Persistence of pulmonary vein isolation after robotic remote-navigated ablation for atrial fibrillation and its relation to clinical outcome

Novel Clue to Locate Conduction Gaps in the Pulmonary Vein Isolation Ablation Line

Background: Several methods have been reported for locating the conduction gap (CG) in the pulmonary vein isolation (PVI) ablation line. However, the value of the interval between far-field atrial potential (FFP) and pulmonary vein potential (PVP) remains unknown.

Methods: Consecutive patients with a CG during observation on the table after PVI were included. The PVP, FFP, and the CG location were evaluated to develop a novel algorithm to identify the CG location in the left superior pulmonary vein. The performance of this novel algorithm was prospectively tested in a validation cohort of consecutive patients undergoing repeat PVI ablation.

Results: A total of 116 patients with atrial fibrillation (AF) were recruited, 56 of whom formed the validation cohort. The interval between FFP and PVP of the left superior pulmonary vein was associated with the CG location, and an interval <5 ms predicted the presence of CG in the upper portion of the ostium with a sensitivity of 92.9% and a specificity of 96.9%. In the prospective evaluation, the interval was able to correctly predict the site of CG in 89.6% of cases.

Conclusions: The interval between FFP and PVP is a novel and accurate index that can be used to predict the CG location in the left superior pulmonary vein. An far-field atrial potential and pulmonary vein potential (FFP–PVP) interval value of ≥5 ms could be used to exclude a CG in the upper portion of the ostium in the majority of patients undergoing AF ablation.

A Magnetorheological Fluids-Based Robot-Assisted Catheter/Guidewire Surgery System for Endovascular Catheterization

A teleoperated robotic catheter operating system is a solution to avoid occupational hazards caused by repeated exposure radiation of the surgeon to X-ray during the endovascular procedures. However, inadequate force feedback and collision detection while teleoperating surgical tools elevate the risk of endovascular procedures. Moreover, surgeons cannot control the force of the catheter/guidewire within a proper range, and thus the risk of blood vessel damage will increase. In this paper, a magnetorheological fluid (MR)-based robot-assisted catheter/guidewire surgery system has been developed, which uses the surgeon’s natural manipulation skills acquired through experience and uses haptic cues to generate collision detection to ensure surgical safety. We present tests for the performance evaluation regarding the teleoperation, the force measurement, and the collision detection with haptic cues. Results show that the system can track the desired position of the surgical tool and detect the relevant force event at the catheter. In addition, this method can more readily enable surgeons to distinguish whether the proximal force exceeds or meets the safety threshold of blood vessels.

Recurrent Atrial Fibrillation After Cryoballoon Ablation: What to Expect!

Atrial fibrillation (AF) recurrence following cryoballoon ablation may occur as a consequence of pulmonary vein (PV) reconnection, which can be treated effectively by performing repeat PV isolation. Alternatively, AF recurrence can manifest in presence of bilateral antral PV isolation. In such circumstances, one may pursue catheter ablation of AF triggers, if present, or proceed with empiric posterior left atrial wall ablation. Although traditionally, focal radiofrequency ablation has been used for this, cryoballoon ablation, itself, may also be used for ablation/isolation of certain structures such as the superior vena cava, the left atrial appendage and even the posterior left atrial wall.

Automated Noncontact Ultrasound Imaging and Ablation System for the Treatment of Atrial Fibrillation

Background:

Catheter ablation for atrial fibrillation (AF) using point-by-point radiofrequency energy or single-application one-shot balloons is either technically challenging or have limited ability to accommodate variable patient anatomy to achieve acute and durable pulmonary vein (PV) isolation. A novel ablation system employs low intensity collimated ultrasound (LICU)-guided anatomic mapping and robotic ablation to isolate PVs. In this first-in-human, single-center, multioperator trial, VALUE trial (VytronUS Ablation System for Treatment of Paroxysmal Atrial Fibrillation; NCT03639597) in patients with paroxysmal atrial fibrillation, this LICU system was evaluated to determine its safety, effectiveness in PV isolation, and freedom from recurrent atrial arrhythmias.

Methods:

In the enrolled 52 patients with paroxysmal atrial fibrillation, ultrasound M-mode–based left atrial anatomies were successfully created, and ablation was performed under robotic control along an operator-defined lesion path. The LICU system software advanced over the course of the study: the last 13 patients were ablated with enhanced software.

Results:

Acute PV isolation was achieved in 98% of PVs—using LICU-only in 77.3% (153/198) of PVs and requiring touch-up with a standard radiofrequency ablation catheter in 22.7% (45/198) PVs. The touch-up rate decreased to 5.8% (3/52) in patients undergoing LICU-ablation with enhanced software. Freedom from atrial arrhythmia recurrence was 79.6% (39/49 patients) at 12 months or 92.3% (12/13 patients) with the enhanced software. Major adverse events occurred in 3 patients (5.8%): one had transient diaphragmatic paralysis, one vascular access complication, and one had transient ST-segment elevation from air-embolism, without sequelae.

Conclusions:

In this first-in-human study, low- intensity collimated ultrasound-guided anatomic mapping and robotic ablation allows PV isolation with good chronic safety; PV isolation success is improving with device enhancements.

Registration:

URL: https://www.clinicaltrials.gov ; Unique identifier: NCT03639597.

Prevalence and clinical impact of spontaneous and adenosine-induced pulmonary vein reconduction in the Contact-Force vs. Cryoballoon Atrial Fibrillation Ablation (CIRCA-DOSE) study

BACKGROUND

Use of intraprocedural observation and pharmacologic challenges have been proposed as means to differentiate permanent pulmonary vein (PV)-left atrial conduction block from inadequate ablation lesions.

OBJECTIVE

The purpose of this study was to determine the prevalence and clinical impact of spontaneous and adenosine-provoked reconnection using contemporary atrial fibrillation (AF) ablation technologies.

METHODS

The CIRCA-DOSE (Cryoballoon vs. Irrigated Radiofrequency Catheter Ablation: Double Short vs. Standard Exposure Duration) study enrolled 346 patients with paroxysmal AF and randomized them to contact force-guided radiofrequency ablation (CF-RF) or cryoballoon ablation. Patients underwent provocative testing with adenosine after a 20-minute observation period. All patients received an implantable cardiac monitor for arrhythmia monitoring.

RESULTS

Spontaneous reconnection was observed in 5.4% of PVs (71/1318) during the 20-minute postprocedure observation period, and dormant conduction was elicited in 5.7% of PVs (75/1318). Both spontaneous reconnection and dormant conduction were more common after CF-RF compared to cryoballoon ablation (P = .03 and P <.0001, respectively). Acute PV reconnection (spontaneous or adenosine-provoked) was associated with a significantly higher incidence of recurrent atrial tachyarrhythmia in the cryoballoon group (hazard ratio [HR] 2.39; 95% confidence interval [CI] 1.44-3.96; P = .0007) but not in the CF-RF group (HR 1.47; 95% CI 0.84-2.58; P = .16). In the absence of acute reconnection, the freedom from recurrent arrhythmia did not differ between groups (HR 0.95; 95% CI 0.6057-1.495; P = .83).

CONCLUSION

Patients without spontaneous or adenosine-provoked reconnection had better outcomes compared to those with acute PV reconnection, suggesting that efforts should be directed toward ensuring an ideal ablation lesion at the first attempt in order to achieve durable PV isolation.

Characteristics of early recurrences detected by continuous cardiac monitoring influencing the long-term outcome after atrial fibrillation ablation

AIMS

Early recurrences (ER) of atrial arrhythmias are common after catheter ablation of atrial fibrillation (AF). The significance of these ER is controversial. Based on data of continuous cardiac monitoring, we sought to investigate the characteristics of ER and their impact on late recurrences (LR) during follow-up.

METHODS

One hundred twenty-six patients with paroxysmal (49%) or persistent (51%) AF underwent an AF ablation with subsequent implantation of implantable loop recorder. Follow up was 12 months using remote monitoring. All atrial arrhythmia (AF or atrial tachycardia-AT-) episodes >30 seconds. within the 3-month blanking period were considered and the AF burden evaluated every 3 months.

RESULTS

Within the 3-months blanking period, 72 patients (57%) experienced an AF/AT recurrence. Survival free from any arrhythmia recurrence during follow-up was 40% in patients with ER vs 69% in those without ER. AF burden during the blanking period and timing of ER correlated significantly with LR at 12 months (area under curve = 0.74, P < .0001 and .831, P < .0001). An AF burden ≥0.5% and ER after 74 days predicted LR (sensitivity 60%, specificity 84.4%; sensitivity 75.6%, specificity 90.3%). In cox regression analysis, AF burden ≥0.5% and ER after 74 days were independently associated with LR.

CONCLUSION

Continuous cardiac monitoring after AF ablation provides important information regarding early recurrence episodes and their prognostic impact. A cut-off of 74 days for the blanking period seems to better differentiate patients with a good or a poor long-term outcome. An AF burden ≥0.5% during the 3 months postablation is predictive for late arrhythmia recurrences.

Pulmonary Vein Reconnection No Longer Occurs in the Majority of Patients After a Single Pulmonary Vein Isolation Procedure

OBJECTIVES

This study sought to determine the prevalence of patients with 4 isolated veins at repeat ablation after "CLOSE" -guided pulmonary vein isolation (PVI), a strategy based on delivery of contiguous and optimized radiofrequency lesions.

BACKGROUND

The likelihood of finding 4 isolated veins at a repeat ablation for atrial fibrillation (AF) recurrence after a first PVI is low.

METHODS

Patients undergoing repeat ablation for AF recurrence after first CLOSE-guided PVI were included. At repeat: 1) the status of the PV was evaluated; and 2) high-density voltage mapping was performed. In case of pulmonary vein reconnection (PVR), veins were reisolated. In patients with 4 isolated veins, empirical trigger or substrate ablation was performed.

RESULTS

Of 326 patients undergoing CLOSE-guided PVI for paroxysmal AF, 45 patients underwent repeat ablation for AF recurrence (11 ± 7 months after first PVI). In 28 patients, all veins were still isolated (62%). They showed similar clinical characteristics and similar time from first PVI to AF recurrence (8 ± 7 vs. 6 ± 6 months, respectively, p = 0.453) compared with patients with PVR. In contrast, they were characterized by a higher incidence of low voltage (57% vs. 17%, p = 0.033). Patients with 4 isolated veins, compared with patients treated for PVR, showed a lower 12-month freedom from AF after repeat ablation (61% vs. 88%, p = 0.045).

CONCLUSIONS

After CLOSE-guided ablation, PVR is no longer the rule in patients with AF recurrence. Patients with AF recurrence and 4 isolated veins present with a similar clinical profile and time to recurrence as patients with PVR.

A randomized clinical trial of early invasive intervention for atrial fibrillation (EARLY-AF) - methods and rationale

BACKGROUND

The ideal management of patients with newly diagnosed symptomatic atrial fibrillation (AF) remains unknown. Current practice guidelines recommend a trial of antiarrhythmic drugs (AAD) prior to considering an invasive ablation procedure. However, earlier ablation offers an opportunity to halt the progressive patho-anatomical changes associated with AF, as well as impart other important clinical benefits.

OBJECTIVE

The aim of this study is to determine the optimal initial management strategy for patients with newly diagnosed, symptomatic atrial fibrillation.

METHODS/DESIGN

The EARLY-AF study (ClinicalTrials.govNCT02825979) is a prospective, open label, multicenter, randomized trial with a blinded assessment of outcomes. A total of 298 patients will be randomized in a 1:1 fashion to first-line AAD therapy, or first-line cryoballoon-based pulmonary vein isolation. Patients with symptomatic treatment naïve AF will be included. Arrhythmia outcomes will be assessed by implantable cardiac monitor (ICM). The primary outcome is time to first recurrence of AF, atrial flutter, or atrial tachycardia (AF/AFL/AT) between days 91 and 365 following AAD initiation or AF ablation. Secondary outcomes include arrhythmia burden, quality of life, and healthcare utilization.

DISCUSSION

The EARLY-AF study is a randomized trial designed to evaluate the optimal first management approach for patients with AF. We hypothesize that catheter ablation will be superior to drug therapy in prevention of AF recurrence.

Contact force facilitates the achievement of an unexcitable ablation line during pulmonary vein isolation

AIMS

Contact force (CF) catheters provide catheter-tissue contact information to improve outcome of pulmonary vein isolation (PVI) in paroxysmal atrial fibrillation (PAF). We evaluated different target-CF values for achievement of the additional endpoint of an unexcitable ablation line.

METHODS

A total of 106 patients undergoing PVI were randomized into three groups (G) (G1: target-CF 15 g, G2: target-CF 10 g, G3: CF concealed from operator). The PVI encircling line was divided into predefined sections. Excitable tissue along the PVI-line identified by high output pacing (10 V, 2 ms) was targeted for further ablation.

RESULTS

Mean average CF was 17.4 ± 4.7 g (G1) vs. 12.3 ± 6.0 g (G2) vs. 11.1 ± 6.5 g (G 3) (p < 0.001). Primary unexcitable ablation lines were found in 38.6, 19.4 and 5.7% (G1, G2, G3 respectively; G1 vs. G2 p < 0.05, G1 vs. G3 p < 0.001, G2 vs. G3 ns). Additional radiofrequency (RF)-energy to achieve unexcitability was lowest in G1 (3.6 ± 3.1 kJ vs. 8.6 ± 7.2 kJ (G2) and 10.4 ± 6.7 (G3), p ≤ 0.001, G2 vs. G3 ns) with accordingly lowest additional RF applications in G1 (3.0 ± 2.6 vs. 7.0 ± 5.4 in G2 and 8.4 ± 4.0 in G3; G1 vs. G2 and G3, p < 0.001, G 2 vs. G 3 ns). Sections along ablation lines with low initial CF were most likely to reveal excitability. Single procedure success was 81.9 vs. 73.5 vs. 71.4% (G 1, 2 and 3, p = 0.6) during 437 ± 254 day follow-up.

CONCLUSION

Higher tip-to-tissue CF during PVI facilitates the achievement of an unexcitable ablation line, requiring less additional RF-energy.

Design and performance evaluation of collision protection-based safety operation for a haptic robot-assisted catheter operating system

The robot-assisted catheter system can increase operating distance thus preventing the exposure radiation of the surgeon to X-ray for endovascular catheterization. However, few designs have considered the collision protection between the catheter tip and the vessel wall. This paper presents a novel catheter operating system based on tissue protection to prevent vessel puncture caused by collision. The integrated haptic interface not only allows the operator to feel the real force feedback, but also combines with the newly proposed collision protection mechanism (CPM) to mitigate the collision trauma. The CPM can release the catheter quickly when the measured force exceeds a certain threshold, so as to avoid the vessel puncture. A significant advantage is that the proposed mechanism can adjust the protection threshold in real time by the current according to the actual characteristics of the blood vessel. To verify the effectiveness of the tissue protection by the system, the evaluation experiments in vitro were carried out. The results show that the further collision damage can be effectively prevented by the CPM, which implies the realization of relative safe catheterization. This research provides some insights into the functional improvements of safe and reliable robot-assisted catheter systems.

Randomised clinical trial of cryoballoon versus irrigated radio frequency catheter ablation for atrial fibrillation-the effect of double short versus standard exposure cryoablation duration during pulmonary vein isolation (CIRCA-DOSE): methods and rationale

INTRODUCTION

Pulmonary vein isolation (PVI) is an effective therapy for paroxysmal atrial fibrillation (AF), but it has limitations. The two most significant recent advances have centred on the integration of real-time quantitative assessment of catheter contact force into focal radio frequency (RF) ablation catheters and the development of dedicated ablation tools capable of achieving PVI with a single ablation lesion (Arctic Front cryoballoon, Medtronic, Minneapolis, MN, USA). Although each of these holds promise for improving the clinical success of catheter ablation of AF, there has not been a rigorous comparison of these advanced ablation technologies. Moreover, the optimal duration of cryoablation (freezing time) has not been determined.

METHODS AND ANALYSIS

Patients undergoing an initial PVI procedure for paroxysmal AF will be recruited. Patients will be randomised 1:1:1 between contact-force irrigated RF ablation, short duration cryoballoon ablation (2 min applications) and standard duration cryoballoon ablation (4 min applications). The primary outcome is time to first documented AF recurrence on implantable loop recorder. With a sample size of 111 per group and a two-sided 0.025 significance level (to account for the two main comparisons), the study will have 80% power (using a log-rank test) to detect a difference of 20% between contact force RF catheter ablation and either of the two cryoballoon ablation groups. Factoring in a 4% loss to follow-up, 116 patients per group should be randomised and followed for a year (total study population of 348).

ETHICS AND DISSEMINATION

The study was approved by the University of British Columbia Office of Research (Services) Ethics Clinical Research Ethics Board. Results of the study will be submitted for publication in a peer-reviewed journal.

TRIAL REGISTRATION NUMBER

NCT01913522; Pre-results.

Identification and Ablation of Dormant Conduction in Atrial Fibrillation Using Adenosine

BACKGROUND

Ablation is used for treatment of atrial fibrillation (AF) but recurrence is common. Dormant conduction is hypothesized to be responsible for these recurrences, and the role of adenosine in identification and ablation of these pathways is controversial with conflicting results on AF recurrence.

MATERIALS AND METHODS

We conducted a meta-analysis for studies evaluating AF ablation and adenosine use. Included in the meta-analysis were human studies that compared ablation using adenosine or adenosine triphosphate (ATP) and reported freedom from AF in patients beyond a minimum follow-up of 6 months.

RESULTS

Our analysis suggests that the use of adenosine leads to a decrease in recurrence of AF compared to the cohort which did not utilize adenosine. Subgroup analysis showed no difference in the recurrence of AF with the modality used for ablation (cryoablation vs. radiofrequency ablation) or with the preparation of adenosine used (ATP vs. adenosine). There was a significant benefit in delayed administration of ATP over early administration. Pooling results of only randomized control trials did not show any significant difference in AF recurrence.

CONCLUSIONS

Adenosine-guided identification and ablation of dormant pathways may lead to a decrease in recurrence of AF.

Redefining the Blanking Period After Catheter Ablation for Paroxysmal Atrial Fibrillation: Insights From the ADVICE (Adenosine Following Pulmonary Vein Isolation to Target Dormant Conduction Elimination) Trial

BACKGROUND

Early recurrences (ERs) of atrial tachyarrhythmia are common after catheter ablation of atrial fibrillation. A 3-month blanking period is recommended by current guidelines. This study sought to investigate the significance of ER during the first 3 months post ablation in predicting late recurrences and determine whether it varies according to timing.

METHODS AND RESULTS

A total of 401 patients with paroxysmal atrial fibrillation undergoing pulmonary vein isolation were followed for 12 months with transtelephonic monitoring in the ADVICE (Adenosine Following Pulmonary Vein Isolation to Target Dormant Conduction Elimination) trial. Patients with atrial tachyarrhythmia ≥30 s within the 3-month blanking period were stratified according to the timing of ER. A total of 179 patients (44.6%) experienced their last episode of ER during the first (n=53), second (n=44), or third (n=82) month of the 3-month blanking period. One-year freedom from symptomatic atrial tachyarrhythmia was 77.2% in patients without ER compared with 62.6%, 36.4%, and 7.8% in patients with ER 1, 2, and 3 months post ablation, respectively (P<0.0001). Receiver operating curve analyses revealed a strong correlation between the timing of ER and late recurrence (area under the curve 0.82, P<0.0001). Corresponding hazard ratios for ER during the first, second, and third months were 1.84, 4.45, and 9.64, respectively.

CONCLUSIONS

This study validates the use of a blanking period after catheter ablation for paroxysmal atrial fibrillation but calls into question the 90-day cut-off value. In particular, >90% of patients with ER during the third month post ablation experience late recurrence by 1 year. However, pending further study, repeat ablation before 90 days cannot be routinely advocated.

CLINICAL TRIAL REGISTRATION

URL: http://www.clinicaltrials.gov. Unique identifier: NCT01058980.

Clinical utility of automated ablation lesion tagging based on catheter stability information (VisiTag Module of the CARTO 3 System) with contact force-time integral during pulmonary vein isolation for atrial fibrillation

BACKGROUND

The clinical utility of an automated lesion tagging module based on catheter stability information (VisiTag) with the CARTO system during atrial fibrillation (AF) ablation remains to be established. We investigated whether VisiTag-guided extensive encircling pulmonary vein isolation (EEPVI) produces durable lesions.

METHODS

The study involved 54 patients undergoing EEPVI for paroxysmal AF. We performed EEPVI guided by the module-generated ablation tags, i.e., "VisiTags," which are point-by-point ablation tags placed on 3D maps. The patients were divided into two groups: those treated under a moderate catheter stability VisiTag setting, i.e., a 3-mm distance limit for at least 5 s and a minimum contact force (CF) of 8 g over 25 % of the set time period with a target force-time integral (FTI) ≥300 g*s (n = 27), and those treated under a strict catheter stability setting, i.e., a 3-mm distance limit for at least 10 s and a minimum CF of 10 g over 50 % of the set time period with a target FTI ≥400 g*s (n = 27).

RESULTS

After EEPVI, adenosine triphosphate-provoked dormant PV conduction was observed in six (22 %) patients in the moderate catheter stability group and in one (4 %) patient in the strict catheter stability group (p = 0.1003); the 12.9-month success rate was 81 % in both groups.

CONCLUSIONS

The strict catheter stability setting for automated lesion tagging together with a target FTI of >400 g*s, vs. the moderate catheter stability setting with a target FTI of >300 g*s, produces less frequent ATP-provoked PV conduction and yields a comparably high mid-term success rate.

Wall thickness of the pulmonary vein-left atrial junction rather than electrical information as the major determinant of dormant conduction after contact force-guided pulmonary vein isolation

PURPOSE

The usefulness of electrogram (EGM)-based information has been reported for assessing lesion transmurality during atrial fibrillation (AF) ablation, but the wall thickness of the pulmonary vein-left atrial (PV-LA) junction has not been considered. We conducted a study to evaluate the relation between PV-LA junction wall thickness and the presence of adenosine triphosphate (ATP)-provoked dormant PV conduction.

METHODS

Eighteen AF patients underwent extensive encircling pulmonary vein isolation (EEPVI) with a target CF of >10 g. RF energy was delivered point-by-point at a power setting of 25-30 W for 30 s, and EGM-based information (change in filtered unipolar EGM morphology and bipolar EGM amplitude), decrease in impedance, CF, and CT-based measurement of the PV-LA junction wall thickness were characterized at sites of ATP-provoked dormant conduction.

RESULTS

After EEPVI, ATP-induced dormant conduction was observed at 12 of the 288 PV sites (8 segments per ipsilateral PVs × 2 × 18 patients). Of the 974 ablation points, 72 were located at dormant conduction sites and were strongly associated with thickened PV-LA junction walls (1.02± 0.23 vs. 0.86 ± 0.26 mm, p < 0.0001) and decreased impedance (13.3 ± 6.4 vs. 14.9 ± 7.1 Ω, p = 0.0498) but not with EGM-based information or CF. Multivariate analysis identified the thickened PV-LA junction wall as the strongest predictor of dormant conduction.

CONCLUSIONS

A thickened PV-LA junction wall is a robust predictor of ATP-provoked dormant conduction; EGM-based information appears to be insufficient for ensuring adequate lesions during CF-guided EEPVI.

The Role of Adenosine in Pulmonary Vein Isolation: A Critical Review

The cornerstone of atrial fibrillation (AF) ablation is pulmonary vein isolation (PVI), which can be achieved in more than 95% of patients at the end of the procedure. However, AF recurrence rates remain high and are related to recovery of PV conduction. Adenosine testing is used to unmask dormant pulmonary vein conduction (DC). The aim of this study is to review the available literature addressing the role of adenosine testing and determine the impact of ablation at sites of PV reconnection on freedom from AF. Adenosine infusion, by restoring the excitability threshold, unmasks reversible injury that could lead to recovery of PV conduction. The studies included in this review suggest that adenosine is useful to unmask nontransmural lesions at risk of reconnection and that further ablation at sites of DC is associated with improvement in freedom from AF. Nevertheless it has been demonstrated that adenosine is not able to predict all veins at risk of later reconnection, which means that veins without DC are not necessarily at low risk. The role of the waiting period in the setting of adenosine testing has also been analyzed, suggesting that in the acute phase adenosine use should be accompanied by enough waiting time.

Impact of Complete Versus Incomplete Circumferential Lines Around the Pulmonary Veins During Catheter Ablation of Paroxysmal Atrial Fibrillation

Background—

Ablation of atrial fibrillation (AF) is an established treatment option for symptomatic patients. It is not known whether complete pulmonary vein isolation (PVI) is superior to incomplete PVI with regard to the patients’ clinical outcome.

Methods and Results—

Patients with drug-refractory, symptomatic paroxysmal AF were randomly assigned to either incomplete (group A) or complete PVI (group B). In group A, a persistent gap was intentionally left within the circumferential ablation line, whereas in group B, complete PVI without any gaps was intended. At 3 months, all patients underwent invasive reevaluation to assess the rate of persistent PVI. Clinical follow-up was based on daily 30-s transtelephonic ECG transmissions. Primary study end point was the time to first recurrence of (symptomatic or asymptomatic) AF. A total of 233 patients were enrolled (116 in group A and 117 in group B). AF recurrence within 3 months was observed in a total of 161 patients (136 [84.5%] with symptomatic and 25 [15.5%] with asymptomatic AF); AF recurred in 62.2% of group B patients and 79.2% of group A patients ( P <0.001), for a difference in favor of complete PVI of 17.1% (95% confidence interval, 5.3%–28.9%). Invasive restudy in 103 group A patients and 93 group B patients revealed conduction gaps in 92 (89.3%) and 65 (69.9%) patients, respectively.

Conclusions—

This study proves the superiority of complete PVI over incomplete PVI with respect to AF recurrence within 3 months. However, the rate of electric reconduction 3 months after PVI is high in patients with initially isolated PVs.

Clinical Trial Registration—

URL: http://clinicaltrials.gov ; Unique identifier: NCT00293943.

Electrophysiological Perspectives on Hybrid Ablation of Atrial Fibrillation

To overcome limitations of minimally invasive surgical ablation as a standalone procedure in eliminating atrial fibrillation (AF), hybrid approaches incorporating adjunctive endovascular catheter ablation have been proposed in recent years. The endovascular component targets residual conduction gaps and identifies additional electrophysiological targets with the goal of minimizing recurrent atrial arrhythmia. We performed a systematic review of published studies of hybrid AF ablation, analyzing 432 pooled patients (19% paroxysmal, 29% persistent, 52% long-standing persistent) treated using three different approaches: A. bilateral thoracoscopy with bipolar radiofrequency (RF) clamp-based approach; B. right thoracoscopic suction monopolar RF catheter-based approach; and C. subxiphoid posterior pericardioscopic ("convergent") approach. Freedom from recurrence off antiarrhythmic medications at 12 months was seen in 88.1% [133/151] for A, 73.4% [47/64] for B, and 59.3% [80/135] for C, with no significant difference between paroxysmal (76.9%) and persistent/long-standing persistent AF (73.4%). Death and major surgical complications were reported in 8.5% with A, 0% with B and 8.6% with C. A critical appraisal of hybrid ablation is presented, drawing from experiences and insights published over the years on catheter ablation of AF, with a discussion of the rationale underlying hybrid ablation, its strengths and limitations, where it may have a unique role in clinical management of patients with AF, which questions remain unanswered and areas for further investigation.

Adenosine-guided pulmonary vein isolation for the treatment of paroxysmal atrial fibrillation: an international, multicentre, randomised superiority trial

BACKGROUND

Catheter ablation is increasingly used to manage atrial fibrillation, but arrhythmia recurrences are common. Adenosine might identify pulmonary veins at risk of reconnection by unmasking dormant conduction, and thereby guide additional ablation to improve arrhythmia-free survival. We assessed whether adenosine-guided pulmonary vein isolation could prevent arrhythmia recurrence in patients undergoing radiofrequency catheter ablation for paroxysmal atrial fibrillation.

METHODS

We did this randomised trial at 18 hospitals in Australia, Europe, and North America. We enrolled patients aged older than 18 years who had had at least three symptomatic atrial fibrillation episodes in the past 6 months, and for whom treatment with an antiarrhythmic drug failed. After pulmonary vein isolation, intravenous adenosine was administered. If dormant conduction was present, patients were randomly assigned (1:1) to additional adenosine-guided ablation to abolish dormant conduction or to no further ablation. If no dormant conduction was revealed, randomly selected patients were included in a registry. Patients were masked to treatment allocation and outcomes were assessed by a masked adjudicating committee. Patients were followed up for 1 year. The primary outcome was time to symptomatic atrial tachyarrhythmia after a single procedure in the intention-to-treat population. The trial is registered with ClinicalTrials.gov, number NCT01058980.

FINDINGS

Adenosine unmasked dormant pulmonary vein conduction in 284 (53%) of 534 patients. 102 (69·4%) of 147 patients with additional adenosine-guided ablation were free from symptomatic atrial tachyarrhythmia compared with 58 (42·3%) of 137 patients with no further ablation, corresponding to an absolute risk reduction of 27·1% (95% CI 15·9-38·2; p<0·0001) and a hazard ratio of 0·44 (95% CI 0·31-0·64; p<0·0001). Of 115 patients without dormant pulmonary vein conduction, 64 (55·7%) remained free from symptomatic atrial tachyarrhythmia (p=0·0191 vs dormant conduction with no further ablation). Occurrences of serious adverse events were similar in each group. One death (massive stroke) was deemed probably related to ablation in a patient included in the registry.

INTERPRETATION

Adenosine testing to identify and target dormant pulmonary vein conduction during catheter ablation of atrial fibrillation is a safe and highly effective strategy to improve arrhythmia-free survival in patients with paroxysmal atrial fibrillation. This approach should be considered for incorporation into routine clinical practice.

FUNDING

Canadian Institutes of Health Research, St Jude Medical, Biosense-Webster, and M Lachapelle (Montreal Heart Institute Foundation).

Contact force threshold for permanent lesion formation in atrial fibrillation ablation: A cardiac magnetic resonance-based study to detect ablation gaps

BACKGROUND

Catheter contact force (CF) has a strong correlation with lesion formation during radiofrequency ablation. Delayed-enhancement cardiac magnetic resonance (DE-CMR) provides lesion information in patients with prior atrial fibrillation (AF) ablation.

OBJECTIVE

The aim of this study was to determine the CF threshold to create permanent lesions detected by DE-CMR.

METHODS

A total of 36 patients referred for AF ablation were included. A CF catheter was used during the ablation procedure, and DE-CMR was performed 3 months after the ablation procedure. Eighteen pulmonary vein (PV) segments were defined, and 3-dimensional (3D) reconstructions of the left atrium (LA) derived from the DE-CMR images were obtained. One observer evaluated the presence of any discontinuity of previous ablation lesions (gap) in the 3D reconstructions of the LA, and another observer (blinded to the gap findings) determined the minimum CF value in each PV segment.

RESULTS

The PV segments where a gap was observed had a lower maximal CF value than did the segments without gap in the 3D LA reconstructions (6.7 ± 4.4 g vs 12.2 ± 4.7 g; P < .001). In receiver operating characteristic analysis, a CF threshold of >8 g provided 73% sensitivity and 81% specificity in the prediction of a complete PV lesion (positive predictive value [PPV] 84%). A CF threshold of >12 g had a specificity of 94% and increased the PPV to 91% in creating a complete lesion in the LA wall (area under the curve 0.834).

CONCLUSION

A CF threshold of >12 g H5H20 predicts a complete lesion with high specificity and PPV when a dragging ablation strategy is used in AF ablation.

Experience matters: long-term results of pulmonary vein isolation using a robotic navigation system for the treatment of paroxysmal atrial fibrillation

BACKGROUND

Long-term results after circumferential pulmonary vein isolation (CPVI) for the treatment of paroxysmal atrial fibrillation (PAF) using a robotic navigation system (RNS) have not yet been reported.

OBJECTIVE

To evaluate long-term results of patients with PAF after CPVI using RNS.

METHODS

In this study, 200 patients (n = 151 (75.5%) male; median age 62.2 (54.7-67.7) years) with PAF were evaluated. In 100 patients, RNS (RN-group) was used for CPVI and compared to 100 manually ablated control patients (MN-group). Radiofrequency was used in conjunction with 3D electroanatomic mapping. Power was limited to 30 watts (W) at the posterior left atrial (LA) wall in the first 49 RNS patients (RN-group-a). After esophageal perforation occurred in one RN-group-a patient, maximum power was reduced to 20 W for the subsequent 51 patients (RN-group-b).

RESULTS

After a median follow-up of 2 years, single (77/100 vs 77/100, p = 0.89) and multiple (90/100 vs 93/100, p = 0.29) procedure success rates were comparable between RN-group and MN-group. Single procedure success rate was significantly lower in RN-group-a as compared to RN-group-b (65.3 vs 88.2%, p = 0.047). In RN-group-a patients, procedural times [200 (170-230) vs 152 (132-200) minutes, p < 0.01] and fluoroscopy times [16.6 (12.9-21.6) minutes vs 13.7 (9.5-19) minutes, p = 0.043] were significantly longer compared to RN-group-b patients.

CONCLUSION

Long-term success rate after CPVI using RNS was comparable to manual ablation. Despite a lower power limit of 20 W at the posterior LA wall, single procedure success rate was higher in RN-group-b as compared to RN-group-a. Procedure time and fluoroscopy time decreased, whilst success rate increased with increasing experience in the RN-group.

Comparison of contact force-guided procedure with non-contact force-guided procedure during left atrial mapping and pulmonary vein isolation: impact of contact force on recurrence of atrial fibrillation

BACKGROUND

The aim of this study was to evaluate the impact of contact force (CF) visualization on the incidence of low and high CF during left atrial (LA) mapping and pulmonary vein isolation (PVI).

METHODS

CF was assessed in 70 patients who underwent PVI. Three highly experienced operators performed all procedures. The operators were blinded to CF in group A (35 patients), and CF was displayed in group B (35 patients). In group B, optimal CF was defined as mean CF between 10 and 39g, and operators attempted to acquire points and ablate within this range.

RESULTS

A total of 8401 mapping points were analyzed during LA mapping (group A: 4104, group B: 4297). Low CF <10g and high CF ≥40g were noted in a significantly larger number of points in group A (37.7 vs. 12.0 %, P < 0.001; 11.5 vs. 1.5 %, P < 0.001). At the mitral isthmus and ridge areas, CF was significantly lower (7.7 vs. 12.2g, P < 0.001; 5.3 vs. 11.7g, P < 0.001) in group A than in group B. PVI was successfully achieved in all patients. There were significant site-dependent CF differences between the two groups. Optimal CF was achieved in significantly more applications in group B (P < 0.001). There was no significant difference in atrial fibrillation (AF) recurrence rates after a minimum follow-up of 1 year between the two groups in this cohort (P = 0.24). No significant peri-procedural complications occurred in either group.

CONCLUSIONS

CF visualization can assist in avoiding both low and high CF, which may have the potential to improve lesion formation and patient safety profile. In this study, CF-guided ablation did not affect AF recurrence.

Unmasking the dormant pulmonary vein conduction with adenosine administration after pulmonary vein isolation with laser energy

AIMS

The isolation of the pulmonary veins (PVs) is the mainstay of atrial fibrillation (AF) ablation, which with current ablation techniques can be achieved in almost all cases. Reconnection of PVs constitutes the most frequent cause of AF recurrence. Visually guided laser balloon ablation (VGLA) is a novel system with very high rate of persistence of pulmonary vein isolation (PVI) three months after the first procedure shown in preclinical and clinical studies. We aimed to determine the acute efficiency of the laser energy during PVI with the help of adenosine provocation.

METHODS AND RESULTS

Twenty-six patients (19 male; mean age 64 ± 9 years) with symptomatic paroxysmal AF were included in the study. Pulmonary vein isolation was performed using the VGLA system. After successful PVI, we studied the effects of intravenous adenosine (18 mg) on activation of each PV at least 20 min after PVI. A total of 104 PVs were targeted. The balloon catheter could not be placed in two PVs. Of the remaining 102 PVs 99 (97% of the ablated PVs) could be successfully isolated. Adenosine was administered for each isolated PV in 25 patients. Only six PVs (6.7%) in five patients (20%) showed a PV reconnection during adenosine provocation.

CONCLUSION

Pulmonary vein isolation with VGLA is a feasible technique for PVI with a very effective acute lesion formation. The clinical significance of this low reconnection rate has to be determined.

Impact of biatrial defragmentation in patients with paroxysmal atrial fibrillation: results from a randomized prospective study

BACKGROUND

Single procedure success rates of pulmonary vein isolation (PVI) in patients with paroxysmal atrial fibrillation (PAF) are still unsatisfactory. In patients with persistent atrial fibrillation (AF), ablation of complex fractionated atrial electrograms (CFAEs) after PVI results in improved outcomes.

OBJECTIVE

We aimed to investigate if PAF-patients with intraprocedurally sustained AF after PVI might benefit from additional CFAE ablation.

METHODS

A total of 1134 consecutive patients underwent a first catheter ablation procedure of PAF between June 2008 and December 2012. In most patients, AF was either not inducible or terminated during PVI. In 68 patients (6%), AF sustained after successful PVI. These patients were randomized to either cardioversion (PVI-alone group; n = 33) or additional CFAE ablation (PVI+CFAE group; n = 35) and followed up every 1-3 months and serial Holter recordings were also obtained. The primary end point was the recurrence of AF/atrial tachycardia (AT) after a blanking period of 3 months.

RESULTS

Procedure duration (127 ± 6 minutes vs 174 ± 10 minutes), radiofrequency application time (44 ± 3 minutes vs 74 ± 5 minutes), and fluoroscopy time (26 ± 2 minutes vs 41 ± 3 minutes) were longer in the PVI+CFAE group (all P < .001). In 30 of 35 patients (86%) in the PVI+CFAE group, ablation terminated AF. There was no significant group difference with respect to freedom from AF/AT (22 of 33 [67%] vs 22 of 35 [63%]; P = .66). Subsequently, 10 of 11 patients in the PVI-alone group (91%) and 11 of 13 patients in PVI+CFAE group (85%) underwent repeat ablation (P = 1.00). Overall, 29 of 33 [88%] vs 30 of 35 [86%] patients (P = 1.00) were free from AF/AT after 1.4 ± 0.1 vs 1.4 ± 0.2 (P = .87) procedures.

CONCLUSION

Patients with sustained AF after PVI in a PAF cohort are rare. Regarding AF/AT recurrence, these patients did not benefit from further CFAE ablation compared to PVI alone, but are exposed to longer procedure duration, fluoroscopy time, and radiofrequency application time.

THERMOCOOL® SMARTTOUCH® CATHETER - The Evidence So Far for Contact Force Technology and the Role of VISITAG™ MODULE

Catheter ablation has become an important modality in the treatment of most cardiac arrhythmias. In recent years there has been significant development of new ablation energies and technologies in an attempt to improve clinical outcomes and decrease disease burden. Ablation failure is often associated with inadequate lesion formation, and catheter-to-myocardial contact force (CF) and catheter stability are two of the parameters required to produce effective lesions during radiofrequency energy application. Recently, CF sensing catheters and tagging modules have been developed to give operators realtime data on catheter force and stability. This review describes the novel THERMOCOOL(®) SMARTTOUCH(®) CATHETER (Biosense Webster Inc., CA, US) and VISITAG™ MODULE (Biosense Webster Inc., CA, US) software, and discusses the results of several studies on CF and catheter stability during mapping and ablation of the left atrium and ventricle from our electrophysiology laboratory. We assess the short- and longer-term outcomes during mapping and ablation with and without CF data, as well as the use of the VISITAG MODULE™ software, which allows the evaluation of multiple parameters of lesion formation, then integrates and displays this as automatic tags in a relatively objective way.

The comparison between robotic and manual ablations in the treatment of atrial fibrillation: a systematic review and meta-analysis

Objective

To examine in what aspects and to what extent robotic ablation is superior over manual ablation, we sought to design a meta-analysis to compare clinical outcomes between the two ablations in the treatment of atrial fibrillation.

Methods and Results

A literature search was conducted of PubMed and EMBASE databases before December 1, 2013. Data were extracted independently and in duplicate from 8 clinical articles and 792 patients. Effect estimates were expressed as weighted mean difference (WMD) or odds ratio (OR) and the accompanied 95% confidence interval (95% CI). Pooling the results of all qualified trials found significant reductions in fluoroscopic time (minutes) (WMD; 95% CI; P: -8.9; -12.54 to -5.26; <0.0005) and dose-area product (Gy×cm²) (WMD; 95% CI; P: -1065.66; -1714.36 to -416.96; 0.001) for robotic ablation relative to manual ablation, with evident heterogeneity (P<0.0005) and a low probability of publication bias. In subgroup analysis, great improvement of fluoroscopic time in patients with robotic ablation was consistently presented in both randomized and nonrandomized clinical trials, particularly in the former (WMD; 95% CI; P: -12.61; -15.13 to -10.09; <0.0005). Success rate of catheter ablation was relatively higher in patients with robotic ablation than with manual ablation (OR; 95% CI; P: 3.45; 0.24 to 49.0; 0.36), the difference yet exhibiting no statistical significance.

Conclusions

This study confirmed and extended previous observations by quantifying great reductions of fluoroscopic time and dose-area product in patients referred for robotic ablation than for manual ablation in the treatment of atrial fibrillation, especially in randomized clinical trials.