(Circulation. 1996;94:376-383.)
© 1996 American Heart Association, Inc.
Articles |
Radiofrequency Current Catheter Ablation of Accessory Atrioventricular Pathways in Ebstein's Anomaly
the Departments of Cardiology, St Georg Hospital (R.C., M.S., K.-H.K.) and University Hospital Eppendorf (C.W., M.A., D.H.K., T.H.), Hamburg, Germany.
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Abstract |
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Background In patients with Ebstein's anomaly, localization of accessory pathways (APs) may be impeded by abnormal local electrograms recorded along the atrialized right ventricle and by the presence of multiple APs. The impact of these factors on radiofrequency (RF) current catheter ablation of APs has not been evaluated yet.
Methods and Results Twenty-one patients with Ebstein's anomaly and reentrant atrioventricular tachycardias underwent electrophysiological evaluation and subsequent attempts at RF catheter ablation. Thirty-four right-sided APs were found, with 30 located along the atrialized ventricle. Local electrograms in this region were normal in 10 patients but fragmented in 11. Fragmented electrograms prevented the clear distinction between atrial and ventricular activation potentials as well as the identification of AP potentials. Right coronary artery mapping was performed in 7 patients. Abolition of all 26 APs was achieved in the 10 patients with normal local electrograms and in 6 of 11 patients with abnormal electrograms. Right coronary artery mapping allowed AP localization and ablation in 5 patients. In the 5 patients with abnormal electrograms and a total of 8 APs, 6 APs could not be ablated. Unsuccessfully treated patients received antiarrhythmic drugs. During 22±12 months of follow-up, 5 patients had clinical recurrences, including 4 who had undergone a successful RF procedure.
Conclusions In patients with Ebstein's anomaly and reentrant atrioventricular tachycardias, factors likely to account for failure of RF catheter ablation include an AP located along the atrialized right ventricle and the abnormal morphology of endocardial activation potentials generated in this region.
Key Words: catheter ablation • Ebstein's anomaly • tachycardia
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Introduction |
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Paroxysmal atrioventricular reentrant tachycardia has been reported in 25% to 30% of patients with Ebstein's anomaly, with ventricular preexcitation present in 5% to 25% of surface ECGs.1 2 3 4 5 6 7 8 9 10 11 12 13 14 Accessory atrioventricular connections usually are located on the same side as the malformed valve, and in up to 50% of patients multiple accessory pathways (APs) have been observed.13 15
Catheter ablation with the use of radiofrequency (RF) energy to interrupt an accessory atrioventricular connection is increasingly being used as the primary therapeutic option for patients with paroxysmal reentrant atrioventricular tachycardias.16 17 18 19 20 21 The efficacy of this approach in patients with Ebstein's anomaly has not been assessed yet. In these patients, precise AP localization may be impaired by the presence of multiple pathways and by their usual location along the dysplastic tricuspid annulus, a region where abnormal endocardial electrograms have been reported to originate.12 The present study reports our experience in a consecutive series of patients referred for RF current ablation of an AP in the presence of Ebstein's anomaly, with particular emphasis on techniques for optimizing the mapping and ablation strategy in these patients.
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Methods |
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Patients
Between May 1987 and May 1995, 1011 consecutive patients underwent RF current catheter ablation of an AP at our institutions. Of these, 21 patients had reentrant atrioventricular tachycardias on the basis of at least one accessory atrioventricular connection associated with Ebstein's anomaly of the tricuspid valve. A total of 13 patients were female and 8 were male; the mean age was 28±14 years (range, 1.5 to 54.0 years). All patients had experienced symptomatic spontaneous tachyarrhythmias. Symptoms included disabling palpitations, nausea, chest pain, dizziness, and presyncope; syncope was reported in 6 patients. In 1 patient, the tachycardia was associated with cyanosis and deterioration of hemodynamic balance; it had become incessant in the weeks preceding the therapeutic intervention. The duration of symptoms ranged from birth (in 1 case) to almost 30 years. Before ablative therapy, all patients had undergone drug trials with a median of 4 antiarrhythmic agents (range, 1 to 7); in 1 patient, 2 previous surgical interventions performed at another institution had failed to divide a manifest right posterior AP. The clinically documented arrhythmias were atrioventricular reentrant tachycardias with either narrow and/or wide QRS complexes in all patients; in 4 patients, atrial fibrillation also had been documented.
Echocardiography
Ebstein's anomaly was defined as an apical displacement of the attachment of the septal tricuspid valve leaflet from the right atrioventricular annulus that exceeded 1.2 cm in length.22 The diagnosis was established by two-dimensional transthoracic echocardiography. The extent of septal leaflet displacement, the area of the atrialized right ventricle, and the proximal septal wall thickness were measured in apical echocardiographic views and normalized for body surface area. The extent of septal leaflet displacement was defined as the distance between the septal annular prominence and the site where the valve leaflet emerged from the septal ventricular wall. The area of the atrialized ventricle was measured during late systole, with its superior border defined by the ideal line connecting the septal and posterior annular prominences and its inferior border by the septal and posterior leaflet attachments (Fig 1
). Septal thickness was defined as the maximum thickness of the septal tract between the annular prominence and the attachment of the tricuspid valve leaflet. The extent of tricuspid regurgitation was assessed semiquantitatively by means of Doppler flow imaging.23
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Electrophysiological Procedure
All patients were informed about the investigational nature of the catheter ablation procedure and gave their written consent. The protocol had been approved by the ethics committees at our institutions. The patients were studied after all cardioactive drugs had been discontinued for at least five half-lives.
During electrophysiological study, a standard mapping procedure was used as described in detail elsewhere.19 In brief, two standard-production 6F quadripolar catheters (5-mm interelectrode distance), introduced through the femoral vein, were advanced under fluoroscopic guidance to the right atrium and the right ventricular apex, respectively. A 6F decapolar catheter (2-mm interelectrode distance) was placed at the bundle of His. In all patients undergoing the standard procedure, a 6F catheter with three groups of four circumferential electrodes arranged in an orthogonal configuration (Jackman-type catheter; Cordis Webster, Inc) could be positioned via the left subclavian vein into the coronary sinus for coronary sinus mapping. For mapping of the tricuspid annulus and right ventricle, and eventual ablation of the AP, a steerable 7F quadripolar catheter with 2-mm interelectrode distance and a tip electrode of 4-mm length (Cordis Webster, Inc, or Dr Osypka GmbH) introduced by way of the femoral vein was used. The atrioventricular annuli were mapped during atrioventricular reentrant tachycardia or ventricular pacing and during sinus rhythm or atrial pacing.
Programmed electrical stimulation with stimuli of 0.5-ms duration at twice diastolic threshold was performed with the ERA-S-HIS stimulator (Biotronik GmbH). Six surface ECG leads and at least five endocardial leads were simultaneously recorded on a 16-channel recorder (Mingograph, Siemens AG) at a paper speed of 100 mm/s. Local electrograms were filtered at 50 to 500 Hz and amplified at a gain of 20 mm/mV.
The presence and participation of an accessory connection as a critical component in the reentrant tachycardia circuit were defined according to conventional criteria.24
Criteria to locate the target site for RF current application were (1) for manifest APs, the site of earliest ventricular activation relative to the onset of the delta wave-possibly in the presence of a presumed AP activation potential preceding the QRS complex-and/or an atrium-to-ventricle interval 
40 ms during sinus rhythm,25 atrial pacing, or antidromic tachycardia, and (2) for both manifest and concealed APs, the site of earliest atrial retrograde activation-possibly in the presence of a presumed AP activation potential-and/or a ventricle-to-atrium activation interval 40 ms during orthodromic tachycardia, ventricular pacing, or antidromic tachycardia when the retrograde limb of the reentrant circuit was due to a second AP.
Local electrograms recorded at the atrioventricular annular region were considered abnormal if, during sinus rhythm, they consisted of continuous fragmented electrical activity with multiple spikes lasting for 
50 ms. These abnormal electrograms were commonly observed during mapping of the tricuspid annulus in the posteroseptal to posterolateral region and resumed their normal configuration as the catheter was moved out of the area of the atrialized right ventricle toward the lateral (Fig 2), and further to the anteroseptal annular region. A progressive change from fragmented to normal activation potentials also was observed when the mapping catheter was advanced from the annulus toward the ventricular apex (Fig 3); the distance from the tricuspid annulus over which this phenomenon occurred varied among patients from 
2.0 to 3.5 cm. Whenever mapping of the tricuspid annulus encountered such abnormal electrograms, timed extrastimuli were delivered from the high right atrium to dissociate the atrial from the ventricular component. During sinus rhythm, the atrial extrastimuli were timed early in an attempt to find the AP refractory and thus discriminate the earliest ventricular activation component during preexcitation (Fig 4). During tachycardia with preexcited retrograde atrial activation, atrial extrastimuli were timed late to dissociate the local atrial electrogram and identify its earliest activation along the atrioventricular annulus.
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, onset of delta wave.
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Right coronary artery mapping
If the precise localization of an AP by means of conventional recording and pacing techniques was not possible, mapping of the right coronary artery was attempted. After full coagulation with intravenous heparin, right coronary angiography was performed with a 7F Judkins catheter. If the anatomic course of the artery was confined to the atrioventricular groove, a 2F angioplasty catheter provided with four poles (Corotrax; Dr Osypka GmbH; 3-mm center-to-center interelectrode distance) was advanced into the right coronary artery to the region of the crux of the heart with the use of an over-the-wire or on-the-wire system. Mapping for AP potentials and for sites of earliest antegrade ventricular activation or earliest retrograde atrial activation was performed while the catheter was slowly withdrawn from the crux of the heart to the mouth of the coronary artery. The intracardiac mapping catheter was positioned at the endocardial site that best matched the anatomic location of, and the electrogram configuration recorded from, the epicardial electrode pair identifying AP location (Fig 5a and 5b); when these criteria were met, RF current was delivered through the tip of the endocardial mapping catheter.
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Ablation
Electrocoagulation was attempted with the use of a 500-kHz continuous-wave current generator (HAT 200; Dr Osypka GmbH). RF current was delivered in a unipolar fashion primarily during atrial pacing to maintain maximal preexcitation, or during atrioventricular reentrant tachycardia.
During the procedure, patients were sedated, if necessary, with diazepam (5 to 15 mg) or were anesthetized with fentanyl (0.1 to 0.5 mg). After catheter positioning, a bolus of 100 U/kg heparin was given intravenously, followed by a second injection of 5000 U after 4 hours.
For APs in which transient or permanent conduction block was achieved, the anatomic location was classified in the 30° left anterior oblique fluoroscopic view according to the catheter position at the site of a successful pulse delivery. In cases of failure, the anatomic location was assumed to be the site of earliest atrial activation for concealed APs and the site of earliest ventricular activation for manifest APs.
An electrophysiological evaluation was performed 30 to 60 minutes after accessory fiber ablation. It consisted of right atrial and ventricular stimulation with use of the extrastimulus technique as well as incremental pacing to exclude the presence of another AP and to determine the postablation conduction properties of the AV node–His bundle system.
Statistics
Data are presented as mean±1 SD values where appropriate. In cases of a skewed, non-gaussian distribution of measured parameters, the median value is given instead of the mean. Nominal data were analyzed by use of the 
2 test.
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Results |
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Echocardiography
In all patients, an apical displacement of the attachment of the septal tricuspid valve leaflet was seen, with no apparent displacement of the contralateral valve attachment. The median extent of the displacement was 2.5 cm (range, 1.6 to 4.6 cm). Tricuspid valve regurgitation was diagnosed in all patients by Doppler echocardiography; grade I regurgitation was present in 11 patients, grade II in 7, and grade III in 3. The degree of valve regurgitation did not correlate with the extent of leaflet displacement or with the clinical status. The median septal wall thickness along the atrialized right ventricle was at 6.5 mm (range, 5.2 to 8.5 mm) within the normal range (5 to 11 mm).22
The median ratio of the areas of the atrialized right ventricle and the cross-sectional right ventricular cavity was 0.31 (range, 0.12 to 0.43). The extent of septal leaflet displacement and the area of atrialized right ventricle, normalized for body surface area, were 15.5±5.6 mm/m2 and 7.8±3.7 cm2/m2, respectively.
Angiography
Right coronary artery mapping was deemed necessary in 9 patients. In 7 of them, coronary angiography showed a dominant coronary vessel lying in the right atrioventricular groove and branching at the crux of the heart into a posteroseptal and a left posterolateral component. An adverse vessel course (not confined to the atrioventricular groove) and anatomy (small vessel) was found in the remaining 2 patients; coronary artery mapping was therefore not performed in these cases.
Anatomic Distribution of APs
Thirty-four accessory atrioventricular connections were found in the 21 patients. All APs were located along the tricuspid annulus (Fig 6); 9 were posteroseptal (6 manifest and 3 concealed), 10 posterior (9 manifest and 1 concealed), 10 posterolateral (7 manifest and 3 concealed), 2 anteroseptal (1 manifest and 1 concealed), 1 lateral (manifest), 1 anterolateral (concealed), and 1 midseptal (manifest). Ten patients had 1 AP, 10 had 2 APs, and 1 had 4 APs.
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APs associated with Ebstein's anomaly accounted for 8.9% of a total of 382 right-sided APs encountered at our institutions.
Ablation Data
Thirty-four ablation sessions were performed. Permanent abolition of all 26 APs was achieved in 16 patients (76%; median of 2 APs per patient), requiring 3 sessions in 1 patient, 2 in 8 patients, and 1 in the other 7. A median of 9 pulses (range, 1 to 44) per fiber were required for ablation; the median cumulative energy per fiber was 8712 J (range, 1206 to 58 354 J). In these patients, cumulative session duration was 7.2±5.5 hours and median fluoroscopy time was 70.7 minutes (range, 18 to 300 minutes).
In 5 patients with a total of 8 APs (median of 2 APs per patient), 35±20 RF current applications failed to ablate 6 APs (2 posteroseptal, 3 posterior, and 1 posterolateral) during 8 sessions. Thus, 28 (82%) of the 34 APs were ablated.
While this study was performed, 332 (95%) of 348 right-sided APs in 329 patients without Ebstein's anomaly were ablated at our institutions (P=.004 versus APs associated with Ebstein's anomaly). No acute or chronic procedure-related complications were observed in either group of patients.
Electrophysiological Findings
Surface ECG
Nineteen patients exhibited ventricular preexcitation. A right bundle-branch block configuration was observed in the 2 patients without preexcitation during sinus rhythm. After ablation, a right bundle-branch block pattern was observed in 15 patients in whom ablation of all APs was achieved; the mean QRS duration in these patients was 118±22 ms after ablation (133±21 ms before ablation).
Thirty-eight clinical tachycardias (cycle length, 347±63 ms) were induced by atrial or ventricular extrastimuli or by rapid atrial or ventricular pacing in 19 patients during the electrophysiological procedure. Of these, 34 were orthodromic (10 using more than 1 pathway in 5 patients) and 4 antidromic (all using a second AP in the retrograde limb). In 2 patients with a single manifest AP, no atrioventricular tachycardia was inducible, and ablation was attempted during sinus rhythm.
Findings Relative to Local Electrogram Characteristics
Normal electrograms
Normal endocardial electrograms with distinct atrial and ventricular deflections at all sites along the tricuspid annulus were recorded in 10 patients; 12 (92%; 11 manifest, 1 concealed) of the 14 APs found in these patients were located in the region extending from the midseptal to the posterolateral tricuspid annulus.
Permanent abolition of all APs was achieved in these patients. At sites of successful RF current application, the local electrogram revealed a presumed AP potential during sinus rhythm (8 cases) or orthodromic tachycardia (6 cases). During orthodromic tachycardia in 8 of the 10 patients, fragmented and delayed local ventricular activation was observed along the atrialized right ventricle.
Abnormal electrograms
In 11 patients (53%), local activation potentials recorded along the atrialized ventricle were abnormal. Located in this area were 18 (12 manifest, 6 concealed) of the 20 APs found in these patients.
Permanent abolition of all 12 APs (10 of them located along the atrialized ventricle) was achieved in 6 of these patients. They underwent a median of 2 sessions (range, 1 to 3; 25±15 RF current pulses per fiber). To locate the APs, atrial stimulation techniques sufficed in 1 patient, while right coronary artery mapping was additionally used in the remaining 5 patients. Right coronary artery mapping was used in these 5 patients only in the session associated with a successful outcome.
At all successful ablation sites along the atrialized right ventricle, the presence of the AP did not produce specific electrogram changes compared with adjacent sites; a presumed AP potential could be recorded in 7 of 12 successful sites. In 2 patients, the site of earliest retrograde atrial activation was recorded over 1 cm in the posteroseptal region. Multiple RF current applications delivered in that area abolished AP conduction in both cases, although in 1 of them AP conduction recurred after 1 month, requiring a second procedure for definitive interruption. Timed delivery of atrial extrastimuli allowed the identification of the earliest retrograde atrial or antegrade ventricular potential in all 11 patients, although in 5 of them 6 APs could not be ablated at the site of shortest V-A interval.
Failure to ablate 6 of 8 APs all located along the atrialized right ventricle was encountered in the other 5 patients with abnormal electrograms. Right coronary artery mapping was not performed in the first patient and could not be performed in 2 patients because of an adverse vessel course. The technique was performed in the 2 remaining patients, each with a concealed AP, but did not allow precise localization of the respective AP. One patient had a suspected posteroseptal AP, but because of low-amplitude epicardial atrial potentials (A/V ratio=0.06), it was not possible to precisely identify the corresponding endocardial site of earliest retrograde atrial activation during orthodromic tachycardia or ventricular pacing. In the other patient, fragmented electrograms similar to those recorded endocardially were recorded from the epicardium in the posterolateral area (Fig 7); despite the ability to dissociate the atrial from the ventricular electrogram component by timed atrial extrastimuli, the site of earliest retrograde atrial activation could not be identified precisely in this patient, and repeat pulse delivery at sites of early activation in the posterolateral region failed to abolish conduction over the accessory pathway.
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Right coronary artery mapping
In 3 of 7 patients in whom the procedure was performed, right coronary artery mapping revealed distinct atrial and ventricular activation potentials throughout the course of the artery, including the annular region along the atrialized right ventricle. In 2 other patients, local epicardial electrograms were characterized by low-amplitude atrial potentials (A/V ratios of 0.06 and 0.07, respectively); this finding was associated with the inability to precisely identify at the corresponding endocardial site the site of earliest retrograde atrial activation during orthodromic tachycardia or ventricular pacing. In another patient, fragmented local electrograms preventing a clear distinction between atrial and ventricular activation potentials as well as the identification of an AP potential were recorded similar to what was observed at the corresponding endocardial aspect.
Right coronary artery mapping during incessant orthodromic reentrant tachycardia in the remaining patient revealed at the eventual sites of ablation a small ventricular activation potential (A/V ratio=3.4) recorded from the distal electrode pair, whereas no ventricular activation was recorded from the proximal electrode pair. Two RF current pulses delivered at the site of earliest retrograde endocardial activation in the posteroseptal region did not interrupt the tachycardia but led to a different local activation sequence, suggestive of a second AP; this was abolished with just one RF pulse after withdrawal of the right coronary artery mapping catheter for 5 mm and current delivery from the endocardial site between the distal and the proximal epicardial electrode pairs.
Extent of atrialized right ventricle and local electrogram characteristics
The presence of abnormal potentials recorded from the atrialized right ventricle was not correlated with the normalized extent of septal leaflet valve displacement, the area of atrialized right ventricle, and the septal wall thickness. Also, the degree of septal wall thickness did not correlate with the extent of septal leaflet displacement.
Follow-up
The mean follow-up was 22±12 months. During this time, 12 patients (with a total of 22 APs) of the 16 who had undergone successful RF current ablation had no symptoms, no preexcitation pattern on the surface ECG, and did not require antiarrhythmic drug treatment. Four patients experienced paroxysmal palpitations on the basis of recurrent conduction over a manifest AP each. With all 4 APs located along the atrialized right ventricle, these patients are presently scheduled for a repeat ablation procedure.
Of the 5 patients in whom the ablation procedure failed to abolish AP conduction, 1 has been asymptomatic during 19 months of follow-up, 3 have experienced mild symptoms well controlled by class Ic antiarrhythmic drugs, and 1 reported frequent palpitations despite flecainide treatment and is scheduled for a repeat procedure.
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Discussion |
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Patients with Ebstein's anomaly of the tricuspid valve have a high incidence of atrioventricular reentrant tachycardias secondary to one or more APs.13 15 The incidence of APs associated with this disease among all clinically relevant accessory atrioventricular connections is low; it was 2.1% in the whole series investigated at our institutions and 8.9% among right-sided APs.
Although confirming the feasibility of RF catheter ablation as a strategy to abolish AP conduction, the results of the present study underline its reduced efficacy in patients with Ebstein's anomaly. The success rates relative to patients and APs were 76% (16 of 21 patients) and 82% (28 of 34 APs), respectively. This compares with a 95% success rate for right-sided APs in patients without Ebstein's anomaly treated at our institutions, which is in accordance with results reported for the general population of patients with APs.16 17 18 19 20 21 Also, successful treatment in patients with Ebstein's anomaly is associated with an increased risk of recurrence during follow-up,26 as documented by the 25% (4 of 16 patients) recurrence rate in the present series.
Factors Adversely Influencing Ablation of APs in Ebstein's Anomaly
In 11 (52%) of 21 patients, the clinical tachycardia was associated with multiple APs, a finding consistent with previous reports.12 13 14 All APs were located along the tricuspid annulus. In addition, the vast majority (30 of 34) of APs were located along the atrialized right ventricle; abnormal activation potentials generated at the endocardial aspect in this region and extending to the atrioventricular annulus were observed in 11 patients (52%). Such potentials prevented the identification of AP activation potentials and of sites of earliest activation during antegrade or retrograde AP conduction. Also, a complex geometry of the AP cannot be excluded, as suggested by the ability to record the earliest retrograde atrial preexcitation over a distance of 1 cm in 2 patients.
Failure to ablate at least one AP was encountered in 5 patients (24%). The relatively good clinical outcome in failed procedures (1 patient asymptomatic, 3 controlled with drugs) suggests a potential influence of late effects brought on by cumulative energy on the anatomic substrate.
Abnormal Endocardial Activation Potentials
The relation between fractionation and local conduction delay is reflected in some specific observations. In one patient during orthodromic tachycardia, the retrograde atrial deflection occurred before the offset of the ventricular activation potential, a finding consistent with markedly impaired local ventricular conduction causing regions of the atrialized ventricle proximal to the lower insertion of the AP to be activated later than the retrogradely invaded atrium.
With regard to a potential target site for RF current delivery, fractionated activation potentials impair (1) the definite recording of an AP activation potential, (2) the determination of the site of earliest antegrade ventricular activation, and (3) the identification of the site of earliest retrograde atrial activation during orthodromic tachycardia. In addition, fractionated ventricular potentials occasionally may exhibit late components of high amplitude that mimic retrograde atrial activation during tachycardia. To distinguish between atrial and ventricular activation, timed atrial extrastimuli were systematically delivered during orthodromic tachycardia to transiently dissociate the two components. This technique proved feasible in all cases, but it failed to provide a precise localization of the upper AP insertion in 5; instability of catheter-tissue contact after an extrastimulus, particularly during tachycardia, may explain the inefficacy of the technique in these patients.
Right coronary artery mapping
Right coronary artery mapping proved to be a useful technique to improve the resolution of electrical activation recorded at the atrioventricular annulus along the atrialized ventricle. The right coronary artery was confined to the atrioventricular groove up to the crux of the heart in 7 (78%) of 9 patients and allowed advancement of the epicardial mapping catheter to the posteroseptal region in all cases. Atrial and ventricular activation potential amplitudes recorded at the epicardial aspect of the posteroseptal to posterolateral region revealed a variable pattern in these patients. The epicardial atrial or ventricular potentials were of low amplitude in 3 (43%) of the 7 patients; in 1 of them, the atrial potential could not be distinguished from the isoelectric baseline. These findings probably reflect an abnormal anatomic relationship of atrial and ventricular tissue at the tricuspid annulus. The low amplitude of epicardial and endocardial atrial activation potentials accounted for the inability to identify the site of earliest retrograde atrial activation in 2 patients with a concealed accessory fiber; in 1 case, RF ablation attempts failed to interrupt conduction over the pathway. In the case with low-amplitude ventricular potentials, distinguished atrial potentials recorded in the posteroseptal region were crucial to identify and ablate 2 concealed APs in the same region. As a whole, the electrograms recorded by means of right coronary artery mapping were relevant to localize and ablate 1 or more APs in 5 (71%) of 7 patients.
Relation Between Local Electrogram Characteristics and the Anatomic Extent of the Atrialized Right Ventricle
The presence of abnormal electrograms along the atrialized right ventricle could not be predicted on the basis of either the extent of displacement of the septal tricuspid leaflet, the area of atrialized ventricle, or septal wall thickness. This finding suggests that the extent of structural abnormalities in Ebstein's anomaly does not help to predict the type of local electrograms likely be recorded in the individual patient.
Study Limitations
In this study, RF current pulses were not delivered with the use of the temperature-controlled mode; therefore, it is not possible to systematically assess the role of catheter-tissue contact as a variable affecting the outcome of the ablation attempts. Also, the recording of unipolar electrograms was not used as a means to identify AP sites along the atrialized right ventricle. Also, we did not perform a systematic use of long guiding sheaths; therefore, the benefit of this technique to minimize failures in this set of APs cannot be assessed.
Conclusions
Data from the present study show that in patients with Ebstein's anomaly, RF current catheter ablation represents a therapeutic option to cure atrioventricular tachycardias on the basis of an accessory atrioventricular connection. In this subset of patients, the success rate is lower than in the general population. Factors likely to account for the reduced success rate include AP locations most commonly along the atrialized right ventricle, a complex geometry of the AP, and the abnormal morphology of endocardial activation potentials generated in this region. Use of the atrial extrastimulus technique during orthodromic tachycardia proved helpful to dissociate atrial from ventricular fragmented potentials recorded from the mapping catheter.
Right coronary artery mapping may add further information in patients in whom AP localization is not possible by means of endocardial mapping techniques.
Because of its safety, RF ablation should be the first choice for a curative therapy in patients with Ebstein's anomaly who do not present with hemodynamic impairment. Compared with surgery,27 the role of RF ablation for the cure of AP-related tachycardias in patients who require correction of associated cardiac defects remains to be established.
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Acknowledgments |
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The authors are grateful to Anton E. Becker, MD, for supervising the manuscript. Wilhelm Kaltenbrunner, MD, Robert Hatala, MD, Zaman Liaqat, MD, and Afsaneh Khanedani, MD, helped during the preparation of the manuscript. We also would like to thank Dorte Oestreich for preparation of the figures.
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Footnotes |
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Reprint requests to Riccardo Cappato, MD, AK St Georg, 2. Med. Abteilung, Lohmuhlenstrasse 5, 20099 Hamburg, FRG.
Received October 25, 1995; revision received January 29, 1996; accepted February 1, 1996.
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