Minimally invasive percutaneous epicardial placement of a prototype miniature pacemaker with a leadlet under direct visualization: A feasibility study in an infant porcine model

Percutaneous epicardial pacing in infants using direct visualization: A feasibility animal study

BACKGROUND

Pacemaker implantation in infants and small children is limited to epicardial lead placement via open chest surgery. We propose a minimally invasive solution using a novel percutaneous access kit.

OBJECTIVE

To evaluate the acute safety and feasibility of a novel percutaneous pericardial access tool kit to implant pacemaker leads on the epicardium under direct visualization.

METHODS

A custom sheath with optical fiber lining the inside wall was built to provide intrathoracic illumination. A Veress needle inside the illumination sheath was inserted through a skin nick just to the left of the xiphoid process and angled toward the thorax. A needle containing a fiberscope within the lumen was inserted through the sheath and used to access the pericardium under direct visualization. A custom dilator and peel-away sheath with pre-tunneled fiberscope was passed over a guidewire into the pericardial space via modified Seldinger technique. A side-biting multipolar pacemaker lead was inserted through the sheath and affixed against the epicardium.

RESULTS

Six piglets (weight 3.7-4.0 kg) had successful lead implantation. The pericardial space could be visualized and entered in all animals. Median time from skin nick to sheath access of the pericardium was 9.5 (interquartile range [IQR] 8-11) min. Median total procedure time was 16 (IQR 14-19) min. Median R wave sensing was 5.4 (IQR 4.0-7.3) mV. Median capture threshold was 2.1 (IQR 1.7-2.4) V at 0.4 ms and 1.3 (IQR 1.2-2.0) V at 1.0 ms. There were no complications.

CONCLUSION

Percutaneous epicardial lead implantation under direct visualization was successful in six piglets of neonatal size and weight with clinically acceptable acute pacing parameters.

A novel videoscope and tool kit for percutaneous pericardial access under direct visualization

BACKGROUND

Pericardial access is necessary for the application of epicardial cardiac therapies including ablation catheters, pacing and defibrillation leads, and left atrial appendage closure systems. Pericardial access under fluoroscopic guidance is difficult in patients without pericardial effusions and may result in coronary artery damage, ventricular injury, or perforation with potentially life-threatening pericardial bleeding in up to 10% of cases. There is a clinical need for a pericardial access technique to safely deliver epicardial cardiac therapies.

METHODS

In this paper, we describe the design and evaluation of a novel videoscope and tool kit to percutaneously access the pericardial space under direct visualization. Imaging is performed by a micro-CMOS camera with an automatic gain adjustment software to prevent image saturation. Imaging quality is quantified using known optical targets, while tool performance is evaluated in pediatric insufflation and pericardial access simulators. Device safety and efficacy is demonstrated by infant porcine preclinical studies (N = 6).

RESULTS

The videoscope has a resolution of 400 × 400 pixels, imaging rate of 30 frames per second, and fits within the lumen of a 14G needle. The tool can resolve features smaller than 39.4 µm, achieves a magnification of 24x, and has a maximum of 3.5% distortion within the field of view. Successful pericardial access was achieved in pediatric simulators and acute in vivo animal studies. During in vivo testing, it took the electrophysiologist an average of 66.83 ± 32.86 s to insert the pericardial access tool into the thoracic space and visualize the heart. After visualizing the heart, it took an average of 136.67 ± 80.63 s to access the pericardial space under direct visualization. The total time to pericardial access measured from needle insertion was 6.7 × quicker than pericardial access using alternative direct visualization techniques. There was no incidence of ventricular perforation.

CONCLUSIONS

Percutaneous pericardial access under direct visualization is a promising technique to access the pericardial space without complications in simulated and in vivo animal models.

Design and Functionality of a Multilumen Thoracic Access Port for Pericardial Access Under Direct Visualization

Small vasculature, venous obstruction, or congenital anomalies can preclude transvenous access to the heart, often resulting in open chest surgery to implant cardiac therapy leads for pacing, defibrillation, or cardiac resynchronization. A minimally invasive approach under direct visualization could reduce tissue damage, minimize pain, shorten recovery time, and obviate the need for fluoroscopy. Therefore, PeriPath was designed as a single-use, low-cost pericardial access tool based on clinical requirements. Its mechanical design aids in safe placement of conductive leads to the pericardium using a modified Seldinger technique. The crossed working channels provide an optimal view of the surgical field under direct visualization. Finite element analysis (FEA) confirms that the device is likely not to fail under clinical working conditions. Mechanical testing demonstrates that the tensile strength of its components is sufficient for use, with minimal risk of fracture. The PeriPath procedure is also compatible with common lead implantation tools and can be readily adopted by interventional cardiologists and electrophysiologists, allowing for widespread implementation. Prior animal work and a physician preliminary validation study suggest that PeriPath functions effectively for minimally invasive lead implantation procedures.

Epicardial implantation of a leadless pacemaker in a lamb model

BACKGROUND

Pacemaker used in small children typically consist of an abdominally placed generator and epicardially affixed leads, making such a system prone to lead dysfunction during growth. Aim of this study was to investigate the feasibility of epicardial pacing with a leadless pacemaker in a lamb model.

ANIMALS AND METHODS

Seventeen lambs underwent epicardial implantation of a Micra transcatheter pacing system (TPS) (Medtronic, Minneapolis, MN, USA) via left-lateral thoracotomy to the left ventricle (LV) surface (n = 11/17) and to the left atrial appendage (n = 6). Ventricular devices were fixated with the tines within the pericardium, whereas the tines of the atrial devices penetrated the myocardium of the left atrial appendage. After 31 weeks, animals were sacrificed and hearts were explanted for histological analysis.

RESULTS

Following implantation, median P/R amplitude was 4.25/5.5 mV while median pacing threshold was 1.1/1.9 V at 0.24 ms. After 31 weeks, median P/R amplitude was 3.3/4.2 mV. Median atrial pacing threshold was 0.5/0.24 ms. Eight of 10 ventricular pacemakers had lost capture at standard impulse width even at maximum impulse amplitude. On explantation, firm adhesion of the device to the thoracic wall and dislodgement of the electrode tip was found in those ventricular devices.

CONCLUSIONS

Firm fixation of the Micra electrode to the epicardial surface as applied to the atrial devices resulted in excellent electrical properties during midterm follow up. Pericardial fixation as in the ventricular devices was associated with loss of capture. Therefore, it is important to embed the tines in the myocardium and to choose an alternative implantation site allowing for safe fixation of the Micra TPS in a position perpendicular to ventricular epimyocardium.

Surgical pericardial adhesions do not preclude minimally invasive epicardial pacemaker lead placement in an infant porcine model

BACKGROUND

Pericardial adhesions in infants and small children following cardiac surgery can impede access to the epicardium. We previously described minimally invasive epicardial lead placement under direct visualization in an infant porcine model using a single subxiphoid incision. The objective of this study was to assess the acute feasibility of this approach in the presence of postoperative pericardial adhesions.

METHODS

Adhesion group piglets underwent left thoracotomy with pericardiotomy followed by a recovery period to develop pericardial adhesions. Control group piglets did not undergo surgery. Both groups underwent minimally invasive epicardial lead placement using a 2-channel access port (PeriPath) inserted through a 1 cm subxiphoid incision. Under direct thoracoscopic visualization, pericardial access was obtained with a 7-French sheath, and a pacing lead was affixed against the ventricular epicardium. Sensed R-wave amplitudes, lead impedances and capture thresholds were measured.

RESULTS

Eight piglets underwent successful pericardiectomy and developed adhesions after a median recovery time of 45 days. Epicardial lead placement was successful in adhesion (9.5 ± 2.7 kg, n = 8) and control (5.6 ± 1.5 kg, n = 7) piglets. There were no acute complications. There were no significant differences in capture thresholds or sensing between groups. Procedure times in the adhesion group were longer than in controls, and while lead impedances were significantly higher in the adhesion group, all were within normal range.

CONCLUSIONS

Pericardial adhesions do not preclude minimally invasive placement of epicardial leads in an infant porcine model. This minimally invasive approach could potentially be applied to pediatric patients with prior cardiac surgery.

Percutaneous epicardial placement of a prototype miniature pacemaker under direct visualization: An infant porcine chronic survival study

INTRODUCTION

Pacemaker implantation in infants typically consists of surgical epicardial lead placement with an abdominal generator. Here, we describe the chronic performance of our minimally invasive prototype miniature pacemaker implanted under direct visualization in an immature porcine model.

METHODS

Twelve piglets underwent miniature pacemaker implantation. A self-anchoring two-channel access port was inserted into a 1 cm incision in the subxiphoid space, and a thoracoscope was inserted into the main channel to visualize the thoracic cavity under insufflation. The pacemaker leadlet was inserted through a sheath via secondary channel and affixed against the epicardium using a helical side-biting electrode. The miniature pacemaker was tucked into the incision, which was sutured closed. Ventricular sensing, leadlet impedance, and capture thresholds were measured biweekly. A limited necropsy was performed after euthanasia.

RESULTS

Nine piglets were followed for a median of 78 (IQR 52-82) days and gained 6.6 ± 3.2 kg. Three animals were censored from the analysis due to complications unrelated to the procedure. Capture thresholds rose above maximal output after a median of 67 (IQR 40-69) days. At termination, there was a significant decrease in R-wave amplitude (P = .03) and rise in capture thresholds at 0.4 ms (P = .01) and 1.0 ms pulse widths (P = .02). There was no significant change in leadlet impedance (P = .74). There were no wound infections.

CONCLUSIONS

There were no infections following minimally invasive implantation of our prototype miniature pacemaker. Improvements to epicardial fixation are necessary to address diminished leadlet efficacy over time.

Chronic performance of subxiphoid minimally invasive pericardial Model 20066 pacemaker lead insertion in an infant animal model

PURPOSE

To describe chronic performance of subxiphoid minimally invasive pacemaker lead insertion in a piglet model.

METHODS

Minimally invasive pacemaker lead implantation was performed through a 10-mm incision under direct visualization using the PeriPath port. Epicardial access was obtained and the commercially available Medtronic Model 20066 pacemaker lead was inserted into the pericardial space and epicardial fixation was performed using the side-action helix. The lead was connected to a pacemaker generator in a para-rectus pocket. Animals underwent a 12-14-week observation period and lead impedances, R-wave amplitudes, and ventricular capture thresholds were tested biweekly. After the survival period, animals were euthanized and gross and histopathology were performed.

RESULTS

Subxiphoid minimally invasive pacemaker lead placement was performed in 8 animals (median 4.9 kg) with 100% acute success. Median procedure time was 65 min (IQR 60.5-77). At implant, median lead impedance was 650 Ω (IQR 244-984), R-wave amplitude 11.1 mV (IQR 8-12.3), and ventricular capture threshold 1.5 V @ 0.4 ms (IQR 1-2.6). Over a median survival period of 13 weeks, there was a median lead impedance change of + 262 Ω (IQR 5.3-618.3), R-wave change of - 4.5 mV (IQR - 7.1-- 2.7) and capture threshold change (1.0 ms) of + 1.5 V (IQR 0-3.3). At autopsy, epicardial fixation sites showed fibrovascular proliferation and minimal chronic inflammation.

CONCLUSIONS

Subxiphoid pericardial pacemaker placement is safe and effective in a piglet model. Further study and development of leads designed for pericardial placement are warranted.