Large tip electrodes for successful elimination of atrial flutter resistant to conventional catheter ablation

Efficacy and safety of a novel temperature-controlled catheter for cavotricuspid isthmus ablation

BACKGROUND

Maintaining an adequate temperature at the target site is essential for effective ablation. We hypothesized that a tissue temperature-controlled (T-Con) catheter for cavotricuspid isthmus (CTI) ablation could improve the procedural ablation parameters.

PURPOSE

To evaluate the efficacy and safety of the T-Con (DiamondTemp™) catheter for CTI ablation compared with non-irrigation (Non-Irri) and irrigation (Irri) catheters.

METHODS

We analyzed 150 patients who underwent prophylactic CTI ablation combined with pulmonary vein isolation. The Non-Irri, Irri, and T-Con catheter groups comprised 50 patients each, and the ablation procedural parameters and complications were compared between these groups.

RESULTS

There were no significant differences in clinical background characteristics among the three groups. The Kruskal-Wallis and post hoc tests demonstrated that the T-Con group showed the lowest total radiofrequency energy delivery time among the three groups (median [25 and 75 percentiles]: 340 [209, 357], 147 [100, 199], and 83 [61, 109] s, respectively in the Non-Irri, Irri, and T-Con groups; T-Con versus Non-Irri, p < .01; T-Con versus Irri, p < .01). The total procedural time and acute reconnection rate in the T-Con group (264 s and 4%, respectively) were lower than those in the Non-Irri group (438 s and 24%) but were similar to those in the Irri group (268 s and 6%). No significant complications were observed in any group.

CONCLUSIONS

The T-Con catheter achieved a short energy delivery time and a low acute reconnection rate, indicating its potential as an alternative catheter for CTI ablation.

Comparative Effectiveness of Various Radiofrequency Ablation Catheters in the Ablation of Typical Atrial Flutter

INTRODUCTION

Although ablation of typical atrial flutter (AFL) can be easily achieved with radiofrequency energy (RF), no studies compare the effectiveness of different ablation catheters. Our study aimed to compare the efficacy of various types of ablation catheters in treating typical AFL.

METHODS

We analyzed patients with AFL who underwent RF ablation by a single operator at our institution. Successful ablation was evidenced by a bidirectional conduction block (trans-isthmus conduction time ≥ 130 ms or double potentials ≥ 90 ms). Logistic regression was used to compare success rate and linear regression to compare lesion time.

RESULTS

Out of 222 patients, only six did not meet the success criteria (2.7%). The catheters used were non-irrigated, large-tip, internally irrigated (Chili II Boston Scientific), and externally irrigated (non-force-sensing) catheters (Cool Path, Abbott). An externally irrigated force-sensing catheter (TactiCath, Abbott) was used with > 10 gm of force and (LPLD) setting (30 W- 45 °C- 60 s), and high-power short-duration (HPSD) setting (50 W- 43 °C - 12 s). No complications were encountered. The catheter type had no statistically significant association with ablation success. With the use of externally irrigated catheter with contract force-sensing and HPSD settings, statistically significantly shortening of lesion time was achieved 758.3 s, [CI - 1128.29, - 388.35 s] followed by LPLD by 419.0 s [CI - 808.49, - 29.47 s].

CONCLUSIONS

The typical atrial flutter radiofrequency ablation procedure had a high success rate, which was not influenced by the type of ablation catheter. Contact force ablation catheter and HPSD are associated with shorter total lesion time.

Comparison between the novel diamond temp and the classical 8-mm tip ablation catheters in the setting of typical atrial flutter

PURPOSE

Radiofrequency (RF) catheter ablation is widely accepted as a first-line therapy for cavotricuspid isthmus (CTI)-dependent atrial flutter (AFL). The novel DiamondTemp (DT) catheter with temperature feedback during RF ablation has been released recently on the market. The purpose of this study was to evaluate the impact of DiamondTemp (DT) technology on ablation efficiency during AFL.

METHODS

In this single-center study, 30 consecutive patients with typical AFL indicated to ablation of CTI were included. The first 15 patients underwent CTI ablation using 8-mm tip catheter, and the following 15 patients underwent temperature-controlled RF ablation using DT catheter. The endpoints were number and mean total duration of RF applications, mean temperature reached in the setting of CTI, procedural times, and fluoroscopy times.

RESULTS

There were no significant differences between the two groups concerning baseline characteristics. Mean duration of the each application (71.5 s ± 30.6 vs 12.4 s ± 13.2, p value < 0.001), mean total duration of RF applications (517,73 s ± 377,96 vs 112,8 s ± 43,58; p value < 0.001), procedural times (51.6 min ± 24.2 vs 38.6 ± 8.2; p = 0.03), and fluoroscopy times (16.2 min ± 10.2 vs 8 min ± 4.24; p = 0.005) were longer in the 8-mm ablation catheter group. Mean temperature measurements (51.9 °C ± 3.59 vs 56.7 °C ± 3.34, p value < 0.003) were as well lower in the 8-mm ablation catheter group.

CONCLUSIONS

Catheter ablation of CTI-dependent AFL by means of DT resulted in a significant reduction of total and single application RF delivery time, procedure, and fluoroscopy times.

Current treatment options for atrial flutter and results with cryocatheter ablation

Rhythm disturbances arising in the upper chambers of the heart are not uncommon. They are associated with a heavy burden of illness for the affected individual, as well as society in general. Atrial flutter, a re-entrant atrial tachycardia, is one such rhythm disturbance. The objective of this review article is twofold: first, to provide a brief insight into atrial flutter and the typical treatments for this arrhythmia in clinical practice; and second, to give an in-depth account of cryocatheter ablation as a relatively new treatment option for this potentially debilitating condition. The many recent clinical studies documenting the use of cryocatheter ablation for treatment of atrial flutter are presented, and their results briefly discussed. Overall, as cryocatheter ablation embeds itself among the arsenal of treatments for atrial flutter, the promising results from clinical studies appear destined to elevate cryocatheter ablation to a premier position among the treatment options for atrial flutter.

Usefulness of pre-procedure cavotricuspid isthmus imaging by modified transthoracic echocardiography for predicting outcome of isthmus-dependent atrial flutter ablation

BACKGROUND

Anatomic characteristics of the cavotricuspid isthmus (CTI) have been reported to be related to the outcome of atrial flutter ablation therapy. However, preprocedural evaluation of CTI anatomy using modified transthoracic echocardiography to guide atrial flutter ablation has not been well described.

METHODS

Transthoracic echocardiography was prospectively performed before atrial flutter ablation in 42 patients with typical CTI-dependent atrial flutter. A modified apical long-axis view was designed to visualize and evaluate anatomic characteristics of the CTI and Eustachian ridge (ER). A prominent ER, extending from the inferior vena cava to the interatrial septum, is defined as an extensive ER.

RESULTS

Twenty-eight patients had straightforward ablation procedures, and 14 patients had difficult ablation procedures. Two patients with difficult procedures had unsuccessful ablation. Multivariate analysis (using CTI length, the presence of a pouch or recess, ER morphology, and significant tricuspid regurgitation as variables) showed that the presence of extensive ER was the only independent predictor of a difficult ablation procedure. The ablation time in patients with extensive ER (n = 13) was significantly longer than in those patients with nonextensive ER (n = 29) (1,638.4 ± 1,548.3 vs 413.8 ± 195.5 sec, P = .015). The incidence of difficulty in achieving bidirectional isthmus block was also higher in patients with extensive ER (10 of 13 vs four of 29, P < .001).

CONCLUSION

Preprocedural transthoracic echocardiography using a modified apical long-axis view is useful to characterize the morphology of the CTI and the ER. An extensive ER is a strong predictor for difficult ablation of CTI-dependent atrial flutter.

Comparison of 8-mm-tip and irrigated-tip catheters in the ablation of isthmus-dependent atrial flutter: a prospective randomized trial

INTRODUCTION AND OBJECTIVES

Both 8-mm-tip and irrigated-tip catheters improve outcomes in typical atrial flutter ablation. However, it is not yet known which is preferable. The objective was to compare the effectiveness of 8-mm-tip (Group 1) and open irrigated-tip (Group 2) catheters in the first ablation attempt.

METHODS

A prospective randomized trial with a long-term follow-up was performed in patients with documented typical atrial flutter. For both types of catheter, the power was initially set to 50 W. The primary endpoint was ablation of the cavotricuspid isthmus in a procedure lasting, at most, 600 s.

RESULTS

Group 1 contained 65 patients and Group 2 contained 66, with no significant intergroup difference in baseline characteristics. Their mean age was 63+/-12 years, 80% were men, and 65% had structural heart disease. The primary endpoint was achieved in 48 patients (73.8%) in Group 1 and 49 (74.2%) in Group 2 (P=NS). In the remaining patients, the procedure was continued at the physician's discretion and ablation was finally achieved in all cases. In the intention-to-treat analysis, there was no significant difference between the groups in the number of applications of the ablation device or in the duration of the ablation procedure, radioscopy or the total procedure. By 16+/-5 months of follow-up (>1 year in 98%), 8 (6.3%) patients had experienced recurrence and 95 (74.2%) were free from any arrhythmia. There was no differences between the groups.

CONCLUSIONS

No difference was found between the effectiveness of 8-mm-tip and open irrigated-tip catheters in the first attempt at ablation of typical atrial flutter.

Robotic versus conventional ablation for common-type atrial flutter: a prospective randomized trial to evaluate the effectiveness of remote catheter navigation

BACKGROUND

Conventional catheter ablation for common-type atrial flutter (AFL) is a widely established therapy but has not been compared with the use of a robotic navigation system (RNS) thus far.

OBJECTIVES

The purpose of this study was to investigate the feasibility of a new, nonmagnetic RNS with regard to safety, efficacy, and X-ray exposure to investigator and patient compared with the conventional ablation approach in patients with AFL.

METHODS

Fifty patients (65.7 +/- 9.3 years, 40 male) undergoing de novo catheter ablation for AFL were randomly assigned to conventional or RNS-guided cavotricuspid isthmus (CTI) ablation.

RESULTS

Complete bidirectional isthmus block was achieved for all patients without occurrence of procedure-related complications. The fluoroscopy time and the investigator X-ray exposure (8.2 +/- 4.6 vs. 5.8 +/- 3.6, P = .038; and 8.2 +/- 4.6 vs. 1.9 +/- 1.1 minutes, P<.001) as well as the mean radiofrequency (RF) duration and the energy delivered were significantly higher in the conventional than in the RNS group (321.7 +/- 214.6 vs. 496.4 +/- 213.9 seconds, P = .006; 8279 +/- 5767 vs. 16,308 +/- 6870 J, P<.001, respectively). The overall procedure time in the RNS group was significantly longer than in the conventional group (79.2 +/- 30.6 vs. 58.4 +/- 17.7 minutes; P = .04) but significantly decreased comparing the first 10 with the last 10 patients in the RNS group (105.3 +/- 34.8 vs. 60.6 +/- 6.3 minutes; P = .003). Starting ablation during AFL, bidirectional block instantly after termination was observed in 90% of the RNS and 50% of the conventionally treated patients (P = .03).

CONCLUSION

The present study demonstrates the safety and feasibility of RNS for performing CTI ablation in patients with common-type AFL for use in the clinical routine. As a result of the remote navigation, X-ray exposure and RF duration to achieve bidirectional block were significantly decreased and occurred more often immediately after AFL termination. These findings are consistent with increased catheter stability and RF application efficacy using RNS compared with conventional catheter manipulation.

Atrial flutter: a focus on treatment options for a common supraventricular tachyarrhythmia

Atrial flutter (AFl), a re-entrant atrial tachycardia, is a cardiac rhythm disturbance that arises in the upper chambers of the heart. This usually non-life-threatening condition can be treated by a number of medical intervention strategies, which include electrical cardioversion, pharmacological therapy, and catheter ablation. These options have been available in clinical practice for a number of years. However, catheter ablation, in the form of radiofrequency catheter ablation and cryo catheter ablation, is increasingly utilised as a first-line treatment option for AFl in certain patients. The purpose of this review article is two-fold: first, to briefly present an overview of AFl and the more familiar treatment options for this arrhythmia, and second to provide more in-depth coverage of catheter ablation technologies as a treatment option for patients with AFl. As part of the latter objective, recent clinical studies documenting the use of radiofrequency catheter ablation and cryo catheter ablation for AFl are presented and their results briefly discussed.

Rapid Ablation for Atrial Flutter by Targeting Maximum Voltage?Factors Associated with Short Ablation Times

BACKGROUND

The maximum voltage-guided (MVG) approach to ablation for atrial flutter targets high-amplitude signals along the cavotricuspid isthmus (CTI). It is based on the observation that the isthmus is often composed of bundles of conducting tissue and the hypothesis that these bundles manifest as high-amplitude electrograms, providing targets for selective ablation. We aim to identify patient and procedural factors that correlate with rapid isthmus ablation.

METHODS

All patients undergoing CTI ablation at our center from January 2005 to May 2006 were included. Patients were divided into outcome groups relative to the median value for total ablation time. The two groups were compared according to patient and procedural variables, using multivariate regression methods.

RESULTS

Seventy-six patients were assessed with mean age 60.2 +/- 10.6 years; 63 (82.9%) were male. Mean ablation time to bidirectional block across the CTI was 6.85 +/- 5.87 min (range 0.68-28.7); median 4.77 min. Seventy-six percent of patients required less than 5 min total ablation time until bidirectional block was achieved. Variables independently associated with a short ablation time were the presence of sinus rhythm at start of ablation (P = 0.0050, odds ratio (OR) 8.03), high mean temperature among all ablations (P = 0.019, OR 17.81), and low variability of mean power among all ablations (P = 0.0048, OR 19.26).

CONCLUSIONS

Using the MVG approach to atrial flutter ablation, shorter total ablation times are observed among patients in sinus rhythm at the onset of ablation, with higher mean temperature among ablation lesions, and less variability of power between ablations.

Is it possible to create a linear lesion with no local electrograms? Comparison between a three-dimensional mapping system and conventional fluoroscopy for cavotricuspid isthmus ablation of typical atrial flutter

OBJECTIVE

The aim of this prospective, randomised study was to evaluate the efficacy, safety and long-term outcomes of the complete disappearance of local electrograms along the linear lesion using the EnSite NavX three-dimensional mapping system as compared with conventional fluoroscopy for ablation of typical atrial flutter (AFL).

METHODS

Seventy-three patients with spontaneous AFL episodes were randomised to undergo fluoroscopy-guided (group I, n=35) or EnSite NavX-guided (group II, n=38) ablation. When bidirectional isthmus block was achieved, the catheter was navigated back along the ablation line to assess the presence of local potentials along the lesion line.

RESULTS

Bidirectional isthmus block was achieved in all patients. Mean total fluoroscopy time was 19.8 +/- 4.1 min in group I and 9.1 +/- 3.5 min in group II (P<0.001); mean fluoroscopy time required for radiofrequency ablation was 6.9 +/- 1.4 min in group I and 0.6 +/- 0.3 min in group II (P<0.001). During a follow-up of 16 +/- 9 months, three patients in group I (10%) experienced recurrence of AFL as opposed to none in group II (P<0.005).

CONCLUSIONS

NavX technology allows accurate re-navigation of the lesion line to assess the presence of local potentials during an ablation procedure for typical AFL. Electroanatomic activation mapping can accurately identify gaps in the linear radiofrequency lesion with no AFL recurrence compared with 20% of recurrences after a standard procedure.

Is it possible to perform a linear lesion with no local electrograms using a three-dimensional mapping system for the ablation of typical atrial flutter?

AIMS

A randomized prospective study to evaluate the efficacy, safety and long-term outcomes of the complete disappearance of local electrograms along the linear lesion using the EnSite NavX three-dimensional mapping system compared to the conventional fluoroscopy-based mapping for the ablation of typical atrial flutter (AFL).

METHODS

83 patients with spontaneous AFL episodes were randomized to the conventional procedure (group I, 41 patients) or to the EnSite NavX three-dimensional mapping system (group II, 42 patients). When bidirectional block was achieved, a renavigation of the ablation line was performed to verify the absence of local potentials along the line.

RESULTS

In all patients, bidirectional isthmus block was achieved. Total mean fluoroscopy time was 19.8 +/- 4.1 min and 9.1 +/- 3.5 min (p < 0.001) and radiofrequency (RF) mean fluoroscopy time was 6.9 +/- 1.4 min and 0.6 +/- 0.3 min (p < 0.001), respectively, in group I and II. During long-term follow-up of 16 +/- 9 months, there were 4 (10%) AFL recurrences in group I and 0 in group II (p < 0.005).

CONCLUSION

NavX accurately renavigates the lesion line and verifies local potentials. The electro-anatomic activation map accurately identifies gaps in the RF lesion line and no recurrences were found compared with 10% recurrences after standard procedures for typical AFL.

Success rate of catheter ablation in atrial flutter: comparison of a 4- or 5-mm tip electrode catheter with an 8-mm tip electrode catheter

BACKGROUND

Radio frequency (RF) energy is capable of interrupting the reentrant circuit of atrial flutter and curing the arrhythmia. The development of 8-mm tip catheter provides more tissue damage and has offered the promise of improved success. The purpose of our study was to determine if the acute and long-term success with the 8-mm tips were superior to the 4- or 5-mm tips.

MATERIALS AND METHODS

The outcomes of the first 20 patients in whom an 8-mm tip catheter was used were compared with the previous 20 patients in whom a 4-or 5-mm tip catheter was used. Procedural (acute) ablation success was defined by creation of bi-directional isthmus block. Long-term success was defined as the prevention of clinically evident atrial flutter (AFl) as determined by the absence of symptoms or maintenance of sinus rhythm on electrocardiogram, six months to one year after the procedure.

RESULTS

Compared to the 4- or 5-mm tip, the 8-mm catheter tip was associated with a reduced ablation duration {22.3 +/- 16 versus 11.5 +/- 5 min (p = 0.0078)}, a lower mean number of ablations {13.5 +/- 9.9 versus 6.8 +/- 2.9 (p = 0.0065)} and a reduced procedure time {1.8 +/- 0.7 versus 1.1 +/- 0.5 h (p = 0.0032)}. Acute success was 95% in the 4- or 5-mm group versus 80% in the 8-mm group (p = NS), but long-term success was higher in the 8-mm group than the 4- or 5-mm group (87.5 versus 63.2%, p = 0.0436).

CONCLUSIONS

Eight-millimeter tip catheters for AFl shorten procedure time, reduce the duration and number of ablations and accomplish bi-directional block when compared with smaller tipped catheters. The long-term success rate is better with the 8-mm tips and should be the preferred catheter for RF ablation of AFl.

Comparison Between a 7 French 6 MM Tip Cryothermal Catheter and a 9 French 8 MM Tip Cryothermal Catheter for Cryoablation Treatment of Common Atrial Flutter

BACKGROUND

Larger tipped cryothermal catheters may deliver efficacy and procedure benefits in the treatment of patients with atrial flutter.

OBJECTIVE

To compare 7 French 6 mm and 9 French 8 mm tip cryothermal catheters (Freezor, Xtra or Freezor, MAX, CryoCath Technologies Inc., Kirkland, Canada) in terms of acute and chronic efficacy, and procedure characteristics in the treatment of atrial flutter.

METHODS

This non-randomized clinical investigation determined bi-directional isthmus block at intervention, procedure characteristics, and symptom and conduction recurrence rates post procedure in consecutive patients with symptomatic atrial flutter ablated either with the 7 French 6 mm tip cryothermal catheter (n = 43) at -75 degrees C for 4 minutes or the 9 French 8 mm tip cryothermal catheter (n = 51) at -75 degrees C for 8 minutes.

RESULTS

Clinical data showed a higher acute success rate for the larger tipped catheter (100% vs. 88%). Symptom recurrence rates were 0% for both catheters at 3, 6, and 9 month follow-up. Conduction recurrence rates were similar for both catheters on repeat electrophysiological study at 3 months post procedure (35% vs. 32%). Procedure benefits were fewer cryotests (20 +/- 17 vs. 26 +/- 21) and ablations (4 +/- 4 vs. 12 +/- 18), and shorter procedure (80 +/- 61 min vs. 87 +/- 48 min), fluoroscopy (14 +/- 9 min vs. 24 +/- 10 min), and cryoapplication times (37 +/- 18 min vs. 44 +/- 23 min) with the larger tipped catheter. There were no adverse events reported.

CONCLUSIONS

Clinical results showed differences in catheter performance that favoured the larger tipped catheter. However, increased acute success rate did not translate into reduced conduction recurrence rate post ablation, although clinical recurrence was completely absent long-term.

Correlation of atrial electrocardiographic amplitude with radiofrequency energy required to ablate cavotricuspid isthmus-dependent atrial flutter

OBJECTIVES

The purpose of this study was to evaluate a possible correlation between atrial ECG amplitude in common atrial flutter (AFL) and radiofrequency (RF) energy required to achieve cavotricuspid isthmus block.

BACKGROUND

The amount of RF delivery required for ablation of typical AFL is variable. This variation has been attributed to the cavotricuspid isthmus anatomy. Atrial ECG amplitude can be a marker of atrial anatomic variations and therefore may correlate with RF duration required to achieve cavotricuspid isthmus block.

METHODS

Seventy consecutive patients were prospectively studied. Ablation of the cavotricuspid isthmus was performed by creating a line of block between the inferior tricuspid annulus and the inferior caval vein using 8-mm-tip electrode catheters. If more than 20 minutes of RF time was required to achieve conduction block, the catheter was changed to an irrigated-tip catheter. Atrial ECG amplitude was assessed in leads II, III, aVF, and aVL.

RESULTS

A total of 14 +/- 11 minutes of RF energy was delivered to achieve block in all patients; 12 patients (8%) required more than 20 minutes. Atrial ECG amplitude showed highly significant correlations with cumulative RF energy (F and P waves in lead II: r = 0.703 and r = 0.737, P < .001). P-wave amplitude <0.2 mV and/or flutter wave amplitude <0.35 mV in lead II have a high negative predictive value to predict <20 min RF delivery (96% and 89% respectively).

CONCLUSIONS

A significant correlation exists between atrial ECG amplitude and amount of RF required to ablate typical AFL. Atrial ECG amplitude may be a surrogate marker of characteristics of isthmus anatomy. These findings may influence the choice of catheter used for cavotricuspid isthmus ablation.

Pattern of Isthmus Conduction Recovery Using Open Cooled and Solid Large‐Tip Catheters for Radiofrequency Ablation of Typical Atrial Flutter

INTRODUCTION

Open cooled-tip and solid 8-mm-tip catheters have demonstrated safety and effectiveness for radiofrequency current (RFC) ablation of typical atrial flutter (AFL). However, data from prospective and randomized studies in this setting are lacking.

METHODS AND RESULTS

One hundred thirty consecutive patients (104 men; 61 +/- 11 years) with AFL were randomized to undergo RFC catheter ablation either using a solid 8-mm-tip catheter (group A, 65 degrees C, 70 W, 60 s) or an open irrigated-tip catheter (group B, 65 degrees C, 50 W, 60 s, 17 mL/min flow). Endpoint was bidirectional conduction isthmus block. In cases of repeated (two times) transient isthmus block, the catheter was changed (crossed over) to the catheter used in the other randomization arm, but patients remained in the original group following intention-to-treat analysis. The selected endpoint could be achieved in all patients after 12 +/- 6 RFC pulses in group A and 10 +/- 7 RFC pulses in group B (P = 0.11). Procedure times were longer (159 +/- 38 min vs 138 +/- 37 min, P = 0.002) and x-ray exposures higher in group A (fluoroscopy time 25 +/- 17 min vs 21 +/- 10 min, P = 0.08; x-ray dosage 3,133 +/- 2,576 cGy.cm2 vs 2,326 +/- 1,405 cGy.cm2, P = 0.03). Transient isthmus block was observed in 23 group A patients and 12 group B patients (P = 0.03). Onset time of transient isthmus block ranged from 0.5 to 27 minutes. Repeated transient isthmus block occurred in 8 of the 23 patients in group A after 19 +/- 3 RFC applications. After crossover to the cooled-tip catheter, the endpoint was reached another 5 +/- 1 RFC pulses. In group B, all patients could be treated without change of ablation catheter. After a follow-up of 14 +/- 2 months, 2 patients (3%) in group A and 1 patient (1.5%) in group B presented with AFL recurrence.

CONCLUSION

Open cooled-tip catheters are more effective than solid large-tip catheters for AFL ablation. The greater effectiveness is evident in cases showing repeated conduction recovery within the cavotricuspid isthmus. Primary use of open irrigated-tip catheters should be considered for AFL ablation.

Catheter Ablation of Common‐Type Atrial Flutter Guided by Three‐Dimensional Right Atrial Geometry Reconstruction and Catheter Tracking Using Cutaneous Patches:

INTRODUCTION

EnSite NavX (NavX) is a novel mapping and navigation system that allows visualization of conventional catheters for diagnostic and ablative purposes and uses them to create a three-dimensional (3D) geometry of the heart. NavX is particularly suitable for ablation procedures utilizing an anatomic approach, as in the setting of common-type atrial flutter (AFL). The aim of this study was to compare NavX-guided and conventional ablation procedures for AFL.

METHODS AND RESULTS

Forty consecutive patients (32 male, 59 +/- 12 years) with documented AFL were randomized to undergo fluoroscopy-guided (group I, 20 patients) or NavX-guided (group II, 20 patients) ablation, including 3D isthmus reconstruction. The same catheter setup was used in both groups. The endpoint of bidirectional isthmus block was obtained in all patients. Compared to conventional approaches, NavX-guided procedures significantly reduced fluoroscopy time (5.1 +/- 1.4 min vs 20 +/- 11 min, P < 0.01) and total x-ray exposure (5.1 +/- 3.1 Gycm2 vs 24.9 +/- 1.6 Gycm2, P < 0.01). Isthmus geometry reconstruction could be performed in all patients of group II. In 4 patients (20%) of group II, anatomic isthmus variations were detected by NavX. No significant differences in radiofrequency current applications and procedural times were found between the two groups.

CONCLUSION

NavX technology allows geometry reconstruction of the cavotricuspid isthmus. NavX-guided ablation of AFL reduces total x-ray exposure compared to the fluoroscopy-guided approach but does not prolong procedure time.

Optimizing RF Output for Cooled RF Ablation

Cooled RF ablation catheters increase lesion size and facilitate ablation compared to standard RF ablation catheters. Cooling the ablation electrode increases the disparity between tissue temperature and electrode temperature, making use of temperature for guiding power application during ablation of less certain value. Appropriate energy titration is important, however, to produce large lesions, while avoiding overheating of tissue with steam formation leading to "pops." In addition to power, the rate of irrigant flow can be controlled. Electrode-tissue contact and orientation and the cooling effect of blood flow around the electrode and within the tissue are not as easily adjusted and also influence tissue heating. In addition to electrode temperature, a decrease in impedance, bubble formation detected by intracardiac ultrasound, and evidence of tissue heating from an effect on recorded electrograms or the arrhythmia can be used to guide ablation energy. Guidelines for adjusting power delivery and avoiding "pops" and coagulum formation are suggested.