Differential pacing for distinguishing block from persistent conduction through an ablation line

Differential Pacing Maneuver From the Vein of Marshall

BACKGROUND

Bidirectional mitral isthmus (MI) block is conventionally verified by differential pacing from the coronary sinus (CS) and its sequence change. This study aimed to evaluate the ability of differential pacing from the vein of Marshall (VOM) to detect epicardial MI connections.

METHODS

Radiofrequency and VOM ethanol MI ablation were performed with a VOM electrode catheter inserted to the septal side of the ablation line. MI block was verified using conventional CS pacing. To perform differential VOM pacing analysis, initial pacing was delivered from a distal VOM bipole closer to the block line, and then from a proximal VOM bipole. The intervals from pacing stimulus during different VOM pacing sites to the electrogram recorded through the CS catheter on the opposite side of the line were compared. When the interval during distal VOM pacing was longer than that during proximal VOM pacing, it indicated a VOM connection block; however, if the former interval was shorter, the connection through the VOM was considered persistent.

RESULTS

Overall, 50 patients were evaluated. According to CS pacing, MI ablation was incomplete in 9 patients, in whom the analysis indicated persistent VOM connection. Among 41 patients with complete MI block, confirmed by CS finding, in 30 (73%) patients, the interval during distal VOM pacing was longer than that during proximal VOM pacing by 11±5 ms. However, in 11 patients (27%) the former interval was revealed to be shorter than the latter by 16±8 ms, indicating residual VOM connection. Conduction time across the line was significantly shorter in 11 patients than in the other 30 (166±21 versus 197±36 ms; P<0.01). Ten successful reevaluated analyses after VOM ethanol and further radiofrequency ablation of the connection indicated VOM block achievement.

CONCLUSIONS

Differential VOM pacing maneuver reflects the VOM conduction status. This maneuver can uncover residual epicardial connections that are missing with CS pacing.

Identification of Human Ventricular Tachycardia Demarcated by Fixed Lines of Conduction Block in a 3-Dimensional Hyperboloid Circuit

BACKGROUND

The circuit boundaries for reentrant ventricular tachycardia (VT) have been historically conceptualized within a 2-dimensional (2D) construct, with their fixed or functional nature unresolved. This study aimed to examine the correlation between localized lines of conduction block (LOB) evident during baseline rhythm with lateral isthmus boundaries that 3-dimensionally constrain the VT isthmus as a hyperboloid structure.

METHODS

A total of 175 VT activation maps were correlated with isochronal late activation maps during baseline rhythm in 106 patients who underwent catheter ablation for scar-related VT from 3 centers (42% nonischemic cardiomyopathy). An overt LOB was defined by a deceleration zone with split potentials (≥20 ms isoelectric segment) during baseline rhythm. A novel application of pacing within deceleration zone (≥600 ms) was implemented to unmask a concealed LOB not evident during baseline rhythm. LOB identified during baseline rhythm or pacing were correlated with isthmus boundaries during VT.

RESULTS

Among 202 deceleration zones analyzed during baseline rhythm, an overt LOB was evident in 47%. When differential pacing was performed in 38 deceleration zones without overt LOB, an underlying concealed LOB was exposed in 84%. In 152 VT activation maps (2D=53, 3-dimensional [3D]=99), 69% of lateral boundaries colocalized with an LOB in 2D activation patterns, and the depth boundary during 3D VT colocalized with an LOB in 79%. In VT circuits with isthmus regions that colocalized with a U-shaped LOB (n=28), the boundary invariably served as both lateral boundaries in 2D and 3D. Overall, 74% of isthmus boundaries were identifiable as fixed LOB during baseline rhythm or differential pacing.

CONCLUSIONS

The majority of VT circuit boundaries can be identified as fixed LOB from intrinsic or paced activation during sinus rhythm. Analysis of activation while pacing within the scar substrate is a novel technique that may unmask concealed LOB, previously interpreted to be functional in nature. An LOB from the perspective of a myocardial surface is frequently associated with intramural conduction, supporting the existence of a 3D hyperboloid VT circuit structure. Catheter ablation may be simplified to targeting both sides around an identified LOB during sinus rhythm.

Ablation of CTI-dependent flutter using different ablation technologies: acute and long-term outcome from the LEONARDO study

BACKGROUND

A novel ablation catheter has been released to map and ablate the cavo-tricuspid isthmus (CTI) in patients with atrial flutter (AFL), improving ablation efficiency.

METHODS

We evaluated the acute and long-term outcome of CTI ablation aiming at bidirectional conduction block (BDB) in a prospective, multicenter cohort study enrolling 500 patients indicated for typical AFL ablation. Patients were grouped on the basis of the AFL ablation method (linear anatomical approach, Conv group n = 425, or maximum voltage guided, MVG group, n = 75) and ablation catheter (mini-electrodes technology, MiFi group, n = 254, or a standard 8-mm ablation catheter, BLZ group, n = 246).

RESULTS

Complete BDB according to both validation criteria (sequential detailed activation mapping or mapping only the ablation site) was achieved in 443 patients (88.6%). The number of RF applications needed to achieve BDB was lower in the MiFi MVG group vs both the MiFi Conv group and the BLZ Conv group (3.2 ± 2 vs 5.2 ± 4 vs 9.3 ± 5, p < 0.0001 for all comparisons). Fluoroscopy time was similar among groups, whereas we observed a reduction in the procedure duration from the BLZ Conv group (61.9 ± 26min) to the MiFi MVG group (50.6 ± 17min, p = 0.048). During a mean follow-up of 548 ± 304 days, 32 (6.2%) patients suffered an AFL recurrence. No differences were found according to BDB achieved by both validation criteria.

CONCLUSIONS

Ablation was highly effective in achieving acute CTI BDB and long-term arrhythmia freedom irrespective of the ablation strategy or the validation criteria for CTI chosen by the operator. The use of an ablation catheter equipped with mini-electrodes technology seems to improve ablation efficiency.

CLINICAL TRIAL REGISTRATION

Atrial Flutter Ablation in a Real World Population. (LEONARDO).

CLINICALTRIALS

gov Identifier: NCT02591875.

Anterior mitral line in patients with persistent atrial fibrillation and anterior scar: A multicenter matched comparison-The MiLine study

BACKGROUND

The benefit of an anterior mitral line (AML) in patients with persistent atrial fibrillation (AF) and anterior atrial scar undergoing ablation has never been investigated.

OBJECTIVE

The purpose of this study was to evaluate the outcomes of AML in addition to standard treatment compared to standard treatment alone (no AML) in this subset of patients.

METHODS

Patients with persistent AF and anterior low-voltage zone (LVZ) treated with AML in 3 centers were retrospectively enrolled. The patients were matched in 1:1 fashion with patients having persistent AF and anterior LVZ who underwent conventional ablation in the same centers. Matching parameters were age, LVZ burden, and repeated ablation. Primary endpoint was AF/atrial tachycardia (AT) recurrence.

RESULTS

One hundred eight-six patients (age 66 ± 9 years; 34% women) were selected and divided into 2 matched groups. Bidirectional conduction block was achieved in 95% of AML. After median follow-up of 2 years, AF/AT recurrence occurred in 29% of the patients in the AML group vs 48% in the no AML group (log-rank P = .024). On Cox regression multivariate analysis, left atrial volume (hazard ratio [HR] 1.03; P = .006) and AML (HR 0.46; P = .003) were significantly associated with the primary endpoint. On univariate logistic regression, lower body mass index, older age, extensive anterior LVZ, and position of the left atrial activation breakthrough away from the AML were associated with first-pass AML block.

CONCLUSION

In this retrospective matched analysis of patients with persistent AF and anterior scar, AML in addition to standard treatment was associated with improved AF/AT-free survival compared to standard treatment alone.

Confirmation of the achievement of linear lesions using "activation vectors" based on omnipolar technology

BACKGROUND

Although differential pacing conventionally has been used to confirm the achievement of block across linear lesion sets, high-resolution mapping demonstrates that pseudo-block is observed in 20%-30% of cases.

OBJECTIVES

The purpose of this study was to examine the reliability and versatility of a method using "activation vectors" based on omnipolar technology to confirm the block line.

METHODS

Linear ablation was performed during pacing, with the HD Grid catheter (Abbott) placed beside the linear lesion opposite the pacing site. The endpoint of complete linear lesion was complete inversion of the activation vectors to the opposite direction. When inversion of the activation vectors was not observed after 10 minutes of radiofrequency (RF) application, high-resolution mapping was performed to assess whether complete block was achieved.

RESULTS

In 33 patients, 24 cavotricuspid isthmus lines, 11 mitral isthmus (MI) lines, 16 posterior lines, and 2 intercaval lines were performed using this method. Of the total of 53 lines, 10 (18.9%) required intermediate evaluation of the block line with high-resolution mapping because of the absence of inversion of activation vectors despite 10 minutes of RF application, resulting in incomplete block with endocardial gaps or epicardial conductions. Additional RF applications finally achieved inversion in direction of activation vectors in the 10 lines. In total, the present method can diagnose achievement of complete block line with 100% accuracy, whereas conventional differential pacing misdiagnosed incomplete block with epicardial conduction in posterior lines in 3 cases and in MI lines in 2 cases.

CONCLUSION

Confirmation of complete linear lesions using "activation vectors" based on omnipolar technology is a reliable and versatile method.

Local impedance measurements during contact force-guided cavotricuspid isthmus ablation for predicting an effective radiofrequency ablation

Background

An ablation catheter capable of contact force (CF) and local impedance (LI) monitoring (IntellaNav StablePoint, Boston Scientific) has been recently launched. We evaluated the relationship between the CF and LI values during radiofrequency catheter ablation (RFCA) along the cavotricuspid isthmus (CTI).

Methods

Fifty consecutive subjects who underwent a CTI-RFCA using IntellaNav StablePoint catheters were retrospectively studied. The initial CF and LI at the start of the RF applications and mean CF and minimum LI during the RF applications were measured. The absolute and percentage LI drops were calculated as the difference between the initial and minimum LIs and 100 × absolute LI drop/initial LI, respectively.

Results

We analyzed 602 first-pass RF applications. A weak correlation was observed between the initial CF and LI (r = 0.13) and between the mean CF and LI drops (r = 0.22). The initial LI and absolute and percentage LI drops were greater at effective ablation sites than ineffective ablation sites (median, 151 vs. 138 Ω, 22 vs. 14 Ω, and 14.4% vs. 9.9%; p < .001), but the initial and mean CF did not differ. At optimal cutoffs of 21 Ω and 10.8% for the absolute and percentage LI drops according to the receiver-operating characteristic analysis, the sensitivity, and specificity for predicting an effective ablation were 57.4% and 88.9% and 80.0%, and 61.1%, respectively.

Conclusions

The effective sites during the CF-guided CTI-RFCA had greater initial LI and LI drops than the ineffective sites. Absolute and percentage LI drops of 21 Ω and 10.8% may be appropriate targets for an effective ablation.

Cavotricuspid isthmus ablation guided by force-time integral - A randomized study

Background

Force‐time integral (FTI) is an ablation marker of lesion quality and transmurality. A target FTI of 400 gram‐seconds (gs) has been shown to improve durability of pulmonary vein isolation, following atrial fibrillation ablation. However, relevant targets for cavotricuspid isthmus (CTI) ablation are lacking.

Hypothesis

We sought to investigate whether CTI ablation with 600 gs FTI lesions is associated with reduced rate of transisthmus conduction recovery compared to 400 gs lesions.

Methods

Fifty patients with CTI‐dependent flutter were randomized to ablation using 400 gs (FTI400 group, n = 26) or 600 gs FTI lesions (FTI600 group, n = 24). The study endpoint was spontaneous or adenosine‐mediated recovery of transisthmus conduction, after a 20‐min waiting period.

Results

The study endpoint occurred in five patients (19.2%) in group FTI400 and in four patients (16.7%) in group FTI600, p = .81. First‐pass CTI block was similar in both groups (50% in FTI400 vs. 54.2% in FTI600, p = .77). There were no differences in the total number of lesions, total ablation time, procedure time and fluoroscopy duration between the two groups. There were no major complications in any group. In the total population, patients not achieving first‐pass CTI block had significantly higher rate of acute CTI conduction recovery, compared to those with first‐pass block (29.2% vs. 7.7% respectively, p = .048).

Conclusions

CTI ablation using 600 gs FTI lesions is not associated with reduced spontaneous or adenosine‐mediated recurrence of transisthmus conduction, compared to 400 gs lesions.

Ablation index-guided cavotricuspid isthmus ablation with contiguous lesions using fluoroscopy integrated 3D mapping in atrial flutter

PURPOSE

The feasibility and safety of cavotricuspid isthmus (CTI) ablation with contiguous lesions using ablation index (AI) under the guidance of fluoroscopy integrated 3D mapping (CARTO UNIVU/CU) in typical atrial flutter (AFL) remains uncertain. This study aimed to determine the efficacy of AI-guided CTI ablation with contiguous lesions in patients with AFL.

METHODS

In this single-center, prospective, non-randomized, single-arm, observational study, procedural outcomes were determined in 151 patients undergoing AI-guided CTI ablation (AI group) with a target AI value of 450 and an interlesion distance of ≤ 4 mm under CU guidance. These outcomes were compared with those of 30 patients undergoing non-AI-guided ablation (non-AI group).

RESULTS

Among 151 patients, first-pass conduction block was achieved in 120 (80%) patients in the AI group (67% in the non-AI group, P = 0.152) with a shorter fluoroscopy time of 0.2 ± 0.4 min (1.7 ± 2.0 min in the non-AI group, P < 0.001). Conduction gaps were located at the atrial aspects near the inferior vena cava in 24 of 31 (78%) patients without first-pass conduction block. The AI group received 11 ± 5 (12 ± 4 in the non-AI group, P = 0.098) radiofrequency (RF) applications, and the RF time was 4.2 ± 2.4 (5.1 ± 2.5 min in the non-AI group, P = 0.011). Despite the occurrence of steam pop in 3 (2%) patients, none of them developed cardiac tamponade. No patients had recurrence within 6 months of follow-up.

CONCLUSIONS

AI-guided CTI ablation in combination with CU was feasible and effective in reducing radiation exposure in patients with AFL.

Stepwise endo-/epicardial catheter ablation for atrial fibrillation: The Mediterranea approach

BACKGROUND

Outcomes of catheter ablation (CA) among patients with nonparoxysmal atrial fibrillation (AF) are largely disappointing.

OBJECTIVE

We sought to evaluate the feasibility, effectiveness, and safety of a single-stage stepwise endo-/epicardial approach in patients with persistent/longstanding-persistent AF.

METHODS

We enrolled 25 consecutive patients with symptomatic persistent (n = 4) or longstanding-persistent (n = 21) AF and at least one prior endocardial procedure, who underwent CA using an endo-/epicardial approach. Our anatomical stepwise protocol included multiple endocardial as well as epicardial (Bachmann's bundle [BB] and ligament of Marshall ablations) components, and entailed ablation of atrial tachycardias emerging during the procedure. The primary outcome was freedom from any AF/atrial tachycardia episode after a 3-month blanking period. The secondary outcome was patients' symptom status during follow-up.

RESULTS

The stepwise endo-/epicardial approach allowed sinus rhythm restoration in 72% of patients, either directly (n = 6, 24%) or after AF organization into atrial tachycardia (n = 12, 48%). BB's ablation was commonly implicated in arrhythmia termination. After a median follow-up of 266 days (interquartile range, 96 days), survival free from AF/atrial tachycardia was 88%. Antiarrhythmic drugs could be discontinued in 22 patients (88%). As compared to baseline, more patients were asymptomatic at 9-month follow-up (0% vs. 56%, p = .02). Five patients (20%) developed mild medical complications, whereas one subject (4%) had severe kidney injury requiring dialysis.

CONCLUSION

A single-stage endo-/epicardial CA resulted in favorable rhythm and symptom outcomes in a cohort of patients with symptomatic persistent/longstanding-persistent AF and one or more prior endocardial procedures. Epicardial ablation of BB was commonly implicated in procedural success.

Extended early meets late for assessment of conduction block along an ablation line

PURPOSE

The purpose of the study was to investigate the usefulness of the extended early meets late (EEML) feature of the HD Coloring software for confirmation of bidirectional block along an ablation line.

METHODS

A single-center prospective observational study of consecutive patients with atypical atrial flutter or persistent atrial fibrillation submitted to catheter ablation including linear lesions from January 2019 to June 2020, with confirmation of bidirectional block across ablation lines assessed with the feature EEML and a multipolar catheter was conducted. Patients were divided into two groups - those with versus those without bidirectional block - and different EEML thresholds were analyzed to assess which one had the better sensitivity and specificity to predict block.

RESULTS

During the 24-month enrollment period, a total of 94 patients were included (50% males, mean age of 64 ± 10 years, 60% with structural heart disease) - 55 patients with versus 39 patients without confirmed a bidirectional block. Activation maps were performed during atrial pacing, with a median number of 1340 (interquartile range 1135-2060) points acquired in 11 ± 3 min, and a mean mapped cycle length of 287 ± 51 ms. The EEML feature was highly useful in detecting bidirectional block along ablation lines, with a 25% threshold value showing the highest discriminative performance (area under the curve of 0.93), 95% sensitivity and 92% specificity in predicting block.

CONCLUSIONS

The EEML feature of the HD Coloring software is a useful addition to the CARTO mapping system for assessment of block across an ablation line. The threshold value of 25% is the most accurate.

A simplified differential pacing technique for the evaluation of bidirectional cavo-tricuspid isthmus block during ablation of typical atrial flutter

PURPOSE

Bidirectional block of the cavo-tricuspid isthmus (CTI) is an established endpoint of CTI-dependent atrial flutter (AFl) ablation. Differential pacing has been used to evaluate the CTI block. The purpose of this study is to describe a modified differential pacing technique to evaluate the CTI block.

METHODS

Sixty-two patients underwent radiofrequency (RF) ablation of CTI-dependent AFl. The acute endpoints were non-inducibility of the AFl, and verification of the bidirectional CTI block by our methodology. Pacing was performed in the CS with an ablation catheter positioned immediately lateral to the CTI ablation line, and then 1-2 cm more laterally. The stimulus-to-ablation catheter atrial electrogram intervals were measured at these sites (Stim_CS-Abl₁ and Stim_CS-Abl₂, respectively). Pacing with the ablation catheter also was performed at these 2 sites, and the stimulus-to-CS electrogram intervals (Stim_ABL1-CS and Stim_ABL2-CS) were measured. The criteria for the bidirectional block were Stim_CS-Abl₁ > Stim_CS-Abl₂, and Stim_ABL1-CS > Stim_ABL2-CS. Clinical efficacy was defined as freedom from recurrent AFl during follow-up.

RESULTS

Following 12.2 ± 3.7 min of RF delivery across the CTI, intervals were Stim_CS-Abl₁ = 181.2 ± 22.7 ms and Stim_ABL1-CS = 181.0 ± 23.6 ms, and Stim_CS-Abl₂ = 152.2 ± 26.5 ms and Stim_ABL2-CS = 151.2 ± 22.7 (P < 0.001). Atrial flutter was rendered not inducible in all patients, and no procedural complications were encountered. During the next 15.9 ± 0.7 months, two patients were lost to follow-up, and among the 62 other patients, one (1.7%) had flutter recurrence.

CONCLUSIONS

The bidirectional CTI block can be assessed quickly and easily using only the ablation and CS catheters for differential pacing.

Definition of success criteria for ablation of typical right atrial flutter with a single-catheter approach: A pilot study

BACKGROUND

The success rate of cavotricuspid isthmus ablation to treat right common flutter is high (up to 95%), but needs bidirectional block confirmation, requiring two or three catheters.

AIM

To describe a new pacing technique using a single catheter to ablate and confirm cavotricuspid isthmus block with differential PR interval measurements.

METHODS

We included 61 patients from five centres, who were referred for cavotricuspid isthmus ablation. All patients had cavotricuspid isthmus ablation, and the cavotricuspid isthmus block was confirmed by differential pacing using two or three catheters. The new method consisted of measuring the PR interval on the surface electrocardiogram using pacing from the tip of the ablation catheter on the lateral side (lateral delay) and the septal side (coronary sinus ostium) of the cavotricuspid isthmus line (difference=delta PR interval), before and after cavotricuspid isthmus ablation. We analysed the value of the delta PR interval in predicting bidirectional cavotricuspid isthmus block as confirmed by standard methods.

RESULTS

Among our patient population (mean age 63±12 years), 39 patients were ablated during sinus rhythm, and 22 during common flutter. Cavotricuspid isthmus block was achieved in all patients but one. Lateral delay and delta PR interval increased significantly after validation of cavotricuspid isthmus block (257±42 vs. 318±50ms and 32±23 vs. 96±22ms, respectively; P<0.0001). A delta PR interval cut-off of ≥70ms had 100% sensitivity and specificity to predict bidirectional cavotricuspid isthmus block.

CONCLUSIONS

A single-catheter ablation approach to performing cavotricuspid isthmus line based on surface electrocardiogram PR interval measurement is feasible. After ablation, cavotricuspid isthmus block was systematically obtained when the delta PR interval was>70ms.

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

PURPOSE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Conduction Recovery After Cavotricuspid Isthmus Ablation When Performed With or Without Concomitant Atrial Fibrillation Ablation

OBJECTIVES

This study sought to define the association between conduction recovery across the cavotricuspid isthmus (CTI) and typical atrial flutter (AFL) recurrence when CTI ablation is performed with pulmonary vein isolation (PVI) compared with a stand-alone procedure.

BACKGROUND

CTI ablation is commonly performed at the same time as PVI to treat AFL or as an empiric therapy. Conduction recovery is a recognized problem after linear ablation in the left atrium (e.g., mitral isthmus ablation) and is proarrhythmic. Less is known about conduction recovery after CTI ablation and possible differences in outcomes when performed at the time of PVI compared with at the time of a stand-alone procedure.

METHODS

Eligible participants who underwent stand-alone CTI ablation were compared with those who underwent a combined (CTI+PVI) procedure. CTI conduction recovery was assessed at the time of a second ablation. Conduction recovery across the CTI (primary outcome) and recurrence of typical AFL (secondary outcome) were studied using multivariable logistic regression.

RESULTS

Among 295 eligible participants (median age: 64 years [interquartile range: 55 to 69 years]; 33% women), recovery was assessed in 232 and was more common after combined versus stand-alone CTI ablation (52% [72 of 139] vs. 13% [12 of 93]; p < 0.001). In multivariable analysis, CTI ablation performed as a combined procedure increased odds of CTI conduction recovery 7.8-fold (odds ratio: 7.8; 95% confidence interval: 3.3 to 18.3; p < 0.001) and clinical AFL recurrence 4.1-fold (odds ratio: 4.1; 95% confidence interval: 1.0 to 16.9; p = 0.049).

CONCLUSIONS

CTI ablation performed at the time of atrial fibrillation ablation is associated with higher rates of conduction recovery and typical flutter recurrence.

Significance of fragmented QRS complexes for predicting new-onset atrial fibrillation after cavotricuspid isthmus-dependent atrial flutter ablation

BACKGROUND

Atrial fibrillation (AF) and cavotricuspid isthmus (CTI)-dependent atrial flutter (AFL) are 2 separate entities that coexist in a significant proportion of patients. In patients with CTI ablation of AFL, the decision to hold anticoagulation often becomes an issue.

OBJECTIVES

This study aimed to describe the incidence of the development of AF after CTI ablation in patients without a history of AF and to identify the risk predictors of the occurrence of AF.

METHODS

The present study included 120 consecutive patients (106 men; mean age 68 ± 12 years) who underwent radiofrequency catheter ablation (RFCA) of typical AFL since 2010. Patients with a history of AF before RFCA were excluded. The P-wave and QRS morphology, characteristics, and duration were evaluated by 12-lead electrocardiography the day after ablation.

RESULTS

During 3.6 ± 2.6 years of follow-up after RFCA, 49 patients (41%) developed new-onset AF. A univariate analysis revealed that the presence of fragmented QRS (fQRS) complexes (hazard ratio [HR], 4.63; 95% confidence interval [CI] 2.31-9.29; P < .001) and advanced interatrial block (IAB), defined as P-wave duration > 120 ms and biphasic morphology in the inferior leads (HR 4.44; 95% CI 2.45-8.01; P < .001), were predictors of new-onset AF. A multivariate analysis revealed that fQRS complexes (HR 3.35; 95% CI 1.58-7.10; P = .002) and advanced IAB (HR 2.64; 95% CI 1.38-5.07; P < .004) were independent predictors.

CONCLUSION

The present study indicated that new-onset AF developed in a significant proportion of patients undergoing AFL ablation. The presence of fQRS complexes and advanced IAB were predictors of new-onset AF.

Advanced mapping strategies for ablation therapy in adults with congenital heart disease

Background

Ultra-high density mapping (HDM) is a promising tool in the treatment of patients with complex arrhythmias. In adults with congenital heart disease (CHD), rhythm disorders are among the most common complications but catheter ablation can be challenging due to heterogenous anatomy and complex arrhythmogenic substrates. Here, we describe our initial experience using HDM in conjunction with novel automated annotation algorithms in patients with moderate to great CHD complexity.

Methods

We studied a series of consecutive adult patients with moderate to great CHD complexity and an indication for catheter ablation due to symptomatic arrhythmia. HDM was conducted using the Rhythmia™ mapping system and a 64-electrode mini-basket catheter for identification of anatomy, voltage, activation pattern and critical areas of arrhythmia for ablation guidance. To investigate novel advanced mapping strategies, postprocedural signal processing using the Lumipoint™ software was applied.

Results

In 19 patients (53±3 years; 53% male), 21 consecutive ablation procedures were conducted. Procedures included ablation of atrial fibrillation (n=7; 33%), atrial tachycardia (n=11; 52%), atrioventricular accessory pathway (n=1; 5%), the atrioventricular node (n=1; 5%) and ventricular arrhythmias (n=4; 19%). A total of 23 supraventricular and 8 ventricular arrhythmias were studied with the generation of 56 complete high density maps (atrial n=43; ventricular n=11, coronary sinus n=2) and an average of 12,043±1,679 mapping points. Multiple arrhythmias were observed in n=7 procedures (33% of procedures; range of arrhythmias detected 2-4). A total range of 1-4 critical areas were defined per procedure and treated within a radiofrequency application time of 16 (interquartile range 12-45) minutes. Postprocedural signal processing using Lumipoint™ allowed rapid annotation of fractionated signals within specific windows of interest. This supported identification of a practical critical isthmus in 20 out of 27 completed atrial and ventricular tachycardia activation maps.

Conclusions

Our findings suggest that HDM in conjunction with novel automated annotation algorithms provides detailed insights into arrhythmia mechanisms and might facilitate tailored catheter ablation in patients with moderate to great CHD complexity.

Additional Diagnostic value of Mini Electrodes in an 8-mm Tip in Cavotricuspid Isthmus Ablation

Background

Eight-mm ablation catheters are widely used in cavotricuspid isthmus ablation (CTI) for treatment of right sided atrial flutter. However a high success rate, these large ablation tips comes with adisadvantage of lower resolution of fractionated signals.

Purpose

The aim of this study was to evaluate the additional diagnostic value of the electrograms recordedfrom mini electrodes (MEs) in an 8-mm ablation catheter tip during CTI.

Methods

CTI-ablation procedures were compared retrospectively in two groups, namely, group A: the Abbott Safire 8-mm tip with a 3D mapping system (n =37) and group B: the Boston Scientific MiFi IntellaTip XP 8-mm tip without a 3D mapping system (n=13). We analyzedacute procedural success, ablation characteristics and recurrence rate at one-year follow-up. Electrograms from MEs were analyzedright before the onset of the critical ablation application that resulted in acute CTI-block. We determined whether these ME electrograms had additional diagnostic value in addition to of the 8-mm tip derivedelectrogram.

Results

At the onset of the critical ablation application, the MEs had an important additional value in 3 out of 13 cases as local signals were sensed on the MEs that were not recorded by the 8-mm tip electrode. In 2cases the ME did not show local electrogramsalthough the ablationwas still effective. Acute procedural and long-term success wereobserved in all patients. No differences were found in time to bidirectional block, procedure time or fluoroscopic exposure.

Conclusion

Our data show that signals recorded from the MEs had additional diagnostic value, but only in asmall percentage of the patients. We did not observe, although omitting 3D-mapping in the ME group, any differencebetween groups with regard to procedural or ablation characteristicsduring CTI-ablation.

Intra-procedural evaluation of the cavo-tricuspid isthmus anatomy with different techniques: comparison of angiography and intracardiac echocardiography

Cavo-tricuspid isthmus (CTI) anatomies are highly variable, and specific anatomies lead to a difficult CTI ablation. This study aimed to compare the clinical utility of angiography and intracardiac echocardiography (ICE) in evaluating CTI anatomies, and to investigate the impact of the CTI anatomy on the procedure when the ablation tactic was adjusted to the anatomy. This study included 92 consecutive patients who underwent a CTI ablation. The CTI morphology was assessed with both right atrial angiography and ICE before the ablation, and the ablation tactic was adjusted to the anatomy. The mean CTI length was 34 ± 9 mm. On ICE imaging, 21 (23%) patients had a flat CTI, while 41 (45%) had a concave CTI with a mean depth of 5.6 ± 2.7 mm. The remaining 30 (32%) had a distinct pouch with a mean depth of 6.4 ± 2.3 mm, located at the posterior, middle, and anterior isthmus in 15, 14, and 1 patients, respectively. The Eustachian ridge (ER) was visualized in 46 (50%) patients. On angiography, a pouch and ER were detected in 22 and 15 patients, but not in the remaining 8 and 31, respectively. A complete CTI block line was created in all patients without any complications. The CTI anatomy did not significantly impact any procedural parameters. ICE was superior to angiography in evaluating the detailed CTI anatomy, especially pouches and the ER. An adjustment of the ablation tactic to the anatomy could overcome the procedural difficulties of the CTI ablation in cases with specific anatomies.

Advances in Real-Time MRI-Guided Electrophysiology

Purpose of Review

Theoretical benefits of real-time MRI guidance over conventional electrophysiology include contemporaneous 3D substrate assessment and accurate intra-procedural guidance and evaluation of ablation lesions. We review the unique challenges inherent to MRI-guided electrophysiology and how to translate the potential benefits in the treatment of cardiac arrhythmias.

Recent Findings

Over the last 5 years, there has been substantial progress, initially in animal models and more recently in clinical studies, to establish methods and develop workflows within the MR environment that resemble those of conventional electrophysiology laboratories. Real-time MRI-guided systems have been used to perform electroanatomic mapping and ablation in patients with atrial flutter, and there is interest in developing the technology to tackle more complex arrhythmias including atrial fibrillation and ventricular tachycardia.

Summary

Mainstream adoption of real-time MRI-guided electrophysiology will require demonstration of clinical benefit and will be aided by increased availability of devices suitable for use in the MRI environment.

An initial experience of high-density mapping-guided ablation in a cohort of patients with adult congenital heart disease

AIMS

In the management of both ventricular and supraventricular tachycardia in patients with congenital heart disease (CHD) catheter ablation has now been recognized as one of the mainstays.

METHODS AND RESULTS

We review our initial experience of using the Rhythmia mapping system in a cohort of 12 adult CHD patients presenting with multiple arrhythmia substrates. A total of 78 arrhythmia maps were attempted in a total of 15 procedures, but possible due to the dilatation of the target chamber only 44% of maps were able to reconstruct the entire arrhythmia. All patients underwent pre-procedure 3D imaging (either cardiac magnetic resonance or computed tomography), but image integration was suboptimal. A median of two maps per patient were finally analysed and acquisition took in median 22 min with a median number of 12 574 (8230-18 167) mapping points. Procedural data with a total duration amounting to in median 285 (194-403) min, with a median total fluoroscopy exposure of 7.5 (5.2-10.7) min. After a median of 1.5 procedures [median of 12 (8-16 months)], nine patients remained in stable sinus rhythm or atrial paced rhythm, while three patients had further sustained recurrences. One of these passed away in end-staged heart failure.

CONCLUSION

This initial experience of using high-density mapping for arrhythmia management in patients with CHD allowed rapid acquisition of multiple maps with high accuracy to identify surgical scars and fibrosis, however, it was limited by large atrial volumes and a high percentage of incomplete maps resulting in modest clinical success.

MARSHALL bundles elimination, Pulmonary veins isolation and Lines completion for ANatomical ablation of persistent atrial fibrillation: MARSHALL-PLAN case series

INTRODUCTION

Beyond pulmonary veins (PV) isolation, the ablation strategy for persistent atrial fibrillation (AF) remains controversial. Substrate ablation may provide a high termination rate but at the cost of impaired atrial physiology and recurrent complex re-entries. To overcome these pitfalls, we investigated a new lesion set based on important anatomical considerations.

METHODS AND RESULTS

The case series included 10 consecutive patients with persistent AF. Three atrial structures were successively targeted: (1) coronary sinus and vein of Marshall (CS-VOM) musculature elimination; (2) PVs isolation; and (3) anatomical isthmuses block. The lesion set completion was the procedural endpoint. Step 1: VOM ethanol infusion was feasible in all cases (mean time of 33.4 ± 9.4 minutes), mean radiofrequency (RF) time for CS-VOM bundles was 14.4 ± 6.9 minutes. Step 2: mean RF time for PV isolation was 27.7 ± 9.3 minutes. Step 3: mean RF time for mitral, roof, and cavotricuspid lines was 5.7 ± 2.3, 8.1 ± 4.3, and 5.9 ± 1.9 minutes, respectively. The lesion set was achieved in all patients. Mean procedure time was 270 ± 29.9 minutes. AF termination and noninducibility were, respectively, obtained in 50% and 90% of the patients. After a 6-month follow-up, all patients were free from arrhythmia recurrence.

CONCLUSION

The present case series reports a new ablation strategy systematically targeting anatomical structures previously identified as possibly involved in the fibrillatory process and the recurrent tachycardias. The resulting lesion set provides good short-term outcomes. Although promising, these preliminary results need to be confirmed in the larger prospective study.

A comparison of 8-mm and open-irrigated gold-tip catheters for typical atrial flutter ablation: Data from a prospective multicenter registry

BACKGROUND

Cavotricuspid isthmus (CTI) radiofrequency (RF) catheter ablation is the standard treatment for patients suffering from CTI-dependent atrial flutter (AFL). The aim of this study was to compare the use in clinical practice of 8-mm gold-tip catheter (8mmRFC) and open-irrigated gold-tip catheter (irrRFC) for RF typical AFL ablation.

METHODS

Patients with typical AFL were treated with 8mmRFC or irrRFC catheters according to investigator preferences. The primary endpoint was the cumulative radiofrequency time (CRFT). Fluoroscopy time, acute and 6-month success rates were secondary endpoints.

RESULTS

After excluding 3 patients with left AFL, 157 of the enrolled patients (median age 71.8 [interquartile range, 64.1-76.2], 76% men, 91% in NYHA class ≤II, 65% with no structural heart disease) were analyzed: 74 (47%) subjects were treated with the 8mmRFC and 83 (53%) with the irrRFC. The median CRFT was 3 [2-6] minutes in the 8mmRFC group and 5 [3-7] minutes in the irrRFC group (P = .183). There were no significant differences in ablation success rates, intraprocedural CTI reconnections, audible steam pops, and procedural times. In the 8mmRFC group, a significantly lower fluoroscopy time was observed as compared to the irrRFC group (8 [5-12] vs 15 [10-20] minutes, P < .001). During the follow-up period, AFL recurrences were documented in 3 patients in the 8mmRFC group and 2 in the irrRFC group (P = .655).

CONCLUSIONS

The 8mmRFC and the irrRFC performed similarly in routine practice for CTI ablation in terms of cumulative RF time, acute and 6-month success rates. Fluoroscopy time was significantly lower in the 8mmRFC group.

Simple and novel technique to confirm complete mitral isthmus block

BACKGROUND

Differential pacing technique to confirm mitral isthmus (MI) block is sometimes challenging due to destroyed tissues after extensive ablation. The purpose of this study is to set an endpoint of MI ablation using conduction time around the mitral annulus (MA).

METHODS

Forty-five consecutive patients with persistent atrial fibrillation who received MI linear ablation were included. The geometry and activation times of the left atrium around the MA were collected using a multipolar catheter before ablation. During coronary sinus (CS) pacing, the time between the stimulus and the wave-front collision at the opposite side of the MA (defined as T/2) was calculated, and the doubled value was defined as the estimated perimitral conduction time (E-PMCT). The endpoint for complete MI block was when the stimulus (at distal CS) minus the maximal delayed potential (St-MDP) on the MI interval reached the E-PMCT.

RESULTS

St-MDP reached E-PMCT during MI ablation in 44/45 patients. Among these 44 patients, differential pacing revealed bidirectional block in 39/44 (88.6%), whereas in 5/44 (11.4%), the differential pacing was not possible because of the loss of capture of local potentials due to extensive applications around the linear line. In one patient, the St-MDP did not reach E-PMCT (E-PMCT: 148 ms, St-MDP :130 ms) and differential pacing revealed no MI block. E-PMCT values (median 176 ms) correlated strongly with St-MDP (median 185 ms, P < 0.0001, R = 0.98).

CONCLUSIONS

Although E-PMCT differs between individuals, the value is significantly correlated with the St-MDP. This technique may be useful in providing an individual endpoint of MI ablation as an alternative to differential pacing.

Electrogram characteristics of the coronary sinus in cases requiring epicardial ablation within the coronary sinus for creating a conduction block at the left lateral mitral isthmus

BACKGROUND

Left lateral mitral isthmus (LLMI) linear ablation is a safe and effective technique for treating left mitral flutter. LLMI linear ablation with pulmonary vein isolation may reduce the recurrence of persistent atrial fibrillation. However, epicardial ablation within the coronary sinus (CS) is often required to create the LLMI block line. If the necessity for epicardial ablation is checked before ablation, complications may be reduced.

METHODS

We recruited 135 patients who underwent their first LLMI ablation and divided them into two groups, one group not requiring epicardial ablation for creating a conduction block at the LLMI (Endo group) and another requiring it (Epi group). These two groups were compared in terms of the electrogram characteristics of the CS.

RESULTS

Bidirectional block through the LLMI was achieved in 94.8% of patients. In 42% of these patients, not only the endocardium but also the epicardium was ablated. As for the electrogram, the Endo group had lower atrium voltage and atrioventricular voltage ratios (p = 0.009) than the Epi group before LLMI ablation. By contrast, there were no significant differences in the atrium voltage and the atrioventricular voltage ratio between these two groups after LLMI ablation.

CONCLUSIONS

For creating a conduction block at the LLMI, the atrium voltage and the atrioventricular voltage ratio in the CS before ablation are important. The atrioventricular voltage ratio is a crucial criterion for determining whether epicardial ablation is necessary; furthermore, the atrioventricular voltage ratio in the CS must be reduced with or without epicardial ablation.

Focal intra-cavotricuspid isthmus atrial tachycardias occurring after typical atrial flutter ablation: incidence and electrocardiographic and electrophysiological characteristics

PURPOSE

Focal atrial tachycardias (ATs) from the septal cavotricuspid isthmus (CTI) occurring after successful CTI ablation can mimic typical atrial flutter (tAFL). This study investigated the incidence, and electrocardiographic and electrophysiological characteristics of these ATs.

METHODS

Among 1082 consecutive patients undergoing successful CTI ablation without any congenital heart diseases, 7 were diagnosed with focal ATs originating from the septal CTI that occurred a median of 74 days after the CTI ablation.

RESULTS

The electrocardiographic characteristics of the ATs were similar to those of the tAFLs. The AT's cycle length was never shorter than and often similar to that of tAFLs. The activation patterns along the tricuspid annulus during the ATs were the same as those of tAFLs in 4 patients with foci adjacent to the CTI line, and centrifugal from foci around the coronary sinus (CS) ostium in 3. Entrainment pacing from the lateral CTI during the ATs revealed a manifest fusion and long post-pacing interval. Entrainment pacing from the lateral CTI during the ATs revealed that the atrial electrograms recorded from the CS and high-lateral right atrium were orthodromically captured, while that from the proximal CS revealed that the atrial electrograms recorded from the CS and lateral right atrium were antidromically captured without manifest fusion.

CONCLUSIONS

Focal intra-CTI ATs with a microreentrant mechanism very rarely occurred after successful CTI ablation. The electrocardiographic and electrophysiological characteristics of these ATs were similar to those of tAFLs. Overdrive pacing from the lateral CTI and proximal CS was helpful for distinguishing these ATs from recurrent tAFLs.

Prospective evaluation of a novel catheter equipped with mini electrodes on a 10-mm tip for cavotricuspid isthmus ablation - The efficacy of a mini electrode guided ablation

BACKGROUND

Clinical utility of large-tip ablation catheters for cavo-tricuspid isthmus (CTI) ablation has been reported, however, it is limited by the impaired near-field electrogram resolution. This study evaluated the efficiency of a novel mini-electrode (ME) equipped 10-mm tip CTI ablation catheter.

METHODS

Thirty-four patients were prospectively enrolled (Group-A). Initially, radiofrequency energy was applied point-by-point guided by ME signals. If it failed, RF applications were applied conventionally guided by tip-ring signals. The data were compared with 32 and 32 patients undergoing CTI ablation using 8-mm tip (Group-B) and 3.5-mm irrigation-tip (Group-C) catheters, respectively.

RESULTS

The successful CTI block creation rate was significantly higher in Group-A and Group-B than Group-C (32/34[94.1%], 31/32[96.8%], and 25/32[78.1%], p=0.027). In Group-A, ME guided ablation was successful in 30 patients and subsequent conventional ablation in 2. There was no significant difference between the 3 groups for the total procedure and fluoroscopic times using the initial catheters. However, the total radiofrequency applications (6.9±3.6, 9.9±4.3, and 12.0±7.1, p=0.001), total radiofrequency time (358±197, 558±248, and 566±265s, p=0.001), and radiofrequency time to achieve initial block (222±159, 471±242, and 396±211s, p<0.001) were significantly shorter in Group-A than Group-B and Group-C. In Group-A, a maximal ME amplitude attenuation (86±13%, from 0.84±0.53 to 0.08±0.04mV) was obtained by 19.0±6.5s mean applications. Maximal tip-ring amplitude attenuation (76±17%, from 0.58±0.29 to 0.12±0.09mV) was obtained by 22.1±6.2s mean applications.

CONCLUSIONS

ME guided ablation using a novel ME equipped 10-mm tip ablation catheter was feasible for human CTI ablation, and might reduce inadvertent radiofrequency applications.

Atrial Flutter, Typical and Atypical: A Review

Clinical electrophysiology has made the traditional classification of rapid atrial rhythms into flutter and tachycardia of little clinical use. Electrophysiological studies have defined multiple mechanisms of tachycardia, both re-entrant and focal, with varying ECG morphologies and rates, authenticated by the results of catheter ablation of the focal triggers or critical isthmuses of re-entry circuits. In patients without a history of heart disease, cardiac surgery or catheter ablation, typical flutter ECG remains predictive of a right atrial re-entry circuit dependent on the inferior vena cava-tricuspid isthmus that can be very effectively treated by ablation, although late incidence of atrial fibrillation remains a problem. Secondary prevention, based on the treatment of associated atrial fibrillation risk factors, is emerging as a therapeutic option. In patients subjected to cardiac surgery or catheter ablation for the treatment of atrial fibrillation or showing atypical ECG patterns, macro-re-entrant and focal tachycardia mechanisms can be very complex and electrophysiological studies are necessary to guide ablation treatment in poorly tolerated cases.

Creating bidirectional conduction block in the cavotricuspid isthmus by cryothermal ablation with a short freeze time: Insight from the results with a 2-minute freeze cycle

BACKGROUND

Optimal freeze doses are unknown during cryothermal cavo-tricuspid isthmus (CTI) ablation. This study aimed to evaluate the feasibility of 2-minute freeze doses for CTI ablation.

METHODS

Forty-eight consecutive patients undergoing cryothermal CTI ablation following pulmonary vein isolation were enrolled. CTI ablation was performed with 2-minute freeze cycles and 8-mm tip cryocatheters.

RESULTS

Bidirectional CTI block was successfully achieved in 45(93.8%) patients with a median of 5.0[4.0-6.0] cryocatheter applications. The total procedure and fluoroscopic times were a median of 16.5[13.0-20.0] and 4.0[2.0-5.0]min, respectively. A crossover to radiofrequency was performed in 3 patients including 1 due to coronary spasms during the cryoapplication. The tip temperature when block was achieved was a median of -81.0[-73.3 - -84.0]°C. Application times from the start of the last application to achieving block were significantly longer in patients with acute conduction resumption than in those without (46.8±4.0 vs. 20.2±8.8s, p<0.0001), and the optimal cutoff point for predicting no acute resumption was 38.5s (sensitivity 100%, specificity 99.5%). Vasospastic angina occurred in 2 patients, during the procedure in 1 and after in another. Durability could be evaluated a median of 6.0[3.0-8.0] months after the procedure in 14 patients, and conduction resumption was observed in 8(57.1%). The majority of gaps were located at the inferior vena cava edge.

CONCLUSIONS

Acute CTI block was obtained by 2-minute freeze cycles with short procedure and fluoroscopic times. Care should be taken to avoid coronary spasms during the peri-procedural period. Additional cryoapplications might be required to improve conduction block durability.

Crucial role of pulmonary vein firing as an initiator of typical atrial flutter: Evidence of a close relationship between atrial fibrillation and typical atrial flutter

Background

Several studies reported that cavotricuspid isthmus-dependent atrial flutter (typical AFL) frequently coexists with atrial fibrillation (AF); however, the underlying mechanisms have not been fully investigated. This study aimed to reveal the mechanisms of the initiation of typical AFL and the association between typical AFL and AF.

Methods

Among 154 consecutive patients undergoing a first catheter ablation of AF, we investigated the appearance and mechanism of spontaneous initiation of typical AFL during catheter ablation. Then, we retrospectively investigated 67 consecutive patients without a previous AF episode who underwent typical AFL ablation. The occurrence and predictors of AF after catheter ablation were evaluated.

Results

During AF ablation, spontaneous initiation of typical AFL occurred during sinus rhythm in eight (5.2%) patients. The initiations of typical AFL were pulmonary vein (PV) firings except in one patient, in whom paroxysmal AF following superior vena cava firing initiated reverse typical AFL after PV isolation. After typical AFL ablation, AF occurred in 23 (34.3%) patients (mean follow up, 28.2±20.3 months). Kaplan-Meier analysis showed the occurrence of AF after typical AFL ablation to be significantly higher in the patients with a larger left atrial diameter over 40 mm (log-rank test, P=0.046).

Conclusions

PV firing through AF played an important role in initiating typical AFL. The occurrence of AF after typical AFL ablation was high, and a dilated left atrium was associated with increased occurrence of AF. These findings disclosed the close relationship between typical AFL and AF, especially PV firing.

Burning the Gap: Electrical and Anatomical Basis of the Incremental Pacing Maneuver for Cavotricuspid Isthmus Block Assessment

INTRODUCTION

The incremental pacing (IP) maneuver is a highly specific technique that improves the ability to confirm complete CTI conduction block during typical atrial flutter (AFL) ablation, and reduces long-term AFL recurrences. The purpose of this study is to assess the performance of new catheters equipped with additional high precision bipoles (AHPB) to allow the visualization of the cavotricuspid isthmus (CTI) conduction gap and to compare them with the IP maneuver.

METHODS AND RESULTS

Twenty consecutive patients undergoing catheter ablation of the CTI for AFL were included. The IP maneuver confirmed functional versus complete CTI block. Local electrogram analysis using AHPB was then used to assess the presence or absence of gaps across the CTI line. Mean age was 67 years and 80% were male. At the end of the procedure CTI block was achieved in all patients. A transient stage of functional CTI block was observed in 40%. In all cases a continuous fragmented electrogram was present between the double potentials in the CTI in the AHPB channels. In contrast, no electrogram was observed between the CTI double potentials in any of the 20 patients once complete block was confirmed by the IP maneuver. When both techniques were compared a significant association and correlation were observed (chi-square <0.01, Spearman's rho = 1, P < 0.01).

CONCLUSION

Catheters equipped with AHPB can aid in the assessment of complete CTI block during AFL ablation procedures by detecting conduction gaps that correlate with incomplete functional block diagnosed by the IP maneuver.

Impact of Impaired Renal Function on the Incidence of Atrial Fibrillation following Radiofrequency Ablation of Cavotricuspid Isthmus-Dependent Atrial Flutter

Background and Objectives

Atrial fibrillation (AF) occurs frequently after successful radiofrequency ablation (RFA) of cavotricuspid isthmus-dependent atrial flutter (CTI-AFL). Renal impairment has been implicated in the development of AF. The purpose of this study is to clarify the impact of impaired renal function on the incidence of AF after RFA of CTI-AFL.

Subjects and Methods

Between January 2001 and December 2013, 240 non-dialysis patients with no prior history of AF {mean age 55.9±15.2 years old; male, 192 (80.0%)} who had undergone successful CTI-AFL ablation were included in the present study. The baseline estimated glomerular filtration rate was calculated, and patients were divided into those with impaired renal function (<60 mL/min/1.73 m²) and those with preserved renal function (≥ 60 mL/min/1.73 m²). The incidence of AF was retrospectively analyzed.

Results

69 (28.8%) patients experienced new onset AF during a median follow-up duration of 26 months (inter-quartile, 7-53). The incidence of AF was significantly higher in patients with impaired renal function than in those with preserved renal function {13/25 (52.0%) versus 56/215 (26.0%), log rank p=0.019}. Age, CHADS₂ score, impaired renal function, and left atrial diameter were significantly associated with the incidence of AF in univariate Cox regression analysis. Multivariate analysis showed that age was the only significant predictor of AF incidence (hazard ratio, 1.024; 95% confidence interval, 1.004-1.044, p=0.020).

Conclusion

Patients with impaired renal function may require careful attention for the incidence of new onset AF following successful RFA of CTI-AFL.