Minimally invasive resynchronization pacemaker: a pediatric animal model

A leadless pericardial pacemaker

BACKGROUND

Cardiac pacemakers have complications related to long pacemaker leads, subcutaneous pockets, and endovascular hardware.

OBJECTIVE

We report on the development of a leadless micropacemaker for percutaneous implantation into the pericardial space.

METHODS

Percutaneous implantations of a micropacemaker system were performed in 15 pigs through subxiphoid access to the pericardial space. In our concept phase, 10 implants were performed with iterative changes to the design and implantation techniques until a design was reached for a viable device. In the study phase, a viable device was implanted in 5 pigs and observed during 8 weeks.

RESULTS

At the completion of the concept phase, a prototype micropacemaker device was fabricated that met 3 mandatory system requirements: can be safely and reproducibly implanted percutaneously into the pericardial space; does not migrate after implantation; and successfully captures the myocardium at implantation and during long-term follow-up (up to 8 weeks). The prototype device was successfully and safely implanted into all 5 pigs in the study phase. These 5 animals survived to the 8-week end point without complications. Ventricular capture threshold calculations at implantation were a median 0.43 V at 0.4 ms (range, 0.05-0.75 V at 0.4 ms). At 8 weeks of follow-up, median capture thresholds were 2.8 V at 0.4 ms (total range, 2.2-7.1 V).

CONCLUSION

A novel pericardial micropacemaker system allows minimally invasive implantation of a leadless cardiac pacemaker without entering the vascular space. We provide proof of concept of this design with encouraging follow-up data.

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.

Novel Doppler-guided subxyphoid approach to avoid coronary artery damage during left ventricular epicardial lead placement or ablation

BACKGROUND

Subxyphoid active left ventricular epicardial (LVE) lead implants or VT ablation are attractive but remain a challenge due to concerns of coronary artery damage. We aimed to see if Doppler-guided positioning could permit safe LVE lead placement without coronary angiography. We evaluated the feasibility of a Doppler flow-guided subxyphoid epicardial screw-in lead fixation in a swine model.

METHODS

Acute subxyphoid access to the pericardial space was performed in an anesthetized swine model using a deflectable sheath and a modified needle-derived Doppler flow meter. The audio signal and visual display from the Doppler flow meter were recorded. Coronary angiography was performed to verify the catheter location. A SelectSecure Model 3830 lead (Medtronic) was used to assess pacing in the procedure.

RESULTS

In both of two swine, the deflectable catheter was inserted into pericardial space via subxyphoid access. The tip of the deflectable catheter with the Doppler was directed to several locations, from quiet (no nearby coronary artery expected) to typical rhythmic pulsatile sound locations which were maximal when superimposed on a coronary artery. Repeated coronary angiograms confirmed the expected findings. A 3830 active lead was fixed into a quiet location for LVE pacing, and confirmed by angiography as distant from a coronary artery.

CONCLUSIONS

Doppler-guided subxyphoid epicardial screw-in lead placement is feasible once the catheter tip is directed and stabilized in a desired LVE location. This obviates the need for repeated (or any) coronary angiography. The Doppler-guided subxyphoid epicardial procedure may also be applicable for epicardial ventricular arrhythmia ablation procedures.

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.

Optocardiography and Electrophysiology Studies of Ex Vivo Langendorff-perfused Hearts

Small animal models are most commonly used in cardiovascular research due to the availability of genetically modified species and lower cost compared to larger animals. Yet, larger mammals are better suited for translational research questions related to normal cardiac physiology, pathophysiology, and preclinical testing of therapeutic agents. To overcome the technical barriers associated with employing a larger animal model in cardiac research, we describe an approach to measure physiological parameters in an isolated, Langendorff-perfused piglet heart. This approach combines two powerful experimental tools to evaluate the state of the heart: electrophysiology (EP) study and simultaneous optical mapping of transmembrane voltage and intracellular calcium using parameter sensitive dyes (RH237, Rhod2-AM). The described methodologies are well suited for translational studies investigating the cardiac conduction system, alterations in action potential morphology, calcium handling, excitation-contraction coupling and the incidence of cardiac alternans or arrhythmias.

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.

Minimally Invasive Implantation of a Micropacemaker Into the Pericardial Space

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.

Feasibility of an Entirely Extracardiac, Minimally Invasive,Temporary Pacing System

Background:

A completely extracardiac pacing system provides the potential for clinical advantages over existing device alternatives that require intravascular, endocardial, or epicardial contact. Preliminary studies evaluating the feasibility of cardiac pacing with a lead in the anterior mediastinum, outside the pericardium and circulatory system have been completed. These studies examined (1) the anatomic access route, (2) the usability of a delivery tool to facilitate lead placement, and (3) the pacing performance of the extracardiac lead.

Methods:

Feasibility evaluations included (1) a retrospective computed tomography analysis to characterize anatomic variations related to lead access, (2) accessing the anterior mediastinum in cadavers and human subjects using a custom delivery tool, and (3) acute clinical pacing performance.

Results:

Major findings: (1) A total of 166 (95%) out of 174 patients had a viable lead access path through the fourth, fifth, or sixth intercostal space. (2) Access to the targeted implant location using a delivery tool was successful in all 5 cadavers and 3 humans without use of fluoroscopy and with an average lead delivery time of 121±52 s. No damage to the lung, pericardium, heart, or internal thoracic vessels occurred. (3) Pacing performance was tested in 6 human subjects showing a threshold voltage of 4.7 V (2.7–6.7), threshold pulse width of 1.8 ms (1.0–2.5), and an impedance of 1205 Ω (894–1786). R-wave amplitudes measured 9.6 mV (5.6–12.0).

Conclusions:

Results support the feasibility for this completely extracardiac pacing method in a heterogeneous patient population, using a minimally invasive, parasternal, delivery approach and with adequate sensing and thresholds suited for temporary pacing.

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

BACKGROUND

Pacemaker implantation in infants is limited to epicardial lead placement and an abdominal generator pocket. We propose a minimally invasive solution using a prototype miniature pacemaker with a steroid-eluting leadlet that can affix against the epicardium under thoracoscopy.

OBJECTIVE

The purpose of this study was to evaluate the safety and feasibility of acute implantation of a prototype miniature pacemaker in an infant porcine model.

METHODS

A self-anchoring 2-channel access port was inserted into a 1-cm incision left of the subxiphoid space. A rigid thoracoscope with variable viewing angle was inserted through the main channel to visualize the heart under insufflation. An 18-G needle through the second channel accessed the pericardial space, which was secured with a 7-F sheath. The leadlet was affixed against the epicardium using a distal helical side-biting electrode. The sheath, thoracoscope, and port were removed, and the pacemaker was tucked into the incision. Ventricular sensing, lead impedances, and capture thresholds were measured.

RESULTS

Twelve piglets (weight 4.8 ± 1.9 kg) had successful device implantation. The median time from incision to leadlet fixation was 21 minutes (interquartile range [IQR] 18-31 minutes). The median lead impedance was 510 Ω (IQR 495-620 Ω). The median R-wave amplitude was 5.7 mV (IQR 4.2-7.0 mV). The median capture threshold was 1.63 V (IQR 1.32-2.97 V) at 0.4 ms pulse width and 1.50 V (IQR 1.16-2.38 V) at 1.0 ms pulse width. There were no complications.

CONCLUSION

Minimally invasive epicardial placement of a prototype miniature pacemaker under thoracoscopy was safe and avoided open chest surgery and creation of an abdominal generator pocket.

Single-incision percutaneous pericardial ICD lead placement in a piglet model

INTRODUCTION

Our group has demonstrated the feasibility of percutaneous pericardial ICD lead placement in a piglet model utilizing direct visualization from a lateral thoracoscopic approach. Development of a novel delivery tool that incorporates visualization allows for the procedure to be performed with a 1 cm subxiphoid incision.

METHODS AND RESULTS

A 1 cm incision is made in the subxiphoid area and a novel self-anchoring delivery tool is inserted. A rigid thoracoscope and needle are inserted into two crossed working channels of the tool. After needle visualization, pericardial needle access, followed by sheath access is obtained. A modified side-biting ICD lead is inserted and fixated to the ventricular epicardial surface. The lead is connected to an ICD generator and lead testing followed by defibrillation threshold testing (DFT) is performed. Single-incision ICD lead placement was performed in 6 piglets without acute complications. Median time from subxiphoid incision to DFT testing was 64 minutes; median time from thoracoscope insertion to lead fixation was 16.5 minutes (range 9-30). All had adequate ventricular sensing and pacing at implant and underwent successful defibrillation (range 3-5 J). Survival period ranged from 1 to 16 weeks. Two piglets had survival periods of 12 and 16 weeks with mean weight gain of 7 kg; both had successful repeat DFT at 10 J. All survival animals had stable lead impedances and R-wave amplitudes throughout the survival period.

CONCLUSION

Percutaneous pericardial placement of an ICD lead using our novel access tool can be safely performed through a 1 cm incision without complications.

Minimally invasive percutaneous pericardial ICD placement in an infant piglet model: Head-to-head comparison with an open surgical thoracotomy approach

BACKGROUND

Epicardial implantable cardioverter-defibrillator (ICD) placement in infants, children, and patients with complex cardiac anatomy requires an open surgical thoracotomy and is associated with increased pain, longer length of stay, and higher cost.

OBJECTIVE

The purpose of this study was to compare an open surgical epicardial placement approach with percutaneous pericardial placement of an ICD lead system in an infant piglet model.

METHODS

Animals underwent either epicardial placement by direct suture fixation through a left thoracotomy or minimally invasive pericardial placement with thoracoscopic visualization. Initial lead testing and defibrillation threshold testing (DFT) were performed. After the 2-week survival period, repeat lead testing and DFT were performed before euthanasia.

RESULTS

Minimally invasive placement was performed in 8 piglets and open surgical placement in 7 piglets without procedural morbidity or mortality. The mean initial DFT value was 10.5 J (range 3-28 J) in the minimally invasive group and 10.0 J (range 5-35 J) in the open surgical group (P = .90). After the survival period, the mean DFT value was 12.0 J (range 3-20 J) in the minimally invasive group and 12.3 J (range 3-35 J) in the open surgical group (P = .95). All lead and shock impedances, R-wave amplitudes, and ventricular pacing thresholds remained stable throughout the survival period.

CONCLUSION

Compared with open surgical epicardial ICD lead placement, minimally invasive pericardial placement demonstrates an equivalent ability to effectively defibrillate the heart and has demonstrated similar lead stability. With continued technical development and operator experience, the minimally invasive method may provide a viable alternative to epicardial ICD lead placement in infants, children, and adults at risk of sudden cardiac death.

Implant and clinical characteristics for pediatric and congenital heart patients in the national cardiovascular data registry implantable cardioverter defibrillator registry

BACKGROUND

In 2010, the National Cardiovascular Data Registry enhanced pediatric, nonatherosclerotic structural heart disease and congenital heart disease (CHD) data collection. This report characterizes CHD and pediatric patients undergoing implantable cardioverter defibrillator implantation.

METHODS AND RESULTS

In this article, we report implantable cardioverter defibrillator procedures (April 2010 to December 2012) in the registry for 2 cohorts: (1) all patients with CHD (atrial septal defect, ventricular septal defect, tetralogy of Fallot, Ebstein anomaly, transposition of the great vessels, and common ventricle) and (2) patients <21 years. We evaluated indications and characteristics to include transvenous and nontransvenous lead implants, CHD type, and New York Heart Association class. There were 3139 CHD procedures, 1601 for patients <21 years and 126 for CHD <21 years. Implantable cardioverter defibrillator indications for patients with CHD were primary prevention in 1943 (61.9%) and secondary prevention in 1107 (35.2%). Pediatric patients had 935 (58.4%) primary prevention and 588 (36.7%) secondary prevention devices. Primary prevention had higher New York Heart Association class. Nontransvenous age (35.9 ± 23.2 versus 40.1 ± 24.6 years; P=0.05) and nontransvenous height (167.1 ± 18.9 cm; range, 53-193 cm versus 170.4 ± 13.1 cm; range, 61-203 cm; P<0.01) were lower than for transvenous patients. CHD and pediatrics had similar rates of transvenous (97%) and nontransvenous (3%) leads and did not differ from the overall registry. Transposition of the great vessels and common ventricle had higher rates of nontransvenous leads.

CONCLUSIONS

Primary prevention exceeds secondary prevention for CHD and pediatrics. Nontransvenous lead patients were younger, with higher rates of transposition of the great vessels and common ventricle patients compared with transvenous lead patients.