Characteristics of local electrogram predicting successful transcatheter radiofrequency ablation of left-sided accessory pathways

Spontaneous Variation of Ventriculo-Atrial Interval after Tachycardia Induction: Determinants and Usefulness in the Diagnosis of Supraventricular Tachycardias with Long Ventriculoatrial Interval

Background: Determining the mechanism of supraventricular tachycardias with prolongedP ventriculoatrial (VA) intervals is sometimes a challenge. Our objective is to analyse the determinants, time course and diagnostic accuracy (atypical atrioventricular nodal reentrant tachycardias [AVNRT] versus orthodromic reentrant tachycardias through an accessory pathway [ORT]) of spontaneous VA intervals variation in patients with narrow QRS tachycardias and prolonged VA. Methods: A total of 156 induced tachycardias were studied (44 with atypical AVNRT and 112 with ORT). Two sets of 10 measurements were performed for each patient—after tachycardia induction and one minute later. VA and VV intervals were determined. Results: The difference between the longest and the shortest VA interval (Dif-VA) correlates significantly with the diagnosis of atypical AVNRT (C coefficient = 0.95 and 0.85 after induction and at one minute, respectively; p < 0.001). A Dif-VA ≥ 15 ms presents a sensitivity and specificity for atypical AVNRT of 50% and 99%, respectively after induction, and of 27% and 100% one minute later. We found a robust and significant correlation between the fluctuations of VV and VA intervals in atypical AVNRTs (Coefficient Rho: 0.56 and 0.76, after induction and at one minute, respectively; p < 0.001 for both) but not in ORTs. Conclusions: The analysis of VA interval variability after induction and one minute later correctly discriminates atypical AVNRT from ORT in almost all cases.

A new insight into the different approaches for the ablation of para-Hisian accessory pathways: safety, effectiveness, and mechanism

BACKGROUND

To compare the safety, effectiveness, electrophysiological characteristics, and mechanisms of different approaches for the ablation of para-Hisian accessory pathways (APs).

METHOD

Eighteen consecutive patients with para-Hisian APs were enrolled in this study. Detailed mapping of retrograde conduction as well as antegrade conduction (if possible) in both the right sided His bundle region and non-coronary cusp (NCC) region was performed before ablation. Ten patients underwent initial ablation in the right septal (RS) region while the remaining 8 patients were ablated in NCC region. Repeat ablation was attempted in an alternative region if ablation at the first site failed.

RESULTS

Among the patients whose procedures were successful, 7 cases were successfully ablated with a NCC approach while 10 were conventionally ablated in RS region. For successful procedures targeting the NCC region, the earliest atrial activation (EAA) in NCC region preceded that at RS region by 4-13 ms. The distance between NCC targets and near-field His potential (NFH) points was longer than that between RS targets and NFH points. Additionally, the risk of complication after ablation in NCC region was lower compared with that following RS-targeted procedure.

CONCLUSION

NCC approach provided a high success rate and low risk of complication for the ablation of para-Hisian APs as long as EAA was observed in NCC region. Sites of successful para-Hisian AP ablation in NCC region had different retrograde mapping patterns in comparison with successful ablation sites in the RS region.

Transseptal or retrograde approach for transcatheter ablation of left sided accessory pathways: a systematic review and meta-analysis

BACKGROUND

Transcatheter ablation is the most effective treatment for patients with symptomatic or high-risk accessory pathways (AP). At present, no clear recommendations have been issued on the optimal approach for left sided AP ablation. We performed this meta-analysis to compare the safety and efficacy of transaortic retrograde versus transseptal approach for left sided AP ablation.

METHODS AND RESULTS

MEDLINE/PubMed and Cochrane database were searched for pertinent articles from 1990 until 2016. Following inclusion/exclusion criteria application, 29 studies were selected including 2030 patients (1013 retrograde, 1017 transseptal) from 28 observational single Centre studies and one randomized trial. Patients approached by transseptal puncture presented a significantly higher acute success (98% vs. 94%, p = 0.040). The incidence of late recurrences (p = 0.381) and complications (p = 0.301) did not differ among the two groups, but the pattern of complications differed: vascular complications were more frequent with transaortic retrograde approach, while cardiac tamponade was the main transseptal complication. No difference was noted in terms of procedural duration and fluoroscopy time (p = 0.230 and p = 0.980, respectively). Meta-regression analysis showed no relation between year of publication and acute success (p = 0.325) or incidence of complications (p = 0.795); additionally, no direct relation was found between age and acute success (p = 0.256) or complications (p = 0.863).

CONCLUSIONS

Left sided AP transcatheter ablation is effective in around 95% of the cases, with a very limited incidence of complications. Transseptal access provides higher acute success in achieving AP ablation; late recurrences are rare but observed similarly following both approaches. Retrograde approach is affected by a relatively high incidence of vascular complications.

Radiofrequency catheter ablation of accessory pathways during pre-excited atrial fibrillation: acute success rate and long-term clinical follow-up results as compared to those patients undergoing successful catheter ablation during sinus rhythm

The onset of recurrent or sustained atrial fibrillation (AF) is common during electrophysiological (EP) studies of accessory pathways (AP). We report our experience in patients with Wolff-Parkinson-White (WPW) syndrome in whom AF with rapid antegrade conduction over the AP occurred during an EP study and mapping and ablation were done during sustained AF, as compared to patients ablated during sinus rhythm. The study group consisted of 18 patients (group 1) with WPW syndrome who underwent catheter ablation during pre-excited AF. Two hundred and sixty-three patients, comparable for clinical characteristics, whose manifest APs were ablated under sinus rhythm formed the control group (group 2). Bipolar electrogram criteria recorded from the ablation catheter showing early ventricular activation relative to the delta wave on the surface ECG and AP potentials preceding the onset of ventricular activation were used as targets for ablation. Clinically documented atrial fibrillation was significantly more frequent and antegrade ERP of AP was significantly shorter in group 1 than in group 2 (39% vs 14%, P=0.014 and 268+/-37 vs 283+/-16, P<0.001, respectively). Procedure-related variables, acute success rates (17/18 [94%] in group 1, 251/263 [95%] in group 2; P>0.05) and late recurrence rates (0/18 [0%] in group 1 vs 5/263 [2%] in group 2; P>0.05) during a mean follow-up of 25+/-9 months (range 8-52 months) did not differ significantly. Our results show that both right- and left-sided accessory pathways can be mapped and ablated safely during pre-excited AF without delay, and that acute success and recurrence rates and long-term follow-up results are similar to those of pathways ablated during sinus rhythm.

Electrophysiological characteristics and radiofrequency ablation of accessory pathways with slow conductive properties

BACKGROUND

Atrioventricular accessory pathways (AP) with unusually long ventriculo-atrial (VA) conduction times are present in a significant subset of patients with the Wolff-Parkinson-White (WPW) syndrome, not including patients with the permanent form of atrioventricular junctional reciprocating tachycardia.

METHODS AND RESULTS

We compared the electrophysiological characteristics and outcomes after radiofrequency (RF) ablation in 34 patients with the WPW syndrome, a VA interval >80 ms, and paroxysmal tachycardia with an RP/PR ratio <1 (the slow group), vs 80 patients with WPW syndrome and a VA interval <80 ms (the fast group). AP were found in the posteroseptal region significantly more often in the slow than in the fast group. In addition, the decremental conductive properties of the AP were more common in the slow than in the fast group. Catheter ablation of AP was highly successful in both groups, although ablation required a greater number of RF applications and longer procedure times in the slow group, especially for AP with decremental conductive properties.

CONCLUSIONS

A posteroseptal AP location was more common in AP associated with long conduction times than in AP with typical conductive properties. Both types of AP were successfully ablated, although the slow group required longer procedures and more RF energy deliveries.

Unipolar electrogram characteristics predictive of successful radiofrequency catheter ablation of accessory pathways

INTRODUCTION

The purpose of this study was to determine the characteristics of the unipolar electrogram that are most helpful in predicting successful radiofrequency ablation of accessory pathways.

METHODS AND RESULTS

The unipolar electrogram was analyzed at 185 ablation sites in 53 patients; 94 attempts were directed at the site of earliest atrial activation ("atrial group") and 91 at the site of earliest ventricular activation ("ventricular group"). The electrogram was analyzed for several features, including pattern ("QS" or "initial R"). Unipolar pattern: Overall, a "QS" pattern was seen at 55% of unsuccessful, 75% of temporarily successful, and 90% of permanently successful sites. For the atrial group, the respective frequencies were 53%, 77%, and 92%, and for the ventricular group, 57%, 73%, and 86%. The difference in pattern distribution between unsuccessful and permanently successful sites was significant for all groups: overall, P < 0.0001; atrial group, P = 0.0005; ventricular group, P = 0.02. Absence of a "QS" pattern (i.e., "initial R") predicted a 92% chance of unsuccessful ablation. Additional features: Activation times were significantly shorter at permanently successful than at unsuccessful (P < 0.0001) or temporarily successful sites (P = 0.0002). No significant differences were found in atrial or ventricular amplitudes or in A/V ratios. Intrinsic deflection slew was lower at temporarily successful sites (P = 0.03 vs all other sites).

CONCLUSION

Ablation at sites revealing an "initial R" pattern (i.e., absent "QS") is very unlikely to be successful. Activation time is shorter at successful sites. These features are equally applicable when mapping the atrial potential as when mapping the ventricular potential.

[Analysis of local electrograms and characteristics of the ablation procedure in left-sided accessory pathways that required five or more pulses of radiofrequency]

INTRODUCTION AND OBJECTIVES

Radiofrequency ablation of left sided accessory pathways requires multiple pulses in some patients due to different factors such as inadequate mapping, inappropriate tissue electrode contact and particular anatomic factors. However these characteristics have not been specifically analyzed.

METHODS

We have studied a prospective ablative series of 65 consecutive patients with left-sided pathways submitted to radiofrequency ablation by a simplified technique. In every application point, we analyzed the electrogram features, application point, impedance, potency and temperature.

RESULTS

52 patients (80%) required less than 5 radiofrequency pulses (group A) and 13 (20%) required > or = than 5 pulses (group B). The presence of a suggestive potential accessory pathway in local electrogram was similar in both groups and there were no differences in the local A-V or V-A intervals. However, in patients with pre-excitation the Delta-V interval was shorter in group A than in group B (8 ms vs 15 ms; p < 0.001). Furthermore, the impedance observed from the ablation point in group A was lower (108 +/- 12 vs 121 +/- 22 ohms; p < 0.001), and the maximum watts required to reach the predetermined temperature was higher in group A (42 +/- 16 vs 31 +/- 18 watts; p < 0.001). Final success of the procedure was 100%.

CONCLUSIONS

Patients requiring more than 5 radiofrequency pulses had electrograms and tissue contact equal or better than those requiring less than 5 pulses. This suggests that difficulties encountered in some procedures can be due to anatomical factors rather than inaccurate mapping or insufficient tissue contact.

[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.

Torsade de pointes secondary to d,l-sotalol after catheter ablation of incessant atrioventricular reentrant tachycardia--evidence for a significant contribution of the "cardiac memory"

Radiofrequency catheter ablation of a right septal accessory pathway was performed in a 66-year-old patient with incessant orthodromic atrioventricular reentrant tachycardia. Intravenous administration of flecainide, ajmaline, verapamil, and d,l-sotalol had been ineffective in controlling the tachycardia. After the ablation procedure, precordial T-wave inversion was observed during sinus rhythm. These repolarization abnormalities persisted and were suggested to represent "cardiac memory." Three days later, atrial fibrillation with a fast ventricular response developed and oral d,l-sotalol, which had been well tolerated previously on a long-term basis, was started again. However, at this time, and in the presence of the persisting repolarization abnormalities, the T waves became deeper and broader within a few hours after the introduction of d,l-sotalol. Marked QT prolongation that was paralleled by the occurrence of repeated episodes of torsade de pointes developed. Serum electrolytes were normal. Direct current cardioversion was necessary due to the degeneration of torsade de pointes into ventricular fibrillation. Further sustained arrhythmia episodes were suppressed by temporary endocardial ventricular pacing. The patient recovered without any sequela. This case demonstrates that repolarization abnormalities after catheter ablation, which may be due, at least in part, to the "cardiac memory," are not always benign but may contribute significantly to proarrhythmia.

Catheter ablation of accessory pathways

Radiofrequency catheter ablation is a highly effective, curative treatment for arrhythmias related to accessory atrioventricular connections. Compared with medical therapy, ablation is more definitive, is more cost-effective, and is associated with a lower risk of proarrhythmia. This article updates the reader on the current indications, techniques, and innovations related to ablation of accessory pathways using radiofrequency energy.

Intracranial microembolic signals during radiofrequency ablation of accessory pathways

Intracranial microembolic signals, probably caused by gaseous emboli, are readily detectable in patients undergoing radiofrequency ablation in the left side of the heart only. Clinical value of the detected signals could not be equivocably assessed, because only 2 of the patients who were examined (both emboli positive) had transient neurologic symptoms.

Use of intracardiac echocardiography in interventional electrophysiology

Intracardiac echocardiography is emerging as a potentially useful tool during RF ablation procedures. There are a number of potential benefits of direct endocardial visualization during RF ablation including: (1) precise anatomical localization of the ablation catheter tip in relation to important endocardial structures, which cannot be visualized with fluoroscopy; (2) reduction in fluoroscopy time; (3) evaluation of catheter tip tissue contact; (4) confirmation of lesion formation and identification of lesion size and continuity; (5) immediate identification of complications; and (6) as a research tool to help in understanding the critical role played by specific endocardial structures in arrhythmogenesis. This article will review existing data and speculate as to possible future roles for intracardiac echocardiography in interventional electrophysiology.

Effect of electrophysiologic properties and location of manifest accessory pathways on local electrogram intervals at effective radiofrequency ablation sites

The purpose of this study was to determine if the electrophysiologic properties and the anatomic location of manifest accessory pathways affect the local electrogram intervals recorded at sites of successful radiofrequency ablation. Accessory pathways in 149 consecutive patients were categorized according to their anatomic location on the basis of the site of successful ablation. Three anatomic groups comprised 90 left free wall, 28 right free wall, and 31 posteroseptal pathways. The accessory pathways were also categorized according to their electrophysiologic properties on the basis of a hierarchical classification of the accessory pathway block cycle length. Four electrophysiologic groups (A, B, C, and D) comprised 54, 51, 28, and 16 accessory pathways, with mean accessory pathway block cycle lengths of 254 +/- 9, 288 +/- 10, 347 +/- 19, and 458 +/- 56 msec, respectively. The local atrial to ventricular (A-V) and atrial to accessory (A-K) pathway electrogram intervals recorded in sinus rhythm at the successful ablation site were significantly affected by the electrophysiologic group and were longest in group D compared with groups A, B, and C (A-V interval F(3,145) = 13.6, p < 0.001; A-K interval F(3,88) = 12.6, p < 0.001). The local A-V interval was also affected by the anatomic group and was longer in posteroseptal compared with free wall accessory pathways (F(2,146) = 15.0, p < 0.001). In contrast, the timing of the local ventricular activation to the delta wave onset (delta-V) was not significantly affected by the electrophysiologic group or the anatomic location of the accessory pathway. Thus the local A-V interval at the successful ablation site may vary because it is affected by the electrophysiologic properties and location of the accessory pathway, whereas the delta-V interval remains unaffected. These effects should be taken into account when selecting ablation sites in patients with manifest accessory pathways.

Signal-averaged intracardiac electrograms: a new method to detect kent potentials

INTRODUCTION

In patients with manifest accessory pathways, Kent potentials are often difficult to identify even at sites of successful catheter ablation, due largely to signal noise and catheter instability. We hypothesized that signal averaging the intracardiac electrogram recorded from the ablation catheter over a number of beats would improve the signal-to-noise ratio of the electrogram and aid in the detection of Kent potentials at accessory pathway locations.

METHODS AND RESULTS

We retrospectively analyzed distal-pair electrograms recorded from 9 successful, 6 transiently successful, and 10 failed ablation sites in 10 patients with manifest accessory pathways who underwent catheter ablation. We developed custom software to finely align 20 to 30 consecutive sinus beats and compute the signal average of the electrogram (SAE) for each site. Kent potentials were classified as probable, possible, or absent in the raw ablation site electrogram and the SAE base on morphologic criteria. A measure of beat-to-beat signal instability, the variability quotient (VQ), was also computed for each site. Probable Kent potentials were found in the raw ablation site electrogram at only 2 of the 15 successful and transiently successful sites, but were found in the SAE at 10 of these sites (P = 0.008). Eight of the 9 successful sites had VQ < 0.2, suggesting stable catheter-tissue contact, while 3 of the 6 transiently successful sites had VQ > 0.2, indicating unstable contact.

CONCLUSIONS

Signal averaging the intracardiac ablation site electrogram enhances detection of Kent potentials at accessory pathway locations. Catheter instability can be quantified by signal variability analysis and, when high, may predict lack of successful ablation even at sites where Kent potentials are present.

Radiofrequency catheter ablation of posteroseptal atrioventricular accessory pathways--location-specific electrographic characteristics of successful ablation sites

The electrographic features of successful sites of radiofrequency catheter ablation were analyzed in 33 cases of posteroseptal accessory pathways and compared with those from 155 cases of free wall accessory pathways. The atrioventricular intervals in the posteroseptal cases were significantly longer than in the free wall cases (posteroseptal vs left and right free wall; 38 vs 33 and 26 msec, respectively; p < 0.05), and the incidences of continuous electrograms (42 vs 63 and 79%; p < 0.01) and PQS-pattern unipolar electrograms (50 vs 76 and 78%; p < 0.05) were significantly lower in the posteroseptal cases. The V-delta intervals in the posteroseptal cases were significantly longer than in the left free wall cases (17 vs 13 msec; p < 0.05), but shorter than in the right free wall cases (17 vs 23 msec; p < 0.05). No statistically significant difference in the incidence of Kent potentials among the 3 groups was observed. In radiofrequency ablation of posteroseptal pathways, the length of the atrioventricular interval and the incidences of continuous electrograms and PQS-pattern unipolar electrograms may be unsatisfactory even at the appropriate target site, but the V-delta interval and Kent potential are good indicators of suitable target sites.

Variants of preexcitation--specialized atriofascicular pathways, nodofascicular pathways, and fasciculoventricular pathways: electrophysiologic findings and target sites for radiofrequency catheter ablation

INTRODUCTION

In the present report, the electrophysiologic findings in patients with different types of variants of preexcitation, i.e., atriofascicular, nodofascicular, and fasciculoventricular fibers, and the results of radiofrequency catheter ablation using different target sites are described.

METHODS AND RESULTS

Twelve patients (mean age 36 +/- 17 years) with variants of the preexcitation syndromes underwent electrophysiologic study and radiofrequency catheter ablation. The atrial origin of atriofascicular pathways remote from the normal AV node was assessed by application of late atrial extrastimuli that advanced ("reset") the timing of the next QRS complex without anterograde penetration into the AV node. In patients with atriofascicular pathways, ablation of the accessory pathway or the retrograde fast AV node pathway was attempted. Ablation of the atriofascicular pathways was guided by a stimulus-delta wave interval mapping in the first five patients and by recording of atriofascicular pathway activation potentials in the next five patients. A nodofascicular pathway was suggested if VA dissociation occurred during tachycardia and if atrial extrastimuli failed to reset the tachycardia without anterograde penetration into the AV node. A fasciculoventricular connection was suggested if the proximal insertion of the accessory pathway was found to arise from the His bundle or bundle branches. The PR interval was expected within normal limits during sinus rhythm and the QRS complex to be slightly prolonged with a discrete slurring of the R wave, suggesting a small delta wave. Ten of the 12 patients had evidence for atriofascicular pathways and one patient each for a nodofascicular and fasciculoventricular pathway. In six patients, the atriofascicular pathways were successfully ablated, and in two patients, the retrograde fast AV node pathway. In one patient, a concealed right posteroseptal accessory AV pathway served as the retrograde limb and was successfully ablated. The nodofascicular pathway was shown to be a bystander during AV node reentrant tachycardia. After successful fast AV node pathway ablation resulting in marked PR prolongation, no preexcitation was present during sinus rhythm because of the proximal insertion of the nodofascicular pathway distal to the delay producing parts of the AV node. The proximal insertion of the fasciculoventricular pathway was suggested to arise distal to the AV node at the site of the penetrating AV bundle. The earliest ventricular activation at the His-bundle recording site indicated the ventricular insertion of this accessory connection into the ventricular summit. The fasciculoventricular connection gave rise to a fixed ventricular preexcitation and served as a bystander during orthodromic AV reentrant tachycardia incorporating a left-sided accessory AV pathway.

CONCLUSION

The majority of patients with variants of the preexcitation syndrome present with specialized atriofascicular pathways that seem to originate from remnants of the specialized AV ring tissue. Nodofascicular and fasciculoventricular pathways exist and may give rise to preexcitation, although their functional role in participation of clinical arrhythmias still needs to be elucidated. In the present study, both a fasciculoventricular pathway and a nodofascicular pathway acted as a bystander.

"Pseudodisappearance" of atrial electrogram during orthodromic tachycardia: new criteria for successful ablation of concealed left-sided accessory pathways

OBJECTIVES

This study sought to analyze two new criteria along with other known predictors of success of radiofrequency ablation. Background. Although the overall success rate of radiofrequency ablation of accessory pathways is high, the individual predictive value of each of the established criteria is low.

METHODS

We prospectively studied the local electrograms obtained before the application of radiofrequency energy in 33 patients with a left-sided concealed accessory pathway successfully ablated. Two new criteria ("pseudodisappearance" during tachycardia of a bipolar atrial electrogram visible during sinus rhythm and the presence of an "atrial notch" in the ascending limb of the unipolar ventricular electrogram during tachycardia) were studied along with other known predictors. Electrograms recorded at a total of 157 sites were analyzed (33 successful applications, 124 failures).

RESULTS

Electrogram characteristics that were predictive of success during ablation on the basis of univariate analyses were a pseudodisappearance criterion (p<0.001), the presence of a Kent potential (p<0.005) and the presence of an "atrial notch" (p<0.005). After adjustment for between-patient differences, logistic regression analysis showed that only the "pseudodisappearance" criterion (odds ratio [OR] 7.2, 95% confidence interval [CI] 1.2 to 42.5, p<0.03) and the presence of a Kent potential (OR 2.4, 95% CI 1.01 to 5.79, p<0.05) had independent predictive value.

CONCLUSIONS

The pseudodisappearance during tachycardia or ventricular pacing of a bipolar atrial electrogram present during sinus rhythm is associated with a good outcome during radiofrequency ablation of concealed accessory pathways. These observations may help to ablate accessory pathways and to avoid missing appropriate sites for ablation when the atrial activation is not clearly visible at the local electrogram.

Radiofrequency ablation of atrial insertion of left-sided accessory pathways guided by the "W Sign"

INTRODUCTION

The aim of this study was to evaluate the efficacy of radiofrequency (RF) ablation of the atrial insertion of left-sided accessory pathways with guidance by a specific morphologic characteristic of the local electrogram, which we call the "W sign." This represents the shortest local atrioventricular (AV) interval during sinus rhythm in patients with manifest preexcitation or the shortest local VA interval during AV reciprocating tachycardia and/or ventricular pacing in patients with concealed accessory pathways.

METHODS AND RESULTS

The transseptal technique was used in 31 patients (18 men, 13 women; aged 32 +/- 13 years), and RF ablation of 33 accessory pathways (26 manifest and 7 concealed) was attempted. Patients presented with palpitations (n = 16), presyncope (n = 10), or syncope (n = 5). The clinical arrhythmia was AV reciprocating tachycardia (n = 24) or atrial fibrillation (n = 7). In 21 patients (68%) electrophysiologic study and RF ablation were performed at a single session. Accessory pathways were left posteroseptal (n = 5) or left free wall (n = 28). The "W sign," formed from merging of the local atrial and ventricular electrograms, was identified at all successful sites prior to ablation. Ablation was successful in all patients. A median of 7 RF lesions were delivered per patient. The fluoroscopy time was 76 +/- 48 minutes; total procedure time was 5.4 +/- 1.9 hours. No significant complications occurred. Early recurrence (< or = 24 hours) occurred in 1 patient; during 6 +/- 4 months, accessory pathway conduction recurred in another patient.

CONCLUSION

We conclude that RF ablation of the atrial insertion of left accessory pathways can be very successful when guided by the "W sign."

Atrial flutter ablation: electrophysiological landmarks

Understanding the configuration of the whole flutter circuit is for us the only valid parameter allowing the design of an ablation strategy. Fragmented or double electrograms may have different meanings in different parts of the circuit, and full activation mapping is the best clue to their interpretation. Correlation of anatomy with activation sequence will mark the best ablation target (isthmus) in each case. Multiple simultaneous recordings from the septum and right atrial anterior wall are very helpful to rapidly diagnose circular activation of the right atrium. In cases without this type of activation, coronary sinus recordings and the study of postentrainment cycles are helpful to localize the reentry circuit.

Radiofrequency catheter ablation of atrial flutter: procedural success and long-term outcome

The objective of this study was to describe the procedural success and clinical recurrences after radiofrequency catheter ablation of atrial flutter. A deflectable catheter with a 4 or 5 mm tip was positioned in the posterior right atrium. Radiofrequency energy was delivered sequentially from the tricuspid annulus to the inferior vena cava. Catheter ablation during 18 sessions for 16 patients resulted in abrupt atrial flutter termination and noninducibility in all patients. Successful sites were near the os of the coronary sinus but had no distinguishing electrographic features. During a follow-up period of 8 +/- 5 months, 4 (25%) patients had recurrence of atrial flutter; 3 of 4 underwent successful repeat ablation. By actuarial analysis, 87% of patients remained in normal sinus rhythm 6 months after the initial procedure. The only distinguishing feature of those with recurrence compared with those whose sinus rhythm was maintained was the induction of nonclinical atrial arrhythmia (50% vs 0%, respectively; p < 0.05). One patient had resolution of presumed tachycardia-related cardiomyopathy. Catheter ablation by an anatomic approach was highly successful in terminating type 1 atrial flutter and was associated with good long-term response. This technique may represent a meaningful alternative for restoration and maintenance of normal sinus rhythm. However, further investigation is warranted to define its clinical role fully.

Assessment of pacing maneuvers used to validate anterograde accessory pathway potentials

Four pacing maneuvers have been proposed to validate an anterograde accessory pathway potential (APP): (1) atrial pacing to induce complete block between the atrial electrogram and the APP; (2) ventricular pacing to advance the APP without altering the timing of the atrial electrogram; (3) atrial pacing to induce complete block between the APP and the ventricular electrogram; and (4) ventricular pacing to advance the ventricular electrogram without altering the timing of the APP. The purpose of this study was to assess these validation techniques by applying them to electrograms that simulated APPs but which were known to be atrial in origin. In 32 patients undergoing an electrophysiology procedure, a split atrial electrogram containing two components separated by at least 30 msec (mean 54 +/- 15 msec) was recorded. Using an atrial extrastimulus technique, complete block between the two components of the atrial electrogram (criterion 1) could never be induced, but complete block between the second component of the atrial electrogram and the ventricular electrogram (criterion 3) consistently was induced. Using a ventricular extrastimulus technique, the second component of the atrial electrogram consistently could be advanced by 10 to 40 msec without altering the timing of the first component (criterion 2). In addition, with ventricular pacing, the ventricular electrogram consistently was advanced without altering the timing of the two components of the atrial electrogram (criterion 4). In conclusion, among the four pacing maneuvers used to validate an anterograde APP, the only one that may be specific for an APP is the ability to induce complete block between the atrial electrogram and the APP.

An anatomically and electrogram-guided stepwise approach for effective and safe catheter ablation of the fast pathway for elimination of atrioventricular node reentrant tachycardia

OBJECTIVES

We describe a new stepwise anatomically and electrogram-guided strategy for radiofrequency catheter ablation of the fast pathway.

BACKGROUND

Anatomically and electrogram-guided approaches have been developed for slow pathway ablation in patients with atrioventricular (AV) node reentrant tachycardia; however, no stepwise systematic approaches exist for fast pathway ablation.

METHODS

Fifty-three patients (mean [+/- SD] age 43 +/- 11 years) with AV node reentrant tachycardia underwent attempted ablation of the fast pathway. The ablation catheter was initially positioned posterior and slightly superior to the site of the maximal His bundle recording region. At these sites, the amplitude of the local atrial potential was usually at least twice as high as the local ventricular potential, and a small proximal His bundle potential was recorded. When the first pulse was ineffective, the ablation catheter was repositioned stepwise slightly inferior to more midseptal sites.

RESULTS

After a mean of 3.4 +/- 3.1 radiofrequency pulses (median 2, range 1 to 12), AV node reentrant tachycardia was noninducible in 51 patients (96%). No inadvertent complete AV block occurred. The AH interval was prolonged from 79 +/- 19 to 145 +/- 37 ms (p < 0.001). Thirty-eight patients (72%) developed complete ventriculoatrial block. Recording of a His bundle potential at the target site, stability of the local electrograms and occurrence of fast junctional rhythms during energy applications were more often observed at successful sites than transiently effective or noneffective sites. During a follow-up period of 12 +/- 7 months, 3 (6%) of 51 patients had a clinical recurrence of AV node reentrant tachycardia.

CONCLUSIONS

Radiofrequency catheter ablation of the fast pathway using a combined anatomically and electrogram-guided stepwise approach is highly effective and safe. The safety of this approach seems to be due to the stable position of the ablation catheter at the interatrial septum, rather than across the tricuspid annulus, and the larger distance to the central body of the AV node and bundle of His.

Localization and radiofrequency catheter ablation of left-sided accessory pathways during atrial fibrillation. Feasibility and electrogram criteria for identification of appropriate target sites

OBJECTIVES

The purpose of the present study was to assess the feasibility of and electrophysiologic criteria for successful radiofrequency catheter ablation of left-sided accessory pathways during atrial fibrillation in patients with Wolff-Parkinson-White syndrome.

BACKGROUND

The onset of recurrent or sustained atrial fibrillation can complicate or significantly prolong accessory pathway catheter ablation procedures.

METHODS

We studied 19 consecutive patients (mean age [+/-SD] 44 +/- 16 years) with Wolff-Parkinson-White syndrome who had ongoing atrial fibrillation with rapid anterograde conduction over the accessory pathway (mean ventricular rate [+/-SD] 173 +/- 26 beats/min, range 130 to 220) at the beginning of the localization procedure during radiofrequency catheter ablation. Localization and ablation of the accessory pathway were performed with a 7F deflectable catheter (4-mm tip) that was placed underneath the mitral valve annulus. The electrophysiologic criteria from unipolar and bipolar local electrograms were compared for successful (n = 18) and unsuccessful (n = 39) sites.

RESULTS

The accessory pathways were localized in the left posteroseptal (n = 6), posterior (n = 1), posterolateral (n = 7) and lateral (n = 5) regions and successfully ablated during atrial fibrillation in 18 (95%) of 19 patients with a mean of 3 +/- 2 radiofrequency pulses (range 1 to 8, median 2). Presence of an accessory pathway potential (94% vs. 44%), early activation time of the ventricular electrogram (-3.2 +/- 9.2 vs. -15.3 +/- 12.6 ms) and recording of atrial activation (88% vs. 61%) from the ablation catheter were helpful in identifying successful sites (p < 0.001, p < 0.001 and p < 0.05, respectively, compared with unsuccessful sites). In addition, the ventricular activation time in relation to the intrinsic deflection of the unipolar electrogram was significantly earlier at successful than unsuccessful sites (18.1 +/- 4.8 vs. 24.4 +/- 6.6 ms, p < 0.01). A QS complex on the unipolar electrogram was observed at 96% of successful sites and at 94% of unsuccessful sites (p = 0.74). Multivariate logistic regression analysis revealed that the presence of an accessory pathway potential (p < 0.002) and early ventricular activation time in relation to the onset of the QRS complex (p < 0.001) were independent predictors of ablation success.

CONCLUSIONS

Localization and radiofrequency catheter ablation of left-sided accessory pathways is possible in patients with sustained atrial fibrillation and rapid anterograde conduction over the accessory pathway during the ablation procedure. The electrophysiologic criteria described here can be used to reliably identify successful sites for radiofrequency ablation.

The effect of radiofrequency catheter ablation on myocardial creatine kinase activity

INTRODUCTION

The primary mechanism of myocardial injury during radiofrequency (RF) catheter ablation in the heart is presumed to be thermal. Creatine kinase has been measured in serum to assess the volume of myocardial injury after ablation. However, its thermal inactivation by RF ablation could lead to underestimation of the true volume of injury.

METHODS AND RESULTS

Serial RF lesions were created in 10 canine left ventricles in vivo, and serial serum creatine kinase activities were measured and compared to lesion volume. To assess the stability of myocardial creatine kinase during RF catheter ablation, 29 RF ablations were made on the epicardial surface of porcine left ventricle in vivo and a 2-mm core biopsy was rapidly removed. The cores were rapidly frozen, sectioned longitudinally in 1-mm slices, and homogenized in 0.3 M Tris buffer solution containing EDTA and dithiothreitol for subsequent analysis of creatine kinase activity. An additional 19 tissue cores from RF lesions were stained and used to determine mean lesion depth. Normal tissue biopsies were exposed to 60 seconds of hyperthermia (37 degrees to 85 degrees C, n = 190), or high-density RF current at 50 degrees C (0 to 100 mA/mm2, n = 50), and tissue creatine kinase activity was measured. There was no evidence of creatine kinase washout within the first 2 hours, and peak values were measured 5 to 7 hours postablation. Tissue creatine kinase activity in the first mm depth of RF lesions averaged 10% of control values and increased over the first 5 mm of lesion depth. The mean creatine kinase activity within the hemisphere of ablated myocardium was calculated to be 31% of control. Creatine kinase activity declined significantly at temperatures above 65 degrees C, but no difference in tissue creatine kinase activity was observed among differing levels of RF current exposure in the absence of significant heating.

CONCLUSIONS

Creatine kinase activity in myocardial tissue is significantly diminished within the RF lesion. Creatine kinase activity is not stable at temperatures above 65 degrees C, which are routinely achieved within the central zone of RF ablation, and is unaffected by RF current in the absence of hyperthermia. Measurements of serum creatine kinase activity after RF catheter ablation may significantly underestimate the volume of myocardial injury.

Anatomic, electrical, and mechanical factors affecting bipolar endocardial electrograms. Impact on catheter ablation of manifest left free-wall accessory pathways

BACKGROUND

The use of bipolar endocardial electrogram characteristics to guide radiofrequency (RF) current catheter ablation of accessory pathways (APs) has been advocated by several investigators. However, the influences of a varying anatomy of the AP and the atrioventricular groove, of different ablative approaches, and of RF current pulses preceding the final pulse have not been adequately addressed.

METHODS AND RESULTS

Local bipolar endocardial electrograms were retrospectively analyzed in a uniform cohort of 62 consecutive patients with a single manifest AP located on the left free wall; in all patients, the AP had been ablated by a uniform approach with a single catheter advanced retrogradely toward the mitral annulus. Electrogram parameters assessed were the presence or absence of a presumed AP potential, the atrial-to-ventricular (A/V) amplitude ratio, the A-V interval, and the onset of delta wave to local ventricular activation (delta-V) interval. The AP location was classified on fluoroscopy as anterior, lateral, or posterior. Catheter stability was verified by comparing pre- and post-RF amplitudes of local atrial potentials. The ablation site was ventricular in 52 patients (group A) and atrial in 10 (group B). In group A, 26 APs (50%) required a single RF current pulse for ablation. These APs showed no anatomic predilection and no statistically significant differences in electrogram parameters from 24 APs that were ablated only after a median of three pulses had failed, suggestive of a wider ventricular insertion of the latter APs. A lower A/V ratio and a higher incidence of transient AP block found in the remaining 2 group A patients, who had anteriorly located APs requiring > 10 failed pulses, suggested an adverse anatomy of the A-V groove in that region. A stepwise multivariate logistic regression analysis revealed that the simultaneous presence of (1) a presumed AP potential, (2) an A/V ratio > or = 0.10, (3) an A-V interval < or = 40 milliseconds, and (4) a delta-V interval < or = 0 milliseconds was associated with a specificity of 94% and a positive predictive accuracy of 87% for an RF pulse to be successfully applied to the ventricular insertion to the AP. Compared with APs of group A, APs of group B were distinguished by unsuccessful ventricular pulses associated with a delta-V interval > 10 milliseconds in the presence of an A/V ratio > 0.33 (specificity of 97% and positive predictive accuracy of 82%), which is suggestive of a more epicardial ventricular insertion of these APs.

CONCLUSIONS

The effect of anatomic variations of the AP and the A-V groove is reflected in the bipolar endocardial electrogram and needs to be considered in the approach to AP ablation. The stepwise inclusion of the four electrogram criteria introduced in this study may improve the efficacy of RF catheter ablation of a manifest left free-wall AP at its ventricular insertion. Whenever mapping cannot improve on a delta-V interval > 10 milliseconds despite apparently close contact with the mitral annulus ("good" A/V ratio), attempts at ablation are likely to be successful at the atrial aspect of the mitral annulus.

Recurrence and late block of accessory pathway conduction following radiofrequency catheter ablation

INTRODUCTION

Many issues regarding the recurrence of accessory pathway conduction and the long-term outcome of late block of accessory pathway conduction are still unknown or controversial.

METHODS AND RESULTS

Data from 217 patients who underwent an initially successful radiofrequency ablation of accessory pathways and 7 patients with late block of accessory pathway conduction following an initially unsuccessful ablation were analyzed. During a mean follow-up of 19 +/- 11 months, accessory pathway conduction resumed in 21 (10%) of 217 patients following an initially successful ablation and in 6 (86%) of 7 patients with late block of accessory pathway conduction (P < 0.01). After initially successful ablations, the recurrence rates of accessory pathway conduction at 1, 3, and 6 months were 5.9%, 7.4%, and 11.3%, respectively. A late electrophysiologic study at 6 months uncovered recurrence in only 1 of 124 asymptomatic patients, but failed to detect the late recurrence in 2 patients in whom the accessory pathway conduction resumed after more than 6 months. Multivariate analysis revealed that independent predictors for recurrence of accessory pathway conduction were concealed accessory pathway, presence of transient effect of radiofrequency pulse, and more than 5 pulses required for initial cure. Accessory pathway location, length of the tip electrode of the ablation catheter, and repeat radiofrequency pulses ("safety pulses") after effective pulses did not predict resumption of accessory pathway conduction.

CONCLUSIONS

After initially successful ablation, the recurrence rates of accessory pathway conduction at 1, 3, and 6 months were 5.9%, 7.4%, and 11.3%, respectively. Late electrophysiologic testing had little prognostic value in asymptomatic patients following successful ablation. Application of "safety pulses" did not prevent recurrence. Late block of accessory pathway conduction did not predict long-term efficacy.

Successful and unsuccessful sites of radiofrequency catheter ablation of accessory atrioventricular connections

Local electrograms from 47 consecutive patients who underwent successful radiofrequency catheter ablation of 49 accessory atrioventricular (AV) connections were analyzed. One hundred twenty-two local electrograms were recorded at 27 successful and 95 unsuccessful sites immediately before radiofrequency catheter ablation of 27 manifest accessory AV connections during preexcited sinus rhythm or atrial pacing. Continuous electric activity was found in 96% of successful sites versus 71% of unsuccessful sites (p < 0.01). Possible accessory pathway (AP) potentials were present only in 15% of successful and 2% of unsuccessful sites, respectively (p < 0.05). All measured time intervals were significantly shorter for successful sites as compared to unsuccessful sites of ablation of manifest accessory AV connections. Unipolar electrograms from the tip of the ablation catheter of each successful and unsuccessful ablation site were available for the last 16 patients with manifest accessory AV connections. A PQS pattern of the unipolar electrogram was associated with a higher success rate, whereas a PrS pattern never resulted in successful ablation of an accessory AV connection. Multivariate logistic regression analysis of the local electrogram characteristics of rapidly conducting, concealed accessory AV connections revealed the interval between the onset of the local ventricular and atrial electrogram (VoAo interval) as the only independent variable associated with successful sites for radiofrequency catheter ablation. The only study patient with a slowly conducting, concealed accessory AV connection underwent successful ablation with the first lesion of radiofrequency energy at the site with the shortest VoAo interval. We conclude that (1) the shortest local AV intervals and local ventricular electrograms preceding the earliest onset of the delta wave in any surface lead are predictive of successful ablation of manifest accessory AV connections; (2) the shortest local VA intervals during orthodromic AV reentry tachycardia or right ventricular pacing are predictive of successful ablation of concealed accessory AV connections; and (3) unipolar recordings from the tip of the ablation catheter should be recorded routinely during mapping of manifest accessory AV connections to identify appropriate target sites for radiofrequency energy applications.

Ablation of left free-wall accessory pathways using radiofrequency energy at the atrial insertion site: transseptal versus transaortic approach

INTRODUCTION

Transcatheter ablation of the left free-wall atrioventricular accessory pathways (AP) by delivery of radiofrequency current at the ventricular insertion site has been shown to be effective. The efficacy of such a technique targeting the atrial insertion site of the AP was evaluated.

METHODS AND RESULTS

One hundred consecutive patients with left free-wall APs and symptomatic supraventricular tachyarrhythmias were included. APs were manifest in 55 patients and concealed in 45. There were 55 men and 45 women with a mean age of 35 years. A total of 107 left free-wall APs were identified in these patients. In these 100 patients, successful ablation was accomplished in all by using a transseptal (45 patients) or transaortic (54 patients) technique. In one patient, ablation was accomplished from within the coronary sinus. Seven patients required a repeat ablative procedure, which was performed successfully. During 107 ablative procedures, six were associated with nonfatal complications including pericardial effusion (hemopericardium) in two patients, mild mitral regurgitation in two patients, swelling of the left arm in one patient, and staphylococcal bacteremia in one patient. Eighty-two (82%) patients underwent a repeat electrophysiologic study 6 to 8 weeks after successful ablation and were found to have no functioning AP or inducible supraventricular tachycardia. During a mean follow-up of 20 +/- 8 months, none of the 100 patients had a recurrence of tachyarrhythmias.

CONCLUSION

These data indicate that the atrial insertion site of the AP can be successfully ablated in the majority of patients with left free-wall APs by using either a transseptal or transaortic approach. Furthermore, both techniques are associated with minimal morbidity and no mortality.

Unipolar electrogram models for prediction of outcome in radiofrequency ablation of accessory pathways

Meticulous catheter positioning close to the accessory pathway is essential for successful radiofrequency ablation. The aim of this study was to identify local unipolar electrogram characteristics predictive of radiofrequency ablation outcome, enabling more accurate accessory pathway localization and catheter positioning. So far mainly bipolar electrogram parameters have been evaluated, stressing the importance of the presence of an accessory pathway potential. However, especially in the absence of this parameter, the unipolar recording mode can be expected to hold several advantages. Nine local unipolar electrogram characteristics were analyzed in preexcited sinus rhythm directly preceding radiofrequency pulses in 35 consecutive patients with a manifest accessory atrioventricular pathway. A total of 1,230 unipolar electrogram complexes were analyzed and recorded at 138 ablation sites. Ablation was successful in 30/35 patients (86%). Multivariate analysis provided two unipolar models for prediction of ablation outcome: in Model I, sites with a suspected accessory pathway potential, local AV interval < or = 30 msec and catheter stability had 76% probability of success, but no more than 1% in their absence. In contrast, using the bipolar recording mode, presence of a suspected accessory pathway potential was the only one of these parameters shown to differentiate between successful and unsuccessful sites, with a predicted chance of success of 48%. Model II, not requiring assessment of possible accessory pathway potentials, showed a 63% probability of success for the combination of initial positivity of the local ventricular signal < or = 0.1 mV, AV interval < or = 30 msec, and catheter stability, but no more than 7% in their absence. Moreover, gradual decrease of initial ventricular positivity and AV interval while approaching a subsequently successful site allows the use of these parameters as dynamic mapping tools. Local unipolar electrogram parameters may thus facilitate precise accessory pathway localization and catheter positioning while offering important information supplementary to the bipolar mode, and enable accurate prediction of ablation outcome at a given site also in the absence of accessory pathway potential recording.