Radiofrequency catheter ablation of idiopathic left ventricular tachycardia guided by a Purkinje potential

Idiopathic left ventricular tachycardia with block between purkinje potential and ventricular myocardium

We performed radiofrequency current catheter ablation in a patient with idiopathic LV. While mapping the inferoapical LV septum during tachycardia, spontaneous termination of tachycardia was observed with block between Purkinje (P) potential and ventricular electrogram (P-V block). The cycle length of the tachycardia was associated with prolongation of P-P interval and P-V interval. P potential recording at this site was earliest and at very low amplitude during tachycardia. The radiofrequency current at this site was successful. These findings indicated that Purkinje fiber was a critical part of the tachycardia circuit. Ablation was successful at a site where both an earliest and low amplitude P potential was recorded during tachycardia, and where P-V block that was induced by catheter manipulation was observed during tachycardia.

Radiofrequency ablation of idiopathic left ventricular tachycardia with changing ECG morphology

Idiopathic left ventricular tachycardia is a distinct clinical entity with a typical ECG of right bundle branch block and left axis deviation. We presented a 39-year-old man with idiopathic left ventricular tachycardia, which demonstrated change in the configuration of QRS complex during successive radiofrequency catheter ablation. We proposed that this idiopathic left ventricular tachycardia may have alternative pathways within the reentrant circuit leading to different exits.

A nonfluoroscopic catheter-based mapping technique to ablate focal ventricular tachycardia

The recent introduction of a nonfluoroscopic electroanatomical cardiac mapping system (CARTO) is an exciting development in catheter ablation treatment of cardiac arrhythmias. The system uses ultralow magnetic fields to locate a sensor positioned near the tip of a regular mapping and ablation catheter. The catheter location and electrograms are recorded and reconstructed in real-time and presented as a three-dimensional geometrical mapped color coded with the electrophysiological information. The CARTO represents an important tool to guide the ablation of patients who have focal tachycardia (e.g., right ventricular outflow tract [RVOT] tachycardia and idiopathic left ventricular [ILV] tachycardia). This study describes how the CARTO system is useful in mapping and ablating these arrhythmias. Two case illustrations, one patient with RVOT tachycardia and another with ILV tachycardia, are described in this article. The tachycardia was mapped and ablated using the new electromagnetic catheter technology creating an electroanatomical map of the arrhythmia focus for each tachycardia without fluoroscopy; both tachycardias were successfully ablated, terminated, and rendered noninducible. The CARTO system is useful in mapping and guiding the ablation of focal tachycardia and merits further study.

Radiofrequency catheter ablation of idiopathic left ventricular tachycardia originating in the left anterior fascicle

Radiofrequency catheter ablation has been used to treat idiopathic left ventricular tachycardia with high success rates. The majority of reported cases have exhibited the typical findings of right bundle branch block morphology with left axis deviation and originate from within or near the left posterior fascicle. We report a case of idiopathic left ventricular tachycardia originating from within or near the left anterior fascicle, which was successfully ablated using a local Purkinje potential as a guide.

Incessant fascicular tachycardia: a cause of arrhythmia induced cardiomyopathy

An incessant ventricular tachycardia arising from the posterior fascicle is reported in a 29-year-old woman. This fascicular tachycardia was due to triggered activity and was clinically induced by an underlying paroxysmal atrial fibrillation. The initial echocardiographic evaluation revealed biventricular dysfunction with an ejection fraction of 30%. On propranolol, the patient has remained asymptomatic and the ventricular function has become normal after 3 months free of arrhythmia.

[Current indications for implantable automatic defibrillators]

Since the first implantation in man in 1980 implantable cardioverter defibrillator technology has greatly improved and the number of devices implanted has increased considerably in recent years. Non-thoracotomy lead systems and biphasic shocks are now the approach of choice, offering nearly a 100% success rate. This paper version reviews the current indications for the implantation of implantable cardioverter defibrillator and is an upgraded of an article previously published by the Arrhythmia's Section of the Spanish Society of Cardiology. Recommendations for qualification of centres implanting defibrillators and follow up are also addressed.

Repetitive ventricular responses induced by radiofrequency ablation for idiopathic ventricular tachycardia originating from the outflow tract of the right ventricle

In 23 consecutive patients, radiofrequency (RF) ablation was used as treatment for idiopathic ventricular tachycardia (VT) originating from the outflow tract of the right ventricle. In this study, we focused on the repetitive ventricular response (> 5 consecutive QRS beats during RF application). The incidence and clinical implications of the repetitive ventricular response were examined through the results of endocardial mapping and RF ablation. VT origin was mapped as the earliest activation site during VT, and it was determined within 0.5 x 0.5 cm (narrow site) in 13 patients and wider than 0.5 x 0.5 cm (wide origin) in the other 10 patients. The repetitive ventricular response was induced during application of RF current in 14 of 23 patients (61%), and it was more frequently observed in VT from a wide origin (100%) than in the VT from a narrow site (31%). The QRS morphology of the repetitive ventricular response was identical to that of clinical VT. As RF application was continued and/or repeated, the RR interval of the repetitive ventricular response was gradually prolonged, the number of consecutive QRS complexes was decreased, and clinical VT was finally eliminated. The overall success rate of RF ablation was 96% (22/23 patients), and no complications were observed. In conclusion, a repetitive ventricular response was frequently observed in idiopathic right VT. The changing pattern of repetitive ventricular response, slowly and/or disappearing was consistent with successful RF ablation.

Determinants of tachycardia recurrences after radiofrequency ablation of idiopathic ventricular tachycardia

Clinical and electrophysiologic parameters were analyzed to define the factors potentially related to tachycardia recurrences in 79 patients undergoing successful radiofrequency ablation of idiopathic right or left ventricular tachycardia. It was found that the endocardial activation time at the successful ablation site was the only independent predictor of tachycardia recurrences.

Entrance site of the slow conduction zone of verapamil-sensitive idiopathic left ventricular tachycardia: evidence supporting macroreentry in the Purkinje system

The entrance site of the slow conduction zone was identified by entrainment study in an 18 year-old woman with verapamil-sensitive idiopathic left ventricular tachycardia. Radiofrequency catheter ablation at this site eliminated the tachycardia. The entrance site was at a mid-septal location and was more than 2 cm away from the exit site. Electrophysiologic findings suggested macroreentry in the Purkinje system as the mechanism of idiopathic left ventricular tachycardia.

Demonstration of Purkinje potential during idiopathic left ventricular tachycardia: a marker for ablation site by transient entrainment

During VT of QRS morphology with right bundle branch block and left axis deviation in a patient without obvious structural heart disease, entrainment by pacing from the right ventricular outflow tract and high right atrium was demonstrated. During entrainment of VT, a Purkinje potential preceding the QRS and recorded at the left ventricular mid-septum was activated by orthodromic impulses in the reentry circuit. The interval between the Purkinje potential and the earliest left ventricular activation was decrementally prolonged with shortening of pacing cycle length. Radiofrequency energy was applied to this site, resulting in successful elimination of VT. Therefore, the Purkinje potential represented activation by an orthodromic wavefront in the reentry circuit, while the orthodromically distal site to this potential showed an area of slow conduction with decremental property.

Idiopathic monomorphic ventricular tachycardia: clinical outcome, electrophysiologic characteristics and long-term results of catheter ablation

Ventricular tachycardia (VT) without structural heart disease or any identifiable predisposing causes for arrhythmia is an uncommon but well-recognized clinical entity. The purpose of this study is to assess the results of catheter ablation therapy and the long-term outcome of patients with idiopathic monomorphic VT in a large patient group. Sixty-one consecutive patients (male/female=40/21; mean age 38+/-16 years) with idiopathic VT underwent electrophysiologic study and an attempt of catheter ablation therapy. The 'left VT' group included 31 patients with QRS morphology of right bundle branch block during VT suggestive of the VT originating from the left ventricle (LV), and the 'right VT' group consisted of 30 patients with QRS morphology of left bundle branch block with normal or right frontal axis deviation suggestive of VT arising from right ventricular outflow tract (RVOT). Idiopathic left VT has sustained VT during the clinical attacks, baseline electrophysiologic study or after isoproterenol infusion; it can be entrained by overdrive ventricular pacing, terminated by verapamil, but not by adenosine (except one case with VT focus at left ventricular free wall). Catheter ablation was successful in 22 (84%) of 26 patients, with recurrence rate of 9%. The successful ablation sites were located at LV inferior-apical septum (16 patients), mid-septum (three patients), high septum (two patients) and high anterior wall (one patient). In the right VT group, 20 (67%) of 30 patients presented clinically repetitive monomorphic VT. Most of the idiopathic right VT (22/30) required isoproterenol to facilitate induction of VT, and were sensitive to both verapamil and adenosine. Successful catheter ablation was achieved in 21 (84%) of 25 patients, with recurrence rate 19%. The successful ablation sites were located at RVOT-septum in 18 patients, and RVOT-free wall in three patients. During a mean follow-up period of 29.2+/-21.7 months (range 1-76 months) after hospital discharge, all patients were alive but one left VT case died of non-cardiovascular cause. We concluded that idiopathic left side and right side VTs have their distinct clinical, electrophysiologic and electropharmacological characteristics suggestive of different underlying mechanisms, and both have a benign prognosis. Furthermore, catheter ablation can be effective in eliminating idiopathic VT originating from the right ventricular outflow tract and left ventricle.

Value of simulated body surface potential maps as templates in localizing sites of ectopic activation for radiofrequency ablation

Body surface potential maps recorded during catheter pace mapping can facilitate the localization of the site of origin of ventricular tachycardia. In this study, we investigated the value of a realistic computer model of the human ventricular myocardium in generating body surface potential maps as templates for identifying sites of ectopic activation. Our model features an anatomically accurate geometry and an anisotropy due to transmural fibre rotation, that were reconstructed with a spatial resolution of 0.5 mm. It simulates the electrotonic interactions of cardiac cells by solving a nonlinear parabolic partial differential equation, but it behaves as a cellular automaton when the transmembrane potential exceeds the threshold value. We successfully validated our model by comparing the simulated activation sequences--described by isochronal maps, epicardial potential maps and body surface potential maps--with the measured sequences of epicardial and body surface maps reported in the literature. By systematically pacing the left ventricular and right ventricular endocardial surfaces in our ventricular model, we generated a database of 155 QRS-integral maps, which provides a high-resolution reference frame for localizing distinct endocardial pacing sites. This database promises to be a useful tool in improving the performance of catheter pace mapping used in combination with body surface potential mapping. Overall, the results demonstrate that our computer model of the human ventricular myocardium is well suited for complementing a database of QRS-integral maps obtained during clinical pace mapping and can help enhance the efficacy of the ablative treatment of ventricular arrhythmias.

Critical atrial site for ablation of pacing-induced atrial fibrillation in the normal dog heart

INTRODUCTION

Radiofrequency catheter ablation (RFA) has been used recently to treat atrial fibrillation (AF). The purpose of this study was to investigate a new approach to preventing AF by RFA.

METHODS AND RESULTS

In open chest, anesthetized dogs, AF (lasting > 30 sec) was induced after burst stimulation, and electrophysiologic parameters were recorded before and after RFA. In group 1 (9 dogs) we performed selective and combined slow and fast pathway RFA, whereas in group 2 (11 dogs) RFA was applied as a linear lesion at the mid-atrial septum between the inferior vena cava and the fossa ovalis. After ablation, the Wenckebach cycle length was significantly prolonged only in group 1 (194 +/- 23 vs 282 +/- 35 msec, P = 0.002), whereas the interval between the stimulus (S) artifact applied at the high right atrium to the His bundle (H) (SH interval) prolonged to the same extent in both groups (162 +/- 14 vs 146 +/- 45 msec, P = NS); group 1 due to an A-H prolongation whereas in group 2 it was due to an intra-atrial conduction delay. In group 1 AF still remained inducible, although with a longer mean R-R interval (215 +/- 16 vs 433 +/- 88 msec, P < 0.05). No instance of complete AV block developed. In group 2, sustained AF was noninducible in 10 dogs and its duration was markedly shorter in the remaining one (8 sec). Gross anatomy and histology did not reveal any damage inside of Koch's triangle, and particularly to the compact AV node.

CONCLUSION

These findings suggest that RFA at the mid-atrial septum prevents AF in the normal dog heart. This approach might also be successful in those clinical settings in which the atrial septum plays a critical role in the maintenance of sustained AF.

Ablation therapy for cardiac arrhythmias

Ablation has become an important and, in some cases, the first-line therapy for a number of tachyarrhythmias. The feasibility of treating arrhythmias with ablation was initially demonstrated with surgical ablation techniques. Recently, catheter ablation techniques have replaced the surgical approach in nearly all cases. Catheter ablation is highly effective for the Wolff-Parkinson-White syndrome, atrioventricular nodal reentry, and atrial ectopic tachycardia. It is effective for atrial flutter, although approximately one quarter of patients treated with catheter ablation continue to require therapy for concomitant atrial fibrillation. The surgical maze procedure has proved to be feasible for preventing atrial fibrillation. The risks and long-term efficacy of catheter ablation maze procedures for atrial fibrillation need to be defined. The efficacy of ablation for ventricular tachycardia varies with the type of tachycardia. Catheter ablation is very effective for the rare idiopathic ventricular tachycardias that occur in structurally normal hearts and for bundle-branch reentry ventricular tachycardia, which occurs most frequently in patients with dilated cardiomyopathy. When performed at an experienced center, surgical ablation is an excellent option for selected patients with ventricular tachycardia due to prior myocardial infarction who have a discrete aneurysm but otherwise well-preserved ventricular function. Catheter ablation shows promise for this arrhythmia, but it can be offered only to those patients who have relatively slow tachycardias that allow catheter mapping. Substantial advances in mapping and ablation technology will continue to occur, allowing nonpharmacologic control of cardiac arrhythmias to be achieved in an ever greater number of patients.

Management of patients with life-threatening ventricular tachyarrhythmias in the defibrillator era: the need to differentiate

Patients with a history of sustained ventricular tachyarrhythmias form an extremely inhomogeneous group with respect to presenting arrhythmia, underlying cardiac disease, and therefore, risk of dying suddenly. For subgroups such as ventricular tachycardia in the absence of underlying cardiac disease, radiofrequency catheter ablation offers cure. In others, implantation of a cardioverter defibrillator already appears to have gained the therapy of first choice, leaving only a secondary role to antiarrhythmic drugs. It must be emphasized however, that these new therapeutic strategies have their pros and cons like the older, seemingly out-fashioned approaches of noninvasively or invasively guided antiarrhythmic drug therapy or empiric amiodarone treatment. Until the advent of controlled randomized trials comparing the implantable cardioverter defibrillator (ICD) with the best other, usually medical form of treatment, physicians must continue to base their individual therapeutic decisions on circumstantial published and personal experience. In doing so, the recent achievements of catheter ablation and defibrillator implantation have definitely improved patient care, but have not made antiarrhythmic drugs jobless. With all the alternatives at hand, it remains a challenging task to weigh the benefits and risks of the various approaches against each other in an attempt to tailor the antiarrhythmic intervention to the very individual need of the patient.

Successful radiofrequency ablation of idiopathic left ventricular tachycardia at a site away from the tachycardia exit

OBJECTIVES

This study sought to assess the possibility of ablating verapamil-responsive idiopathic left ventricular tachycardia at a site distant from the tachycardia exit and thus to define the tachycardia circuit.

BACKGROUND

The nature of the reentry circuit in idiopathic left ventricular tachycardia is unclear. If the circuit is of considerable size, then it should be possible to ablate the tachycardia at a site distant from the exit site.

METHODS

Electrophysiologic studies and radiofrequency ablation were performed in 27 consecutive patients with verapamil-responsive idiopathic left ventricular tachycardia. In all 27 patients, the tachycardia exit site was defined as the site where the earliest Purkinje potential was recorded > or = 25 ms before the onset of the QRS complex during the tachycardia and where the pace map QRS complex resembled that during the tachycardia. A potential ablation site other than the exit site was then sought around the midseptum, proximal to the exit site. At such sites the tachycardia could be terminated transiently by pressure applied to the catheter tip, without induction of ventricular ectopic beats.

RESULTS

The potential ablation site, other than the tachycardia exit site, was identified in seven male patients (mean [+/-SD] age 31 +/- 12 years, range 13 to 52). Application of the radiofrequency current at this site resulted in termination of the tachycardia within 1 to 5 s (mean 2.9 +/- 1.6), and successful ablation of the tachycardia was achieved in all seven patients (success rate 100%, 95% exact confidence interval 0.5898 to 1). The mean distance between the ablation site and the tachycardia exit site was 3.1 +/- 0.7 cm (range 2.0 to 4.0). A presystolic Purkinje spike was recorded 14 +/- 5 ms (range 8 to 20) before the onset of the QRS complex during the tachycardia. During the follow-up period of 24 +/- 11 months (range 12 to 39), there was no recurrence of tachycardia in these seven patients.

CONCLUSIONS

Successful ablation of idiopathic left ventricular tachycardia can be achieved at sites away from the tachycardia exit site in some patients. This finding suggests that the reentry circuit is likely to be of considerable size, encompassing the middle, inferior and lower aspects of the left interventricular septum.

Use of an orthogonal electrode array to identify the successful ablation site in right ventricular outflow tract tachycardia

A novel approach to localize the origin of a right ventricular outflow tract tachycardia using an ablation catheter having an orthogonally oriented electrode array is described. Bipolar electrogram polarity reversal using minimally filtered (1-500 Hz) electrograms simultaneously acquired in two axes from the ablation catheter permitted accurate localization of the tachycardia focus. A single radiofrequency energy application at the site identified by this technique resulted in successful tachycardia ablation. This technique may facilitate mapping of any arrhythmia which can be modeled as arising from a point source.

Radiofrequency catheter ablation for idiopathic right ventricular tachycardia with special reference to morphological variation and long-term outcome

OBJECTIVE

To assess the long term outcome of radiofrequency (RF) catheter ablation for idiopathic ventricular tachycardia (VT) originating from the outflow tract of the right ventricle, with special reference to the morphological variation in the VT-QRS complexes.

PATIENTS

13 patients whose ventricular tachycardia was treated with RF ablation were followed up more than 18 months after RF ablation.

RESULTS

Endocardial mapping revealed the various extensions of ventricular tachycardia origin (from 0.5 x 0.5 cm to 2.0 x 2.0 cm) in which the earliest local electrogram was recorded during ventricular tachycardia. In all five tachycardias from a relatively wider origin (more than 0.5 x 0.5 cm) and in four of eight from a narrow origin (< 0.5 x 0.5 cm), subtle morphological variation in the VT-QRS complexes was observed. In tachycardias with morphological variation, the local electrogram at the tachycardia origin also showed concomitant variation in morphology and activation sequence. Ventricular tachycardia from a narrow site was eliminated by RF ablation to the confined site, but a larger number of RF applications was required in tachycardias from a wider origin. All 13 tachycardias were successfully ablated by RF current, and during the follow up period of 28.2 (SD 7.2) months, recurrence was observed in only one patient who had a wider origin.

CONCLUSIONS

Long term efficacy of RF ablation was excellent in idiopathic ventricular tachycardia originating from the outflow tract of the right ventricle. Subtle morphological variations were frequently observed in this type of ventricular tachycardia, and about half of them represented a relatively wider arrhythmogenic area.

Radiofrequency catheter ablation of idiopathic ventricular tachycardias in children

We performed radiofrequency catheter ablation of idiopathic ventricular tachycardia in six children. In four, the ventricular tachycardia originated in the left ventricle, in two it originated in the right ventricular outflow tract. In 5/6 (83%) the RF procedure was successful; there were no complications.

Mechanisms of idiopathic left ventricular tachycardia

Idiopathic left ventricular tachycardia (ILVT) differs from idiopathic right ventricular outflow tract (RVOT) tachycardia with respect to mechanism and pharmacologic sensitivity. ILVT can be categorized into three subgroups. The most prevalent form, verapamil-sensitive intrafascicular tachycardia, originates in the region of left posterior fascicle of the left bundle. This tachycardia is adenosine insensitive, demonstrates entrainment, and is thought to be due to reentry. The tachycardia is most often ablated in the region of the posteroinferior interventricular septum. A second type of ILVT is a form analogous to adenosine-sensitive RVOT tachycardia. This tachycardia appears to originate from deep within the interventricular septum and exits from the left side of the septum. This form of VT also responds to verapamil and is thought to be due to cAMP-mediated triggered activity. A third form of ILVT is propranolol sensitive. It is neither or initiated or terminated by programmed stimulation, does not terminate with verapamil, and is transiently suppressed by adenosine, responses consistent with an automatic mechanism. Recognition of the heterogeneity of ILVT and its unique characteristics should facilitate appropriate diagnosis and therapy in this group of patients.

Idiopathic left ventricular tachycardia with left and right bundle branch block configurations

INTRODUCTION

Idiopathic left ventricular tachycardia typically has a right bundle branch block configuration. The purpose of this case report is to demonstrate that idiopathic ventricular tachycardia arising in or near the left posterior fascicle also may have a left bundle branch block configuration.

METHODS AND RESULTS

A 27-year-old woman underwent an electrophysiologic procedure because of recurrent, verapamil-responsive, wide QRS complex tachycardia. Two types of ventricular tachycardia (cycle lengths 330 to 340 msec) were reproducibly inducible, one with a right bundle branch block configuration and left-axis deviation that had been documented clinically, and the other with a left bundle branch block configuration and axis of zero. A Purkinje potential recorded at the junction of the left ventricular mid-septum and inferior wall preceded the ventricular complex by 40 msec in both tachycardias. A single application of radiofrequency energy at this site successfully ablated both ventricular tachycardias.

CONCLUSION

The findings of this case report demonstrate that idiopathic ventricular tachycardia arising in or near the left posterior fascicle may have a left bundle branch block configuration.

Experience with radiofrequency catheter ablation of fascicular tachycardia

OBJECTIVE

To report experience with radiofrequency catheter ablation of fascicular tachycardia including two cases of the rare type of this arrhythmia which arises from the anterior fascicle of the left bundle branch.

DESIGN

Review of results of radiofrequency ablation in nine consecutive patients presenting with fascicular tachycardia.

SETTING

Regional cardiac centre.

INTERVENTION

Percutaneous radiofrequency catheter ablation, performed between 1993 and 1996.

RESULTS

Radiofrequency ablation was successful in both patients with tachycardia arising from the anterior fascicle and in six of the seven patients with tachycardia arising from the anterior fascicle and in six of the seven patients with tachycardias arising from the posterior fascicle. Notable differences in the "right bundle branch block" configuration of lead V1 during tachycardia between patients were observed. One patient with incessant tachycardia had marked impairment of ventricular function which returned to normal after ablation.

CONCLUSIONS

Radiofrequency ablation is effective in both anterior and posterior fascicular tachycardias. The arrhythmia can cause reversible impairment of ventricular function.

Morphological variation of nonreentrant idiopathic ventricular tachycardia originating from the right ventricular outflow tract and effect of radiofrequency lesion

RF catheter ablation was performed in 16 patients with nonreentrant idiopathic VT originating from the RVOT. All documented VT was monomorphic, but subtle morphological variation in the VT-QRS complex was observed in 10 (63%) of 16 patients. Through endocardial mapping, VT origin was determined within a narrow site (< 0.5 x 0.5 cm) in 4 of the 10 patients with the morphological variation. In the other 6 of 10 patients, the origin extended to an area of > 0.5 x 0.5 cm. In VT with morphological variation, the local electrogram at the site of VT origin also showed variation in morphology and activation sequence. For VT of narrow origin, RF application to the site eliminated the VT. However, in VT from a wide arrhythmogenic area, RF current had to be delivered to 3-7 distinct sites to cover the possible origin, and specific QRS configuration of VT and/or PVC was ablated at each of the earliest activation site. All but one VT were successfully ablated by RF current. Subtle morphological variation was frequent in this type of VT, and about half were associated with a wide arrhythmogenic area. Precise mapping and analysis of the efficacy of each RF application might be helpful to better understand the relationship between subtle changes of VT-QRS morphology and their origins.

Predictors for successful ablation of right- and left-sided idiopathic ventricular tachycardia

This study reports on predictors for successful radiofrequency (RF) ablation of idiopathic ventricular tachycardia (VT) in 48 patients--35 with right ventricular (RV) outflow tract and 13 with left ventricular VT. In RV outflow tract idiopathic VT, RF ablation was successful in 29 of 35 patients (83%). The following information allowed differentiation between patients with and without a successful RF ablation: > 1 induced VT morphology (O vs 3); presence of delta wave-like beginning of the QRS (2 vs 3) and > or = 11 of 12 leads showing a "match" between the clinical VT and the pacemap (28 vs 1). Endocardial activation times were not different between both groups (-15 +/- 18 vs -4 +/- 5 ms). In left ventricle idiopathic VT, RF ablation was successful in 12 of 13 patients (92%). In patients who underwent successful ablation, 1 VT morphology was induced and no delta wave-like beginning of the QRS was present; a correlation between clinical VT and the pacemap > or = 11 of 12 leads was found and the endocardial activation time preceded the QRS (range of -5 to -58 ms [mean -30 +/- 14]). Purkinje activity was observed in 5 of 7 patients with an idiopathic VT originating from the inferoposterior region but not from the inferoapical region of the left ventricle. Four patients (14%) with RV outflow tract idiopathic VT had recurrence during a mean follow-up of 2 to 50 months (mean 30 +/- 12). Thus, (1) in RV outflow tract idiopathic VT a good pacemap was more important than an early endocardial activation time; (2) an optimal pacemap as well as an early endocardial activation time were important predictors for successful ablation of the left ventricle idiopathic VT; (3) Purkinje activity was recorded in VTs arising in the inferoposterior region of the left ventricle; and (4) factors for unsuccessful ablation for idiopathic VT were > 1 induced VT morphology, a delta wave-like beginning of the QRS, and a VT/pacemap correlation < 11 of 12 leads. Idiopathic VT can be successfully ablated with both immediate and long-term success.

Ventricular tachycardia: pathophysiology and radiofrequency catheter ablation

Limitations of pharmacological therapy for VT have led to great interest in alternative nonpharmacological therapies. The appeal of a curative therapy for VT initially led to the search for operative techniques to identify and destroy the underlying substrate, and more recently, has resulted in the development of catheter techniques to achieve the same goal in the electrophysiology laboratory. Investigations into the pathophysiology of VT have resulted in the recognition that this arrhythmia reflects a mechanistically and anatomically heterogeneous set of disorders. Recent growth in our understanding of these distinctions has both led to, and resulted from, simultaneous advances in catheter ablation techniques. The clinical electrophysiology laboratory has served as a testing ground for theories derived from in vitro and animal experiments while also providing its own set of human experimental data regarding the pathophysiology and treatment of VT. As a result of this process, several distinct forms of VT that are amenable to catheter ablation have been characterized. This article will summarize current knowledge of the pathophysiology of various VT subtypes and of techniques for catheter mapping and ablation.

Adenosine-sensitive bundle branch reentry

INTRODUCTION

Bundle branch reentry is an uncommon mechanism for ventricular tachycardia. More infrequently, both fascicles of the left bundle may provide the substrate for such macroreentrant bundle branch circuits, so-called interfascicular reentry. The effect of adenosine on bundle branch reentrant mechanisms of tachycardia is unknown.

METHODS AND RESULTS

A 59-year-old man with no apparent structural heart disease and history of frequent symptomatic wide complex tachycardias was referred to our center for further electrophysiologic evaluation. During electrophysiologic study, a similar tachycardia was reproducibly initiated only during isoproterenol infusion, which had the characteristics of bundle branch reentry, possibly using a left interfascicular mechanism. Intravenous adenosine reproducibly terminated the tachycardia. Application of radiofrequency energy to the breakout site from the left posterior fascicle prevented subsequent tachycardia induction and rendered the patient free of spontaneous tachycardia during long-term follow-up.

CONCLUSIONS

Patients with ventricular tachycardia involving a bundle branch reentrant circuit may be sensitive to adenosine. These results suggest that adenosine may not only inhibit catecholamine-mediated triggered activity but also some catecholamine-mediated reentrant ventricular arrhythmias.

Therapy of "idiopathic" ventricular tachycardia

Idiopathic ventricular tachycardias occur in "normal" hearts and are generally benign arrhythmias. They can arise from either the left or right ventricle, and the origin is usually predictable from the surface ECG. These arrhythmias are produced by diverse mechanisms. When treatment is indicated, empiric pharmacotherapy can be successful. However, if drugs are not tolerated or fail, radiofrequency (RF) ablation may be indicated. During electrophysiologic study, arrhythmia mechanism can be determined, and pace and activation mapping can be used to localize the site of ventricular tachycardia origin to direct application of RF lesions. RF ablative therapy has been associated with high success rates.

Radiofrequency catheter ablation of idiopathic ventricular tachycardia originating in the anterior fascicle of the left bundle branch

INTRODUCTION

Idiopathic ventricular tachycardia (VT) originating in or close to the anterior fascicle of the left bundle is rare. A patient with no structural heart disease and VT with a right bundle branch block configuration and right-axis deviation underwent an electrophysiologic examination.

METHODS AND RESULTS

Both endocardial activation mapping during VT and pacemapping were performed via a transseptal approach to localize the site of origin of the VT. Endocardial recordings of the His bundle and the posterior and anterior fascicles of the left bundle branch revealed an origin of the VT in or close to the anterior fascicle. The Purkinje potential at that site preceded the QRS complex by 20 msec, with pacemapping showing an optimal match between the paced rhythm and the clinical VT. RF energy delivered at this site terminated the VT. A left anterior hemiblock appeared after RF ablation. Ten months later, the patient is free from recurrences of VT.

CONCLUSIONS

Idiopathic VT originating in or close to the anterior fascicle was cured by RF ablation. A Purkinje potential preceding the QRS during tachycardia and an optimal pacemap were used to guide RF ablation.

Radiofrequency catheter ablation of ventricular tachycardia in right ventricular cardiomyopathy: use of concealed entrainment to identify the slow conduction isthmus bounded by an aneurysm and the tricuspid annulus

Radiofrequency (RF) catheter ablation of ventricular tachycardia (VT) in patients with a right ventricular (RV) cardiomyopathy has only rarely been successful. This report demonstrates reentrant VT in the setting of RV cardiomyopathy in which the tricuspid valve annulus acted as one of the barriers of an isthmus of slow conduction, identified by the presence of entrainment with concealed fusion. The RF pulse was further targeted by analysis of the relationship between the postpacing interval with the tachycardia cycle length, and of the local activation time with the stimulation time. Long-term clinical follow-up has documented no recurrent VT.

Current role and future perspectives for radiofrequency catheter ablation of postmyocardial infarction ventricular tachycardia

The most common substrate for ventricular tachycardia (VT) is a postmyocardial infarction (MI) scar. Radiofrequency catheter ablation (RFCA) in post-MI VT faces clinical, electrophysiologic, anatomic, and methodologic difficulties not found in many other human tachycardias. The pathophysiologic understanding of post-MI VT is incomplete; this influences the process of selecting RFCA target sites, which is time consuming, demands catheter stability, and has low sensitivity and predictive value for VT interruption by RF current. Improving and simplifying the methodology of RFCA in post-MI VT is badly needed. We review the pathophysiology of post-MI VT from the data reported on endocardial, epicardial, and intramural ventricular mapping obtained either intraoperatively or in a Langendorff perfused set-up in hearts from transplanted patients. From these studies we conclude that (1) some post-MI VT cases are not amenable to RFCA (reentry around the scar, VT having a subepicardial or deep intramural substrate, or a wide, extensive, subendocardial intrascar area of slow conduction); and (2) searching for the endocardial exit is advantageous for selecting the RFCA targets. We also comment on a new self-reference mapping catheter that allows the recording of high gain, noise-free, unfiltered and filtered unipolar signals as well as unipolar pacing. Among the unresolved issues in these patients is the meaning of fast nonclinical VT induced after successful RFCA of the clinical VT, which may explain why a substantial number of these patients still receive an implantable cardioverter-defibrillator.

Radiofrequency catheter ablation of left ventricular tachycardia in the normal heart

BACKGROUND

Radiofrequency (RF) catheter ablation is a safe and effective cure for many forms of supraventricular tachycardia. Its efficacy in the cure of right ventricular outflow tract tachycardia, and some forms of left ventricular tachycardia in patients with left ventricular dysfunction, has also been shown. In contrast limited data are available to assess the role of RF catheter ablation in treating idiopathic left ventricular tachycardia (ILVT), an unusual form of tachycardia occurring in patients without demonstrable heart disease.

AIM

To examine the efficacy and safety of RF catheter ablation in patients with ILVT.

METHODS

Three patients without structural heart disease and with recurrent drug-refractory ILVT (right bundle branch block and left axis morphology) underwent electrophysiologic study (EPS) to initiate and localise the site of origin of their VT. RF catheter ablation of the VT focus was performed, with success being defined as failure to reinduce VT during incremental infusion of isoprenaline.

RESULTS

In all three patients VT was inducible by rapid right atrial pacing and/or programmed ventricular stimulation, and could be terminated by intravenous verapamil. RF catheter ablation was successful in all patients. The site of successful ablation was common to each patient and was localised to the infero-apical aspect of the left ventricular septum. It was characterised by the recording of the earliest presystolic "P' potential during both sinus rhythm and induced ILVT. No complications occurred during the procedure. During follow-up periods ranging from six to 12 months there were no symptomatic or documented episodes of recurrent ILVT.

CONCLUSIONS

We conclude that ILVT can be safely and effectively cured by RF catheter ablation.

Radiofrequency ablation for supraventricular and ventricular tachycardia in young patients

Radiofrequency ablation therapy was conducted in 86 consecutive children and young patients with a mean age of 14 +/- 3 years (range = 3-18). Fifty-two patients had Wolff-Parkinson-White syndrome, one had re-entry tachycardia incorporating a nodoventricular fiber, 22 had atrioventricular node re-entry tachycardia, two had atrial tachycardia and nine had idiopathic ventricular tachycardia. Radiofrequency ablation was successful in 50 of the 52 patients (96%) with Wolff-Parkinson-White syndrome and the one with nodoventricular fiber. Radiofrequency modification of the atrioventricular node using the inferior approach was successful in eliminating atrioventricular node re-entry tachycardia in 20 of the 22 patients (91%). Radiofrequency ablation in the two patients with atrial tachycardia was unsuccessful. Of the nine patients with idiopathic ventricular tachycardia, eight from the left ventricle and one from the right ventricular outflow tract, eight were successfully ablated (88%). Follow-up over a period ranging from 1 to 46 months (21 +/- 13) revealed a recurrence of tachycardia in seven patients; a late electrophysiological study in 38 patients revealed the induction of tachycardia in 11 patients (seven with accessory pathway-mediated tachycardia, three with atrioventricular node re-entry tachycardia and one with idiopathic ventricular tachycardia). All 11 patients were successfully ablated by a second trial. In conclusion, radiofrequency ablation therapy is effective and safe in pediatric patients with supraventricular and ventricular tachycardia and should be considered as the therapy of choice in this group of patients.

Catheter ablation for successful management of left posterior fascicular tachycardia: an approach guided by recording of fascicular potentials

OBJECTIVE

To assess whether catheter ablation of fascicular tachycardia can be facilitated by the recording of sharp deflections arising from the mid-septum---inferior apical septum of the left ventricle.

PATIENTS AND METHODS

Seven consecutive patients (mean age 29 (range 16-43) years) with ventricular tachycardia originating from the left posterior fascicle underwent electrophysiology study and detailed mapping of endocardial activation. Selection of ablation sites in the last five patients was based on the recording, during left posterior fascicular tachycardia and sinus rhythm, of a discrete potential preceding the earliest ventricular electrogram, which was thought to represent conduction through the posterior fascicle.

RESULTS

Patients were treated with low energy direct current or radiofrequency current ablation. The median fluoroscopy and procedure times were 23 (range 6-42) min and 110 (range 50-176) min, respectively. In a follow up period of 4 to 16 months, six patients were asymptomatic and one had minor symptoms. No patient had any change in intraventricular conduction. Similar potentials were also recorded from the left posterobasal septum in three of eight patients who underwent catheter ablation of left free wall accessory pathways.

CONCLUSION

Fascicular potentials can be reproducibly recorded in left posterior fascicular tachycardia and may serve as a reliable marker for successful ablation procedures. The relation of these potentials with the substrate of the tachycardia, however, remains obscure.

Radiofrequency ablation of idiopathic ventricular tachycardia

BACKGROUND

Radiofrequency ablation (RFA) has been shown to be very effective in the treatment of supraventricular tachycardias and has replaced surgical ablation. Only a few reports of RFA for idiopathic ventricular tachycardia (VT) have appeared in the literature during the last two years.

AIM

This paper presents our experience with RFA for idiopathic VT in 19 patients.

MATERIAL

The age range of patients was 22-60, with a mean of 37.9 years. Twelve out of 19 were females, two patients had cardiac failure due to almost incessant VT while the rest had normal left ventricular function. Twelve patients had VT arising from the right ventricle (RV); of these, nine were from the outflow tract, two from the RV apex, and one from the mid-anterior RV. Seven patients had VT arising from the left ventricle (LV); of these, five were from the inferobasal portion of the septum and two were from the anterolateral area.

METHODS

In all patients the diagnostic study and therapeutic RFA were combined in a single procedure. Pacemapping was used to guide the site of RFA in patients with VT arising from the RV. Local activation time (LAT), Purkinje potentials (PP) and pacemapping were used to guide RFA in those patients with LV septal tachycardias.

RESULTS

A total of 21 RF procedures were performed in 19 patients and 15 out of 19 patients had successful VT ablation. Ten of the 12 patients with RV tachycardias and all five patients with LV septal (left axis, right bundle branch block) tachycardias were successfully ablated. One patient with mid anterior RV VT required two attempts for successful ablation. One patient with RV outflow tract (RVOT) VT could not be ablated despite two attempts. Two patients with LV tachycardias arising from the antero-lateral LV could also not be ablated. During a follow up period of two to 16 months none of the successful patients had recurrence of VT. The number of RF applications was one to 27, mean 10; fluoroscopy times were four to 75, mean 26.9 minutes.

CONCLUSION

Idiopathic VT frequently arises from the RVOT and inferobasal portion of the LV septum. These tachycardias can be diagnosed on clinical and ECG grounds. RFA for idiopathic VT arising from these areas has a high success rate and this mode of treatment should be considered as a nonpharmacological curative treatment for symptomatic patients.

Ventricular tachycardia with narrow QRS duration, a right bundle branch block pattern, and right axis deviation abolished by catheter manipulation

A 25-year-old women underwent electrophysiologic evaluation for sustained normal QRS complex tachycardia with a pattern of right bundle branch block and right axis deviation. Ventricular tachycardia was diagnosed by demonstrating fusion beats, atrioventricular dissociation, and bundle of His potential activation, which began before the onset of each QRS complex. A single ventricular extrastimulus was capable of easily provoking the tachycardia. There was an inverse relationship between the coupling interval of the first extrastimulus and the interval of the first tachycardia beat, suggesting reentry as the mechanism. The tachycardia was unexpectedly abolished during catheter manipulation in the left ventricle and has never recurred during 1 year of follow-up evaluation. The tachycardia was thought to be an unusual form of interfascicular tachycardia or microreentrant fascicular tachycardia.

The present role of radiofrequency catheter ablation in the management of cardiac arrhythmias

Radiofrequency catheter ablation can be used to treat a variety of cardiac arrhythmias. Yet while the spectrum of arrhythmias amenable to catheter ablation continues to expand, the protocol for whether or not catheter ablation should be recommended for the management of an individual patient has not been firmly established. This article summarizes the experience of one medical center with radiofrequency catheter ablation. The varieties of arrhythmias that may be effectively treated with catheter ablation, the probability of success, and the attendant risks of these procedures in the series are presented. In addition, the future applications of catheter ablation to cardiac arrhythmias are discussed.

Bundle branch reentry tachycardia and possible sustained interfascicular reentry tachycardia with a shared unusual induction pattern

A case of bundle branch reentry tachycardia with an unusual induction pattern is presented. Unlike typical cases of this arrhythmia in which tachycardia is usually inducible with routine programmed ventricular stimulation and/or short-long sequences, tachycardia in this case was inducible only with atrial stimulation. It also arose spontaneously during atrial flutter and during isoproterenol administration. After ablation of the right bundle, possible interfascicular reentry tachycardia with a similar induction pattern was observed. This tachycardia was successfully ablated in the region of the posterior fascicle of the left bundle branch.

Diagnostic clues from the surface ECG to identify idiopathic (fascicular) ventricular tachycardia: correlation with electrophysiologic findings

INTRODUCTION

An RS interval > 100 msec in precordial leads has been recently described for the diagnosis of ventricular tachycardia (VT). The aim of this study was to assess the value of this criterion when applied to patients with right bundle branch block pattern, left-axis deviation (fascicular) VT sensitive to verapamil.

METHODS AND RESULTS

Eleven patients (mean age 31 +/- 11 years; range 16 to 51) had a mean heart rate of 164 +/- 37 beats/min (range 107 to 230) during VT. The QRS complex axis was -92 degrees +/- -15 degrees (range -80 to -115). The mean QRS duration was 121 +/- 9 msec (range 105 to 140). The mean RS interval was 67 +/- 9 msec (range 60 to 80). Fusion beats were present in 2 patients (18%), and AV dissociation confirmed by electrophysiologic study was found on ECG in 8 (73%) of 11. During tachycardia, the QRS-H' interval was 19 +/- 10 msec (range 10 to 30) in 6 of 11 patients. In seven patients, a fast, unique (or double) presystolic potential lasting 32 msec (range 12 to 40) occurring before the onset of the QRS complex was found at the site of origin of VT, localized in the inferior apical left ventricular septum. In all cases, VT was successfully treated by catheter ablation.

CONCLUSION

A wide QRS complex tachycardia with right bundle branch block and left-axis deviation sensitive to verapamil observed in a young patient without structural heart disease should not be confused with supraventricular tachycardia with aberrancy but rather suggests the presence of fascicular VT. As opposed to VT associated with structural heart disease, the RS interval is < 80 msec in all precordial leads in all cases. Independent of this parameter, AV dissociation detectable on surface ECG has a sensitivity of 73%, which increases to 82% in the presence of fusion beats.

Radiofrequency ablation of idiopathic left anterior fascicular tachycardia

INTRODUCTION

A 45-year-old man with idiopathic ventricular tachycardia (VT) having a right bundle branch block configuration with right-axis deviation underwent an electrophysiologic test.

METHODS AND RESULTS

Mapping demonstrated a site on the anterobasal wall of the left ventricle where there was an excellent pace map and an endocardial activation time of -20 msec, but radiofrequency catheter ablation at this site was unsuccessful. At a nearby site, a presumed Purkinje potential preceded the by 30 msec during VT and sinus rhythm, and catheter ablation was effective despite a poor pace map and an endocardial ventricular activation time of zero.

CONCLUSION

Idiopathic VT with a right bundle branch configuration and right-axis deviation may originate in the area of the left anterior fascicle. A potential presumed to represent a Purkinje potential may be more helpful than endocardial ventricular activation mapping or pace mapping in guiding ablation of this type of VT.

New horizons in catheter ablation

Catheter ablation has evolved into the dominant therapeutic modality in the treatment of a variety of arrhythmias, particularly supraventricular arrhythmias with the mechanisms of atrioventricular (AV) nodal reentry and AV reciprocating tachycardia via an accessory pathway. The mode of catheter ablation used in the great majority of cases is radiofrequency (RF) catheter ablation. This technology is well-suited for the above arrhythmias because the targets and the RF lesions are both small and discrete. Using temperature monitoring may improve the outcome of these procedures by decreasing procedure time and incidence of coagulum formation on the catheter after a sudden rise in electrical impedance. New RF catheter designs and new modalities of creating catheter-induced focal myocardial injury will allow operators to have improved success with the ablation of less approachable arrhythmias, including atrial flutter and reentrant ventricular tachycardia. Studies are currently underway to create a catheter based "maze" procedure for the treatment of atrial fibrillation. As techniques and technologies evolve, a greater proportion of patients with symptomatic or threatening arrhythmias may be approached with catheter ablation as a curative or palliative procedure.

Radiofrequency catheter ablation of multiple morphologies of ventricular tachycardia by targeting a single region of the left ventricle

INTRODUCTION

As treatment options for ventricular tachycardia (VT) continue to evolve, the use of radiofrequency catheter ablation is rapidly expanding. However, in the presence of multiple morphologies of VT, achieving successful results may seem less likely. We report two patients with multiple morphologies of VT who underwent successful radiofrequency ablation by application of radiofrequency energy to a single region in the left ventricle.

METHODS AND RESULTS

Two patients, each without any apparent cardiac dysfunction and a history of documented VT, were referred to our institution for further management. They underwent an electrophysiologic study and were found to have easily inducible VT, of three morphologies in one patient and two in the other. Using a transaortic approach, left ventricular mapping was performed for detecting a site with presystolic potentials, earliest ventricular activation, or both. Application of radiofrequency energy to a single area in the left ventricle resulted in the elimination of all previously inducible VT in each patient.

CONCLUSION

VTs with distinctly different morphologies can occur in patients with no detectable structural heart disease. These VT circuits may share a common pathway and, therefore, may readily be amenable to therapy with radiofrequency catheter ablation.

Future ablation concepts of tachyarrhythmias

Application of radiofrequency energy to arrhythmogenic substrates after careful cardiac mapping could ensure a high success rate in eliminating certain types of tachyarrhythmias. Future studies of catheter ablation will focus on how to improve ablation efficacy and achieve a better result in various types of tachyarrhythmias. More information about the arrhythmogenic mechanisms will be provided to improve the knowledge of diagnostic and interventional electrophysiology.