Developments, complications and limitations of catheter-mediated electrical ablation of posterior accessory atrioventricular pathways

Novel pacing maneuvers for mapping the upstream insertion of unidirectional accessory pathways

BACKGROUND

Anatomic characterization of unidirectional accessory pathways (APs) is inherently limited to the localization of the downstream insertion site. The inability to define the full anatomic course of unidirectional pathways can limit the safety and effectiveness of ablation in the setting of complex pathways, slanted pathways, unstable catheter positioning at downstream insertions, or insertions near the conduction system.

OBJECTIVE

We aimed to develop novel pacing maneuvers to localize upstream insertions of unidirectional APs.

METHODS

Two methods were evaluated: localizing the shortest transit time from roving pacing sites to a fixed reference in the opposite chamber (upstream transit mapping); and identifying the site at which the latest atrial or ventricular extrastimulus reset atrioventricular reciprocating tachycardia (late reset mapping). Unidirectional APs were included to test utility and feasibility of the techniques, and bidirectional APs were included to test anatomic accuracy.

RESULTS

A total of 13 patients were included, 8 unidirectional APs and 5 bidirectional APs. Blind side mapping was successfully performed in all cases and showed excellent spatial correlation to conventional mapping methods (mean, 4.2 mm; SD, 1.3 mm) as well as to the site of successful ablation (mean, 2.5 mm; SD, 2.9 mm). The upstream transit mapping method was critical for successful ablation after conventional techniques proved inadequate in 2 cases.

CONCLUSION

Two novel methods, upstream transit mapping and late reset mapping, were used to localize the previously unmappable upstream insertions of unidirectional pathways. These methods expand the diagnostic toolbox to facilitate successful ablation in challenging cases.

Pathophysiological Effects on Coronary Arteries Following Radiofrequency Ablation: A Comprehensive Review

Radiofrequency ablation (RFA) is a safe and effective treatment for patients experiencing ventricular and atrial tachyarrhythmias. While complications after RFA are generally rare, the occurrence of coronary artery (CA) injury, albeit infrequent, can have significant clinical implications. Given the proximity of CAs to common ablation sites, understanding the interplay between RFA and CA perfusion pathophysiology is paramount. Although previous studies have discussed the presentation and outcomes of CA injury post-ablation, a comprehensive review consolidating the mechanisms of CA injury following RFA remains absent in the cardiology literature. In this review, we conducted an extensive literature search spanning the past three decades to explore the link between the biophysics of RFA and CA perfusion pathophysiology, focusing on injury mechanisms. We delve into RFA lesion pathology, elucidate the mechanisms of CA injury resulting from RFA, and examine factors influencing lesion formation, such as convective cooling and the "shadow effect." Furthermore, we outline methods to mitigate CA injury post-RFA and propose novel research avenues to optimize lesion formation and ensure the safety of arrhythmia treatments, particularly in cases where tissue ablation is performed close to CAs.

Mechanisms of action behind the protective effects of proactive esophageal cooling during radiofrequency catheter ablation in the left atrium

Proactive esophageal cooling for the purpose of reducing the likelihood of ablation-related esophageal injury resulting from radiofrequency (RF) cardiac ablation procedures is increasingly being used and has been Food and Drug Administration cleared as a protective strategy during left atrial RF ablation for the treatment of atrial fibrillation. In this review, we examine the evidence supporting the use of proactive esophageal cooling and the potential mechanisms of action that reduce the likelihood of atrioesophageal fistula (AEF) formation. Although the pathophysiology behind AEF formation after thermal injury from RF ablation is not well studied, a robust literature on fistula formation in other conditions (eg, Crohn disease, cancer, and trauma) exists and the relationship to AEF formation is investigated in this review. Likewise, we examine the abundant data in the surgical literature on burn and thermal injury progression as well as the acute and chronic mitigating effects of cooling. We discuss the relationship of these data and maladaptive healing mechanisms to the well-recognized postablation pathophysiological effects after RF ablation. Finally, we review additional important considerations such as patient selection, clinical workflow, and implementation strategies for proactive esophageal cooling.

Coronary Sinus Injuries following Retrograde Cardioplegia

A retrograde coronary sinus cardioplegia catheter was used for administration of retrograde cardioplegic solution in 620 of 942 coronary bypass procedures performed over a 3-year period. Coronary sinus injuries were encountered in 4 patients (0.65%).

Coronary artery pathophysiology after radiofrequency catheter ablation: review and perspectives

BACKGROUND

Radiofrequency ablation (RFA) has proven to be an effective and safe treatment in patients with ventricular and atrial tachyarrhythmias. Among complications arising after RFA, the incidence of coronary artery (CA) injury is exceedingly low. When CA injury does occur, however, it can be clinically devastating. The proximity of CAs to common ablation sites suggests that the relationship between RFA and CA perfusion pathophysiology is important for optimal lesion formation and safe arrhythmia treatments.

OBJECTIVE

Although others have described the presentation and outcomes of patients with CA injury after ablation, a review that consolidates the mechanisms of CA injury after RFA has yet to be presented in the cardiology literature.

METHODS

We conducted an extensive literature search of studies published over the past 30 years that relate the biophysics of RFA with CA perfusion pathophysiology and injury.

RESULTS

We present a review of the dynamic relationship between RFA and CA perfusion. We describe RFA lesion pathology, mechanisms of CA injury from RFA, and factors that influence lesion formation, such as convective cooling and the shadow effect.

CONCLUSION

We summarize methods to mitigate CA injury after RFA and propose new research avenues to optimize lesion formation and safe arrhythmia treatments when tissue is ablated in the vicinity of CAs.

Reversing the direction of paced ventricular and atrial wavefronts reveals an oblique course in accessory AV pathways and improves localization for catheter ablation

BACKGROUND

The purpose of this study was to determine how often accessory atrioventricular (AV) pathways (AP) cross the AV groove obliquely. With an oblique course, the local ventriculoatrial (VA) interval at the site of earliest atrial activation (local-VA) and the local-AV interval at the site of earliest ventricular activation (local-AV) should vary by reversing the direction of the paced ventricular and atrial wavefronts, respectively.

METHODS AND RESULTS

One hundred fourteen patients with a single AP were studied. Two ventricular and two atrial pacing sites on opposite sides of the AP were selected to reverse the direction of the ventricular and atrial wavefronts along the annulus. Reversing the ventricular wavefront increased local-VA by >/=15 ms in 91 of 106 (91%) patients. With the shorter local-VA, the ventricular potential overlapped the atrial potential along a 17.2+/-8.5-mm length of the annulus. No overlap occurred with the opposite wavefront. Reversing the atrial wavefront increased local-AV by >/=15 ms in 32 of 44 (73%) patients. With the shorter local-AV, the atrial potential overlapped the ventricular potential along an 11.9+/-8.9-mm length of the annulus. No overlap occurred with the opposite wavefront. Mapping during longer local-VA or local-AV identified an AP potential in 102 of 114 (89%) patients. Catheter ablation eliminated AP conduction in all 111 patients attempted (median, 1 radiofrequency application in 99 patients with an AP potential versus 4.5 applications without an AP potential).

CONCLUSIONS

Reversing the direction of the paced ventricular or atrial wavefront reveals an oblique course in most APs and facilitates localization of the AP potential for catheter ablation.

Radiofrequency catheter ablation of left-sided accessory pathways in pediatric patients

In many cases, radiofrequency catheter ablation has replaced the long-term use of antiarrhythmic medication for symptomatic tachycardia, and has all but eliminated arrhythmia surgery. The most common substrate for radiofrequency catheter ablation in pediatric patients is atrioventricular (AV) reentry tachycardia due to a concealed or manifest accessory pathway. Accessory pathways are distributed unevenly along the right and left atrioventricular valve annuli, and left-sided accessory pathways are most common. Although some centers advocate an abbreviated diagnostic and mapping approach to both concealed and manifest left-sided accessory pathways, most still use a complete electrophysiological evaluation and complex catheter manipulation for mapping, followed by the application of radiofrequency energy. Left-sided accessory pathways may be approached from the transatrial approach, the retrograde aortic approach, or less commonly from within the coronary sinus. Each approach has proven to be associated with success, but also with a distinct set of risks. Possibly because left-sided accessory pathways are most common, catheter ablation of this substrate has proven highly successful and has the lowest risk of recurrence. However, recent data also suggest that this substrate is associated with greater risk of complications than of right-sided accessory pathways or pathways located in the posteroseptal region. The following report reviews some of the recently described diagnostic and mapping techniques, success rates, risks and follow-up data in pediatric patients undergoing radiofrequency catheter ablation of left-sided accessory pathways.

[Biphasic low-energy internal cardioversion in atrial fibrillation induced during electrophysiologic study]

INTRODUCTION

Atrial fibrillation is observed in 10% of electrophysiological studies. Previous studies have shown the efficacy of biphasic low energy internal cardioversion to restore sinus rhythm. We studied the efficacy and safety of low-energy internal cardioversion and the biphasic curve, in sustained atrial fibrillation (>15 min) during electrophysiologic procedures.

MATERIALS AND METHODS

From January 1997 to August 1998, 320 patients underwent an electrophysiological study. An internal cardioversion was done on those patients who developed sustained atrial fibrillation. We delivered biphasic shocks between electrodes-catheters positioned in the right atrium and the coronary sinus. Increasing energy was applied until restoration of sinus rhythm or a maximum of 10 joules were achieved with no result. A right ventricle electrode was used to synchronize the V wave and for temporary pacing.

RESULTS

Thirty one episodes of sustained atrial fibrillation were observed in 26 patients (1,23 episodes/patient) and a mean of 2,58 internal cardioversions were applied per every patient. Sinus rhythm was restored in twenty three patients. The mean energy delivered was 4.1 joules. The mean time for the recovery was 3,200 ms. Temporary pacing was used in 16% of the patients for up to 1 minute. No AV blocks were observed.

CONCLUSIONS

Internal cardioversion successfully restored sinus rhythm in 88.5% of the patients who presented sustained atrial fibrillation (88.5%). Temporary pacing was necessary for the treatment of postsinus shock pauses.

Persistent T-wave changes after radiofrequency catheter ablation of an accessory connection (Wolff-parkinson-white syndrome) are caused by "cardiac memory"

BACKGROUND

The purpose of this study was to determine the incidence and origin of T-wave changes after ablation of an accessory atrioventricular connection (AC), which could either be a sign of damage to the coronary circulation or a result of persistent abnormal repolarization secondary to previously abnormal ventricular activation ("cardiac memory").

METHODS AND RESULTS

Ninety of 107 consecutive patients (33 women and 57 men, mean age 36 +/- 5 years) undergoing successful catheter ablation of an AC were studied. Patients with bundle branch block or more than 1 AC were excluded. Sixty-four patients had manifest preexcitation (group 1) and 26 had a concealed AC (group 2). Immediately after loss of preexcitation, 38 (59%) patients with a manifest AC showed T-wave abnormalities. In contrast, none of the patients with a concealed AC had T-wave abnormalities after ablation (P <.05). The T-wave changes (1) did not correlate with the number or duration of energy applications or with markers of tissue injury; (2) correlated with the location of the AC and the degree of preexcitation, respectively; and (3) completely resolved over a period of weeks to months. None of the patients had recurrence of preexcitation or tachycardia during a mean follow-up of 16 +/- 7 months.

CONCLUSIONS

T-wave changes after ablation are most likely caused by "cardiac memory" and are not a sign of myocardial or coronary injury.

Successful radiofrequency catheter ablation of congenital junctional ectopic tachycardia with preservation of atrioventricular conduction in a 9-month-old infant

An infant with congenital junctional ectopic tachyardia required frequent hospitalizations due to tachycardia acceleration despite multiple antiarrhythmic medications. At 9 months of age, he underwent successful radiofrequency catheter ablation of the tachycardia with preservation of AV conduction.

Entrapment of an ablation catheter in the cardiac venous system: a case report

Cannulation of the coronary sinus is a common procedure with infrequent complications. We report an unusual case of a steerable "dumb-bell" catheter passed through the ostium of the coronary sinus prior to an intended radiofrequency ablation procedure becoming stuck and requiring general anesthesia for extraction. We caution against the use of such catheters with a "waist" for the cannulation of the coronary sinus.

[High frequency current catheter ablation of accessory conduction pathways]

Radiofrequency catheter ablation has established as the first line therapy for the curative treatment of patients with accessory pathway. Atrioventricular accessory pathways irrespective of the exact localisation can be successfully ablated in more than 90% of all cases. Severe complications associated with the ablation procedure are rare and occur in approximately 2% of patients treated. The recurrence rate after successful ablation is approximately 8 to 10%. Recurrence of accessory pathway conduction occurs almost exclusively within the first 3 months following successful ablation, late recurrences are rare. Patients with variants of accessory pathways such as atriofascicular pathways or retrogradely conducting accessory pathways with decremental conduction properties can also be cured with a high success rate. Because of its well balanced efficacy-risk profile radiofrequency catheter ablation should be recommended as the first line therapy to all symptomatic patients with accessory pathway.

Internal cardioversion of chronic atrial fibrillation in patients

Transvenous internal cardioversion of chronic AF using a right atrium (RA) coronary sinus (CS) vector requires more energy than cardioversion of paroxysmal AF. Chronic AF is not terminated in 25% of patients using biphasic shocks up to 10 J. We therefore evaluated efficacy, safety, and tolerability of internal cardioversion using a "unipolar" configuration (RA to skin patch) and biphasic shocks in patients with long-lasting AF and different heart disease. In each patient, biphasic R wave synchronous shocks were delivered between a large defibrillating surface area electrode in the RA and a skin patch in the left prepectoral position. Defibrillation protocol started with a test shock of 0.4 J. Shocks were repeated and increased until termination of AF or a maximum of 34 J. Sedation was used when the patient described the shock as painful. This study included 11 patients with a mean age of 67 +/- 8 years (range 56-83). AF duration was > or = 1 month in all patients with a mean duration of 11 +/- 11 months (range 2-36). Underlying heart disease was present in all patients and the mean left atrial dimension was 43 +/- 9 mm (range 26-57). AF was terminated in 10 of 11 patients (91%) with a mean delivered energy of the successful shocks of 18.7 +/- 8.7 J (median energy 16.9 J; range 7.3-32.5) and a mean leading edge voltage of 564 +/- 129 V. The mean shock impedance at the defibrillation threshold was 71 +/- 13 omega (range 59-103). A total of 131 shocks were delivered without any complication and proarrhythmia episodes. We conclude that low energy "unipolar" internal cardioversion is a simple, safe, and effective technique for termination of chronic AF in patients with heart disease. The procedure is often tolerated under light sedation.

Insights into the electrophysiology of accessory pathway-mediated arrhythmias provided by the catheter ablation experience: "learning while burning, part III"

The success of catheter ablation has greatly improved the care of patients with paroxysmal tachycardias and has caused a revolution in the practice of electrophysiology. Some investigators have expressed that concern over procedural success in an increasingly interventional specialty threatens to eclipse attempts to understand the physiology of arrhythmia syndromes. Alternatively, due to the precise and directed nature of the lesions created with radiofrequency energy, catheter ablation procedures have allowed investigation to continue at a more focused level. In this article, the insights provided by the catheter ablation experience into the physiology of arrhythmias mediated by accessory AV pathways will be reviewed. Although the learning process was sometimes delayed by the nearly immediate success of radiofrequency catheter ablation, difficult situations have continued to renew efforts for understanding at a deeper level. Conscious attempts at "learning while burning" will provide the opportunity to investigate aspects of bypass tract physiology that remain incompletely characterized, such as partial response to therapy and late recurrence.

Atrial fibrillation: maintenance of sinus rhythm versus rate control

Atrial fibrillation represents a common and challenging arrhythmia. A rational approach to management of the individual case depends on careful assessment of the temporal of the arrhythmia, any associated cardiovascular disease, and any particular features suggesting the advisability or risks of any particular treatment regimen. The nature of an arrhythmia and of individual patient factors change over time, requiring a flexible approach to long-term treatment that may be defined only after months or years. While new treatment options such as catheter ablation techniques and implantable atrial defibrillators are being tested, old therapies (e.g., low-dose amiodarone) are undergoing reappraisal. Increasing recognition of the dangers of antiarrhythmic therapy used to maintain sinus rhythm is focusing attention on nonpharmacologic methods. All patients with persistent atrial fibrillation merit serious consideration for direct current cardioversion before accepting that atrial fibrillation is permanent, and many patients may benefit from more than one attempt to restore and maintain sinus rhythm.

Catheter ablation for the treatment of paroxysmal supraventricular tachycardia

Radiofrequency catheter ablation has evolved into a front-line curative therapy for patients who have paroxysmal supraventricular tachycardia secondary to Wolff-Parkinson-White syndrome. AV nodal reentrant tachycardia, and atrial tachycardia. In patients with accessory pathways, cure rates exceed 90% in almost all anatomic locations. Equally high success rates are noted in patients with atriofascicular pathways and the permanent form of junctional reciprocating tachycardia. Complications secondary to catheter ablation of accessory pathways occur in 1% to 3% of patients and include cardiac perforation, tamponade, AV block, and stroke. In patients with AV modal reentrant tachycardia, selective slow pathway ablation is curative in over 95% of patients with a very low risk of AV block. Atrial tachycardias originating in both the left and right atria can be successfully ablated in over 80% of patients. Given the overall effectiveness of this procedure, radiofrequency catheter ablation should be considered as front-line therapy in patients with recurrent or drug-refractory paroxysmal supraventricular tachycardia. Although an effective therapy, the risks and benefits of this procedure need to be assessed in all patients who are candidates for this procedure.

Feasibility of radiofrequency powered, thermal balloon ablation of atrioventricular bypass tracts via the coronary sinus: in vivo canine studies

Radiofrequency catheter ablation of left-sided accessory pathways is technically demanding and usually requires left heart catheterization. The feasibility of creating lesions from within the coronary sinus of sufficient size to ablate accessory pathways in humans using a thermal balloon catheter was studied in 20 dogs. In group 1 (n = 14), 17 thermal inflations were performed in 12 dogs at either 70 degrees, 80 degrees, or 90 degrees C each for 30 or 60 seconds (in 2 dogs two non-thermal control inflations were performed). Animals were sacrificed 6.3 +/- 1.6 days later. In group 2 (n = 6), seven thermal inflations were performed at 90 degrees C each for 180, 300, or 360 seconds. Group 2 animals received antiplatelet and anticoagulant therapy for 1 week and were sacrificed at 13 +/- 10.7 days. In both groups, hemodynamic, angiographic, and electrocardiographic studies were performed at baseline, 1 hour after inflation, and prior to sacrifice. All dogs remained clinically stable throughout the procedure and no complications were attributed to the effect of thermal inflation. Thermal lesions measured 14.4 +/- 4.4 mm in length and extended from the coronary sinus intima to a mean depth of 2.9 +/- 1.2 mm (range 1.4-6.5 mm). Group 2 lesions were significantly deeper than group 1 lesions (P = 0.03). Of the 24 thermal lesions created, atrial necrosis was present in 23 and ventricular necrosis in 11. In all lesions there was some degree of either atrial necrosis, ventricular necrosis, or both. A variable degree of coronary sinus thrombus was present in 18 dogs without clinical sequelae. It is concluded that radiofrequency balloon heating via the coronary sinus can create thermal lesions in the atrioventricular sulcus of dogs that may be of sufficient size to ablate accessory left-sided pathways in humans.

Efficacy and tolerability of transvenous low energy cardioversion of paroxysmal atrial fibrillation in humans

OBJECTIVES

This study investigated the efficacy and tolerability of low energy shocks for termination of atrial fibrillation in patients, using an endocardial electrode configuration that embraced both atria.

BACKGROUND

In animals, low energy biphasic shocks delivered between electrodes in the coronary sinus and right atrium have effectively terminated atrial fibrillation. If human defibrillation thresholds are sufficiently low, atrial defibrillation could be achieved in conscious patients using an implanted device.

METHODS

Twenty-two consecutive patients with stable atrial fibrillation were studied during electrophysiologic testing. Biphasic R wave synchronous shocks were delivered between large surface area electrodes in the coronary sinus and high right atrium, using a step-up voltage protocol starting at 10 or 20 V and increasing to a maximum of 400 V. Patients were conscious at the start of the study and were asked to report on symptoms but were sedated later if shocks were not tolerated.

RESULTS

Cardioversion was achieved in all 19 patients who completed the study, with a mean (+/- SD) leading-edge voltage of 237 +/- 55 V (range 140 to 340) and mean energy of 2.16 +/- 1.02 J (range 0.7 to 4.4). The mean maximal shock delivered without sedation was 116 +/- 51 V (range 60 to 180). No proarrhythmia or mechanical complications occurred.

CONCLUSIONS

The delivery of biphasic R wave synchronous shocks between the high right atrium and coronary sinus can terminate atrial fibrillation with very low energies. General anaesthesia is not required, and a minority of fully conscious patients are able to tolerate this method of cardioversion.

Catheter ablation of the accessory pathways of the Wolff-Parkinson-White syndrome and its variants

The basis of arrhythmias in the Wolff-Parkinson-White (WPW) syndrome and its variants is the presence of accessory atrioventricular connections. Those variants include the concealed form of the WPW syndrome, the permanent form of junctional reciprocating tachycardia, and Mahaim preexcitation. In all forms of symptomatic WPW syndrome, catheter ablation of the accessory atrioventricular connections using radiofrequency current has become the treatment of choice. This review traces the development of this therapy, outlines the basics of the technique, summarizes the results reported in the largest series, indicate remaining areas of controversy, and discusses the indications and limitations of radiofrequency ablation therapy.

Ablative therapy for ventricular arrhythmias

Radiofrequency catheter ablation techniques have enjoyed successful applications in patients with a wide variety of supraventricular tachycardias, especially the Wolff-Parkinson-White syndrome and atrioventricular nodal reentry. More recent reports have shown successful applications in patients with atrial tachycardias and atrial flutter. In addition to these, there are now reports of success during attempts to use radiofrequency techniques to eliminate ventricular tachycardia (VT), both in patients without structural heart disease (idiopathic VT) and patients with structural heart disease (primarily coronary artery disease). Techniques to map sites for ablation in patients with idiopathic VT usually include identifying early endocardial activation and using pace mapping. Success rates for ablation of idiopathic VT have been very high (over 90%) in patients with VT arising from the right ventricular outflow tract. Success rates have not been quite as high when VTs arising from sites other than the right ventricular outflow tract are targeted in the patient with idiopathic VT. In patients with VT caused by coronary artery disease, early endocardial activation and pace mapping can be unreliable. In these patients, searching for mid-diastolic potentials or showing concealed entrainment have proved more reliable. When these latter techniques are applied, success rates in eliminating a single focus of VT in a patient with coronary artery disease has been reported to be as high as 60% to 80%. Future therapies will include new energy sources, new (larger and/or cooled) electrodes, and multipoint catheter mapping, possibly using body surface mapping techniques.

Radiofrequency catheter ablation of septal accessory atrioventricular pathways

OBJECTIVE

Septal accessory atrioventricular pathways are recognised as being more difficult to ablate than pathways in other locations. This paper describes an experience of 48 consecutive patients with septal accessory pathways who had catheter ablation with radiofrequency current.

PATIENTS AND METHODS

There were 28 male and 20 female patients, mean (SD) age 35 (17). 43 patients had a single accessory pathway and 5 patients had multiple accessory pathways. Pre-excitation was present in 37 patients, and 11 patients had concealed accessory pathways. 21 patients had had a previous electrophysiological study. Catheter ablation was undertaken with radiofrequency current delivered by a standard unipolar technique or by delivery of current across the septum (the bipolar technique).

RESULTS

The median total procedure time was 167 (83) minutes including a 30-40 minute observation period after the abolition of conduction by the accessory pathway. The median total fluoroscopic time was 56 (30) minutes. 42 (88%) out of 48 patients had successful ablation of the pathway during the first session. In the six patients in whom the procedure failed, five had a midseptal pathway and one had a right anteroseptal pathway. A second attempt at ablation was made in two patients and succeeded in both. In total, 49 accessory pathways were successfully ablated in 44 (92%) out of 48 patients. The bipolar technique was used in 11 patients and succeeded in 10 patients. Standard unipolar current delivery had previously failed in seven of the 11 patients. Complications developed in two patients with a mid septal pathway (one with complete atrioventricular block and the other with a small pericardial effusion).

CONCLUSION

Radiofrequency catheter ablation of septal accessory pathways is efficacious and safe. The procedure time can be shortened and success rate can be increased after improvement of the technique--that is, consideration of a bipolar approach for energy delivery in difficult cases.

Radiofrequency catheter ablation of accessory pathways: a contemporary review

Catheter ablation techniques are now advocated as the first line of therapy for arrhythmias caused by accessory pathways (APs). The most common energy source is radiofrequency current, but technical characteristics vary. Several parameters can be used to determine the optimal target site: AP potential, AV time, atrial or ventricular insertion site, or unipolar morphology. Specific considerations are needed depending on AP location. Despite the different approaches described, there is no significant difference in the reported success rate, which is over 90%. However, the number of radiofrequency applications needed to achieve ablation appears to differ significantly, with median values from 3 to 8 reported. A combination of criteria related to both timing and direction of the activation wavefront or use of subthreshold stimulation could improve the accuracy of mapping. In patients with "resistant" APs, different changes in ablation technique must be considered during the procedure to achieve elimination of AP conduction. The incidence of complications in multicenter reports is close to 4%, with a recurrence rate of 8%. The long-term safety of catheter ablation requires further study.

Catheter ablation using radiofrequency or low-energy direct current in pediatric patients with the Wolff-Parkinson-White syndrome

Percutaneous ablation of accessory pathways was performed in 22 consecutive children and adolescents (9 boys and 13 girls, age range 8 to 18 years). Low-energy direct current (DC) was used exclusively in the first 6 patients, whereas ablation was performed with radiofrequency energy in the following 16. Accessory pathways were located in the left free wall in 15 patients, were posteroseptal in 3, were in the right free wall in 3 and were anteroseptal in 1. A concealed accessory pathway was present in 7 patients (32%). There was no significant difference in clinical or electrophysiologic variables between both groups. Catheter ablation was successful in the initial 6 patients using low-energy DC, as compared with 13 of 16 patients using radiofrequency ablation. Low-energy DC was successful as a backup power source in all 3 patients who had unsuccessful radiofrequency ablation. There was no complication. The median procedural and fluoroscopic times for successful ablation were 2.5 hours and 49 minutes, respectively (p = NS between both power sources). Accessory pathway conduction recurred in 2 patients (33%) who had low-energy DC as compared with 1 (6%) who had radiofrequency ablation (p = NS). These 3 patients had successful reablation of their accessory pathways. In children and adolescents with accessory pathways, both new power sources compare favorably, with an overall success rate of ablation of 100% (22 of 22 patients). Radiofrequency ablation should be used initially because it does not require general anesthesia and is associated with a lower rate of recurrence of accessory pathway conduction.(ABSTRACT TRUNCATED AT 250 WORDS)

Results of a comparative study of low energy direct current with radiofrequency ablation in patients with the Wolff-Parkinson-White syndrome

OBJECTIVE

To compare two new power sources for catheter ablation in patients with the Wolff-Parkinson-White syndrome.

DESIGN

120 consecutive patients with accessory pathways had catheter ablation. Low energy direct current (DC) was used in the first 60 patients and radio-frequency current in the next 60 patients.

SETTING

Electrophysiological laboratory of a large heart institute.

PATIENTS

72 men and 48 women (mean (SD) age 35 (14) years (range 9-75)). The accessory pathways were in the left free wall in 73 patients. They were posteroseptal in 35 patients, in the right free wall in five, and anteroseptal in seven. There was no significant difference in the clinical or electrophysiological variables between the two ablation groups.

RESULTS

Catheter ablation with low energy direct current was successful in 55/60 patients (92%) and radiofrequency energy was successful in 52/60 patients (87%). Low energy direct current was also successful in four of the eight patients in whom radiofrequency ablation had failed. Radiofrequency ablation was successful in two of the five patients in whom low energy direct current ablation had failed. The mean (SD) procedure and fluoroscopy times for successful ablation were 3.2 (1.5) h and 61 (40) min respectively. These times were similar for both power sources. Accessory pathway conduction recurred in 17 patients (28%) who had low energy direct current and four patients (7%) who received radiofrequency energy (p < 0.004). All patients with recurrence of an accessory pathway had successful re-ablation.

CONCLUSIONS

Both new power sources successfully ablated accessory pathways, (overall success rate 94% (113/120 patients)). Radiofrequency ablation, however, did not require general anaesthesia and was associated with a significantly lower rate of recurrence of accessory pathway conduction. Therefore radiofrequency should be used initially for ablation. Low energy direct current may be most useful as a back-up in patients in whom radiofrequency ablation fails.

Radiofrequency ablation of accessory pathways associated with congenital heart disease including heterotaxy syndrome

Congenital heart disease complicates the management of most accessory pathway-mediated tachycardias and also increases the challenge of radiofrequency ablation. Since 1990, radiofrequency ablation of accessory atrioventricular (AV) pathways has been attempted in 10 patients (age range 3.5 months to 30 years) with congenital heart disease: Ebstein's anomaly (n = 5), heterotaxy with AV discordance (n = 3), tetralogy of Fallot (n = 1) and total anomalous pulmonary venous return (n = 1). Eight patients had manifest Wolff-Parkinson-White syndrome and 2 had concealed pathways. Five patients had multiple pathways including 4 of the 5 with Ebstein's anomaly. Of 16 pathways total, 15 were associated with the tricuspid valve including all pathways in the patients with Ebstein's anomaly and heterotaxy. The His bundle area was identified in all patients and involved an anterior AV node in 2 of 3 with heterotaxy. Ablation was performed on the atrial side of the AV ring in all cases. No instance of AV block was encountered. Complete success was achieved in 6 patients including the 3 with heterotaxy. In 2 patients, manifest preexcitation was eliminated and clinical symptoms were greatly modified. The procedure was transiently successful in 1 patient who later had surgical interruption of the accessory pathway during tetralogy of Fallot repair. Ablation was unsuccessful in 1 patient. Thus, the overall success was 80%.

Physics and engineering of transcatheter cardiac tissue ablation

Ablation of arrhythmogenic cardiac tissues has emerged as one of the most important advances in cardiac electrophysiology. With the introduction of transcatheter ablation, the treatment of ventricular tachycardia, Wolff-Parkinson-White syndrome and other cardiac arrhythmias has progressed from an expensive and painful surgical therapy accompanied by a long recovery period to the less expensive, less traumatic transcatheter approach. The feasibility of cardiac ablation, along with the increasing number of physicians using the technique, requires understanding of the anatomic and electrophysiologic bases of transcatheter ablation as well as the different technologies, their limitations and complications. This report provides an overview of the physical, scientific and technical aspects of cardiac ablation performed with the methods currently available and a summary of the limitations of each method and expected future technologic developments in this growing field. Emphasis is placed on radiofrequency and direct current energies, the primary methods now used. Methods such as cryoablation and laser, and microwave and chemical ablation are discussed with less detail because the method of delivering energy for these ablative procedures has not been fully developed.

Patterns of radiofrequency catheter ablation of left free-wall accessory pathways: implications for accessory pathway anatomy

Despite the abundance of literature on the electrophysiology of accessory pathways, clinical data on their anatomic properties remain infrequent. The small and discrete nature of lesions generated by radiofrequency (RF) energy may allow better characterization of accessory pathway anatomy in the intact heart. RF catheter ablation was performed on 40 left free-wall accessory pathways in 39 consecutive patients with a unipolar endocardial approach. The patterns of accessory pathway ablation were identified. Spatial-electrophysiologic information provided by the ablation catheter at individual sites of RF application and corresponding data from the coronary sinus catheter were correlated with the effects of RF energy on accessory pathway conduction. Of 39 accessory pathways permanently (n = 37) or transiently (n = 2) ablated, 24 had "simple" ablation, with abolition of conduction by one individual RF application. In 15 of 24 pathways that could be crossed by the coronary sinus catheter, the concordance in anatomic and electrophysiologic information between the site of earliest retrograde atrial activation and the effective ablation position (ventricular approach) suggested a perpendicular fiber course. Fifteen pathways had "complex" ablations; of these, eight had spatial-electrophysiologic discordance between the atrial and ventricular insertions, suggesting an oblique fiber orientation. Seven pathways had modification or transient suppression of conduction, with or without subsequent abolition of conduction at identical or physically disparate (> 1 cm apart) sites; four pathways had sequential ablation of antegrade and retrograde conduction. These raised possibilities of broad fiber span and functional longitudinal dissociation of accessory pathway conduction. Accessory pathways with simple and complex ablations did not differ in clinical and electrophysiologic parameters. Complex ablations demanded more lengthy and difficult procedures.(ABSTRACT TRUNCATED AT 250 WORDS)

Role of radiofrequency ablation in the management of supraventricular arrhythmias: experience in 760 consecutive patients

INTRODUCTION

Several reports have demonstrated that radiofrequency catheter ablation provides effective control of a variety of supraventricular tachycardias. However, the efficacy, complications, risk of arrhythmia recurrence, and follow-up survival analysis have not been reported in a large series of consecutive patients with supraventricular arrhythmias with diverse electrophysiologic mechanisms. This report details the results of radiofrequency catheter ablation in 760 consecutive patients (386 males, 374 females) with a wide variety of supraventricular tachycardias treated at one center.

METHODS AND RESULTS

Arrhythmias were associated with the presence of an accessory pathway in 363 patients (384 accessory pathways), including four patients with Mahaim fibers and eight patients with the permanent form of junctional reciprocating tachycardia. The mechanism of the clinical arrhythmia was AV nodal reentrant tachycardia in 245 patients, and a primary atrial tachycardia in 20 patients (ectopic atrial tachycardia in 16 patients and sinus nodal reentry in 4 patients). Ablation of the reentrant circuit of atrial flutter within the right atrium was attempted in 13 patients. AV node ablation and permanent pacemaker implantation were performed in 119 patients with medically refractory atrial fibrillation or flutter. Radiofrequency catheter ablation was successful in 346 of 363 patients (95.3%, CI 93.1%-97.5%) with accessory pathways (367 of 384 pathways, 95.6%, CI 93.5%-97.6%) with a complication rate of 1.1% and a recurrence rate of 5.5%. Successful accessory pathway ablation was achieved for 179 of the first 192 pathways treated (93.2%, CI 89.7%-96.6%) and increased to 188 of 192 pathways (97.9%, CI 95.9%-99.9%) over the second half of the series. AV nodal reentry was successfully abolished in 244 of 245 patients (99.6%, CI 98.8%-100%) by selective ablation of the slow pathway in 234 patients and the fast pathway in 10 patients. The complication rate in this group was 2.0% with a recurrence rate of 6.5%. All 20 primary atrial tachycardias were successfully ablated with no complications and a recurrence rate of 15%. The reentrant circuit of atrial flutter was ablated successfully in 10 of 13 patients (77%) with recurrent atrial flutter in one additional patient. Complete AV block was achieved in 117 of 119 (98.3%, CI 96.0%-100%) patients with atrial fibrillation or flutter treated by AV nodal ablation with a complication rate of 0.8% and recurrence of AV conduction in 6%. The median duration of fluoroscopy exposure for the population was 23.4 minutes. The overall primary success rate for the entire population was 97.0% (737 of 760 patients, CI 95.8%-98.2%).

CONCLUSION

Thus, the results of this large series of patients demonstrates the safety and efficacy of radiofrequency ablation for the treatment of a wide variety of supraventricular arrhythmias. It also appears that increasing experience with these procedures increases the rate of successful ablation and decreases the risk of complications.

Curative radiofrequency catheter ablation for permanent junctional reciprocating tachycardia

Two patients with the permanent form of junctional reciprocating tachycardia successfully treated with the radiofrequency catheter ablation technique are described. In both patients a reentrant tachycardia utilizing a concealed slow conducting posterior septal accessory pathway for retrograde conduction was demonstrated. Radiofrequency current was delivered below the coronary sinus orifice. The procedure resulted in ablation of the accessory pathway conduction in both patients. During the follow-up, both patients remained free from tachycardia on no medication. This report demonstrates that the arrhythmogenic substrate of the permanent junctional reciprocating tachycardia can be easily suppressed by means of the radiofrequency catheter technique.

Radiofrequency catheter ablation for paroxysmal supraventricular tachycardia: a report of 135 procedures

BACKGROUND

Paroxysmal Supraventricular Tachycardia (PSVT) is a common condition which until recently has been treated with anti-arrhythmic drugs or surgery. Radiofrequency (RF) catheter ablation is a new mode of treatment which provides a cure of this condition.

AIMS

To present our early experience of RF catheter ablation for PSVT.

METHODS

One hundred and thirty-five procedures were performed in 117 patients. The diagnostic study and therapeutic catheter ablation were performed as a combined electrophysiological procedure in 74 patients (63%). In 58 patients (50%), PSVT was due to Atrio-ventricular junctional (nodal) re-entrant tachycardia (AVJRT). Twenty-five of the 58 patients underwent a fast pathway ablation while 33 had ablation of their slow pathway. The mean number of radiofrequency pulses delivered was ten for a mean duration of 25 seconds. Radiofrequency ablation of accessory pathways was attempted in 58 patients; pathways were left-sided in 29 patients, postero-septal in 21, midseptal in five, Mahaim connection in two, antero-septal in one and right free wall in one patient. One patient with incessant automatic atrial tachycardia also underwent a successful RF ablation.

RESULTS

Using RF ablation cure of PSVT was achieved in 90% of patients. Cure of AVJRT was achieved in 95% (55/58) of patients using either fast or slow pathway ablation. Only one patient required permanent pacemaker implantation for Mobitz type I AV block following fast pathway ablation. The overall success rate for ablation of accessory pathways was 85%. There is an operator learning curve for this procedure suggested by the fact that the success rate for accessory pathway ablation at first attempt was 63% in the first 29 patients and 93% in the remaining 29. There was no significant morbidity or mortality during or after the procedure. In a mean follow-up of nine months in the patients with successful ablation only two patients with AVJRT had a recurrence of documented PSVT. Both these patients had successful repeat RF ablation. Catheter ablation using radiofrequency energy is an effective and safe therapeutic option for patients with symptomatic PSVT.

Comparison of catheter ablation using direct current energy versus radiofrequency: observations in 147 patients with supraventricular tachyarrhythmias

We studied the follow-up of 147 patients who underwent catheter ablation because of drug resistant supraventricular tachyarrhythmias. Direct current (DC) ablation was performed in 116 patients, while 31 patients underwent radiofrequency (RF) ablation. In 101 patients (87%) with DC ablation and in 28 patients (90%) with RF ablation, complete atrioventricular (AV) block was achieved initially. Fifteen patients (13%) with DC ablation and three patients (11%) with RF ablation resumed AV conduction. Serious complications occurred in eight patients (7%) with DC ablation and in none of the patients with RF ablation. During the mean follow-up of 45 +/- 24 months, 13 patients died (11%) who underwent DC ablation; during the mean follow-up of 11 plus or minus 3 months, no patient died who had had RF ablation. Transcatheter ablation using DC or RF is an effective treatment in patients with drug resistant supraventricular arrhythmias, providing a beneficial long-term outcome including an improved quality of life. Although the risk of complications is low, this procedure should be reserved for patients with supraventricular arrhythmias who do not respond to conventional drug therapy.

Effect on coronary artery anatomy of radiofrequency catheter ablation of atrial insertion sites of accessory pathways

OBJECTIVES

The purpose of this study was to analyze the effects of radiofrequency catheter ablation of the atrial insertion site of accessory pathways on the angiographic appearance of coronary arteries.

BACKGROUND

Radiofrequency catheter ablation of accessory pathways requires the application of energy to the endocardial surface of the atrioventricular groove adjacent to the major epicardial coronary arteries. A systematic analysis of the effect of radiofrequency ablation on coronary arteries has not previously been demonstrated.

METHODS

Seventy consecutive patients with 76 accessory pathways (7 right free wall, 44 left free wall, 12 posteroseptal, 8 anteroseptal and 5 midseptal) were studied. Quantitative coronary angiography was performed before, immediately after and a mean of 69 +/- 42 days after radiofrequency catheter ablation.

RESULTS

Coronary artery diameter adjacent to the ablating electrode was 2.6 +/- 0.9 mm before ablation, 2.7 +/- 0.9 mm immediately after ablation and 2.7 +/- 1.0 mm at the time of follow-up study. Angiographic findings were unchanged from baseline in 69 of 70 patients immediately after ablation and in all 70 patients at the time of follow-up study.

CONCLUSIONS

Radiofrequency catheter ablation of the atrial insertion site of accessory pathways does not result in short-term angiographic changes in coronary artery anatomy.

Radiofrequency current catheter ablation for control of supraventricular arrhythmias

With the advent of radiofrequency energy, catheter ablation techniques have become an accepted form of treatment for a variety of supraventricular arrhythmias. The ablation of the atrioventricular (AV) node was performed first and is now widely used in patients with refractory atrial fibrillation or flutter. Ablation has also replaced surgery in patients with preexcitation syndromes, and as the complication rate in experienced centers is low, it has become the first line of treatment in these institutions. The results of catheter ablation in AV nodal reentrant tachycardia are excellent as well, although there is still debate about whether "slow" pathway ablation is superior to "fast" pathway ablation. Radiofrequency current ablation has also contributed to a better understanding of the pathophysiology of AV nodal reentrant tachycardia, as it has provided evidence for atrial participation in the reentrant circuit. Experience with atrial tachycardias and tachycardias due to Mahaim fibers remains limited. The ideal source of energy for specific arrhythmias is still unknown and improvement in catheter technology is needed.

Reappraisal of radiofrequency ablation of multiple accessory pathways

Complete electrophysiologic study and radiofrequency ablation were performed in 145 consecutive patients with Wolff-Parkinson-White syndrome. Presence of multiple accessory atrioventricular pathways was documented in 20 patients (13.8%); 17 had two, two had three, and one had four accessory pathways. Location of accessory pathways was posteroseptal in 18, left free wall in 15, right free wall in nine, and right midseptal in two. Of the 44 pathways, 36 were found during baseline electrophysiologic study and eight were found after successful ablation of the initially attempted pathways. After delivery 20 +/- 23 pulses (per patient) of radiofrequency energy (37 +/- 6 W, 70 +/- 30 seconds), 43 accessory pathways were ablated successfully without complications. Duration of the procedure (4.5 +/- 1.7 vs 3.7 +/- 1.6 hours, p < 0.05) and radiation exposure time (53 +/- 30 vs 38 +/- 18 minutes, p < 0.05) were longer in patients with multiple pathways, whereas the success rate (95% vs 95%, p > 0.05) and incidence of recurrent conduction (11% vs 11%, p > 0.05) were similar in patients with single or multiple accessory pathways. These findings confirmed that multiple accessory pathways were common in patients with Wolff-Parkinson-White syndrome, and these pathways could be ablated successfully by radiofrequency energy with a success rate comparable to that of a single accessory pathway.

Arrhythmogenicity of catheter ablation in supraventricular tachycardia

To evaluate arrhythmogenicity in patients who receive a modified direct-current (DC) shock ablation (distal pair of electrodes connected in common as the cathode) or radiofrequency (RF) ablation of supraventricular tachycardia, a prospective study was performed with signal-averaged ECG, 24-hour Holter monitoring, electrophysiologic study (EPS) for ventricular tachycardia (VT), and treadmill exercise test. Sixty-nine consecutive patients with documented paroxysmal supraventricular tachycardia were included. Twenty-eight patients proved to have atrioventricular nodal reentrant tachycardia, and 41 patients had atrioventricular reciprocating tachycardia that involved accessory atrioventricular pathways. The first 34 patients received DC shock ablation and the other 35 patients received RF ablation. Signal-averaged ECG, Holter monitoring, and EPS for VT were performed before ablation, immediately after ablation, then 1 week, 2 weeks (Holter monitoring), 1 month (except EPS), and 3 months after ablation. Treadmill exercise testing was performed before ablation, and at 1 week and 3 months after ablation. The root mean square, low-amplitude signal and QRS duration of signal-averaged ECG disclosed no significant change after either DC or RF ablation up to 3 months. Late potential developed in only one patient in the DC shock group and it was considered to be innocuous because neither VT nor ventricular fibrillation was noted or induced. Increases in the number of ventricular premature contractions and in short-run VT were detected by Holter monitoring in the first week after either mode of ablation (p < 0.001 for the DC shock group; p < 0.05 for the RF group), which were greater (p < 0.05) and lasted longer in the DC shock group than in the RF group.(ABSTRACT TRUNCATED AT 250 WORDS)

Factors predicting success in DC catheter ablation of accessory pathways

In a series of 33 patients with accessory pathways, 26 had successful catheter ablation (fulguration [23 patients] or modification [3 patients]) of their accessory pathway conduction, and could be considered as a clinical success. One hundred thirteen single discharge or double discharge shocks were delivered, and each shock was studied to reveal which parameters were important to predict the success or failure of catheter ablation. Double discharge shocks resulted in successful accessory pathway modification or ablation twice as often as single discharge shocks (32% vs 16%). This effect was more pronounced in left lateral accessory pathways (48% vs 4%). Shocks in the electrophysiologically defined ventricular zone were more likely to be successful (33%) than shocks delivered in the atrial zone (14%), irrespective of accessory pathway location. The presence of a probable Kent potential was the parameter most strongly associated with success. The parameter most strongly associated with failure, with a 100% negative predictive value, was the absence of earliest activation recorded on the ablating catheter prior to shock delivery. An AV interval of < 60 msec significantly divided the successful from the unsuccessful shocks (P = 0.01). The VA interval during orthodromic reciprocating tachycardia or right ventricular stimulation did not allow for significant division into successful and unsuccessful attempts in this relatively short series. VA intervals, when longer, were predictive of failure but, when shorter, had low positive predictive value. Mean follow-up in 25 successful patients was 15 +/- 6 months. All patients did well in the follow-up period. Neither those patients with ablation nor modification of the accessory pathway had recurrent episodes of tachycardia or required pharmacological treatment for control of arrhythmias.

Radiofrequency catheter ablation for treatment of Wolff-Parkinson-White syndrome--short- and long-term follow-up

One hundred and twenty-five patients with accessory pathways mediated tachyarrhythmias underwent radiofrequency ablation. Right-sided accessory pathways were ablated from the atrial aspect of the tricuspid anulus (all from the femoral vein approach) and the left-sided accessory pathways were ablated from the atrial or ventricular aspect of the mitral anulus. Immediately after the procedures, 3 of 8 accessory pathways (38%) and 131 of 137 accessory pathways (95%) were ablated successfully with radiofrequency through a small-tip (2 mm) and a large-tip (4 mm) electrode catheter, respectively. Seven of the 11 accessory pathways that failed radiofrequency ablation had a later successful direct current ablation. During follow-up (3 to 22 months), serial electrophysiological study showed that 11 of the 114 patients (10%) with successful ablation had return of accessory pathway conduction (2 had recurrence of tachycardia, 2%). Complications included accidental AV block (1 patient), cardiac tamponade (1 patient) and possible aortic dissection (1 patient). Transient proarrhythmic effects (more atrial and ventricular premature beats) were seen during the first week and sustained ventricular tachyarrhythmias were not inducible. In a successful session, procedure and radiation exposure times (including the time for diagnostic procedures) were 3.8 +/- 0.2 h and 45 +/- 4 min, respectively. This study confirms that radiofrequency ablation with a large-tip electrode catheter is an effective and relatively safe nonsurgical method for treatment of Wolff-Parkinson-White syndrome, with a low complication and recurrence rate.

Long-term effects of percutaneous laser balloon ablation from the canine coronary sinus

BACKGROUND

Radiofrequency catheter ablation of left-sided accessory pathways is becoming the first line of therapy for patients with symptomatic Wolff-Parkinson-White syndrome. Nevertheless, alternative ablation techniques merit development, at least as supplementary modalities for cases in which conventional ablation approaches may prove unsuccessful. We recently reported the short-term results with transcatheter laser balloon ablation from the coronary sinus in a canine model, proving that the procedure is feasible for the potential ablation of left-sided accessory pathways. We now report the effects of percutaneous transcatheter laser balloon ablation in a chronic canine model.

METHODS AND RESULTS

Twenty adult mongrel dogs were studied. After baseline coronary arteriography, left ventriculography, and coronary sinus angiography were obtained, 15 dogs received two or three consecutive laser doses from the coronary sinus of 30-40 W for 15-30 seconds, for a total cumulative energy of 1,200-2,400 J. The five remaining animals underwent a procedure consisting of balloon sham inflation without laser exposure and served as controls. After a mean follow-up of 6 weeks, the angiographic procedures were repeated, and the animals were killed. The mean extent of the fibrotic lesion was 15 mm long, 6 mm wide, and 4.5 mm deep and involved the coronary sinus wall, atrium, and, frequently, the summit of the posterior left ventricular wall. Six animals (four in the study group and two in the control group) showed asymptomatic narrowing of the coronary sinus lumen but always with total angiographic reconstitution due to extensive collateral circulation. The circumflex artery and mitral valve were intact angiographically and histologically in all animals.

CONCLUSIONS

Percutaneous transcatheter laser balloon ablation via the coronary sinus produces a lesion that may be anatomically well suited for left-sided accessory pathway ablation. Although coronary sinus narrowing may occur, adverse physiological effects are unlikely due to the development of extensive collateral circulation. Systematic clinical studies of this new approach to catheter ablation appear warranted.