Localization and interruption of accessory conduction pathway in the Wolff-Parkinson-White syndrome

Inverse independent component analysis facilitates clarification of the accessory conductive pathway of Wolf-Parkinson-White syndrome electrocardiogram

Our aim was to demonstrate a digital analyzing method that could extract the potential of early excitation derived from accessory conductive pathway (ACP) from fusion of the QRS complex wave of the electrocardiogram of Wolf-Parkinson-White (WPW) syndrome. A 13-year-old boy with WPW syndrome received successful catheter ablation therapy. ECG was recorded and analyzed using independent component analysis (ICA) and inverse independent component analysis (I-ICA), at pretherapy and posttherapy. We identified the ACP potential and the following potential spread to the ventricle. Results agreed with those of intracardiac mapping, locating the ACP in the left posterior side of the heart. ICA and I-ICA might be useful for noninvasive analysis of WPW syndrome ECG and other electrocardiac abnormalities.

Monomorphic ventricular tachycardia related to Wolff-Parkinson-White surgery

Monomorphic ventricular tachycardia (MVT) is well described in patients who have had a ventricular scar due to repair of congenital heart disease. A 54-year-old woman presented with MVT 20 years after WPW surgery for a left-sided accessory pathway. The circuit was mapped to an area at the base of the left ventricle consistent with the incision described in the operation report. Entrainment confirmed the re-entrant circuit. Successful radiofrequency ablation was performed in a zone of slowed conduction consistent with the circuit isthmus. Any iatrogenic ventricular scar may form the substrate for MVT and be treated with standard electrophysiology techniques.

Accuracy and limitations of published algorithms using the twelve-lead electrocardiogram to localize overt atrioventricular accessory pathways

INTRODUCTION

The purpose of this study was to evaluate the accuracy and limitations of published algorithms using the 12-lead ECG to localize AV accessory pathways (APs).

METHODS AND RESULTS

The 11 relevant algorithms found in the literature (MEDLINE database and major scientific sessions) were tested on a series of 266 consecutive patients who successfully underwent radiofrequency catheter ablation of a single overt AV AP. The positive predictive values (PPV) of the algorithms in applicable patients were significantly lower for algorithms with > 6 accessory location sites (40.6% +/- 10.9% vs 61.2% +/- 8.0%; P < 0.03) and show a tendency for algorithms not relying on delta wave polarity but on QRS polarity only (36.6% +/- 11.2% vs 52.3% +/- 13.1%; P = 0.09). The PPV in applicable patients is related to the AP location (P < 0.001) and ranked from the highest to the lowest as follows: left lateral (mean PPV = 86.3%), posteroseptal (mean PPV = 65.2%), right anteroseptal (mean PPV = 45.2%), and right posterolateral (mean PPV = 23.4%).

CONCLUSION

Our study suggests that the accuracy of algorithms relying on the 12-lead ECG depends on AP locations as defined in the algorithms and on the number of AP sites. The accuracy tends to be lower when delta wave polarity is not included in the algorithm's architecture. This should be considered when using these algorithms or when building new ones.

Development and validation of an ECG algorithm for identifying accessory pathway ablation site in Wolff-Parkinson-White syndrome

INTRODUCTION

Delta wave morphology correlates with the site of ventricular insertion of accessory AV pathways. Because lesions due to radiofrequency (RF) current are small and well defined, it may allow precise localization of accessory pathways. The purpose of this study was to use RF catheter ablation to develop an ECG algorithm to predict accessory pathway location.

METHODS AND RESULTS

An algorithm was developed by correlating a resting 12-lead ECG with the successful RF ablation site in 135 consecutive patients with a single, anterogradely conducting accessory pathway (Retrospective phase). This algorithm was subsequently tested prospectively in 121 consecutive patients (Prospective phase). The ECG findings included the initial 20 msec of the delta wave in leads I, II, aVF, and V1 [classified as positive (+), negative (-), or isoelectric (+/-)] and the ratio of R and S wave amplitudes in leads III and V1 (classified as R > or = S or R < S). When tested prospectively, the ECG algorithm accurately localized the accessory pathway to 1 of 10 sites around the tricuspid and mitral annuli or at subepicardial locations within the venous system of the heart. Overall sensitivity was 90% and specificity was 99%. The algorithm was particularly useful in correctly localizing anteroseptal (sensitivity 75%, specificity 99%), and mid-septal (sensitivity 100%, specificity 98%) accessory pathways as well as pathways requiring ablation from within ventricular venous branches or anomalies of the coronary sinus (sensitivity 100%, specificity 100%).

CONCLUSION

A simple ECG algorithm identifies accessory pathway ablation site in Wolff-Parkinson-White syndrome. A truly negative delta wave in lead II predicts ablation within the coronary venous system.

Surgical treatment of patients with Wolff-Parkinson-White syndrome and associated Ebstein's anomaly

Ebstein"s anomaly is the most common congenital heart disease associated with the Wolf-Parkinson-White syndrome. Between November 1973 and March 1993, we surgically treated 42 patients with Wolff-Parkinson-White syndrome and Ebstein's anomaly. The patient's ages ranged from 5 months to 59 years (mean 35.3 +/- 14.0 years). There were a total of 52 accessory pathways, 48 of which were located in the right (65%) or posteroseptal (29%) area. A left-sided accessory pathway was seen in only two patients (3.8%). Division of all right-sided accessory pathways was done during normothermic cardiopulmonary bypass with the heart beating; cryocoagulation was applied together with scalpel dissection of the atrioventricular groove. Division of the left-sided accessory pathways was done with the use cold potassium cardioplegic arrest. Thirty-five of these patients underwent tricuspid valve operation for Ebstein's anomaly and 11 of them underwent tricuspid valve replacement with a bioprosthesis. All 52 accessory pathways were successfully divided, although two patients required reoperation because of tachycardia caused by accessory pathways in different positions. Three hospital deaths (7.1%) occurred. There were no late deaths during the follow-up period (mean 94.3 +/- 52.4 months), but two patients required repeat tricuspid operation because of progression of the tricuspid regurgitation. Because no repeat operations were required during long-term follow-up patients who underwent valve repair or valve replacement, correction should be indicated in some patients.

Epicardial electric shock ablation of the left lateral accessory pathway

Fifty patients with drug-resistant, recurrent tachyarrhythmias causing Wolff-Parkinson-White syndrome underwent surgery between 1990 and 1992. All recognized surgical methods for accessory pathway destruction were performed. Epicardial electric shock ablation was first used as a method of surgically destroying an accessory atrioventricular pathway in 1983. This technique avoids the need for cardioplegia and hypothermia during operation. The procedure is based on the application of a series of two to five electrical shocks (50-150 J) to the region of the atrioventricular groove where the accessory pathway has been previously located. Some 32 patients with a left free wall accessory pathway underwent this operation. Cardioplegia and hypothermia were not required in 22 patients with an accessory pathway located in the left lateral position. In the second group comprising ten patients with a left lateral accessory pathway, four were diagnosed as having a second pathway and four had concomitant heart pathology such as coronary artery disease -- one had an atrial septal defect and another had a ventricular septal defect. Accessory pathway ablation was carried out in these ten patients using epicardial electric shock under normothermic cardiopulmonary bypass. Concomitant heart pathology was corrected at the second stage of the operation under cardiopulmonary bypass with cardioplegia and hypothermia. Postoperative electrophysiological studies confirmed that the accessory pathway had been destroyed in all patients. The only side effects of epicardial electric shock application were transient ST elevation < 1 mm in four patients, transient atrioventricular bloc in two and moderate sinus tachycardia in three.(ABSTRACT TRUNCATED AT 250 WORDS)

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

BACKGROUND

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.

METHODS

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.

RESULTS

In 128 patients (92%), the new algorithm allowed an accurate diagnosis of the site of implantation of the accessory pathway.

CONCLUSION

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.

Surgical treatment of Wolff-Parkinson-White syndrome in infants and children

Electrophysiologic features and surgical results were examined in 55 pediatric patients who underwent surgical accessory pathway division for Wolff-Parkinson-White syndrome. There were 31 male and 24 female patients ranging in age from 4 months to 15 years (mean age, 9.8 +/- 4.2 years; 25 patients were less than 10 years old; 4 patients were less than 12 months). Eleven of these patients had associated congenital heart disease and underwent concomitant surgical procedures to treat those conditions. Preoperative effective refractory period of antegrade accessory pathways, the right atrium, atrioventricular node, and cycle length during reentrant tachycardia were shorter in pediatric patients than in adult patients. Antegrade accessory pathways showed right predominance more frequently in the pediatric group than in the adult group. Surgical techniques included an endocardial approach (an epicardial approach was used in 1 patient) and concomitant operation for combined heart disease. The early mortality rate was 3.6%, whereas no late deaths occurred during the follow-up period of 96.8 +/- 54.9 months (maximum follow-up, 205 months). The absolute cure rate was 92%. There were no significant differences in early and late mortality between pediatric and adult patients. Surgical treatment of the Wolff-Parkinson-White syndrome in pediatric patients is as safe and effective as in adults. Considering the potential complications from prolonged fluoroscopic exposure during catheter ablation, surgical division of accessory pathways in children is a promising modality for the treatment of Wolff-Parkinson-White syndrome in selected cases.

Noninvasive localization of accessory pathways by magnetocardiographic imaging

The magnetocardiogram (MCG) is a newly developed method that helps localize a cardiac current source. To test the clinical accuracy of a 7-channel biomagnetic system in the localization of early ventricular depolarization sites, the MCGs of 14 patients with Wolff-Parkinson-White (WPW) syndrome were recorded in a radiofrequency-shielded room. The locations of early ventricular depolarization sites were classified by standard 12-lead electrocardiograms (ECGs) and body surface isopotential mapping. The accessory pathways of 3 patients with WPW syndrome were located in the right free wall and in 11 patients in the left free wall. The three-dimensional (3-D) dipole location was computed every 2 ms from the onset of the QRS complex by the least-square method. These 3-D dipole locations were projected onto a gated magnetic resonance image in order to visualize the propagation of the calculated ventricular source. The results were compared with those obtained by body surface isopotential mapping, and electrocardiographic and electrophysiologic studies. The location of the deduced current dipole at 20 ms correlated well with the location of the accessory pathway by the body surface mappings in 12 of the 14 patients with WPW syndrome. The MCG is capable of precisely determining the 3-D location of a current source in a noninvasive manner and may be of potential benefit in the treatment of WPW syndrome by catheter ablation.

Comparative study of eight sets of ECG criteria for the localization of the accessory pathway in Wolff-Parkinson-White syndrome

Eight sets of electrocardiographic (ECG) criteria for the localization of accessory conduction pathway (ACP) were evaluated on 182 patients with a single ACP. The Rosenbaum criteria identified 78.6% of the left-sided and 94.0% of the right-sided ACPs. Four of the other seven sets of criteria demonstrated a sensitivity higher than 70.9% and six showed a specificity higher than 74.9% in the 4-region ACP localization. The ECG feature of the delta wave polarity in lead V1 correctly localized the ACP to one of three broad regions in 162 of 182 patients with an overall specificity of 94.5%. The study indicates that (1) the 12-lead ECG is of practical value for initial ACP localization; (2) a type A ECG is almost invariably associated with a left-sided ACP, while type B may occur with any ACP location; (3) the polarity of the delta wave is the most important ECG feature, and the polarities of the delta wave and main QRS complex in lead V1 play an important role in ACP localization.

Clinical experience with surgery for paroxysmal supraventricular tachycardia: a report of 103 cases

One-hundred-and-three patients underwent surgery for paroxysmal supraventricular tachycardia (PSVT). In eighty-three patients (81%), PSVT was due to an accessory atrioventricular pathway (Group I) and in 20 (19%) to Atrioventricular Junctional (AV nodal) Reentrant Tachycardia (AVJRT:Group II). Initial surgery successfully divided 77 of 83 accessory pathways, including 58 of 60 left free wall pathways, 12 of 15 posteroseptal pathways, six of seven right free wall pathways and one anteroseptal pathway. Twenty patients had successful surgery for AVJRT. Surgery was performed with low morbidity and no early or late mortality in either group. One patient in each group required permanent pacemaker implantation. Immediate (within one week) postoperative electrophysiological study using epicardial wires was performed in 96% of patients and repeat electrophysiological study six months later was possible in 65/103 (63%) patients. Patients with surgery for accessory pathways were followed-up for a mean 34 +/- 23 months, while those with surgery for AVJRT for a mean of 13 +/- seven months. No patient with successful surgery has had a clinical recurrence of PSVT. Thus the results indicate that surgery is a safe and curative therapy for patients with PSVT.

Localization of cardiac arrhythmias: conventional noninvasive methods

Noninvasive localization of the accessory pathway (AP) in patients with the Wolff-Parkinson-White syndrome and of the site of origin of ventricular tachycardia (VT) is reviewed. 12-lead electrocardiography (ECG) is the most readily available method for localization of both the AP and the site of VT origin. Many published ECG criteria are introduced. The application of body surface potential mapping, vectorcardiography, nuclear phase imaging, echocardiography, computed tomography, nuclear magnetic resonance, and signal-averaged ECG in the localization of these arrhythmogenic substrates is also described. We believe that ECG is the most sensitive noninvasive method for AP localization as well as being convenient and simple; it may be used as the only noninvasive method for the initial evaluation. The left lateral AP, which occurs with an incidence of more than 40%, could be localized preoperatively by noninvasive methods only. For localization of the site of VT origin, none of the noninvasive methods is accurate enough for guiding the surgical and catheter-mediated ablative therapies so far.

Determination of transmural location of onset of activation from cardiac surface electrograms

Methods of estimating depth of origin of ventricular activation from cardiac surface electrograms were evaluated in experiments on eight dogs. The ventricles were paced via multielectrode needle arrays placed transmurally in from four to six locations in the wall of the left ventricle. A multiplexed data-recording system was used to simultaneously record from 64 unipolar cardiac surface electrodes during pacing at each multielectrode needle site. The four indexes evaluated were the maximum and average gradients of activation isochrones around the site of earliest epicardial activation, the QRS area at the site of earliest epicardial activation, the interval between the QRS onset computed from all 64 epicardial surface electrograms, and the time of the minimum dV/dt in the electrogram displaying the earliest epicardial activation time (t(ee)-t(rmso) interval). Correlation coefficients between depth of stimulation and average and maximum gradients of isochrones, QRS area at the site of earliest epicardial activation, and t(ee)-t(rmso) interval were 0.985 or higher. These methods, particularly those involving gradients of isochrones, should be useful for evaluating electromaps of patients undergoing surgery for ablation of tachyarrhythmias.

Surgical management of tachyarrhythmias

In this study of surgical procedures for various tachyarrhythmias, Wolff-Parkinson-White syndrome comprised most of the cases. An endocardial approach was used to ablate accessory pathways. Additional use of cryocoagulation after surgical incision of the atrium, previously routinely performed, is at present only done occasionally for septal accessory pathways. Ventricular tachycardia (VT) was the next most frequent condition. The surgical procedures for ischemic and nonischemic VTs are completely different, although both are based on the principle of complete electrophysiologic mapping. For ischemic VT, surgery consists of resection of the left ventricular aneurysm and excision or cryocoagulation of the endocardium, or both. For nonischemic VT, either excision of the entire thickness of the myocardium (2.0 X 2.5 cm on average) at the earliest excitation site of the right ventricle and cryocoagulation of the area of delayed potential or only incision and cyrocoagulation of the left ventricle were performed to avoid reduction of the left ventricular cavity. Ectopic atrial tachycardia was cured by excision of the earliest excitation site without use of a heart-lung machine, when the focus was located in the atrial free wall. Other successful treatments were of reentrant atrial tachycardia by cryocoagulation, atrial flutter by cryocoagulation of impulse pathways at the coronary sinus and around the atrioventricular node, and a new surgery for atrial fibrillation and flutter, which retained sinus rhythm. Johnson's procedure was used for surgical ablation of atrioventricular nodal reentrant tachycardia.

Intermediate-term results of the endocardial surgical approach for anomalous atrioventricular bypass tracts

Between October 1974 and March 1, 1985, 26 patients with 29 anomalous AV bypass tracts underwent surgical treatment at the Medical Center of UAB, with follow-up from 1 to 14 years. Eleven of the patients underwent surgical correction of major associated cardiac anomalies. One patient had His bundle ablation, and 25 patients had direct surgical division of 28 bypass tracts with the use of an endocardial approach. Successful division was achieved in 27 (96%; confidence limits 88% to 99%) of 28 bypass tracts identified pre- and intraoperatively. There were no hospital deaths, but on formal follow-up there were three late deaths, all occurring in patients with major associated cardiac pathology. Neither preexcitation nor reciprocating tachycardia recurred, and functional status was excellent among patients without associated cardiac lesions. Because of the safety and, at least on intermediate-term follow-up, apparently curative nature of this operation (particularly for patients without other major cardiac pathology), surgical treatment is recommended for patients with bypass tracts having lethal potential, those with reciprocating tachycardia unresponsive to drugs, and to symptomatic patients facing many years of medications.

Surgical treatment of arrhythmias

Surgical treatment of arrhythmias is often more expeditious and more cost-effective in the long run than pharmacologic therapy. In the past, surgical treatment of arrhythmias has been reserved for patients with disabling paroxysmal or incessant tachycardia refractory to medical management, severe life-threatening arrhythmia or aborted episodes of sudden death. However, tachyarrhythmias that are refractory to pharmacologic therapy because of drug inefficacy, noncompliance or limiting side effects are not uncommon. Although nonpharmacologic treatment of arrhythmias carries with it a one-time period of higher risk (i.e., when the patient undergoes surgery), it is curative and often preferable to the uncertainty and possibly higher cumulative risk associated with medical management.

Frequency, diagnosis and clinical characteristics of patients with multiple accessory atrioventricular pathways

Multiple accessory atrioventricular (AV) pathways were documented in 52 of 388 patients (13%) who underwent detailed electrophysiologic evaluation. Multiple AV pathways were identified during intraoperative mapping or electrophysiologic study by different patterns of ventricular preexcitation during atrial fibrillation, flutter or atrial pacing with different delta-wave morphologic and ventricular activation patterns; different sites of atrial activation during right ventricular pacing or orthodromic reciprocating tachycardia; or preexcited reciprocating tachycardia using a second pathway as the retrograde limb of the tachycardia. A logistic model was used to determine which clinical, electrocardiographic and electrophysiologic variables were associated with multiple AV pathways. Right free-wall and posteroseptal accessory AV pathways were more common in patients with multiple AV pathways and were frequently associated. Multivariate logistic regression identified Ebstein's anomaly, and a history of preexcited reciprocating tachycardia as significant variables (p less than 0.0001). Pathway location was not subjected to statistical analysis because of confounding variables.

Long-term follow-up after surgical correction of Wolff-Parkinson-White syndrome

The long-term efficacy of surgical correction of Wolff-Parkinson-White syndrome was evaluated in 45 consecutive patients. Before surgery, 42 patients had reciprocating tachycardia and 12 had atrial fibrillation. The principal operative procedure was endocardial incision in 42 patients, endocardial cryoablation in 2 patients and epicardial cryoablation without dissection of the atrioventricular (AV) fat pad in 1 patient. Two patients had perioperative complications. One patient had bleeding that necessitated reoperation, and one had a right cerebral stroke with subsequent clearing of neurologic deficit. At postoperative electrophysiologic study, only the patient who underwent epicardial cryoablation had conduction over an accessory connection. Two others had intermittent delta waves in the early postoperative period but no accessory connection conduction at electrophysiologic study. During a mean follow-up of 3.1 years, the patient with ineffective cryoablation had recurrent orthodromic tachycardia, and one other patient had late recurrence of delta waves without arrhythmias. Four other patients had frequent palpitation, which was caused by premature ventricular complexes in three and sinus tachycardia in one. Seventeen patients had occasional "skipped beats" without recurrence of tachyarrhythmias. Twelve of 13 patients whose arrhythmias limited employment before surgery returned to work after surgery. By actuarial analysis at 1, 2 and 3 years, all patients were alive and 98% were free from tachyarrhythmias. Surgical correction of Wolff-Parkinson-White syndrome provides excellent long-term results with low morbidity. Patients who are disabled by arrhythmias return to work after successful surgery. Delta waves may persist or recur without return of arrhythmias. Minor postoperative episodes of palpitation are common and do not correlate with tachyarrhythmias.

Surgical treatment of accessory atrioventricular pathways and symptomatic tachycardia in children and young adults

Twenty-seven patients aged 21 years or younger (mean 15) with symptomatic tachycardia underwent operation for ablation of an accessory atrioventricular pathway. Six patients had associated Ebstein's malformation of the tricuspid valve. Supraventricular tachycardia had been present for a mean of 5 years. At electrophysiologic study, 4 patients were found to have 2 accessory pathways. Left ventricular free wall pathways were found in 14 patients, right ventricular free wall pathways in 10 and septal pathways in 6. Successful initial ablation of all the pathways was achieved in 26 of the 27 patients. No patient died perioperatively and none had persistent complete heart block. During a mean follow-up of 11 months, no patient had recurrence of an arrhythmia related to the accessory pathway. Thus, the surgical treatment of children and young adults with accessory atrioventricular pathways and symptomatic supraventricular tachycardia is safe and effective. For these patients, unless the tachycardia can be easily controlled with a minimal number of drugs and adverse effects, surgical ablation should be considered early in the clinical course.

Nuclear tomographic phase analysis: localization of accessory conduction pathway in patients with Wolff-Parkinson-White syndrome

The purpose of this study was to evaluate the usefulness of tomographic phase analysis in detecting the site of the accessory conduction pathway (ACP) in patients with Wolff-Parkinson-White (WPW) syndrome. Gated emission computed tomography and planar gated blood pool scintigraphy were performed in 20 patients with WPW syndrome, 14 with delta waves and six without delta waves (two intermittent types and four concealed types). The abnormal initial contractions in both planar and tomographic phase images were compared with the sites of ACPs confirmed by epicardial mapping and surgery. The atrioventricular ring was divided into eight segments on each side, and the identification of the initial phase in the segment in which the ACP was located, or that adjacent to it, was considered to be the correct diagnosis. In planar phase analysis, the abnormal initial phase was identified correctly in 8 of 14 patients (57%), whereas in tomographic phase analysis, the site of the ACP was detected in 12 of 14 patients (86%). Tomographic phase analysis can be a helpful adjunctive method in patients with WPW syndrome.

A digital timing and display unit for intraoperative mapping of cardiac arrhythmias

An inexpensive display and timing unit incorporating a multichannel signal delay has been developed for mapping the heart during electrophysiological surgery. It provides a continuous digital readout of the time relationships between 3 intracardiac electrograms and the surface electrocardiogram. The electrograms are displayed on a storage oscilloscope with an automatic erase facility. This unit is used to locate accessory atrioventricular connections in the Wolff-Parkinson-White syndrome, to map ventricular tachycardias and to locate the bundle of His. The design has been refined during 5 years of use in over 200 operative procedures.

Techniques of intraoperative electrophysiologic mapping

Cardiac mapping during sinus rhythm and during spontaneous or induced ventricular arrhythmias is a promising technique that offers a variety of potential strategies to improve our ability to locate abnormal areas in the heart that are the seat of arrhythmias. If surgical procedures are to become more limited in scope in an attempt to salvage myocardium, mapping will need to be used to a greater extent. However, it remains to be established which mapping technique will prove most sensitive and specific in detecting sites of arrhythmia, and whether the localizing method used allows a more directed surgical intervention to be successful.

Surgical treatment of the Wolff-Parkinson-White syndrome in infants and children

Eleven pediatric Wolff-Parkinson-White (WPW) syndrome patients underwent surgery. Four had left, 5 right cardiac type and 2 had right septal type WPW syndrome. Two patients had 2 accessory conduction pathways (ACP). Ebstein's anomaly and secundum type atrial septal defect were the association congenital cardiac diseases in one patient each. Indications for surgery included repeated and/or long-lasting paroxysmal supraventricular tachycardia (PSVT), ineffective drug therapy, cardiac failure due to frequent tachycardia, short effective refractory period of the ACP, and simultaneous surgery for associated congenital cardiac diseases. Pre- and intra-operative examinations, including ECG, VCG, UCG, body surface mapping, intracavitary recording by catheter electrodes, computerized epicardial mapping, and endocardial mapping, were performed for the precise localization of the ACP. The surgical method was basically the same as is used for adults. Anterior median stermotomy was used primarily in right cardiac and right septal type and left anterior thoracotomy was used in 3 of 4 cases of the left cardiac type. Eight of 11 cases, two of which had 3 ACPs, were completely cured and in 3 there was evidence of postoperative pre-excitation. However, the PSVT attacks disappeared almost completely and drug therapy is not required at present.