Acute and long-term effects of consecutive radiofrequency applications on conduction properties of the subeustachian isthmus in type I atrial flutter

Ablation of typical atrial flutter using mini electrode measurements for maximum voltage‐guided ablation: A randomized, controlled trial

Background

Novel ablation catheters with mini electrode (ME) sensing have become available but their utility is unclear. We investigated whether ablation of the cavotricuspid isthmus (CTI) for atrial flutter (AFL) would be improved using ME signals.

Methods

Sixty‐one patients (76% male, 63 ± 10 years) with CTI‐dependent AFL underwent ablation using a maximum voltage‐guided approach, randomized to either standard 8 mm non‐irrigated catheter with bipolar signals or IntellaTip MiFi catheter using ME signals alone.

Results

Acute bidirectional block was achieved in 97%. Mean follow‐up was 16.7 ± 10 months. The median number of ablation lesions was 13 in both groups (range 3–62 vs. 1–43, p = .85). No significant differences were observed in AFL recurrences (17% vs. 11%, p = .7), median procedure durations (97 min [interquartile range (IQR), 71–121] vs. 87 min [IQR, 72–107], p = .55) or fluoroscopy times (31 min [IQR, 21–52] vs. 38 min [IQR, 25–70], p = .56). Amplitudes of ME signals were on average 160% greater than blinded bipolar signals. In 23.7% of lesions where bipolar signals were difficult to interpret, 13.6% showed a clear ME signal.

Conclusions

There was no difference in the effectiveness of CTI ablation guided by ME signals, compared with using bipolar signals from a standard 8 mm ablation catheter. While ME signal amplitudes were larger and sometimes present when the bipolar signal was unclear, this did not improve procedural characteristics or outcomes. The results suggest future research should focus on lesion integrity rather than signal sensing.

Interest of waiting time for spontaneous early reconnection after cavotricuspid isthmus ablation: A monocentric randomized trial

INTRODUCTION

The aim of this study was to determine the rate of recurrent atrial flutter (AFl) after isolated cavotricuspid isthmus (CTI) ablation and to evaluate the impact of a waiting period with the search for early resumption of the CTI block on the long-term outcome.

METHOD

Three hundred and nineteen consecutive patients referred for typical AFl ablation were randomly assigned to CTI ablation with continuous reevaluation of the CTI block during 30 minutes and early reablation if needed (waiting time [WT] + group, n  =  155) or to CTI ablation with no waiting period after proven bidirectional CTI block (WT - group, n  =  164). All patients were regularly followed-up.

RESULT

In the WT+ group, 10 patients (6%) presented a recovery across the CTI (time to recovery: 17 ± 7') and were reablated at the end of the waiting period. After a median follow-up of 21 months, the rate of recurrent AFl was significantly higher in the WT - group as compared to the WT+ group (11.6% [19/164] vs 2.5% [4/155], respectively; P  =  0.007). However, no significant differences in the subsequent rate of AF were observed between the two groups (29% [WT -] vs 32% [WT+], P  =  0.66). During the follow-up, 28 patients from the WT - group underwent a second ablation procedure (16 AFl redo and 12 AF ablation) versus 10 patients form the WT+ group (three AFl redo and seven AF ablation).

CONCLUSION

Waiting 30 minutes after CTI ablation to check for early resumption and early reablation allows for decreasing significantly the rate of recurrent atrial flutter.

A review on atrioventricular junction ablation and pacing for heart rate control of atrial fibrillation

Atrioventricular junction ablation with permanent pacemaker implantation is a highly effective treatment approach in patients with atrial fibrillation and high ventricular rates resistant to other treatment modalities, especially in the elderly or those with severe comorbidities. Compared with pharmacological therapy alone, the so-called “ablate and pace” approach offers the potential for more robust control of ventricular rate. Atrioventricular junction ablation and pacing strategy is associated with improvement in symptoms, quality of life, and exercise capacity. Given the close relationship between atrial fibrillation and heart failure, there is a particular benefit of such a rate control in patients with atrial fibrillation and reduced systolic function. There is increasing evidence that cardiac resynchronization therapy devices may be beneficial in selected populations after atrioventricular junction ablation. The present review article focuses on the current recommendations for atrioventricular junction ablation and pacing for heart rate control in patients with atrial fibrillation. The technique, the optimal implantation time, and the proper device selection after atrioventricular junction ablation are also discussed.

Two-dimensional echocardiographic features of the inferior right atrial isthmus: the role of vestibular thickness in catheter ablation of atrial flutter

OBJECTIVES

The aim of this study was to examine the feasibility of transthoracic two-dimensional (2D)-echocardiography in defining the cavo-tricuspid isthmus (CTI) anatomy and its value concerning the ease of catheter ablation of isthmic atrial flutter (AF).

METHODS

CTI analysis was accomplished in 39 cases: 16 necropsy specimens and 23 patients. Sixteen were patients with isthmus-dependent AF and seven controls with other supraventricular re-entrant tachycardias. Two-dimensional transthoracic echocardiography and a right atrium angiogram were performed before radiofrequency catheter ablation (RFCA).

RESULTS

The measurements of the CTI with angiography were compared with those taken with echocardiography and correlation was excellent (r= 0.91; P < 0.0001). In normal patients, the dimension of the vestibular thickness was successfully compared and validated with the histological examination of the necropsy specimens: histology median 6.8 mm, range 4.4-10.5 vs. echo median 6.2 mm, range 5.4-8.7; P: NS. Vestibular thickness was greater in complex than in simple RFCA (13.6 ± 1.9 mm vs. 10.0 ± 2.3 mm; P = 0.01). When vestibular thickness ≥11.5 mm, the ablation prone to be complex (sensitivity 83.3%, specificity 80%, positive predictive value 71.4%, and negative predictive value 88.9%).

CONCLUSIONS

Two-dimensional transthoracic echocardiography clearly depicts the inferior isthmus and, displaying the thickness of the tricuspid vestibule, it was related with complexity of the ablation procedure in isthmus-dependent AF.

Adenosine testing in atrial flutter ablation: unmasking of dormant conduction across the cavotricuspid isthmus and risk of recurrence

BACKGROUND

Adenosine-induced hyperpolarization may identify pulmonary veins at risk of reconnection following electrical isolation for atrial fibrillation. The potential role of adenosine testing in other arrhythmic substrates, such as cavotricuspid isthmus (CTI)-dependent atrial flutter, remains unclear. We assessed whether dormant conduction across the CTI may be revealed by adenosine after ablation-induced bidirectional block, and its association with recurrent flutter.

METHODS AND RESULTS

Patients undergoing catheter ablation for CTI-dependent flutter were prospectively studied. After confirming bidirectional block across the CTI by standard pacing maneuvers, adenosine (≥ 12 mg IV) was administered to assess resumption of conduction, followed by isoproterenol (ISP) bolus. Further CTI ablation was performed for persistent (but not transient) resumption of conduction. Bidirectional block across the CTI was achieved in all 81 patients (63 males), age 61.2 ± 11.0 years. The trans-CTI time increased from 71.9 ± 18.1 milliseconds preablation to 166.2 ± 26.4 milliseconds postablation. Adenosine elicited resumption of conduction across the CTI in 7 patients (8.6%), 2 of whom had transient recovery. No additional patient with dormant conduction was identified by ISP. Over a follow-up of 11.8 ± 8.0 months, atrial flutter recurred in 4 (4.9%) patients, 3/7(42.9%) with a positive adenosine challenge versus 1/74 (1.3%) with a negative response, P = 0.0016 (relative risk 31.7).

CONCLUSION

Adenosine challenge following atrial flutter ablation provoked transient or persistent resumption of conduction across the CTI in almost 9% of patients and identified a subgroup at higher risk of flutter recurrence. It remains to be determined whether additional ablation guided by adenosine testing during the index procedure may further improve procedural outcomes.

Catheter ablation of scar-related atypical atrial flutter

AIMS

The aim of the study was to assess the impact of isthmus location of atypical atrial flutters/atrial tachycardias (ATs) on outcomes of catheter ablation. Atrial tachycardias are clinically challenging arrhythmias that can occur in the presence of atrial scar--often due to either cardiac surgery or prior ablation for atrial fibrillation. We previously demonstrated a catheter ablation approach employing rapid multielectrode activation mapping with targeted entrainment manoeuvrs. However, the role that AT isthmus location plays in acute and long-term success of ablation remains uncertain.

METHODS AND RESULTS

Retrospective multicenter analysis of 91 consecutive AT patients undergoing ablation using a systematic four-step approach: (i) high-density activation mapping; (ii) analysis of atrial activation to identify wavefronts of electrical propagation; (iii) targeted entrainment of putative channels; and (iv) irrigated radiofrequency ablation of constrained regions of the circuit. Clinical outcomes, procedural details, and clinical profiles were determined. A total of 171 ATs (1.9 ± 1.0 per patient, 26% septal ATs) were targeted for ablation. The acute success rates were 97 and 77% for patients with either non-septal ATs or septal ATs, respectively (P = 0.0023). Similarly, the long-term success rates were 82 and 67% for patients with either no septal ATs or at least one septal AT, respectively (P = 0.1057). The long-term success rates were 75, 88, and 57% for patients with ATs associated with prior catheter ablation, cardiac surgery or MAZE, and idiopathic atrial scar, respectively.

CONCLUSION

Catheter ablation of AT can be successfully performed employing a strategy of combined high-density activation and entrainment mapping. Septal ATs are associated with higher rates of acute and long-term recurrences.

Lessons from dissociated pulmonary vein potentials: entry block implies exit block

Aims

Prior reports using pacing manoeuvres, demonstrated an up to 42% prevalence of residual pulmonary vein to left atrium (PV–LA) exit conduction after apparent LA–PV entry block. We aimed to determine in a two-centre study the prevalence of residual PV–LA exit conduction in the presence of unambiguously proven entry block and without pacing manoeuvres.

Methods and results

Of 378 patients, 132 (35%) exhibited spontaneous pulmonary vein (PV) potentials following circumferential PV isolation guided by three-dimensional mapping and a circular mapping catheter. Pulmonary vein automaticity was regarded as unambiguous proof of LA–PV entry block. We determined the prevalence of spontaneous exit conduction of the spontaneous PV potentials toward the LA. Pulmonary vein automaticity was observed in 171 PVs: 61 right superior PV, 33 right inferior PV, 47 left superior PV, and 30 left inferior PV. Cycle length of the PV automaticity was >1000 ms in all cases. Spontaneous PV–LA exit conduction was observed in one of 171 PVs (0.6%). In a subset of 69 PVs, pacing from within the PV invariably confirmed PVLA exit block.

Conclusion

Unidirectional block at the LA–PV junction is unusual (0.6%). This observation is supportive of LA–PV entry block as a sufficient electrophysiological endpoint for PV isolation.

Catheter ablation of atrial arrhythmias: state of the art

Catheter ablation is at the forefront of the management of a range of atrial arrhythmias. In this Series paper, we discuss the underlying mechanisms and the current role of catheter ablation for the three most common atrial arrhythmias encountered in clinical practice: focal atrial tachycardia, atrial flutter, and atrial fibrillation. The mechanisms of focal atrial tachycardia and atrial flutter are well understood, and these arrhythmias are amenable to curative catheter ablation with high success rates. In most cases, paroxysmal atrial fibrillation is initiated by triggers located within pulmonary vein musculature. Circumferential ablation to isolate this musculature is associated with high success rates for elimination of paroxysmal atrial fibrillation in selected populations. Because of the problem of recurrent pulmonary vein connection, more than one procedure will be needed in about 30% of patients, and new technologies are being developed to reduce this occurrence. The mechanisms that sustain persistent atrial fibrillation are not well understood and are the subject of continuing investigation. As such, ablation approaches and technologies for this arrhythmia are still evolving.

Evaluation of the surface ECG in detecting isthmus conduction block after ablation of typical atrial flutter

OBJECTIVES

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.

METHODS

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).

RESULTS

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%.

CONCLUSIONS

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.

Meta-analysis of ablation of atrial flutter and supraventricular tachycardia

The purpose of this study was to perform a systematic review and meta-analysis to evaluate the safety and efficacy of radiofrequency ablation (RFA) of typical atrial flutter (AFL) and atrioventricular node-dependent supraventricular tachycardia (SVT) in adult patients. Medline and EMBASE were searched (1990 to 2007) for all study design trials of RFA. Data relating to single- and multiple-procedure success, arrhythmia recurrence, repeat ablation, adverse events, and death were extracted. For RFA in AFL, 18 primary studies with 22 treatment arms and 1,323 patients were identified. Single-procedure success for AFL was 91.7% (95% confidence interval [CI] 88.4% to 94.9%). Multiple-procedure success was 97.0% (95% CI 94.7% to 99.4%). Postablation arrhythmia was noted in 13.2% of patients (95% CI 7.5% to 18.9%), while repeat ablation was reported in 8% (95% CI 4.5% to 11.4%). For RFA of SVT, 39 primary studies with 49 treatment arms in 7,693 patients with accessory pathways and atrioventricular nodal reentrant tachycardia were identified. Single-procedure success for SVT was 93.2% (95% CI 90.8% to 95.5%). Multiple-procedure success was 94.6% (95% CI 92.4% to 96.9). Postablation arrhythmia was noted in 5.6% patients (95% CI 4.1% to 7.2%). Repeat ablation occurred in 6.5% (95% CI 4.7% to 8.3%). For AFL studies, all-cause mortality was 0.6%, and adverse events were reported in 0.5% of patients. For SVT studies, all-cause mortality was 0.1%, and adverse events were reported in 2.9% of patients. In conclusion, studies of RFA for the treatment of patients with AFL and SVT report high efficacy rates and low rates of complications.

Typical atrial flutter can effectively be treated using single one-minute cryoapplications: results from a repeat electrophysiological study

Purpose

Catheter-based cryoablation (cryo) has proven to be as effective as radiofrequency energy (RF) ablation for the treatment of arrhythmias. Nevertheless, the duration of cryoapplications has been reported as being significantly longer than RF applications.

Methods

Thirty-seven consecutive patients (28 men; mean age 59 ± 14 years) with typical atrial flutter (AFL) underwent cryo of the cavotricuspid isthmus (CTI). Applications of 1 min were delivered with a 10-French, 10-mm tipped catheter (CryoCor™). If bidirectional CTI block was not obtained after 12 1-min applications, applications of 3 min were selectively delivered to areas of conduction breakthrough. The endpoint of the procedure was creation of bidirectional CTI block and non-inducibility of AFL.

Results

A median of 7 (range 3 to 12) 1-min applications were given along the CTI with a mean temperature of −88.6 ± 2.3°C. Mean fluoroscopy and procedure time were 27 ± 14 min and 110 ± 28 min respectively. Five patients required additional 3-min applications; in one patient an overextended ablation catheter prevented the completion of the index-procedure. The acute success rate of the index-procedure was 97%. In 12/24 patients, two with AFL recurrence, resumption of CTI conduction was found 4 months post-ablation. In all patients bidirectional CTI block was re-obtained after a median of one 1-min application. No additional AFL recurrences occurred, after a mean follow-up of 37 ± 3 (range 30 to 44) months.

Conclusions

Cryo of AFL can successfully be performed using the same application duration as used for RF ablation. Both acute and long-term results are comparable to RF ablation. AFL recurrences occurred in only a minority of patients with resumption of CTI conduction.

Anatomical characteristics of the cavotricuspid isthmus in patients with and without typical atrial flutter: Analysis with two- and three-dimensional intracardiac echocardiography

INTRODUCTION

The cavotricuspid isthmus (CTI) is crucial in the ablation of typical atrial flutter (AFL), and consequently the CTI anatomy and/or its relation to resistant ablation cases have been widely described in human angiographic studies. Intracardiac echocardiography (ICE) has been shown to be a useful tool for determining detailed anatomical information. Thus, this technology may also allow the visualization of the anatomical characteristics of the CTI, providing an opportunity to further understand the anatomy.

AIM

We conducted a study to compare the anatomy of the CTI between the patients with and without AFL and to characterize the anatomy of the CTI in the patients with AFL resistant to ablation.

MATERIALS AND METHODS

Twelve patients with typical AFL and 20 without AFL were enrolled in the study. Two-dimensional (2D) intracardiac echocardiography (ICE) was performed. The recordings were obtained with a 9F, 9-MHz ICE catheter from the right ventricular outflow tract to the inferior vena cava by pulling the catheter back 0.3 mm at a time under guidance with echocardiographic imaging in a respiration-gated manner. Three-dimensional (3D) reconstruction of the images of the CTI were made with a 3D reconstruction system. After the acquisition of the ICE, the CTI ablation was performed in the patients with AFL.

RESULTS

The 2D and 3D images provided clear visualization of the tricuspid valve, coronary sinus ostium, fossa ovalis and Eustachian valve/ridge (EVR). The CTI was significantly longer in the patients with AFL than in those without AFL (median length 24.6 mm (range 17.0-39.1 mm) versus median length 20.6 mm (range 12.5-28.0 mm), respectively, P < 0.05). However, a deep recess due to a prominent EVR was observed in 9 of 12 (75%) patients with AFL and in 12 of 20 (60%) patients without AFL (N.S.). A deep recess and the relatively long CTI were related to aging in all the study patients, and that relationship was similar in a limited number of patients without AFL. In five patients with AFL resistant to ablation, a deep recess and prominent EVR were observed.

CONCLUSIONS

The 2D and 3D ICE were useful for visualizing the complex anatomy of the CTI and identifying the anatomical characteristics of the CTIs refractory to ablation therapy. The anatomical changes observed in the CTI region may simply be the result of aging and may partially be involved in the development of AFL.

Simple and efficient identification of conduction gaps in post-ablation recurring atrial flutters

AIMS

Cavo-tricuspid isthmus (CTI) radiofrequency (RF) ablation is a curative therapy for common atrial flutter (AFl), but is associated with a recurrence rate of 5-26%. Although complete bidirectional conduction block is usually achieved, the recurrence of AF is due to recovered conducting isthmus tissue through which activation wavefronts pass. We evaluated a simple and efficient electrophysiological strategy, which pinpoints the ablation target.

METHODS AND RESULTS

Twenty-five patients (19 men), mean age 61 +/- 6, with recurrent AFl required a repeat ablation, 250 +/- 160 days after a successful RF CTI procedure. Transverse CTI conduction was monitored during AFl or coronary sinus (CS) pacing by a 24-pole mapping catheter positioned in the right atrium (RA), with the distal poles in the CS, proximal poles on the lateral RA, and intermediate poles on the CTI. A slow conduction area traversing the CTI (velocity, 37 +/- 22 vs. 98 +/- 26 cm/s on either side, P < 0.05) and a lower potential amplitude than at both sides (0.2 +/- 0.15 vs. 0.5 +/- 0.5 mV, P < 0.05), defined by a bayonet-shaped depolarization sequence, were considered to represent the incomplete line of block (InLOB). An ablation catheter was progressively dragged up to this InLOB, from the tricuspid annulus to the inferior vena cava, analysing the widely separated double potentials (DPs) until these coalesced. In nine patients (35%), the target conduction gap was a coalesced fractionated atrial potential within the InLOB (duration, 77 +/- 12 ms), and in 16 patients (65%), a narrow DP toward the healthy margins of this InLOB (duration, 28 +/- 15 ms). Adopting this strategy yields 100% successful re-ablation of recurring AFl leading to bidirectional block, with a mean 2.7 +/- 1.4 RF applications.

CONCLUSION

Transverse CTI mapping precisely locates the InLOB and helps find conduction gaps along the CTI in re-ablation procedures for common AFl.

Clinical prediction of cavotricuspid isthmus dependence in patients referred for catheter ablation of "typical" atrial flutter

INTRODUCTION

Typical atrial flutter (AFL) can be cured by catheter ablation of the cavotricuspid isthmus (CTI). The surface electrocardiogram (ECG) is not always diagnostic of isthmus dependence of AFL. The aim of this study was to evaluate clinical parameters for the prediction of isthmus-dependent AFL.

METHODS AND RESULTS

Sixty consecutive adult patients without suspected atriotomy-related AFL, congenital heart disease, or previous AFL ablation, referred for catheter ablation of presumed typical AFL were studied. All patients had distinct flutter waves in the inferior leads, suggestive of CTI-dependent AFL, either on presentation to the electrophysiology (EP) lab or documented on prior ECG. Electrophysiology study was performed in the standard fashion. Patients who presented to the EP laboratory not in AFL underwent arrhythmia induction with a burst pacing protocol. A clinical history of persistent AFL (P = 0.0001) and existence of AFL on presentation to the EP laboratory (P = 0.0001) were strong predictors of CTI dependence. History of atrial fibrillation (P = 0.19), structural heart disease (P = 0.6), hypertension (P = 0.4), and previous cardiac surgery (P = 0.5), as well as the nature of AFL-related symptoms (P = 0.5), were not predictors of CTI-dependent AFL documented during EP study.

CONCLUSION

In patients with ECG suggestive of typical AFL, the presence of persistent rather than paroxysmal AFL and presentation to the EP laboratory in AFL are strong predictors of CTI-dependent AFL. A paroxysmal pattern of AFL predicts noninducibility of CTI-dependent AFL during EP study. CTI ablation may therefore be less effective in these patients.

Pharmacological and ablative hybrid therapy of atrial fibrillation

The pharmacological and ablative hybrid therapy of atrial fibrillation (AF) consists of radiofrequency catheter ablation of antiarrhythmic drug-induced typical atrial flutter (AFl) and continuation of drug therapy. The purpose of this study was to determine the effect of this therapy on AF symptoms and quality of life (QoL). Forty-six patients were monitored after isthmus-ablation of drug-induced typical AFl and continuation of their antiarrhythmic drug treatment over a mean follow-up of 22.4+/-11.6 months. AF characteristics, symptoms and QoL before and after ablation were evaluated by the SF-36 question- naire, the Symptoms Checklist-Frequency and Severity Scale and the analysis of ECG recordings. 63% of patients demonstrated recurrences of AF. However, the frequency and duration of symptomatic episodes significantly decreased in 82.6 and 76% of patients. All categories of the SF-36 improved significantly and the AF symptomatology showed a relevant attenuation in 65.8% of the study population.

CONCLUSION

The pharmacological and ablative hybrid therapy significantly reduced the mean number and the duration of symptomatic AF episodes as well as AF-correlated symptoms and was associated with significant QoL improvement.

The Inferior Right Atrial Isthmus: Further Architectural Insights for Current and Coming Ablation Technologies

BACKGROUND

Although linear ablation of the right atrial isthmus in patients with isthmus-dependent atrial flutter can be highly successful, recurrences and complications occur in some patients. Our study provides further morphological details for a better understanding of the structure of the isthmus.

METHODS AND RESULTS

We examined the isthmic area in 30 heart specimens by dissection, histology, and scanning electron microscopy. This area was bordered anteriorly by the hinge of the tricuspid valve and posteriorly by the orifice of the inferior caval vein. With the heart in attitudinal orientation, we identified and measured the lengths of three levels of isthmus: paraseptal (24 +/- 4 mm), central (19 +/- 4 mm), and inferolateral (30 +/- 3 mm). Comparing the three levels, the central isthmus had the thinnest muscular wall and the paraseptal isthmus the thickest wall. At all three levels, the anterior part was consistently muscular whereas the posterior part was composed of mainly fibro-fatty tissue in 63% of hearts. The right coronary artery was less than 4 mm from the endocardial surface of the inferolateral isthmus in 47% of hearts. Inferior extensions of the atrioventricular node were present in the paraseptal isthmus in 10% of hearts, at 1-3 mm from the endocardial surface.

CONCLUSIONS

The thinner wall and shorter length of the central isthmus together with its distance from the right coronary artery, and nonassociation with the atrioventricular node or its arterial supply, should make it the preferred site for linear radiofrequency ablation.

Cryothermal Ablation Treatment of Atrial Flutter—Experience with a New 9 French 8 mm Tip Catheter

BACKGROUND

Cardiac cryoablation has been used to successfully treat a variety of arrhythmias.

OBJECTIVE

This study documents our experience with a new 9 French (FR) 8 mm cryocatheter for ablation treatment of symptomatic atrial flutter.

METHODS

A total of 77 consecutive patients with symptomatic atrial flutter were treated. Electrophysiological studies (EPS) were performed with diagnostic catheters and ablation was performed with a 9FR, 8 mm tip, quadripolar cryocatheter (Freezor MAX catheter, CryoCath Technologies Inc., Kirkland, Canada). Cryoablation at -75 degrees C for 8 minutes was performed, beginning at the inferior rim of the coronary sinus (CS) os and creating a posterior line to the Eustachian ridge. Safety, bidirectional isthmus block at intervention, and recurrence at 3 months post procedure were assessed.

RESULTS

There were no adverse events reported. All patients remained free of discomfort on cryoenergy delivery. The acute success rate at intervention was 96% for all patients and 100% for those with common atrial flutter. Follow-up data from 47 patients showed 33 (70%) patients without conduction recurrence on repeat EPS at 3 months. Although, 1 (2%) patient had both symptom and conduction recurrence. Data available from 53 acutely successful patients at 6 month clinical follow-up showed that 48 (91%) patients were asymptomatic and 5 (9%) patients had recurrence documented by ECG and/or patient diary records.

CONCLUSIONS

Our experience with a new 9FR, 8 mm tip, quadripolar cryocatheter yielded a high success rate at intervention and an excellent safety profile. Although repeat EPS at 3 months post ablation identified conduction recurrence in 30% of patients, at 6 month clinical follow-up only 9% of patients had recurrence. Further monitoring is necessary to assess whether the relatively low recurrence rate observed at 6 month clinical follow-up is maintained over the long term.

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.

Single cryothermia applications of less than five minutes produce permanent cavotricuspid isthmus block in humans

OBJECTIVES

The aim of this study was to compare single-3-minute (single-3) with double-3-minute (double-3) cryothermia applications for treatment of atrial flutter (AFL).

BACKGROUND

Previous animal studies have indicated the need for a double 5-minute cryothermal application to create large and permanent lesions.

METHODS

Forty patients (56 +/- 13 years old) with typical AFL (cycle length 229 +/- 35 ms) were randomized to single-3 (n = 20) or double-3 (n = 20) cryothermia applications at each site along the cavotricuspid isthmus (CTI). Cryoablation was performed with the CryoCor cryoablation system. A successful procedure was defined as noninducibility of AFL with the concomitant presence of bidirectional CTI conduction block under isoproterenol infusion.

RESULTS

All but 1 patient (95%) of the single-3 group and all patients (100%) of the double-3 group were successfully ablated. The number of sites needed to create isthmus conduction block was 9 +/- 4 (single-3) and 8 +/- 2 (double-3) (NS). Fluoroscopy time did not differ between the two groups (single-3: 31 +/- 14; double-3: 36 +/- 17 min, NS). The procedure time of the single-3 group was significantly shorter compared to the procedure time of the double-3 group (mean procedure duration 132 +/- 64 vs 159 +/- 50 min, P < .04). After a mean follow-up of 11.7 +/- 4.7 months, two recurrences of AFL occurred in the double-3 group.

CONCLUSIONS

Single cryothermia applications of 3 minutes produce permanent CTI conduction block in patients with typical AFL and significantly reduce procedure duration.

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.

Catheter-based cryoablation permanently cures patients with common atrial flutter

BACKGROUND

Cryoablation (cryo) has a high success rate in the short-term treatment of atrial flutter (AFL), but evidence of long-term efficacy is lacking. The present study reports the long-term effect of cryo of the cavotricuspid isthmus (CTI) in patients with common AFL.

METHODS AND RESULTS

Thirty-five consecutive patients (28 men; mean age, 53 years) underwent cryo of the CTI. In 34 patients, the AFL had a counterclockwise rotation (cycle length, 242+/-43 ms). Eleven patients had structural heart disease. Cryo was performed with a 10F catheter with a 6-mm-tip electrode (CryoCor). Applications (3 to 5 minutes each) were delivered by use of a point-by-point technique to create the ablation line. The acute end point of the procedure was creation of bidirectional isthmus conduction block and noninducibility of AFL. A median of 14 applications (range, 4 to 30) at 10 sites (range, 4 to 19) was given along the CTI with a mean temperature of -80.0+/-5.0 degrees C. Mean fluoroscopy and procedure times were 40+/-26 minutes and 3.2+/-1.3 hours, respectively. Of the 35 patients, 34 were acutely successfully ablated (97%). After a mean follow-up of 17.6+/-6.2 months (range, 9.6 to 26.1 months), 31 patients (89%) did not have recurrence of AFL. Three of the 4 patients with recurrence had a second successful procedure. One patient had transient ST elevation in the inferior leads during cryoapplication.

CONCLUSIONS

Cryo produces permanent bidirectional isthmus conduction block of the CTI. Short- and long-term success rates are comparable to those for radiofrequency ablation.

Delineation of Intra-Atrial Reentrant Tachycardia Circuits After Mustard Operation for Transposition of the Great Arteries Using Biatrial Electroanatomic Mapping and Entrainment Mapping

INTRODUCTION

Intra-atrial reentrant tachycardia (IART) circuits after Mustard operation remain incompletely understood due to the complex atrial anatomy after extensive surgical procedures. The aim of this study was to delineate IART circuits and their relations to the individual anatomic boundaries in Mustard patients.

METHODS AND RESULTS

Twelve patients (10 men and 2 women; age 29 +/- 4.6 years) with atrial tachyarrhythmias after Mustard operation were included in this study. During 14 IARTs and 2 focal atrial tachycardias, electroanatomic mapping and entrainment mapping were performed in both the systemic venous atrium and the pulmonary venous atrium. The latter was accessed via a retrograde transaortic approach. Thirteen IARTs used a single-loop reentrant circuit, and 1 IART used a dual-loop reentrant circuit. Ten (77%) of 13 single-loop reentrant circuits used the tricuspid annulus (TA) as their central barrier. The remaining 3 IARTs rotated around the inferior vena cava (IVC) (n = 2) or ostium of the right upper pulmonary vein (n = 1). In 6 (60%) of the 10 peritricuspid IARTs, both pulmonary venous atrium and systemic venous atrium components of the mid-portion of the TA-IVC isthmus were demonstrated to be part of the reentry. Overall, 12 (86%) of 14 IARTs in 10 patients were successfully ablated by bridging two barriers that constrained the reentrant circuit. Eight (80%) of 10 peritricuspid circuits were abolished by linear ablation connecting the TA to the IVC (n = 4), incisional scar (n = 2), patch (n = 1), and atriotomy (n = 1).

CONCLUSIONS

In Mustard patients, the TA serves as the most frequent central barrier of IART. Biatrial electroanatomic mapping combined with entrainment mapping facilitates delineation of IART circuits in relation to their anatomic barriers and enables the design of individual ablation strategies to achieve high success.

Occurrence of atrial fibrillation after flutter ablation: the significance of intra-atrial conduction and atrial vulnerability

Atrial vulnerability and intra-atrial conduction delay are important substrates for paroxysmal atrial fibrillation (AFib); however, their significance is unknown in patients undergoing atrial flutter ablation. Antegrade (high right atrium to coronary sinus: HRA-CS) and retrograde (CS-HRA) intra-atrial conduction times and AFib inducibility were assessed in 61 patients undergoing ablation for type I atrial flutter. Twenty-three patients had structural heart disease and 18 AFib before the procedure. After 16 +/- 12 months of follow-up 17 patients experienced AFib, 5 of which progressed into chronic AFib. During the study, AFib was easily inducible in 14 patients, 7 of which developed AFib (P =.03). Patients with post- ablation AFib were older (59 +/- 11 vs. 44 +/- 15 years, P =.001), had longer intra-atrial conduction times before (98 +/- 17 ms vs. 68 +/- 20 ms, P <.001) and after ablation (91 +/- 19 ms vs. 73 +/- 21 ms, P =.01) than those without AFib. Discriminant analysis revealed that only age, previous AFib and inta-atrial conduction delay (>90 ms) were independent predictors of postablation AFib. Patients without a history of AFib and with normal intra-atrial conduction had a 3% risk of AFib, while patients with both factors had a 90% risk of AFib after ablation. Intra-atrial conduction delay is an important electrophysiological factor predicting atrial fibrillation after successful flutter ablation.

Identification of extremely slow conduction in the cavotricuspid isthmus during common atrial flutter ablation

INTRODUCTION

Complete isthmus block has been used as an endpoint for radiofrequency ablation for common atrial flutter (AF). We sought to systematically evaluate extremely slow conduction (ESC), which is easily misinterpreted as complete block.

METHODS AND RESULTS

We studied 107 consecutive patients (92 men, 15 women, 58 +/- 11 years) who had undergone a successful AF ablation procedure. A 24-pole catheter was positioned along the tricuspid annulus spanning the isthmus. Complete isthmus block was defined as the presence of a complete corridor of double potentials along the ablation line. Activation delay time (AT), activation difference (deltaA) between two adjacent dipoles, maximum activation difference (deltaA(max)), change in polarity (CP) and change in amplitude (CA) of the bipolar atrial electrogram were recorded and P-wave morphology in the surface electrocardiogram was analyzed. ESC was observed in 16 patients. Between ESC and complete block, differences were found on the two lateral dipoles adjacent to the ablation line (AT: 148 +/- 17 vs. 183 +/- 27 ms and 155 +/- 18 vs. 170 +/- 28 ms, P < 0.01; deltaA: -91 +/- 22 vs. -126 +/- 28 ms and -7 +/- 13 vs. 13 +/- 6 ms, P < 0.01). Statistically significant differences in CP were detected on the relevant dipoles (7/16 vs. 14/16 and 6/16 vs.13/16, P < 0.05). No significant difference was found either in CA or in terminal P wave positivity. Mean deltaA(max) were 13.8 +/- 5.0 and 27.8 +/- 9.5 ms (P < 0.001) respectively in ESC and complete block. Two types of ESC, regular and irregular, were demonstrated during the ablation procedure.

CONCLUSIONS

(1) ESC was observed in 15% of the patients during the AF ablation procedure. (2) The parameters of AT, deltaA, and CP may help to differentiate ESC from complete block. DeltaA(max) might be the most powerful indicator. (3) To verify complete block, it is essential to position the mapping catheter across the CTI in order to demonstrate the activation sequence up to the ablation line.

Symptomatic improvement after radiofrequency catheter ablation for typical atrial flutter

OBJECTIVE

To assess the changes in quality of life, arrhythmia symptoms, and hospital resource utilisation following catheter ablation of typical atrial flutter.

DESIGN

Patient questionnaire to compare the time interval following ablation with a similar time interval before ablation.

SETTING

Tertiary referral centre.

PATIENTS

63 consecutive patients were studied. Four patients subsequently underwent an ablate and pace procedure, two died of co-morbid illnesses, and two were lost to follow up. The remaining 55 patients form the basis of the report.

RESULTS

Patients were followed for a mean (SD) of 12 (9.5) months. Atrial flutter ablation resulted in an improvement in quality of life (3.8 v 2.5, p < 0.001) and reductions in symptom frequency score (2.0 v 3.5, p < 0.001) and symptom severity score (2.0 v 3.8, p < 0.001) compared with preablation values. There was a reduction in the number of patients visiting accident and emergency departments (11% v 53%, p < 0.001), requiring cardioversion (7% v 51%, p < 0.001), or being admitted to hospital for a rhythm problem (11% v 56%, p < 0.001). Subgroup analysis confirmed that patients with atrial flutter and concomitant atrial fibrillation before ablation and those with atrial flutter alone both derived significant benefit from atrial flutter ablation. Patients with concomitant atrial fibrillation had an improvement in quality of life (3.5 v 2.5, p < 0.001) and reductions in symptom frequency score (2.3 v 3.5, p < 0.001) and symptom severity score (2.2 v 3.7, p < 0.001) compared with preablation values.

CONCLUSIONS

Ablation of atrial flutter is recommended both in patients with atrial flutter alone and in those with concomitant atrial fibrillation.

Symptomatic improvement after radiofrequency catheter ablation for typical atrial flutter

OBJECTIVE

To assess the changes in quality of life, arrhythmia symptoms, and hospital resource utilisation following catheter ablation of typical atrial flutter.

DESIGN

Patient questionnaire to compare the time interval following ablation with a similar time interval before ablation.

SETTING

Tertiary referral centre.

PATIENTS

63 consecutive patients were studied. Four patients subsequently underwent an ablate and pace procedure, two died of co-morbid illnesses, and two were lost to follow up. The remaining 55 patients form the basis of the report.

RESULTS

Patients were followed for a mean (SD) of 12 (9.5) months. Atrial flutter ablation resulted in an improvement in quality of life (3.8 v 2.5, p < 0.001) and reductions in symptom frequency score (2.0v 3.5, p < 0.001) and symptom severity score (2.0 v 3.8, p < 0.001) compared with preablation values. There was a reduction in the number of patients visiting accident and emergency departments (11%v 53%, p < 0.001), requiring cardioversion (7% v 51%, p < 0.001), or being admitted to hospital for a rhythm problem (11%v 56%, p < 0.001). Subgroup analysis confirmed that patients with atrial flutter and concomitant atrial fibrillation before ablation and those with atrial flutter alone both derived significant benefit from atrial flutter ablation. Patients with concomitant atrial fibrillation had an improvement in quality of life (3.5 v 2.5, p < 0.001) and reductions in symptom frequency score (2.3 v 3.5, p < 0.001) and symptom severity score (2.2v 3.7, p < 0.001) compared with preablation values.

CONCLUSIONS

Ablation of atrial flutter is recommended both in patients with atrial flutter alone and in those with concomitant atrial fibrillation.

Effects of cavotricuspid isthmus catheter ablation on paroxysmal atrial fibrillation

It has been demonstrated that successful cavotricuspid isthmus ablation of typical atrial flutter combined with atrial fibrillation (AF) sometimes influences the preablation history of paroxysmal AF. However, the effectiveness of only isthmus ablation on AF itself is unclear. Endocardial catheter mapping during induced AF was performed around the tricuspid annulus using duodecapolar clectrode catheters in 39 patients with drug-refractory paroxysmal AF. Isthmus ablation was performed in 16 patients (41%) in whom catheter mapping during AF showed an organized activation pattern around the tricuspid annulus. During a mean follow-up of 12.3 months, isthmus ablation was successful in preventing AF in 12 (75%) patients, 8 without medication and 4 with a previously ineffective drug. This success group had a significantly higher F wave amplitude in lead V1 (0.29+/-0.10 vs 0. 15+/-0.04 mV, p < 0.01), a higher left ventricular ejection fraction (74+/-9 vs 58+/-2%, p < 0.05), and a smaller left atrial dimension (35+/-6 vs 43+/-4 mm, p < 0.05) than the failure group. Isthmus ablation may be effective in preventing paroxysmal AF with an organized activation pattern around the tricuspid annulus. F wave amplitude, left ventricular ejection fraction, and left atrial dimension were significant predictors of success.

Electromagnetic versus fluoroscopic mapping of the inferior isthmus for ablation of typical atrial flutter: A prospective randomized study

BACKGROUND

Radiofrequency catheter ablation within the tricuspid annulus-inferior caval vein isthmus can cure typical atrial flutter. The target for ablation, nonetheless, is relatively wide, and standard ablation procedures may require significant exposure to radiation.

METHODS AND RESULTS

A total of 50 patients (mean age, 58+/-11 years) with typical atrial flutter were prospectively randomized to receive isthmus ablation using conventional fluoroscopy for catheter navigation (group I, n=24) or electromagnetic mapping (group II, n=26). Complete bidirectional isthmus block was verified with double potential mapping. If complete isthmus block could not be achieved after 20 radiofrequency pulses or 25 minutes of fluoroscopy, the patients were switched to the other group. Eight patients from group I (33%) but only 1 patient from group II (4%) were switched. Overall, complete isthmus block was achieved in 47 of 50 patients (94%). The overall fluoroscopy time, including the placement of the diagnostic catheters, was 22.0+/-6.3 minutes in group I and 3.9+/-1.5 minutes in group II (P:<0.0001). The fluoroscopy time needed for isthmus mapping was 17.7+/-6.5 minutes in group I and 0.2+/-0.3 minutes in group II (P:<0.0001).

CONCLUSIONS

Electromagnetic mapping during the induction of linear lesions for the ablation of atrial flutter permitted a highly significant reduction in exposure to fluoroscopy while maintaining high efficacy, and it allowed the time required for fluoroscopy to be reduced to levels anticipated for diagnostic electrophysiological studies.

Management of atrial flutter

Typical atrial flutter is a macroreentrant arrhythmia of the right atrium. The isthmus area between the tricuspid annulus, the inferior vena cava, and the ostium of the coronary sinus is a critical zone of the reentry circle. Atrial flutter has been treated with class I and III antiarrhytmic drugs to maintain sinus rhythm, with moderate success. Catheter ablation has been highly successful in treating atrial flutter. A contiguous line of bidirectional electrical block is created in the isthmus area between the tricuspid annulus and the inferior vena cava by application of radiofrequency energy. In patients with both atrial flutter and atrial fibrillation, ablation of the atrial flutter circuit may make the atrial fibrillation more easy to control. Quality of life assessments show improvement after ablation of atrial flutter. With a probability of success of 90%, a recurrence rate of 5% to 15%, and few complications, catheter ablation emerges as the best treatment of recurrent, symptomatic flutter.

Typical atrial flutter ablation: conduction across the posterior region of the inferior vena cava orifice may mimic unidirectional isthmus block

INTRODUCTION

The aim of this study was to map the low right atrium before and after radiofrequency ablation of the inferior vena cava-tricuspid annulus (IVC-TA) isthmus in patients with typical atrial flutter (AFI) to better understand the electrophysiologic meaning of incomplete or unidirectional block following the ablation procedure and its relationship with AFI recurrence.

METHODS AND RESULTS

We performed atrial mapping in 12 patients using a "basket" catheter in the IVC orifice, Halo catheter in the right atrium, and multipolar catheters in the coronary sinus (CS) and His region. In patients in sinus rhythm, atrial activation was analyzed during pacing from the CS and low lateral right atrium (LLRA) before and after ablation. Atrial activation propagated across the isthmus and posterior region of the IVC orifice simultaneously before ablation. Mapping during AF1 in four patients showed that the crista terminalis was a site of functional block. After ablation, evaluation of Halo catheter recordings in three patients showed apparent unidirectional counterclockwise block, whereas analysis of basket catheter recordings demonstrated complete bidirectional block. The apparent conduction over the isthmus during pacing from proximal CS was due to conduction along the posterior part of the IVC orifice, which activated the LLRA despite complete isthmus block.

CONCLUSION

Our results demonstrate that limited endocardial mapping may yield a pattern compatible with unidirectional block in the IVC-TA isthmus, although bidirectional block is present at this anatomic level.

Prospective randomized comparison of irrigated-tip versus conventional-tip catheters for ablation of common flutter

BACKGROUND

Radiofrequency (RF) ablation of common flutter requires the creation of a complete ablation line to produce bidirectional conduction block in the cavotricuspid isthmus. An irrigated-tip ablation catheter has been shown to be effective in patients in whom conventional ablation has failed. This randomized study compares the efficacy and safety of this catheter with those of a conventional catheter for de novo flutter ablation.

METHODS AND RESULTS

Cavotricuspid ablation was performed with a conventional (n=26) or an irrigated-tip catheter (n=24). RF was applied for 60 minutes with a temperature-controlled mode: 65 degrees C to 70 degrees C up to 70 W with a conventional catheter or 50 degrees C up to 50 W (with a 17-mL/min saline flow rate) with the irrigated-tip catheter. The end point was the achievement of bidirectional isthmus block, and a crossover was performed after 21 unsuccessful applications. Procedural ablation parameters as well as number of applications, x-ray exposure, procedure duration, impedance rise, and clot formation were compared for each group. A coronary angiogram was performed before and after each ablation for the first 30 patients. Complete bidirectional isthmus block was achieved for all patients. Four patients crossed over from conventional to irrigated-tip catheters. The number of applications, procedure duration, and x-ray exposure were significantly higher with the conventional than with the irrigated-tip catheter: 13+/-10 versus 5+/-3 pulses, 53+/-41 versus 27+/-16 minutes, and 18+/-14 versus 9+/-6 minutes, respectively. No significant side effects occurred, and the coronary angiograms of the first 30 patients after ablation were unchanged.

CONCLUSIONS

Irrigated-tip catheters were found to be more effective than and as safe as conventional catheters for flutter ablation, facilitating the rapid achievement of bidirectional isthmus block.

Catheter ablation approach on the right side only for paroxysmal atrial fibrillation therapy: long-term results

We report the long-term follow-up of a right side only catheter ablation approach for paroxysmal AF. Eighteen patients with AF refractory to drugs entered the study. Ablation was attempted in the right atrium only by creating linear lesions based on a specific design including from two to four linear lesions. Induction of AF was attempted before ablation and after placement of the lesions. A septal lesion was performed in nine patients. In ten patients atrial defibrillation thresholds (ADFTs) before ablation and following creation of the linear lesions were compared. After a mean follow-up of 22 +/- 11 months, seven patients had recurrence of AF, and another nine patients experienced atrial flutter or atrial tachycardia. Five patients remained in sinus rhythm without medications and four required the use of drugs. Three patients had sporadic AF and six were in chronic AF. The recurrence rate was similar in patients with and without the septal lesion. However, a cure with right side ablation appeared to be predicted by the presence of disorganized and earlier activity in the high right atrium and crista terminalis. Linear lesions in the right atrium were associated with a lower ADFT (pre 2.6 +/- 04 J vs post 1.7 +/- 0.6 J). In conclusion, in a small number of patients, control of AF can be obtained with a right side only approach. Certain activation patterns may identify patients suitable to this approach. No specific lesion pattern appeared more effective. Right atrial linear lesions resulted in lower ADFT.

Comparison of results of an 8-mm split-tip versus a 4-mm tip ablation catheter to perform radiofrequency ablation of type I atrial flutter

Thirty consecutive patients with type I atrial flutter were randomized to undergo radiofrequency ablation using an 8-mm split-tip versus a 4-mm tip catheter. Procedural success was high in both groups (100% vs 93%). However, requirement of a fewer number of radiofrequency pulses and fluoroscopy time suggests superiority of the 8-mm split-tip over the 4-mm tip ablation catheter.

Predictors of success in radiofrequency catheter ablation of atrial flutter

Radiofrequency catheter ablation of typical atrial flutter at the isthmus between the tricuspid annulus and the inferior vena cava is established. However in selected patients, the creation of a continuous linear lesion at the targeted isthmus requires a lengthened procedure or is not feasible at all and atrial flutter recurrences are common. In a retrospective analysis, we found that an intraoperatively determined distance between the tricuspid annulus and the inferior vena cava of <.2.5 cm is an independent predictor of a lengthened or failed ablation procedure. Additional equipment, e.g., long introducer sheaths, adapted ablation catheter design, or irrigated tip ablation, as well as alternative ablation approaches, e.g., linear lesions between the tricuspid annulus and Eustachian ridge, have been invented in order to increase the acute success rate or decrease fluoroscopy and procedure time. In a prospective study on the effects of various conduction properties at the isthmus between tricuspid annulus and inferior vena cava following radiofrequency ablation of atrial flutter, we showed previously that others than a complete bidirectional conduction block predicts a high recurrence rate of atrial flutter. For determination of transisthmal conduction properties following ablation, established mapping approaches are documentation of double potentials at the ablation line and right atrial activation sequence following posteroseptal and low lateral right atrial pacing. Novel threedimensional mapping systems, i.e., Carto(R) and EnSite(R), may further enhance the accuracy of conventional mapping techniques.

Cavotricuspid isthmus mapping to assess bidirectional block during common atrial flutter radiofrequency ablation

BACKGROUND

We sought to compare published methods to an alternative approach ascertaining cavotricuspid isthmus (CTI) block during atrial flutter ablation.

METHODS AND RESULTS

In 39 consecutive patients who underwent an atrial flutter ablation procedure, a 24-pole mapping catheter was positioned so that 2 adjacent dipoles were bracketing the targeted CTI line of block (LOB), with proximal dipoles lateral to the LOB and distal dipoles in the coronary sinus. Two pacing sites were lateral (positions A and B) and 2 were septal (positions C and D) to the LOB, with locations A and D closest to the LOB. A resulting CTI block was accepted when 3 criteria were fulfilled: (1) complete reversal of the right atrial depolarization on the 24-pole catheter when pacing in the coronary sinus, (2) conduction delays from A to D greater than from B to D, and (3) conduction delays from D to A greater than from C to A. A successful CTI block was obtained in all patients. Before CTI block was obtained, a progressive CTI conduction delay was observed in 11 patients (28.2%). During the procedure, the 3 criteria defined above were either all present or all absent.

CONCLUSIONS

This study establishes that reversal of the atrial depolarization sequence up to the LOB is a definitive and mandatory criteria of successful atrial flutter ablation.

Impact of the ECG for detection of intraatrial conduction block after atrial flutter ablation

Induction of complete bidirectional conduction block via the posterior isthmus of the right atrium is introduced as a standard endpoint for catheter ablation of atrial flutter. The present study sought to investigate the impact of changes in P wave duration and morphology detected by the surface ECG during coronary sinus and posterolateral right atrial stimulation as a marker for conduction block. Morphology and duration changes of the paced P wave before and after radiofrequency catheter (RFC) ablation were estimated in 22 patients referred for ablation of atrial flutter. We looked for a morphology change of the terminal portion in the 12-lead ECG and an increment of P wave duration. In 16 of 22 patients in whom atrial flutter ablation resulted in a complete bidirectional block, the conduction block was unidirectional in 4 patients and conduction times remained unchanged in 2 patients. After induction of complete bidirectional block a change of the terminal portion of the P wave towards a more positive morphology in one or more inferior leads was detected in 14 (88%) of 16 patients during coronary sinus stimulation and in 15 (94%) of 16 patients during posterolateral right atrial stimulation. These changes were predominantly observed in the inferior leads. Positive morphology changes of the terminal P wave portion in the inferior leads indicating conduction block with a sensitivity of 86% and a specificity of 100% were observed. An increment of 10 ms or more in P wave duration indicates conduction block with a specificity of 100% and a sensitivity of 67%. There was a significantly larger increment of P wave duration during coronary sinus (CS) stimulation compared to posterolateral right atrial stimulation (38 +/- 21 vs 16 +/- 21 ms). The analysis of P wave duration and morphology in the inferior leads of the surface ECG is a reliable tool to assess the intraatrial conduction after atrial flutter ablation. Different conduction during coronary sinus and posterolateral right atrial pacing may cause a different P wave duration after ablation.

Transverse conduction capabilities of the crista terminalis in patients with atrial flutter and atrial fibrillation

OBJECTIVES

In this study, the transverse conduction capabilities of the crista terminalis (CT) were determined during pacing in sinus rhythm in patients with atrial flutter and atrial fibrillation.

BACKGROUND

It has been demonstrated that the CT is a barrier to transverse conduction during typical atrial flutter. Mapping studies in animal models provide evidence that this is functional. The influence of transverse conduction capabilities of the CT on the development of atrial flutter remains unclear.

METHODS

The CT was identified by intracardiac echocardiography. The atrial activation at the CT was determined during programmed stimulation with one extrastimulus at five pacing sites anteriorly to the CT in 10 patients with atrial flutter and 10 patients with atrial fibrillation before and after intravenous administration of 2 mg/kg disopyramide. Subsequently, atrial arrhythmias were reinduced.

RESULTS

At baseline, pacing with longer coupling intervals resulted in a transverse pulse propagation across the CT. During shorter coupling intervals, split electrograms and a marked alteration of the activation sequence of its second component were found, indicating a functional conduction block. In patients with atrial flutter, the longest coupling interval that resulted in a complete transverse conduction block at the CT was significantly longer than that in patients with atrial fibrillation (285 +/- 49 ms vs. 221 +/- 28 ms; p < 0.05). After disopyramide administration, a transverse conduction block occurred at longer coupling intervals as compared with baseline (287 +/- 68 ms vs. 250 +/- 52 ms; p < 0.05). Subsequently, a sustained atrial arrhythmia was inducible in 15 of 20 patients. This was atrial flutter in three patients with previously documented atrial fibrillation and in eight patients with history of atrial flutter. Mapping revealed a conduction block at the CT in all of these patients.

CONCLUSIONS

It was found that the CT provides transverse conduction capabilities and that the conduction block during atrial flutter is functional. Limited transverse conduction capabilities of the CT seem to contribute to the development of atrial flutter.