Complete Bidirectional Isthmus Block Research Articles

Electrophysiological cardiovascular MR: procedure-ready mesh model generation for interventional guidance based on non-selective excitation compressed sensing whole heart imaging.

Fully CMR-guided electrophysiological interventions (EP-CMR) have recently been introduced but data on the optimal CMR imaging protocol are scarce. This study determined the clinical utility of 3D non-selective whole heart steady-state free precession imaging using compressed SENSE (nsWHcs) for automatic segmentation of cardiac cavities as the basis for targeted catheter navigation during EP-CMR cavo-tricuspid isthmus ablation. Fourty-two consecutive patients with isthmus-dependent right atrial flutter underwent EP-CMR radiofrequency ablations. nsWHcs succeeded in all patients (nominal scan duration, 98 ± 10s); automatic segmentation/generation of surface meshes of right-sided cavities exhibited short computation times (16 ± 3s) with correct delineation of right atrium, right ventricle, tricuspid annulus and coronary sinus ostium in 100%, 100%, 100% and 95%, respectively. Point-by-point ablation adhered to the predefined isthmus line in 62% of patients (26/42); activation mapping confirmed complete bidirectional isthmus block (conduction time difference, 136 ± 28ms). nsWHcs ensured automatic and reliable 3D segmentation of targeted endoluminal cavities, multiplanar reformatting and image fusion (e.g. activation time measurements) and represented the basis for precise real-time active catheter navigation during EP-CMR ablations of isthmus-dependent right atrial flutter. Hence, nsWHcs can be considered a key component in order to advance EP-CMR towards the ultimate goal of targeted substrate-based ablation procedures.

Abstract 19728: Translesional Time to Determine Complete Bidirectional Block Across the Cavotricuspid Isthmus

Introduction: The goal of ablation of typical atrial flutter is to create complete bidirectional block across the cavotricuspid isthmus (CTI). The purpose of this study was to document whether there was a transisthmus time that is associated with complete bidirectional isthmus block (CBIB). Methods: Thirty consecutive patients who had CTI ablation procedures were assessed. A circular right atrial mapping catheter, coronary sinus catheter, and electroanatomical mapping were used in all patients. Before ablation, points were marked medial and lateral to the planned line and bidirectional conduction times were assessed. Post ablation bidirectional conduction times were assessed again at the points medial and lateral to the line. The translesional time (TL) was defined as the difference in bidirectional conduction time recorded lateral to the line from medial to the line. CBIB was verified by reversal of activation of the right atrium on the circular mapping catheter and/or documentation of widely spaced double potentials. Results: CBIB was achieved in 29/30 patients. The average baseline counterclockwise (CCW) conduction time across the CTI was 43 +/- 22 msec The average baseline clockwise (CW) conduction time was 42 +/- 16 msec. The average baseline TL was 10 msec CCW, and 9 msec CW. The longest baseline TL was 52 msec CCW and 28 msec CW . Post ablation, the average CCW conduction time was 149 msec, and CW was 150 msec in patients with CBIB. The average TL in patients with CBIB was 116 msec CCW and 111 msec CW. The shortest TL associated with CBIB was 90 msec CCW and 91 msec CW. The maximum TL associated with incomplete block was 68 msec. Conclusions: A bidirectional TL of greater 90 msec was predictive of CBIB after typical atrial flutter ablation, and could be used simplify assessment of CBIB during CTI ablation.

Feasibility of real-time magnetic resonance imaging-guided electrophysiology studies in humans

Magnetic resonance imaging (MRI) in the context of electrophysiology (EP) studies facilitates visualization of complex three-dimensional anatomy and the underlying arrhythmogenic substrate, real-time passive visualization of catheters, atrial and ventricular function and complications, as well as lesion visualization during the ablation without radiation. In the following we report on our first experience of a real-time MRI-guided EP study demonstrating current possibilities and drawbacks. Five consecutive patients (one male, four female; mean age 66 ± 11 years) with symptomatic arrhythmias, three patients with highly symptomatic typical atrial flutter, presented to our hospital for isthmus ablation, one patient for an EP study and one for slow pathway ablation in atrioventricular node re-entry tachychardia. The four ablations were performed successfully in a conventional EP laboratory and complete bidirectional isthmus block was confirmed in three patients with atrial flutter. After the procedure in the EP laboratory all five patients were transferred to a 1.5 T whole-body MRI scanner (Intera) for a diagnostic EP procedure. Two MRI compatible steerable diagnostic/ablation catheters (Vision) were inserted via the femoral sheaths and manipulated by an experienced electrophysiologist using a commercially available interactive real-time steady-state free precession sequence (repetition time = 3 ms, echo time = 1 ms, flip angle = 35°, slice thickness = 10 mm, frame rate = 8/s). All catheters could be placed successfully in the right atrium and ventricle, confirmed by intracardiac electrograms, using passive catheter tracking. Furthermore, simple programmed stimulation maneuvers were performed. During and after the procedure, no adverse effects were observed in any patients. To our knowledge, this is the first series of patients with real-time MRI-guided placement of multiple catheters with subsequent performance of stimulation maneuvers. Besides the mentioned benefits, this technology still encounters several limitations, which have to be solved before application in a routine clinical setting. Challenges arise from delineation of precise surface electrocardiogram recordings in the MRI setting along with intracardiac electrograms, easier handling and visualization of catheters, facilitation of immediate defibrillation in the MRI setting and implementation of an active catheter tracking system.

Six-month follow-up of isthmus-dependent right atrial flutter ablation using a remote magnetic catheter navigation system: a case-control study

Objective— The objective of this study was to compare results between the magnetic navigation system (MNS) and conventional catheter ablation of cavo-tricuspid isthmus (CTI)-dependent right atrial flutter (AFL) in a case control study.Background— A remote MNS has been used for ablation of various arrhythmias including CTIdependent AFL but comparative results between MNS and conventional ablation are not available.Methods— Between May and September 2007, a total of 51 consecutive patients (45 men, mean age 65.4 ± 9.4 years) had undergone catheter ablation for CTI-dependent AFL.The catheter ablation (70°C, 70 W, 90 s) was performed with either an 8-mm-tip magnetic catheter using MNS (case group, n = 26, 23 men, mean age 64.6 ± 9.6 y) or a conventional 8-mm catheter (case group, n = 25, 22 men, mean age 65.4 ± 9.1 y). Acute procedural success was defined as complete bidirectional isthmus block and success at six months was defined as absence of AFL during the six months follow-up.Results— With respect to baseline characteristics there were no differences between the two groups.The procedure time in MNS and conventional group was [median (range)] 53 (30-130) min and 45 (30-100) min, respectively (P= 0.12). Acute success was achieved by MNS and conventional ablation in 25/26 (96.2%) and 25/25 (100%) of patients, respectively (P= 0.53). During the six months of follow-up 4 patients, 2 in each group, experienced recurrence (P= 0.90). No major complication occurred during the procedure. Charring on the catheter tip occurred in 5 patients (19.2%) in MNS and none of the patients in the control group (P < 0.05).Conclusion— This case-control study demonstrated the acute and mid-term efficacy and safety of catheter ablation by MNS for CTI-dependent AFL, similar to rates achieved by conventional radiofrequency catheter ablation.

Evaluation of the Surface ECG in Detecting Isthmus Conduction Block after Ablation of Typical Atrial Flutter

To investigate the value of changes in P wave morphology and duration detected by surface electrocardiogram (ECG) during proximal coronary sinus (PCS) and low lateral right atrial (LLRA) stimulation as a marker for complete bidirectional isthmus conduction block in the procedure of typical atrial flutter ablation. Morphology, duration, and ratio of a positive terminal P wave were estimated in 52 typical atrial flutter patients before and after radiofrequency catheter ablation (RFCA). Atrial flutter ablation resulted in a complete bidirectional isthmus block in all 52 patients. The terminal portion of the P wave towards a positive morphology was detected in 90.7% (47/52) patients both during PCS and LLRA stimulation. These changes were predominantly observed in the inferior leads. Positive morphological changes of the terminal P wave portion and the measured P wave ratio (40% +/- 12%) in the inferior leads indicating bidirectional isthmus conduction block with a sensitivity of 87.5% and a specificity of 91.7% were observed. An increment of 20 ms or more in P wave duration during the PCS stimulation and 10 ms or more during the LLRA stimulation indicating the conduction block with a sensitivity of 90% and a specificity of 100%. The variation of P wave morphology and duration in inferior leads of the surface ECG is a helpful technique to assess the complete bidirectional isthmus conduction block in the procedure of typical atrial flutter ablation.

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.

Initial Clinical Experience with a Remote Magnetic Catheter Navigation System for Ablation of Cavotricuspid Isthmus‐Dependent Right Atrial Flutter

A remote magnetic navigation system (MNS) is available and has been used with a 4-mm-tip magnetic catheter for radiofrequency (RF) ablation of some supraventricular and ventricular arrhythmias; however, it has not been evaluated for the ablation of cavotricuspid isthmus-dependent right atrial flutter (AFL). The present study evaluates the feasibility and efficiency of this system and the newly available 8-mm-tip magnetic catheter to perform RF ablation in patients with AFL. Twenty-six consecutive patients (23 men, mean age 64.6 +/- 9.6 years) underwent RF ablation using a remote MNS. RF ablation was performed with an 8-mm-tip magnetic catheter (70 degrees C, maximum power 70 W, 90 seconds). The endpoint of ablation was complete bidirectional isthmus block. To assess a possible learning curve, procedural data were compared between the first 14 (group 1) and the rest (group 2) of the patients. The initial rhythm during ablation was AFL in 20 (19 counterclockwise and 1 clockwise) and sinus rhythm in six patients. Due to technical issues, the ablation in the 18th patient could not be done with the MNS, and so we switched to conventional ablation. The remote magnetic navigation and ablation procedure was successful in 24 of the 25 (96%) remaining patients with AFL. In one patient (patient 2), conventional catheter was used to complete the isthmus block after termination of AFL. The procedure, preparation, ablation, and fluoroscopy times (median [range]) were 53 (30-130) minutes, 28 (10-65) minutes, 25 (12-78) minutes, and 7.5 (3.2-20.8) minutes, respectively. Patients in group 2 had shorter procedure (45 [30-70] min vs 80 [57-130] min, P = 0.0001), preparation (25 [10-30] min vs 42 [30-65] min, P = 0.0001), ablation (20 [12-40] min vs 31 [20-78] min, P = 0.002), and fluoroscopy (7.2 [3.2-12.2] min vs 11.0 [5.4-20.8] min, P = 0.014) times. No complication occurred during the procedure. Using a remote MNS and an 8-mm-tip magnetic catheter, ablation of AFL is feasible, safe, and effective. Our data suggest that there is a short learning curve for this procedure.

Ablation de flutter atrial : expérience initiale d'un centre hospitalier général

Background Right atrial flutter has a relatively high incidence. It is often symptomatic and can have a poor outcome particularly in case of thrombo-embolic events. Aim of study We evaluate the results of radiofrequency catheter ablation for right atrial flutter since the introduction of this technique in our hospital. Methods The 28 first patients referred in our institution for atrial flutter and relevant for cavo-tricuspid isthmus ablation were enrolled. Ablation used a 8 mm tip electrode catheter and one or two conventional diagnostic catheters. The goal of ablation was complete bidirectional isthmus block. Results The first-line success rate was 96 percent with 4 percent early flutter recurrence. The mean duration of radiofrequency current applications was 652 ± 409 seconds. No complication was observed. Conclusion This results are comparable with the published data and encourage the development of basic ablation procedures and maintenance of rhythmologic competence in general hospital inside medical network.

Use of a New Non‐Fluoroscopic Three‐Dimensional Mapping System in Type I Atrial Flutter Ablation

We studied 40 patients who underwent cavo-tricuspid isthmus ablation for typical counterclockwise atrial flutter with cooled tip catheters between 2001 and 2003. Complete bi-directional isthmus block was created in all patients. A new, three-dimensional (3D), non-fluoroscopic mapping system was used in 20 patients (test group), and conventional fluoroscopy in 20 others (conventional group), using anatomic and electrophysiologic criteria in both groups. We measured the total procedure, ablation procedure, and overall fluoroscopy times, and the total number of radiofrequency (RF) applications delivered in the two groups. The overall fluoroscopy time was shorter in the test group (mean 8.8 minutes, range 2-17 minutes) than the conventional group (29.7 minutes, range 12-57 minutes; P < 0.001). Though the overall procedure time was similar in both groups (92.5 +/- 28.6 minutes vs 106.5 +/- 20.9 minutes; P = 0.067) the ablation duration (25.1 +/- 6.6 minutes versus 43.3 +/- 19.6 minutes; P = 0.0051) and the total RF applications (10.6 +/- 9.4 versus 16.4 +/- 9.4; P = 0.044) were smaller in the test group. The use of a new, 3D non-fluoroscopic mapping system markedly reduced the fluoroscopy exposure during typical atrial flutter ablation. It was also associated with a significant reduction in ablation time and in the number of RF applications. Since atrial flutter ablation is one of the most frequently performed procedures, this system may significantly reduce the overall amount of radiation exposure in high-volume laboratories.

Double potential interval and transisthmus conduction time for prediction of cavotricuspid isthmus block after ablation of typical atrial flutter.

Complete bi-directional isthmus block is the endpoint of typical atrial flutter ablation. The purpose of this study was to investigate the feasibility of the local double potential (DP) interval and the change in transisthmus conduction time for predicting complete isthmus block after ablation of the cavotricuspid isthmus. The study population consisted of 32 patients with typical atrial flutter after a procedure of radiofrequency (RF) ablation of the cavotricuspid isthmus (16 had incomplete block and 16 had complete block). The transisthmus conduction time was determined during pacing from the proximal coronary sinus and low lateral right atrium before and after RF ablation. The DP interval close to the ablation line was evaluated after final RF energy application. In the counterclockwise direction, transisthmus conduction time had an increase of 37 +/- 25.4% and 127.3 +/- 35.5% (P < 0.001), and the DP interval was 63.3 +/- 8.7 ms and 120 +/- 17.4 ms (P < 0.001) after achievement of incomplete and complete block, respectively. The sensitivity, specificity, positive and negative predictive values of an increase in the transisthmus conduction time > or =50% were 100%, 81%, 84% and 100%, respectively; those of DP interval > or =100 ms were 100%. In the clockwise direction, transisthmus conduction time had an increase of 38.8 +/- 28.6% and 135.7 +/- 63.6% (P < 0.001), and the DP interval was 63.6 +/- 13.8 ms and 127.7 +/- 27.1 ms (P < 0.001) after achievement of incomplete and complete block, respectively. The sensitivity, specificity, positive and negative predictive values of an increase in the transisthmus conduction time > or =50% were 100%, 67%, 83% and 100%, respectively; those of the DP interval > or =100 ms were 100%. The transisthmus conduction time > or =50% increase or DP interval > or =100 ms was feasible to predict complete bi-directional isthmus block.

Electrogram polarity and cavotricuspid isthmus block during ablation of typical atrial flutter.

The atrial activation sequence around the tricuspid annulus has been used to assess whether complete block has been achieved across the cavotricuspid isthmus during radiofrequency ablation of typical atrial flutter. However, sometimes the atrial activation sequence does not clearly establish the presence or absence of complete block. The purpose of this study was to determine whether a change in the polarity of atrial electrograms recorded near the ablation line is an accurate indicator of complete isthmus block. Radiofrequency ablation was performed in 34 men and 10 women (age 60 +/- 13 years [mean +/- SD]) with isthmus-dependent, counterclockwise atrial flutter. Electrograms were recorded around the tricuspid annulus using a duodecapolar halo catheter. Electrograms recorded from two distal electrode pairs (E1 and E2) positioned just anterior to the ablation line were analyzed during atrial flutter and during coronary sinus pacing, before and after ablation. Complete isthmus block was verified by the presence of widely split double electrograms along the entire ablation line. Complete bidirectional isthmus block was achieved in 39 (89%) of 44 patients. Before ablation, the initial polarity of E1 and E2 was predominantly negative during atrial flutter and predominantly positive during coronary sinus pacing. During incomplete isthmus block, the electrogram polarity became reversed either only at E2, or at neither E1 nor E2. In every patient, the polarity of E1 and E2 became negative during coronary sinus pacing only after complete isthmus block was achieved. In 4 patients (10%), the atrial activation sequence recorded with the halo catheter was consistent with complete isthmus block, but the presence of incomplete block was accurately detected by inspection of the polarity of E1 and E2. Reversal of polarity in bipolar electrograms recorded just anterior to the line of isthmus block during coronary sinus pacing after ablation of atrial flutter is a simple, quick, and accurate indicator of complete isthmus block.

Randomized comparison of two targets in typical atrial flutter ablation

Typical atrial flutter ablation has become anatomically guided to 2 separate sites within the isthmus at the inferior right atrium: (1) between the inferior vena cava and the tricuspid annulus (anterior side of the isthmus [A]), (2) between the eustachian crest, the coronary sinus ostium and tricuspid annulus (posterior side of the isthmus [P]). We prospectively compared ablation results at these sites in 72 consecutive patients. Patients were randomized in group P or A according to the initial target site. If ablation failed at 1 site after 15 radiofrequency (RF) pulses, the other side of the isthmus was targeted. Before 15 RF pulses, complete bidirectional isthmus block was achieved in 30 of 36 group A patients and in 25 of 36 group P patients, with similar mean RF pulses number, procedure time, and fluoroscopy time. After shifting to the other target, success was finally obtained at P in 2 of 6 group A patients, and at A in 8 of 11 group P patients before a maximum of 30 RF pulses. Among successful patients, number of RF pulses, procedure time, and fluoroscopy time were significantly lower in group A (7.2 ± 5.4 vs 11.0 ± 8.1 pulses, p = 0.03; 131 ± 44 vs 163 ± 66 minutes, p = 0.03; 31 ± 19 vs 46 ± 24 minutes, p = 0.01, respectively). Impairment of atrioventricular (AV) nodal conduction occurred in 5 patients only during ablation at P. AV block was transient in 4 patients and permanent in 1. Although atrial flutter ablation is equally effective at P and A, success seems easier to obtain when A is first targeted. Ablation at P is associated with a significant risk of AV block.

Impact of Transisthmus Linear Ablation of Typical Atrial Flutter on Coronary Sinus Activation Time

Complete or incomplete bidirectional isthmus conduction block after linear ablation of atrial flutter is difficult to interpret without detailed multiple electrodes mapping along the tricuspid annulus and the low right atrial isthmus area. The influence of isthmus block on the intraatrial septal and coronary sinus activation has not been assessed by endocardial mapping. This study was designed to analyze the intraartial and interatrial activation times in a retrospective fashion to investigate (1) whether isthmus conduction block can change the coronary sinus activation sequence during low lateral right atrial pacing, and (2) the correlation between change of coronary sinus activation time and isthmus conduction block. Sixty-five consecutive patients (mean age, 57 +/- 18 years) with clinically documented typical atrial flutter were studied. A 20-pole "Halo" catheter was placed around the tricuspid annulus including the entire low right atrial isthmus to verify complete bidirectional isthmus block. Activation time from ostium to distal coronary sinus (OCS-->DCS), and interatrial septum and isthmus activation times during right atrial pacing were analyzed and compared before and after incomplete or complete isthmus block. Complete bidirectional isthmus block was achieved in 50 (77%) patients. During low lateral right atrial pacing, linear ablation at low right atrial isthmus results in a significant delay of activation in all coronary sinus recording sites with greater extent at the ostium area without influence on interatrial septum activation in complete and incomplete isthmus conduction block. The difference of the OCS-->DCS interval before and after ablation, delta (OCS-->DCS), was well correlated with results of isthmus conduction block and significantly longer in patients with complete than those with incomplete isthmus block (34 +/- 11 vs 11 +/- 8 ms, P < 0.001), thereby allowing a value of 20 ms as a discriminative parameter to differentiate incomplete (< 20 ms) from complete (> or = 20 ms) isthmus counterclockwise conduction block with a sensitivity of 96% and a specificity of 88%. In conclusion, creation of a line of block at the inferior vena cava-tricuspid annulus isthmus could change coronary sinus activation sequence during low lateral right atrial pacing in sinus rhythm. The change of coronary sinus activation time after linear ablation, delta (OCS-->DCS), was well correlated with isthmus conduction block by using a value > or = 20 ms to discern complete counterclockwise isthmus block.