-term cohort, 10 chronically (5.3 months) implanted animals underwent retrieval, followed by: 1) immediate necropsy in 5; and 2) in the remaining 5, reimplantation of a new LP followed by necropsy at 6 weeks. In the long-term cohort, 8 additional sheep underwent retrieval at 2.3 ± 0.1 years followed by necropsy. Retrieval was performed using either a single or triple loop snare. All 18 LPs (100%) were successfully retrieved. The time from retrieval catheter insertion to retrieval was 2:35 ± 01:11 and 3:04 ± 01:13 minutes in the mid-term and long-term study groups, respectively. RESULTS: There were no significant differences in retrieval times using either snare. Intracardiac echocardiography was used pre- and post-retrieval to confirm the absence of pericardial effusion in all 8 sheep. On necropsy, there was no evidence of pericardial bleeding or perforation. Only minor tissue disruption and hemorrhage was noted at the implant site after retrieval. Histology demonstrated fibrous connective tissue at the contact sites of endocardium and LP can and at the helix. There was no evidence of pulmonary thromboembolism. CONCLUSIONS: We demonstrate the feasibility and safety of percutaneous, catheter-based retrieval in chronic LP implants of a maximum duration of approximately 2.5 years.

Novel mitral repair device for the treatment of severe mitral regurgitation: preclinical ovine acute and chronic implantation model.

OBJECTIVE: A project is now underway to implement a novel percutaneous mitral repair system for severe mitral regurgitation (MR). The initial phase of the project consists of proof-of-concept by testing device characteristics using open surgical implantation. When surgical proof-of-concept of the intended percutaneous design is completed, a second phase of the project will consist of in vivo testing of the percutaneous transseptal system. The device is currently being designed to fold into a 17F catheter system and to unfold within the left atrium where attachment is accomplished using a reversible anchoring system. The purpose of this study was to show functionality of the device in elimination of MR using the open surgical method. METHODS: We have performed surgical prototype device implantation in 5 acute and 7 chronic sheep preparations. We created a P2-flail model of severe (4+) MR in the 12 sheep. Via a minimally invasive left thoracotomy incision and open repair on cardiopulmonary bypass, the device was implanted to determine efficacy of elimination of severe MR. Implantation was considered successful if 4+ regurgitation was converted to 1+ MR or lower. Left ventriculography and epicardial 2-dimensional/3-dimensional echocardiography were used to assess repair; serial 2-dimensional/3-dimensional transthoracic echocardiography was used to assess long-term mitral repair status. RESULTS: Twelve sheep had surgical creation of severe (4+) MR by cutting all chordae to the P2 scallop of the mitral valve; this preparation was tested and was found to produce 100% acute fatality without repair of the mitral valve. Five sheep had acute implantation of the device with elimination of regurgitation in 5/5 sheep. Seven sheep had chronic (1-7 month) implantation of the device. The device was tested in the chronic model for clinical status, residual regurgitation, thrombosis, and histopathology. All sheep had mitigation of MR and survived to the intended date of death. CONCLUSIONS: Proof-of-concept of a novel percutaneous mitral repair device has been completed using an ovine P2-flail severe MR model. The device has characteristics that will allow its use in posterior leaflet degenerative disease and functional/secondary MR. Open, minimally invasive, and robotic surgical implantation of the device can also be developed as an alternative to the percutaneous approach.