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

INTRODUCTION: 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. METHODS AND RESULTS: 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. CONCLUSION: 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 anatomic and electrogram mapping approaches to ablation of typical atrial flutter

INTRODUCTION: The cavotricuspid isthmus can be ablated using an anatomic approach or an electrogram mapping approach in which sites at which there is a gap in the line of block are targeted. The aim of this study was to compare the anatomic and electrogram mapping approaches for creating a line of block in the cavotricuspid isthmus after an initial, unsuccessful anatomically directed ablation line. METHODS AND RESULTS: The subjects of this study were 63 patients with isthmus-dependent atrial flutter in whom a single series of contiguous applications of radiofrequency energy guided by fluoroscopy in the cavotricuspid isthmus did not result in complete block. The patients were randomly assigned to additional ablation on an anatomic basis (n = 31) or guided by single potentials or narrowly split double potentials during coronary sinus pacing (n = 32). After every 15 applications of radiofrequency energy, the alternate approach was used until complete block was achieved. Before cross-over, complete block was achieved in 6 patients (19%) with the anatomic approach compared with 19 patients (59%) with the electrogram mapping approach (P < 0.005). The electrogram mapping approach also was more effective than the anatomic approach in achieving complete isthmus block after the first cross-over (72% vs 23%, P < 0.005) and after the second cross-over (80% vs 42%, P < 0.05). CONCLUSION: When there is incomplete block after an initial series of applications of radiofrequency energy in the cavotricuspid isthmus, complete block is achieved more efficiently with an electrogram mapping approach than with an anatomic approach.     

三尖瓣峡部消融对心房颤动导管消融术后复发的影响

目的:评估三尖瓣峡部消融对伴有典型心房扑动(房扑)和不伴典型房扑发作的心房颤动(房颤)患者术后复发的影响.方法:连续入选房颤射频消融治疗患者113例,根据有无典型房扑分为三尖瓣峡部消融组(CTI组)和未行三尖瓣峡部消融组(Non-CTI组),比较临床特征及手术特点,并随访术后典型房扑和房颤发生率.结果:Non-CTI组左房内径更大,持续性和永久性房颤的比例、左房线性消融的比例更高.而CTI组射频消融时间较Non-CTI组更长.术后典型房扑和房颤发生率2组无显著区别.结论:无典型房扑发作的房颤患者,不行三尖瓣峡部消融,不会升高术后典型房扑发生率和房颤复发率,同时射频消融时间缩短.     

Phased-array intracardiac echocardiography for defining cavotricuspid isthmus anatomy during radiofrequency ablation of typical atrial flutter

INTRODUCTION: Cavotricuspid isthmus (CTI) topography includes ridges, pouches, recesses, and trabeculations. These features may limit the success of radiofrequency ablation (RFA) of typical atrial flutter (AFL). The aim of this study was to assess the utility of phased-array intracardiac echocardiography (ICE) for imaging the CTI and monitoring RFA of AFL. METHODS AND RESULTS: Fifteen patients (mean age 64 +/- 9 years) underwent ICE assessment (imaging frequency 7.5-10 MHz) before and after RFA of AFL. The ICE catheter was positioned at the inferior vena cava-right atrial junction and the following parameters were measured: (1) CTI length from the tricuspid valve to the eustachian ridge; (2) extent of CTI pouching; and (3) thickness pre/post RFA of the anterior, mid, and posterior CTI. CTI length was 35 +/- 6 mm at end-ventricular systole but shorter (30 +/- 6 mm) and more pouched at end-ventricular diastole (P = 0.02). A pouch or recess was seen in 11 of 15 patients (mean depth 6 +/- 2 mm). The septal CTI was more pouched than the lateral CTI, but the latter had more prominent trabeculations. Trabeculations were seen in 10 of 15 patients, and at these locations the CTI was 4.6 +/- 1 mm thick. Anterior, mid, and posterior CTI thickness pre-RFA was 4.1 +/- 0.8, 3.3 +/- 0.5, and 2.7 +/- 0.9 mm, respectively (P < 0.001 by analysis of variance). ICE guided RFA away from unfavorable CTI features (recesses/thick trabeculations). RFA applications created discrete CTI lesions that coalesced, forming diffuse CTI swelling. Post-RFA thickness was as follows: anterior 4.8 +/- 0.8 mm (P = NS vs pre); mid 3.8 +/- 0.8 mm (P = 0.05 vs pre); and posterior 3.8 +/- 0.8 mm (P = 0.02 vs pre). CONCLUSION: Phased-array ICE permits novel real-time CTI imaging with excellent endocardial resolution and may facilitate RFA of AFL.     

Unidirectional conduction block at cavotricuspid isthmus created by radiofrequency catheter ablation in patients with typical atrial flutter

INTRODUCTION: Although unidirectional conduction block at the cavotricuspid isthmus can be created by radiofrequency ablation for atrial flutter, its underlying mechanism has not been elucidated. METHODS AND RESULTS: Twenty-seven patients (22 men and 5 women; mean age 59 +/- 11 years) who met the following criteria were studied: (1) bidirectional isthmus conduction demonstrable at baseline; (2) at least one linear lesion attempted on the cavotricuspid isthmus with radiofrequency catheter ablation; and (3) conduction times at anterolateral and posteromedial portions of the isthmus measured for both clockwise and counterclockwise directions before the ablation procedure. Unidirectional conduction block was observed before achieving bidirectional block in 9 patients (group I); the remaining 18 patients did not exhibit unidirectional conduction block (group II). All unidirectional conduction blocks were demonstrated in the counterclockwise direction. Anterolateral isthmus conduction time in group I was significantly longer than that in group II in both directions. However, there were no significant differences in posteromedial isthmus conduction time between groups I and II in either direction. Anterolateral isthmus conduction time was significantly longer than posteromedial conduction time in group I but not in group II. CONCLUSION: There were significant differences in conduction properties at the cavotricuspid isthmus between patients who developed unidirectional conduction block and those who did not. Our results support the notion that anisotropy contributes to the genesis of unidirectional conduction block at the cavotricuspid isthmus during the radiofrequency ablation procedure.     

An alternative method of assessing bidirectional block for atrial flutter

V‐A and A‐V Intervals During Atrial Flutter Ablation . Background: The success of cavotricuspid (CTI) ablation depends on the achievement of bidirectional block. Previous investigators have shown that right ventricular (RV) pacing can replace proximal coronary sinus (pCS) pacing in assessing clockwise CTI conduction block. Objective: We sought to assess bidirectional conduction using antegrade (A‐V) and retrograde (V‐A) conduction times in the absence of coronary sinus (CS) pacing. Methods: Counterclockwise CTI conduction block was evaluated using conduction time to the QRS from 2 pacing sites (immediately lateral and further lateral to the CTI). This was compared to the conduction time to the pCS with pacing from the same 2 lateral points. This was measured prior to ablation in 7 patients and 41 patients following ablation. To evaluate clockwise CTI conduction block we measured the conduction time to the 2 lateral sites during RV pacing and pCS pacing. This was measured in 7 patients prior to ablation and 16 patients following successful ablation. Results: The abbreviated technique correctly indicated the presence or absence of bidirectional block in all patients. Furthermore, conduction times as assessed by the 2 methods correlated well both before and after creation of bidirectional block (correlation coefficients prior to ablation: clockwise direction r = 0.92, P = 0.0036; counterclockwise direction r = 0.86, P = 0.0132; after ablation: clockwise direction r = 0.82, P = 0.0001; counterclockwise direction r = 0.91, P < 0.0001). Conclusion: Bidirectional CTI conduction block can be successfully demonstrated using A‐V and V‐A conduction without the need for CS pacing. Patients need, however, to have intact A‐V and V‐A AV nodal conduction. (J Cardiovasc Electrophysiol, Vol. 22, pp. 431‐435)     

Voltage-guided ablation technique for cavotricuspid isthmus-dependent atrial flutter: refining the continuous line

Ablation of the cavotricuspid isthmus has become first-line therapy for "isthmus-dependent" atrial flutter. The goal of ablation is to produce bidirectional cavotricuspid isthmus block. Traditionally, this has been obtained by creation of a complete ablation line across the isthmus from the ventricular end to the inferior vena cava. This article describes an alternative method used in our laboratory. There is substantial evidence that conduction across the isthmus occurs preferentially over discrete separate bundles of tissue. Consequently, voltage-guided ablation targeting only these bundles with large amplitude atrial electrograms results in a highly efficient alternate method for the interruption of conduction across the cavotricuspid isthmus. Understanding the bundle structure of conduction over the isthmus facilitates more flexible approaches to its ablation and targeting maximum voltages in our hands has resulted in reduction of ablation time and fewer recurrences.     

Histopathologic background for resistance to conventional catheter ablation of common atrial flutter

Histopathologic examination of the cavotricuspid isthmus in which a large-tip catheter was necessary to achieve conduction block is presented. No thickened myocardium or prominent trabeculation was observed on the ablation line. A small cardiac vein extending through the isthmus across the ablation scar was detected. The remaining myocardial cells were distributed along the small cardiac vein. It is possible that the luminal blood flow of the small cardiac vein protects the surrounding atrial muscle from effective delivery of radiofrequency energy.     

Evaluation of an individualized strategy of cavotricuspid isthmus ablation as an adjunct to atrial fibrillation ablation

Objectives: To evaluate supplementary cavotricuspid isthmus (CTI) ablation as an adjunct to atrial fibrillation (AF) ablation in selected patients.
Background: It is unclear whether routine CTI ablation is beneficial in all patients undergoing AF ablation.
Methods and Results: In patients undergoing AF ablation, additional CTI block was created only for those with typical atrial flutter (Afl) before or during the ablation. Out of 188 consecutive patients (108 male, 56 ± 9 years), 75 underwent CTI ablation (Group CTI+) and left atrial (LA) ablation (circular mapping-guided extensive pulmonary vein isolation in all and linear LA ablation when required), while 113 underwent LA ablation alone (Group CTI−). Group CTI+ patients had smaller LA and less frequently persistent/permanent AF and linear LA ablation. Over a follow-up of 30 ± 10 months, complications (4% vs 5%, P = NS), typical Afl occurrence (1.3% and 2.6%, P = NS) and AF recurrence (25% and 28%, P = NS) were similar. Atypical Afl was more common in Group CTI− (4 vs 14%, P = 0.026). Eighty-two percent and 79% of patients in Groups CTI+ and CTI−, respectively, remained arrhythmia free in stable sinus rhythm without antiarrhythmic drug treatment (P = NS).
Conclusions: Avoiding supplementary CTI ablation in AF ablation patients without evidence of typical flutter does not result in a higher incidence of typical Afl. Despite more persistent/permanent AF and larger LA in patients without evidence of typical flutter, a strategy of selective supplementary ablation resulted in similar and low AF recurrence rates in the group without CTI ablation compared with the group with CTI ablation.     

Acute resumption of conduction in the cavotricuspid isthmus after catheter ablation in patients with common atrial flutter. Real-time evaluation and long-term follow-up.

AIMS: Cavotricuspid isthmus conduction (CIC) is closely associated with the maintenance and recurrence of common atrial flutter (AFL). This study systematically sought to assess the prevalence and characteristics of acute CIC recovery during AFL ablation and to define its predictors and its relationship with the results of long-term follow-up. METHODS AND RESULTS: A total of 124 consecutive patients (105 men, 19 women, mean age 58 +/- 11 years) who underwent successful AFL ablation were included. The procedure endpoint was defined as complete bi-directional CIC block. During an observation period of 30 min, the incidence of CIC restoration was 34.% in patients and 39.8% in applications. It increased with increasing block time and decreased over time during the observation period. Block time in successful burns followed by persistent block was shorter than in those followed by CIC resumption (12 +/- 6 vs 33 +/- 12 s, P<0.0001). A negative correlation between block time and resumption time was found (r = - 0.57, P<0.001). Patients with permanent pacemakers had a higher incidence of acute CIC resumption than those without pacemakers (5/7 vs 29/117, P = 0.007). The AFL recurrence rate was 4.8% during a mean follow-up period of 21 +/- 8 months. Our results suggest that acute CIC resumption may be a potential risk for clinical AFL recurrence during long-term follow-up. CONCLUSIONS: Acute CIC resumption in common AFL ablation varies in terms of incidence and time course. Block time has a predictive value for acute CIC recovery. Observation time can be shortened if block time is short. With longer block time, it is essential to observe for a longer period in order to minimize CIC resumption.     

The electroanatomic characteristics of the cavotricuspid isthmus: implications for the catheter ablation of atrial flutter

Introduction: Radiofrequency ablation (RFA) of typical AFL is sometimes difficult because of the poor electroanatomic approach to the cavotricuspid isthmus (CTI). The aim of this study was to correlate the anatomy of the CTI between contact mapping (NavX) and right atrial angiography (RAG), and to investigate the impact of the electroanatomic characteristics of the CTI on the RFA of typical atrial flutter (AFL).
Methods: One hundred patients with typical AFL undergoing RFA were studied. The image-guided group consisted of 50 consecutive patients with the guidance of NavX. NavX geometry and RAG were performed to investigate the morphology of the CTI. The bipolar voltages of the CTI were collected during sinus rhythm by a NavX. The control group consisted of 50 consecutive patients with the guidance of conventional fluoroscopy.
Results: There was a good correlation between the angiography and NavX for the anatomy of the CTI. The pouch type had a longer length of CTI than the flat type (33.4 ± 5.0 vs 22.6 ± 8.4 mm, P < 0.0001) and deeper depth than the concave type (6.5 ± 2.2 vs 3.7 ± 0.8 mm, P < 0.0001) on the angiography. The pouch-type CTI had a longer ablation time and larger pulses of RFA than the other two types. The control group had a longer ablation time, fluoroscopy time, and larger pulses of RFA than image-guided group.
Conclusions: The 3-D mapping system provided a good reconstruction of CTI, which may help in the RFA in patients with a complex anatomy of the CTI.     

Use of double-potential barrier to identify functional isthmus at the cavotricuspid isthmus for facilitating catheter ablation of isthmus-dependent atrial flutter

INTRODUCTION: The aim of the study was to identify an alternative target for more effective radiofrequency catheter ablation (RFCA) of isthmus-dependent atrial flutter (AFL). METHODS AND RESULTS: We hypothesized that a functional isthmus formed by preexisting double potential barrier at the cavotricuspid isthmus (CTI) could serve as a new target site for facilitating RFCA of AFL. Forty-three consecutive patients with recurrent isthmus-dependent AFL were studied using three-dimensional navigated magnetic mapping and ablation technique. Twenty patients (47%, group A) were shown to have a narrower functional channel at the CTI (functional isthmus). The remaining 23 patients did not have this feature (53%, group B). In group A, double potentials were clustered near the border of the inferior vena cava (IVC) of the CTI and served as a functional channel along the tricuspid annulus (TA). The interspike interval of double potentials was 87 +/- 26 ms near the IVC border and 45 +/- 17 ms (P < 0.0001) near the TA border of CTI. RFCA targeting at the functional isthmus in group A resulted in interruption of bidirectional transisthmus conduction with fewer radiofrequency pulses (6.7 +/- 4.7 in group A vs 21.1 +/- 17.1 pulses in group B, P < 0.001), shorter ablation line (11.6 +/- 4.0 mm vs 37.8 +/- 7.2 mm, P < 0.0001) with no arrhythmia recurrence. These functional isthmuses were found to be located at the lateral third of CTI in 12 patients, middle third in 7, and medial third in 1. This finding is different from that obtained by the conventional method in group B (lateral in 5, middle in 16, medial in 2, P < 0.038). CONCLUSION: In our study, a functional, rather than anatomic, isthmus formed by preexisting double-potential barrier at the CTI was identified in 47% of patients with isthmus-dependent AFL. It is a useful guide to facilitate RFCA of isthmus-dependent AFL.     

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

BACKGROUND: 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. OBJECTIVES: The purpose of this study was to develop a more efficacious method for ablation of isthmus-dependent atrial flutter. METHODS: 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. RESULTS: 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%). CONCLUSION: This simplified technique was feasible for creating and determining complete CTI block, with fewer RF applications required.     

Randomized comparison of cavotricuspid isthmus ablation for atrial flutter using an open irrigation-tip versus a large-tip radiofrequency ablation catheter

Ablation of Typical Atrial Flutte. Background: 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). Methods and Results: 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. Conclusions: Complete CTI block is achieved more rapidly using an LTC than an OITC, and with a similar clinical efficacy. (J Cardiovasc Electrophysiol, Vol. 22, pp. 1007‐1012, September 2011)     

Maximum electrogram-guided ablation of cavotricuspid isthmus-dependent atrial flutter

Aims

To verify and re-emphasise the efficacy of the max electrogram-guided approach for ablation of cavotricuspid isthmus (CTI)-dependent atrial flutter (AFL).

Methods

Consecutive patients were alternatively assigned to receive either conventional linear radio-frequency (RF) ablation between the tricuspid annulus and inferior vena cava (the linear approach) or RF ablation at sites with the highest electrograms (the max electrogram-guided approach). Sustained, bi-directional CTI block was the endpoint. Procedure parameters and follow-up data were obtained.

Results

In total, 80 patients were included, 40 each for the linear approach and the max electrogram-guided approach. To achieve sustained bi-directional CTI block, the linear approach needed 841 ± 594 sec or 14.0 ± 9.9 RF applications, with total fluoroscopy time of 18.6 ± 9.4 min and total procedure time of 152 ± 58 min, as compared to the max electrogram-guided approach which needed 350 ± 319 sec (p < 0.0001) or 5.8 ± 5.3 RF applications (p < 0.0001), with total fluoroscopy time of 14.8 ± 6.0 min (p < 0.05) and total procedure time of 111 ± 36 min (p < 0.0005). The CTI block was obtained with 3 or less RF applications in 18 patients in the max electrogram-guided group (45%), but only in 2 patients in the linear ablation group (5%). During follow-up of 28 ± 14 months, recurrence cases were 2 in the linear and 1 in the max electrogram-guided group (NS).

Conclusion

During ablation of AFL, directly targeting muscle bundles in the CTI as guided by the highest electrograms is more efficient than making a linear lesion across the entire CTI, since using the former approach needed less RF application, shorter fluoroscopy and procedure times than using the latter. The max electrogram-guided approach may be recommended for routine clinical use to replace the conventional linear ablation approach.     

Randomized trial of intracardiac echocardiography during cavotricuspid isthmus ablation

Randomized Trial of ICE During CTI Ablation. Introduction: Despite a high success rate, radio‐frequency ablation (RFA) of the cavotricuspid isthmus (CTI) can be unusually challenging in some cases. We postulated that visualization of the CTI with intracardiac echocardiography (ICE) could maximize the succes rate, decrease the procedure and ablation time, and minimize the radiation exposure. Methods and Results: In our prospective, randomized study, we included 102 patients scheduled for CTI ablation. We randomized patients in 2 groups: guided only by fluoroscopy (n = 52) or ICE‐guided (n = 50) group. Procedure time, fluoroscopy time, and the time spent for RFA were significantly shorter, radiation exposure (dose‐area product‐DAP) and the sum of delivered radio frequency energy were significantly lower in the ICE‐group (68.06 ± 15.09 minutes vs 105.94 ± 36.51 minutes, P < 0.001, 5.54 ± 3.77 minutes vs 18.63 ± 10.60 minutes, P < 0.001, 482.80 ± 534.12 seconds vs 779.76 ± 620.82 seconds, P = 0.001 and 397.62 ± 380.81 cGycm² vs 1,312.92 ± 1,129.28 cGycm², P < 0.001, 10,866.84 ± 6,930.84 Ws vs 16,393.56 ± 13,995.78 Ws, P = 0.048, respectively). Seven patients (13%) from the fluoroscopy‐only group crossed over to ICE‐guidance because of prolonged unsuccessful RFA and were all treated successfully. Four vascular complications and 2 recurrences were equally distributed between the 2 groups. Conclusions: ICE‐guided ablation of the CTI significantly shortens the procedure and fluoroscopy time, markedly decreases radiation exposure, and time spent for ablation in comparison with fluoroscopy‐only procedures. At the same time, visualization with ICE allowed successful ablation in challenging cases. (J Cardiovasc Electrophysiol, Vol. 23, pp. 996‐1000, September 2012)     

Prospective randomised comparison of irrigated-tip and large-tip catheter ablation of cavotricuspid isthmus-dependent atrial flutter.

BACKGROUND: Radiofrequency (RF) ablation of cavotricuspid isthmus (CTI) dependent flutter can be performed using different types of ablation catheters. It has been proposed that irrigated and large-tip catheters are capable of creating larger lesions, resulting in greater efficacy. This prospective, randomised clinical study compared the efficacy of irrigated and large-tip catheters of different designs. METHODS: Eighty patients (69 men, 66+/-11 years) undergoing de novo RF ablation of CTI-dependent flutter were randomised to ablation using one of the following catheters: (i) externally-irrigated 20), (ii) internally-cooled (n=20), (iii) single sensor, 8-mm tip (n=20), or (iv) double sensor, 8-mm tip (n=20). The study endpoint was the demonstration of bidirectional CTI conduction block within 12 min of cumulative RF delivery. Crossover to the externally-irrigated catheter was permitted if this was not achieved. The ablation and procedural parameters, safety and efficacy were compared. RESULTS: The primary endpoint was achieved in 64 patients (80%), including all 20 patients randomised to the externally-irrigated catheter. Crossover was required in 16 patients: 9 initially using the internally-cooled catheter (45%), 3 using single-sensor, 8-mm-tip (15%), and 4 using double-sensor, 8-mm-tip (20%) catheters. The higher initial failure rate with the internally-cooled-tip catheter was significant compared to the externally-irrigated (p = 0.001) and single-sensor, 8-mm-tip (p = 0.04) catheters. The externally-irrigated catheter achieved the study endpoint more frequently with fewer RF applications of shorter duration compared to the internally-cooled-tip catheter and 8-mm-tip catheters, the difference being significant compared with internally cooled ablation. No major complications were observed. CONCLUSION: Among commonly used ablation catheters, the externally-irrigated catheter has a higher efficacy for rapid achievement of CTI block.     

Evaluation of the cavotricuspid isthmus and right atrium by multidetector-row computed tomography in patients with common atrial flutter

The sizes of the right atrium (RA), cavotricuspid isthmus, and Eustachian valve are predictors of success of radiofrequency catheter ablation for atrial flutter (AFL). We examined the relationship between the sizes of cavotricuspid isthmus as measured by multidetector-row computed tomography (MDCT) and fluoroscopy. We used eight-detector MDCT to measure the tricuspid isthmus of 23 patients prior to linear ablation for common AFL. One patient with a deep pouch in the RA was excluded. Parameters measured were (1) the length of the trace of isthmus (Ti), which was equivalent to the blocking line; (2) the size of the tricuspid isthmus (DTi); and (3) the distance from the tricuspid valve and inferior vena cava (IVC) (LDTi). DTi and LDTi indicate the size of the RA, reflecting the appropriately sized steerable ablation catheter, respectively. Of the 22 patients, 21 were ablated successfully without recurrence of AFL, and clinical success was achieved in one additional patient despite failure to obtain a bidirectional block. Ti, DTi, and LDTi were correlated with fluoroscopy time (r = 0.84, r = 0.88, and r = 0.88, respectively; P < 0.0001), total delivered energy (r = 0.81, r = 0.80, and r = 0.83, respectively; P < 0.0001), and application time (r = 0.84, r = 0.80, and r = 0.87, respectively; P < 0.0001). Measurement of the tricuspid isthmus by MDCT may noninvasively provide important information for successful linear ablation.