Incidence, significance, and pharmacological responses of catheter-induced mechanical trauma in patients receiving radiofrequency ablation for supraventricular tachycardia

Adenosine revives catheter-induced mechanical blocks in radiofrequency ablation

Adenosine can hyperpolarize the atrial action potential, which helps rapidly re-establish the membrane potential in ablated sites and unmask "dormant conduction." It has been reported that pharmacological agents, including adenosine, were unable to revive traumatized tissues. We present the first case of the catheter-induced mechanical block ("bump" phenomenon) that was unmasked with adenosine administration in the working myocardium of the superior vena cava. This result may be because, unlike before, we could determine the force of contact between the tip of the ablation catheter and the myocardial tissue. This case suggests the clinical usefulness of adenosine for unmasking bumped sites.

Antegrade slow pathway mapping of typical atrioventricular nodal reentrant tachycardia based on direct slow pathway capture

BACKGROUND

Radiofrequency (RF) ablation of typical atrioventricular nodal reentrant tachycardia (tAVNRT) is performed without revealing out the location of antegrade slow pathway (ASp). In this study, we studied a new electrophysiological method of identifying the site of ASp.

METHODS

This study included 19 patients. Repeated series of very high-output single extrastimulations (VhoSESts) were delivered at the anatomical slow pathway region during tAVNRT. Tachycardia cycle length (TCL), coupling interval (CI), and return cycle (RC) were measured and the prematurity of VhoSESts [ΔPM (= TCL - CI)] and the prolongation of RCs [ΔPL (= RC - TCL)] were calculated. Pacing sites were classified into two categories: (i) ASp capture sites [DSPC(+) sites], where two different RCs were shown, and ASp non-capture sites [DSPC(-) sites], where only one RC was shown. RF ablation was performed at DSPC(+) sites and/or sites with catheter-induced mechanical trauma (CIMT) to ASp.

RESULTS

DSPC(+) sites were shown in 13 patients (68%). RF ablation was successful in all patients without any degree of atrioventricular block nor recurrence. Total number of RF applications was 1.8 ± 1.1. Minimal distance between successful ablation sites and DSPC(+)/CIMT sites and His bundle (HB) electrogram recording sites was 1.9 ± 0.8 mm and 19.8 ± 6.1 mm, respectively. ΔPL of more than 92.5 ms, ΔPL/TCL of more than 0.286, and ΔPL/ΔPM of more than 1.565 could identify ASp with sensitivity of 100%, 91.1%, and 88.9% and specificity of 92.9%, 97.0%, and 97.6%, respectively.

CONCLUSIONS

Sites with ASp capture and CIMT were close to successful ablation sites and could be useful indicators of tAVNRT ablation.

Mechanical suppression of premature ventricular complexes during catheter ablation procedures

Introduction

Mechanical suppression of premature ventricular complexes (PVCs) is not a well-known observation. We retrospectively reviewed this phenomenon in the Ventricular Arrhythmia (VA) ablation procedures performed at Richard L. Roudebush Veterans Health Administration (VHA) center.

Methods

Data from 40 consecutive patients who underwent VA ablation at VHA, Indianapolis, IN, with 44 VA was included in the study. Demographic and electrophysiological parameter data was collected.

Results

Overall the mean age of the population was 64 ± 11 years. The phenomenon of mechanical suppression was seen in 11 PVCs. The mean age was 59 ± 15 years in the group in which mechanical suppression was seen. Of the 11 cases, the site of earliest activation was seen in the coronary sinus in 8 and in the pulmonary artery in 3. In one case catheter ablation was not performed because of proximity to the left coronary artery system. However, sustained pressure at the site with earliest electrograms (−35 ms) and 95% pacematch resulted in long-term suppression of PVCs. In the cases in which mechanical suppression was seen, there was a statistically significant reduction in PVC burden compared to pre ablation PVC load (1.1% ± 1.50% (post ablation) versus 24.04% ± 13.07% (pre ablation) versus p < 0.05).

In all the 11 cases the site of mechanical suppression was also the site with earliest electrograms.

Conclusion

This case series illustrates phenomenon of mechanical suppression of PVCs as an indication for good site for successful ablation in unique veteran patient population.

Novel use of a 3-dimensional mapping system in cryoablation of right-sided and septal accessory pathways: playback ablation

PURPOSE

Despite recent advances in the treatment of eliminating accessory pathways (APs), catheter-induced mechanical block (bump) of APs has been reported to result in a less favorable outcome with high primary failure and recurrence rates. The real bump site cannot always be precisely reapproached under fluoroscopy so physicians can perform ablation to a location different from where the mechanical block was encountered. In this paper, we describe this novel use of a 3-dimensional (3D) mapping system (playback ablation) with a case series.

METHODS

The EnSite Velocity system (St. Jude Medical, St. Paul, MN, USA), a 3D mapping system, has a unique function that records the positional information of catheters in a 3D geometric map and the local potential of catheters continuously. This function enables physicians to specify the bump site in a 3D geometric map and apply ablation to the bump site even if the catheter moves away from the bump site.

RESULTS

This technique helped us eliminate APs in two patients with bump of APs, and they have been free of preexcitation and arrhythmias without the use of anti-arrhythmic drugs for more than 3 months.

CONCLUSIONS

This technique may contribute to improving long-term success in patients with mechanical block of APs.

Patients' and procedural characteristics of AV-block during slow pathway modulation for AVNRT-single center 10year experience

BACKGROUND

Permanent AV-block is a recognized and feared complication of slow pathway modulation for AVNRT. We aimed to assess incidence of transient and permanent AV-block as well as consequences of transient AV-block in a large contemporary AVNRT ablation cohort.

METHODS

We searched our single center prospective ablation database for occurrence of transient and permanent AV-block during slow pathway modulation between January 2004 and October 2015. We analyzed patients' and procedural characteristics as well as outcome of patients in whom transient or permanent AV-block occurred.

RESULTS

Of 9170 patients who underwent a catheter ablation at our institution between January 2004 and October 2015, 2101 patients (64% women, mean age 50±18years) underwent slow pathway modulation. In three patients, permanent AV-block occurred during RF application. Additional two patients had transient AV-block that recovered (after a few minutes and 25min), but recurred within two days of the procedure. All five patients underwent dual chamber pacemaker implantation (0.2%). Transient AV-block related to RF delivery occurred in 44 patients (2%). Transient mechanical AV-block occurred in additional 17 patients (0.8%). In 12 patients, ablation was continued despite transient AV-block. One of these patients developed permanent AV-block.

CONCLUSION

Permanent AV-block following slow pathway modulation is a rare event, occurring in 0.2% of patients in a large contemporary single center cohort. Transient AV-block is more frequent (2%).

Age-related location of manifest accessory pathway and clinical consequences

BACKGROUND

Accessory pathway (AP) ablation is not always easy. Our purpose was to assess the age-related prevalence of AP location, electrophysiological and prognostic data according to this location.

METHODS

Electrophysiologic study (EPS) was performed in 994 patients for a pre-excitation syndrome. AP location was determined on a 12 lead ECG during atrial pacing at maximal preexcitation and confirmed at intracardiac EPS in 494 patients.

RESULTS

AP location was classified as anteroseptal (AS)(96), right lateral (RL)(54), posteroseptal (PS)(459), left lateral (LL)(363), nodoventricular (NV)(22). Patients with ASAP or RLAP were younger than patients with another AP location. Poorly-tolerated arrhythmias were more frequent in patients with LLAP than in other patients (0.009 for ASAP, 0.0037 for RLAP, <0.0001 for PSAP). Maximal rate conducted over AP was significantly slower in patients with ASAP and RLAP than in other patients. Malignant forms at EPS were more frequent in patients with LLAP than in patients with ASAP (0.002) or PSAP (0.001). Similar data were noted when AP location was confirmed at intracardiac EPS. Among untreated patients, poorly-tolerated arrhythmia occurred in patients with LLAP (3) or PSAP (6). Failures of ablation were more frequent for AS or RL AP than for LL or PS AP.

CONCLUSIONS

AS and RLAP location in pre-excitation syndrome was more frequent in young patients. Maximal rate conducted over AP was lower than in other locations. Absence of poorly-tolerated arrhythmias during follow-up and higher risk of ablation failure should be taken into account for indications of AP ablation in children with few symptoms.

Simultaneous Accessory Pathway and AV Node Mechanical Block

We report a clinical case of a 22-year-old female referred to our institution due to palpitations and preexcitation. Her ECG suggested a right superior paraseptal accessory pathway (AP), which was localised during the electrophysiological study at the superior paraseptal region in close proximity to the His recordings. Reproducible orthodromic reciprocating tachycardia was induced by atrial pacing with extrastimuli. Cryo-mapping performed in the area of earliest atrial activation was not able to terminate the tachycardia. A second attempt, slightly more posterior, caused mechanical block of the AP, which rendered the tachycardia non-inducible. More pressure with the ablation catheter determined a Wenckebach type supra-hisian AV block, which was transient but reproducible. Given this finding no ablation was done. Simultaneous block to the AP and the atrioventricular node has rarely been reported using radiofrequency energy. However, to our knowledge this phenomenon has not been previously reported in large series using cryo-thermal energy.

Successful ablation of right atriofascicular pathway guided by pathway potential recording despite catheter-induced mechanical pathway trauma

Radiofrequency ablation of right atriofascicular pathways (RAFPs) is frequently complicated by the occurrence of mechanically induced trauma to the pathway by the ablation catheter. Since recording of accessory pathway (AP) potential is critical for achieving successful ablation of RAFP, one may fear that long-lasting mechanically induced trauma to the AP will affect recording of AP potential and thereby adversely affect the procedure outcome. We report a patient with antidromic tachycardia involving an antegrade RAFP. Despite long-lasting catheter trauma to the RAFP, mapping of the tricuspid annulus showed persistent recording of an AP potential that enabled us to continue the procedure and successfully abolish the AP.

[Relationships between age and accessory pathway location in Wolff-Parkinson-White syndrome]

BACKGROUND

Radiofrequency ablation of atrioventricular accessory pathway (AP) which is currently used, remains associated with a risk of complete AV block in the case of anteroseptal (AS) location and its indication remains debatable. The purpose of the study was to evaluate the frequency of AS location in Wolff-Parkinson-White syndrome (WPW) and the clinical and electrophysiological data of these patients.

METHODS

Electrophysiologic study (EPS) was performed in 503 pts aged from six to 85 years (35+/-17), 297 men, 206 women, recruited for a patent WPW syndrome. The location of AP was determined on a 12 lead ECG during atrial pacing at maximal preexcitation according to classical criteria. The location was confirmed at EPS. Eleven pts were excluded because the location remained not clearly defined. EPS was indicated for suspected or documented tachycardias (n=264), syncope (n=68) or was systematic in asymptomatic patients (n=171).

RESULTS

AS AP location was identified in 34 patients aged eight to 48 years (7%). Their mean age was younger than the age of remaining population (25+/-13 versus 36+/-17, p<0.001). According to the age, the prevalence of AS location was significantly higher in children and adolescents (14%) than after 40 years (3%) (p<0.01). There was no AS location among 108 patients aged more than 50 years. The maximal rate conducted over AP was lower in patients with AS location than in other locations either in control state (174+/-60 per minute versus 197+/-63 per minute) (p<0.01) or after isoproterenol (206+/-71 versus 248+/-69) (p<0.01). The number of induced reciprocating tachycardia (47% versus 57.5%), atrial fibrillation (15% versus 21%) and malign forms (12% versus 17%) did not differ significantly in patients with AS location and in other patients. Anterograde conduction disappeared spontaneously in three of six patients followed 8+/-1.5 years, and significantly increased in two other patients.

CONCLUSIONS

AS AP location in WPW syndrome was more frequent in children than in adults. The maximal rate conducted over the AP was lower than in other locations. The incidence decreased after 40 years. AS AP location was never noted after 50 years in our population. This disappearance with age should be taken into account for the indications of AS AP ablation.

Catheter-induced mechanical trauma to fast and slow pathways during radiofrequency ablation of atrioventricular nodal reentry tachycardia: incidence, predictors, and clinical implications

BACKGROUND

Data on the incidence and significance of catheter-induced trauma to fast and slow pathways are scarce.

OBJECTIVES

To evaluate the incidence, predictors, and clinical implications of inadvertent catheter-induced mechanical trauma to fast and slow pathways during radiofrequency ablation (RFA) of atrioventricular nodal reentry tachycardia (AVNRT).

METHODS

A total of 901 consecutive patients (aged 9-92 years old) with inducible sustained AVNRT underwent RFA of the slow pathway. All procedures were closely monitored for appearance of catheter-induced mechanical block of fast or slow pathways.

RESULTS

Catheter-induced mechanical trauma to fast and/or slow pathways was observed in 121 (13.4%) patients: 86 (71%) patients had trauma of the fast pathway, three (2.4%) had trauma of the slow pathway, and 32 (26.4%) had trauma of both pathways. Mechanical trauma lasted <1 minute in 87 (72%) patients, 1-30 minutes in 23 (19%) and >30 minutes in 11 (9%). A significantly increased procedure discontinuation rate was observed in patients with mechanical trauma as compared to those with no trauma (P < 0.0001). Young patient age (<35) was a strong predictor for the occurrence of mechanical trauma to AV nodal pathways. No significant difference between the trauma and non-trauma groups was found in respect to the number of catheters used during the procedure, the incidence of AV block, and the need for permanent pacemaker implantation.

CONCLUSIONS

Mechanical trauma to fast and slow pathways during ablation of AVNRT is more common than previously recognized, occurring especially in patients aged <35 years.

Differentiation of narrow QRS complex tachycardia types using the 12-lead electrocardiogram

BACKGROUND

Previous studies have shown that only 80% of narrow QRS supraventricular tachycardia (SVT) types can be differentiated by standard 12-lead electrocardiographic (ECG) criteria. This study was designed to determine the value of some new ECG criteria in differentiating narrow QRS SVT.

METHODS AND RESULTS

120 ECGs demonstrating paroxysmal narrow QRS complex tachycardia (QRS < or = 0.11 ms and rate > 120 beats/min) were analyzed. Forty atrioventricular reciprocating tachycardia (AVRT), 70 atrioventricular nodal reentrant tachycardia (AVNRT), and 10 atrial tachycardia defined with electrophysiologic study (EPS) consisted the study group. Eight surface ECG criteria were found to be significantly different between tachycardia types by univariate analysis. P waves separate from the QRS complex were observed more frequently in AVRT (70%) and atrial tachycardia (80%). Pseudo r' deflection in lead V(1), pseudo S wave in inferior leads, and cycle length alternans were more common in AVNRT (55, 20, and 6%, respectively). QRS alternans was also present during AVRT (28%). ST-segment depression (> or = 2 mm) or T-wave inversion, or both, were present more often in AVRT (60%) than in AVNRT (27%). During sinus rhythm, manifest preexcitation was observed more often in patients with AVRT (42%). When a P wave was present, RP/PR interval ratio > 1 was more common in atrial tachycardia (90%). By multivariate analysis, presence of a P wave separate from the QRS complex, pseudo r' deflection in lead V(1), QRS alternans, preexcitation during sinus rhythm, ST-segment depression > 2 mm or T-wave inversion, or both, were independent predictors of tachycardia type.

CONCLUSIONS

Several new ECG criteria may be useful in differentiation of SVT types. Prediction of mechanism prior to EPS may provide additional benefits concerning the fluoroscopic exposure time and cardiac catheterization procedure.

Mechanical interruption of postinfarction ventricular tachycardia as a guide for catheter ablation

BACKGROUND

Mechanical trauma has been described as a helpful guide for ablation of atrial tachycardias and accessory pathways. In postinfarction ventricular tachycardia (VT), the reentrant circuit is partly endocardial and therefore may be susceptible to catheter trauma.

OBJECTIVES

The purpose of this study was to determine the prevalence and significance of VT termination resulting from catheter trauma.

METHODS

A consecutive series of 39 patients (mean age 68 +/- 7 years, ejection fraction 0.25 +/- 0.02) underwent left ventricular mapping for postinfarction VT. Mapping was performed during 62 hemodynamically tolerated VTs (mean cycle length 451 +/- 88 ms). Only hemodynamically tolerated VTs that did not terminate spontaneously and VTs that were reproducibly inducible were included in the study. VT termination was considered mechanical only if it was not caused by a premature depolarization.

RESULTS

In 13 of 62 VTs (21%) in 8 of 39 patients (21%), either VT terminated during catheter placement at a particular site (n = 7) or a previously reproducibly inducible VT became no longer inducible with the mapping catheter located at a particular site (n = 6). The stimulus-QRS interval was significantly shorter at sites where mechanical trauma affected the reentrant circuit compared with sites having concealed entrainment (102 +/- 56 ms vs 253 +/- 134 ms, P = .003). At the site that was susceptible to mechanical trauma, the pace map was identical or highly similar in 13 of 13 VTs. After radiofrequency ablation at these sites, the targeted VTs were no longer inducible. No patient had recurrence of the targeted VT during a mean follow-up of 15 +/- 11 months.

CONCLUSIONS

Catheter contact at a critical endocardial site can interrupt postinfarction VT or prevent its induction. Radiofrequency ablation at sites of mechanical termination of VT has a high probability of success.

Utility of adenosine 5'-triphosphate in predicting early recurrence after successful ablation of manifest accessory pathways

OBJECTIVES

The purpose of this study was to determine whether administration of adenosine 5'-triphosphate (ATP; 20-40 mg) after successful ablation of accessory pathway (AP) with manifest preexcitation is useful for detecting residual conduction and predicting early recurrences.

BACKGROUND

The reported incidence of recurrence of AP conduction after an initially successful procedure is 5% to 10%. Little information on the variables related to early recurrence has been reported.

METHODS

We prospectively used 108 ATP tests on 100 consecutive patients (66 men, mean age 36 +/- 15 years) with manifest preexcitation. Five minutes after successful ablation, intravenous boluses of ATP at increasing doses were injected until the target effect of second- or third-degree AV block or AP conduction was observed.

RESULTS

The effect of ATP was AV block (negative test) in 82 cases (76%), conduction over previously ablated AP (positive test) in 9 cases (8.3%), and no achievement of target effect (nondiagnostic test) in 17 cases (15.7%). Thirteen early recurrences were observed in 12 patients. In all 9 (100%) patients with positive ATP test and in 4 (4.9%) of the 82 patients with negative ATP test, conduction over the AP recurred (relative risk 20; 95% confidence interval 8-53; P < .000001). The diagnostic accuracy of the test (analyzing the target effect) was 95%, sensitivity 69%, specificity 100%, and positive and negative predictive values 100% and 95%, respectively.

CONCLUSIONS

ATP administration after successful ablation of APs has a high predictive value for early recurrence and may help optimize the duration of the ablation procedure.

Electrocardiographic and Electrophysiologic Characteristics of Midseptal Accessory Pathways

BACKGROUND

The purpose of the present study was to investigate the electrocardiographic and electrophysiologic characteristics of right midseptal (RMS) and left midseptal (LMS) accessory pathways (APs), and to develop a stepwise algorithm to differentiate RMS from LMS APs.

METHODS AND RESULTS

From May 1989 to February 2004, 1591 patients with AP-mediated tachyarrhythmia underwent RF catheter ablation in this institution, and 38 (2.4%) patients had MS APs. The delta wave and precordial QRS transition during sinus rhythm, retrograde P wave during orthodromic tachycardia, and electrophysiologic characteristic and catheter ablation in 30 patients with RMS APs and 8 patients with LMS APs were analyzed. There was no significant difference in electrophysiologic characteristics and catheter ablation between RMS and LMS APs. The polarity of retrograde P wave during orthodromic tachycardia also showed no statistical difference between patients with RMS and LMS APs. The delta wave polarity was positive in leads I, aVL, and V3 to V6 in patients with RMS and LMS APs. Patients with LMS APs had a higher incidence of biphasic delta wave in lead V1 than patients with RMS APs (80% vs. 15%, P=0.012). The distributions of precordial QRS transition were different between RMS APs (leads V2; n = 10, V3; n = 7 and V4; n = 3) and LMS APs (leads V1; n = 1 and V2; n = 4) (P = 0.03). The combination of a delta negative wave in lead V1 or precordial QRS transition in lead V3 or V4 had a sensitivity of 90%, specificity of 80%, positive predictive value of 95%, and negative predictive value of 66% in predicting an RMS AP.

CONCLUSIONS

Delta wave polarity in lead V1 and precordial QRS transition may differentiate RMS and LMS APs.

Multiple accessory pathways in pediatric patients with Wolff-Parkinson-White syndrome

The characteristics of multiple accessory pathways in children have not been previously studied. Records were reviewed of 317 consecutive pediatric patients with Wolff-Parkinson-White syndrome who underwent electrophysiologic study and radiofrequency catheter ablation at our institution. Twenty-eight patients (9%) had multiple pathways (a total of 64 pathways: 21 patients had 2, 6 had 3, and 1 patient had 4 pathways). The locations were left free wall (22 pathways), right free wall (19 pathways), posteroseptal (17 pathways), and anteromidseptal (6 pathways). Of these 64 pathways, 55 were ablated successfully without complications, 5 failed ablation, and 4 fasciculoventricular fibers did not require treatment. Three patients had a newly found pathway at the repeat session. Three patients had atrioventricular nodal reentrant tachycardia and the slow pathway area was modified. One patient had failed initial ablation and had a successful ablation using a 3-dimensional electroanatomic mapping system. Compared with patients with a single pathway, those with multiple pathways exhibited a higher incidence of antidromic tachycardia, a shorter anterograde accessory pathway effective refractory period (<250 ms), a longer fluoroscopic time (65 +/- 43 vs 39 +/- 46 minutes, p <0.05), and a larger number of unsuccessful attempts (9 +/- 16 vs 5 +/- 8, p <0.05). Success rate (92% vs 93%) and recurrence rate (1.7% vs 2.1%) were similar in both groups. This study demonstrates that multiple pathways are not rare in pediatric patients and that multiple pathways contrast with a single pathway in a variety of conduction properties.

Characteristics and radiofrequency catheter ablation of septal accessory atrioventricular pathways

Septal accessory AV pathways are located in the complex AV septal space that also contains the specialized conduction system. They have unique electrocardiographical and electrophysiological characteristics to be differentiated from free-wall accessory pathways. Some of the septal pathways have AV nodelike conduction properties and produce a similar activation sequence in the retrograde conduction. Several methods have been developed to distinguish them from AV nodal pathways. Radiofrequency catheter ablation using the titration method and endocardial approach without entrance into the coronary sinus is effective in eliminating most of the septal accessory pathways without impairment of AV conduction. However, some posteroseptal accessory pathways may require energy application inside the coronary sinus, thus information of the coronary sinus anatomy is important for preventing complication.

Catheter-induced mechanical trauma to accessory pathways during radiofrequency ablation: incidence, predictors and clinical implications

OBJECTIVES

To evaluate the incidence, predictors and clinical implications of nonintentionally catheter-induced mechanical trauma to accessory pathways during radiofrequency ablation procedures.

BACKGROUND

Data on the incidence and significance of catheter-induced trauma to accessory pathways are scarce.

METHODS

Consecutive patients (n = 381) undergoing radiofrequency ablation of accessory pathways at two different institutions were closely monitored for appearance of mechanical block of accessory pathways during catheter manipulation.

RESULTS

Mechanical trauma to accessory pathways was observed in 37 (9.7%) patients. According to a multivariate analysis, the only independent variable associated with this phenomenon was the anatomical pathway location (p = 0.0001). The incidence of trauma of either right anteroseptal (38.5%) or right atriofascicular pathways (33.3%) was significantly greater than that of pathways (< or =10%) at all remaining locations (p < 0.0001). The duration of conduction block observed ranged from < or =1 min to >30 min in 19% and 35% of patients, respectively. "Immediate" application of radiofrequency pulses at sites of mechanical block (<1 min after occurrence) was associated with a 78% long-term success rate at follow-up. This contrasted with a 25% long-term success rate in patients in whom pulses were delivered 30 min after occurrence of block ("delayed pulses"). Finally, in 24% of patients persistent trauma-induced conduction block led to discontinuation of the ablation procedure.

CONCLUSIONS

Trauma to accessory pathways is more common than previously recognized and frequently results in prolongation or discontinuation of the ablation procedure and in lower success rates. The only independent predictor of catheter-trauma to accessory pathways is the pathway location.

Clinical recurrences after successful accessory pathway ablation: the role of "dormant" accessory pathways

INTRODUCTION

Recurrence of clinical symptoms after radiofrequency catheter ablation of an accessory atrioventricular pathway (AP) may be due to the late manifestation of an additional AP that was not detected during the initial ablation session. It was the purpose of this study to elucidate the phenomenon of these "dormant" APs.

METHODS AND RESULTS

Of 1280 consecutive patients who underwent radiofrequency catheter ablation of an AP, 54 patients (4.2%) developed clinical symptoms postablation, necessitating a repeat ablation session. Recurrence of conduction over the AP targeted at the initial ablation session was found in 45 patients, whereas in the other 9 patients (0.7%) the manifestation of a previously unnoticed AP had caused symptom recurrence. Retrospective analysis of the data from these patients' ablation sessions revealed that the late manifesting AP was ablated at a site clearly different from that of the initially targeted AP, and that the manifestation of conduction over a previously "dormant" AP occurred significantly later than the recovery of a presumably ablated AP. Seven (78%) of the 9 "dormant" APs were concealed, and none exhibited decremental conduction properties.

CONCLUSION

The incidence of clinical recurrences mediated by the late manifestation of conduction over a previously "dormant" AP is low. The lack of an anatomic vicinity of these predominantly concealed APs with the initially targeted AP and the lack of evidence for their presence during the initial ablation session suggest intermittent conduction as the most likely explanation for their late manifestation.

Role of the surface electrocardiogram in the diagnosis of patients with supraventricular tachycardia

In this era of interventional electrophysiology, the accuracy of the electrocardiogram in diagnosis of supraventricular tachycardia could be improved by detailed endocardial mapping and confirmed by results of radiofrequency catheter ablation. This article describes the electrocardiographic characteristics for different types of supraventricular tachycardia: atrial fibrillation, atrial flutter, atrial tachycardia, atrioventricular reciprocating tachycardia using an accessory pathway, and atrioventricular node reentrant tachycardia. Several limitations, including the identification of P wave morphologies and polarities and separation between the terminal part of T wave and P wave during tachycardia, should be resolved before an accurate algorithm of the 12-lead surface electrocardiogram is developed for the diagnosis of supraventricular tachycardia.

A new electrocardiographic algorithm using retrograde P waves for differentiating atrioventricular node reentrant tachycardia from atrioventricular reciprocating tachycardia mediated by concealed accessory pathway

OBJECTIVES

The purpose of this study was to use an electrocardiographic (ECG) algorithm, derived from the results of radiofrequency ablation, to discriminate atrioventricular node reentrant tachycardia (AVNRT) from atrioventricular reciprocating tachycardia (AVRT) and to localize a concealed accessory pathway, prospectively.

BACKGROUND

Information about ECG criteria for differentiating AVNRT from AVRT is limited and has not been confirmed by surgical or catheter ablation.

METHODS

Four hundred six ECGs (obtained from 406 different patients) that demonstrated narrow QRS complex (< 0.12 s) supraventricular tachycardia with an RP' interval less than the P'R interval or pseudo r' wave in lead V1 or pseudo S wave in inferior leads, or both, were examined, and the results were confirmed by radiofrequency catheter ablation. The initial 226 ECGs were analyzed to develop a stepwise algorithm, and the subsequent 180 ECGs were prospectively evaluated by the new algorithm.

RESULTS

The presence of a pseudo r' wave in lead V1 or a pseudo S wave in leads II, III, aVF indicated anterior-type AVNRT with an accuracy of 100%. With the difference of RP' intervals in leads V1 and III > 20 ms, posterior-type AVNRT could be differentiated from AVRT utilizing a posteroseptal pathway with a sensitivity of 71% (95% confidence interval [CI] 55% to 89%), a specificity of 87% (95% CI 67% to 97%) and a positive predictive value of 75% (95% CI 56% to 91%). According to the polarity of retrograde P waves in leads V1, II, III, aVF and I during AVRT, the concealed accessory pathway could be localized to one of the nine regions on the atrioventricular annuli with an accuracy of 75% (for a right midseptal pathway) to 93.8% (for a left posterior pathway). Overall, the new algorithm had an accuracy of 97.8% in discriminating AVNRT from AVRT and 88.1% in localizing a concealed accessory pathway, prospectively. Prediction was incorrect in only 15 patients (9.1%).

CONCLUSIONS

The new ECG algorithm derived from the analysis of retrograde P waves during tachycardia could provide a criterion for differential diagnosis between AVNRT and AVRT and for predicting the location of concealed accessory pathways.

Long-term results of radiofrequency catheter ablation in patients with multiple accessory pathways

Information on the long-term results of radiofrequency catheter ablation in a large group of patients with multiple accessory pathways (APs) was not available. This study included 858 patients with Wolff-Parkinson-White syndrome who underwent electrophysiologic study and radiofrequency catheter ablation: 73 patients (8.5%) had multiple APs. Sixty-six patients had 2 APs, 5 had 3 APs, 1 had 4 APs, and 1 had 5 APs. The most common combination pattern of these pathways were concealed APs (38 patients, 52%). Localization of accessory pathways showed a higher incidence of right free wall (22% vs 11%, p < 0.05), anteroseptal, and midseptal APs (9% vs 5%, p < 0.05) in patients with multiple APs than in patients with 1 AP. The most common anatomic sites for multiple APs were 2 APs in the left wall (21 patients, 28%). Although the success rate was similar (98% vs 99%, p > 0.05), procedure time (3.1 +/- 1.2 vs 2.0 +/- 1.1 hours, p < 0.05) and radiation exposure time (48 +/- 26 vs 29 +/- 19 minutes, p < 0.05) were longer in patients with multiple APs. The recurrence rate was higher in patients with multiple APs (9.5% vs 2.5%, p < 0.05), and the most common site of recurrent APs was in the left free wall (7.2%); in contrast, it was in the right free wall in patients with 1 AP. These findings demonstrated that a high success rate of radiofrequency catheter ablation was found in patients with multiple APs; however, the higher recurrence rate in patients with multiple APs should be considered.

Catheter-induced atrioventricular nodal block during radiofrequency ablation

This study examined the incidence and significance of catheter-induced atrioventricular nodal block (AVNB) during a radiofrequency ablation procedure that uses stiff large-tip steerable ablation catheters. AVNB was noted in 10 (1.6%) of 613 consecutive patients undergoing radiofrequency ablation therapy for atrioventricular nodal (AVN) reentrant tachycardia (592 patients) or atrioventricular reentry tachycardia incorporating a midseptal accessory pathway (21 patients). Of these 10 patients, 9 underwent AVN modification for AVN reentrant tachycardia and 1 for ablation of a midseptal accessory pathway. One patient had two episodes of AVNB during two sessions undertaken because of recurrence of tachycardia. No patient had a preexisting conduction defect before the study. In all 10 patients, AVNB was transient, and it lasted for a mean of 9.1 +/- 19 minutes. It occurred during positioning of the ablation catheter in the junctional area before (8 patients) or after (2 patients) the start of radiofrequency current applications. Complete AVNB was noted on six occasions, second-degree AVNB on four occasions, and first-degree AVNB on one occasion. All blocks were associated with narrow QRS ventricular beats and with a site of block proximal to the His bundle. The mean ventricular heart rate during AVNB was 60 +/- 23 beats/min. Two patients had transient asystole, with one having loss of consciousness. No patient required special treatment for heart block. One-to-one conduction resumed after repositioning of the catheters, and the subsequent ablation procedure was successfully completed in 8 of the 10 patients. During a follow-up of 20 +/- 12 months, none of the patients had severe dizziness or syncope, and none required implantation of a permanent pacemaker. In conclusion, transient AVNB due to mechanical injury occurs during positioning of a stiff large-tip steerable ablation catheter in the junctional area. Delivery of radiofrequency current to the site that provokes catheter-induced AVNB should be avoided.

Permanent mechanical catheter ablation of an accessory pathway in a child

Permanent mechanical ablation of an accessory atrioventricular pathway was observed in an infant during intracavitary electrophysiological mapping. The persistent lack of preexcitation was confirmed during a 15-month follow-up period.

Role of catheter-induced mechanical trauma in localization of target sites of radiofrequency ablation in automatic atrial tachycardia

OBJECTIVES

We compared the efficacy of two different mapping techniques in identifying the ablation site for atrial tachycardia. Moreover, we evaluated the additive positive predictive value of mechanical interruption of atrial tachycardia to reduce the number of ineffective radiofrequency applications.

BACKGROUND

Radiofrequency catheter ablation has been suggested as a highly effective technique to treat drug-resistant atrial tachycardia. However, irrespective of the mapping technique utilized, success was most often achieved with a large number of radiofrequency applications.

METHODS

Forty-five patients with atrial tachycardia underwent radiofrequency catheter ablation. Mapping techniques included identification of earliest atrial activation and pace-mapping concordant sequence.

RESULTS

Atrial tachycardia was successfully treated in 42 (93.3%) of 45 patients with a mean of 3.9 radiofrequency pulses/patient. An interval between the onset of the intracavitary atrial deflection and the onset of the P wave during atrial tachycardia (AP interval) > or = 30 ms (p < 0.001) and pace-mapping concordant sequence (p = 0.01) were all significant predictors of outcome. An AP interval > or = 30 ms and a pace-mapping concordant sequence were highly sensitive (92.8%, 95% confidence interval [CI] 80.5% to 98.5%; 85.7%, 95% CI 71.5% to 94.6%, respectively) but less specific (47.8%, 95% CI 37.9% to 58.2%, 36.8%, 95% CI 27.6% to 47.2%, respectively) in identifying the site of ablation. By using atrial tachycardia mechanical interruption combined with the AP interval >30 ms or the pace-mapping concordant sequence, we obtained a specifically of 76.5% (95% CI 66.4% to 84.0%) and 73.5% (95% CI 63.2% to 81.4%), respectively, and a positive predictive value of 49.2% and 44.6%, respectively.

CONCLUSIONS

An AP interval > or = 30 ms and a pace-mapping concordant sequence were reliable mapping features for predicting the outcome of the ablation procedure. Mechanical interruption of atrial tachycardia improved the specificity and positive predictive value of these two mapping techniques.

Electrocardiographic and electrophysiologic characteristics of anteroseptal, midseptal, and para-Hisian accessory pathways. Implication for radiofrequency catheter ablation

STUDY OBJECTIVE

To investigate the ECG characteristics, the electrophysiologic properties, and an effective radiofrequency catheter ablation technique in patients with septal accessory pathways.

PATIENTS

Forty-six consecutive subjects with septal accessory pathways located in the anteroseptal, midseptal, and para-Hisian areas.

DESIGN AND INTERVENTIONS

ECGs obtained during sinus rhythm and orthodromic tachycardia, conduction properties obtained from electrophysiologic study, and results of two different ablation techniques were analyzed.

MEASUREMENTS AND RESULTS

(1) Twenty-four (52.2%) had manifest preexcitation and 15 (32.6%) had multiple accessory pathways; (2) midseptal pathways could be differentiated from anteroseptal and para-Hisian pathways by a negative delta wave in lead III and a biphasic delta wave in lead aVF during sinus rhythm, and a negative retrograde P wave in two inferior leads during orthodromic tachycardia; (2) midseptal pathways had better antegrade conduction properties and a significantly higher incidence (61.5%) of inducible atrial fibrillation; (4) radiofrequency catheter ablation using lower energy (20+/-6 W) had a comparable effect to ablation using higher energy (36+/-5 W), but without impairment of atrioventricular (AV) node conduction or development of AV block; and (5) during the follow-up period of 26+/-14 months (range, 5 to 54 months), three (6.5%) patients had recurrence.

CONCLUSIONS

Midseptal accessory pathways had ECG and electrophysiologic characteristics that were distinctive from those of anteroseptal and para-Hisian pathways. Catheter ablation of these septal pathways using low radiofrequency energy was safe and effective.

The evolution of platelet aggregability in patients undergoing catheter ablation for supraventricular tachycardia with radiofrequency energy: the role of antiplatelet therapy

Forty-two consecutive patients were checked for profiles of platelet aggregability before, during, and 10 and 30 minutes after catheter ablation. They were randomized into Group A (n = 20) who accepted intravenous aspirin (in 0.015 g/kg body weight) and Group P (n = 22) who accepted only placebo treatment. Blood samples were drawn from ascending aorta (Ao) and main pulmonary artery (MPA) simultaneously at each time period. In Group P, the EC50 of substrate induced platelet aggregability decreases significantly during (for ADP, from 1.72 to 0.78 mumol/L for samples from Ao, P < 0.0001; and from 1.68 to 0.69 mumol/L for MPA, P < 0.0001; for collagen, from 2.26 to 1.34 micrograms/mL for Ao, P < 0.005, and from 2.40 to 1.64 micrograms/mL, P < 0.0001) and 10 minutes after successful ablation (for ADP, to 0.70 mumol/L for Ao, P < 0.000, and to 0.61 mumol/L for MPA, P < 0.0001; for collagen, to 1.54 micrograms/mL for Ao, P < 0.01, and to 1.63 micrograms/mL, P < 0.0001), and then returned to baseline levels 30 minutes later (all P = NS) compared with comparative baseline levels. The levels of thromboxane B2 (TXB2) had the similar evolution. The evolution of platelet aggregability profiles was not associated with total energy dose, duration of energy application, duration of procedure, impedance, and ablation site. However, there were moderate positive correlations between the TXB2 levels and tip temperatures (r = 0.56, P < 0.05 for Ao and r = 0.65, P < 0.01 for MPA). These results suggest that increased platelet aggregability can occur during and 10 minutes after radiofrequency current ablation and antiplatelet therapy can maintain "flat" response of platelet aggregability to radiofrequency energy, which may provide possible benefits in preventing the occurrence of the complication.

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.

An accurate stepwise electrocardiographic algorithm for localization of accessory pathways in patients with Wolff-Parkinson-White syndrome from a comprehensive analysis of delta waves and R/S ratio during sinus rhythm

Prediction of accessory pathway location before radio-frequency ablation has become increasingly important for patients with Wolff-Parkinson-White syndrome. However, existing electrocardiographic (ECG) criteria for localization of accessory pathways have several limitations, and the polarity of delta waves has not been well defined. In the present study, 369 patients with a single anterogradely conducting accessory pathway who underwent successful radiofrequency ablation were included. The polarity of delta waves was defined and categorized in detail, and various ECG characteristics of the most preexcited QRS complexes were examined and compared with QRS complexes after successful ablation in the initial 182 patients, which included morphology and polarity of delta waves, initial 20, 40, and 60 ms segments of the preexcited QRS complex, R/S ratio in the precordial leads, R/S ratio in the frontal leads, delta wave axis in the frontal plane, polarity of delta waves in the frontal leads, and polarity of delta waves in the precordial leads. The polarity of the initial 40 ms segment of the most preexcited QRS complexes in each of the frontal leads, and the polarity of the initial 60 ms segment of the most preexcited QRS complex in each of the precordial leads proved to be the best representatives of delta wave polarity in the respective leads.(ABSTRACT TRUNCATED AT 250 WORDS)