Pulsed-field ablation for paroxysmal atrial fibrillation: An indirect comparison of effectiveness among three proprietary devices conducted in the absence of randomized trials

INTRODUCTION

In patients with paroxysmal atrial fibrillation, pulsed-field ablation has been developed as an alternative to thermal ablation. Three devices are currently available: Farawave by Boston, PulseSelect by Medtronic, and Varipulse by Johnson. In the present report, we studied the outcomes at 12 months of these three devices using indirect comparisons.

METHODS

A standard PubMed search was conducted that identified all studies evaluating these devices in patients with paroxysmal atrial fibrillation. The endpoint was freedom from arrhythmia recurrence. Kaplan-Meier curves were subjected to the IPDfromKM method that generated reconstructed patients. Standard time-to-event statistical testss (including heterogeneity assessment) were performed.

RESULTS

Our analysis included 9 studies (8 single-arm and 1 randomized trial based on Farawave for a total of 1916 patients). A significant heterogeneity was found across the trials using Farawave because the outcomes found in the single-arm trials were better than those found in the randomized trial. Farawave (according exclusively to the results of the randomized trial), PulseSelect, and Varipulse showed a similar time-course of their respective outcomes with no significant difference. The single-arm trials using Farawave showed better outcomes than the randomized trial using Farawave and the pivotal trials using PulseSelect and Varipulse.

DISCUSSION

Our study provided an updated overview of all the studies that have so far used pulsed-fileld ablation in patients with paroxysmal atrial fibrillation.

Dual energy for pulmonary vein isolation using dual-energy focal ablation technology integrated with a three-dimensional mapping system: SmartfIRE 3-month results

AIMS

Contact force (CF)-sensing radiofrequency (RF) catheters with an ablation index have shown reproducible outcomes for the treatment of atrial fibrillation (AF) in large multicentre studies. A dual-energy (DE) focal CF catheter to deliver RF and unipolar/biphasic pulsed field ablation (PFA), integrated with a three-dimensional (3D) mapping system, can provide operators with additional flexibility. The SmartfIRE study assessed the safety and efficacy of this novel technology for the treatment of drug-refractory, symptomatic paroxysmal AF. Results at 3 months post-ablation are presented here.

METHODS AND RESULTS

Pulmonary vein isolation (PVI) was performed using a DE focal, irrigated CF-sensing catheter with the recommendation of PFA at posterior/inferior and RF ablation at the anterior/ridge/carina segments. Irrespective of energy, a tag size of 3 mm; an inter-tag distance ≤6 mm; a target index of 550 for anterior, roof, ridge, and carina; and a target index of 400 for posterior and inferior were recommended. Cavotricuspid isthmus ablation was permitted in patients with documented typical atrial flutter. The primary effectiveness endpoint was acute procedural success. The primary safety endpoint was the rate of primary adverse events (PAEs) within 7 days of the procedure. A prespecified patient subset underwent oesophageal endoscopy (EE; 72 h post-procedure), neurological assessment (NA; pre-procedure and discharge), and cardiac computed tomography (CT)/magnetic resonance angiogram (MRA) imaging (pre-procedure and 3 months post-procedure) for additional safety evaluation, and a mandatory remapping procedure (Day 75 ± 15) for PVI durability assessment. Of 149 patients enrolled between February and June 2023, 140 had the study catheter inserted (safety analysis set) and 137 had ablation energy delivered (per-protocol analysis set). The median (Q1/Q3) total procedure and fluoroscopy times were 108.0 (91.0/126.0) and 4.2 (2.3/7.7) min (n = 137). The acute procedural success rate was 100%. First-pass isolation was achieved in 89.1% of patients and 96.8% of veins. Cavotricuspid isthmus ablations were successfully performed in 12 patients [pulsed field (PF) only: 6, RF only: 5, and RF/PF: 1]. The PAE rate was 4.4% [6/137 patients; 2 pulmonary vein (PV) stenoses, 2 cardiac tamponades/perforations, 1 stroke, and 1 pericarditis]. No coronary artery spasm was reported. No oesophageal lesion was seen in the EE subset (0/31, 0%). In the NA subset (n = 30), microemboli lesions were identified in 2 patients (2/30, 6.7%), both of which were resolved at follow-up; only 1 was symptomatic (silent cerebral lesion, 3.3%). In the CT/MRA subset (n = 30), severe PV narrowing (of >70%) was detected in 2 patients (2/30, 6.7%; vein level 2/128, 1.6%), of whom 1 underwent dilatation and stenting and 1 was asymptomatic; both were associated with high index values and a small inter-tag distance. In the PV durability subset (n = 30), 100/115 treated PVs (87%) were durably isolated and 18/30 patients (60.0%) had all PVs durably isolated.

CONCLUSION

A DE focal CF catheter with 3D mapping integration showed a 100% acute success rate with an acceptable safety profile in the treatment of paroxysmal AF. Prespecified 3-month remapping showed notable PVI durability.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT05752487.

Durable pulmonary vein isolation with optimized high-power and very high-power short-duration temperature-controlled ablation: A step-by-step guide

INTRODUCTION

Through systematic scientific rigor, the CLOSE guided workflow was developed and has been shown to improve pulmonary vein isolation durability. However, this technique was developed at a time when using power-controlled ablation catheters with conventional power ranges was the norm. There has been increased adoption of a high-power and very high-power short-duration ablation practice propelled by the availability of the temperature-controlled radiofrequency QDOT MICRO catheter.

METHODS

There are fundamental differences in biophysics between very high-powered temperature guided ablation and conventional ablation strategy that may impact patient outcomes. The catheter's design and ablation modes offer flexibility in technique while accommodating the individual operator's clinical discretion and preference to deliver a durable, transmural, and contiguous lesion set.

RESULTS

Here, we provide recommendations for 3 different workflows using the QDOT MICRO catheter in a step-by-step manner for pulmonary vein isolation based on our cumulative experience as early adopters of the technology and the data available in the scientific literature.

CONCLUSIONS

With standardization, temperature-controlled ablation with the QDOT MICRO catheter provides operators the flexibility of implementing different ablation strategies to ensure durable contiguous pulmonary vein isolation depending on patient characteristics.

Determination of Continuity Index Values in Atrial Fibrillation Ablation with Proactive Esophageal Cooling

Radiofrequency (RF) ablation to perform pulmonary vein isolation (PVI) for the treatment of atrial fibrillation involves some risk to collateral structures, including the esophagus. Proactive esophageal cooling using a dedicated device has been granted marketing authorization by the Food and Drug Administration (FDA) to reduce the risk of ablation-related esophageal injury due to RF cardiac ablation procedures, and more recent data also suggest that esophageal cooling may contribute to improved long-term efficacy of treatment. A mechanistic underpinning explaining these findings exists through the quantification of lesion placement contiguity defined as the Continuity Index (CI). Kautzner et al. quantified the CI by the order of lesion placement, such that whenever a lesion is placed non-adjacent to the prior lesion, the CI is incremented by the number of segments the catheter tip has moved over. To facilitate real-time calculation of the CI and encourage further adoption of this instrument, we propose a modification in which the placement of non-adjacent lesions increments the CI by only one unit, avoiding the need to count potentially nebulous markers of atrial segmentation. The objective of this protocol is to describe the methods of calculating the CI both prospectively during real-time PVI cases and retrospectively using recorded case data. A comparison of the results obtained between cases that utilized proactive esophageal cooling and cases that used luminal esophageal temperature (LET) monitoring is then provided.

In Vivo Findings of a Novel Focal Ablation Catheter: Focused Electric Field Catheter Tip

Current catheter designs used for radiofrequency (RF) in cardiac tissue achieve limited ablation depth as lesion size is driven heavily by resistive heating at the tissue surface. A catheter with a truncated, dome-shaped tip with a toroidal surface designed for focal RF ablation was recently described. This in vivo study compares lesion characteristics between a second-generation focused electric field (FEF) catheter vs a standard irrigated catheter using RF energy in a beating heart model. We performed in vivo ablations using RF energy with the FEF ablation catheter tip (Focused Therapeutics) and an irrigated Blazer catheter (Boston Scientific) under identical power, duration, and irrigation rates. In addition, RF dosing at high power and duration was examined using the FEF catheter. Intracardiac echocardiography was used to evaluate steam pops and catheter tip angle relative to the tissue surface. Studies were terminal and lesion size was measured following 2,3,5-triphenyltetrazolium chloride staining. Ablations were performed in 6 swine (FEF, n = 31; control, n = 8). FEF ablation lesions (n = 7) were deeper (15.6 ± 2.6 mm vs 7.5 ± 1.9 mm; P < 0.001) and wider (18.4 ± 2.9 mm vs 12.6 ± 2.4 mm; P < 0.001) than lesions delivered with the control irrigated catheter (n = 8) under the same parameters. Thirty-two percent (n = 10 of 31) of lesions delivered from the left ventricle endocardial surface using the FEF catheter were transmural. No steam pops were observed with delivery of FEF lesions (n = 31). The angle of incidence did not significantly affect FEF lesion size. In this in vivo preclinical study, the FEF catheter, which provides focused energy delivery, resulted in significantly larger lesions than the irrigated control catheter without steam pops. Approximately one-third of ablations with the FEF catheter delivered from the endocardial left ventricular surface resulted in transmural lesions.

First-in-human clinical series of a novel conformable large-lattice pulsed field ablation catheter for pulmonary vein isolation

AIMS

Pulsed field ablation (PFA) has significant advantages over conventional thermal ablation of atrial fibrillation (AF). This first-in-human, single-arm trial to treat paroxysmal AF (PAF) assessed the efficiency, safety, pulmonary vein isolation (PVI) durability and one-year clinical effectiveness of an 8 Fr, large-lattice, conformable single-shot PFA catheter together with a dedicated electroanatomical mapping system.

METHODS AND RESULTS

After rendering the PV anatomy, the PFA catheter delivered monopolar, biphasic pulse trains (5-6 s per application; ∼4 applications per PV). Three waveforms were tested: PULSE1, PULSE2, and PULSE3. Follow-up included ECGs, Holters at 6 and 12 months, and symptomatic and scheduled transtelephonic monitoring. The primary and secondary efficacy endpoints were acute PVI and post-blanking atrial arrhythmia recurrence, respectively. Invasive remapping was conducted ∼75 days post-ablation. At three centres, PVI was performed by five operators in 85 patients using PULSE1 (n = 30), PULSE2 (n = 20), and PULSE3 (n = 35). Acute PVI was achieved in 100% of PVs using 3.9 ± 1.4 PFA applications per PV. Overall procedure, transpired ablation, PFA catheter dwell and fluoroscopy times were 56.5 ± 21.6, 10.0 ± 6.0, 19.1 ± 9.3, and 5.7 ± 3.9 min, respectively. No pre-defined primary safety events occurred. Upon remapping, PVI durability was 90% and 99% on a per-vein basis for the total and PULSE3 cohort, respectively. The Kaplan-Meier estimate of one-year freedom from atrial arrhythmias was 81.8% (95% CI 70.2-89.2%) for the total, and 100% (95% CI 80.6-100%) for the PULSE3 cohort.

CONCLUSION

Pulmonary vein isolation (PVI) utilizing a conformable single-shot PFA catheter to treat PAF was efficient, safe, and effective, with durable lesions demonstrated upon remapping.

Optimizing transseptal puncture guided by three-dimensional mapping: the role of a unipolar electrogram in a needle tip

AIMS

A three-dimensional electroanatomic mapping system-guided transseptal puncture (3D-TSP), without fluoroscopy or echocardiography, has been only minimally reported. Indications for 3D-TSP remain unclear. Against this background, this study aims to establish a precise technique and create a workflow for validating and selecting eligible patients for fluoroless 3D-TSP.

METHODS AND RESULTS

We developed a new methodology for 3D-TSP based on a unipolar electrogram derived from a transseptal needle tip (UEGM tip) in 102 patients (the derivation cohort) with intracardiac echocardiography (ICE) from March 2018 to February 2019. The apparent current of injury (COI) was recorded at the muscular limbus of the foramen ovalis (FO) on the UEGM tip (sinus rhythm: 2.57 ± 0.95 mV, atrial fibrillation: 1.92 ± 0.77 mV), which then disappeared or significantly reduced at the central FO. Changes in the COI, serving as a major criterion to establish a 3D-TSP workflow, proved to be the most valuable indicator for identifying the FO in 99% (101/102) of patients compared with three previous techniques (three minor criteria) of reduction in atrial unipolar or bipolar potential and FO protrusion. A total of 99.9% (1042/1043) patients in the validation cohort underwent successful 3D-TSP through the workflow from March 2019 to July 2023. Intracardiac echocardiography guidance was required for 6.6% (69/1042) of patients. All four criteria were met in 740 patients, resulting in a 100% pure fluoroless 3D-TSP success rate.

CONCLUSION

In most patients, fluoroless 3D-TSP was successfully achieved using changes in the COI on the UEGM tip. Patients who met all four criteria were considered suitable for 3D-TSP, while those who met none required ICE guidance.

Pivotal Study of a Novel Motor-Driven Endoscopic Ablation System

[Figure: see text].

Slit-based irrigation catheters can reduce procedure-related ischemic stroke in atrial fibrillation patients undergoing radiofrequency catheter ablation

Open irrigation ablation catheters are now the standard in radiofrequency catheter ablation (RFCA) of atrial fibrillation (AF). Among various irrigation catheters, laser-cut slit-based irrigation system (Cool Flex and FlexAbility) has a unique design to cool the catheter tip more efficiently. We aimed to assess the safety of slit-based irrigation catheters regarding prevention of procedure-related ischemic complication in AF patients undergoing RFCA. The analysis was performed with Korea University Medicine Anam Hospital RFCA registry. Procedure-related ischemic complication was defined as ischemic stroke or transient ischemic attack (TIA) occurring within 30 days after RFCA. Patients were divided into 3 groups: non-irrigation, hole-based irrigation, and slit-based irrigation catheter groups. A total of 3,120 AF patients underwent first RFCA. Non-irrigation, non-slit-based irrigation, and slit-based irrigation catheters were used in 290, 1,539, and 1,291 patients, respectively. As compared with non-irrigation and non-slit-based irrigation catheter groups, slit-based irrigation catheter group had significantly older age, higher prevalence of non-paroxysmal AF, large left atrial size, and decreased left atrial appendage flow velocity. The CHA₂DS₂-VASc score was not different among the 3 groups. Procedure-related ischemic complication occurred in 17 patients (0.54%) with 16 ischemic strokes and 1 TIA event: 5/290 (1.72%), 11/1,539 (0.71%), and 1/1,291 (0.08%) events in non-irrigation, non-slit-based irrigation, and slit-based irrigation catheter groups, respectively (p = 0.001). Slit-based irrigation catheter was superior in direct comparison with non-slit-based irrigation catheter (0.71% vs. 0.08%; p = 0.009). Slit-based irrigation catheters were highly effective in preventing procedure-related ischemic complications.

A Percutaneous Catheter for In Vivo Hyperspectral Imaging of Cardiac Tissue: Challenges, Solutions and Future Directions

PURPOSE

Multiple studies have shown that spectral analysis of tissue autofluorescence can be used as a live indicator for various pathophysiological states of cardiac tissue, including ischemia, ablation-induced damage, or scar formation. Yet today there are no percutaneous devices that can detect autofluorescence signals from inside a beating heart. Our aim was to develop a prototype catheter to demonstrate the feasibility of doing so.

METHODS AND RESULTS

Here we summarize technical solutions leading to the development of a percutaneous catheter capable of multispectral imaging of intracardiac surfaces. The process included several iterations of light sources, optical filtering, and image acquisition techniques. The developed system included a compliant balloon, 355 nm laser irradiance, a high-sensitivity CCD, bandpass filtering, and image acquisition synchronized with the cardiac cycle. It enabled us to capture autofluorescence images from multiple spectral bands within the visible range while illuminating the endocardial surface with ultraviolet light. Principal component analysis and other spectral unmixing post-processing algorithms were then used to reveal target tissue.

CONCLUSION

Based on the success of our prototype system, we are confident that the development of ever more sensitive cameras, recent advances in tunable filters, fiber bundles, and other optical and computational components makes it possible to create percutaneous catheters capable of acquiring hyper or multispectral hypercubes, including those based on autofluorescence, in real-time. This opens the door for widespread use of this methodology for high-resolution intraoperative imaging of internal tissues and organs-including cardiovascular applications.

Balloon-Based Ablation Technologies

Pulmonary vein isolation (PVI) is widely accepted as the mainstay of interventional treatment of atrial fibrillation. Ablation with radiofrequency (RF) point-by-point catheters is highly operator dependent and may fail because of ineffective lesions or gaps. Several balloon-based catheter ablation technologies have emerged as an alternative to effect PVI. Cryoballoon ablation is widely used, and current iterations of the technology show comparable acute and long-term efficacy to RF ablation. Techniques such as time to isolation have emerged to improve efficacy and safety. Laser balloon is a highly compliant variably sized balloon that has been validated as an effective strategy for PVI.

Pulsed Field Ablation Using a Lattice Electrode for Focal Energy Delivery: Biophysical Characterization, Lesion Durability, and Safety Evaluation

BACKGROUND

Pulsed field ablation (PFA) is a nonthermal energy that may provide safety advantages over radiofrequency ablation (RFA). One-shot PFA catheters have been developed for pulmonary vein isolation, but they do not permit flexible lesion sets. This study investigated a novel lattice-tip catheter designed for focal RFA or PFA ablation.

METHODS

The effects of PFA (biphasic, 24 amperes) were investigated in 25 swine using a lattice-tip catheter and system (Affera Inc). Step 1 (n=14) examined the feasibility to create atrial line of block and described its acute effects on the phrenic nerve and esophagus. Step 2 (n=7) examined the subacute effects of PFA on block durability, phrenic nerve, and esophagus ≥2 weeks. Step 3 compared the effects of PFA and RFA on the esophagus using a mechanical deviation model approximating the esophagus to the right atrium (n=4) and by direct ablation within its lumen (n=4). The effects of endocardial PFA and RFA on the phrenic nerve were also compared (n=10). Histological analysis was performed.

RESULTS

PFA produced acute block in 100% of lines, achieved with 2.1 (1.3-3.2) applications/cm line. Histological analysis following (35 [18-37]) days showed 100% transmurality (thickness range 0.4-3.4 mm) with a lesion width of 19.4 (10.9-27.4 mm). PFA selectively affected cardiomyocytes but spared blood vessels and nervous tissue. PFA applied from the posterior atria (23 [21-25] applications) to the approximated esophagus (6 [4.5-14] mm) produced transmural lesions without esophageal injury. PFA (16.5 [15-18] applications) applied inside the esophageal lumen produced mild edema compared with RFA (13 [12-14] applications) which produced epithelial ulcerations. PFA resulted in no or transient stunning of the phrenic nerve (<5 minutes) without histological changes while RFA produced paralysis.

CONCLUSIONS

PFA using a lattice-tip ablation catheter for focal ablation produced durable atrial lesions and showed lower vulnerability to esophageal or phrenic nerve damage compared with RFA.

A numerical study on the no-touch bipolar radiofrequency ablation

The commonly used radiofrequency ablation (RFA) technique for treating liver cancer is in the monopolar mode. This requires the insertion of the RF electrode directly into the tumor tissue, which increases the risks of tumor track seeding (TTS). One way to overcome TTS is by employing the bipolar RFA, implemented in the no-touch mode. In the no-touch mode, two RF electrodes are inserted into the healthy tissue that surrounds the tumor. The distance between the electrodes and the tumor is defined as the no-touch gap. The ability of the no-touch bipolar RFA to overcome TTS has been demonstrated in laboratory studies; however, little is known about the thermo-physiological responses of the tissue during the ablation process of the no-touch procedure. This will be investigated numerically in the present study. A 3D model of the liver tissue is developed and the no-touch bipolar RFA implemented using a pair of RF electrodes is simulated using the finite element method. In particular, the effects of the no-touch gap on the treatment outcome of the RFA procedure are investigated. Results show that a larger no-touch gap may result incomplete tumor destruction due to the central region of the tumor not being directly affected by the Joule heating phenomenon that is more prominent around the electrodes. This suggests that an improperly selected no-touch gap may result in a reduced efficiency of the no-touch bipolar RFA.

Benefit of Contact Force-Guided Catheter Ablation for Treating Premature Ventricular Contractions

We evaluated whether an irrigated contact force-sensing catheter would improve the safety and effectiveness of radiofrequency ablation of premature ventricular contractions originating from the right ventricular outflow tract. We retrospectively reviewed the charts of patients with symptomatic premature ventricular contractions who underwent ablation with a contact force-sensing catheter (56 patients, SmartTouch) or conventional catheter (59 patients, ThermoCool) at our hospital from August 2013 through December 2015. During a mean follow-up of 16 ± 5 months, 3 patients in the conventional group had recurrences, compared with none in the contact force group. Complications occurred only in the conventional group (one steam pop; 2 ablations suspended because of significantly increasing impedance). In the contact force group, the median contact force during ablation was 10 g (interquartile range, 7-14 g). Times for overall procedure (36.9 ± 5 min), fluoroscopy (86.3 ± 22.7 s), and ablation (60.3 ± 21.4 s) were significantly shorter in the contact force group than in the conventional group (46.2 ± 6.2 min, 107.7 ± 30 s, and 88.7 ± 32.3 s, respectively; P <0.001). In the contact force group, cases with a force-time integral <560 gram-seconds (g-s) had significantly longer procedure and fluoroscopy times (both P <0.001) than did those with a force-time integral ≥560 g-s. These findings suggest that ablation of premature ventricular contractions originating from the right ventricular outflow tract with an irrigated contact force-sensing catheter instead of a conventional catheter shortens overall procedure, fluoroscopy, and ablation times without increasing risk of recurrence or complications.

The Current Status of Devices for the Treatment of Resistant Hypertension

Arterial hypertension is associated with increased cardiovascular morbidity and mortality. Although blood pressure-lowering therapies significantly reduce the risk of major cardiovascular events, blood pressure control remains unsatisfactorily low. Several device-based antihypertensive therapies have been investigated in patients with treatment-resistant hypertension and in patients unable or unwilling to adhere to antihypertensive medication. As the field of device-based therapies is subject to constant change, this review aims at providing an up-to-date overview of different device-based approaches for the treatment of hypertension. These approaches target the sympathetic nervous system (renal denervation, baroreflex amplification therapy, baroreflex activation therapy, and carotid body ablation) or alter mechanical arterial properties by creating an iliac arteriovenous fistula. Notably, the use of all of these treatment options is not recommended for the routine treatment of hypertension by current guidelines but should be investigated in the context of controlled clinical studies.

Radiofrequency Balloon Devices for Atrial Fibrillation Ablation

Despite technological advancements, radiofrequency catheter ablation for pulmonary vein isolation remains a challenging procedure, as maneuvering the catheter to obtain effective lesions is technically complex and time consuming. For this reason, balloon-based ablation systems have been developed, which can quickly and easily isolate the pulmonary veins (single-shot), with outcomes comparable with point-by-point catheter ablation in the paroxysmal atrial fibrillation population. In this review, we discuss 3 balloon-based devices that use radiofrequency to obtain permanent lesions, a relatively emerging technology that may pose as an alternative option to cryoenergy or laser for single-shot pulmonary vein isolation.

Atrial fibrillation ablation with a spring sensor-irrigated contact force-sensing catheter compared with other ablation catheters: systematic literature review and meta-analysis

OBJECTIVES

The objective of our review was to systematically assess available evidence on the effectiveness, safety and efficiency of a spring sensor-irrigated contact force (CF) catheter (THERMOCOOL SMARTTOUCH Catheter (ST)) for percutaneous ablation of paroxysmal or persistent atrial fibrillation (AF), compared with other ablation catheters, or with the ST with the operator blinded to CF data.

DESIGN

Systematic literature review and meta-analysis.

BACKGROUND

Emerging evidence suggests improved clinical outcomes of AF ablation using CF-sensing catheters; however, reviews to date have included data from multiple, distinct CF technologies.

METHODS

We conducted a systematic review and meta-analysis of published studies comparing the use of ST versus other ablation catheters for the treatment of AF. A comprehensive search of electronic and manual sources was conducted. The primary endpoint was freedom from recurrent atrial tachyarrhythmia (AT) at 12 months. Procedural and safety data were also analysed.

RESULTS

Thirty-four studies enrolling 5004 patients were eligible. The use of ST was associated with increased odds of freedom from AT at 12 months (71.0%vs60.8%; OR 1.454, 95% CI 1.12 to 1.88, p=0.004) over the comparator group, and the effect size was most evident in paroxysmal AF patients (75.6%vs64.7%; OR 1.560, 95% CI 1.09 to 2.24, p=0.015). Procedure and fluoroscopy times were shorter with ST (p=0.05 and p<0.01, respectively, vs comparator groups). The reduction in procedure time is estimated at 15.5 min (9.0%), and fluoroscopy time 4.8 min (18.7%). Complication rates, including cardiac tamponade, did not differ between groups.

CONCLUSIONS

Compared with the use of other catheters, AF ablation using the CF-sensing ST catheter for AF is associated with improved success rates, shorter procedure and fluoroscopy times and similar safety profile.

Comparison of parallel and crossed placement of antennas in microwave ablation of 3-5 cm hepatocellular carcinoma

PURPOSE

To evaluate the effects of ablation strategies on local tumor progression (LTP) after microwave ablation (MWA) of hepatocellular carcinomas (HCCs) measuring 3-5 cm.

MATERIALS AND METHODS

Between December 2011 and May 2017, 71 HCC patients with 71 nodules treated by ultrasound(US)-guided percutaneous MWA were divided into parallel (group A) and crossed (group B) antenna placement groups. All patients underwent MWA using two antennas with four insertions. LTP and overall survival (OS) rates were compared between the two groups.

RESULTS

The median follow-up time was 16.8 months. There was no significant difference in the complete ablation rate and treatment sessions between the two groups. LTP was diagnosed in 8 of 48 nodules (16.7%) in group A and 1 of 23 nodules (4.3%) in group B, with no significant difference between two groups (P = 0.115). The 1-, 2-, and 3-year OS rates were 88.5%, 79%, and 71.8% in group A and 93.8%, 87.5%, and 87.5% in group B, respectively (P = 0.236). Multivariate analysis showed that the tumor diameter (P = 0.017), the distance between the antennas (P = 0.032), and the total emission time (P = 0.015) were associated with LTP.

CONCLUSIONS

There were trends with lower LTP and improved OS in group B, despite the lack of statistically significant differences between the two strategies at a level of P < 0.05. The increase of distance between antennas and total emission time will facilitate reductions in LTP rate.

[Design and Research of Thermal Ablation System Based on Dual-frequency Microwave Solid State Source]

Microwave thermal ablation technology is widely used in the treatment of liver tumors because of its minimal invasiveness and small side effects. The precise control of the thermal dose largely determines the therapeutic effect of microwave thermal ablation. However, the current magnetron-based microwave thermal ablation device has the disadvantages of poor power output stability and high operating voltage. In view of the above problems, this paper selected the microwave solid-state source as the core device of microwave output, and designed a dual-frequency microwave thermal ablation system based on 2 450 MHz and 433 MHz. The system used the power detection circuit to perform PID feedback control on the actual output power of the system. The experimental results show that the maximum output power of the system is less than 1 W. The PID algorithm further enhances the accuracy and stability of the system output power while improving the system security. The dual-frequency microwave thermal ablation system designed in this paper can provide a safe and reliable experimental platform for subsequent research.

Cost-reduction strategy for isoproterenol use in radiofrequency catheter ablation procedures

PURPOSE

A cost-reduction strategy for isoproterenol use in radiofrequency catheter ablation procedures was evaluated.

SUMMARY

A medication-use evaluation at a 454-bed tertiary medical center revealed that the cardiac catheterization laboratory was the highest user of isoproterenol. Isoproterenol was removed from all AcuDose-Rx machines Omnicell, Mountain View, CA, and compounding was performed by pharmacy personnel. It was initially provided to the cardiac catheterization laboratory as an 8-µg/mL concentration in 20-mL 0.9% sodium chloride injection syringes with a 24-hour beyond-use date. This resulted in an initial cost savings but with an unacceptably high rate of wastage. Isoproterenol was then compounded as a 4-µg/mL concentration in 30 mL 5% dextrose in water syringes with a 9-day beyond-use date after a thorough literature search supported longer stability with this admixture. After 12 months of our current process, isoproterenol use during radio frequency catheter ablations (RFCAs) in the cardiac catheterization laboratory was reduced by 85%, decreasing the number of ampules used from 11.15 to 1.66 per week.

CONCLUSION

A pharmacy-initiated process to mitigate an extraordinary increase in isoproterenol acquisition cost resulted in a reduction in usage in a tertiary care community hospital. Isoproterenol usage was reduced 85% after two different interventions were implemented, which is estimated to save $1,839 per procedure.

Multicentre randomised trial comparing contact force with electrical coupling index in atrial flutter ablation (VERISMART trial)

Introduction

Electrical coupling index (ECI) and contact force (CF) have been developed to aid lesion formation during catheter ablation. ECI measures tissue impedance and capacitance whilst CF measures direct contact. The aim was to determine whether the presence of catheter / tissue interaction information, such as ECI and CF, reduce time to achieve bidirectional cavotricuspid isthmus block during atrial flutter (AFL) ablation.

Methods

Patients with paroxysmal or persistent AFL were randomised to CF visible (range 5-40g), CF not visible, ECI visible (change of 12%) or ECI not visible. Follow-up occurred at 3 and 6 months and included a 7 day ECG recording. The primary endpoint was time to bidirectional cavotricuspid isthmus block.

Results

114 patients were randomised, 16 were excluded. Time to bidirectional block was significantly shorter when ECI was visible (median 30.0 mins (IQR 31) to median 10.5mins (IQR 12) p 0.023) versus ECI not visible. There was a trend towards a shorter time to bidirectional block when CF was visible. Higher force was applied when CF was visible (median 9.03g (IQR 7.4) vs. 11.3g (5.5) p 0.017). There was no difference in the acute recurrence of conduction between groups. The complication rate was 2%, AFL recurrence was 1.1% and at 6 month follow-up, 12% had atrial fibrillation.

Conclusion

The use of tissue contact information during AFL ablation was associated with reduced time taken to achieve bidirectional block when ECI was visible. Contact force data improved contact when visible with a trend towards a reduction in the procedural endpoint.

ClinicalTrials.gov trial identifier: NCT02490033.

[Study on Effect of 4 Different Conduction Pathways on Initiation and Maintenance of Atrial Fibrillation Based on Atrial Simulation]

OBJECTIVE

In this study,computational modelling was used to study whether different conduction pathways have impact on the AF initiation and maintenance based on a human atrial model.

METHODS

MRI images from one patient who has atrial fibrillation were used to reconstruct the human atrial anatomical model.The number of MRI images was 112.In order to study the effect of different conduction pathways to AF,4 different atrial models were generated in this study,which were biatrial conduction via only LFO;biatrial conduction via only CS;biatrial conduction via both LFO and CS;model without biatrial conduction.

RESULTS

In the case of biatrial conduction simulation via only LFO,the same re-entries were induced as in the LFO and CS case.But for the two cases of only CS conduction and both LFO and CS cannot conduct electricity,one stimulus site induced unsustained re-entry which only lasted for 2 cycles,and then terminated.The other two sites induced the same re-entries as in the previously described two cases,which were biatrial conduction simulation via both LFO and CS and only LFO.

CONCLUSIONS

Our simulation showed that these conduction pathways played a minor role in the re-entry initiation and maintenance,the possible explanation is that all the re-entries induced in our simulation is local drivers and maintained by fibrosis.

New real-time patient radiation dosimeter for use in radiofrequency catheter ablation

In a previous study, we reported on a novel (prototype) real-time patient dosimeter with non-toxic phosphor sensors. In this study, we developed new types of sensors that were smaller than in the previous prototype, and clarified the clinical feasibility of our newly proposed dosimeter. Patient dose measurements obtained with the newly proposed real-time dosimeter were compared with measurements obtained using a calibrated radiophotoluminescence glass reference dosimeter (RPLD). The reference dosimeters were set at almost the same positions as the new real-time dosimeter sensors. We found excellent correlations between the reference RPLD measurements and those obtained using our new real-time dosimeter (r2 = 0.967). However, the new type of dosimeter was found to underestimate radiation skin dose measurements when compared with an RPLD. The most probable reason for this was the size reduction in the phosphor sensor of the new type of dosimeter. We believe that, as a result of reducing the phosphor sensor size, the backscattered X-ray irradiation was underestimated. However, the new dosimeter can accurately determine the absorbed dose by correcting the measured value with calibration factors. The calibration factor for the new type dosimeter was determined (by linear regression) to be ~1.15. New real-time patient dosimeter design would be an effective tool for the real-time measurement of patient skin doses during interventional radiology treatments.

Contact Forces Required to Record Monophasic Action Potentials: A Complement to Catheter Contact Force Measurement

OBJECTIVE

The ability to monitor catheter contact force (CF) plays a major role in assessing radiofrequency ablation, impacting lesion size and arrhythmia recurrence, and dictating ablation duration and/or overall patient safety. Our study sought to determine the relative CFs required to elicit reproducible monophasic action potential (MAP) recordings.

METHODS

The study utilized four swine in which: first, median sternotomies were performed and MAPs were collected from seven ventricular locations on the epicardial surface of each heart; and second, a subset of endocardial signals was recorded from a reanimated heart. In these studies, the initial elicitation and then loss of stable MAP waveforms were recorded, as were their associated catheter CFs (n = 371).

RESULTS

Mean CF at the onset of stable MAP recordings was 14.2 ± 2.9 g for epicardial and 16.6 ± 2.5 g for endocardial locations. Across epicardial locations, no significant differences in CF were required to elicit MAPs. Additionally, endocardial and epicardial CFs for MAPs did not significantly differ for respective locations, i.e., right ventricular septum endocardial versus epicardial. In our study, the catheter CFs required to elicit MAPs were within optimal ranges previously reported for eliciting clinically viable radiofrequency ablations.

CONCLUSION

We believe that MAP recordings could complement CF measurements with electrical data, providing additional clinical feedback for physicians performing cardiac ablation.

SIGNIFICANCE

If applied clinically, MAP recordings could potentially improve ablation outcomes in patients with cardiac arrhythmias.

Differences in treatment outcomes between ultrasound-guided percutaneous microwave ablation and endoscopic thyroidectomy for patients with papillary thyroid microcarcinoma: Protocol for a systematic review and meta-analysis

BACKGROUND

The differences in treatment outcomes between ultrasound (US)-guided percutaneous microwave ablation (PMWA) and endoscopic thyroidectomy for patients with papillary thyroid microcarcinoma (PTMC) remains unknown.

METHODS

An electronic search will be performed for randomized controlled trials or observational studies that reported recurrence and mortality rates in PTMC patients with US-guided PMWA or endoscopic thyroidectomy. Hazard ratios with their 95% confidence intervals will be calculated using fixed- or random-effects models according to heterogeneity.

RESULTS

This study will present the differences in treatment outcomes between US-guided PMWA and endoscopic thyroidectomy for patients with PTMC by pooling the results of individual studies.

CONCLUSION

The results of this study would provide vigorous evidence in this issue and offer the guidance to both clinical decision-making and future research.

ETHICS AND DISSEMINATION

Ethical approval is not applicable for this study.

PROSPERO REGISTRATION NUMBER

CRD42018112320.

[Frequency-Selectable RF Ablation Treatment System]

In order to support study of new radiofrequency ablation treatments and finally realize of precise conformal ablation of targeted tissue, this paper proposed a system which is able to generate radio frequency currents at different frequencies. The designed system bases on the basic principle of Class E power amplifier and uses MSP430 microcontroller as a controller and uses a touch screen as human-machine interface to design a frequency-selectable radiofrequency ablation treatment system,. The RF signals at frequencies of 230 kHz, 460 kHz, 920 kHz, and 2 000 kHz were tested to verify the feasibility of the system, and by using a tissue phantom, tested the heating ability of the RF signals at frequencies of 460 kHz, 920 kHz, and 2 000 kHz. The results show the device could well heat the tissue at the three frequencies. The study has also found that both the highest temperature and the ablation area decreases with RF frequency, when using the constant power control mode.

Identification of Radiofrequency Ablation Catheter Parameters That May Induce Intracardiac Steam Pops: Direct Visualization of Elicitation in Reanimated Swine Hearts

Radiofrequency, a common ablation modality, is used clinically to terminate cardiac arrhythmias. With excessive heating, complications sometimes occur when the applied energy generates steam pops, which cause release of energy in the form of tissue and/or air emboli. In this study, we investigated numerous parameters potentially associated with intracardiac steam pops including (1) wattage, (2) catheter tip temperature, (3) catheter irrigation, (4) anatomic site, and (5) repeat ablations at a given site. Using unique Visible Heart® methodologies in reanimated swine hearts, we visualized 539 ablations; steam pops developed in 140 of these ablations. The incidence of steam pops significantly increased for both nonirrigated and irrigated ablations at 40 W (p < 0.005), and for nonirrigated ablations with catheter contact angles perpendicular to the tissue or that encompassed larger surface areas (p < 0.05). To minimize the incidence of steam pops, clinicians performing radiofrequency ablations must consider catheter parameters.

Hydrodissection of the Retrohepatic Space: A Technique to Physically Separate a Liver Tumour from the Inferior Vena Cava and the Ostia of the Hepatic Veins

OBJECTIVE

To report a technique of percutaneous retrohepatic hydrodissection, highlighting its potential to physically separate liver tumours from the inferior vena cava (IVC) and the ostia of the hepatic veins (HV).

MATERIALS AND METHODS

Between December 2017 and April 2018, hydrodissection of the retrohepatic IVC was performed in 5 patients (5 females; mean age 64.5 years) undergoing percutaneous ablation of 5 liver metastases (mean size: 3.6 cm) located adjacent to the IVC. Number of hydrodissection needles, volume of hydrodissection, separation of tumour/liver parenchyma from IVC/HV post-hydrodissection; technical success of ablation; and complications were tabulated.

RESULTS

Two to three 22G spinal needles were required per case for adequate dissection. Mean volume to obtain sufficient hydrodissection was 410 ml on average. Physical separation of the IVC and tumour/hepatic parenchyma was successful in all cases, by 9 mm on average (range 5-12 mm). It also leaded to physical separation of the ostia of the right and middle HV in all cases. There was no early or delayed complication, notably no venous thrombosis in the post-operative period. All lesions but one were completely ablated after one session at 3-month follow-up. The patient with residual tumour was successfully retreated.

CONCLUSION

Retrohepatic hydrodissection is a feasible technique to separate a tumour from the IVC and/or ostia of the HV. This could potentially limit the heat-sink effect/reduce the risk of thrombosis. Larger follow-up studies are required to assess efficacy on a long-term basis.

[Surgical Ablation Devices]

Fundamental procedure of arrhythmia surgery is to bock conduction of macro-reentry or focal activation. Traditional "cut and sew" technique is effective to make a conduction block without any special devices although it is time consuming and there is some bleeding risk. Surgical ablation devices are easily able to make a conduction block during surgery. It could undergo the minimally invasive cardiovascular surgery (MICS) -maze procedure through the right mini thoracotomy. It is most important to make complete conduction block because incomplete ablation causes residual conduction, resulting in recurrence of atrial fibrillation or atrial tachycardia. Moreover, the left atrial clip is new surgical treatment for atrial fibrillation. This device could avoid thrombus formation and make a conduction block arising from the left atrial appendage.

Contact force-sensing catheters: performance in an ex vivo porcine heart model

PURPOSE

Contact force (CF) catheters are useful to address proper contact during ablation. However, interactions between the ablation process, or its associated irrigation flow changes, with the CF sensing may translate into unexpected CF value fluctuations. We aimed to test for unintentional CF value variations during radiofrequency applications at a fixed applied force, with two commercially available catheters (TactiCath™ and SmartTouch™), and to evaluate its theoretical clinical significance by correlating CF-derived automatic ablation algorithms (force-time integral and lesion index) and actual lesion size at two standard CF values.

METHODS

Four series of 20 perpendicular epicardial ablations (20 W, 60 s, 17 ml/min) were performed on porcine left ventricle submerged in 37 °C saline. Catheters were mechanically fixed at a constant position and evaluated at 10 and 20 g. CF values were digitally analysed before each application changing irrigation rate (2-17-30 ml/min), and during ablation. Finally, lesions were quantified.

RESULTS

Increasing irrigation before ablation led to a slight but significant CF decrease. During ablation, CF showed a reproducible pattern: fast initial decrease, subsequent increase until higher-than-initial values and final plateau phase (CF variation up to 69% at 10 g). CF variability was significantly higher at 10 g and using TactiCath™. There were no major differences in lesion size between catheters at the same initial CF. CF only correlated mildly to lesion measures, and automatic algorithms globally failed to predict lesion size.

CONCLUSIONS

CF measured values spontaneously vary during ablation following a predictable pattern (initial decrease, subsequent increase and final plateau). This is especially remarkable applying lower CF.

Contact-force-guided vs. contact-force-blinded catheter ablation of typical atrial flutter: a prospective study

Aims

It remains unknown whether contact force (CF) sensing technology is of value for cavotricuspid isthmus (CTI) ablation. We prospectively evaluated procedural parameters and outcomes of CF-guided vs. CF-blinded CTI ablation for typical atrial flutter (AFL).

Methods and results

A total of 70 consecutive patients (62.5 ± 10.9 years) undergoing CTI ablation for AFL were prospectively enrolled, 35 in CF-blinded and 35 in CF-guided groups. A CF-sensing catheter (power 25-35 W) was used in all. In the CF-guided group, CF target range was 10-25 g, whereas in the CF-blinded group, the operator was blinded to CF. The isthmus was divided into anterior, middle, and posterior segments for region-specific CF analysis. The procedural endpoint of bidirectional isthmus block following a 20-min observation period was achieved in all. A trend towards lower fluoroscopy and procedure duration was observed when the CF-guided group was compared with the CF-blinded group. The total radiofrequency (RF) energy delivery time required to achieve bidirectional block was significantly lower in the CF-guided vs. CF-blinded group [10.0 min (IQR 8.3;15.1) vs. 15.9 min (IQR 9.6;24.7), P= 0.0020], with a significant inverse correlation between CF and total RF delivery time (r = -0.36; P= 0.0027). Mean CF measurements significantly increased from anterior to posterior anatomical zones of CTI in the CF-blinded group (ANOVA P= 0.0466).

Conclusions

Catheter ablation of AFL guided by real-time CF assessment results in a significant reduction in total RF delivery time. Real-time CF measurements facilitate the maintenance of homogenous efficient contact all along the CTI, particularly in the anterior segment where CF is generally lower.

Surgical linear ablation for ventricular tachycardia with postinfarction ventricular aneurysm

BACKGROUND

Left ventricular aneurysm (LVA) might be an arrhythmogenic substrate. Endocardiectomy and cryoablation for ventricular tachycardia (VT) with LVA can cause extensive myocardial damage. We aimed to evaluate the feasibility of surgical radial linear ablation for VT with LVA guided by electrophysiological mapping.

MATERIALS AND METHODS

Porcine models of VT with LVA were developed. Endocardial and epicardial substrate mapping during sinus rhythm were performed under thoracotomy. Surgical radial linear ablation was achieved by a bipolar radiofrequency ablation device. Outcomes, including procedural success and acute freedom of VT, were analyzed.

RESULTS

Fifteen of 20 pigs developed LVA in a 6-wk survival period. A total of 28 sustained monomorphic VTs were initiated in 13 of 15 pigs (86.67%). The number of potential points captured from the endocardium and epicardium were 319 ± 45 and 358 ± 52 per animal, respectively. The ablative targets containing abnormal potentials were located largely on the border zone of LVA. Eight linear lesions from core to border zone of LVA were achieved per animal in a radial and even manner continuously, and ablation was repeated three times to transect border zone. The acute freedom of VT was 84.62%, P < 0.05.

CONCLUSIONS

Surgical linear endo-epicardial ablation seemed to be feasible in a porcine model with VT and LVA.

Characteristics of Phrenic Nerve Injury During Pulmonary Vein Isolation Using a 28-mm Second-Generation Cryoballoon and Short Freeze Strategy

BACKGROUND

The reported incidence of phrenic nerve injury (PNI) varies owing to different definitions, balloon generations, balloon size, freezing regimen, and protective maneuvers. We evaluated the incidence, predictors, and outcome of PNI during cryoballoon pulmonary vein isolation in a large population.

METHODS AND RESULTS

Five hundred fifty atrial fibrillation patients underwent pulmonary vein isolation using one 28-mm second-generation cryoballoon and single 3-minute freeze strategy under diaphragmatic compound motor action potential (CMAP) monitoring. A total of 34 (6.2%) patients experienced PNI during the right superior and inferior pulmonary vein ablation in 30 and 4 patients, respectively. Applications were interrupted using double-stop techniques after 136 [104-158] second applications, and a pulmonary vein isolation was already achieved in all but one case. The baseline CMAP amplitude and timing of deflation (CMAPdef) were 0.75±0.30 and 0.17±0.17 mV, respectively. Persistent atrial fibrillation, larger right superior pulmonary vein ostia, and deeper balloon positions were associated with higher incidences of PNI. The CMAPdef predicted a PNI recovery delay, and the best cutoff value for predicting PNI recovery by the next day was 0.20 mV (sensitivity 57.1%, specificity 100%). Among 6 patients undergoing second procedures 8.5 (6.7-15.0) months later, the right superior pulmonary vein was durable in 3 with >120 second applications. Despite active balloon deflation, no significant pulmonary vein stenosis was observed in 15 right superior pulmonary veins evaluated 6 (5-9) months later. No patients had symptoms, and the PNI recovered 1 day and 1 month postprocedure in 21 and 4 patients, respectively.

CONCLUSIONS

PNI resulting from cryoballoon ablation was reversible. The double-stop technique is safe, and immediate active deflation following a CMAP decrease appears to be essential for faster PNI recovery.

[Radiofrequency ablation in comprehensive surgical treatment of patients with varicose veins of lower limbs]

Analysed herein are the results of using radiofrequency ablation (RFA) in comprehensive surgical treatment of patients presenting with varicose veins of the lower extremities. The study included a series of ninety-eight 28-to-60-year-old patients (with a total of 105 operations performed) suffering from varicose veins of the lower limbs. Of these, there were 10 men (10.3%) and 88 women (89.7%). Venous disease of clinical class C2 according to the CEAP classification was diagnosed in 80 patients, that of class C3 in 17, and that of class C4a in 1 patient. The procedure of RFA was performed by means of the VNUS device model RF62. The impact was exerted in an automatic mode, maintaining the catheter's temperature at 120° C during a 20-second treatment cycle for each 7 cm of the vein's length. In all cases, each 7-cm-long venous segment to be treated was acted upon 4 times. Forty-five patients after RFA underwent ultrasonographic monitoring performed first on POD 7 and then at 3, 6, 12 and 24 months. Recanalization of the trunk of the great saphenous vein (GSV) was registered in 3 (2.8%) cases at terms up to 3 months after the operation. In 2 cases recanalization turned out to be provoked by an incompetent perforant vein in the lower third of the femur. Seven (6.6%) patients with a large diameter of the great saphenous vein were found to develop post-closure hyperpigmentation which resolved spontaneously 8 months later. The remaining patients, with strict adherence to the indications for RFA, demonstrated complete obliteration of the vessel treated, with no recanalization observed ultrasonographically 10-12 months after the procedure. An additional experimental study with a morphological analysis confirmed appropriateness of carrying out four 20-second treatment cycles of RFA in each segment of the vein. A conclusion was made that RFA used in comprehensive surgical treatment for varicose veins of the lower limbs makes it possible to attain good therapeutic and cosmetic results that persist over time, if conducted in compliance with the mentioned fundamentally essential peculiarities of performing the procedure.

Effectiveness of atrial fibrillation rotor ablation is dependent on conduction velocity: An in-silico 3-dimensional modeling study

BACKGROUND

We previously reported that stable rotors are observed in in-silico human atrial fibrillation (AF) models, and are well represented by a dominant frequency (DF). In the current study, we hypothesized that the outcome of DF ablation is affected by conduction velocity (CV) conditions and examined this hypothesis using in-silico 3D-AF modeling.

METHODS

We integrated 3D CT images of left atrium obtained from 10 patients with persistent AF (80% male, 61.8±13.5 years old) into in-silico AF model. We compared AF maintenance durations (max 300s), spatiotemporal stabilities of DF, phase singularity (PS) number, life-span of PS, and AF termination or defragmentation rates after virtual DF ablation with 5 different CV conditions (0.2, 0.3, 0.4, 0.5, and 0.6m/s).

RESULTS

1. AF maintenance duration (p<0.001), spatiotemporal mean variance of DF (p<0.001), and the number of PS (p = 0.023) showed CV dependent bimodal patterns (highest at CV0.4m/s and lowest at CV0.6m/s) consistently. 2. After 10% highest DF ablation, AF defragmentation rates were the lowest at CV0.4m/s (37.8%), but highest at CV0.5 and 0.6m/s (all 100%, p<0.001). 3. In the episodes with AF termination or defragmentation followed by 10% highest DF ablation, baseline AF maintenance duration was shorter (p<0.001), spatiotemporal mean variance of DF was lower (p = 0.014), and the number of PS was lower (p = 0.004) than those with failed AF defragmentation after DF ablation.

CONCLUSION

Virtual ablation of DF, which may indicate AF driver, was more likely to terminate or defragment AF with spatiotemporally stable DF, but not likely to do so in long-lasting and sustained AF conditions, depending on CV.

First clinical experience of a dedicated irrigated-tip radiofrequency ablation catheter for the ablation of cavotricuspid isthmus-dependent atrial flutter

BACKGROUND

Different types of irrigated-tip ablation catheters are available for ablation of atrial flutter (AFL). The aim of this study was to compare an established with a novel dedicated Gold irrigated-tip catheter for ablation of AFL.

METHODS AND RESULTS

We compared consecutive patients undergoing ablation of AFL using a standard 3.5 mm irrigated-tip platinum-iridium (Pt-Ir) catheter (Thermocool, TC-group) and a 3.5 mm irrigated gold-tip catheter (Gold-group) specifically designed for cavotricuspid isthmus ablation (CTI). The primary endpoint was acute efficacy (net RF time) to achieve block across the CTI. Secondary endpoints included procedure time, fluoroscopy duration, complications, and recurrence of AFL.153 patients (age 68 ± 11 years, 74% male) were included. Net RF time to achieve CTI block was not different between the TC-group (793 ± 503 s) and the Gold-group (706 ± 422 s; p = 0.406). Total procedure time was not significantly different between the TC-group (70 ± 26 min) and the Gold-group (70 ± 27 min; p = 0.769). A significant difference between the groups was identified for the fluoroscopy duration (TC-group: 934 ± 537 s, Gold-group: 596 ± 362 s, p < 0.001). There were no major complications observed in the groups. Recurrence of AFL occurred in 3 of 66 (5%) in the TC-group and in 2 of 87 (2%) in the Gold-group (p = 0.652).

CONCLUSIONS

In conclusion, acute and chronic efficacy of the irrigated Pt-Ir and gold-tip catheters were comparable. However, the dedicated catheter design was associated with decreased fluoroscopy duration.

Stray energy transfer during endoscopy

INTRODUCTION

Endoscopy is the standard tool for the evaluation and treatment of gastrointestinal disorders. While the risk of complication is low, the use of energy devices can increase complications by 100-fold. The mechanism of increased injury and presence of stray energy is unknown. The purpose of the study was to determine if stray energy transfer occurs during endoscopy and if so, to define strategies to minimize the risk of energy complications.

METHODS AND PROCEDURES

A gastroscope was introduced into the stomach of an anesthetized pig. A monopolar generator delivered energy for 5 s to a snare without contacting tissue or the endoscope itself. The endoscope tip orientation, energy device type, power level, energy mode, and generator type were varied to mimic in vivo use. The primary outcome (stray current) was quantified as the change in tissue temperature (°C) from baseline at the tissue closest to the tip of the endoscope. Data were reported as mean ± standard deviation.

RESULTS

Using the 60 W coag mode while changing the orientation of the endoscope tip, tissue temperature increased by 12.1 ± 3.5 °C nearest the camera lens (p < 0.001 vs. all others), 2.1 ± 0.8 °C nearest the light lens, and 1.7 ± 0.4 °C nearest the working channel. Measuring temperature at the camera lens, reducing power to 30 W (9.5 ± 0.8 °C) and 15 W (8.0 ± 0.8 °C) decreased stray energy transfer (p = 0.04 and p = 0.002, respectively) as did utilizing the low-voltage cut mode (6.6 ± 0.5 °C, p < 0.001). An impedance-monitoring generator significantly decreased the energy transfer compared to a standard generator (1.5 ± 3.5 °C vs. 9.5 ± 0.8 °C, p < 0.001).

CONCLUSION

Stray energy is transferred within the endoscope during the activation of common energy devices. This could result in post-polypectomy syndrome, bleeding, or perforation outside of the endoscopist's view. Decreasing the power, utilizing low-voltage modes and/or an impedance-monitoring generator can decrease the risk of complication.

Reconstruction left atrium and isolation pulmonary veins of paroxysmal atrial fibrillation using single contact force catheter with zero x-ray exposure: A CONSORT Study

BACKGROUND

Conventional ablation of paroxysmal atrial fibrillation (PAF) is associated with radiation risks for patients and laboratory staff. Three-dimensional (3D) mapping system capable of showing contact force (CF) and direction of catheter tip may compensate for nonfluoroscopic safety issues.

OBJECTIVE

The aim of this study was to investigate the feasibility of zero x-ray exposure during reconstruction left atrium (LA) and ablation.

METHODS

Single, CF catheter, and 3D mapping system were used to reconstruct LA and isolate pulmonary veins (PV) in all patients. The patients were randomly divided into 2 groups after LA angiography. In group 1, reconstruction LA and isolation PV was performed with the help of 3D system (without x-ray), whereas in group 2, x-ray and 3D system were utilized to reconstruct LA and ablate PV antrum. After ablation, Lasso catheter was used to confirm the PV isolation. All patients were followed up to 12 months.

RESULTS

A total of 342 PAF patients were continuously enrolled. The basic clinical characteristics between the 2 groups had no significant difference. Parameters related to the procedure, average procedure time, ablation procedure time, average contact force (CF) applied, the percentage of time within CF settings, and average power applied during radiofrequency application showed no significant difference between the 2 groups. In group 1, the average fluoroscopy time before LA reconstruction was similar to that in group 2 (2.8 ± 0.4 vs. 2.4 ± 0.6 minutes, P = .75). The average fluoroscopy time during ablation was significantly lower than that in group 2 (0 vs. 7.6 ± 1.3 minutes, P < .001). The total x-ray exposure dose of the procedure in group 1 was significantly lower than that in group 2 (19.6 ± 9.4 vs. 128.7 ± 62.5 mGy, respectively, P < .001). Kaplan-Meier analysis indicated that there were no statistical differences in the probability of freedom from atrial arrhythmia (AF/AFL/AT) recurrence at 12 months between group 1 and group 2 (P = .152). The success rate after a single ablation procedure and without drugs (Class I/III AAD) at 12 months was not significantly different between the 2 groups (67.6%, 95% confidence interval [CI]: 62%-79.5% in group 1 and 68.9%, 95% CI: 63%-80.7% in group 2, P = .207). Procedural-related adverse events showed no significant different incidence between group 1 and group 2. A multivariate logistic regression analysis of risk factors was performed to evaluate the effectiveness outcome, which demonstrated that the percentage of CF (within the investigator-selected work ranges) during therapy was significantly associated with positive outcomes (odds ratio: 3.68; 95% CI: 1.65-10.6, P = .008), whereas the LA dimension was negatively associated with effectiveness outcomes (odds ratio: 0.72; 95% CI: 0.52-0.84, P = .016).

CONCLUSIONS

Reconstruction LA and isolation PV ablation using single CF-assisted catheter without x-ray exposure was both safe and effective. CF was positively associated with effective outcomes and LA dimensions negatively with effective ones.

Comparisons of Lesion Volumes and Shapes Produced by a Radiofrequency System with a Cooled, a Protruding, or a Monopolar Probe

BACKGROUND

Radiofrequency (RF) ablation for denervation has been utilized for decades in chronic pain management. This relies on the proper targeting of the affected nerve which may be obtained by creating an ablation lesion with a shape and volume that optimizes targeting. Various systems designed to improve lesion size are available. These include cooling the active tip (cooled-RF) and protruding the RF electrode outside the active tip (PERF).

OBJECTIVES

This study compares lesion volumes of 3 commercially available RF systems: cooled-RF, "V" shaped active cannula and protruding electrode (18 g and 20 g), and monopolar RF (MRF; 16 g, 18 g, and 20 g).

STUDY DESIGN

Ex vivo study using clinically relevant conditions.

SETTING

Biophysical laboratory in an academic institution.

METHODS

RF ablation lesions were generated in additive-free chicken breast specimens (n = 10) with the RF probes fully inserted in them. For cooled RF, a 17 g probe (4 mm active tip) was used. RF was applied for 150 seconds at 60°C. PERF was applied using 18 g or 20 g introducers (10 mm active tip) for either 90 or 150 seconds at 80°C. For MRF ablation, introducers diameter were 16 g, 18 g, or 20 g (10 mm active tip), while RF was applied for 90 seconds at 80°C. Tissues were dissected through the midpoint of the lesion, and measurements of the longitudinal, transversal, and depth lengths were taken and used to calculate the lesion volume. Measurements from the distal edge in the transverse and longitudinal directions were also recorded. One-way ANOVA was used to determine statistical significance between volume means (P < 0.05).

RESULTS

Mean lesion volume with cooled RF (595 mm3) is significantly larger than any other mean volume measured. The second largest volume is produced with MRF using a 16 g introducer (360 mm3), which is significantly larger than those obtained with 18 g or 20 g. This is also significantly larger than the one obtained with PERF using an 18 g introducer. Mean lesion volume produced with PERF (80°C for 90 seconds) and an 18 g diameter tip (215 mm3) is significantly larger than the respective one produced with MRF (169 mm3). Increasing lesioning time to 150 seconds significantly increases the volume (283 mm3). Using a 20 g tip produces the smallest lesions at 80°C for 90 seconds with either PERF or MRF, although a lesioning time of 150 seconds makes it significantly larger (207 mm3).

LIMITATIONS

The study is ex vivo and therefore does not account for the dynamic effects of the anatomy and physiology of a living organism.

CONCLUSIONS

The results indicate that the lesion produced with a cooled-RF system (17 g, 4 mm tip) is significantly larger than that produced with either of the other systems trialed (18 g or 20 g, 10 mm active tip protruding electrode or 16 g, 18 g, or 20 g monopolar electrode). Interestingly, a 16 g, 10 mm active tip monopolar electrode produced a larger lesion than the one produced with the 18 g protruding electrode. Key words: Radiofrequency, ablation, lesion shape, lesion size, cooled-RF, protruding electrode RF, monopolar RF.

The Extent of Mechanical Esophageal Deviation to Avoid Esophageal Heating During Catheter Ablation of Atrial Fibrillation

OBJECTIVES

This study sought to determine the extent of lateral esophageal displacement required during mechanical esophageal deviation (MED) and to eliminate luminal esophageal temperature elevation (LET_Elev) during pulmonary vein (PV) isolation.

BACKGROUND

MED is a conceptually attractive strategy of minimizing esophageal injury while allowing uninterrupted energy delivery along the posterior left atrium during PV isolation.

METHODS

MED was performed using a malleable metal stylet within a plastic tube placed within the esophagus. Barium was instilled to characterize the trailing esophageal edge. For each MED attempt, the MED_Effective, defined as the distance from the trailing esophageal edge-to-ablation line, was correlated to occurrences of LET_Elev.

RESULTS

In 114 consecutive patients/221 PV pairs undergoing MED (age 62.1 ± 11 years, 75% men, 62%/38% paroxysmal/persistent AF), esophageal stretching invariably occurred such that the esophageal edge trailed behind the plastic tube. MED_Effective distances of 0 mm to 10 mm, 10 mm to 15 mm, 15 mm to 20 mm or >20 mm were achieved in 60 (27.1%), 64 (29%), 48 (21.7%), and 49 (22.2%) attempts, respectively. Overall, LET elevation >38°C occurred in 81 of 221 (36.7%) PV pairs. The incidence of LET_Elev among the 4 groups was 73.3%, 35.9%, 25%, and 4.1%, respectively. MED_Effective distances were 9.1 ± 6.5 mm and 18 ± 7.6 mm in patients with and without LET_Elev, respectively (p < 0.0001). Three patients (2.6%) experienced clinically significant MED-related trauma, albeit only with a stiffer stylet.

CONCLUSIONS

Mechanical esophageal deviation >20 mm from the PV ablation line prevents significant esophageal heating during PV isolation, but this level of displacement was difficult to safely achieve with this off-the-shelf mechanical stylet approach.

Outcomes of Radiofrequency Ablation for Kidney Cancer

BACKGROUND

The incidence of small (< 4 cm) solid enhancing renal masses has been rising, and the majority (60% to 80%) of these tumors are renal cell carcinomas (RCCs) when pathologic analysis is performed. Needle ablation for small incidental renal masses is an attractive therapeutic option. Reasons include its decreased morbidity, shorter convalescence, and the ability to avert the higher risk of extirpative surgery in an aging patient population. Radiofrequency ablation (RFA) is a thoroughly studied needle ablative method used for RCC.

METHODS

The current published literature on renal tumor RFA was reviewed. The in vitro experiments, animal studies and clinical experience with RFA for treatment of small RCCs were analyzed and various controversies in renal RFA are presented for discussion.

RESULTS

Percutaneous and laparoscopic renal RFA can be safely performed and can eradicate small RCCs with cancer specific survival rates over 90% to 95% in many series. While long-term (5 years or greater) cancer control data are not yet available, these intermediate-term results are similar to those achieved with traditional nephron-sparing surgical options. However, the optimal method to perform RFA for renal masses is still evolving.

CONCLUSIONS

While long-term cancer control data are not yet available, the current literature suggests that RFA can effectively eradicate small RCCs. Further research is needed to elucidate the influence of various treatment variables, including impedance vs temperature-controlled RFA, sonographic vs computed tomographic guidance, general anesthetic vs conscious sedation, and radiologist vs urologist delivery of renal RFA.

[Study of Imitation Hardened Plaque RF Ablation with Different Frequencies]

In order to solve the heat transfer mechanism in radiofrequency treatment of atherosclerosis, we design two experimental structures to simulate the plaque, and use three frequencies and a variety of electrode arrangement, to study the heat transfer mechanism and heating capacity under the special structure. The results show that the temperature increment and heating area increase with increasing frequency. Under the structure in which the lipid particles are embedded in the fiber cap, using three electrodes with opposite polar arrangement between middle electrode and others, achieves effective heating to lipid pool in the plaque.

Medical Devices; Obstetrical and Gynecological Devices; Classification of the Closed Loop Hysteroscopic Insufflator With Cutter-Coagulator. Final order

The Food and Drug Administration (FDA, Agency, or we) is classifying the closed loop hysteroscopic insufflator with cutter-coagulator into class II (special controls). The special controls that will apply to the device are identified in this order, and will be part of the codified language for the closed loop hysteroscopic insufflator with cutter-coagulator classification. The Agency is classifying the device into class II (special controls) in order to provide a reasonable assurance of safety and effectiveness of the device.

Endoscopic ultrasound-guided radiofrequency ablation in gastroenterology: New horizons in search

Radiofrequency ablation (RFA) has been widely used for the treatment of various solid organ malignancies. Over the last decade, endosonographers have gradually shifted the application of RFA from porcine models to humans to treat a spectrum of diseases. RFA is performed in patients with pancreatic carcinoma who are not candidates for surgery. In this paper, we will discuss various indications for RFA, its procedural details and complications. At present, endoscopic ultrasound-guided RFA is gradually incorporated into the management of various diseases and opens a new avenue for disease treatment.