Complete Cavotricuspid Isthmus Block Research Articles

178 Catheter inversion during cavotricuspid isthmus catheter ablation: the new shaft visualization catheter reduces fluoroscopy use

Abstract Aims Catheter ablation (CA) is the choice therapy of cavotricuspid isthmus (CTI) atrial flutter. The aim of this study was to describe our approach to improve the CTI ablation using a zero-fluoroscopy (ZF). The procedural difficulties could be related to anatomical characteristics of the CTI. Methods and results One hundred eighty-eight patients that performed CA of CTI were retrospectively and consecutively evaluated between 2017 and 2019. The studied population was divided into two groups. Eighty-eight patients who were undergone CA using ablation catheter without shaft visualization catheter (NSV) were Group 1. One hundred patients were undergone CA using ablation catheter with a shaft visualization (SV); they were Group 2. The catheter was looped at the Eustachian ridge after 200 s of radiofrequencies (RF) without elimination of local electrogram. A conduction line block of CTI was obtained in all patients of Group 2 using a ZF approach. In 16 patients of Group 1, the catheter inversion was obtained using fluoroscopy to avoid damages during its loop. In Group 2, a complete CTI block was obtained with a catheter inversion approach in 10 patients without fluoroscopy, visualizing the shaft and the tip of the ablation catheter on the electroanatomic (EAM) map. In the overall population studied the use of SV had a linear correlation with the ZF approach (r = 0.629; P < 0.001). The duration of RF was lower in Group 2 than in Group 1 (Group 1: 27.8 ± 6.3 vs. Group 2: 15.6 ± 7.2 min; P < 0.01). The procedure time between two groups was lower in Group 2 than in Group 1 (Group 1: 58.4 ± 22.4 vs. Group 2: 42.2 ± 15.7 min; P < 0.01). No differences between two groups were documented regarding success and complications. Conclusions The visualization of the shaft’s catheter on the EAM permitted the catheter inversion safely in order to overcome some complex CTI anatomy and obtain bidirectional block. The SV reduced procedure time, RF applications, and fluoroscopy exposition during CTI ablation.

Catheter inversion during cavotricuspid isthmus catheter ablation: The new shaft visualization catheter reduces fluoroscopy use.

AimsCatheter ablation (CA) is the choice therapy of cavotricuspid isthmus (CTI) atrial flutter. The aim of this study was to describe our approach to improve the CTI ablation using a zero‐fluoroscopy (ZF). The procedural difficulties could be related to anatomical characteristics of the CTI.MethodsOne hundred eighty‐eight patients that performed CA of CTI were retrospectively and consecutively evaluated between 2017 and 2019. The studied population was divided into two groups. Eighty‐eight patients who were undergone CA using ablation catheter without shaft visualization catheter (NSV) were Group 1. One hundred patients were undergone CA using ablation catheter with a shaft visualization (SV); they were Group 2. The catheter was looped at the Eustachian ridge after 200 seconds of radiofrequencies (RF) without elimination of local electrogram.ResultsA conduction line block of CTI was obtained in all patients of Group 2 using a ZF approach. In 16 patients of Group 1, the catheter inversion was obtained using fluoroscopy to avoid damages during its loop. In Group 2, a complete CTI block was obtained with a catheter inversion approach in ten patients without fluoroscopy, visualizing the shaft and the tip of the ablation catheter on the electroanatomic (EAM) map. In the overall population studied the use of SV had a linear correlation with the ZF approach (r = .629; P < .001). The duration of RF was lower in Group 2 than in Group 1 (Group 1: 27.8 ± 6.3 vs Group 2: 15.6 ± 7.2 minutes; P < .01). The procedure time between two groups was lower in Group 2 than in Group 1 (Group 1: 58.4 ± 22.4 vs Group 2: 42.2 ± 15.7 minutes; P < .01). No differences between two groups were documented regarding success and complications.ConclusionsThe visualization of the shaft's catheter on the EAM permitted the catheter inversion safely in order to overcome some complex CTI anatomy and obtain bidirectional block. The SV reduced procedure time, RF applications and fluoroscopy exposition during CTI ablation.

Mapping potentials adjacent to the cavo-tricuspid isthmus ablation line during incremental pacing: A feasible and highly accurate maneuver to confirm complete CTI conduction block.

The diagnostic accuracy of incremental atrial pacing (IP) to determine complete cavo-tricuspid isthmus (CTI) block during typical atrial flutter (AFL) ablation is limited by both an extensive/nonlinear ablation and/or the presence of intra-atrial conduction delay elsewhere in the right atrium. We examined the diagnostic performance of an IP variant based on the assessment of the atrial potentials adjacent to the ablation line which aims at overcoming both limitations. From a prospective population of 108 consecutive patients, 15 were excluded due to observation of inconclusive CTI ablation potentials precluding for a straight comparison between the IP maneuver and its variant. In the remaining 93, IP was performed from the low lateral right atrium and the coronary sinus ostium, with the ablation catheter positioned both at the CTI line and adjacent (<5 mm) to its septal and lateral aspect. The IP variant consisted of measuring the interval between the two atrial electrograms situated on the same side of the ablation line, opposite to the pacing site, a ≤10 ms increase indicating complete CTI block. The IP maneuver and its variant were consistent with complete CTI block in 82/93 (88%) and 87/93 (93%) patients, respectively. Four patients had AFL recurrence during follow-up: 2/4 and 4/4 had been adequately classified as incomplete block by the IP maneuver and its variant, respectively. Twenty-three patients (24%) had significant intra-atrial conduction delay elsewhere in the right atrium. The IP maneuver and its variant were suggestive of an incomplete CTI block in 11/23 and 4/23 in this setting (P = .028), with the later best predicting subsequent AFL relapses (2/12 vs 2/4, P = .01). The IP variant, which was designed to overcome the limitations of the conventional IP maneuver, accurately distinguishes complete from incomplete CTI block and helps to predict AFL recurrences after ablation.

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

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. 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). 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.

Characteristics of Virtual Unipolar Electrogram Voltage and Characteristics of Isthmus Block during Radiofrequency Ablation of Typical Atrial Flutter

Background: The optimal technique for recording of the electrogram to detect complete cavo-tricuspid isthmus (CTI) block during radiofrequency ablation (RFA) of the typical atrial flutter (AFL) using non-contact mapping system remains unclear. The aim of this study was to investigate the characteristics of the local virtual unipolar electrogram recorded at the ablation line during coronary sinus pacing after RFA of the CTI. Methods: Non-contact mapping was performed in 8 patients with AFL. Non-contact virtual unipolar electrograms were obtained before and after CTI linear ablation. All unipolar electrograms were acquired with both wide-band (0.5-300 Hz and 0.5-IC 150 Hz) and narrow-band filtering (32-300 Hz). The unipolar electrogram measurements included both the peak-to-peak voltage and peak-negative voltage for both filter settings, and the morphological characteristics of the second component of double potentials. Results: Comparison of the electrogram voltage along the ablation line before and after ablation demonstrated: 1) peak-negative voltage reduction at the mid-portion of the ablation line by 0.5-IC 150 Hz filtering, and 2) the second component of unipolar electrogram morphologies of R, Rs or rSR were the most sensitive and speci-c recording technique to predict conduction block. Conclusions: Non-contact unipolar electrograms using the peak-negative voltage with 0.5-IC 150 Hz and a predominant R-wave pattern in the second component at the ablation line indicate complete CTI block, even in the presence of transcristal conduction.

Incremental pacing maneuver for atrial flutter recurrence reduction after ablation: Vallès: Yield of incremental pacing after flutter ablation

BackgroundA <20ms increase in the interval between cavo-tricuspid isthmus (CTI) double potentials during incremental pacing (IP) is a highly specific marker differentiating functional from complete CTI block during typical flutter (AFL) ablation. Long-term effects of IP remain unclear. We aimed to assess the impact of IP in reducing AFL recurrences after CTI ablation. MethodsOne hundred and thirty-four patients (age 67±13years, 78% males) undergoing successful CTI ablation were included and divided into 2 groups: Group 1 (n=68), in which ablation was performed before the IP maneuver was incorporated, with CTI block confirmed by at least 1 non-local and 1 local electrogram-based previously established criteria; and Group 2 (n=66), in which IP maneuver was used to confirm complete CTI block. ResultsNo intergroup differences were noted in baseline characteristics, ablation settings and fluoroscopy/radiofrequency times. Long-term AFL recurrences were observed in 14 out of 134 patients (10.4%), and were more common in Group 1 (19%, vs 1.5% among Group 2 patients, p<0,001). Despite a longer follow-up period among the former group (1603±734 vs. 964±289days, respectively), the adjusted AFL recurrence rate was still higher among Group 1 patients (4.3%/year vs. 0.6%/year, p<0,001). Cox-regression analysis confirmed inclusion in Group 1 as the only predictor of AFL recurrences (HR=8.2, CI 1.04–64.7, p=0.046). ConclusionsThe addition of the IP maneuver for the diagnosis of complete CTI block reduces AFL long-term recurrences after ablation.

Incremental His-To-Coronary Sinus Maneuver

Background— Achievement of complete cavotricuspid isthmus (CTI) conduction block reduces typical atrial flutter recurrences after ablation. The lack of increase in the His-to-Coronary sinus ostium atrial interval during incremental pacing (IP) from the low lateral right atrium may distinguish slow conduction from complete CTI conduction block. Methods and Results— Sixty-six consecutive patients (age, 65±13 years; 18% female) were prospectively included. A &lt;10 ms increase in the His-to-Coronary sinus ostium atrial timing during low lateral right atrium IP at cycle length of 600 ms through 300 ms was compared with the previously reported IP maneuver for the confirmation of complete CTI block. On the basis of the IP maneuver, complete CTI block (phase 2) was achieved in 59 patients, in 13 of whom an intermediate phase of functional CTI block (phase 1) was observed. In the remaining 7 patients, the IP maneuver did not allow for assessment of complete CTI block because of the presence of inconclusive potentials in the CTI ablation line. As compared with the IP maneuver, the incremental His-to-Coronary sinus ostium maneuver was consistent with functional CTI block during phase 1 in all cases and conclusive of complete CTI block in 98% of cases during phase 2. Conclusions— The incremental His-to-Coronary sinus ostium maneuver is analogous to the IP maneuver in distinguishing complete CTI block from persistent CTI conduction. This maneuver may provide confirmation of CTI block in those patients in whom assessment of local electrogram–based criteria is not feasible because of inconclusive potentials in the CTI ablation line.

POSTER PRESENTATIONS

POSTER PRESENTATIONS

Randomized Comparison of Cavotricuspid Isthmus Ablation for Atrial Flutter Using an Open Irrigation-Tip versus a Large-Tip Radiofrequency Ablation Catheter

Large-tip (10 mm) catheters (LTCs) and open-irrigation-tip catheters (OITCs), both capable of creating large lesions, are more effective than conventional catheters for cavotricuspid isthmus (CTI) ablation. However, it is not clear whether complete CTI block can be achieved more efficiently using an LTC or an OITC. The purpose of this study was to compare the efficiency of radiofrequency catheter ablation (RFA) of the CTI using LTC versus OITC to eliminate atrial flutter (AFL). Sixty consecutive patients (age = 62 ± 10 years) with typical AFL were randomized to undergo RFA of CTI using an LTC (10 mm) or an OITC. If complete CTI block was not achieved by ≤30 minutes of RFA, patients were allowed to cross over to ablation with the other catheter. A 3-dimensional electroanatomical mapping system was used for catheter navigation only with the OITC. The mean duration of RFA to achieve CTI block in 50% of the patients was 6.8 ± 2.2 minutes with an LTC and 11.7 ± 2.7 minutes with an OITC (P = 0.001). After 30 minutes of RFA, CTI block was achieved in 26/30 (87%) and 25/30 patients (83%) using an LTC and an OITC, respectively (P = 1.0). After crossover, CTI block was achieved in 4/5 (80%) and in 4/4 patients (100%) with an LTC and OITC, respectively (P = 1.0). LTC was associated with a lower volume of intravenous fluid administration (388 ± 365 mL versus 865 ± 451 mL, P = 0.0001) and a trend for shorter procedure duration (95 ± 31 minutes versus 114 ± 50 minutes, P = 0.09) than the OITC. At 6 ± 3 months, 30/30 patients (100%) in the LTC and 27/30 patients (90%) in the OITC groups remained free from AFL, respectively (P = 0.24). Except for one inconsequential steam-pop during RFA with the OITC, there were no complications. Complete CTI block is achieved more rapidly using an LTC than an OITC, and with a similar clinical efficacy.

A simple and definite proof of complete cavotricuspid isthmus block

Complete bidirectional block of the cavotricuspid isthmus (CTI) after radiofrequency ablation of typical atrial flutter is an established endpoint. Methods to determine completeness of block are subject to debate, 3‐6 since the ultimate electrophysiological proof does not seem to exist. Additionally, because of increasing economic constraints, the number of usable catheters and poles may become limited. The criterion for clockwise (CW) CTI block based on the anterior right atrium (RA) activation sequence during septal CTI pacing has been proposed to overcome the limitations of other criteria. 7 Pastor et al. elegantly and meticulously evaluate the clinical significance of this method, validating it as a powerful predictor of a freedom of recurrence after more than 3 years. Several issues are to be raised. First, in this retrospective series, three types of ablation catheters have been used which may partially affect the conclusion that can be drawn from this study: a solid 4 mm-tip catheter, a solid 8 mm-tip catheter, and an openirrigation 4 mm-tip catheter. It seems that the solid 4 mm-tip catheter was the least effective and accounted for the majority of recurrences. Secondly, the importance of obtaining non-ambiguous evidence of complete bidirectional CTI block is stressed again. Atrial flutter recurrence rate was only 3% in the presence of bidirectional block vs. 22% in the case of unidirectional block and 67% in the absence of block (P , 0.001 vs. bidirectional block). This is not a new observation but interestingly and, in our opinion, of major importance, CW CTI block, as demonstrated by completely descending anterior RA activation sequence during septal CTI pacing, was simultaneously proven by differential pacing in only 64% of these cases. The limited sensitivity of septal differential pacing was attributed to the unclear local CTI electrogram interpretation (due to the low voltage and fragmented potentials) and was observed in 36% of cases, which is similar to our experience. 5 Moreover, CTI anfractuous anatomy 8,9 makes detailed assessment of the ablation line difficult. We still think that accurate activation mapping of the anterior RA activation sequence during septal CTI pacing is of prime importance to clearly identify complete CTI block. The usefulness of a multipolar catheter is stressed out once more in this paper, with its distal poles placed along the antero-inferior RA wall but in the most immediate vicinity of the ablation line. Many cases of localized slow (yet persistent) conduction are then easily ruled out.

Incremental Pacing for the Diagnosis of Complete Cavotricuspid Isthmus Block During Radiofrequency Ablation of Atrial Flutter

Complete conduction block of the cavotricuspid isthmus (CTI) reduces atrial flutter recurrences after ablation. Incremental rapid pacing may distinguish slow conduction from complete CTI conduction block. Fifty-two patients (67 +/- 9 years) undergoing 55 CTI ablation procedures were included. With ablation, double potentials (DPs) separated by an isoelectric line of > or =30 ms were obtained. Incremental atrial pacing (600-250 ms) was performed from coronary sinus (CS) and low lateral right atrium (LLRA). A <20 ms increase in the DPs distance during incremental pacing was indexed as complete CTI block. In 8 patients, an initial <20 ms DPs distance increase was noted; direct complete isthmus block was suggested and no additional ablation performed. In the remaining, the CTI line was remapped for conduction gaps and additional radiofrequency energy pulses applied. Complete block, as indexed by incremental pacing, occurred in 46 of 55 procedures, with one flutter recurrence (follow-up 8 +/- 2 months): DPs interval variation of 116 +/- 20 to 123 +/- 20 ms (CS), P = 0.21; and 122 +/- 25 to 135 +/- 35 ms (LLRA), P = 0.17. The remaining 9 patients (persistent rate-dependent DPs increase) presented 3 flutter recurrences, P = 0.01: DP distance from 127 +/- 15 to 161 +/- 18 ms (CS), P < 0.001; and 114 +/- 24 to 142 +/- 10 ms (LLRA), P = 0.007. Incremental pacing distinguishes complete CTI block from persistent conduction. Such identification, accompanied by additional ablation to achieve block, should minimize flutter recurrences after ablative therapy.

Linear Ablation with Duty-Cycled Radiofrequency Energy at the Cavotricuspid Isthmus

Multielectrode catheters using duty-cycled radiofrequency (RF) have been developed to treat atrial fibrillation (AF). Many of these patients also have atrial flutter. Therefore, a linear multielectrode has been developed using the same RF energy. The concept and acute results of linear ablation using duty-cycled RF were tested in the cavotricuspid isthmus (CTI). The CTI was targeted in 75 patients, in 68 (90%) among them as an adjunct to AF ablation with the same technology. A linear electrode catheter with a 4-mm tip and five 2-mm ring electrodes was connected to a generator titrating duty-cycled RF at 20-45 W up to a target temperature of 70 degrees C in 1:1 unipolar/bipolar mode. During a mean procedure time of 20 +/- 12 minutes, complete CTI block was achieved by 4 +/- 3 applications of duty-cycled RF in 69 (92%) patients. No more than three RF applications were necessary in 60% of patients. During the initial learning curve, standard RF had to be used in five (7%) patients. Complete block was not achieved in one patient with frequent episodes of AF. Char was observed in five (7%) patients with poor electrode cooling; consequently, the temperature ramp-up was slowed and manually turned off in the event of low-power delivery. Two groin hematomas occurred; otherwise, no clinical complications were observed. Multielectrode catheters delivering duty-cycled RF can effectively ablate the CTI with few RF applications with promising acute results. Further modifications are necessary to improve catheter steering and prevent char formation. (PACE 2010; 444-450).

Interactive real-time mapping and catheter ablation of the cavotricuspid isthmus guided by magnetic resonance imaging in a porcine model

AimsWe investigated the feasibility of real-time magnetic resonance imaging (RTMRI) guided ablation of the cavotricuspid isthmus (CTI) by using a MRI-compatible ablation catheter.Methods and resultsCavotricuspid isthmus ablation was performed in an interventional RTMRI suite by using a novel 7 French, steerable, non-ferromagnetic ablation catheter in a porcine in vivo model (n = 20). The catheter was introduced and navigated by RTMRI visualization only. Catheter position and movement during manipulation were continuously visualized during the entire intervention. Two porcine prematurely died due to VT/VF. Anatomical completion of the CTI ablation line could be achieved after a mean of 6.3±3 RF pulses (RF energy: 1807±1016.4 Ws/RF pulse, temperature: 55.9±5.9°C) in n = 18 animals. In 15 of 18 procedures (83.3%) a complete CTI block was proven by conventional mapping in the electrophysiological (EP) lab.ConclusionCompletely non-fluoroscopic ablation guided by RTMRI using a steerable and non-ferromagnetic catheter is a promising novel technology in interventional electrophysiology.

Remote Magnetic Catheter Navigation for Cavotricuspid Isthmus Ablation in Patients With Common-Type Atrial Flutter

Conventional catheter ablation of cavotricuspid isthmus (CTI)-dependent atrial flutter is a widely applied standard therapy. Remote magnetic catheter navigation (RMN) may provide benefits for different ablation procedures, but its efficacy for CTI ablation has not been evaluated in a randomized, controlled trial. Ninety patients undergoing de novo ablation of atrial flutter were randomly assigned to conventional manual (n=45) or RMN-guided (n=45) CTI ablation with an 8-mm-tip catheter. Complete bidirectional isthmus block was achieved in 84% (RMN) and 91% (conventional catheter ablation) of the cases (P=0.52). RMN was associated with shorter fluoroscopy time (median, 10.6 minutes; interquartile range [IQR], 7.6 to 19.9, versus 15.0 minutes; IQR, 11.5 to 23.1; P=0.043) but longer total radiofrequency application (17.1 minutes; IQR, 8.6 to 25, versus 7.5 minutes; IQR, 3.6 to 10.9; P<0.0001), ablation time (55 minutes; IQR, 28 to 76, versus 17 minutes; IQR, 7 to 31; P<0.0001), and procedure duration (114+/-35 versus 77+/-24 minutes, P<0.0001). Procedure duration in the RMN group did not decrease significantly with case experience. Long-term procedure success, defined as achievement of complete CTI block and freedom from atrial flutter recurrence during 6 months of follow-up, was lower in the RMN group (73% versus 89%, P=0.063). Right atrial angiography after ablation revealed no significant differences between groups in terms of right atrial diameter or CTI length, morphology, and angulation. Furthermore, none of these parameters was predictive for difficult (ablation time >20 minutes) or unsuccessful ablation. RMN-guided CTI ablation is associated with reduced radiation exposure but prolonged ablation and procedure times as compared with conventional catheter navigation. Our findings suggest that ablation lesions produced with an RMN-guided 8-mm catheter are less effective irrespective of CTI anatomy. clinicaltrials.gov Identifier: NCT00560872.

Incidence and predictive factors of atrial fibrillation after ablation of typical atrial flutter

Although cavotricuspid isthmus radiofrequency catheter ablation is considered curative therapy for typical atrial flutter, many patients develop an atrial fibrillation after ablation. The purpose of our study was to determine the incidence and the predictive factors of post-ablation atrial fibrillation. One hundred and forty eight consecutive patients underwent cavotricuspid isthmus ablation for the treatment of typical atrial flutter between January 2004 and December 2005 in our electrophysiological department. Complete cavotricuspid isthmus block was successfully obtained in 96.6% of the patients. At the end of the electrophysiological study a sustained atrial fibrillation was inducible in 20 patients (13.5%). During an average follow-up of 21.3 +/- 8.2 months, atrial fibrillation occurred in 27% of the patients. Univariate analysis identified four parameters correlated with post-ablation atrial fibrillation among the 21 parameters tested: the young age of the patients, a prior history of atrial fibrillation, an inducible atrial fibrillation, and a paroxysmal atrial flutter. Only inducible atrial fibrillation and paroxysmal atrial flutter were independent factors linked to atrial fibrillation after ablation. In our study the incidence of atrial fibrillation after cavotricuspid isthmus radiofrequency catheter ablation is 152 per 1,000 patient-years, i.e. 25 times higher than the incidence of atrial fibrillation in the general population of the same age. Twenty five percent of the patients who had neither prior history of atrial fibrillation nor structural heart disease suffered from atrial fibrillation during a mean follow-up of 21.3 +/- 8.2 months. All these results suggest that atrial flutter and fibrillation could be manifestations of a more general electrophysiologic disease. They emphasize the need for all these patients to benefit from regular, long-term cardiological follow-up after cavotricuspid isthmus ablation because of the high incidence of atrial fibrillation. Treatment with antiarrhythmic and antithrombotic agents should also be adapted to these factors.

Radio-Frequency Ablation of Atrial Flutter: Long-Term Results and Predictive Value of Cavo-Tricuspid Isthmus Bidirectional Block as Determined by a Simplified Technique

Objectives: Complete bidirectional cavo-tricuspid isthmus (CTI) block is mandatory for radio-frequency (RF) ablation of typical atrial flutter (AF). CTI block can be assessed by a simplified method using two catheters and the technique of differential pacing, but long-term results in large series are poorly known. Methods: CTI RF ablation was performed in 255 consecutive patients with typical AF, using one quadripolar catheter, and the ablation catheter, in association with the technique of differential pacing. Results: Procedural success, as defined by documentation of complete bidirectional CTI block using limited activation mapping, positive differential pacing together with termination of ongoing AF, was achieved in 80% of patients. AF recurred in 37 patients (14%) over a mean follow-up period of 15 ± 9 months. Two hundred and forty-one patients (94%) were finally cured, with 1.1 procedures/patient. The recurrence rate was related to the achievement of complete CTI bidirectional block (12% vs. 29%, p = 0.01). Conclusions: Long-term results of CTI ablation, employing a simplified method using the differential pacing technique, are similar to those for the standard methods using multipolar catheters. Therefore, this technique compares favorably to other established methods for such common RF procedures, especially due to its lower cost.

Usefulness of the polarity in high-density wide range-filtered bipolar mapping to detect isthmus block during radiofrequency ablation of typical atrial flutter

The atrial activation sequence around the tricuspid annulus (TA) cannot always be used to establish whether complete block has been achieved across the cavotricuspid isthmus (CTI) during radiofrequency ablation (RFCA) for typical counterclockwise atrial flutter (CCW-AFL). We examined whether a change in the polarity of the atrial high-density wide range-filtered bipolar electrograms recorded near the ablation line is an accurate indicator of complete CTI block. Nineteen patients with CCW-AFL underwent RFCA. Electrograms were recorded around the TA with duodecapolar conventional (2mm x 8mm x 2mm spacing) and high-density (2-mm spacing) Halo catheters. The bipolar electrograms on the high-density Halo catheter recorded from a series of adjacent electrode pairs positioned just lateral to the ablation line were filtered at a bandpass setting of 0.05-500 Hz. The activation sequence on the conventional Halo catheter during coronary sinus pacing (CSp) and inferolateral TA pacing, and the bipolar electrograms on the high-density Halo catheter during CSp were determined before and after RFCA. The final complete CTI block was verified by the presence of widely split double electrograms > or =100 msec along the ablation line. The final complete CTI block was achieved in all the 19 patients. Before RFCA, the polarity of bipolar electrograms was predominantly negative during CCW-AFL and positive during CSp. In 18 of the 19 patients, the bipolar electrograms exhibited the CCW activation and a negative polarity during CSp only after complete CTI block. In one of those 18 patients, additional applications of RFCA changed the polarity of bipolar electrograms positive to negative although the conventional Halo electrogram activation sequence suggested complete CTI block during CSp. In seven patients, who had transverse conduction across the crista terminalis during CSp, the conventional Halo electrogram activation sequence suggested an incomplete CTI block. However, in six of those seven patients, the CCW activation had a predominantly negative polarity of the bipolar electrograms. In one of those seven patients, complete CTI block was unable to be detected even using the high-density Halo catheter. These data demonstrate that the high-density wide range-filtered mapping can identify the CTI block in undetectable cases of complete CTI block or incomplete CTI block by the conventional method. The polarity of the bipolar electrograms recorded just lateral to the ablation line during CSp after RFCA of AFL may be used as a simple and an accurate indicator of complete CTI block.

Mapping-guided ablation of the cavotricuspid isthmus: A novel simplified approach to radiofrequency catheter ablation of isthmus-dependent atrial flutter

Because the anatomic features of the cavotricuspid isthmus (CTI) are complex, radiofrequency (RF) energy requirements for CTI ablation may vary at each point within the CTI. Conventionally, multiple-site mapping has been required for determining CTI conduction block. The purpose of this study was to develop a more efficacious method for ablation of isthmus-dependent atrial flutter. Forty consecutive patients underwent CTI ablation using a CTI mapping-guided approach (20 patients) or a conventional approach (20 patients). In the CTI mapping-guided approach, an octapolar catheter was positioned on the CTI parallel to, and downstream from, the intended ablation line in order to map and ablate the breakthrough point. Complete CTI block was achieved in all study patients. CTI mapping of incomplete ablation lines revealed that the site with the shortest interval between double potentials did not always coincide with the conduction gap. Disappearance of a breakthrough pattern on the CTI electrograms corresponded to creation of complete CTI block. During ablation, CTI mapping exhibited pseudo-CTI block in 8% of patients in the clockwise direction and 63% of patients in the counterclockwise direction. The number and total time of RF applications were significantly lower with the CTI mapping-guided approach than with the conventional approach (7.7 +/- 3.9 applications vs 13.8 +/- 8.9 applications and 8.9 +/- 4.4 minutes vs 16.3 +/- 11.9 minutes, respectively, P <.05). In the CTI mapping-guided approach, RF applications were not required along the entire CTI in 7 patients (35%). This simplified technique was feasible for creating and determining complete CTI block, with fewer RF applications required.

Characteristics of virtual unipolar electrograms for detecting isthmus block during radiofrequency ablation of typical atrial flutter

ObjectivesThe purpose of this study was to investigate the characteristics of the second component of local virtual unipolar electrograms recorded at the ablation line during coronary sinus (CS) pacing after radiofrequency ablation (RFA) of the cavotricuspid isthmus (CTI) for typical atrial flutter (AFL). BackgroundRadiofrequency ablation of the CTI can produce local double potentials at the ablation line. The second component of unipolar electrograms represents the approaching wavefront in the right atrium opposite the pacing site. We hypothesized that the morphologic characteristics of the second component of double potentials would be useful in detecting complete CTI block. MethodsRadiofrequency ablation of the CTI was performed in 52 patients (males = 37, females = 15, 62 ± 12 years) with typical AFL. The noncontact mapping system (Ensite 3000, Endocardial Solutions, St. Paul, Minnesota) was used to guide RFA. Virtual unipolar electrograms along the ablation line during CS pacing after RFA were analyzed. Complete or incomplete CTI block was confirmed by the activation sequence on the halo catheter and noncontact mapping. ResultsThree groups were classified after ablation. Group I (n = 37) had complete bidirectional CTI block. During CS pacing, the second component of unipolar electrograms showed an R or Rs pattern. Group II (n = 12) had incomplete CTI block. The second component of unipolar electrograms showed an rS pattern. Group III (n = 3) had complete CTI block with transcristal conduction. The second component of unipolar electrograms showed an rSR pattern. ConclusionsA predominant R-wave pattern in the second component of unipolar double potentials at the ablation line indicates complete CTI block, even in the presence of transcristal conduction.

Randomized comparison of anatomical versus voltage guided ablation of the cavotricuspid isthmus for atrial flutter

Objectives The purpose of this prospective study was to compare radiofrequency catheter ablation of the cavotricuspid isthmus using a strictly anatomic approach to an approach guided by a bipolar voltage map to avoid high voltage zones in the cavotricuspid isthmus. Background It is not clear whether local atrial electrogram amplitude influences the achievement of complete cavotricuspid isthmus block during radiofrequency catheter ablation for atrial flutter. Methods Thirty-two patients with atrial flutter were randomized to cavotricuspid isthmus ablation using an anatomical approach (group I, 16 patients) or guided by a bipolar voltage map (group II, 16 patients). A 3-dimensional electroanatomic mapping system and an 8-mm-tip ablation catheter were used in all patients. With the anatomical approach, an ablation line was created in the cavotricuspid isthmus at a 6 o’clock position in the 45 degree left anterior oblique projection. During voltage-guided ablation, a high-density bipolar voltage map of the cavotricuspid isthmus was created, and then contiguous applications of radiofrequency energy were delivered to create an ablation line through the cavotricuspid isthmus sites with the lowest bipolar voltage. Results Complete cavotricuspid isthmus conduction block was achieved in 100% of patients in each group. The mean maximum voltages along the line were 3.6 ± 1.5 mV in group I, and 1.2 ± 0.9 mV in group II ( P < .01). Creating a high-density voltage map was associated with ∼15-minute increase in the total procedure time ( P = .2). During a mean follow-up of 177 ± 40 days, there were no recurrences of atrial flutter in either group. There were no complications in either group. Conclusions When cavotricuspid isthmus ablation for atrial flutter is performed with an 8-mm-tip catheter, complete block can be achieved in all patients regardless of local voltage. Ablation of high voltage zones is not associated with a higher recurrence rate. Therefore, anatomic ablation without voltage mapping is the preferred initial approach for cavotricuspid isthmus ablation.