The jugular approach for leadless pacing. A novel and safe alternative

AIMS

To evaluate safety of leadless pacemaker implantation through the internal jugular vein in a larger cohort with longer follow-up. Moreover, feasibility of non-apical pacing as well as relation between pacing site and QRS duration were assessed.

METHODS

82 consecutive patients, who received a leadless pacemaker though the internal jugular vein were included. Electrical parameters were measured at regular follow-up and any complications were registered. Paced QRS interval was compared for three pacing sites, RVOT, RV mid septum and RV apical septum.

RESULTS

In all patients the leadless pacemaker was implanted successfully. In 69 patients the device was implanted in a non-apical position. In 71% of cases, the device could be deployed at first attempt. The median fluoroscopy time was 4.4minutes (range 0.9-51-) The paced QRS interval was significantly narrower for non-apical pacing compared to apical pacing 156ms. vs 179 ms. P = 0.04 respectively. During mean follow-up of 16 months (range 0-43 months) electrical parameters remained stable. Two complications occurred which could be resolved during the implant procedure. There were no access site related complications.

CONCLUSION

The jugular approach for leadless pacemaker implantation is feasibly and may avoid vascular complications. It facilitates non-apical positioning of leadless pacemakers leading to a narrower paced QRS interval. The jugular approach allows for immediate post procedural ambulation. This article is protected by copyright. All rights reserved.

Multielectrode Contact Measurement Can Improve Long-Term Outcome of Pulmonary Vein Isolation Using Circular Single-Pulse Electroporation Ablation

BACKGROUND

Irreversible electroporation (IRE) ablation is generally performed with multielectrode catheters. Electrode-tissue contact is an important predictor for the success of pulmonary vein (PV) isolation; however, contact force is difficult to measure with multielectrode ablation catheters. In a preclinical study, we assessed the feasibility of a multielectrode impedance system (MEIS) as a predictor of long-term success of PV isolation. In addition, we present the first-in-human clinical experience with MEIS.

METHODS

In 10 pigs, one PV was ablated based on impedance (MEIS group), and the other PV was solely based on local electrogram information (electrophysiological group). IRE ablations were performed at 200 J. After 3 months, recurrence of conduction was assessed. Subsequently, in 30 patients undergoing PV isolation with IRE, MEIS was evaluated and MEIS contact values were compared to local electrograms.

RESULTS

In the porcine study, 43 IRE applications were delivered in 19 PVs. Acutely, no reconnections were observed in either group. After 3 months, 0 versus 3 (P=0.21) PVs showed conduction recurrence in the MEIS and electrophysiological groups, respectively. Results from the clinical study showed a significant linear relation was found between mean MEIS value and bipolar dV/dt (r²=0.49, P<0.001), with a slope of 20.6 mV/s per Ohm.

CONCLUSIONS

Data from the animal study suggest that MEIS values predict effective IRE applications. For the long-term success of electrical PV isolation with circular IRE applications, no significant difference in efficacy was found between ablation based on the measurement of electrode interface impedance and ablation using the classical electrophysiological approach for determining electrode-tissue contact. Experiences of the first clinical use of MEIS were promising and serve as an important basis for future research.

Characteristics and time course of acute and chronic myocardial lesion formation after electroporation ablation in the porcine model

INTRODUCTION

Electroporation ablation creates deep and wide myocardial lesions. No data are available on time course and characteristics of acute lesion formation.

METHODS

For the acute phase of myocardial lesion development, 7 pigs were investigated. Single 200J applications were delivered at 4 different epicardial right ventricular sites using a linear suction device, yielding a total of 28 lesions. Timing of applications was designed to yield lesions at 7 time points: 0, 10, 20, 30, 40, 50, 60 minutes, with 4 lesions per time point. After euthanization, lesion characteristics were histologically investigated. For the chronic phase of myocardial lesion development, tissue samples were used from previously conducted studies where tissue was obtained at 3 weeks and 3 months after electroporation ablation.

RESULTS

Acute myocardial lesions induce a necrosis pattern with contraction band necrosis and interstitial edema, immediately present after electroporation ablation. No further histological changes such as hemorrhage or influx of inflammatory cells occurred in the first hour. After 3 weeks, the lesions consisted of sharply demarcated loose connective tissue that further developed to more fibrotic scar tissue after 3 months without additional changes. Within the scar tissue arteries and nerves were unaffected.

CONCLUSION

Electroporation ablation immediately induces contraction band necrosis and edema without additional tissue changes in the first hour. After 3 weeks a sharply demarked scar has been developed that remains stable during follow up of 3 months. This is highly relevant for clinical application of electroporation ablation in terms of the electrophysiological endpoint and waiting period after ablation. This article is protected by copyright. All rights reserved.

High-frequency irreversible electroporation for cardiac ablation using an asymmetrical waveform

Background

Irreversible electroporation (IRE) using direct current (DC) is an effective method for the ablation of cardiac tissue. A major drawback of the use of DC-IRE, however, are two problems: requirement of general anesthesia due to severe muscle contractions and the formation of bubbles containing gaseous products from electrolysis. The use of high-frequency alternating current (HF-IRE) is expected to solve both problems, because HF-IRE produces little to no muscle spasms and does not cause electrolysis.

Methods

In the present study, we introduce a novel asymmetric, high-frequency (aHF) waveform for HF-IRE and present the results of a first, small, animal study to test its efficacy.

Results

The data of the experiments suggest that the aHF waveform creates significantly deeper lesions than a symmetric HF waveform of the same energy and frequency (p = 0.003).

Conclusion

We therefore conclude that the use of the aHF enhances the feasibility of the HF-IRE method.

Leadless pacing: Going for the jugular

Background

Leadless pacing is generally performed from a femoral approach. However, the femoral route is not always available. Until now, data regarding implantation using a jugular approach other than a single‐case report were lacking.

Methods

The case records of all patients who underwent internal jugular venous (IJV) leadless pacemaker implantation (Micra, Medtronic, Dublin, Ireland) at our center were analyzed retrospectively.

Results

Nineteen patients underwent IJV leadless pacemaker implantation, nine females, mean age of 77.5 ±9.6  years; permanent atrial fibrillation in all patients with normal left ventricular ejection fraction. Implant indication was atrioventricular conduction disturbance in 10, pre‐AV node ablation in seven, and replacement of a conventional VVI pacemaker in two (infection in one and lead malfunction in the other). The device was positioned at the superior septum in seven patients, apicoseptal in seven patients, and midseptal in five patients. In 12 patients, a sufficient device position was obtained at the first attempt, in three at the second, in one at the third, in one at the fourth, and in two at the sixth attempt.

The mean pacing threshold was 0.56 ± 0.39V at 0.24‐ms pulse width, sensed amplitude was 9.1 ± 3.2 mV, mean fluoroscopy duration was 3.1 ± 1.6 min. There were no vascular or other complications. At follow‐up, electrical parameters remained stable in 18 of 19 patients.

Conclusion

Although experience is minimal, we suggest that the IJV approach is safe and may be considered in patients where the femoral approach is contraindicated.

Novel method for electrode-tissue contact measurement with multi-electrode catheters

Aims

With multi-electrode catheters, measuring contact force (CF) on each electrode is technically challenging. Present electrical methods, like the electrical coupling index (ECI) may yield false positive values in pulmonary veins. We developed a novel method that measures electrode-interface resistance (IR) by applying a very local electrical field between neighbouring catheter electrodes while measuring voltage between each catheter electrode and a skin patch. The aim of this study was to evaluate the new IR method to measure electrode-tissue contact.

Methods and results

In vitro, effects of remote high-impedance structures were studied. In addition, both ECI and IR were directly compared with true electrode-tissue CF. In five pigs, the influence of high-impedance pulmonary tissue on ECI and IR was investigated while navigating the free floating catheter into the caval veins. Inside the left atrium (LA), IR was directly compared with CF. Finally, multi-electrode IR measurements in the LA and inferior pulmonary vein (IPV) were compared. In vitro, IR is much less affected by remote high-impedance structures than ECI (3% vs. 32%). Both IR and ECI strongly relate to electrode-tissue CF (r2 = 0.84). In vivo, and in contrast to ECI, IR was not affected by nearby pulmonary tissue. Inside the LA, a strong relation between IR and CF was found. This finding was confirmed by simultaneous multi-electrode measurements in LA and IPV.

Conclusion

Data of the present study suggest that electrode-tissue contact affects the IR while being highly insensitive to remote structures. This method facilitates electrode-tissue contact measurements with circular multi-electrode ablation catheters.

Acute and Long-Term Effects of Full-Power Electroporation Ablation Directly on the Porcine Esophagus

Background—

Esophageal ulceration and fistula are complications of pulmonary vein isolation using thermal energy sources. Irreversible electroporation is a novel, nonthermal ablation modality for pulmonary vein isolation. A single 200 J application can create deep myocardial lesions. Acute and chronic effects of this new energy source on the esophagus are unknown.

Methods and Results—

In 8 pigs (±70 kg), the suprasternal esophagus was surgically exposed. A linear suction device with a single 35-mm long and 6-mm wide protruding linear electrode inside a plastic suction cup was used for ablation. Single, nonarcing, nonbarotraumatic, cathodal 100 and 200 J applications were delivered at 2 different sites on the anterior esophageal adventitia. No proton-pump inhibitors were administered during follow-up. Esophagoscopy was performed at days 2 and 7. After euthanasia at day 60, the esophagus was evaluated visually and histologically. All ablations were uneventful. Esophagoscopy at day 2 showed small white densities in the ablated areas, which appeared to be small intraepithelial vesicles. No epithelial erythema, erosions, or ulcerations were seen. At day 7, all densities had disappeared, and all esophaguses appeared completely normalized. After euthanasia, there were no macroscopically visible lesions on the adventitia or epithelium. Histologically, a small scar was observed at the outer part of the muscular layer, whereas the mucosa and submucosa were normal.

Conclusions—

Esophageal architecture remains unaffected 2 months after irreversible electroporation, purposely targeting the adventitia. Irreversible electroporation seems to be a safe modality for catheter ablation near the esophagus.

Myocardial Lesion Size After Epicardial Electroporation Catheter Ablation After Subxiphoid Puncture

Background—

Irreversible electroporation is a promising nonthermal ablation modality able to create deep myocardial lesions. We investigated lesion size after epicardial electroporation catheter ablation with various energy levels after subxiphoid pericardial puncture.

Methods and Results—

In six 6-month-old pigs (60–75 kg), a custom deflectable octopolar 12-mm circular catheter with 2-mm ring electrodes was introduced via a deflectable sheath after pericardial access by subxiphoid puncture. Nonarcing, nonbarotraumatic, cathodal 50, 100, and 200 J electroporation applications were delivered randomly on the basal, mid and lateral left ventricle. After 3-month survival, myocardial lesion size and degree of intimal hyperplasia of the coronary arteries were analyzed histologically. Five animals survived the follow-up without complications and 1 animal died of shock after the subxiphoid puncture. At autopsy, whitish circular scars with indentation of the epicardium could be identified. Average lesion depths of the 50-, 100-, and 200-J lesions were 5.0±2.1, 7.0±2.0, and 11.9±1.5 mm, respectively. Average lesion widths of the 50-, 100-, and 200-J lesions were 16.6±1.1, 16.2±4.3, and 19.8±1.8 mm, respectively. In the 100- and 200-J cross sections, transmural left ventricular lesions and significant tissue shrinkage were observed. No intimal hyperplasia of the coronary arteries was observed.

Conclusions—

Epicardial electroporation ablation after subxiphoid pericardial puncture can create deep, wide, and transmural ventricular myocardial lesions. There is a significant relationship between the amounts of electroporation energy delivered epicardially and lesion size in the absence of major adverse events.

Myocardial Lesion Depth With Circular Electroporation Ablation

Background—

Recently, we demonstrated the feasibility and safety of circular electroporation ablation in porcine pulmonary vein ostia, but the relationship between the magnitude of the application and lesion dimensions is still unknown.

Methods and Results—

An in vivo porcine study was performed on left ventricular epicardium submerged under 10 mm of blood, using devices that mimic a 20-mm-diameter 7F circular ablation catheter. Model D contained 10 separate electrodes, whereas model M consisted of 1 circular electrode. Ablations were performed at 50, 100, and 200 J with model D and at 100 J with model M. Lesion dimensions were measured after 3-week survival. All applications resulted in smooth voltage waveforms demonstrating the absence of vapor globe formation, arcing, and a pressure wave. Applications up to 100 J with model D resulted in separate lesions under the electrodes. At 200 J, continuous deep circular lesions were created despite the use of separate electrodes. There was a significant relationship between applied current and median lesion depth, with a slope of 0.17 mm/A. At 100 J, there was no difference in lesion depth or width between models D and M. The electrodes and ablation site directly after ablation showed no signs of thermal damage.

Conclusions—

In an epicardial porcine model with blood around the application site, continuous circular lesions, deep enough for electric pulmonary vein isolation, were created with a single circular 200-J application. Lesions were continuous despite the use of separate electrodes. Lesion depth increased with the magnitude of the application.

Can optimization of pacing settings compensate for a non-optimal left ventricular pacing site?

AIMS

Optimal left ventricular (LV) lead position improves the response to cardiac resynchronization therapy (CRT). However, in some patients it is not possible to position the LV lead at an optimal pacing site. The aim of this study was to determine whether optimization of the pacing settings atrioventricular delay (AVD) and interventricular delay (VVD) can compensate for a non-optimal LV pacing site.

METHODS AND RESULTS

In 16 patients with heart failure [New York Heart Association class III (13) or IV (3), median QRS duration of 172 ms and median LV ejection fraction of 20%] the acute haemodynamic effect of biventricular pacing was assessed at > or =2 pacing sites by the increase in maximum rate of LV pressure rise (%dP/dt(max)). At each site the AVD and VVD were optimized. Biventricular pacing with nominal settings at a non-optimal LV pacing site improved dP/dt(max) by 12.8% (-0.5 to 23.2%). This could be further improved by 6.5 percentage points (1.2-13.9) by optimization of pacing settings (P = 0.001) and by 9.9 percentage points (3.7-13.3, P = 0.004) by optimization of pacing site. Optimization of the LV pacing site and pacing settings together improved %dP/dt(max) by 16.2 per cent points (10.0-21.8, P < 0.001).

CONCLUSION

Optimization of the AVD and VVD can partly compensate for a non-optimal LV pacing site. However, a combination of an optimal LV pacing site and optimized pacing settings gives the best acute haemodynamic response.