Optimal Force-Time Integral for Pulmonary Vein Isolation According to Anatomical Wall Thickness Under the Ablation Line

Association of left atrial wall thickness with recurrence after cryoballoon ablation of paroxysmal atrial fibrillation

BACKGROUND

Transmural injury plays a role in successful atrial fibrillation ablation. The effect of left atrial wall thickness (LAWT) on the efficacy of radiofrequency ablation has been identified, but data on the relationship between LAWT and cryoballoon for paroxysmal atrial fibrillation (PAF) are lacking. We aim to explore the relationship between LAWT and recurrence after cryoballoon ablation (CBA).

METHODS

We studied 364 patients (mean age 62 years) with PAF who underwent a second-generation CBA and pre-procedure cardiac CTA. LAWT and left atrial volume index (LAVI) were obtained based on pre-procedure cardiac CTA measurements. Follow-up was at least 12 months and predictors of atrial tachyarrhythmia recurrence during follow-up were assessed.

RESULTS

Patients were followed up for a median of 19 (12-28) months, with an atrial tachyarrhythmia-free rate of 77.5% after cryoablation. Greater LAVI (50.0 ± 19.6 mL/m2 vs. 44.3 ± 15.4 mL/m2, P = 0.018) and greater LAWT (1.67 ± 0.24 vs. 1.46 ± 0.25 mm, P < 0.001) were associated with atrial tachyarrhythmia recurrence. The mean LAWT of PV antrum correlated with TTI (R = 0.252, P < 0.001). Adding LAWT to the established risk model improved both the discrimination and reclassification effects (IDI: 0.099, 95% CI: 0.065-0.134, P < 0.001; NRI: 0.685, 95% CI: 0.455-0.915, P < 0.001). In a multivariable Cox proportional hazard model, the mean LAWT of PV antrum (hazard ratio [HR]:3.657, 95%CI: 2.319-5.765, P < 0.001) was an independent predictor of atrial tachyarrhythmia recurrence after cryoablation.

CONCLUSIONS

The mean LAWT of PV antrum, obtained from preoperative measurements on CT, was associated with atrial tachyarrhythmia recurrence after cryoablation.

Characteristics of right pulmonary vein with an epicardial connection needing additional carina ablation for isolation

Background

This study thought to elucidate the anatomical features that can predict an epicardial connection (EC) between the right pulmonary vein (RPV) and right atrium.

Methods

We retrospectively analyzed 251 consecutive patients undergoing initial radiofrequency pulmonary vein isolation. We defined EC as present when RPV could not be isolated with circumferential ablation and additional ablation for the conduction gap if needed, and RPV isolation could be achieved by ablation for the earliest activation site >10 mm inside the initial ablation line. Using computed tomography data, we evaluated the RPV bifurcation angle, and the area occupation ratio of the carina region to the RPV antrum (ARC) for predicting EC. In subjects with EC undergoing RPV activation mapping after circumferential ablation, the correlation between conduction delay and bipolar/unipolar potential voltage in the carina region was investigated.

Results

There were ECs in 45 out of 251 patients (17.9%). The RPV bifurcation angle (47.7° vs. 38.8°, p < .001) and ARC (37.2% vs. 29.7%, p < .001) were significantly greater in the EC (+) group. Multivariate logistic regression analysis revealed that RPV bifurcation angle (odds ratio [OR]: 1.994, p = .002) and ARC (OR: 3.490, p = .013) were independent predictors of EC. In nine patients with EC undergoing carina region mapping, the unipolar potential voltage was correlated with conduction delay in RPV with EC (R = -0.401, p < .001).

Conclusion

Anatomical features suggesting a wider RPV carina region could predict the presence of EC, and potential with high voltage could be helpful for detecting EC connection sites.

Quantitative late gadolinium enhancement cardiac magnetic resonance analysis of the relationship between ablation parameter and left atrial tissue lesion following pulmonary vein isolation

Background

The impact of ablation parameters on acute tissue lesion formation after pulmonary vein isolation (PVI) has not been sufficiently evaluated in patients with atrial fibrillation. Radiofrequency ablation lesion can be visualized by late gadolinium enhancement cardiac magnetic resonance (LGE-CMR). We sought to quantitatively analyze the relationship between ablation parameter and tissue lesion following PVI at different segments of pulmonary vein (PV) using LGE-CMR.

Methods

Twenty-one patients with atrial fibrillation who underwent PVI procedure were retrospectively enrolled. All patients underwent LGE-CMR examination within 3 days after radiofrequency ablation. Ablation parameters during PVI were documented, including lesion size index (LSI), force-time integral (FTI), power, contact force, temperature, and time of duration. The ablation point was projected onto 3-dimensional (3D) left atrial shell constructed base on LGE-CMR and corresponding image intensity ratio (IIR) was calculated on the same shell. A tissue lesion point was defined when the LGE-CMR IIR was > 1.2.

Results

In total, 1,759 ablation points were analyzed. The ablation parameters and IIRs for each PV segment were significantly different (P < 0.0001). IIRs corresponding to ablation points at posterior of PV tended to be higher than those at non-posterior of PV when similar ablation parameters were applied during ablation. LSI was a better predictor of tissue lesion existence following PVI than FTI, contact force, power, temperature, and duration time at non-posterior wall of PV. The IIR showed positive correlation with LSI at non-posterior wall of PV (non-posterior of right PV, r = 0.13, P = 0.001, non-posterior of left PV, r = 0.26, P < 0.0001).

Conclusion

When similar ablation parameters were applied during PVI, the posterior wall of PV had more severe tissue lesion than non-posterior wall of PV. Therefore, it was reasonable to decrease ablation energy at posterior wall of PV. Moreover, LSI was a better index to reflect tissue lesion quality following PVI at non-posterior of PV.

Characterization of high-power and very-high-power short-duration radiofrequency lesions performed with a new-generation catheter and a temperature-control ablation mode

INTRODUCTION

High-power short-duration (HPSD) has been proposed to shorten procedure times while maintaining efficacy and safety. We evaluated the differences in size and geometry between radiofrequency lesions obtained with this method and conventional ones.

METHODS AND RESULTS

Twenty-eight sets of 10 perpendicular radiofrequency applications were performed with two commercially available catheters: a temperature-controlled HPSD catheter (QDot-Micro) and a conventional power-controlled catheter (Thermocool SmartTouch) on porcine left ventricle. Different power settings (35, 40, 50, and 90 W), contact force (CF; 10 and 20 g), ablation index (AI; 400 and 550), and application times were combined to create conventional (35-40 W), HPSD (50 W) and very-high-power short-duration (VHPSD; 90 W) lesions, that were cross-sectioned and measured. About 4-s VHPSD lesions were smaller, shallower, and thinner than HPSD performed with the QDot-Micro catheter in any scenario of CF or AI (61 ± 7.8 mm³ , 6.1 ± 0.3 mm wide, and 2.9 ± 0.1 mm deep with 10 g; 72.2 ± 0.5 mm³ , 6.8 ± 0.3 mm wide, and 2.9 ± 0.2 mm deep with 20 g). Conventional and HPSD lesions performed with the temperature-controlled catheter were generally bigger, deeper, and wider than the ones obtained with the power-controlled catheter, as well as more consistent in size. This was especially true with the lower CF and AI scenario, while differences were less notable with other setting combinations.

CONCLUSION

VHPSD lesions performed with QDot-Micro catheter were smaller than any other lesions, which is especially attractive for posterior left atrial wall ablation. On the contrary, conventional-powered and HPSD lesions performed with this catheter were equally sized (or even bigger with lower CF and AI objectives), as well as more consistent in size, which would guarantee transmurality in other locations.

Ablation Index Guided Left Atrial Posterior Wall Isolation

Ablation index (AI)-guided linear ablation is reported to be feasible.We assessed the feasibility of AI-guided left atrial (LA) posterior wall isolations (PWIs) using different target AI values.Seventy-one persistent atrial fibrillation patients who underwent AI-guided PWIs following pulmonary vein isolation were included. LA linear lesions were created with strict contiguity (inter-lesion distance < 4 mm) and different predetermined AI target values (Group-1: 430, Group-2: 450). The data was analyzed retrospectively.The total radiofrequency application time of the roof and bottom-line ablation was a median of 2.8 (2.0, 3.8) and 3.6 (2.8, 4.3) minutes. The first-pass PWI success rate (26/35 [74.3%] versus 16/36 [44.4%], P = 0.011) and a first-pass roof line block (28/35 [80.0%] versus 21/36 [58.3%], P = 0.048) were significantly higher in Group-2 than Group-1, but that for the first-pass bottom line block was similar between Group-1 and Group-2 (29/36 [80.6%] versus 29/35 [82.9%], P = 0.80). Successful PWIs were achieved by additional applications in all. The significant parameter associated with a successful first-pass LA roof line block was a greater RF power, and that for the LA bottom were a higher radiofrequency power and shorter inter-lesion distance. Conduction gaps were mostly located at the middle of both lines. Among 22 roof line gaps, 12 were closed on the line whereas 10 (45.4%) required ablation inside the posterior wall for PWIs. On the contrary, all 11 gaps on bottom lines were closed on the line.Successful first-pass PWIs were obtained in 74% of patients using a target AI value of 450 and strict criteria for the lesion contiguity.

Requirement of larger local impedance reduction for successful lesion formation at carinal area during pulmonary vein isolation

PURPOSE

Local impedance (LI) measurement from an ablation catheter is useful in predicting lesion size and acute success of pulmonary vein isolation (PVI). The LI variation can be described by absolute LI drop (ΔLID) or ΔLID/initial LI (%LID). We evaluated the utility of these parameters in predicting acute lesion durability during PVI using a novel catheter capable of measuring both LI and contact force (CF).

METHODS

PVI with a targeted CF, power, and duration was performed in 23 consecutive patients with paroxysmal atrial fibrillation. LI was blinded to operators during ablation. Parameters for each RF application were collected and compared for acute successful lesions and gaps.

RESULTS

A total of 1633 RF applications including 97 (5.9%) gap lesions were analyzed. Successful lesions were more frequently observed at non-carinal sites and those with higher contact force, FTI, initial LI, and larger variation of LI and generator impedance (GI). Multivariate analysis demonstrated that absolute GI drop (ΔGID) [OR 1.09 (1.04-1.15), p < 0.001], ΔLID [1.12 (1.09-1.16), p < 0.001], ΔGID/initial GI (%GID) [OR 1.04 (1.01-1.07), p = 0.01], and %LID [OR 1.15 (1.12-1.28), p < 0.001] were significantly associated with successful lesions, and carinal site [OR 0.15(0.09-0.24), p < 0.001] was significantly related to gaps. Both ΔLID and %LID equally predicted the acute durability of lesions during PVI. ΔLID ≥ 24Ω and %LID ≥ 15% at the carina, and ΔLID ≥ 21Ω and %LID ≥ 14% at non-carinal sites significantly predicted acute successful lesions with negative predictive values of 93-99%.

CONCLUSIONS

Both ΔLID and %LID were equally useful in predicting acute successful lesions during PVI. Larger cut-off values should be applied to carinal sites.

Esophageal thermal injury in catheter ablation of atrial fibrillation

Pulmonary vein isolation is an established method for the catheter ablation of atrial fibrillation. Esophageal thermal injuries, such as esophageal erosion, ulceration and periesophageal nerve injury leading to gastric hypomotility, are important complications associated with pulmonary vein isolation. In this review article, we describe the mechanisms, characteristics and the predictors of esophageal thermal injury associated with pulmonary vein isolation.

Influence of power setting on superior vena cava potential during right pulmonary vein isolation

PURPOSE

High-power short-duration (HP-SD) ablation could reduce collateral tissue damage by shortening the conductive heating phase. However, it is difficult to evaluate the transmural effect of ablation lesions during pulmonary vein isolation (PVI) procedures. The present study aimed to evaluate the change in superior vena cava (SVC) potential delay as a surrogate marker of collateral tissue damage during right PVI, which is adjacent to SVC.

METHODS

Out of 250 consecutive patients who underwent PVI, 86 patients in whom SVC potential during sinus rhythm was recorded both before and after right PVI were analyzed. In 46 of the patients, an HP-SD setting of 45-50 W was used (HP-SD group). In the remaining 40 patients, a conventional power setting of 20-30 W was used (conventional group). We compared the change in SVC potential delay after right PVI, radiofrequency energy, and mean contact force in the anterior-superior right PVI line, which was close to the posterior aspect of SVC, between the two groups.

RESULTS

Although the total delivered radiofrequency energy (2,924 J vs. 2,604 J) and the mean contact force (18.5 g vs. 16.0 g) in the SVC overlapping area did not differ, the change in SVC potential delay after right PVI was significantly longer in the conventional group compared to the HP-SD group (5.0 ms vs. 0.0 ms, p < 0.001).

CONCLUSIONS

The changes in SVC potential delay after right PVI might be a surrogate marker of collateral tissue damage according to the used energy settings.

Comparison of lesion characteristics between conventional and high-power short-duration ablation using contact force-sensing catheter in patients with paroxysmal atrial fibrillation

Background

Transmural lesion creation is essential for effective atrial fibrillation (AF) ablation. Lesion characteristics between conventional energy and high-power short-duration (HPSD) setting in contact force-guided (CF) ablation for AF remained unclear.

Methods

Eighty consecutive AF patients who received CF with conventional energy setting (power control: 25–30 W, force–time integral = 400 g s, n = 40) or with HPSD (power control: 40–50 W, 10 s, n = 40) ablation were analyzed. Of them, 15 patients in each conventional and HPSD group were matched by age and gender respectively for ablation lesions analysis. Type A and B lesions were defined as a lesion with and without significant voltage reduction after ablation, respectively. The anatomical distribution of these lesions and ablation outcomes among the 2 groups were analyzed.

Results

1615 and 1724 ablation lesions were analyzed in the conventional and HPSD groups, respectively. HPSD group had a higher proportion of type A lesion compared to conventional group (P < 0.01). In the conventional group, most type A lesions were at the right pulmonary vein (RPV) posterior wall (50.2%) whereas in the HPSD group, most type A lesions were at the RPV anterior wall (44.0%) (P = 0.04). The procedure time and ablation time were significantly shorter in the HPSD group than that in the conventional group (91.0 ± 12.1 vs. 124 ± 14.2 min, P = 0.03; 30.7 ± 19.2 vs. 57.8 ± 21 min, P = 0.02, respectively). At a mean follow-up period of 11 ± 1.4 months, there were 13 and 7 patients with recurrence in conventional and HPSD group respectively (P = 0.03).

Conclusion

Optimal ablation lesion characteristics and distribution after conventional and HPSD ablation differed significantly. HPSD ablation had shorter ablation time and lower recurrence rate than did conventional ablation.

Optimizing Durability in Radiofrequency Ablation of Atrial Fibrillation

Radiofrequency ablation (RFA) remains a highly effective therapy in the management of paroxysmal atrial fibrillation (PAF) and is an important therapeutic option in the management of persistent atrial fibrillation (PeAF) when clinically indicated. Lesion size is influenced by many parameters, which include those related to energy application (RFA power, temperature, and time), delivery mechanism (electrode size, orientation, and contact force), and the environment (blood flow and local tissue contact, stability, and local impedance). Successful durable RFA is dependent on achieving lesions that are reliably transmural and contiguous, whilst also avoiding injury to the surrounding structures. This review focuses on the variables that can be adjusted in connection with RFA to achieve long-lasting lesions that enable patients to derive the maximum sustained benefit from pulmonary vein isolation and additional lesion sets if utilized.

Tailored ablation index for pulmonary vein isolation according to wall thickness within the ablation circle

BACKGROUND

Ablation index (AI), a novel lesion quality marker, includes contact force, time, and power of radiofrequency (RF) application, but not regional variation in wall thickness within the wide antral catheter ablation (WACA) circle. This study explored the relationships among AI target value, atrial wall thickness, and gap formation within the WACA circle in patients with paroxysmal atrial fibrillation (PAF).

METHODS

We evaluated 102 consecutive patients (mean age, 65 ± 9 years) with PAF who underwent AI-guided WACA for ipsilateral pulmonary vein isolation (PVI). Each WACA circle was subdivided into eight segments, and overall 7143 RF applications were delivered, including 125 gaps in PVI ablation lines. For each RF tag within the ablation circle, we collected data on ablation lesion depth surrogates (time of application, delivery power, impedance drop, average contact force, force-time integral [FTI], and AI) and left atrial wall thickness measured by multidetector computer tomography scanning.

RESULTS

The anterior and roof walls were the thickest segments of the ablation circle, in which 85.8% of gaps concentrated, while the posterior and inferior walls were the thinnest. Gap formation was significantly associated with FTI, AI, wall thickness, FTI/wall thickness, and AI/wall thickness. AI/wall thickness had the highest predictive value for gap formation, with a cutoff of 195.6 au/mm for effective ablation.

CONCLUSIONS

In AI-guided PVI of PAF, AI/wall thickness by normalizing myocardial thickness variation along the WACA circle was a strong predictor of gap formation, with a target of 195.6 au/mm appearing suitable for effective ablation.

Characteristics of Esophageal Injury in Ablation of Atrial Fibrillation Using a High-Power Short-Duration Setting

BACKGROUND

The mechanism of esophageal thermal injury (ETI; esophageal mucosal injury and periesophageal nerve injury leading to gastric hypomotility) remains unknown when using a high-power short-duration (HP-SD) setting. This study sought to evaluate the characteristics of esophageal injuries in atrial fibrillation ablation using a HP-SD setting.

METHODS

After exclusion of 5 patients with their esophagus at the right portion of left atrium and 21 patients with additional ablations such as box isolation and low voltage area ablation in left atrium posterior wall, 271 consecutive patients (62±10 years, 56 women) who underwent pulmonary vein isolation by radiofrequency catheter ablation were analyzed. In the 101 patients, a HP-SD setting at 45 to 50 W with an Ablation Index module was used (HP-SD group). In the remaining 170 patients before introduction of the HP-SD setting, a conventional power setting of 20 to 30 W with contact force monitoring was used (conventional group). We performed esophagogastroduodenoscopy after pulmonary vein isolation in all patients and investigated the incidence and characteristics of ETI.

RESULTS

Although the incidence of ETI was significantly higher in the HP-SD group compared with the conventional group (37% versus 22%, P=0.011), the prevalence of esophageal lesions did not differ between the groups (7% versus 8%). Multivariate logistic regression analysis revealed that the use of the HP-SD setting (odds ratio, 6.09, P<0.001), and the parameters that suggest anatomic proximity surrounding the esophagus, were independent predictors of ETI. However, the majority of ETI in the HP-SD group was gastric hypomotility, and the thermal injury was limited to the shallow layer of the periesophageal wall using the HP-SD setting.

CONCLUSIONS

Although the use of the HP-SD setting was a strong predictor of ETI, it could avoid deeper thermal injuries that reach the esophageal mucosal layer.

Impact of local left atrial wall thickness on the incidence of acute pulmonary vein reconnection after Ablation Index-guided atrial fibrillation ablation

•

Ablation Index-guided ablation allows for ablation lesions of consistent depth.

•

Ablation Index-guided ablation is limited by ignoring local wall thickness.

•

Local atrial wall thickness is associated with acute pulmonary vein reconnection.

•

Wall thickness adjusted Ablation Index targets may improve ablation outcomes.

Background

Although Ablation Index (AI)-guided ablation facilitates creation of lesions of consistent depth, pulmonary vein (PV) reconnection is still commonly observed after AI-guided pulmonary vein isolation (PVI). The present study aimed to investigate the impact of local left atrial wall thickness on the incidence of acute PV reconnection after AI-guided atrial fibrillation (AF) ablation.

Methods and results

Seventy patients (63% paroxysmal AF, 67% male, mean age 63 ± 8 years) who underwent preprocedural CT imaging and AI-guided AF ablation were studied. Occurrence of acute PV reconnection after initial PVI was assessed after a 30-minute waiting period. Ablation procedures were retrospectively analyzed and each ablation circle was subdivided into 8 segments. Minimum AI, force-time integral, contact force, ablation duration, power, impedance drop and maximum interlesion distance were determined for each segment. PV antrum wall thickness was assessed for each segment on reconstructed CT images based on patient-specific thresholds in Hounsfield Units. Acute reconnection occurred in 27/1120 segments (2%, 15 anterior/roof, 12 posterior/inferior) in 19/140 ablation circles (14%). Reconnected segments were characterized by a greater local atrial wall thickness, both in anterior/roof (1.87 ± 0.42 vs. 1.54 ± 0.42 mm; p < 0.01) and posterior/inferior (1.43 ± 0.20 vs. 1.16 ± 0.22 mm; p < 0.01) segments. Minimum AI, force-time integral, contact force, ablation duration, power, impedance drop and maximum interlesion distance were not associated with acute reconnection.

Conclusions

Local atrial wall thickness is associated with acute pulmonary vein reconnection after AI-guided PVI. Individualized AI targets based on local wall thickness may be of use to create transmural ablation lesions and prevent PV reconnection after PVI.

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.

Pulmonary vein isolation using ablation index vs. CLOSE protocol with a surround flow ablation catheter

Aims

Pulmonary vein isolation (PVI) using ablation index (AI) incorporates stability, contact force (CF), time, and power. The CLOSE protocol combines AI and ≤6 mm interlesion distance. Safety concerns are raised about surround flow ablation catheters (STSF). To compare safety and effectiveness of an atrial fibrillation (AF) ablation strategy using AI vs. CLOSE protocol using STSF.

Methods and results

First cluster was treated using AI and second cluster using CLOSE. Procedural data, safety, and recurrence of any atrial tachycardia (AT) or AF &gt;30 s were collected prospectively. All Classes 1c and III anti-arrhythmic drugs (AAD) were stopped after the blanking period. In total, all 215 consecutive patients [AI: 121 (paroxysmal: n = 97), CLOSE: n = 94 (paroxysmal: n = 74)] were included. Pulmonary vein isolation was reached in all in similar procedure duration (CLOSE: 107 ± 25 vs. AI: 102 ± 24 min; P = 0.1) and similar radiofrequency time (CLOSE: 36 ± 11 vs. AI: 37 ± 8 min; P = 0.4) but first pass isolation was higher in CLOSE vs. AI [left veins: 90% vs. 80%; P &lt; 0.05 and right veins: 84% vs. 73%; P &lt; 0.05]. Twelve-month off-AAD freedom of AF/AT was higher in CLOSE vs. AI [79% (paroxysmal: 85%) vs. 64% (paroxysmal: 68%); P &lt; 0.05]. Only four patients (2%) without recurrence were on AAD during follow-up. Major complications were similar (CLOSE: 2.1% vs. AI: 2.5%; P = 0.87).

Conclusion

The CLOSE protocol is more effective than a PVI approach solely using AI, especially in paroxysmal AF. In this off-AAD study, 79% of patients were free from AF/AT during 12-month follow-up. The STSF catheter appears to be safe using conventional CLOSE targets.

Mapping and Imaging in Non-paroxysmal AF

Despite intense research efforts, maintenance of sinus rhythm in patients with non-paroxysmal AF remains challenging with suboptimal outcomes. A major limitation to the success of current ablation-based treatments is that our understanding of AF pathophysiology is incomplete. Advances in imaging and mapping tools have been reported to improve ablation outcomes. However, the role of these new approaches on the clinical care of patients with AF remains to be validated and better understood before wide adoption can occur. This article reviews the current techniques of imaging and mapping that can be applied in the management of patients with non-paroxysmal AF with a focus on their relevance to catheter ablation. Future applications and opportunities for new knowledge are also discussed.

A Pilot Study on Parameter Setting of VisiTag™ Module during Pulmonary Vein Isolation

Objectives

To identify optimal predefined criteria (OPC) for filters of the VisiTag™ module in the CARTO 3 system during pulmonary vein isolation (PVI).

Methods

Thirty patients with atrial fibrillation (AF) who experienced PVI first were enrolled. PVI was accomplished by using a Thermocool SmartTouch catheter. Ablation lesions were tagged automatically as soon as predefined criteria of the VisiTag™ module were met. OPC should be that ablation with the setting resulting in the conduction gap (CG) as few as possible, while contiguous encircling ablation line (CEAL) without the tag gap (TG) on the 3D anatomic model as much as possible.

Result(s)

When ablation with parameter setting is being catheter movement with a 3 mm distance limit for at least 20 s and force over time (FOT) being off, there were 60 CEAL without TG on the 3D anatomic model. However, 26 CGs were found. After changing FOT setting to be a minimal force of 5 g with 50% stability time, 22 TGs were displayed. Of them, 20 TGs were accompanied by CGs. On reablation at sites of TG with changed parameter setting, 18 CGs were eliminated when 20 TGs disappeared. When reablation with FOT is being a minimal force of 10 g with 50% stability time, 6 remaining CGs were eliminated. However, there was no CEAL. With a mean of follow-up 10.93 months, 2 patients with persistent AF suffered AF recurrence.

Conclusion

A 3 mm distance limit for at least 20 s and FOT being a minimal force of 5 g with 50% stability time might be OPC for the VisiTag™ module.

Optimal lesion size index to prevent conduction gap during pulmonary vein isolation

INTRODUCTION

A novel real-time lesion size index (LSI) that incorporates contact force (CF), time, and power has been developed for safe and effective catheter ablation. The optimal LSI was evaluated to eliminate gap formation during pulmonary vein isolation (PVI).

METHODS AND RESULTS

Consecutive patients were enrolled, who underwent their first PVI using a fiber-optic CF-sensing catheter for atrial fibrillation between December 2016 and October 2017. The CF parameters, force-time integral (FTI), and LSI for 3095 ablation points in 34 patients were evaluated. The FTI and LSI in the lesions with gaps or dormant conduction (gaps/DC) were significantly lower than those in the lesion without gaps/DC (FTI: 140.5 ± 54.5 and 232.4 ± 121.4 g s, P < 0.0001; LSI: 4.0 ± 0.6 and 4.7 ± 0.9, P < 0.0001, respectively). On receiver operating characteristic curve analysis, the optimal LSI threshold was 4.05 (sensitivity, 63.4%; specificity, 76.3%). The LSI of <5.25 predicted a gap or DC with a high sensitivity (sensitivity, 97.6%; specificity, 25.7%). In the posterior wall, which was 37% thinner than the nonposterior wall, a lower LSI of <3.95 showed a relatively high sensitivity (92.3%) and specificity (65.6%).

CONCLUSIONS

The LSI can be used to predict gaps/DC during the PVI procedure. An LSI of 5.2 may be a suitable target for effective lesion formation. An LSI of 4.0 may be acceptable in the posterior wall, especially in areas adjacent to the esophagus.

Ablation Index for Catheter Ablation of Atrial Fibrillation - Clinical Applicability and Comparison With Force-Time Integral

BACKGROUND

Key determinants for lesion formation in catheter ablation are contact force, radiofrequency (RF) power and time. The aim of this study was to evaluate the clinical applicability of ablation index (AI), a novel non-linear formula based on these components, and to compare AI with the conventional linear force-time interval (FTI) in pulmonary vein isolation (PVI). Methods and Results: Target AI ranges were defined for anatomical segments of the ipsilateral pulmonary veins. The operator was blinded to AI during PVI for the initial 11 patients (group A), and was unblinded for the remaining 23 patients (group B). We assessed (1) the clinical value of AI to avoid excessively high and low values with an operator blinded vs. non-blinded to AI; and (2) the relation of AI and FTI in predefined ranges. In group A, 235/564 lesions (41.7%) were in the predefined target range as compared with 1,171/1,412 lesions (82.9%) in group B (P<0.001). A given AI may correspond to a wide range of FTI, as reflected by a quartile coefficient of dispersion for AI of 0.11 vs. a quartile coefficient of dispersion for FTI of 0.36.

CONCLUSIONS

Incorporating RF current power, the non-linear AI provides more comprehensive information during PVI compared with FTI. Given that the FTI for a given AI varies widely, the value of FTI in clinical practice is questionable.

Two Year, Single Center Clinical Outcome After Catheter Ablation For Paroxysmal Atrial Fibrillation Guided by Lesion Index

Background

This study describes the use of lesion index (LSI) as a direct measure to assess the adequacy of ablation lesion formation with force-sensing catheters in ablation of paroxysmal atrial fibrillation (PAF). LSI is calculated by the formula:LSI = CF (g) ×Current (mA) ×Time (sec).

Methods

Fifty consecutive patients with PAF underwent pulmonary vein (PV) isolation using a catheter dragging technique and targeting different LSI values in different anatomical areas.A force-sensing ablation catheter was used to continuously measure contact force (CF) and guide radiofrequency ablation (RF) lesion formation. Ablation lesions were delivered to achieve an LSI value of 5.0 in posterior locations, 5.5 in anterior locations and 6.0 in the regionbetween the left atrial appendage and left superiorpulmonary vein ridge. Force-time Integral (FTI) was not used to evaluate lesion formation.

Results

A single center, retrospective analysis was performed with 196/198 (99%) PVs acutely isolated. The mean procedure time was 134 ± 34 mins and the mean fluoroscopy time was 7.8 ± 3.2 mins. At a mean follow up of two years, 43/50 (86%) of patients were in normal sinus rhythm with no documented recurrences of atrial fibrillation.

Conclusion

LSI can be used to guide the placement of durable lesion formation with RF ablation using CF catheters in patients with PAF.

The relationship of early recurrence of atrial fibrillation and the 3-month integrity of the ablation lesion set

Early recurrence of atrial fibrillation (ERAF) after catheter-ablation (CA) can be a transient phenomenon due to inflammation, or a harbinger of late AF recurrence due to CA lesion (re)conduction. We studied the relationship between ERAF and the 3-month CA lesions integrity. Forty one consecutive AF patients who underwent a pulmonary vein isolation (PVI), roof line (RL) and mitral isthmus line (MIL) CA were enrolled. At 3 months all patients underwent invasive assessment of the lesion set integrity irrespective of ERAF. The PVI, RL and MIL ablation was successful in 100.0%, 95.1% and 82.9% patients, respectively. At the 3-month remapping, a gap in PVI-lesion(s), RL or MIL was identified in 61.0%, 31.7% and 36.6% patients, respectively. Patients with (n = 17, 41.5%) compared to those without ERAF (n = 24) had a significantly higher rate of any PV-reconnection (88.2% vs. 41.7%), the right PV(s)-reconnection (82.5% vs. 29.2%) and the RL gap (52.9% vs. 16.7%), as well as a higher number of reconnected right PVI-segments, all p < 0.05. On multivariate analysis, only the number of reconnected right PVI-segments was associated with ERAF (OR 4.26, p = 0.004). The ERAF following PVI + RL + MIL ablation was significantly related to 3-month PV-reconnections and the presence of RL gaps.

Lesion modeling, characterization, and visualization for image-guided cardiac ablation therapy monitoring

In spite of significant efforts to improve image-guided ablation therapy, a large number of patients undergoing ablation therapy to treat cardiac arrhythmic conditions require repeat procedures. The delivery of insufficient thermal dose is a significant contributor to incomplete tissue ablation, in turn leading to the arrhythmia recurrence. Ongoing research efforts aim to better characterize and visualize RF delivery to monitor the induced tissue damage during therapy. Here, we propose a method that entails modeling and visualization of the lesions in real-time. The described image-based ablation model relies on classical heat transfer principles to estimate tissue temperature in response to the ablation parameters, tissue properties, and duration. The ablation lesion quality, geometry, and overall progression are quantified on a voxel-by-voxel basis according to each voxel's cumulative temperature and time exposure. The model was evaluated both numerically under different parameter conditions, as well as experimentally, using ex vivo bovine tissue samples undergoing ex vivo clinically relevant ablation protocols. The studies demonstrated less than 5°C difference between the model-predicted and experimentally measured end-ablation temperatures. The model predicted lesion patterns were within 0.5 to 1 mm from the observed lesion patterns, suggesting sufficiently accurate modeling of the ablation lesions. Lastly, our proposed method enables therapy delivery feedback with no significant workflow latency. This study suggests that the proposed technique provides reasonably accurate and sufficiently fast visualizations of the delivered ablation lesions.

Impact of left atrial size on isolation area in the acute phase of pulmonary vein isolation using 28 mm cryoballoon

BACKGROUND

The impact of left atrial (LA) size on isolation area (ISA) using a 28-mm second-generation cryoballoon (CB) in the acute phase after pulmonary vein isolation (PVI) and the differences of CB from contact force-guided radiofrequency (RF) ablation have not been fully investigated.

METHODS

We examined 85 consecutive patients (CB group, 35; RF group, 50) with drug-refractory paroxysmal atrial fibrillation who underwent their first PVI procedure at two institutions. We evaluated ISA after PVI using 3D-Merge computed tomography images (GE Healthcare, Little Chalfont, UK) and high-resolution electroanatomical mapping.

RESULTS

Total ISA was significantly smaller in the CB group (20.6 ± 6.0 cm² ) than in the RF group (29.0 ± 7.1 cm² ; P < 0.0001). In the CB group, ISA of the left pulmonary vein (LPV), right pulmonary vein (RPV), and total ISA were not correlated with the left atrial surface area (LASA). The ratios of ISA to LASA (%ISA) of LPV and total ISA negatively correlated with LASA in the CB group (LPV: r = -0.4001, P = 0.0173; total ISA: r = -0.4733, P = 0.0041). In contrast, in the RF group, ISA of LPV, RPV, and total ISA positively correlated with LASA; (LPV: r = 0.5155, P = 0.001; RPV: r = 0.6398, P < 0.0001; total ISA: r = 0.7299, P < 0.0001).

CONCLUSION

ISA created using CB was significantly smaller than that using RF and did not change regardless of LASA increment. Differences in ISA between the two groups became more prominent in the large atrium.

Strategy and Outcome of Catheter Ablation for Persistent Atrial Fibrillation - Impact of Progress in the Mapping and Ablation Technologies

Pulmonary vein (PV) antrum isolation (PVAI) is effective in treating paroxysmal atrial fibrillation (AF) but is less so for persistent AF. A recent randomized study on the ablation strategies for persistent AF demonstrated that 2 common atrial substrate modifications, creation of linear lesions in the left atrium and ablation of complex fractionated electrogram sites, in addition to PVAI did not improve the outcome compared with stand-alone PVAI, suggesting the necessity of a more individualized, selective approach to persistent AF. There are emerging technologies, including high-resolution mapping with the use of multi-electrode catheter and auto mapping system and contact force (CF) guide ablation; the former allows rapid and accurate confirmation of the completeness of PVAI, and the latter enhances the achievement of durable ablation lesions more securely. Ablation for fibrotic area(s) has been proposed as a new approach for substrate modification, and high-resolution mapping is useful to define the area with low-voltage electrograms, a surrogate marker for atrial fibrosis. Ablation for non-PV triggers in addition to PVAI improves the outcome of persistent AF. Further, durable isolation of the left atrial posterior wall may reduce AF recurrence. These ablation strategies with concomitant use of the emerging technologies are strongly expected to enhance the effectiveness of catheter ablation for persistent AF.

Contact force sensing for ablation of persistent atrial fibrillation: A randomized, multicenter trial

BACKGROUND

Impact of contact force sensing (CFS) on ablation of persistent atrial fibrillation (PeAF) is unknown.

OBJECTIVE

The purpose of the TOUCH AF (Therapeutic Outcomes Using Contact force Handling during Ablation of Persistent Atrial Fibrillation) randomized trial was to compare CFS-guided ablation to a CFS-blinded strategy.

METHODS

Patients (n = 128) undergoing first-time ablation for persistent AF were randomized to a CFS-guided vs CFS-blinded strategy. In the CFS-guided procedure, operators visualized real-time force data. In the blinded procedure, force data were hidden. Wide antral pulmonary vein isolation plus a roof line were performed. Patients were followed at 3, 6, 9, and 12 months with clinical visit, ECG, and 48-hour Holter monitoring. The primary endpoint was cumulative radiofrequency (RF) time for all procedures. Atrial arrhythmia >30 seconds after 3 months was a recurrence.

RESULTS

PeAF was continuous for 26 weeks (interquartile range [IQR] 13-52), and left atrial size was 45 ± 5 mm. Force in the CFS-blinded and CFS-guided arms was 12 g [IQR 6-20] and 14 g [IQR 9-20] (P = .10), respectively. Total RF time did not differ between CFS-guided and CFS-blinded groups (49 ± 14 min vs 50 ± 20 min, respectively; P = .70). Single procedure freedom from atrial arrhythmia was 60% in the CFS-guided arm and 63% in the CFS-blinded arm off drugs. Lesions with gaps were associated with significantly less force (11.4 g [IQR 6-19] vs 13.2 g [IQR 8-20], respectively; P = .0007) and less force-time integral (174 gs [IQR 91-330] vs 210 gs [IQR 113-388], respectively; P <.001).

CONCLUSION

CFS-guided ablation resulted in no difference to RF time or 12-month outcome. Lower force/force-time integral was associated with significantly more gaps.

Prospective use of Ablation Index targets improves clinical outcomes following ablation for atrial fibrillation

AIMS

Late recovery of ablated tissue leading to reconnection of pulmonary veins remains common following radiofrequency catheter ablation for AF. Ablation Index (AI), a novel ablation quality marker, incorporates contact force (CF), time, and power in a weighted formula. We hypothesized that prospective use of our previously published derived AI targets would result in better outcomes when compared to CF-guided ablation.

METHODS

Eighty-nine consecutive drug-refractory AF patients (49% paroxysmal) underwent AI-guided ablation (AI-group). AI targets were 550 for anterior/roof and 400 for posterior/inferior left atrial segments. Procedural and clinical outcomes of these patients were compared to 89 propensity-matched controls who underwent CF-guided ablation (CF-group). All 178 procedures were otherwise similar, and both groups were followed-up for 12 months. The last 25 patients from each group underwent analysis of all VisiTags™ for ablation duration, CF, Force-Time Integral, and impedance drop.

RESULTS

First-pass pulmonary vein isolation (PVI) was more frequent in AI-group than in CF-group (173 [97%] vs. 149 [84%] circles, P < 0.001), and acute PV reconnection was lower (11 [6%] vs. 24 [13%] circles, P = 0.02). Mean PVI ablation time was similar (AI-group: 42 ± 9 vs. CF-group: 45 ± 14 minutes, P = 0.14). Median impedance drop for AI-group was significantly higher than in CF-group (13.7 [9-19] Ω vs. 8.8 [5.2-13] Ω, P < 0.001). Two major complications occurred in CF-group and none in AI-group. Atrial tachyarrhythmia recurrence was significantly lower in AI-group (15 of 89 [17%]) than in CF-group (33 of 89 [37%], P = 0.002).

CONCLUSION

AI-guided ablation is associated with significant improvements in the incidence of acute PV reconnection and atrial tachyarrhythmia recurrence rate compared to CF-guided ablation, potentially due to creation of better quality lesions as suggested by greater impedance drop.

Contact force technology integrated with 3D navigation system for atrial fibrillation ablation: improving results?

INTRODUCTION

Pulmonary veins isolation (PVI) by radiofrequency (RF) ablation is currently an established treatment for symptomatic, drug-resistant paroxysmal atrial fibrillation. Although the effectiveness of the therapy has been clearly demonstrated, success rate after a single procedure is still sub-optimal. The main reason for recurrences after PVI is electrical pulmonary vein-atrium reconnection. In order to increase the likelihood of permanent PVI, the creation of a transmural, durable lesion is mandatory. The main determinants of lesion size and transmurality are power, stability, duration and contact-force during RF application. In recent times, catheters with contact-force sensors have been developed and released for clinical use. Areas covered: The present review summarizes rational and clinical evidences for efficacy and safety of contact force (CF) technology integrated into 3D navigation systems for AF ablation. Expert commentary Although CF technology has a strong rational, clinical data on the superior safety and efficacy of CF technology over traditional non-CF catheters are still conflicting. The reason for that is very likely to rely on the lack of definite data on how to optimize CF parameters and how to integrate CF data with power, duration of RF applications and information on catheter stability.

High-voltage zones within the pulmonary vein antra: Major determinants of acute pulmonary vein reconnections after atrial fibrillation ablation

PURPOSE

Recurrence of atrial fibrillation (AF) after pulmonary vein isolation (PVI) is mainly due to PV reconnections. Patient-specific tissue characteristics that may contribute remain unidentified. This study aimed to assess the relationship between the bipolar electrogram voltage amplitudes recorded from the PV-left atrial (LA) junction and acute PV reconnection sites.

METHODS

Three-dimensional LA voltage maps created before an extensive encircling PVI in 47 AF patients (31 men; mean age 62 ± 11 years) were examined for an association between the EGM voltage amplitude recorded from the PV-LA junction and acute post-PVI PV reconnections (spontaneous PV reconnections and/or ATP-provoked dormant PV conduction).

RESULTS

Acute PV reconnections were observed in 17 patients (36%) and in 24 (3%) of the 748 PV segments (16 segments per patient) and were associated with relatively high bipolar voltage amplitudes (3.26 ± 0.85 vs. 1.79 ± 1.15 mV, p < 0.0001) and a relatively low mean force-time integral (FTI) (428 ± 56 vs. 473 ± 76 gs, p = 0.0039) as well as FTI/PV-LA bipolar voltage (137 [106, 166] vs. 295 [193, 498] gs/mV, p < 0.0001). An analysis of the receiver operating characteristic curves revealed a high prognostic performance of the LA bipolar voltage and FTI/PV-LA bipolar voltage for acute PV reconnections (areas under the curve: 0.86 and 0.89, respectively); the best cutoff values were >2.12 mV and ≤183 gs/mV, respectively.

CONCLUSIONS

The PV-LA voltage on the PV-encircling ablation line and FTI/PV-LA voltage were related to the acute post-PVI PV reconnections. A more durable ablation strategy is warranted for high-voltage zones.

General anesthesia improves contact force and reduces gap formation in pulmonary vein isolation: a comparison with conscious sedation

Compared to conscious sedation (CS), the use of general anesthesia (GA) in pulmonary vein isolation (PVI) is associated with a lower recurrence rate of atrial fibrillation (AF). GA may improve catheter stability and mapping system accuracy compared to CS, but its influence on contact force (CF) parameters during ipsilateral PVI has not previously been investigated. The study population comprised 176 consecutive patients (107 in GA group and 69 in CS group) with AF who underwent their first PVI procedure. We retrospectively assessed CF parameters, force-time integral (FTI), FTI/wall thickness during anatomical ipsilateral PVI and long-term outcome after ablation. Complete PVI with single continuous circular lesions around the ipsilateral PVs was achieved in 54 patients (50.5%) in the GA group but only 24 patients (34.8%) in the CS group (P = 0.04). The distribution of gaps did not differ between the groups. All CF parameters were significantly higher in the GA group than in the CS group (average CF: 19.4 ± 8.7 vs. 16.7 ± 7.7 g, P < 0.0001; FTI: 399.0 ± 262.5 vs. 293.9 ± 193.4 gs, P < 0.0001; FTI/wall thickness: 155.5 ± 106.1 vs. 115.7 ± 85.5 gs, P < 0.0001). GA was associated with lower AF recurrence rate in patients with paroxysmal AF but not with persistent AF. Compared with CS, GA improves CF parameters, FTI and FTI/wall thickness, and reduced gap formation after ipsilateral PVI.

Optimal Force-Time Integral for Pulmonary Vein Isolation According to Anatomical Wall Thickness Under the Ablation Line

Background

Low contact force and force–time integral (FTI) during catheter ablation are associated with ineffective lesion formation, whereas excessively high contact force and FTI may increase the risk of complications. We sought to evaluate the optimal FTI for pulmonary vein (PV) isolation based on atrial wall thickness under the ablation line.

Methods and Results

Contact force parameters and FTI during anatomical ipsilateral PV isolation for atrial fibrillation and atrial wall thickness were assessed retrospectively in 59 consecutive patients for their first PV isolation procedure. The PV antrum was divided into 8 segments, and the wall thickness of each segment under the ablation line was determined using multidetector computed tomography. The FTI for each ablation point was divided by the wall thickness of the PV antrum segment where each point was located to obtain FTI/wall thickness. In total, 5335 radiofrequency applications were delivered, and 85 gaps in PV isolation ablation lines and 15 dormant conductions induced by adenosine were detected. The gaps or dormant conductions were significantly associated with low contact force, radiofrequency duration, FTI, and FTI/wall thickness. Among them, FTI/wall thickness had the best prediction value for gaps or dormant conductions by receiver operating characteristic curve analysis. FTI/wall thickness of <76.4 gram‐seconds per millimeter (gs/mm) predicted gaps or dormant conductions with sensitivity (88.0%) and specificity (83.6%), and FTI/wall thickness of <101.1 gs/mm was highly predictive (sensitivity 97.0%; specificity 69.6%).

Conclusions

FTI/wall thickness is a strong predictor of gap and dormant conduction formation in PV isolation. An FTI/wall thickness ≈100 gs/mm could be a suitable target for effective ablation.