Novel contact force sensor incorporated in irrigated radiofrequency ablation catheter predicts lesion size and incidence of steam pop and thrombus

Optimal local impedance drops for an effective radiofrequency ablation during cavo-tricuspid isthmus ablation

PURPOSE

A novel ablation catheter capable of local impedance (LI) monitoring (IntellaNav MiFi OI, Boston Scientific) has been recently introduced to clinical practice. We aimed to determine the optimal LI drops for an effective radiofrequency ablation during cavo-tricuspid isthmus (CTI) ablation.

METHODS

This retrospective observational study enrolled 50 consecutive patients (68 ± 9 years; 34 males) who underwent a CTI ablation using the IntellaNav MiFi OI catheter, guided by Rhythmia. The LI at the start of radiofrequency applications (initial LI) and minimum LI during radiofrequency applications were evaluated. The absolute and percentage LI drops were defined as the difference between the initial and minimum LIs and 100× absolute LI drop/initial LI, respectively.

RESULTS

A total of 518 radiofrequency applications were analyzed. The absolute and percentage LI drops were significantly greater at effective ablation sites than ineffective sites (median, 15 ohms vs 8 ohms, P < .0001; median, 14.7% vs 8.3%, P < .0001). A receiver-operating characteristic analysis demonstrated that at optimal cutoffs of 12 ohms and 11.6% for the absolute and percentage LI drops, the sensitivity and specificity for predicting the effectiveness of the ablation were 66.5% and 88.2%, and 65.1% and 88.2%, respectively. Finally, bidirectional conduction block along the CTI was achieved in all patients.

CONCLUSIONS

During the LI-guided CTI ablation, the effective RF ablation sites exhibited significantly greater absolute and percentage LI drops than the ineffective RF ablation sites. Absolute and percentage LI drops of 12 ohms and 11.6% may be suitable targets for effective ablation.

Electrical Impedance Tomography for monitoring cardiac radiofrequency ablation: a scoping review of an emerging technology

Arrhythmias are common cardiac diseases which can be treated effectively by the cardiac radiofrequency ablation (CRFA). However, information regarding the lesion growth within the myocardium is critical to the procedure's safety and efficacy but still unavailable in the current catheterisation lab (CathLab). Over the last 20 years, many efforts have been made in order to track the lesion size during the procedure. Unfortunately, all the approaches have their own limitations preventing them from the clinical translation and hence making the lesion size monitoring during a CRFA still an open issue. Electrical Impedance Tomography (EIT) is an impedance imaging modality that might be able to image the thermal-related impedance changes from which the lesion size can be measured. With the availability of the patient's CT scans, for a detailed model, and the catheter-based electrodes for the internal electrodes, EIT accuracy and sensitivity to the ablated sites can be significantly improved and is worth being explored for this application. Though EIT is still new to CRFA with no in-vivo experiments being done according to our up-to-date searching, many related EIT studies and its extensive research in Hyperthermia and other ablations can reveal many hints for a possibility of the CRFA-EIT application. In this paper, we present a review on multiple aspects of EIT in CRFA. First, the expected CRFA-EIT signal range and frequency are discussed based on various measured impedance results obtained from lesions in the past. Second, the possible noise sources that can happen in a clinical CRFA procedure, along with their signal range and frequency compared to the CRFA-EIT signal, and, third, the available current solutions to separate such noises from the CRFA-EIT signal. Finally, we review the progress of EIT in thermal applications over the last two decades in order to identify the developments that EIT can take advantage of and the current drawbacks that need to be solved for a potential CRFA-EIT application.

Analysis of Contact Stability and Contact Safety of a Robotic Intravascular Cardiac Catheter under Blood Flow Disturbances

This paper studies the contact stability and contact safety of a robotic intravascular cardiac catheter under blood flow disturbances while in contact with tissue surface. A probabilistic blood flow disturbance model, where the blood flow drag forces on the catheter body are approximated using a quasi-static model, is introduced. Using this blood flow disturbance model, probabilistic contact stability and contact safety metrics, employing a sample based representation of the blood flow velocity distribution, are proposed. Finally, the contact stability and contact safety of a MRI-actuated robotic catheter are analyzed using these models in a specific example scenario under left pulmonary inferior vein (LIV) blood flow disturbances.

Impedance decrement indexes for avoiding steam-pop during bipolar radiofrequency ablation: An experimental study using a dual-bath preparation

INTRODUCTION

This experimental study was conducted to explore impedance monitoring for safely performing bipolar (BIP) radiofrequency (RF) ablation targeted to arrhythmia focus.

METHODS AND RESULTS

Using a newly designed dual-bath experimental model, contact-force-controlled (20-g) BIP ablation (50 W, 60 s) was attempted for porcine left ventricle (17.0 ± 2.7 mm thickness). BIP ablation was successfully accomplished for 60 s in 75 of the 89 RF applications (84.3%), whereas audible steam-pop occurred in the other 14 RF applications (15.7%). Receiver operating characteristic analysis demonstrated the optimal predictive values regarding the occurrence of steam-pop as follows; thinner myocardial wall (≤14.8 mm), low minimum impedance (≤89 ohm), greater total impedance decrement (TID) (≤ -25 ohm) and %TID (≤ -22.5%). Greater impedance decrement was not observed immediately preceding the occurrence of steam-pop but appeared around 15 s before. Four steam-pops happened before reaching the optimal predictive values of minimum impedance, whereas all 14 steam-pops developed 11.5 ± 9.2 and 8.1 ± 8.1 s after reaching the optimal predictive values of TID and %TID, respectively. Total lesion depth (endocardial plus epicardial) was 10.7 ± 1.2 mm on average, and was well correlated with TID and %TID. Transmural lesion through the myocardial wall was created in 22 RF applications.

CONCLUSION

Relatively thinner areas of the myocardium are likely to be at greater risk for steam-pop during BIP RF ablation. Lowering the RF application energy to reduce the impedance decrement may help to lessen this risk.

Spiral FBG sensors-based contact detection for confocal laser endomicroscopy

Endomicroscopy is an emerging non-invasive technique for real-time diagnosis of intraluminal malignancies. For accurate microscopic steering of the imaging probe in vivo, a miniature continuum manipulator has been developed to perform large-area optical biopsy. To keep images in focus, consistent contact with proper force and orientation between the imaging probe tip and the targeted tissue is required. This paper presents a spiral FBG sensors-based sensing method to simultaneously measure the force and torque exerted at the tip of the probe when contacting with the tissue. The embodiment consists of a tapered substrate with a hollow inner lumen for holding the imaging probe, and three optical fibres equally and spirally distributed on the outer surface of the substrate. Each fibre has two FBG sensors to detect small strain changes at two different cross-sections. The modelling process is explained in detail, and a learning-based measurement decoupling method is also provided. In vitro experiments are performed to collect cellular images with simultaneous force and torque sensing, demonstrating the practical value of the technique.

Catheter-integrated soft multilayer electronic arrays for multiplexed sensing and actuation during cardiac surgery

The rigidity and relatively primitive modes of operation of catheters equipped with sensing or actuation elements impede their conformal contact with soft-tissue surfaces, limit the scope of their uses, lengthen surgical times and increase the need for advanced surgical skills. Here, we report materials, device designs and fabrication approaches for integrating advanced electronic functionality with catheters for minimally invasive forms of cardiac surgery. By using multiphysics modelling, plastic heart models and Langendorff animal and human hearts, we show that soft electronic arrays in multilayer configurations on endocardial balloon catheters can establish conformal contact with curved tissue surfaces, support high-density spatiotemporal mapping of temperature, pressure and electrophysiological parameters and allow for programmable electrical stimulation, radiofrequency ablation and irreversible electroporation. Integrating multimodal and multiplexing capabilities into minimally invasive surgical instruments may improve surgical performance and patient outcomes.

Updated systematic review and meta-analysis of the impact of contact force sensing on the safety and efficacy of atrial fibrillation ablation: discrepancy between observational studies and randomized control trial data

Aims

Despite widespread adoption of contact force (CF) sensing technology in atrial fibrillation (AF) ablation, randomized data suggests lack of improvement in clinical outcomes. We aimed to assess the safety and efficacy of CF-guided vs. non CF-guided AF ablation.

Methods and results

Electronic databases were searched for randomized controlled trials (RCTs) and controlled observational studies (OS) comparing outcomes of AF ablation performed with vs. without CF guidance. The primary efficacy endpoint was freedom from AF at follow-up. The primary safety endpoint was major peri-procedural complications. Secondary endpoints included procedural, fluoroscopy, and ablation duration. Subgroup analyses were performed by AF type and study design. Nine RCTs (n = 903) and 26 OS (n = 8919) were included. Overall, CF guidance was associated with improved freedom from AF [relative risk (RR) 1.10; 95% confidence interval (CI) 1.02-1.18], and reduced total procedure duration [mean difference (MD) 15.33 min; 95% CI 6.98-23.68], ablation duration (MD 3.07 min; 95% CI 0.29-5.84), and fluoroscopy duration (MD 5.72 min; 95% CI 2.51-8.92). When restricted to RCTs however, CF guidance neither improved freedom from AF (RR 1.03; 95% CI 0.95-1.11), independent of AF type, nor did it reduce procedural, fluoroscopy, or ablation duration. Contact force guidance did not reduce the incidence of major peri-procedural complications (RR 0.89; 95% CI 0.64-1.24).

Conclusion

Meta-analysis of randomized data demonstrated that CF guidance does not improve the safety or efficacy of AF ablation, despite initial observational data showing dramatic improvement. Rigorous evaluation in randomized trials is needed before widespread adoption of new technologies.

Impedance, power, and current in radiofrequency ablation: Insights from technical, ex vivo, and clinical studies

BACKGROUND

Radiofrequency (RF) power is routinely considered during RF application. In contrast, impedance has been relatively poorly studied, despite also influencing RF lesion creation. The aim of this study was to examine the influence of electric impedance on RF lesion characteristics and on clinical RF ablation parameters.

METHODS AND RESULTS

In the first part of the study, power and impedance were systematically varied and the resulting current was calculated using custom-made software. In the second part of the study, ablation lesions (n = 40) were analyzed in a porcine ex vivo model. RF applications were delivered in cardiac muscle preparations with systematically varied values of electric impedance using a contact force ablation catheter. In the third part of the study, n = 3378 clinical RF applications were analyzed, power, impedance, and current data were exported and correlated with clinical patient data. 20 ± 3 W/80 Ω, 30 ± 3 W/120 Ω, 40 ± 3 W/160 Ω, and 50 ± 3 W/200 Ω RF applications resulted in 498 ± 40, 499 ± 26, 500 ± 20, and 500 ± 16 mA RF current, which were not significantly different (p = .32). Ablation lesions were significantly different in depth and diameter when applied with the same power but different impedances (p < .01); lesion sizes decreased when increasing impedance. In clinical data, a large range of delivered current (e.g., 39-40 W: 530-754 mA) was measured, due to variations in impedance.

CONCLUSIONS

RF lesion creation is determined by current rather than by power. During clinical RF ablation procedures, impedance significantly influences current delivery and varies considerably between patients. Impedance and current are clinically relevant parameters that should be considered during RF ablation.

Epicardial Ablation Biophysics and Novel Radiofrequency Energy Delivery Techniques

Important physiologic and anatomic differences exist between the epicardium and endocardium, particularly of the ventricles, and these differences affect ablation biophysics. Absence of passive convective effects conferred by circulating blood as well as the presence of epicardial fat and vessels and absence of intracavitary ridges and structures affect ablation lesion size when performing epicardial catheter-based ablation, whether using radiofrequency or cryothermal energy. Understanding differential effects in each environment is important in informing strategies to increase ablation lesion depth. When using actively cooled radiofrequency ablation, local impedance can be altered to selectively augment energy delivery.

Impact of catheter-tissue contact force on lesion size during right ventricular outflow tract ablation in a swine model

Background

The catheter-tissue contact force (CF) is one of the significant determinants of lesion size and thus has a considerable impact on the effectiveness of ablation procedures. This study aimed to evaluate the impact of CF on the lesion size during right ventricular outflow tract (RVOT) ablation in a swine model.

Methods

Twelve Guangxi Bama miniature male pigs weighing 40 to 50 kg were studied. After general anesthesia, a ThermoCool SmartTouch contact-sensing ablation catheter was introduced to the RVOT via the femoral vein under the guidance of the CARTO 3 system. The local ventricular voltage amplitude and impedance were measured using different CF levels. We randomly divided the animals into the following four groups according to the different CF levels: group A (3–9 g); group B (10–19 g); group C (20–29 g); and group D (30–39 g). Radiofrequency ablations were performed at three points in the free wall and septum of the RVOT in power control mode at 30 W for 30 s while maintaining the saline irrigation rate at 17 mL/min. At the end of the procedures, the maximum depth, surface diameter, and lesion volume were measured and recorded. A linear regression analysis was performed to determine the relationship between continuous variables.

Results

A total of 72 ablation lesions were created in the RVOT of the 12 Bama pigs. The maximum depth, surface diameter, and volume of the lesions measured were well correlated with the CF (free wall: β = 0.105, β = 0.162, β = 3.355, respectively, P < 0.001; septum: β = 0.093, β = 0.150, β = 3.712, respectively, P < 0.001). The regional ventricular bipolar voltage amplitude, unipolar voltage amplitude, and impedance were weakly positively associated with the CF (β = 0.065, β = 0.125, and β = 1.054, respectively, P < 0.001). There was a significant difference in the incidence of steam pops among groups A, B, C, and D (free wall: F = 7.3, P = 0.032; septum: F = 10.5, P = 0.009); and steam pops occurred only when the CF exceeded 20 g. Trans-mural lesions were observed when the CF exceeded 10 g in the free wall, while the lesions in the septum were non-trans-mural even though the CF reached 30 g.

Conclusions

CF seems to be a leading predictive factor for the size of formed lesions in RVOT ablation. Maintaining the CF value between 3 and 10 g may be reasonable and effective for creating the necessary lesion size and reducing the risk of complications, such as steam pops and perforations.

Role of pre-procedural CT imaging on catheter ablation in patients with atrial fibrillation: procedural outcomes and radiological exposure

BACKGROUND

Cardiac computed tomography (CT) is commonly used to study left atrial (LA) and pulmonary veins (PVs) anatomy before atrial fibrillation (AF) ablation. The aim of the study was to determine the impact of pre-procedural cardiac CT with 3D reconstruction on procedural outcomes and radiological exposure in patients who underwent radiofrequency catheter ablation (RFA) of AF.

METHODS

In this registry, 493 consecutive patients (age 62 ± 8 years, 70% male) with paroxysmal (316) or persistent (177) AF who underwent first procedure of RFA were included. A pre-procedural CT scan was obtained in 324 patients (CT group). Antral pulmonary vein isolation was performed in all patients using an open-irrigation-tip catheter with a 3D electroanatomical navigation system. Procedural outcome, including radiological exposure, and clinical outcomes were compared among patients who underwent RFA with (CT group) and without (no CT group) pre-procedural cardiac CT.

RESULTS

Acute PV isolation was obtained in all patients, with a comparable overall complication rate between CT and no CT group (4.3% vs 3%, p = 0.7). No differences were observed about mean duration of the procedure (231 ± 60 vs 233 ± 58 min, p = 0.7) and fluoroscopy time (13 ± 10 vs 13 ± 8 min, p = 0.6) among groups. Cumulative radiation dose resulted significantly higher in the CT group compared with no CT group (8.9 ± 24 vs 4.8 ± 15 mSv, P = 0.02). At 1 year, freedom from AF/atrial tachycardia were comparable among groups (CT group, 227/324 (70%), vs no CT group,119/169 (70%), p = ns).

CONCLUSIONS

Pre-procedural CT does not improve safety and efficacy of AF ablation, increasing significantly the cumulative radiological exposure.

Introducing a novel catheter-tissue contact feedback feature in robotic navigated catheter ablation: Utility, feasibility, and safety

Background

The quality of catheter–tissue contact is one of the most important determinants of catheter ablation (CA) success. The absence of catheter–tissue contact feedback has been regarded a major limitation of remote magnetic navigation (RMN)–guided CA. The e-Contact module (ECM) is a novel feature designed for RMN that measures the quality of catheter–tissue contact.

Objective

The purpose of this study was to describe the first clinical experience with this feature and to test its effect on procedural parameters and interference with other ablation equipment during CA procedures as well as its safety.

Methods

This was a prospective, single-center, 2-phase study investigating ECM use during complex RMN procedures in 30 patients. Impact of ECM on procedural parameters was evaluated in the feasibility phase (FP), and its interference with other equipment was tested in the interference phase (IP) using pacing maneuvers at 3 randomly selected right atrial sites. Intracardiac electrograms were evaluated for disturbances by 2 independent electrophysiologists.

Results

For FP, mean procedural time was 162 ± 66 minutes, fluoroscopy time 21 ± 9 minutes, and ablation time 34 ± 21 minutes. For IP, no significant differences in pacing capture or thresholds were found (ECM– vs ECM+: site 1: 2.05 vs 2.21 mA; P = .320; site 2: 2.15 vs 2.12 mA; P = .873; site 3: 2.51 vs 2.50 mA; P = .976). Electrogram disturbances did not significantly differ between ECM– and ECM+. No adverse events were reported.

Conclusion

The ECM is a novel catheter–tissue contact technology designed for RMN-guided CA. Our study suggests that this feature is feasible and does not interfere with other electrophysiology equipment while maintaining an excellent safety profile.

Intracardiac radiofrequency ablation in living swine guided by polarization-sensitive optical coherence tomography

SIGNIFICANCE

Pulmonary vein isolation with catheter-based radiofrequency ablation (RFA) is carried out frequently to treat atrial fibrillation. However, RFA lesion creation is only guided by indirect information (e.g., temperature, impedance, and contact force), which may result in poor lesion quality (e.g., nontransmural) and can lead to reoccurrence or complications.

AIM

The feasibility of guiding intracardiac RFA with an integrated polarization-sensitive optical coherence tomography (PSOCT)-RFA catheter in the right atria (RA) of living swine is demonstrated.

APPROACH

In total, 12 sparse lesions were created in the RA of three living swine using an integrated PSOCT-RFA catheter with standard ablation protocol. PSOCT images were displayed in real time to guide catheter-tissue apposition. After experiments, post-processed PSOCT images were analyzed to assess lesion quality and were compared with triphenyltetrazolium chloride (TTC) lesion quality analysis.

RESULTS

Five successful lesions identified with PSOCT images were all confirmed by TTC analysis. In two ablations, PSOCT imaging detected gas bubble formation, indicating overtreatment. Unsuccessful lesions observed with PSOCT imaging were confirmed by TTC analysis.

CONCLUSIONS

The results demonstrate that the PSOCT-RFA catheter provides real-time feedback to guide catheter-tissue apposition, monitor lesion quality, and possibly help avoid complications due to overtreatment, which may enable more effective and safer RFA treatment.

Continuous ablation improves lesion maturation compared with intermittent ablation strategies

BACKGROUND

Interrupted ablation is increasingly proposed as part of high-power short-duration radiofrequency ablation (RFA) strategies and may also result from loss of contact from respiratory patterns or cardiac motion. To study the extent that ablation interruption affects lesions.

METHODS

In ex vivo and in vivo experiments, lesion characteristics and tissue temperatures were compared between continuous (group 1) and interrupted (groups 2 and 3) RFA with equal total ablation duration and contact force. Extended duration ablation lesions were also characterized from 1 to 5 minutes.

RESULTS

In the ex vivo study, continuous RFA (group 1) produced larger total lesion volumes compared with each interrupted ablation lesion group (273.8 ± 36.5 vs 205.1 ± 34.2 vs 174.3 ± 32.3 mm³ , all P < .001). Peak temperatures for group 1 were higher at 3 and 5 mm than groups 2 and 3. In vivo, continuous ablation resulted in larger lesions, greater lesion depths, and higher tissue temperatures. Longer ablation durations created larger lesion volumes and increased lesion depths. However, after 3 minutes of ablation, the rate of lesion volume, and depth formation decreased.

CONCLUSIONS

Continuous RFA delivery resulted in larger and deeper lesions with higher tissue temperatures compared with interrupted ablation. This study may have implications for high-power short duration ablation strategies, motivates strategies to reduce variations in ablation delivery, and provides an upper limit for ablation duration beyond which power delivery has diminishing returns.

Rapid pacing and high-frequency jet ventilation additively improve catheter stability during atrial fibrillation ablation

INTRODUCTION

Catheter stability during atrial fibrillation ablation is associated with higher ablation success rates. Rapid cardiac pacing and high-frequency jet ventilation (HFJV) independently improve catheter stability. Simultaneous modulation of cardiac and respiratory motion has not been previously studied. The objective of this study was to determine the effect of simultaneous heart rate and respiratory rate modulation on catheter stability.

METHODS

Forty patients undergoing paroxysmal atrial fibrillation ablation received ablation lesions at 15 prespecified locations (12 left atria, 3 right atria). Patients were randomly assigned to undergo rapid atrial pacing for either the first or the second half of each lesion. Within each group, half of the patients received HFJV and the other half standard ventilation. Contact force and ablation data for all lesions were compared among the study groups. Standard deviation of contact force was the primary endpoint defined to examine contact force variability.

RESULTS

Lesions with no pacing and standard ventilation had the greatest contact force standard deviation (5.86 ± 3.08 g), compared to lesions with pacing and standard ventilation (5.45 ± 3.28 g; P < .01) or to lesions with no pacing and HFJV (4.92 ± 3.00 g; P < .01). Lesions with both pacing and HFJV had the greatest reduction in contact force standard deviation (4.35 ± 2.81 g; P < .01), confirming an additive benefit of each maneuver. Pacing and HFJV together was also associated with a reduction in the proportion of lesions with excessive maximum contact force (P < .001).

DISCUSSION

Rapid pacing and HFJV additively improve catheter stability. Simultaneous pacing with HFJV further improves catheter stability over pacing or HFJV alone to optimize ablation lesions.

A randomized trial of contact force in atrial flutter ablation

Aims

Contact force (CF) sensing has emerged as a tool to guide and improve outcomes for catheter ablation (CA) for cardiac arrhythmias. The clinical benefit on patient outcomes remains unknown. To study whether CF-guided CA for typical atrial flutter (AFL) is superior to CA not guided by CF.

Methods and results

In a double-blinded controlled superiority trial, we randomized patients 1:1 to receive CA for typical AFL guided by CF (intervention group) or blinded to CF (control group). In the intervention group, a specific value of the lesion size index (LSI), estimating ablation lesions size was targeted for each ablation lesion. Patients underwent electrophysiological study (EPS) after 3 months to assess occurrence of the primary endpoint of re-conduction across the cavo-tricuspid isthmus (CTI). We included 156 patients with typical AFL, median age was 68 [interquartile range (IQR) 61–74] years and 120 (77%) patients were male. At index procedure median LSI was higher in the intervention group [6.4 (IQR 5.1–7) vs. 5.6 (IQR 4.5–6.9), P &lt; 0.0001]. After 3 months, 126 patients (58 in intervention group) underwent EPS for primary endpoint assessment. Thirty (24%) patients had CTI re-conduction, distributed with 15 patients in each treatment group (P = 0.62). We observed no difference between treatment groups with regard to fluoroscopy, ablation, or procedure times, nor peri-procedural complications.

Conclusion

Contact force-guided ablation does not reduce re-conduction across the CTI after 3 months, nor does CF-guided ablation shorten fluoroscopy, ablation, or total procedure times.

The force stability of tissue contact and lesion size index during radiofrequency ablation: An ex-vivo study

INTRODUCTION

Radiofrequency (RF) ablation is a commonly used tool in the invasive electrophysiology laboratory to treat a variety of rhythm disorders. Reliable creation of transmural ablation lesions is crucial for long-term success. Lesion size index (LSI) is a multiparametric index that incorporates time, power, contact force (CF), and impedance data recorded during RF ablation in a weighted formula and has been shown to predict the extent of myocardial tissue lesions. Whether the force stability of contact influences lesion size in LSI-guided ablations is unknown.

OBJECTIVES

The aim of this study was to analyze the influence of the force stability of contact on lesion size during LSI-guided ablations in an ex-vivo model.

METHODS AND RESULTS

A total of 267 RF lesions (n = 6 hearts) were created on porcine myocardial slabs by using an open-tip irrigated ablation catheter with the following settings: 35 W with either intermittent (varied between 0 and up to 20 g), variable (10 to 20 g), or constant tissue contact (15 g) in a perpendicular or parallel fashion (applied manually) up to a target LSI of either 5 or 6. Subsequently, lesion width and depth were determined. Lesion width was mainly influenced by catheter tip orientation and LSI, whereas lesion depth was mainly influenced by LSI alone. The force stability of catheter contact had no relevant impact on lesion width or depth.

CONCLUSION

The force stability of catheter contact has only little effect on lesion depth or width in LSI-guided catheter ablation while the catheter orientation primarily affects lesion width.

Comparative study of strategies to prevent esophageal and periesophageal injury during atrial fibrillation ablation

OBJECTIVE

To compare the prevalence of esophageal and periesophageal thermal injury in patients undergoing radiofrequency (RF) atrial fibrillation (AF) ablation using 8 mm tip catheters during three different esophageal protection strategies.

METHODS

Forty-five consecutive patients with paroxysmal or persistent AF underwent first ablation procedure, besides esophagogastroduodenoscopy (EGD) combined with radial endosonography (EUS) performed before and after the pulmonary vein (PV) isolation. Before the procedure, patients were randomly assigned to one of three esophageal lesion protection strategies: group I-without any protective or monitoring dispositive and limiting RF applications to 30 W for 20 seconds, in left atrium posterior wall (LAPW); group II-power and time of RF delivery, up to 50 W for 20 seconds at LAPW, limited by esophageal temperature monitoring; group III-applications of RF in LAPW with fixed power application of 50 W for 20 seconds during continuous esophageal cooling.

RESULTS

Baseline characteristics of patients were similar in all groups. The four PVs were isolated in 14 (93.3%), 13 (86.7%), and 15 (100%) patients, respectively in groups I, II, and III. The mean RF power was significantly higher (P < .001) in the posterior side of PVs in group III. Post-AF ablation EGD and EUS revealed two esophageal wall ulcerations and two periesophageal mediastinal edemas only in the esophageal cooling group (P = .008).

CONCLUSION

Esophageal cooling balloon strategy resulted in a higher RF power energy delivery when ablating at the LA posterior wall, using 8 mm nonirrigated tip catheters under temperature mode control. Despite that, patients presented a relatively low incidence of esophageal and periesophaeal injuries.

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.

Quantitative analysis of ablation technique predicts arrhythmia recurrence following atrial fibrillation ablation

BACKGROUND

Optimal ablation technique, including catheter-tissue contact during atrial fibrillation (AF) radiofrequency (RF) ablation, is associated with improved procedural outcomes. We used a custom developed software to analyze high-frequency catheter position data to study the interaction between catheter excursion during lesion placement, lesion-set sequentiality, and arrhythmia recurrence.

METHODS

A total of 100 consecutive patients undergoing first-time RF ablation for paroxysmal AF were analyzed. Spatial positioning of the ablation catheter sampled at 60 Hz during RF application was extracted from the CARTO3 system (Biosense Webster Inc, USA) and analyzed using custom-developed MATLAB software to determine precise catheter spatial 3D excursion during RF ablation. The primary end point was freedom from atrial arrhythmia lasting longer than 30 seconds after a single ablation procedure.

RESULTS

At 1 year, 86% of patients were free from recurrent arrhythmia. There was no significant difference in clinical, echocardiographic, or ablation characteristics between patients with and without recurrent arrhythmia. Analyzing 15,356,998 position data points revealed that lesion-set sequentiality and mean lesion catheter excursion were predictors of arrhythmia recurrence. Analyzing arrhythmia recurrence by mean single-lesion catheter excursion (excursion >2.81 mm) and by sequentiality (using 46% of lesions with interlesion distance >6 mm as cutoff) revealed significantly increased arrhythmia recurrence in the higher excursion group (23% vs 6%, P = .03) and in the less sequential group (24% vs 4%, P = .02).

CONCLUSIONS

Ablation lesion sequentiality measured by catheter interlesion distance and catheter stability measured by catheter excursion during lesion placement are potentially modifiable factors affecting arrhythmia recurrence after RF ablation for AF.

Lesion Index Titration Using Contact-Force Technology Enables Safe and Effective Radiofrequency Lesion Creation at the Root of the Aorta and Pulmonary Artery

BACKGROUND

Ablation of some myocardial substrates requires catheter-based radiofrequency delivery at the root of a great artery. We studied the safety and efficacy parameters associated with catheter-based radiofrequency delivery at the root of the aorta and pulmonary artery.

METHODS

Thirty-six pigs underwent in-vivo catheter-based ablation under continuous contact-force and lesion index (power, contact-force, and time) monitoring during 60-s radiofrequency delivery with an open-irrigated tip catheter. Twenty-eight animals were allocated to groups receiving 40 W (n=9), 50 W (n=10), or 60 W (n=9) radiofrequency energy, and acute (n=22) and chronic (n=6) arterial wall damage was quantified by multiphoton microscopy in ex vivo samples. Adjacent myocardial lesions were quantified in parallel samples. The remaining 8 pigs were used to validate safety and efficacy parameters.

RESULTS

Acute collagen and elastin alterations were significantly associated with radiofrequency power, although chronic assessment revealed vascular wall recovery in lesions without steam pop. The main parameters associated with steam pops were median peak temperature >42°C and impedance falls >23 ohms. Unlike other parameters, lesion index values of 9.1 units (interquartile range, 8.7-9.8) were associated with the presence of adjacent myocardial lesions in both univariate ( P=0.03) and multivariate analyses ( P=0.049; odds ratio, 1.99; 95% CI, 1.02-3.98). In the validation group, lesion index values using 40 W over a range of contact-forces correlated with the size of radiofrequency lesions (R²=0.57; P=0.03), with no angiographic or histopathologic signs of coronary artery damage.

CONCLUSIONS

Lesion index values obtained during 40 W radiofrequency applications reliably monitor safe and effective lesion creation at the root of the great arteries.

Temperature-Controlled Radiofrequency Ablation Using Irrigated Catheters: Maximizing Ventricular Lesion Dimensions While Reducing Steam-Pop Formation

OBJECTIVES

The goal of this study was to examine the safety and efficacy of radiofrequency ablation (RFA) with irrigated catheters operated in a temperature-controlled mode for ventricular ablation.

BACKGROUND

Techniques to increase RFA dimensions are associated with higher risk for steam-pops. A novel irrigated catheter with circumferential thermocouples embedded in its ablation surface provides real-time surface temperature data. This study hypothesized that RFA operated in a temperature-controlled mode may allow maximizing lesion dimensions while reducing the occurrence of steam-pops.

METHODS

RFA with an irrigated catheter incorporating surface thermocouples was examined in 6 swine thigh muscle preparations and 15 beating ventricles at higher (50 W/60 s, T_max50^oC) and lower (50 W/60 s, T_max45^oC) temperature limits. Biophysical properties, lesion dimensions, and steam-pop occurrence were compared versus RFA with a standard catheter operated in power-control mode at higher (50 W/60 s) and lower (40W/60 s) power, and additionally at high power with half-normal saline (50 W/60 s).

RESULTS

In the thigh muscle preparation, lesion depth and width were similar between all groups (p = 0.90 and p = 0.17, respectively). Steam-pops were most frequent with power-controlled ablation at 50 W/60 s (82%) and least frequent with temperature-controlled ablation at 50 W/60 s, T_max45^oC (0%; p < 0.001). In the beating ventricle, lesion depth was comparable between all RFA settings (p = 0.09). Steam-pops were most frequent using power-controlled ablation at 50 W/60 s (37%) and least frequent with temperature-controlled ablation at 50 W/60 s, T_max45^oC (7%; p < 0.001). Half-normal saline had no incremental effect on lesion dimensions at 50 W in either the thigh muscle or the beating heart.

CONCLUSIONS

RFA using a novel irrigated catheter with surface thermocouples operated in a temperature-controlled mode can maximize lesion dimensions while reducing the risk for steam-pops.

Comparison of atrial fibrillation ablation efficacy using remote magnetic navigation vs. manual navigation with contact-force control

AIMS

This study aims to compare procedural parameters and clinical efficacy of remote magnetic navigation (RMN) vs. manual navigation (MAN) approach for radiofrequency ablation (RFA) in patients with atrial fibrillation (AF).

METHODS

146 patients with AF were enrolled in the study. In the RMN group (n=57), patients were treated with the CARTO® 3 in combination with the Niobe ES system. In the MAN group (n=89), ablation was performed with the EnSite Velocity and TactiCath™ Quartz catheter with direct contact force measurement. Procedural time, ablation time, fluoroscopy time, radiation dose and ablation counts were measured and compared between the groups. Recurrence of AF was evaluated after 6 months of follow-up.

RESULTS

Mean procedure times (236.87±64.31 vs. 147.22±45.19 min, P<0.05), counts of RF applications (74.30±24.77 vs. 49.15±20.33, P<0.05) and total RFA times (4323.39±1426.69 vs. 2780.53±1157.85 s, P<0.05) were all significantly higher in the RMN than in the MAN group, respectively. In the same order, mean X-ray dose (9722.6±7507.4 vs. 8087.9±6051.5 mGy/cm², P=0.12) and mean total X-ray exposure time (8.07±4.20 vs. 9.54±5.47 min, P=0.08) were not statistically different. At 6-month follow-up, freedom from AF was similar in RMN and MAN group for paroxysmal (60.8% and 73%, respectively, P=0.42) and persistent AF (69.6% and 75.0%, respectively, P=0.77).

CONCLUSIONS

Due to the fact that mid-term clinical outcomes showed no significant differences in AF recurrences between groups and manual ablation strategy provided more favorable results regarding acute procedural parameters, we can conclude that the remote magnetic navigation is not superior to the manual approach.

Role of Contact Force Sensing in Catheter Ablation of Cardiac Arrhythmias: Evolution or History Repeating Itself?

Adequate catheter-tissue contact facilitates efficient heat energy transfer to target tissue. Tissue contact is thus critical to achieving lesion transmurality and success of radiofrequency (RF) ablation procedures, a fact recognized more than 2 decades ago. The availability of real-time contact force (CF)-sensing catheters has reinvigorated the field of ablation biophysics and optimized lesion formation. The ability to measure and display CF came with the promise of dramatic improvement in safety and efficacy; however, CF quality was noted to have just as important an influence on lesion formation as absolute CF quantity. Multiple other factors have emerged as key elements influencing effective lesion formation, including catheter stability, lesion contiguity and continuity, lesion density, contact homogeneity across a line of ablation, spatiotemporal dynamics of contact governed by cardiac and respiratory motion, contact directionality, and anatomic wall thickness, in addition to traditional ablation indices of power and RF duration. There is greater appreciation of surrogate markers as a guide to lesion formation, such as impedance fall, loss of pace capture, and change in unipolar electrogram morphology. In contrast, other surrogates such as tactile feedback, catheter motion, and electrogram amplitude are notably poor predictors of actual contact and lesion formation. This review aims to contextualize the role of CF sensing in lesion formation with respect of the fundamental principles of biophysics of RF ablation and summarize the state-of-the-art evidence behind the role of CF in optimizing lesion formation.

Modular Optic Force Sensor for a Surgical Device Using a Fabry–Perot Interferometer

The ability to sense force in surgery is in high demand in many applications such asforce feedback in surgical robots and remote palpation (e.g., tumor detection in endoscopic surgery).In addition, recording and analyzing surgical data is of substantial value in terms of evidence-basedmedicine. However, force sensing in surgery remains challenging because of the specific requirementsof surgical instruments, namely, they must be small, bio-compatible, sterilizable, and tolerant tonoise. In this study, we propose a modular optic force sensor using a Fabry–Perot interferometer thatcan be used on surgical devices. The the proposed sensor can be implemented like a strain gauge,which is widely used in industrial applications but not compatible with surgery. The proposed sensorincludes two key elements, a fiber-optic pressure sensor using a Fabry–Perot interferometer thatwas previously developed by one of the authors and a structure that includes a carbide pin thatcontacts the pressure sensor along the long axis. These two elements are fixed in a guide channelfabricated in a 3 × 2 × 0.5 mm sensor housing. The experimental results are promising, revealinga linear relationship between the output and the applied load while showing a linear temperaturecharacteristic that suggests temperature compensation will be needed in use.

Endo/epicardial ablation of ventricular arrhythmias with contact force-sensing catheters in arrhythmogenic right ventricular dysplasia/cardiomyopathy

Objective:

To control ventricular arrhythmia in arrhythmogenic right ventricular dysplasia/cardiomyopathy (ARVD/C), ablation may be required both from the endocardial and epicardial side. In this study, we analyzed the results of contact force–sensing (CFS) catheters in the endo/epicardial ablation of ventricular arrhythmias in ARVD/C.

Methods:

We included 17 patients with ARVD/C, 5 of whom had premature ventricular contractions (PVC), and the rest of them were admitted with a ventricular tachycardia (VT) storm, between September 2014 and October 2016. We divided patients into two groups: the PVC and VT groups. Irrigated CFS catheters (Smart Touch, Biosense Webster, Inc.) were utilized in all procedures.

Results:

In the PVC group, the mean ratio of PVC during the 24-hour Holter monitoring was 31.8±7.6%. The mean contact force during mapping and ablation in the right ventricle was 13±1.2 and 12.8±1.9 grams, respectively. The mean follow-up duration was 15±3.1 months for the PVC group. The left ventricular ejection fraction improved in all patients (52.8±10%). All patients in the VT group underwent endo/epicardial ablation, except one. The mean contact force during the endocardium and epicardium mapping was 12.5±1.2 and 12.5±4.6 grams, respectively. The mean contact force during ablation for the endocardium and epicardium was 12.1±1.4 and 12.8±1.9 grams, respectively. All clinical and non-clinical VTs were ablated successfully, except in 2 patients who still had non-clinical VTs. The mean follow-up was 15.5±4.5 months. None of the VT patients experienced electrical storm or death. Two patients had single shock, and 1 patient had two shocks during the follow-up.

Conclusion:

Endo/epicardial ablation of ventricular arrhythmias with CFS catheters in ARVD/C seems to be promising.

Comparison Between Contact Force Monitoring and Unipolar Signal Modification as a Guide for Catheter Ablation of Atrial Fibrillation

Background:

Both contact force monitoring (CFM) and unipolar signal modification (USM) are guides for ablation, which improve the efficacy of pulmonary vein isolation of atrial fibrillation. We sought to compare the outcomes of atrial fibrillation ablation guided by CFM or USM.

Methods:

A total of 136 patients with paroxysmal atrial fibrillation underwent a circumferential pulmonary vein isolation using CF sensing ablation catheters and were randomly assigned to undergo catheter ablation guided by either CFM (CFM-guided group: n=70) or USM (USM-guided group: n=66). In the USM-guided group, each radiofrequency application lasted until the development of completely positive unipolar electrograms. In the CFM-guided group, a CF of 20 g (range, 10–30 g) and minimum force-time integral of 400 g were the targets for each radiofrequency application. The primary end point was freedom from any atrial tachyarrhythmia recurrence without antiarrhythmic drugs at 12-months of follow-up.

Results:

The cumulative freedom from recurrences at 12-months was 85% in the USM-guided group and 70% in the CFM-guided group ( P =0.031). The incidence of time-dependent and ATP-provoked early electrical reconnections between the left atrium and PVs, procedural time, fluoroscopic time, and average force-time integral, did not significantly differ between the 2 groups. The radiofrequency time for the pulmonary vein isolation was shorter in the USM-guided group than CFM-guided group but was not statistically significant ( P =0.077).

Conclusions:

USM was superior to CFM as an end point for radiofrequency energy deliveries during the pulmonary vein isolation in patients with paroxysmal atrial fibrillation in terms of the 12-month recurrence-free rate.

Clinical Trial Registration:

URL: https://www.umin.ac.jp/ctr/index.htm . Unique identifier: UMIN000021127.

Relationship between the ablation index, lesion formation, and incidence of steam pops

BACKGROUND

The ablation index (AI) is reported to be useful for a durable pulmonary vein isolation (PVI). However, there have been no studies investigating the relationship between the power, contact force (CF), AI, and steam pops.

METHODS

Using an in vitro model, ablation energy was delivered until a steam pop occurred and the time to the steam pop and AI when the steam pop occurred were measured. The experiment was performed with a combination of various powers (20, 30, 40, and 50 W) and contact forces (CFs) (10, 30, and 50 g) 20 times for each setting. The analysis consisted of two protocols. The first protocol was a comparison between the ablation power and several parameters under the same CF (10, 30, and 50 g). The second protocol was a comparison between the CF and several parameters under the same power (20, 30, 40, and 50 W). The correlation between the lesion formation and ablation parameters was evaluated.

RESULTS

The AI value when steam pops occurred varied depending on the ablation settings. All AI median values were <500 under an ablation power of 50 W. On other hand, the median ablation time up to the steam pop was more than 46 seconds, but all median values of the AI were more than 550 under an ablation with 20 W.

CONCLUSIONS

The AI cannot predict steam pops. A low power and long duration ablation could obtain a high AI value. However, high-power ablation could not obtain a high AI value because of an early occurrence of steam pops.

A Fiber Bragg Grating Sensing Structure for the Design, Simulation and Stress Strain Monitoring of Human Puncture Surgery

In order to improve the precision and stability of puncture surgical operations to assist doctors in completing fine manipulation, a new of type puncturing needle sensor is proposed based on a fiber Bragg grating (FBG). Compared with the traditional puncture needle sensor, the new type of puncturing needle sensor is able to sense not only the axial force, but also the torque force during the puncture process. A spoke-type structure is designed near the needle tip. In order to eliminate the influence of temperature and realize temperature compensation, a reference fiber method using three FBGs is applied. FBG1 and the reference FBG2 are pasted on the upper and lower surfaces of the new-type elastic beam, and FBG3 is pasted into the groove on the surface of the new type of puncturing needle cylinder. The difference of Bragg wavelength between FBG1 and the reference FBG2 is calibrated with the torque force, while the difference between the Bragg wavelength of the FBG3 and the reference FBG2 is calibrated with the axial force. Through simulation and sensing tests, when the torque force calibration range is 10 mN·m, the torque average sensitivity is 22.8 pm/mN·m, and the determination coefficient R2 is 0.99992, with a hysteresis error YH and repetition error YR of 0.03%FS and 0.81%FS, respectively. When the axial force calibration rang is 5 N, the axial force average sensitivity is 0.089 nm/N, and the determination coefficient R2 is 0.9997, with hysteresis error YH and repetition error YR of 0.014%FS and 0.11%FS, respectively. The axial force resolution and torque resolution of the new type of puncturing needle sensor are 0.03 N and 0.8 mN·m, respectively. The experimental data and simulation analysis show that the proposed new type of puncturing needle sensor has good practicability and versatility.

Electrogram voltage and pacing threshold before ablation, measured by mini-electrodes, predict parameters indicative of transmural lesions in the human atrium

PURPOSE

An important attenuation of the atrial signal recorded with mini-electrodes (ME) embedded in an 8-mm tip was associated with a transmural radiofrequency lesion. Our aim was to assess if parameters obtained from ME or conventional bipoles before applications predict successful atrial lesions.

METHODS

We prospectively included 33 consecutive patients undergoing cavotricuspid isthmus (CTI) ablation. Electrogram voltages and pacing thresholds were measured with ME and conventional bipoles before and after radiofrequency (RF) applications. The time before the loss of capture during applications was recorded. Lesions were considered successful, in accordance with preclinical data, if ME voltage decreased > 54%.

RESULTS

Of 207 applications, 107 could be analyzed. During applications, voltages decreased more in the ME than in the conventional bipoles (66.8 ± 26.1% vs 37.5 ± 42.5%, P = 0.001). Likewise, pacing threshold increased significantly more using the ME (86.3 ± 22.9% ME, 52.6 ± 35.6% conventional, P = 0.001). ME pre-ablation voltages were significantly higher and pacing thresholds significantly lower in successful lesions (voltage 0.88 ± 0.71 vs 0.26 ± 0.18 mV, P = 0.0001; threshold 1.6 ± 1.7 vs 2.8 ± 3.0, P = 0.04). Neither of these parameters with conventional bipoles nor time to loss of capture showed differences. A ME voltage > 0.33 mV and a pacing threshold < 1.5 mA predicted a successful lesion with 0.78 and 0.6 sensitivity and 0.78 and 0.59 specificity.

CONCLUSIONS

Certain pre-ablation parameters derived from ME such as electrogram voltage and pacing threshold differ from those obtained by a conventional configuration and can predict a successful atrial lesion.

Assessment of ablation catheter contact on valve annulus: Implications on accessory pathway ablation

Background

Catheter-tissue contact force is an important factor influencing lesion size and efficacy and thereby potential for arrhythmia recurrence following accessory pathway (AP) radiofrequency ablation. We aim to evaluate adequacy and perception of catheter contact on the tricuspid and mitral annuli.

Methods

Data were collected from 42 patients undergoing catheter ablation. Operators were blinded to contact force information and reported perceived contact (poor, moderate, or good) while positioning the catheter at four tricuspid annular sites (12, 9, 6 and 4 o'clock positions; abbreviated as TA12, TA9, TA6 and TA4) and three mitral annular sites (3, 5 and 7 o'clock positions; abbreviated as MA3, MA5 and MA7) through long vascular sheaths.

Results

The highest and lowest mean contact forces were obtained at MA7 (13.3 ± 1.7 g) and TA12 (3.6 g ± 1.3 g) respectively. Mean contact force on tricuspid annulus (6.1 g ± 0.9 g) was lower than mitral annulus (9.8 ± 0.9 g) locations (p = 0.0036), with greater proportion of sites with <10 g contact force (81.7% vs 60.4%; p = 0.0075). Perceived contact had no impact on measured mean contact force for both mitral and tricuspid annular positions (p = 0.959 and 0.671 respectively). There was correlation of both impedance and atrial electrogram amplitude with contact force, though insufficient to be clinically applicable.

Conclusion

A high proportion of annular catheter applications have low contact force despite being performed with long vascular sheaths in the hands of experienced operators. In addition, there was no impact of operator perceived contact force on actual measured contact force. This may carry implications for success of AP ablation.

•

The highest and lowest mean contact forces were obtained at posterolateral mitral and superior tricuspid annulus.

•

Mean contact force on tricuspid annulus was lower than mitral annulus locations (p=0.0036).

•

Perceived contact had no impact on measured mean contact force for both mitral and tricuspid annular positions.

•

There was some correlation of both impedance and atrial electrogram amplitude with contact force.

RESCUE-AF in Patients Undergoing Atrial Fibrillation Ablation: The RESCUE-AF Trial

BACKGROUND

Although contact force (CF)–sensing catheters improve procedural effectiveness and safety of atrial fibrillation ablation, recent reports documented a higher incidence of atrioesophageal fistula formation relative to ablation with non–CF-sensing catheters.The present study was to assess whether restricting CF to <20 g reduced risk for esophageal injury (EI) in patients with atrial fibrillation undergoing circumferential pulmonary vein isolation.

METHODS

This prospective, single-center, randomized study enrolled 89 consecutive patients (mean age, 57.2±11.3 years; 57.3% men) with atrial fibrillation (68.5% paroxysmal and 31.5% persistent). Computed tomography angiography, transesophageal echocardiography, and esophageal endoscopy were conducted before the procedure, and a repeat esophageal endoscopy was performed after the procedure. Patients were randomized to restricted-CF group (n=44) or non-CF group (n=45), with circumferential pulmonary vein isolation using a CF-sensing (CF restricted to <20 g) or non–CF-sensing catheter, respectively. The primary end point was rate of EI post ablation.

RESULTS

Baseline characteristics were evenly distributed between groups, without a case of preprocedural EI. With the same power setting, similar ablation time and average measured catheter tip temperature during posterior wall ablation just opposite to the esophagus in all patients in the restricted-CF group versus non-CF groups, there were no cases versus 9 (20%) cases of EI post ablation, respectively, with similar rate of freedom from atrial tachyarrhythmias at mean 31.3±6.5 months follow-up (68.2% versus 64.4%; P=0.3798).

CONCLUSIONS

Risk for EI was minimized when CF was restricted to <20 g at the posterior left atrial wall, where the circumferential pulmonary vein isolation lesion set and the course of the esophagus overlapped in all subjects.

Fatal esophageal-pericardial fistula as a complication of radiofrequency catheter ablation

The clinical role of catheter ablation using radiofrequency or cryothermal energy has become an important therapy in the management of patients with recurrent or persistent tachyarrhythmia that is refractory to medical therapy. It is regarded as a safe and reliable procedure and is performed routinely in health care facilities across the country. Like all procedures, there are associated risks and benefits. Development of an esophageal-atrial fistula is a rare but often-fatal complication of radiofrequency ablation. It is the second most frequent cause of death caused by the procedure, with mortality rates in excess of 70%. Death usually occurs as a result of cerebral or myocardial air embolism, endocarditis, massive gastrointestinal bleeding, and/or septic shock. Electrophysiologists have instituted a number of safeguard techniques to diminish the risk of developing esophageal-atrial fistula. Despite these measurements, instances of fistulous development still occur. Herein, we report a case of a 74-year-old male who presented with chest pain secondary to esophageal-pericardial fistula 19 days after pulmonary vein isolation using radiofrequency energy for atrial fibrillation in order to illustrate the clinical variability and diagnostic challenges associated with this dreaded gastrointestinal complication.

Haptic Telerobotic Cardiovascular Intervention: A Review of Approaches, Methods, and Future Perspectives

Cardiac diseases are recognized as the leading cause of mortality, hospitalization, and medical prescription globally. The gold standard for the treatment of coronary artery stenosis is the percutaneous cardiac intervention that is performed under live X-ray imaging. Substantial clinical evidence shows that the surgeon and staff are prone to serious health problems due to X-ray exposure and occupational hazards. Telerobotic vascular intervention systems with a master-slave architecture reduced the X-ray exposure and enhanced the clinical outcomes; however, the loss of haptic feedback during surgery has been the main limitation of such systems. This paper is a review of the state of the art for haptic telerobotic cardiovascular interventions. A survey on the literature published between 2000 and 2019 was performed. Results of the survey were screened based on their relevance to this paper. Also, the leading research disciplines were identified based on the results of the survey. Furthermore, different approaches for sensor-based and model-based haptic telerobotic cardiovascular intervention, haptic rendering and actuation, and the pertinent methods were critically reviewed and compared. In the end, the current limitations of the state of the art, unexplored research areas as well as the future perspective of the research on this technology were laid out.

The effect of contact force during radiofrequency catheter ablation using a vibrating catheter: New cooling method for catheter ablation

BACKGROUND

A new cooling method is proposed for preventing electrode-tissue overheating during cardiac catheter ablation using a vibrating catheter. Previous work has shown that vibration that results from increased flow velocity around the catheter can have a cooling effect on the electrode.

OBJECTIVE

Contact force has been shown to be an important factor that affects cooling and lesion formation, because contact force determines the ratio of power delivery between blood and tissue. In this study, the effect of contact force on electrode cooling and tissue heating was investigated during the operation of an electrode cooled by vibration.

METHODS

Using PVA-H or myocardium ablation tissue models under conditions of no flow, electrode and tissue temperatures and lesion sizes were measured at various vibrational frequencies and contact force conditions.

RESULTS

The experiments showed that the catheter vibration still decreases the electrode temperature over a contact force range of 2-30 gf. The lesion size was increased with increasing contact force at each vibrational frequency.

CONCLUSIONS

Increasing contact force can increase lesion size with cooling by vibration remaining effective.

Pathology Approaches to Determine Safety and Efficacy of Cardiac Ablation Catheters

Cardiac electrophysiology utilizes nonimplantable, catheter-based devices for diagnosis and treatment of arrhythmias as well as electroanatomical mapping of cardiac chambers. Gross pathology and histopathological assessments in preclinical studies play critical roles in determining the safety and efficacy of cardiac ablation systems used to treat tachyarrhythmias. The pathologist must assess ablation sites, adjacent structures and organs, and downstream organs to characterize the effects of the ablation treatment and determine whether adverse local reactions, collateral injury, or downstream thromboembolism are present. Histopathological assessment serves as an adjunct to electroanatomical data in determining efficacy in preclinical studies. Histopathology is the standard in definitively demonstrating transmurality of ablation lesions, which is necessary for complete conduction block, as well as showing the linear or circumferential distribution of a contiguous, transmural ablation lesion necessary for electroanatomical isolation of entire target structures such as pulmonary veins and the cavotricuspid isthmus, which are involved in propagating certain arrhythmias. This article will detail gross and histological methods for the pathology assessment of preclinical studies evaluating the safety and/or efficacy of cardiac ablation catheter systems as well as discuss correlation of pathology data with other supporting evidence for safety and efficacy such as acute, electroanatomical data.

Contact force and ablation assessment of surgical bipolar radiofrequency clamps in the treatment of atrial fibrillation

OBJECTIVES

Atrial fibrillation is treated surgically by creating conduction block lesions. Radiofrequency (RF) lesions have reduced efficacy compared to 'cut-and-sew'. Catheter ablation studies demonstrate a relationship between lesion depth and contact force. We hypothesized that contact force and lesion depth are dependent on design of the bipolar surgical RF clamps.

METHODS

Hinged and parallel jaw style RF clamps were studied. Muscle samples were clamped with pressure-sensitive film at increasing tissue thicknesses. Films were analysed determining clamp pressure profiles. A sheep model was utilized for ablation testing using each clamp style until the device indicated transmurality. Separate muscle areas had 1, 2 or 3 burns applied. The muscle was excised, sectioned every 1 cm and stained for lesion depth and fat thickness analysis.

RESULTS

Pressure profiling comparing the proximal and distal segments of each clamp style demonstrated only one statistically significant difference in the parallel clamp; the hinged clamp had statistically significant differences (P ≤ 0.03) for all tissue thicknesses. There was no evidence for differences in the proximal lesion depth of both clamps (P = 0.13) but deeper distally in the parallel clamp (10.17 mm vs 8.02 mm, P = 0.003). The logistic regression analysis demonstrated increased odds of transmurality with parallel clamps at 1, 2 or 3 burns (P = 0.03, P = 0.003 and P = 0.002). Every 1 mm increase in overlying fat decreased likelihood of transmurality by 11% (P < 0.05).

CONCLUSIONS

The parallel and hinged clamps have different pressure profiles with higher likelihood of transmurality using the parallel clamp. Fat reduces the ability of RF to deliver a transmural lesion. These findings have implications for optimal surgical RF ablation technique.