Catheter-tissue contact force for pulmonary veins isolation: a pilot multicentre study on effect on procedure and fluoroscopy time

Deep neuromuscular blockade during radiofrequency catheter ablation under general anesthesia reduces the prevalence of atrial fibrillation recurrence when compared to moderate neuromuscular blockade: A randomized controlled trial

BACKGROUND

Proper anesthesia management is required to maintain immobilization and stable breathing of the patient to improve catheter contact and stability during catheter ablation for PVI. However, it remains unclear whether the depth of neuromuscular blockade affects the results of RFCA under general anesthesia.

METHODS

The patients were randomly assigned to either the moderate neuromuscular blockade group (Group M, train-of-four 1 to 2) or the deep neuromuscular blockade group (Group D, posttetanic count 1-2). The primary outcome was the 12-month AF recurrence rate using confirmed electrocardiographic diagnosis after the ablation procedure at two different neuromuscular blockade depths.

RESULTS

Total 94 patients (47 in each group) were included in the analysis. Recurrence of AF during the A 12-month follow-up was 12 (25%) in group D and 22 (46%) in group M. The AF recurrence rate was significantly higher in group M (p =  0.03). The relative risk (RR) for the risk of 12-month AF recurrence was 0.545 in group D. AF symptom recurrence was observed during the A 12-month follow-up in 12 (25%) and 26 (54%) patients in groups D and M, respectively.

CONCLUSIONS

Compared to moderate neuromuscular blockade, deep neuromuscular blockade while performing RFCA under general anesthesia reduced 12-month AF recurrence rate. Deep neuromuscular blockade under general anesthesia is thought to increase the success rate by providing a stable surgical environment during the RFCA procedure.

TRIAL REGISTRATION

Clinical trials of Korea KCT 0003371.

Posterior wall substrate modification using optimized and contiguous lesions in patients with atrial fibrillation

BACKGROUND

Radiofrequency (RF) linear ablation at the left atrial (LA) roof and bottom to isolate the LA posterior wall using contiguous and optimized RF lesions was evaluated. Achieving isolation of the LA posterior wall is challenging as two continuous linear lesion sets are necessary.

METHODS

Forty consecutive patients with symptomatic atrial fibrillation (AF) and arrhythmia substrates affecting the LA posterior wall underwent posterior wall isolation by linear lesions across the roof and bottom. The cohort was divided into two groups: group 1 (20 patients) linear ablation guided by contact force (CF) only; group 2 (20 patients) guided by ablation index (AI) and interlesion distance.

RESULTS

Bidirectional block across the LA roof and bottom was achieved in 40/40 patients. Additional endocardial RF applications in 5 patients from group 1 vs. 3 patients from group 2 resulted in posterior wall isolation in all patients. Procedure duration was almost equal in both groups. CF and AI were significantly higher in group 2 for the roof line, whereas no statistical difference was found for the bottom line. AI-guided LA posterior wall isolation led to a significantly lower maximum temperature increase. The mean AI value as well as the mean value for catheter-to-tissue CF for the roof line were significantly higher when AI-guided ablation was performed. Standard deviation in group 2 showed a remarkably lower dispersion.

CONCLUSIONS

Ablation index guided posterior wall isolation for substrate modification is safe and effective. AI guided application of the posterior box lesion allows improved lesion formation.

When local impedance meets contact force: preliminary experience from the CHARISMA registry

PURPOSE

Highly localized impedance (LI) measurements during atrial fibrillation (AF) ablation have emerged as a viable real-time indicator of tissue characteristics and the consequent durability of the lesions created. We investigated the impact of catheter-tissue contact force (CF) on LI behavior during pulmonary vein isolation (PVI).

METHODS

Forty-five consecutive patients of the CHARISMA registry undergoing de novo AF radiofrequency (RF) catheter ablation with a novel open-irrigated-tip catheter endowed with CF and LI measurement capabilities (Stablepoint™ catheter, Boston Scientific) were included.

RESULTS

A total of 2895 point-by-point RF applications were analyzed (RF delivery time (DT) = 8.7±4s, CF = 13 ±±8 g, LI drop = 23 ±±7 Ω). All PVs were successfully isolated in an overall procedure time of 118 ±±34 min (fluoroscopy time = 13 ±±8 min). The magnitude of LI drop weakly correlated with CF (r = 0.13, 95% confidence interval (CI): 0.09 to 0.16, p < 0.0001), whereas both CF and LI drop inversely correlated with DT (r = -0.26, 95%CI: -0.29 to -0.22, p < 0.0001 for CF; r = -0.36, 95%CI: -0.39 to -0.33, p < 0.0001 for LI). For each 10 g of CF, LI drop markedly increased from 22.4 ± 7 Ω to 24.0 ± 8 Ω at 5 to 25 g CF intervals (5-14 g of CF vs 15-24 g of CF, p < 0.0001), whereas it showed smooth transition over 25 g (24.8 ± 7Ω at ≥ 25 g CF intervals, p = 0.0606 vs 15-24 g of CF). No major complications occurred during the procedures or within 30 days.

CONCLUSIONS

CF significantly affects LI drop and probable consequent lesion formation during RF PVI. The benefit of higher contact (> 25 g) between the catheter and the tissue appears to have less impact on LI drop.

TRIAL REGISTRATION

Catheter Ablation of Arrhythmias With High Density Mapping System in the Real World Practice (CHARISMA). URL: http://clinicaltrials.gov/ Identifier: NCT03793998.

In vivo Lesion Index (LSI) validation in percutaneous radiofrequency catheter ablation

INTRODUCTION

Lesion Index (LSI) has been developed to predict lesion efficacy during radiofrequency (RF) catheter ablation. However, its value in predicting lesions size has still to be established. The aim of our study was to assess the lesions size reproducibility for pre-specified values of LSI reached during RF delivery in an in vivo beating heart.

METHODS

Ablation lesions were created with different values of LSI in 7 domestic pigs by means of a contact force sensing catheter (TactiCath^TM , Abbott). Lesions were identified during RF delivery by means of a 3D mapping system (EnSite^TM Precision, Abbott) and measured after heart explantation. Histology was carried out after gross examination on the first 3 lesions to confirm the accuracy of the macroscopic evaluation.

RESULTS

A total of 64 myocardial lesions were created. Thirty-nine lesions were excluded from the analysis for the following reasons: histological confirmation of macroscopic lesion measurement (n=3), transmurality (n=24), unfavorable anatomic position (n=10), not macroscopically identifiable (n=2). In a final set of 25 non-transmural lesions, injury width and depth were respectively 4.6±0.6 mm and 2.6±0.8 mm for LSI=4, 7.3±0.8 mm and 4.7±0.6 mm for LSI=5, and 8.6±1.2 mm and 7.2±1.1 mm for LSI=6. A strong linear correlation was observed between LSI and lesion width (r=0.87, p<0.00001) and depth (r=0.89, p<0.00001). Multiple linear regression analysis identified LSI as the only ablation parameter that significantly predicted lesion width (p<0.001) and depth (p<0.001).

CONCLUSION

In our in vivo study, LSI proved highly predictive of lesion size and depth. This article is protected by copyright. All rights reserved.

Impact of cavotricuspid isthmus depth on the ablation index for successful first-pass typical atrial flutter ablation

Cavotricuspid isthmus (CTI) linear ablation has been established as the treatment for typical atrial flutter. Recently, ablation index (AI) has emerged as a novel marker for estimating ablation lesions. We investigated the relationship between CTI depth and ablation parameters on the procedural results of typical atrial flutter ablation. A total of 107 patients who underwent CTI ablation were retrospectively enrolled in this study. All patients underwent computed tomography before catheter ablation. From the receiver-operating curve, the best cut-off value of CTI depth was < 4.1 mm to predict first-pass success. Although the average AI was not different between deep CTI (DC; CTI depth ≥ 4.1) and shallow CTI (SC; CTI depth < 4.1), DC required a longer ablation time and showed a lower first-pass success rate (p < 0.01). In addition, the catheter inversion technique was more frequently required in the DC (p < 0.01). The lowest AI sites of the first-pass CTI line were determined in both the ventricular (2/3 segment of CTI) and inferior vena cava (IVC, 1/3 segment of CTI) sides. The best cut-off values of the weakest AIs at the ventricular and IVC sides for predicting first-pass success were > 420 and > 386, respectively. Among patients with these cut-off values, the first-pass success rate was 89% in the SC and 50% in the DC (p < 0.01). Although ablation parameters were not significantly different, the first-pass success rate was lower in the DC than in the SC. Further investigation might be required for better outcomes in deep CTIs.

Radiofrequency induced lesion characteristics according to force-time integral in experimental model

Contact force (CF)-sensing technology has enabled accurate real-time CF measurement in tissue. Average CF, which is quantified by the force–time integral (FTI), correlates with lesion volume. Little is known about which of the time and force factors that compose FTI plays a more important role and which is a better index for predicting lesion size, FTI, or force–power–time index (FPTI). Investigators sought to identify a better index for predicting radiofrequency ablation lesion formation with experimental model. Radiofrequency current was delivered to the swine skeletal muscle at radiofrequency energy current was delivered at 4 fixed power settings (15, 25, 30, and 40 W) for 6 variable time durations (5, 10, 20, 30, 40, and 50 s) with 6 variable CF settings (5, 10, 20, 30, 40, and 50 g). At each setting, the following parameters were evaluated: (1).. transmural lesion depth, (2).. lesion width, and (3).. lesion volume. Between FTI factors, the time factor was more important than the force factor for lesion formation. The area under the curve was greater for FPTI (0.943) than for FTI (0.870). On univariate linear regression analysis, the explanatory power of the linear regression model was better explained by FPTI (56.4%) than FTI (32.1%). Under the same FTI condition, the time factor had a greater effect on lesion formation. When power was included, the power factor had a greater effect on lesion formation and steam pop.

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.

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.

Development of an integrated optical contact force monitoring sensor for cardiac ablation catheters

Contact force monitoring technology during cardiac catheter ablation has become a major issue as both appropriate RF delivery and risk-free therapy have been more and more significant. In this study, an elastic waveguide was utilized to detect the contact force of 0 to 40 gF applied at the end of the sensor tip. The sensor showed a hysteresis between the force loading and releasing because of the elasticity of waveguide. The sensing responses were nearly linear and the sensitivity was about 0.2 mV/gF.

Contiguity Between Ablation Lesions and Strict Catheter Stability Settings Assessed by VISITAGTM Module Improve Clinical Outcomes of Paroxysmal Atrial Fibrillation Ablation - Results From the VISITALY Study

BACKGROUND

Our aim was to evaluate the clinical outcome of paroxysmal atrial fibrillation (AF) ablation with contact force technology, using an automated lesion tagging system (VISITAGTM module) with strict criteria of catheter stability.

METHODS AND RESULTS

We enrolled 200 consecutive patients who underwent pulmonary vein isolation (PVI) in 11 centers and were followed up for 12 months. The stability setting was within 3 mm for ≥10 s and for ≥15 s in 47% and 53% of patients, respectively. A mean of 67.2±21.9 VISITAGs was acquired. Freedom from atrial tachyarrhythmias at follow-up was 77.5% (155/200), and the contiguity between lesions was associated with a higher chronic success rate (96% vs. 77.1%; log-rank P=0.036). Radiofrequency (RF), fluoroscopy times, and recurrence rates at the 12-month follow-up were significantly lower than in a comparison group of 80 patients without VISITAGTM module (42.7±14.5 vs. 50.9±23.6 min; P=0.032; 11.6±7.8 vs. 18.4±12.8 min; P=0.003 and 22.5% vs. 41.2%; P=0.02). Two major complications (1 cardiac tamponade and 1 minor stroke) were observed only in the control group.

CONCLUSIONS

Paroxysmal AF ablation with contact force technology and strict criteria of stability using the VISITAG module was a safe procedure, associated with an improvement in efficiency and a reduction of atrial tachyarrhythmia recurrence at the 12-month follow-up compared with manual annotation. Contiguity between lesions seemed to enhance effectiveness outcomes.

Safety and efficacy of pulmonary vein isolation using a surround flow catheter with contact force measurement capabilities: A multicenter registry

INTRODUCTION

Pulmonary vein (PV) isolation is the cornerstone of catheter ablation in patients with atrial fibrillation (AF). Surround flow and contact force (CF) measurement capabilities might enhance procedure efficacy and safety. We report on the safety and midterm efficacy of a novel ablation catheter for PV isolation in patients with AF.

METHODS AND RESULTS

Two hundred thirty-three consecutive patients (57 ± 11 years, 76% males, 51% with structural heart disease), referred for paroxysmal (157) or persistent (76) AF, underwent PV isolation by a surround flow catheter with CF measurement capability in four centers. Ablation was guided by electroanatomic mapping allowing radiofrequency (RF) energy delivery in the antral region aiming at PV isolation. Mean overall procedure time was 100 ± 42 minutes with a mean fluoroscopy time of 6 ± 5 minutes. Mean ablation time was 31±15 minutes; 99% of the targeted veins were isolated. The mean CF value during ablation was 13 ± 4 g. Intraprocedural early (30 minutes) PV reconnection occurred in 12% PVs, and all PVs were effectively reisolated. One pericardial effusion and five groin hematomas were reported. During a mean follow-up of 12 ± 6 months, 30 (12.9%) (10% paroxysmal AF vs. 18% persistent AF, P = 0.07) patients had an atrial arrhythmias recurrence.

CONCLUSIONS

In this multicenter registry, RF ablation using a new surround flow catheter, with CF sensor, resulted as feasible, achieving a high rate of isolated PVs. Procedural and fluoroscopy times and success rates were comparable with other techniques with a low complication rate.

Accuracy of Voltage Signal Measurement During Radiofrequency Delivery Through the SMARTTOUCH Catheter

INTRODUCTION

Current methods for measuring voltage during radiofrequency (RF) ablation (RFA) necessitate turning off the ablation catheter. If voltage could be accurately read without signal attenuation during RFA, turning off the catheter would be unnecessary, allowing continuous ablation. We evaluated the accuracy of the Thermocool SMARTTOUCH catheter for measuring voltage while RF traverses the catheter.

METHODS AND RESULTS

We studied 26 patients undergoing RFA for arrhythmias. A 7.5F SMARTTOUCH catheter was used for sensing voltage and performing RFA. Data were collected from the Carto-3 3-dimensional mapping system. Voltages were measured during ablation (RF-ON) and immediately before or after ablation (RF-OFF). In evaluating the accuracy of RF-ON measurements, we utilized the RF-OFF measure as the gold standard. We measured 465 voltage signals. The median values were 0.2900 and 0.3100 for RF-ON and RF-OFF, respectively. Wilcoxon signed rank testing showed no significant difference in these values (P = 0.608). The intraclass correlation coefficient (ICC) was 0.96, indicating that voltage measurements were similarly accurate during RF-OFF versus RF-ON. Five patients had baseline atrial fibrillation (AF), for whom 82 ablation points were measured; 383 additional ablation points were measured for the remaining patients. The voltages measured during RF-ON versus RF-OFF were similar in the presence of AF (P = 0.800) versus non-AF rhythm (P = 0.456) (ICC, 0.96 for both).

CONCLUSION

Voltage signal measurement was similarly accurate during RF-ON versus RF-OFF independent of baseline rhythm. Physicians should consider not turning off the SMARTTOUCH ablation catheter when measuring voltage during RFA.

Advanced Mapping Systems To Guide Atrial Fibrillation Ablation: Electrical Information That Matters

Catheter ablation is an established and widespread treatment for atrial fibrillation (AF). Contemporary electroanatomical mapping systems (EAMs) have been developed to facilitate mapping processes but remain limited by spatiotemporal and processing restrictions. Advanced mapping systems emerged from the need to better understand and ablate complex AF substrate, by improving the acquisition and illustration of electrophysiological information. In this review, we present you the recently advanced mapping systems for AF ablation in comparison to the established contemporary EAMs.

Electroanatomic mapping systems (CARTO/EnSite NavX) vs. conventional mapping for ablation procedures in a training program

BACKGROUND

Three-dimensional electroanatomic mapping (EAM) systems reduce radiation exposure when radio frequency catheter ablation (RFCA) procedures are performed by well-trained senior operators. Given the steep learning curve associated with complex RFCA, trainees and their mentors must rely on multiple imaging modalities to maximize safety and success, which might increase procedure and fluoroscopy times. The objective of the present study is to determine if 3-D EAM (CARTO and ESI-NavX) improves procedural outcomes (fluoroscopy time, radio frequency time, procedure duration, complication, and success rates) during CA procedures as compared to fluoroscopically guided conventional mapping alone in an academic teaching hospital.

METHODS

We analyzed a total of 1070 consecutive RFCA procedures over an 8-year period for fluoroscopic time stratified by ablation target and mapping system. Multivariate logistic regression and adjusted odds ratios were calculated for each variable.

RESULTS

No statistically significant differences in acute success rates were noted between conventional and 3-D mapping cases [CARTO (p = 0.68) or ESI-NavX (p = 0.20)]. Moreover, complication rates were also not significantly different between CARTO (p = 0.23) and ESI-NavX (p = 0.53) when compared to conventional mapping. Procedure, radio frequency, and fluoroscopy times were significantly longer with CARTO and ESI-NavX versus conventional mapping [fluoroscopy time: CARTO, 28.3 min; ESI, 28.5 min; and conventional, 24.3 min; p < 0.001)].

CONCLUSIONS

The use of 3-D EAM systems during teaching cases significantly increases radiation exposure when compared with conventional mapping. These findings suggest a need to develop alternative training strategies that enhance confidence and safety during catheter manipulation and allow for reduced fluoroscopy and procedure times during RFCA.

Clinical significance of induced left atrial macro-reentrant tachycardia after pulmonary vein isolation

BACKGROUND

The clinical significance of induced left atrial macro-reentrant tachycardia (LA-AT) after encircling pulmonary vein isolation (EPVI) is unclear. Our objective was to determine whether induced LA-ATs are associated with the clinical recurrence of ATs.

METHODS

We studied 185 consecutive patients with paroxysmal atrial fibrillation (PAF) who underwent their first EPVI with an 8-mm tip, nonirrigated catheter approach. AT was induced by atrial burst pacing after the completion of EPVI, and the atrial activation pattern was evaluated using EnSite NavX. Induced LA-ATs were ablated only in patients with clinical ATs of suspected LA origin. The factors associated with occurrence of AT after the procedure were examined.

RESULTS

LA-ATs were induced in 38 patients and ablated in 5 patients. During a follow-up of 23 ± 7 months, the occurrence of AT did not differ between patients with nonablated LA-ATs (4/33, 12 %) and those without any inducible ATs (16/113, 14 %, p > 0.99). In multivariate analysis, the number of ablation points for completing EPVI was the only independent predictor of AT occurrence (odds ratio 1.07, p < 0.01). A repeat procedure was performed in 22 of 26 patients who developed AT. Nineteen patients became free from AT and AF after ablation of the conduction gaps (EPVI, n = 17; another line, n = 4), extra PV firing (n = 4), focal AT (n = 4), and induced LA-ATs (n = 3).

CONCLUSIONS

In patients who had EPVI for PAF using an 8-mm tip, nonirrigated catheter, the occurrence of AT after EPVI was mainly due to conduction gaps in the ablation line or extra PV triggers. In patients with PAF, LA-ATs induced during the first procedure did not require ablation if they were not associated with clinical AT.

Reduced residual conduction gaps and favourable outcome in contact force-guided circumferential pulmonary vein isolation

Aims

Although contact force (CF)-guided circumferential pulmonary vein isolation (CPVI) for paroxysmal atrial fibrillation (PAF) is useful, AF recurrence at long-term follow-up still remains to be resolved. The purpose of this study was to assess safety and efficacy of CF-guided CPVI and to compare residual conduction gaps during CPVI and long-term outcome between the conventional (non-CF-guided) and the CF-guided CPVI.

Methods and results

We studied the 50 consecutive PAF patients undergoing CPVI by a ThermoCool EZ Steer catheter (conventional group, mean age 61 ± 10 years) and the other 50 consecutive PAF patients by a ThermoCool SmartTouch catheter (CF group, 65 ± 11 years). The procedure parameters and residual conduction gaps during CPVI, and long-term outcome for 12 months were compared between the two groups. Circumferential pulmonary vein isolation was successfully accomplished without any major complications in both groups. Total procedure and total fluoroscopy times were both significantly shorter in the CF group than in the conventional group (160 ± 30 vs. 245 ± 61 min, P < 0.001, and 17 ± 8 vs. 54 ± 27 min, P < 0.001, respectively). Total number of residual conduction gaps was significantly less in the CF group than in the conventional group (2.7 ± 1.7 vs. 6.3 ± 2.7, P < 0.05). The AF recurrence-free rates after CPVI during 12-month follow-up were 96% (48/50) in the CF group and 82% (41/50) in the conventional group (P = 0.02 by log rank test). Multivariate Cox regression analysis further supported this finding.

Conclusion

Contact force-guided CPVI is safe and more effective in reducing not only the procedure time but also the AF recurrence than the conventional CPVI, possibly due to reduced residual conduction gaps during CPVI procedure.

The symbiosis of contact force catheter use for hybrid ablation for atrial fibrillation

OBJECTIVE

Reconduction across an ablation line is a common reason for arrhythmia recurrence over time. The hybrid procedure combines epicardial ablation of the pulmonary vein (PV) and creation of a box lesion with endocardial touch-ups for any electrical gaps. A high contact force (CF) between the ablation tip and cardiac tissue may increase the risk of thrombus formation, catheter tip charring, steam pop formation, and even cardiac perforation. CF monitoring is a significant new parameter for titration of the CF for creating an adequate lesion.

METHODS

Thirty-eight consecutive patients underwent epicardial ablation using bipolar radiofrequency devices. After checking electrical bidirectional block of the ablation lines, an endocardial CF catheter was used for further ablation (if needed) to complete the isolation of PVs, box lesion, cavotricuspid isthmus (CTI), and complex fractionated atrial electrograms (CFAE).

RESULTS

Endocardial touch-up was needed for 2 PVs (1.3 %) and 10 (26.3 %) box lesions. It was also used for the CTI line in 7 (18.4 %) patients, atrial tachycardia in 3 (7.9 %) patients, and additional CFAE ablation in 17 (44.7 %) patients. All 5 patients with arrhythmia recurrence had a mean CF < 10 g (p = 0.03). Procedure duration was significantly shorter in the CF group (223 ± 57 vs. 256 ± 60 min, p = 0.03) compared with control group.

CONCLUSION

Use of CF catheters is safe, feasible, and complementary to a hybrid procedure setup for atrial fibrillation ablation. Its real-time monitoring may predict future arrhythmia recurrence, and decrease procedure time.

EFFICAS II: optimization of catheter contact force improves outcome of pulmonary vein isolation for paroxysmal atrial fibrillation

Aims

A challenge of pulmonary vein isolation (PVI) in catheter ablation for paroxysmal atrial fibrillation (PAF) is electrical reconnection of the PV. EFFICAS I showed correlation between contact force (CF) parameters and PV durable isolation but no prospective evaluation was made. EFFICAS II was a multicentre study to prospectively assess the impact of CF guidance for an effective reduction of PVI gaps.

Methods and results

Pulmonary vein isolation using a radiofrequency (RF) ablation catheter with an integrated force sensor (TactiCath™) was performed in patients with PAF. Operators were provided EFFICAS I-based CF guidelines [target 20 g, range 10–30 g, minimum 400 g s force-time integral (FTI)]. Conduction gaps were assessed by remapping of PVs after 3 months, and gap rate was compared with EFFICAS I outcome. At follow up, 24 patients had 85% of PVs remaining isolated, compared with 72% in EFFICAS I (P = 0.037) in which CF guidelines were not used. The remaining 15% of gaps correlated to the number of catheter moves at creating the PVI line, quantified as Continuity Index. For PV lines with contiguous lesions and low catheter moves, durable isolation was 81% in EFFICAS I and 98% in EFFICAS II (P = 0.005). At index procedure, the number of lesions was reduced by 15% in EFFICAS II vs. EFFICAS I.

Conclusion

The use of CF with the above guidelines and contiguous deployment of RF lesions in EFFICAS II study resulted in more durable PVI in catheter ablation of PAF.

Contemporary Mapping Techniques of Complex Cardiac Arrhythmias - Identifying and Modifying the Arrhythmogenic Substrate

Cardiac electrophysiology has moved a long way forward during recent decades in the comprehension and treatment of complex cardiac arrhythmias. Contemporary electroanatomical mapping systems, along with state-of-the-art technology in the manufacture of electrophysiology catheters and cardiac imaging modalities, have significantly enriched our armamentarium, enabling the implementation of various mapping strategies and techniques in electrophysiology procedures. Beyond conventional mapping strategies, ablation of complex fractionated electrograms and rotor ablation in atrial fibrillation ablation procedures, the identification and modification of the underlying arrhythmogenic substrate has emerged as a strategy that leads to improved outcomes. Arrhythmogenic substrate modification also has a major role in ventricular tachycardia ablation procedures. Optimisation of contact between tissue and catheter and image integration are a further step forward to augment our precision and effectiveness. Hybridisation of existing technologies with a reasonable cost should be our goal over the next few years.

Radiation Dose is Significantly Reduced by Use of Contact Force Sensing Catheter During Circumferential Pulmonary Vein Isolation

The creation of a durable radiofrequency (RF) lesion depends on several parameters, including catheter tip electrode size and composition, tip orientation, temperature, RF pulse duration, power, blood flow, and catheter to tissue contact. The development of new contact force (CF) sensor catheters has allowed the measurement of the tip to tissue CF during the RF ablation procedure. Here, we describe the clinical experience obtained using CF catheters for atrial fibrillation ablation, with a specific focus on the impact of CF technology on acute procedural data (procedure and fluoroscopy time).

Atrial fibrillation ablation in the era of cryoballoon and force-sensing catheters: freeze or burn?

OPINION STATEMENT

Atrial fibrillation can adversely affect the quality of life for many patients. Though antiarrhythmic drug therapy remains an option for the treatment of atrial fibrillation, the drugs are associated with numerous side effects. Atrial fibrillation ablation has been shown to be as efficacious as antiarrhythmic drug therapy. The field of atrial fibrillation ablations has evolved over time from utilizing radiofrequency energy to using cryoenergy. Newer technologies are being developed with efforts to improve outcomes in patients undergoing atrial fibrillation ablations. This article will highlight two such technologies: cryoballoon ablation catheters and contact force-sensing catheters. These novel catheters appear to be further revolutionizing this young field in electrophysiology.

In vivo contact force measurements and correlation with left atrial anatomy during catheter ablation of atrial fibrillation

AIMS

Lesion formation during catheter ablation crucially depends on catheter-tissue contact. We sought to evaluate the impact of anatomical characteristics of the left atrium (LA) and the pulmonary veins (PVs) on contact force (CF) measurements.

METHODS AND RESULTS

An anatomical map of the LA was obtained in 25 patients prior to catheter ablation of atrial fibrillation. Contact force (operator blinded) and local bipolar electrogram amplitudes (EGM) were measured in eight pre-defined segments around the PVs. After unblinding, points with low CF (≤5 g) were corrected to CF >5 g, and the distance between points was measured. In a pre-procedural computed tomography of the heart, LA volume as well as sizes and circumferences of the PV ostia were measured and correlated to CF measurements. Four hundred and twenty-six points in eight pre-defined LA locations were assessed. Low CF (<5 g) was found in 25.0% (43.5%) of points superior, 33.3% (66.7%) anterior, 32.1% (44.4%) inferior, and 15.5% (15.9%) posterior to the right (left) PVs. The mean distance after correction was 5.8 ± 3.4 mm. Local bipolar electrogram amplitudes between low- and high-CF points did not differ (1.21 ± 1.54 vs. 1.13 ± 1.3 mV, P = ns). The mean CF at the left PVs was significantly lower than at the right PVs (7.91 ± 3.74 vs. 13.95 ± 6.34 g, P < 0.001), with the lowest CF anterior to the left PVs (5.2 ± 3.6 g). Contact force measurements did not correlate to LA volume, size, and circumference of the PVs.

CONCLUSION

Contact force during LA mapping significantly differs according to the location within the LA. These differences are independent of LA volume and anatomy of the PV ostia.

Catheter Ablation of Atrial Fibrillation Without Radiation Exposure Using A 3D Mapping System

Transcatheter ablation procedures have been traditionally performed under fluoroscopic guidance. However, x-ray exposure is afflicted by the risk of developing malignancies as well as other deterministic effects of radiation. For this reason, radiation doses in the interventional laboratory should be reduced "As Low As Reasonably Achievable", with respect to the safety of the patients and the medical staff. This is of utmost importance in atrial fibrillation (AF) ablations, which are usually lengthy procedures. With the improvement of technology, the development of additional imaging tools and the widespread of 3D electroanatomic mapping systems (EAM), near-zero fluoroscopy AF ablation procedure is becoming a reality, limiting fluoroscopy use mainly to guide transseptal puncture. In the present paper we reviewed the risks to health related to x-ray exposure and we discussed the current state of knowledge of catheter ablation of AF without fluoroscopy in the 3D EAM system era.

Relationship between contact force sensing technology and medium-term outcome of atrial fibrillation ablation: a multicenter study of 600 patients

INTRODUCTION

Contact force sensing (CFS) technology improves acute pulmonary vein isolation durability; however, its impact on the clinical outcome of ablating atrial fibrillation (AF) is unknown.

METHODS AND RESULTS

First time AF ablation procedures employing CFS from 4 centers were matched retrospectively to those without CFS in a 1:2 manner by type of AF. Freedom from atrial tachyarrhythmia was defined as the primary outcome measure, and fluoroscopy time the secondary outcome measure. Nineteen possible explanatory variables were tested in addition to CFS. A total of 600 AF ablation procedures (200 using CFS and 400 using non-CFS catheters) performed between 2010 and 2012 (46% paroxysmal, 36% persistent, 18% long-lasting persistent) were analyzed. The mean follow-up duration was 11.4 ± 4.7 months-paroxysmal AF 11.2 ± 4.1 CFS versus 11.3 ± 3.9 non-CFS (P = 0.745)-nonparoxysmal AF 10.4 ± 4.5 CFS versus 11.9 ± 5.4 non-CFS (P = 0.015). The use of a CFS catheter independently predicted clinical success in ablating paroxysmal AF (HR 2.24 [95% CIs 1.29-3.90]; P = 0.004), but not nonparoxysmal AF (HR 0.73 [0.41-1.30]; P = 0.289) in a multivariate analysis that included follow-up duration. Among all cases, the use of CFS catheters was associated with reduced fluoroscopy time in multivariate analysis (reduction by 7.7 [5.0-10.5] minutes; P < 0.001). Complication rates were similar in both groups.

CONCLUSIONS

At medium-term follow-up, CFS catheter technology is associated with significantly improved outcome of first time catheter ablation of paroxysmal AF, but not nonparoxysmal AF. Fluoroscopy time was lower when CFS technology was employed in all types of AF ablation procedures.

Contact force mapping and voltage thresholds during high-frequency stimulation of human cardiac ganglionated plexuses†

AIMS

The intrinsic cardiac nervous system consists of ganglionated plexuses (GPs) localized epicardially to specific regions of the left atrium (LA). The relation between voltage thresholds and endocardial contact force associated with autonomic effects during stimulation of GPs has not previously been evaluated.

METHODS AND RESULTS

Sixteen patients with symptomatic atrial fibrillation (AF) underwent mapping of GPs prior to radiofrequency ablation of AF. Pre-acquired computed tomographic images were merged with 3D non-fluoroscopic electroanatomic mapping of the LA. Using high-frequency stimulation (HFS), the voltage thresholds of GPs was obtained while patients received conscious sedation. At each location, the contact force measurement from the catheter was correlated with the voltage applied during HFS at 5, 10, or 15 V to obtain an autonomic effect, usually associated with asystole, or marked bradycardia. There were 192 applications of HFS, resulting in GP identification in all patients (mean 3.4 per patient, range 1-5). During HFS, an autonomic response was significantly more likely to occur at 10 V as compared with 5 V (P < 0.008). There was no significant relation between the measured contact force and the likelihood of obtaining an autonomic response. When performing HFS at 15 V, a sudden overshoot with maximal values of contact force of up to 100 g was also observed. High-frequency stimulation was well tolerated, without associated adverse events.

CONCLUSION

An autonomic response during HFS was significantly more likely to occur at 10 V as compared with 5 V. Although the GPs are epicardial structures, significant contact force was not required for their localization.

Electroanatomical mapping of atrial fibrillation: Review of the current techniques and advances

The number of atrial fibrillation (AF) catheter ablations performed annually has been increasing exponentially in the western countries in the last few years. This is clearly related to technological advancements, which have greatly contributed to the improvements in catheter ablation of AF. In particular, state-of-the-art electroanatomical mapping systems have greatly facilitated mapping processes and have enabled complex AF ablation strategies. In this review, we outline contemporary and upcoming electroanatomical key technologies focusing on new mapping tools and strategies in the context of AF catheter ablation.

Catheter-tissue contact force values do not impact mid-term clinical outcome following pulmonary vein isolation in patients with paroxysmal atrial fibrillation

PURPOSE

Catheter-tissue contact is critical for effective lesion creation in radiofrequency catheter ablation (RFCA). In a multicenter prospective study, we assessed the relationship between catheter contact force (CF) during RFCA for paroxysmal atrial fibrillation (AF) and clinical recurrences over a mid-term follow-up.

METHODS

All patients underwent RFCA for paroxysmal AF by antral pulmonary vein (PV) isolation, aiming at entry and exit conduction block in all PVs. A new open-irrigated tip catheter with CF sensing (SmartTouch(TM), Biosense Webster Inc. CA) was used. All patients were followed for at least 12 months and the relationship between CF and clinical outcomes assessed.

RESULTS

One year follow-up was available in 92/95 of the patients enrolled. Acute PV isolation was achieved in 100 % of the veins. Mean CF during RFCA was 12.2 ± 3.9 g. Mean force-time integral (FTI) was 733 ± 505 gs. Following the 3-month blanking period, 17 (18 %) patients experienced at least 1 atrial tachyarrhythmia relapse. There was no statistical difference in mean CF (13 ± 3.4 g vs 12 ± 4 g, p = 0.32) and mean FTI (713 ± 487 gs vs 822 ± 590 gs, p = 0.42) between patients with and without arrhythmia recurrences. Recurrences were recorded in 22 % of patients achieving a mean FTI value below the median of 544 gs and in 15 % of patients with a mean FTI value above the median (p = 0.64).

CONCLUSIONS

RFCA with CF data during PV isolation for paroxysmal AF improves physician's knowledge on catheter-tissue contact. In the present dataset, however, higher CF values did not impact mid-term clinical RFCA outcome.

Higher contact-force values associated with better mid-term outcome of paroxysmal atrial fibrillation ablation using the SmartTouch™ catheter

AIMS

Real-time measurement of contact force (CF) during catheter ablation of atrial fibrillation (AF) has been recently suggested to potentially impact procedural outcome. However, the role of CF intensity on mid-term results using the SmartTouch™ catheter has not been investigated so far.

METHODS AND RESULTS

Pulmonary vein isolation (PVI) using the SmartTouch™ catheter was performed in 100 eligible patients (age 62 ± 8; 79% men) undergoing a first procedure of paroxysmal AF catheter ablation. Continuous CF monitoring during catheter ablation allowed calculation of mean CF per patient. Patients were dichotomized into high CF (≥22 g, upper quartile) and low CF (<22 g, remaining) and enroled in a standardized follow-up programme (after a 3-month blanking period), free from antiarrhythmic therapy, with regular evaluations including 24 h Holter recordings at 1, 3, 6, 9, 12, 18, and 24 months. Atrial fibrillation relapse was defined as any symptomatic or asymptomatic atrial arrhythmia lasting >30 s. The average CF among all procedures was 19.6 ± 3.7 g. Though complete PVI was eventually achieved in all cases in both groups, success using an exclusively anatomical approach was higher in the high CF group (92.0 vs. 72.0%; P = 0.04). During a mean follow-up of 19 ± 5 months, a lower incidence of AF relapse was observed in higher CF patients (4.0 vs. 20.0%; log rank P = 0.04). Pericardial tamponade occurred in one patient in the higher CF group. No thromboembolism or procedure-associated deaths were observed.

CONCLUSION

Higher values of CF overall during antral PVI appear to be associated with a higher likelihood of sinus rhythm maintenance without significantly increasing the complication rate.

The benefit of tissue contact monitoring with an electrical coupling index during ablation of typical atrial flutter--a prospective randomised control trial

INTRODUCTION

We sought to investigate the use of tissue contact monitoring by means of the electrical coupling index (ECI) in a prospective randomised control trial of patients undergoing cavotricuspid isthmus (CTI) ablation for atrial flutter.

METHODS

Patients with ECG-documented typical flutter undergoing their first CTI ablation were randomised to ECI™-guided or non-ECI™-guided ablation. An irrigated-tip ablation catheter was used in all cases. Consecutive 50-W, 60-s radiofrequency lesions were applied to the CTI, from the tricuspid valve to inferior vena cava, with no catheter movement permitted during radiofrequency (RF) delivery. The ablation endpoint was durable CTI block at 20 min post-ablation. Patients underwent routine clinic follow-up post-operatively.

RESULTS

A total of 101 patients (79 male), mean age 66 (+/-11), 50 ECI-guided and 51 control cases were enrolled in the study. CTI block was achieved in all. There were no acute complications. All patients were alive at follow-up. CTI block was achieved in a single pass in 36 ECI-guided and 30 control cases (p = 0.16), and at 20 min post-ablation, re-conduction was seen in 5 and 12 cases, respectively (p = 0.07). There was no significant difference in total procedure time (62.7 ± 33 vs. 62.3 ± 33 min, p = 0.92), RF requirement (580 ± 312 vs. 574 ± 287 s, p = 0.11) or fluoroscopy time (718 ± 577 vs. 721 ± 583 s, p = 0.78). After 6 ± 4 months, recurrence of flutter had occurred in 1 (2 %) ECI vs. 8 (16 %) control cases (OR 0.13, 95 % CI 0.01-1.08, p = 0.06).

CONCLUSIONS

ECI-guided CTI ablation demonstrated a non-statistically significant reduction in late recurrence of atrial flutter, at no cost to procedural time, radiation exposure or RF requirement.

Contact-force guided radiofrequency vs. second-generation balloon cryotherapy for pulmonary vein isolation in patients with paroxysmal atrial fibrillation-a prospective evaluation

AIMS

In the setting of paroxysmal atrial fibrillation (AF), there are no available data comparing the mid-term outcome of patients undergoing pulmonary vein isolation (PVI) catheter ablation using contact-force (CF)-guided radiofrequency (RF) vs. second-generation balloon cryotherapy.

METHODS AND RESULTS

Prospective single-centre evaluation, carried out from March 2011 to February 2013, comparing CF radiofrequency (Thermocool(®) SmartTouch™, Biosense Webster, Inc.) (CF group) with cryoballoon ablation (Arctic Front Advance™ 28 mm cryoballoon, Medtronic, Inc.) (CB group), in regards to procedural safety and efficacy, as well as recurrence at 12 months. Overall, 150 consecutive patients were enrolled (75 in each group). The characteristics of patients of both the groups were similar (61.2 ± 9.9 years, women 25.3%, mean AF duration 4.1 ± 4.0 years, mean CHA2DS2-VASc score 1.4 ± 1.3, mean HAS-BLED 1.4 ± 0.6). Duration of the procedure was significantly lower in the CF group (110.7 ± 32.5 vs. 134.5 ± 48.3 min, P = 0.001), with a lower duration of fluoroscopy (21.5 ± 8.5 vs. 25.3 ± 9.9 min, P = 0.017) and X-ray exposure (4748 ± 2411 cGy cm² vs. 7734 ± 5361 cGy cm², P = 0.001). In contrast, no significant difference was found regarding significant procedural complication (2.7 vs. 1.3% in CF and CB groups, respectively; P = 0.56), and PVI was eventually achieved in all cases. At 12 months, AF recurrence occurred in 11 patients (14.7%) in the CB group and in 9 patients (12.0%) in the CF group (HR = 1.20 95% CI 0.50-2.90; log rank P = 0.682).

CONCLUSIONS

Our preliminary findings suggest that CF-guided radiofrequency and cryotherapy present very similar performances in the setting of paroxysmal AF catheter ablation.

Improvements In AF Ablation Outcome Will Be Based More On Technological Advancement Versus Mechanistic Understanding

Atrial fibrillation (AF) is one of the most common cardiac arrhythmias. Catheter ablation has proven more effective than antiarrhythmic drugs in preventing clinical recurrence of AF, however long-term outcome remains unsatisfactory. Ablation strategies have evolved based on progress in mechanistic understanding, and technologies have advanced continuously. This article reviews current mechanistic concepts and technological advancements in AF treatment, and summarizes their impact on improvement of AF ablation outcome.

Contact Force Assessment In Catheter Ablation Of Atrial Fibrillation

The efficacy of catheter ablation of atrial fibrillation (AF) remains limited. Increase of success would require more durable lesions without increased risk of complications, such as of steam pop and cardiac perforation. Recently, novel technologies have been developed to estimate real-time catheter-tissue contact force (CF). This paper reviews three available tools for assessment of CF and data on experimental or clinical experience. Experimental data with open-irrigated catheter showed that lesion size was greater with applications of lower power (like 30 W) and greater CF (e.g. 30 to 40 g) than vice versa with high power and low CF. Impedance drop in the first 5 seconds was significantly correlated to catheter CF. Perforation was achieved more rapidly with the ablation catheter in a sheath despite the same CF because the sheath prevents catheter buckling. Clinical experience confirmed poor relationship between CF and either unipolar amplitude, bipolar amplitude, or impedance. Within the left atrium, the most common high CF site was found at the anterior/rightward LA roof, directly beneath the ascending aorta (confirmed by merging the CT image and map). Importantly, several studies showed that the use of CF leads to shorter procedure with less fluoroscopy time and less RF applications. CF assessment was also found to be associated with higher proportion of durable lesions. Finally, pilot studies showed that CF measurement could be associated with better clinical efficacy AF ablation.

In vivo left-ventricular contact force analysis: comparison of antegrade transseptal with retrograde transaortic mapping strategies and correlation of impedance and electrical amplitude with contact force

AIMS

Clinical outcomes following radiofrequency ablation of ventricular tachycardias (VTs) depend on catheter tip-to-tissue contact force (CF). Left-ventricular (LV) mapping is performed via antegrade-transseptal or retrograde-transaortic approaches, and the applied CF may depend on the approach used. This study evaluated (i) the impact of antegrade-transseptal vs. retrograde-transaortic LV-mapping approaches on CF and catheter stability and (ii) the clinical value of the commonly used surrogate markers of catheter-myocardial contact-impedance, unipolar, and bipolar electrogram amplitudes.

METHODS AND RESULTS

An antegrade-transseptal and a retrograde-transaortic LV-mapping approach was performed in 10 patients undergoing VT ablation by using CF-sensing catheters. Operators were blinded to CF data and data were analysed according to 11 predefined LV segments. Three thousand three hundred and twenty-four mapping points (1577 antegrade, 1747 retrograde) were analysed, including 80 (2.4%) points with maximum CF > 100 g. Median antegrade and retrograde CF were 16.0 g (q1-q3; 8.4-26.2) and 15.3 g (9.8-23.4), respectively. Contact force was significantly higher antegradely in mid-anteroseptum, mid-lateral, and apical segments, and significantly higher retrogradely in basal-anteroseptum, basal-inferoseptum, basal-inferior, and basal-lateral segments. Contact force did correlate with impedance, unipolar, and bipolar electrogram amplitudes; however, there were large overlaps.

CONCLUSIONS

Antegrade vs. retrograde LV-mapping approaches result in different CF. A combined approach to the LV mapping may improve the overall LV mapping, potentially resulting in better clinical outcomes for the left VT catheter ablation. The previous surrogate markers used to assess CF do correlate with in vivo CF; however, due to a larger overlap, their clinical value is limited.