Single Accessory Pathway Research Articles

Pediatric Radiofrequency Catheter Ablation: Results of Initial 100 Consecutive Cases Including Congenital Heart Anomalies

Radiofrequency catheter ablation (RFCA) has recently become a management option for pediatric tachycardia. We reviewed the records of a total of 100 patients (aged 10 months to 19 yr) who had undergone RFCA, from March 2000 to June 2004. Types of arrhythmia (age, acute success rate) were as follows: atrioventricular reentrant tachycardia (AVRT, 9.0±3.7 yr, 66/67), atrioventricular nodal reentrant tachycardia (AVNRT, 13±2.5 yr, 16/16), ectopic atrial tachycardia (6.4±3.3 yr, 5/5), junctional ectopic tachycardia (10 month, 1/1), ventricular tachycardia (12±4.9 yr, 6/6), postsurgical intraatrial reentrant tachycardia (15.6±4.1 yr, 2/3), twin node tachycardia (4 yr, 0/1), and His bundle ablation (9 yr, 1/1). The age of AVNRT was older than that of AVRT (p=0.002). Associated cardiac disease was detected in 17 patients, including 6 univentricular patients, and 3 Ebstein's anomaly patients. RFCA for multiple accessory pathways required longer fluoroscopic times than did the single accessory pathway (53.9±4.8 vs. 36.2±24.1 min; p=0.03), and was associated with a higher recurrence rate (3/9 vs. 3/53; p=0.03). Regardless of the presence or absence of cardiac diseases, the overall acute success rate was 97% without major complications, the recurrence rate was 8.2%, and the final success rate was 97%. This experience confirmed the efficacy and safety of RFCA in the management of tachycardia in children.

Radiofrequency ablation of multiple accessory pathways.

The aim of the study was to review the clinical and electrophysiological characteristics and results of radiofrequency catheter ablation in patients with multiple accessory pathways to compare them with those of patients with single accessory pathways. Electrophysiological study and radiofrequency catheter ablation were performed in 1010 consecutive cases with Wolff Parkinson White Syndrome. Presence of multiple accessory pathways was documented in 31 patients (3.1%); 30 had two, and 1 had three accessory pathways. Of the 63 accessory pathways, 42 were manifest and 21 concealed. Nine patients had Ebstein's anomaly associated with atrioventricular bypass tracts. The most common combination was right posteroseptal with right free wall bypass tracts (15 patients with 30 accessory pathways). Fifty-one of the sixty-three accessory pathways (81%) were ablated successfully without complications. The duration of the procedure was 100 +/- 58 min and the fluoroscopic time 40 +/- 17 min. A follow up of 5 +/- 3 years after ablation, demonstrated recurrences of six accessory pathways (9.5%). In conclusion, patients with multiple accessory pathways can be treated by radiofrequency ablation in only one session with a high success rate although slightly less than that in patients with a single accessory pathway (81% vs 93%, P<0.01).

Analysis of age of onset of accessory pathway-mediated tachycardia in men and women

diated tachycardia. 1‐4 However, a detailed analysis of the inter-relationships between gender, accessory pathway location, and the age of onset of accessory pathway-mediated tachycardia has been lacking. Therefore, the purpose of this study was to analyze the interactions between gender, accessory pathway location, and the age of onset of accessory pathwaymediated tachycardia. ••• The subjects of this study were 910 patients who underwent an electrophysiologic study at the University of Michigan Medical Center and met the following selection criteria: a history of symptomatic paroxysmal tachycardia; the ability to recollect the age of onset of the tachycardia; a single accessory pathway; an inducible accessory pathway-mediated tachycardia in the electrophysiology laboratory; and successful radiofrequency ablation of the accessory pathway. Patients who had 1 mechanism of tachycardia or 1 accessory pathway were excluded from the study. There were 536 men (59%) and 374 women (41%), and their mean age at the time of the electrophysiologic study was 37 15 years ( SD; range 10 to 84 years). The location of the accessory pathways was classified as being left sided, right sided, or septal, according to the site at which successful radiofrequency ablation was achieved. Among the 910 accessory pathways, 541 (59%) were left sided, 131 (14%) were right sided, and 238 (26%) were septal. In 328 patients (36%), the accessory pathway was concealed and capable only of retrograde conduction, and in the remaining 64% of patients, the accessory pathway was manifest and conducted in the anterograde direction. Continuous variables are expressed as mean 1 SD. Student’ s t test was used to compare 2 groups. Analysis of variance was used when comparisons involved 2 groups. When group differences were found, 1-way analysis of variance was followed by the

Quantitative effects of functional bundle branch block in patients with atrioventricular reentrant tachycardia

Changes in the retrograde conduction time (ventriculoatrial [VA]) interval during functional bundle branch block (BBB) have been used to separate septal from free wall accessory pathways (APs), but different values of the VA interval prolongation (ΔVA) have been described in different reports. A total of 95 patients with single nondecremental APs who developed BBB during atrioventricular reentrant tachycardia were studied. Free wall APs were found in 60 patients, and 35 had septal APs. For patients with free wall APs, complete and incomplete BBB ipsilateral to the atrial insertion site of APs were observed in 39 of 60 patients (65%) and 31 of 60 patients (52%), respectively. For patients who had both complete (QRS ≥120 ms) and incomplete (QRS <120 ms) BBB during atrioventricular reentrant tachycardia, ΔVA for patients with complete BBB was significantly greater than in those with incomplete BBB, 59 ± 19 ms versus 30 ± 11 ms, p <0.001. For patients with septal APs and complete and incomplete BBB during tachycardia, the mean ΔVA for those with complete BBB was 31 ± 20 ms and was significantly longer than in patients with incomplete BBB (14 ± 6 ms), p <0.001. There was no significant difference in ΔVA between those with free wall APs and incomplete BBB compared with those with septal APs and complete BBB. The criteria of QRS ≥120 ms associated with ΔVA ≥40 ms served to best separate free wall from septal APs with a sensitivity of 88% and a specificity of 89%. Left anterior fascicular block was associated with marked lengthening of ΔVA for those with left free wall APs, whereas a left posterior fascicular block pattern resulted in a marked increase in the ΔVA for patients with posteroseptal APs. In the absence of fascicular block patterns, a ΔVA ≥40 ms provides strong evidence of a free wall AP, with a sensitivity of 95% and a specificity of 100%. The left posterior fascicle appears to provide predominant innervation of the posterior septum.

Radiofrequency application to the posteroseptal region alters retrograde accessory pathway activation.

Radiofrequency applications to the posteroseptal region can ablate the atrioventricular accessory pathway residing in this area. In conjunction with the adjacent anatomic structures, however, ablative lesions which do not effectively ablate the accessory pathway could markedly alter retrograde atrial activation sequence and confound interpretation of further mapping of an accessory pathway. Electrophysiologic studies, endocardial activation mapping and radiofrequency catheter ablation were undertaken in three patients with recurrent supraventricular tachycardia. Patients were initially thought to have a single posteroseptal accessory pathway; earliest ventrioatrial activation during tachycardias and during ventricular pacing was at the coronary sinus ostium, but initial radiofrequency applications were unsuccessful to ablate the pathway. After initial radiofrequency applications to the posteroseptal region, the earliest retrograde atrial activation changed to the right atrial free wall in two patients. Additional radiofrequency application to the posteroseptal area was able to ablate the single posteroseptal accessory pathway in one patient. Radiofrequency application to the right atrial free wall was required to stop tachycardia initiation in other patient. The third patient was suspected of having a slow-slow atrioventricular nodal reentry tachycardia. Radiofrequency application to the posteroseptal area changed the earliest retrograde atrial activation to the distal coronary sinus recording site, mimicking an accessory pathway at the left atrial free wall. Radiofrequency application to the anteroseptum was able to ablate the concealed accessory pathway. Radiofrequency applications to the posteroseptal region can markedly alter retrograde atrial activation, thereby confounding further mapping of the accessory pathway.

Clinical and Electrocardiographic Variables Can Predict Atrial Fibrillation in Patients with Atrioventricular Accessory Pathways

Background:Risk stratification of sudden death in patients with Wolff-Parkinson-White syndrome is based on the refractory period of the atrioventricular accessory pathway and the probability of spontaneous atrial fibrillation. Risk stratification based on invasive studies does not seem cost-effective in the radiofrequency ablation era, and, although sensitive, noninvasive tests are not used because of their low specificity. We sought to determine whether clinical and electrocardiographic variables can predict spontaneous atrial fibrillation in patients with an accessory pathway. Methods:We studied 420 consecutive patients treated by radiofrequency catheter ablation who had a single atrioventricular accessory pathway and the Influence of four variables: age, gender, location of the accessory pathway as determined by the site of successful radiofrequency ablation, and the presence of a manifest accessory pathway in the ECG was analyzed by multiple logistic regression analysis and a chi-square test. The development model, comprised of data from the first 359 patients, included 58 patients with spontaneous atrial fibrillation and 301 patients without spontaneous atrial fibrillation during follow-up. The likelihood ratio derived from the development model was validated in the last 61 patients. Results:Patients with spontaneous atrial fibrillation occurring before accessory pathway ablation were more often male and were older than those without atrial fibrillation. Atrial fibrillation occurred more frequently in manifest than in concealed accessory pathways, and the presence of posteroseptal accessory pathway strongly correlated with spontaneous atrial fibrillation. Conclusion:The probability of spontaneous atrial fibrillation was higher in men with a manifest posteroseptal accessory pathway and increased with age. A.N.E. 2000;5(1):45–52

Prediction of accessory pathway locations in Wolff-Parkinson-White syndrome with body surface potential Laplacian maps . A simulation study.

An electrocardiographic computer simulation was conducted to study the feasibility of predicting accessory pathway locations in Wolff-Parkinson-White (WPW) syndrome with body surface potential Laplacian maps. Three-dimensional, realistically-shaped heart and torso models were used. Ten accessory pathways (APs) around the atrioventricular ring corresponding to Gallagher et al. were set in the heart model, and body surface Lapacian and potential maps of WPW syndrome with single or multiple APs were simulated and compared to each other. In simulations with a single AP in the anterior walls, the maximum-minimum pairs in Laplacian maps appeared to be similar to those in potential maps with respect to their locations and orientations, but the maximum-minimum pairs in Laplacian maps were sharper and more localized than in potential maps. In simulations with a posterior AP or multiple APs, the maximum-minimum pairs in the Laplacian maps showed features correlative to the AP locations, but no such features were found in potential maps. These results suggest the possibility of using Laplacian maps, as a non-invasive method for predicting accessory pathways locations in WPW syndrome.

Identification of fiber orientation in left free-wall accessory pathways: implication for radiofrequency ablation.

Previous reports on the anatomic discordance between atrial and ventricular insertion sites of left free-wall accessory pathways were limited and their findings were controversial. The purpose of this study was to explore the fiber orientation and related electrophysiologic characteristics of left free-wall accessory pathways. The study population comprised 96 consecutive patients with a single left free-wall accessory pathway (33 manifest and 63 concealed pathways), who underwent electrophysiologic study and radiofrequency catheter ablation using the retrograde ventricular approach. The atrial insertion site of the accessory pathway was defined from the cinefilms as the site with the earliest retrograde atrial activation bracketed on the coronary sinus catheter during tachycardia, and the ventricular insertion site was defined as the site where successful ablation of the pathway was achieved. Forty-two patients (44%) had their atrial insertion sites 5-20 mm (10 +/- 3 mm) distal to the ventricular insertion sites (proximal excursion), 30 (31%) patients had their atrial insertion sites 5-20 mm (12 +/- 3 mm) proximal to the ventricular insertion sites (distal excursion), and 24 (25%) patients had directly aligned atrial and ventricular insertion sites. Retrograde conduction properties, including 1:1 VA conduction and effective refractory period, were significantly poorer in the pathways with proximal excursion (302 +/- 67, 285 +/- 61 ms respectively) than in those with distal excursion (264 +/- 56, 250 +/- 48 ms respectively) or direct alignment (272 +/- 61, 258 +/- 73 ms respectively). Accessory pathways at the more posterior location had a significantly higher incidence of proximal excursion (P = 0.006), and those at the more anterior location had a higher incidence of distal excursion (P = 0.012). In conclusion, a wide variation in fiber orientations and related electrophysiologic characteristics was found in left free-wall accessory pathways. This may have important clinical implications for radiofrequency ablation.

Paradox of accessory pathway block after radiofrequency ablation in patients with the Wolff-Parkinson-White syndrome.

Although pacing technique has demonstrated that the most common site of conduction block in a manifest accessory pathway (AP) was between the AP and the ventricle, most of the block sites have been found to be between the atrium and AP after successful radiofrequency ablation. Furthermore, the block site in a concealed AP after successful radiofrequency catheter ablation has not been reported in the literature, and comparisons between a manifest and concealed AP have not been performed. This study included 219 consecutive patients undergoing successful radiofrequency catheter ablation of a single AP. AP potential was recorded at the successful target site in 76 of 92 (82.6%) patients with manifest APs, and in 99 of 127 (77.9%) patients with concealed APs. All the left-sided APs (including left posteroseptal APs) were ablated by a ventricular approach, and right-sided APs (including anteromidseptal and right posteroseptal APs) were ablated by an atrial approach. The site of conduction block was determined by analyzing and comparing the local electrograms recorded before and after radiofrequency ablation at successful ablation sites. Conduction block of manifest APs was between the atrial-AP (A-AP) in 69 patients (75%) and between the AP-ventricle (AP-V) interface in 7 patients (7.6%), whereas the conduction block of concealed APs occurred between the AP-V in 90 patients (70.9%) and between the A-AP interface in 9 patients (7.1%). Neither the preablation electrogram nor electrophysiologic characteristics of APs predicted the site of conduction block. Furthermore, neither the location of the APs nor the position of the ablation catheter affected the block site. It was concluded that the most common site of conduction block during successful radiofrequency catheter ablation of a manifest and concealed AP was between the A-AP and AP-V interface, respectively, and the impedance mismatch theory explained only part of the findings.

Transesophageal echo phase imaging for localizing accessory pathways during adenosine-induced preexcitation in patients with the Wolff-Parkinson-White syndrome

Transesophageal phase images and precordial electrocardiograph (ECG) were used to localize accessory pathways during adenosine-induced preexcitation in 30 patients (18 men, mean age ± SD 33 ± 14 years) undergoing endocardial mapping for suspected Wolff-Parkinson-White syndrome. Digitized 2-dimensional echocardiographic cine loops were mathematically transformed using a first harmonic Fourier algorithm before and after catheter ablation. Endocardial mapping found single accessory pathways with anterograde conduction in 20 patients, concealed pathways in 7, and atrioventricular reentry circuits in 3 patients. At baseline, precordial ECG correctly localized 8 pathways (40%) with anterograde conduction and predicted 5 adjacent locations (25%), but findings were normal in 7 patients (35%). Phase imaging correctly identified only 3 pathway locations (15%), findings were normal in 15 (75%), and could not be obtained in 2 patients (10%). Adenosine augmented manifest but minimal preexcitation in 9 patients and unmasked latent preexcitation in 7. In 4 patients, preexcitation was already maximal at baseline. During adenosine-augmented preexcitation, ECG correctly identified 13 locations (65%), but still predicted 7 adjacent locations (35%). However, phase imaging correctly identified 15 locations (75%) and predicted only 3 adjacent locations (15%). All midseptal (n = 2) and anteroseptal (n = 2) locations were correctly identified by phase imaging, but none by ECG. On follow-up studies in 16 patients, successful catheter ablation (n = 13) was equally well confirmed by ECG and phase imaging. Therefore, transesophageal echocardiographic phase imaging during adenosine-induced preexcitation is a readily available and safe procedure that appears clinically most useful for identifying septal pathways.

A fast and reliable algorithm to localize accessory pathways based on the polarity of the QRS complex on the surface ECG during sinus rhythm.

Many criteria have been published to localize accessory pathways from the 12-lead ECG during sinus rhythm. This study analyzed whether the localization of an accessory pathway could be predicted by using the polarity of the QRS complex during sinus rhythm on the surface ECG, instead of the delta wave polarity as used in many reports. The ECGs of 140 patients with an overt and single accessory pathway were evaluated. Eight localizations were taken into account. The precise location was previously known from successful radiofrequency ablation sites. In 128 patients (92%), the new algorithm allowed an accurate diagnosis of the site of implantation of the accessory pathway. Analysis of the polarity of the QRS complex on five electrocardiographic leads provides an easy, fast and reliable way to localize accessory pathways during sinus rhythm.

777-5 The Relationship Between Impedance and Temperature During Radiofrequency Ablation of Accessory Pathways

Temperature monitoring is a useful tool for radiofrequency (RF) ablation of accessory pathways (AP), but this technology is not universally available and is not suitable for some catheter designs. Impedance monitoring is also helpful and prior studies in humans have demonstrated that an impedance fall of 20 ohms is predictive of coagulum formation or a loss of AP conduction. The purpose of this study was to prospectively quantitate the correlation between impedance and temperature during RF ablation of APs. Thirty-three consecutive patients, each with a single AP, underwent RF ablation using a thermistor ablation catheter. Temperature and impedance were continually recorded during each RF application. The initial and final temperatures and impedance measurements for 319 applications of RF energy were analyzed. The initial and final impedance and temperature measurements were 109 ± 17 ohms and 102 ± 17 ohms (p &lt; 0.000t). and 37 ± 1°C and 57 ± 11°C (p &lt; 0.0001). Among the 319 applications of RF energy, 158 were associated with ≥20°C increase in tissue temperature. There were 10 applications of RF energy associated with coagulum formation. A ≥20°C increase in tissue temperature was observed in 84 of 104 applications associated with a 5–10 ohm decrease in impedance (81% positive predictive value and 93% negative predictive value). The mean change in impedance for applications associated with and without coagulum formation was–19 ± 7 ohms and –6 ± 6 ohms (p &lt; 0.0001), respectively, and was never less than 12 ohms. In conclusion, successful tissue heating without coagulum formation can be achieved by titrating the power to achieve a 5–10 ohm decrement in impedance. Impedance decrements beyond 10 ohms increase the likelihood of excessive tissue heating and coagulum formation.

The effects of accumulated experience on radiofrequency ablation of accessory pathways.

Increasing experience in radiofrequency ablation for accessory pathways appears to reduce the procedure time, radiation time and radiofrequency pulse number, and results in a higher success rate. However, the effect of a learning curve on this procedure from the perspective of location and conduction direction of accessory pathways has not been reported before. The purpose of this study was to determine the effect of accumulated experience on the outcomes of radiofrequency ablation for accessory pathways and on the duration of the procedure parameters by analyzing the results of a dedicated ablation team. The first 512 patients with a single accessory pathway treated in this laboratory were included for analysis of the procedure parameters with respect to locations and conduction directions of accessory pathways. The results showed that the average procedure time, radiation time, and radiofrequency pulse number differed significantly among the different subgroups (left free wall, right free wall, posteroseptal and anteromidseptal location; manifest or concealed conduction). All subgroups except the anteromidseptal pathways showed a significant improvement of the procedure parameters with increased ablation experience. Although the initial rate of improvement was similar among the different subgroups, the rate of improvement in left free wall pathways nearly reached a plateau after 120 ablation procedures. Thus it was concluded that a certain number of ablation procedures was necessary before achievement of a high success rate with shorter procedure and radiation times and a lower radiofrequency pulse number.

Radiofrequency catheter ablation of septal accessory atrioventricular pathways.

Septal accessory atrioventricular pathways are recognised as being more difficult to ablate than pathways in other locations. This paper describes an experience of 48 consecutive patients with septal accessory pathways who had catheter ablation with radiofrequency current. There were 28 male and 20 female patients, mean (SD) age 35 (17). 43 patients had a single accessory pathway and 5 patients had multiple accessory pathways. Pre-excitation was present in 37 patients, and 11 patients had concealed accessory pathways. 21 patients had had a previous electrophysiological study. Catheter ablation was undertaken with radiofrequency current delivered by a standard unipolar technique or by delivery of current across the septum (the bipolar technique). The median total procedure time was 167 (83) minutes including a 30-40 minute observation period after the abolition of conduction by the accessory pathway. The median total fluoroscopic time was 56 (30) minutes. 42 (88%) out of 48 patients had successful ablation of the pathway during the first session. In the six patients in whom the procedure failed, five had a midseptal pathway and one had a right anteroseptal pathway. A second attempt at ablation was made in two patients and succeeded in both. In total, 49 accessory pathways were successfully ablated in 44 (92%) out of 48 patients. The bipolar technique was used in 11 patients and succeeded in 10 patients. Standard unipolar current delivery had previously failed in seven of the 11 patients. Complications developed in two patients with a mid septal pathway (one with complete atrioventricular block and the other with a small pericardial effusion). Radiofrequency catheter ablation of septal accessory pathways is efficacious and safe. The procedure time can be shortened and success rate can be increased after improvement of the technique--that is, consideration of a bipolar approach for energy delivery in difficult cases.

Localization of accessory pathways from the 12-lead electrocardiogram using a new algorithm

A new algorithm (St. George's algorithm), based on the polarity and morphology of QRS complexes rather than delta waves, was developed for localizing accessory pathways to 1 of 9 sites on the atrioventricular annuli. This was compared with algorithms previously proposed by Skeberis et al (localizing to 1 of 7 sites) and Milstein et al (localizing to 1 of 4 sites). The preexcited 12-lead electrocardiograms recorded during sinus rhythm in 106 consecutive patients (including 60 retrospectively analyzed patients and 46 prospectively analyzed patients) who underwent successful radiofrequency catheter ablation of a single accessory pathway were analyzed by 3 blinded observers using all 3 algorithms. The results were compared with the actual localization of accessory pathways as derived from endocardial mapping during catheter ablation. In all 106 patients, the accuracy of the 3 algorithms for 4 sites on the atrioventricular annuli (as considered by Milstein's method) was 72%, 79%, and 92% for Milstein's, Skeberis', and St. George's algorithms, respectively. For 7 sites (as considered by Skeberis' method), the accuracy was 65% (Skeberis' algorithm) and 88% (St. George's algorithm), and for 9 sites (as considered by our method) the accuracy was 86% (St. George's algorithm). In 46 prospectively analyzed patients, the accuracy of the 3 algorithms for 4 sites was 70% (Milstein's), 67% (Skeberis'), and 87% (St. George's); for 7 sites the accuracy was 61% (Skeberis') and 85% (St. George's), and for 9 sites the accuracy was 85% (St. George's). The reproducibility of St. George's and Skeberis' methods was better than that of Milstein's method. It is concluded that our algorithm allows localization of a single accessory pathway from the preexcited 12-lead electrocardiogram with sufficient precision and greater accuracy than other methods.

Single physician approach to radiofrequency catheter ablation in patients with supraventricular tachycardia.

The minimal requirements for safe and effective performance of catheter ablation using radiofrequency current are still unclear. To determine the feasibility and safety of single physician approach to catheter ablation of supraventricular tachycardia substrate using radiofrequency energy, the results of the ablation procedure in 52 consecutive patients were evaluated. The procedures were performed during 1 year by the same physician and nurse. Twenty-one patients had selective atrioventricular (AV) nodal pathway ablation and 31 patients had accessory AV pathway ablation. Forty-eight patients (89%) had the diagnostic and the ablative procedure during the same electrophysiological test. In the 21 patients with AV nodal reentrant tachycardia, all had successful selective ablation of the fast (13) or the slow (8) pathways. Eight patients had recurrence of the clinical tachycardia and had a successful reablation. No patient developed complete AV block or other significant complications. The mean fluoroscopy time during the procedure was 16.0 +/- 8.6 minutes. In the eight patients with Wolff-Parkinson-White syndrome, all concealed accessory pathways were successfully ablated with a mean fluoroscopy time of 30.0 +/- 27.9 minutes. Two patients had recurrence of the conduction through the accessory pathway and had a successful reablation. Eighteen of 19 patients with a single overt accessory pathway had successful ablation, with a fluoroscopy time of 22.7 +/- 20.6 minutes. Three patients had an early recurrence of the conduction through the accessory pathway, reablation was successful in two of them. Ten accessory pathways were ablated in four patients with multiple pathways during nine procedures. Only two patients developed minor peripheral vascular complications.(ABSTRACT TRUNCATED AT 250 WORDS)

Radiofrequency ablation in multiple accessory pathways and the physiologic implications

The presence of multiple accessory pathways was noted in 24 of 210 consecutive patients (12 males and 12 females aged 15 to 77 years [mean ± SD 43 ± 16]) with the Wolff-Parkinson-White syndrome who underwent electrophysiologic study and radiofrequency ablation. Six had 3 and 18 had 2 accessory pathways. There were 25 manifest and 29 concealed accessory pathways. The location of the accessory pathways was in the left free wall in 22, the right free wall in 17, the left posterior portion of the ventricular septum in 8, the right posterior portion of the ventricular septum in 6, and the midseptum in 1. The success rate of accessory pathway ablation and the fluoroscopic time in these 24 patients with multiple accessory pathways were 89% and 78 ± 66 minutes, respectively, whereas they were 98% (p < 0.01) and 36 ± 37 minutes (p = 0.01) in the 186 patients with a single accessory pathway. The mean applications, the power level of the radiofrequency current and the application duration in these 24 patients were 21 ± 22, 30 ± 3 W, and 27 ± 10 seconds, respectively. In the 186 patients with a single accessory pathway, they were 9 ± 12 applications (p = 0.02), 30 ± 4 W (p = NS) and 26 ± 9 seconds (p = NS), respectively. Seventeen of the 24 patients had a follow-up electrophysiologic study 89 ± 40 days after ablation, and 2 (12%) had resumption of a right and left accessory pathway conduction. In conclusion, patients with multiple accessory pathways can be treated by radiofrequency ablation in a single session with a high success rate, although slightly less than that in patients with a single accessory pathway.

Reappraisal of radiofrequency ablation of multiple accessory pathways

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

A CASE OF WPW SYNDROME ASSOCIATED WITH MITRAL STENOSIS AND REFRACTORY ATRIAL FIBRILLATION

A 60 year-old man with Wolff-Parkinson-White (WPW) syndrome was admitted to our hospital because of atrial fibrillation and heart failure. He had a history of paroxysmal atrial fibrillation which had increased in frequency as mitral stenosis progressed over a period of 10 years. Since heart rate-dependent torsades de pointes appeared after DC defibrillation due to class IA antiarrhythmic agents, the drug was withdrawn and an intravenous infusion of isoproterenol was started. Sinus rhythm was restored and maintained by restarting the administration of the class I A antiarrhythmic agent. Electrophysiological examination revealed a single accessory conduction pathway and no retrograde conduction, the effective refractory period was prolonged to 330 msec. After the heart failure had improved, mitral valve replacement and transection of the bundle of Kent were performed. Because of the possibility of grave hemodynamic derangement induced by marked tachycardia, surgical treatment should be seriously considered in patients with mitral stenosis when associated with WPW syndrome and atrial fibrillation, even in those not classified as high risk patients.

Physiological substrate for antidromic reciprocating tachycardia. Prerequisite characteristics of the accessory pathway and atrioventricular conduction system.

Although the anatomic "substrate" for the occurrence of antidromic reciprocating tachycardia (ART) has been previously examined, the underlying physiological substrate for this unusual arrhythmia in patients with the Wolff-Parkinson-White syndrome has not been thoroughly characterized. The electrophysiological properties of the accessory pathway and normal ventriculoatrial conduction system in 30 patients with ART and a single accessory pathway were compared with those observed in a control group of 36 patients without this arrhythmia to elucidate the critical physiological substrate essential for the development and maintenance of ART. Inducible ART had a mean cycle length of 286 +/- 31 msec. The average retrograde ventriculoatrial conduction system effective refractory period in ART patients was significantly less than that in the control group (244 +/- 32 versus 291 +/- 46 msec, p = 0.0002). All of the ART patients showed retrograde conduction over the normal conduction system at cycle lengths of less than or equal to 360 msec; 23 had 1:1 conduction to less than or equal to 300 msec, and 16 showed 1:1 propagation at cycle lengths of less than or equal to 260 msec. The shortest cycle length accompanied by 1:1 retrograde propagation over the normal conduction system in patients with ART was also significantly less than that observed in the control group (274 +/- 39 versus 347 +/- 73 msec, p less than 0.001). The accessory pathway anterograde ERP in ART patients with 1:1 retrograde conduction over the normal ventriculoatrial conduction system at cycle lengths of less than or equal to 360 was significantly less than that seen in comparable control patients (247 +/- 23 versus 284 +/- 56 msec, p = 0.001), and the accessory pathway location was significantly further from the atrioventricular node in 21 patients with ART undergoing surgery than that in 22 operated control patients (3.8 +/- 0.8 versus 2.9 +/- 0.8 mapping units, p = 0.0025) who also had retrograde ventriculoatrial conduction to cycle lengths of less than or equal to 360 msec. No significant differences in anterograde atrioventricular conduction system properties, retrograde accessory pathway refractoriness, or shortest ventricular pacing cycle lengths maintaining 1:1 conduction via the accessory pathway were observed between groups. This quantitative characterization of the properties of conduction and refractoriness of both the accessory pathway and ventriculoatrial conduction system and the relation between these characteristics and the accessory pathway location in ART patients provides additional insight into the prerequisites for the initiation and maintenance of this rhythm disturbance.