The localization of bypass tracts in the Wolff-Parkinson-White syndrome from the surface electrocardiogram

Accessory pathway localization with probabilistic density maps generated by a mobile application: Assessment of a full pre-excitation net-vector method

INTRODUCTION

Precise electrocardiographic localization of accessory pathways (AP) can be challenging. Seminal AP localization studies were limited by complexity of algorithms and sample size. We aimed to create a nonalgorithmic method for AP localization based on color-coded maps of AP distribution generated by a web-based application.

METHODS

APs were categorized into 19 regions/types based on invasive electrophysiologic mapping. Preexcited QRS complexes were categorized into 6 types based on polarity and notch/slur. For each QRS type in each lead the distribution of APs was visualized on a gradient map. The principle of common set was used to combine the single lead maps to create the distribution map for AP with any combination of QRS types in several leads. For the validation phase, a separate cohort of APs was obtained.

RESULTS

A total of 800 patients with overt APs were studied. The application used the exploratory data set of 553 consecutive APs and the corresponding QRS complexes to generate AP localization maps for any possible combination of QRS types in 12 leads. Optimized approach (on average 3 steps) for evaluation of preexcited electrcardiogram was developed. The area of maximum probability of AP localization was pinpointed by providing the QRS type for the subsequent leads. The exploratory data set was validated with the separate cohort of APs (n = 256); p = .23 for difference in AP distribution.

CONCLUSIONS

In the largest data set of APs to-date, a novel probabilistic and semi-automatic approach to electrocardiographic localization of APs was highly predictive for anatomic localization.

A case of Wolff–Parkinson–White syndrome in which two-dimensional speckle-tracking echocardiography was useful for identifying the location of the accessory atrioventricular pathway

Background

In Wolff–Parkinson–White (WPW) syndrome, accessory atrioventricular pathways (AP) result in abnormal pre-excitation around the atrioventricular annuli and produce a dyssynchronous contraction of cardiac chambers. Identification of the AP affects the outcome of catheter ablation.

Case summary

We report a case of WPW syndrome and paroxysmal atrial fibrillation in a 65-year-old man. Wolff–Parkinson–White syndrome Type B was suspected from lead V1, but when two-dimensional speckle-tracking echocardiography (2D-STE) was performed, a decrease in regional strain was observed in the anterior basal wall of the left ventricle. We identified the earliest site of atrioventricular conduction, and improvement in the regional strain at the site of ablation was observed after successful AP ablation.

Discussion

Various echocardiographic techniques have been investigated as non-invasive alternatives for AP localization. Longitudinal 2D-STE accurately identified contractile abnormalities associated with the AP, allowing us to non-invasively estimate the localization of the AP in WPW syndrome.

Infarction or Pseudo-infarction?

An applicant with a history of paroxysmal atrial fibrillation is found to have QS waves in leads III and AVF suggestive of a prior inferior wall myocardial infarction. Using the relationship between Q wave and T wave vectors in the inferior leads, an alternative explanation is explored.

Electrocardiographic estimation of successful ablation site in patients with manifest inferior paraseptal accessory pathway

Inferior paraseptal accessory pathways (APs) have a wide distribution and prediction of AP location before radiofrequency ablation is very important in such pathways. We aimed to estimate successful ablation site based on electrocardiogram in 137 patients (mean age: 25.8±9.0; 126 males) with single manifest inferior paraseptal AP. Right endocardial inferior paraseptal APs were discriminated from left endocardial APs with an R/S ratio <1 (p<0.001) and negative delta wave in lead V1 (p<0.001). Epicardial inferior paraseptal APs were differentiated from endocardial APs by a negative delta wave in lead II (p=0.001), positive delta waves in AVR (p<0.001) and V1 (p=0.012), R/S ratio <1 in lead II (p=0.03), and R/S ratio ≥1 in V1 (p=0.04). Delta wave polarity and R/S ratio in lead V1 differentiate right endocardial inferior paraseptal APs from left endocardial APs. Delta wave polarities in leads II, AVR and V1, and R/S ratios in leads II and V1 estimate epicardial inferior paraseptal APs.

A Practical ECG Criterion to Unmask Left Accessory AV Connections in Patients With Subtle Preexcitation

BACKGROUND

Accessory AV-connections capable of antegrade conduction need to be recognized because of the potential for life-threatening arrhythmias. However, the preexcited ECG pattern may be subtle, especially among left-sided AV-connections. We explored whether additional ECG criteria might help identify left-sided AV-connections.

METHODS

We analyzed 156 patients who underwent an electrophysiology study (EPS) and ablation for paroxysmal supraventricular tachycardias (PSVT). Patients were divided into 2 groups: those with left-sided AV-connections (Group 1) and all other PSVT (Group 2). Various ECG parameters were compared before and after ablation in both groups.

RESULTS

The EPS identified left-sided AV-connections among 43 patients (Group 1) and excluded it among 113 (Group 2). Baseline ECG in Group 1 demonstrated obvious preexcitation among 24/43 patients (55.8%), the remaining 19/43 missing obvious preexcitation. R/S ratio > 0.5 in V1 was noted in 38/43 (88.4%) patients in Group 1 before ablation (median 1.00; IQR 0.58-2.20), including 16/19 (84.2%) patients lacking obvious left-sided AVconnections. Conversely, only 10/113 (8.8%) patients in Group 2 had R/S ratios in V1 ≥ 0.5 (0.20; 0.10-0.31), P < 0.0001. After ablation, the R/S ratio decreased significantly in Group 1 (0.29; 0.17-0.45), P < 0.0001. Thus, a combined criterion of classic preexcitation or R/S ratio ≥ 0.5 on ECG identified 40/43 left-sided AV-connections (sensitivity 93.0%). The negative predictive value of this combined criterion was 103/106 (97.2%).

CONCLUSIONS

In symptomatic patients, combining the R/S ratio (≥ 0.5) in lead V1 with the classic preexcitation pattern on ECG markedly improved the sensitivity to diagnose left-sided AV-connections. This ratio may be particularly useful among patients lacking obvious preexcitation.

Supraventricular tachycardias: proposal of a diagnostic algorithm for the narrow complex tachycardias

The narrow complex tachycardias (NCTs) are defined by the presence in a 12-lead electrocardiogram (ECG) of a QRS complex duration less than 120ms and a heart rate greater than 100 beats per minute; those are typically of supraventricular origin, although rarely narrow complex ventricular tachycardias have been reported in the literature. As some studies document, to diagnose correctly the NCTs is an arduous exercise because sometimes those have similar presentation on the ECG. In this paper, we have reviewed the physiopathological, clinical, and ECG findings of all known supraventricular tachycardias and, in order to reduce the possible diagnostic errors on the ECG, we have proposed a quick and accurate diagnostic algorithm for the differential diagnosis of NCTs.

An enhanced method for accessory pathway localization in case of Wolff-Parkinson-White syndrome

This paper presents an analysis of the Arruda accessory pathway localization method for patients suffering from Wolff-Parkinson-White syndrome, with modifications to increase the overall accuracy. The Arruda method was tested on a total of 79 cases, and 91.1% localization performance was reached. After a deeper analysis of each decision point of the Arruda localization method, we considered that the lead aVF was not as relevant as other leads (I, II, III, V1) used. The branch of the decision tree, which evaluates the left ventricle positions, was entirely replaced using different decision criteria based on the same biological parameters. The modified algorithm significantly improves the localization accuracy in the left ventricle, reaching 94.9%. An accurate localization performance of non-invasive methods is relevant because it can enlighten the necessary invasive interventions, and it also reduces the discomfort caused to the patient.

Absence of left atrium-coronary sinus musculature electrical connection at coronary sinus ostium unmasked by unique double coronary sinus potentials pattern

We describe a 77-year-old man with Wolff-Parkinson-White syndrome exhibiting double coronary sinus (CS) potentials during retrograde conduction over accessory pathway (AP). The first, low-frequency potential (DP1) was first recorded in the left posterolateral region, while the second, higher frequency signal (DP2) was recorded in a lateral-to-septal direction. The two signals were fused near the left lateral wall. Successful ablation of the AP was obtained at its ventricular insertion site in the postero-septal region. The unexpectedly delayed activation of the paraseptal RA following activation of the paraseptal left atrium (DP1) can be explained by the absence of a LA-CS musculature (CSM) electrical connection at the proximal CS, which forces a detour of the activation wavefront from LA to RA via the distal CS (DP2). This is a rare case exhibiting unique double CS potentials which unmasked the absence of a LA-CSM electrical connection at CS ostium.

Use of an artificial neural network to localize accessory pathways of Wolff–Parkinson–White syndrome with12-lead electrocardiogram

Today, radio-frequency ablation has been shown to be a safe and effective method to treat paroxysmal tachycardia with Wolff-Parkinson-White syndrome. The many criteria reported for localizing the sites of accessory pathways from a 12-lead electrocardiogram have not proven adequate to differentiate the correct sites of accessory pathways for all situations. This study trained an artificial neural network to differentiate the varied features needed to localize 10 sites of accessory pathways. One hundred fifty patients underwent successful catheter ablation, with manifest single and antegradely conducting accessory pathways. Using the two electrocardiogram features of polarity of delta wave and R wave's share of QRS complex, an artificial neural network learned the characteristics of electrocardiogram waves for each site of the 10 accessory pathways through 90 learning cases, and an applicable network model was developed for testing. In 58 of 60 test cases (96.7%), sites of accessory pathways were localized correctly by the network. Based on the method employed in the present study, it thus becomes possible to predict the sites of accessory pathways with Wolff-Parkinson-White syndrome in more detail by using an artificial neural network with a 12-lead electrocardiogram. In the future, when this method is incorporated into a conventional automatic electrocardiogram system which could analyze delta waves and ORS complex, it will become useful to automatically diagnose the locations of the accessory pathways with Wolff-Parkinson-White syndrome in clinical practice.

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.

Ablation of posteroseptal and left posterior accessory pathways guided by left atrium-coronary sinus musculature activation sequence

INTRODUCTION

While some posteroseptal and left posterior accessory pathways (APs) can be ablated on the tricuspid annulus or within the coronary venous system, others require a left-sided approach. "Fragmented" or double potentials are frequently recorded in the coronary sinus (CS), with a smaller, blunt component from left atrial (LA) myocardium, and a larger, sharp signal from the CS musculature.

METHODS AND RESULTS

Forty patients with posteroseptal or left posterior AP were included. The LA-CS activation sequence was determined at the earliest site during retrograde AP conduction. Eleven APs (27.5%) were ablated on the tricuspid annulus (right endocardial), 9 (22.5%) inside the coronary venous system (epicardial), and 20 (50%) on the mitral annulus (left endocardial). A "fragmented" or double "atrial" potential was recorded in all patients inside the CS at the earliest site during retrograde AP conduction. Sharp potential from the CS preceded the LA blunt component (sharp/blunt sequence) in all patients with an epicardial AP, and in 10 of 11 (91%) patients with a right endocardial AP. Therefore, 18 of 19 (95%) APs ablated by a right-sided approach produced this pattern. The reverse sequence (blunt/sharp) was recorded in 19 of 20 (95%) patients with a left endocardial AP.

CONCLUSION

During retrograde AP conduction, the sequence of LA-CS musculature activation-as deduced from analysis of electrograms recorded at the earliest site inside the CS-can differentiate posteroseptal and left posterior APs that require left heart catheterization from those that can be eliminated by a totally venous approach.

Inaccuracy of Wolff-Parkinson-White Accessory Pathway Localization Algorithms in Children and Patients with Congenital Heart Defects

INTRODUCTION

ECG algorithms used to localize accessory pathways (AP) in patients with Wolff-Parkinson-White (WPW) syndrome have been validated in adults, but less is known of their use in children, especially in patients with congenital heart disease (CHD). We hypothesize that these algorithms have low diagnostic accuracy in children and even lower in those with CHD.

METHODS

Pre-excited ECGs in 43 patients with WPW and CHD (median age 5.4 years [0.9-32 years]) were evaluated and compared to 43 consecutive WPW control patients without CHD (median age 14.5 years [1.8-18 years]). Two blinded observers predicted AP location using 2 adult and 1 pediatric WPW algorithms, and a third blinded observer served as a tiebreaker. Predicted locations were compared with ablation-verified AP location to identify (a) exact match for AP location and (b) match for laterality (left-sided vs right-sided AP).

RESULTS

In control children, adult algorithms were accurate in only 56% and 60%, while the pediatric algorithm was correct in 77%. In 19 patients with Ebstein's anomaly, diagnostic accuracy was similar to controls with at times an even better ability to predict laterality. In non-Ebstein's CHD, however, the algorithms were markedly worse (29% for the adult algorithms and 42% for the pediatric algorithms). A relatively large degree of interobserver variability was seen (kappa values from 0.30 to 0.58).

CONCLUSIONS

Adult localization algorithms have poor diagnostic accuracy in young patients with and without CHD. Both adult and pediatric algorithms are particularly misleading in non-Ebstein's CHD patients and should be interpreted with caution.

Sensibility analysis of the Arruda localization method

This paper presents an analysis of the Arruda accessory pathway localization method (for patients suffering from Wolff-Parkinson-White syndrome) with suggestions to increase the overall performance. The Arruda method was tested on a total of 121 patients, and a 90% localization performance was reached. This was considered almost as performing result as the highest published (90%) by L. Boersma in 2002. After a deeper analysis of each decision point of Arruda localization method we considered that the lead AVF is not as relevant as other used leads (I, II, III, VI). The overall performance (90%) was slightly lower then the correct decision rate (91.67%) at the weakest decision element (AVF+) of the method. The vectorial space constructed from the most used leads (II, VI, AVF) is not orthogonal which can be a reason for weaker rate in case of AVF.

Parahisian radiofrequency catheter ablation in dogs: comparison of the above-valve and below-valve approaches

In patients with an accessory pathway close to the His bundle, radiofrequency catheter ablation (RFCA) requires additional care to avoid damage to the normal conduction system. To assess differences between approaches from above or below the tricuspid valve (TV), we performed RFCA in 20 dogs (from above, group A, n=10; from below, group B, n=10). RF energy with temperature control at 60 degrees 60 seconds was administered at the site where a small His potential was recorded from the ablation catheter guided by fluoroscopy and transesophageal echocardiography (TEE) (in the latter six dogs). Before and after RFCA, electrophysiological testing was performed and histological findings were compared. An ablated lesion was created in 7 of 10 (2 of 2 guided by TEE) dogs in group A and 5 of 10 (3 of 4 TEE) dogs in group B. In group A, an ablated lesion involved the atrium and ventricle in the anterior site of His bundle, but the lesion was only in the ventricle in group B. An atrioventricular block (AVB) and severe damage to the penetrating bundle was observed in one dog of group A. A large hematoma on the TV was made in 2 dogs and the complete right bundle branch block (CRBBB) occurred in 3 dogs of group B. The approach from below the TV was safer than that from above the TV in parahisian RFCA, because it did not create an AVB, although it has a high incidence of CRBBB and associated technical difficulties.

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.

Clinical features of Wolff-Parkinson-White syndrome

Wolff-Parkinson-White syndrome is the most common form of ventricular preexcitation. Understanding this syndrome is fundamental for anyone interested in learning about arrhythmias. This review addresses (1) the historic sequence of events that led to the understanding of this syndrome; (2) the pathologic, embryologic, and electrophysiologic properties of accessory pathways; (3) the epidemiology and genetics of this syndrome; (4) the clinical diagnosis of this syndrome, with special emphasis on the arrhythmias that patients with ventricular preexcitation are predisposed to; and (5) the therapy for patients with Wolff-Parkinson-White syndrome.

Prevalence of ventricular preexcitation in Japanese schoolchildren

BACKGROUND

Wolff-Parkinson-White syndrome is thought to be a congenital disease, however, its exact prevalence is not known. This may be because of the intermittent activity of accessory pathways in some cases and fluctuations in autonomic tone.

AIMS

To investigate the prevalence of ventricular preexcitation by electrocardiography and reported symptoms in each school age child in Yamanashi prefecture.

METHODS

From 1994 to 1996, answers to a questionnaire, results of physical examination, and electrocardiography were obtained from all schoolchildren in Yamanashi prefecture (n = 92,161; total population 880,000) on admission to elementary school (age 6 to 7 years, n = 28,395), junior high school (age 12 to 13 years, n = 31,206), and high school (age 14 to 15 years, n = 32,837).

RESULTS

Elementary and junior high school students had a significantly lower prevalence of preexcitation than high school students (0.073% and 0.070% v 0.174%, p < 0.001). The prevalence of left free wall pathway was highest in high school students (n = 27) compared with elementary (n = 6) and junior high school students (n = 5) (p < 0.005). The only symptom noted in the answers to the questionnaire was palpitations. The symptomatic cases were more frequent in high school (n = 13) than in elementary (n = 1) and junior high school (n = 2) children, but not significantly. No student with preexcitation had associated heart disease or family history of Wolff-Parkinson-White syndrome or sudden death.

CONCLUSIONS

The prevalence of preexcitation in younger schoolchildren was less frequent than previously reported. The prevalence of preexcitation and left free wall pathways increased with age. The symptoms were few and there was no significant morbidity.

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.

Electrocardiographic identification of mid-septal accessory pathways in close proximity to the atrioventricular conduction system

In order to identify ECG characteristics of overt mid-septal accessory pathways (APs) predictive of close proximity to the AV conduction system we analyzed data from patients who underwent successful RF catheter ablation of a mid-septal AP. Mean patient age was 31 +/- 16 years, and 13 were male. The 40 degrees right anterior oblique view was used to divide the mid-septal area into 3 zones: 1 (anterior portion); 2 (intermediate); and 3 (posterior portion). The 12-lead ECG was analyzed with regard to delta wave polarity and R/S transition in the precordial leads. The findings from patients ablated at zone 3 were compared to those at zones 1 and 2. All patients had a positive delta wave in the leads I, II, aVL, and negative delta wave in the leads III and aVR. The R/S transition occurred in lead V2 in 80% of patients. The delta wave in lead aVF was the only ECG characteristic that correlated with the AP ablation zone. Six of 8 patients ablated at zone 3 had a negative delta wave in lead aVF while 6 out of 7 patients ablated at zone 1 or 2 had a positive or isoelectric delta wave in lead aVF (P = 0.03). A positive or isoelectric delta wave in lead aVF identifies mid-septal AP in close proximity to the AV conduction system.

Increased dispersion of ventricular recovery time as a new repolarization abnormality in the Wolff-Parkinson-White syndrome

The aim of our study was to assess whether the presence of ventricular preexcitation affects the spatial distribution of ventricular recovery time. Recent reports support the hypothesis that QT and QTc dispersions (QTd and QTcd) can be reliably adopted as a non-invasive parameter to estimate regional discrepancies of ventricular repolarization. The ECGs of 32 healthy subjects with Wolff-Parkinson-White syndrome and of 29 normal individuals have been analysed using a Digitizer (Calcomp 9000), in order to obtain, for each subject, a mean QRS (M-QRS), QT (M-QTe), QTc (M-QTec), JT (M-JT), JTc (M-JTc) from all the measured intervals of the 12 standard ECG leads. QRS, QT and QTc dispersions (QRSd, QTd, QTcd) were defined as the difference between the maximal and minimal QRS, QTe and Qtec values calculated in the various leads. We attained the following results: patients with WPW syndrome exhibited, with respect to controls, longer M-QRS (P < 0.001) and M-QTec (P < 0.001) values, despite similar M-QTe (P = NS), M-JT (P = NS) and M-JTc (P = NS). QRSd did not differ in the two groups(P = NS), while QTd and QTcd both resulted significantly greater in pre-excited subjects (P < 0.001). In the WPW group, QRSd was not related either to QTd (r = 0.325, P = NS) or to QTcd (r = 0.148, P = NS), while in the controls there was a significant relation between QRSd and both QTd (r = 0.522, P = 0.004) and QTcd (r = 0.379, P = 0.042). Our findings suggest that the presence of ventricular pre-excitation does not determine a prolongation of the mean ventricular recovery time, but increases regional discrepancies of the re-polarization process. This assumption is supported by the observation of greater values of QTd and QTcd associated with a similar QRSd.

Reasons for prolonged or failed attempts at radiofrequency catheter ablation of accessory pathways

OBJECTIVES

The purpose of this study was to categorize the reasons for a prolonged or failed procedure in a series of patients undergoing catheter ablation of an accessory pathway.

BACKGROUND

Radiofrequency ablation of accessory pathways at times requires a lengthy procedure or a second ablation session, or both, and not prior studies have systematically investigated the reasons for this.

METHODS

In a consecutive series of 619 patients undergoing catheter ablation of an accessory pathway, the mean ablation time +/- SD was 68 +/- 64 min. The subjects of this study were 14 patients who had an ablation time >2 SD greater than the mean (>196 min) and 51 patients who required a second ablation session for a successful outcome. The accessory pathway in the 65 patients in this study was located in the right free wall in 19 patients (29%), septum in 14 (22%) and left free wall in 32 (49%).

RESULTS

The primary reasons for a lengthy or failed ablation attempt were 1) inability to position the ablation catheter at the effective target site (16 patients, 25%); 2) instability of the ablation catheter or inadequate tissue contact at the target site, or both (15 patients, 23%); 3) mapping error due to an oblique course of the accessory pathway (7 patients, 11%); 4) failure to recognize a posteroseptal accessory pathway as being left-sided instead of right-sided (4 patients, 6%); 5) other errors in accessory pathway localization (6 patients, 9%); 6) epicardial location of the accessory pathway (5 patients, 8%); 7) recurrent atrial fibrillation (2 patients, 3%); 8) occurrence of a complication (2 patients, 3%); 9) unusual right-sided accessory pathway that inserted in the anterior right ventricle, 2 cm away from the lateral tricuspid annulus (1 patient, 1.5%); and 10) unexplained factors (7 patients, 11%). The most common effective strategies employed to achieve a successful outcome in these patients were 1) substitution of a more experienced operator; 2) use of ablation catheters of varying configurations; 3) switching from a retrograde aortic to a trans-septal approach; 4) switching from an inferior to a superior vena caval approach; 5) use of a 60-cm guiding sheath; 6) detailed mapping of the atrial or ventricular insertion of the accessory pathway; and 7) searching within the coronary sinus for a presumed accessory pathway potential.

CONCLUSIONS

A lengthy or failed attempt at catheter ablation of an accessory pathway may be due to a variety of reasons, the most common of which are problems related to some aspect of catheter manipulation and errors in accessory pathway localization. Knowledge of the most common reasons for a lengthy or ineffective procedure may facilitate successful outcome of accessory pathway ablation.

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.

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)

Initial depolarizing potentials in Wolff-Parkinson-White syndrome using signal-averaged electrocardiograms: correlation with reciprocating tachycardia

Initial depolarizing potentials were examined in patients with Wolff-Parkinson-White (WPW) syndrome using signal-averaging techniques. In all, 25 WPW patients and 21 age-matched healthy children were studied. Ten of the patients were symptomatic and 15 were asymptomatic. Symptomatic patients with supraventricular tachycardias had longer durations of low-amplitude signals (LAS) < 40 mu V in the initial portion of the QRS complex (initial LAS, 49 +/- 7 ms vs. 37 +/- 9 ms, p < 0.01) and lower root-mean-square (RMS) voltage in the initial 40 ms of the QRS complex (initial RMS, 12 +/- 4 mu V vs. 23 +/- 8 mu V, p < 0.01) compared with asymptomatic patients. When a symptomatic patient was defined as having an initial LAS of > 46 ms or an initial RMS of < 15 mu V, the sensitivity and specificity for predicting documented supraventricular tachycardia were 100 and 67%, respectively. These SA-ECG findings may reflect instability of conduction in symptomatic patients through an accessory pathway and may identify those at high risk for supraventricular tachycardia.

Posteroseptal accessory pathways: an overview of anatomical characteristics, electrocardiographic patterns, electrophysiological features, and ablative therapy

First, the posteroseptal region of the heart is probably the most complex area among those that harbor AV accessory fibers and a firm grasp of the anatomical characteristics of this region may facilitate achieving a successful AP ablation. Second, there is no sharp demarcation between the posteroseptal area and its surrounding regions including mid-septal, left posterior paraseptal, and right posterior paraseptal locations. Therefore, there are some inevitable overlaps between the electrocardiographic and electrophysiological features of APs located in the posteroseptal region and those areas immediately adjacent to it. Third, in the vast majority of cases, successful ablation can be achieved using a right atrial approach. Therefore, dividing posteroseptal APs into right- or left-sided pathways may only be useful for describing their ECG or electrophysiological characteristics with little or no value in predicting the site of successful ablation. Fourth, it seems advisable to attempt efforts to induce functional bundle branch block during orthodromic tachycardia and assess its effect on the VA interval. Ventriculoatrial interval prolongation due to right bundle branch block strongly favors a right free-wall or anteroseptal AP location. Prolongation of the VA interval by 30 msec or less in response to left bundle branch block is compatible with a posteroseptal location. In this situation, the mapping and ablative efforts should primarily be focused on the right atrial approach, including the terminal coronary sinus. If left bundle branch block causes VA interval lengthening of 30 msec or greater, the AP is most likely in the left free-wall region, including the posterior paraseptal area. Finally, the presence of APs having an intimate relationship with the middle cardiac (posterior interventricular) vein or the coronary sinus pouch, although exceedingly uncommon, should be considered in difficult cases in which radiofrequency applications to the conventional posteroseptal locations are unsuccessful. Such cases may require coronary sinus venography for better visualization and precise mapping of the terminal sinus complex.

Clinical anatomy of the atrioventricular junctions

OBJECTIVES

This study reevaluated the anatomy of the areas anterior and posterior to the atrioventricular (AV) septal structures, previously said to represent anterior and posterior septal areas.

BACKGROUND

In descriptions of the locations of accessory AV pathways within the AV junctions, four regions have been recognized: the left and right free walls and the anterior and posterior septums. On the basis of known facts concerning cardiac structure, it is questionable whether these so-called septums are truly septal.

METHODS

Ten human hearts were dissected to elucidate the clinical anatomy of these purportedly septal regions, together with the overall arrangement of the AV junctions.

RESULTS

The true septal components of the AV junctions are the muscular and membranous AV septal areas. These separate the cavity of the right atrium from that of the left ventricle. The region previously designated as the anterior septum is part of the right parietal junction. It is contiguous with the membranous part of the septum but extends anteriorly and laterally from the septum as part of the supraventricular crest of the right ventricle ("crista supraventricularis"). In the region posterior to and beneath the mouth of the coronary sinus, only the most anterior extent, in continuity with the central fibrous body, is part of the muscular AV septum. The posterior extent of this area roofs over the diverging right and left ventricular walls and is filled in with fibroareolar tissue of the AV groove.

CONCLUSIONS

The larger part of the regions anterior and posterior to the true AV septal areas are not septal but are parts of the parietal AV junctions. An understanding of these anatomic relations is essential for those wishing to modify conduction across the AV junctions.

Cardiac depolarization and repolarization in Wolff-Parkinson-White syndrome

Delta wave and QRS complex polarities have been extensively studied in preexcitation syndromes. However, only limited data exist about ventricular depolarization and repolarization in the setting of maximal preexcitation in relation to the site of insertion of the accessory pathway. Therefore this study was designed to systematically analyze cardiac depolarization and repolarization in patients with maximal preexcitation. We analyzed the polarity of the QRS complex and T wave on the frontal plane on the conventional 12-lead electrocardiogram in 118 patients with maximal preexcitation. Fast atrial pacing was used to provoke maximal ventricular preexcitation. The 32 patients with a left lateral accessory pathway showed right-axis deviation of the QRS complex (110 +/- 20 degrees) with a left-axis deviation of the T-wave axis (-40 +/- 25 degrees). The 54 patients with a posteroseptal accessory pathway had a left axis of the QRS complex (-50 +/- 20 degrees) with a right-axis deviation of the T-wave axis (95 +/- 15 degrees). The 11 patients with a right lateral accessory pathway had a left axis of the QRS complex (-40 +/- 20 degrees) and a right axis of the T wave (110 +/- 10 degrees). In 7 patients with a left anterolateral accessory pathway and 14 patients with a right anteroseptal accessory pathway, the axis of the QRS complex was 50 +/- 25 degrees and 45 +/- 20 degrees, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Transcatheter ablation of posteroseptal accessory pathways using a venous approach and radiofrequency energy

BACKGROUND

The efficacy of transcatheter ablation of atrioventricular (AV) accessory pathways (APs) located in the posteroseptal region using a right atrial approach and radiofrequency energy was evaluated.

METHODS AND RESULTS

Fifty consecutive patients with APs in the posteroseptal region underwent radiofrequency catheter ablation. Manifest preexcitation was present in 36 patients and a concealed AP in 14. In 18 patients (group 1), the ventriculoatrial (VA) interval during orthodromic tachycardia was prolonged by 21 +/- 7 milliseconds (range, 10 to 30 milliseconds) with functional left bundle-branch block. In 16 patients (group 2), functional left bundle-branch block caused no VA interval prolongation. The remaining 16 patients (group 3) had no inducible left bundle-branch block during orthodromic tachycardia. Functional right bundle-branch block was induced in 30 patients with no effect on the VA interval. In group 1, of 14 patients with manifest preexcitation during sinus rhythm, 10 patients had a positive delta wave in lead V1. Of 10 group 2 patients with manifest preexcitation, only 5 had a positive delta wave in lead V1. In group 3, of 12 patients with manifest preexcitation, 7 exhibited a positive delta wave in lead V1. All posteroseptal APs were successfully ablated, and this was achieved via a right atrial approach in 48 patients and left ventricular approach in only 2. Successful sites were at the posteroseptal region of the tricuspid annulus (30 patients), within the terminal 1 cm of the coronary sinus including its ostium (16 patients), and at the inferomedial aspect of the right atrium posterior to the coronary sinus ostium (2 patients). The posteroseptal region of the left ventricle was the site of successful ablation in 2 patients. Six patients with a recurrence of AP conduction required a repeat ablation, with successful results in 5. Thirty-five patients had a complete electrophysiological evaluation 2 to 3 months after their successful ablation and were found to have no functioning AP. In 49 patients with a final successful ablation, no recurrence of symptoms was noted during a mean follow-up period of 12 +/- 9 months. Complications occurring in 3 patients were cardiac tamponade requiring surgical drainage and repair of a right ventricular tear, pericardial effusion with no hemodynamic consequence that spontaneously resolved, and a transient 2:1 atrioventricular block.

CONCLUSIONS

These data suggest that posteroseptal APs are amenable to successful ablation using a right atrial approach. Success was achieved in 47 cases (94%) in this series even though the ECG and/or electrophysiological characteristics of the posteroseptal APs of some patients were suggestive of "left-sided" pathways.

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

INTRODUCTION

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

METHODS AND RESULTS

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

CONCLUSION

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

The 12-lead electrocardiogram in midseptal, anteroseptal, posteroseptal and right free wall accessory pathways

The 12-lead electrocardiograms of 50 patients with 1 anterogradely conducting accessory pathway were analyzed to obtain characteristics of electrocardiographic findings in the midseptal, anteroseptal, true posteroseptal and right free wall accessory pathway locations. Locations were confirmed by surgery (33 patients) or radiofrequency catheter ablation (17 patients). This study analyzed (1) QRS in the frontal plane, (2) delta wave axis in the frontal plane, (3) the angle between QRS and delta wave axes, (4) the R/S ratio in lead III, (5) negativity of delta wave in inferior leads, and (6) the R/S ratio in precordial leads.(ABSTRACT TRUNCATED AT 250 WORDS)

A unique preexcitation pattern related to an atypical anteroseptal accessory pathway

Accessory atrioventricular pathways have traditionally been classified by anatomical location to four areas, namely anteroseptal, posteroseptal, and right and left free walls. Each of these have been associated with a relatively distinct preexicitation pattern electrocardiographically. We describe a patient with a unique ECG pattern suggesting preexicitation to the right ventricular outflow region. Preoperative and intraoperative electrophysiological testing confirmed the presence of an accessory pathway with an atrial insertion site near the His bundle, decremental anterograde conduction, and a ventricular insertion site in the upper part of the interventricular septum. Operative ablation near the atrial insertion site eliminated preexicitation.

Characteristic findings on the standard 12-lead ECG in patients with the fasciculoventricular Mahaim fiber

Standard 12-lead electrocardiograms with a Q wave in lead V1 were obtained from 32 subjects without organic cardiac disease and analyzed for features that might characterize an abnormal atrioventricular conduction through the fasciculoventricular Mahaim fiber. Following an infusion of ajmaline, the Q wave in V1 vanished abruptly and changed to an rS pattern in the 12 ajmaline responders. Discriminant analysis was performed to distinguish the ajmaline responders from the others. The explanatory variables were number of precordial leads with the abnormal Q wave, existence of the septal q waves, existence of the slurring of the Q wave in V1, existence of clockwise rotation, and existence of high voltage (RV5 + SV1 > 3.5 mV). Three variables, the absence of the septal q waves, the presence of the slurring, and the absence of clockwise rotation, were found to predict a positive response to ajmaline (discriminant probability = 77%). These findings associated with the Q wave in V1 suggest that the fasciculoventricular fiber may be present.

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.

Adenosine and the treatment of supraventricular tachycardia

Adenosine has recently become widely available for the treatment of paroxysmal supraventricular tachycardia. In order to evaluate its role in the management of arrhythmias, we have reviewed the literature on the cellular mechanisms, metabolism, potential for adverse effects, and clinical experience of the efficacy and safety of intravenous adenosine. Adenosine produces transient atrioventricular nodal block when injected as an intravenous bolus. This is of therapeutic value in the conversion to sinus rhythm of the majority of paroxysmal supraventricular tachycardias, which involve the atrioventricular node in a re-entrant circuit. The mean success rate was 93% from over 600 reported episodes. Compared with other antiarrhythmic agents, adenosine is remarkable for its rapid metabolism and brevity of action, with a half-life of a few seconds. It commonly produces subjective symptoms, particularly chest discomfort, dyspnea, and flushing, which are of short duration only. No serious adverse effect has been reported. Arrhythmias may recur within minutes in a minority of patients. Comparative studies have shown that adenosine is as effective as verapamil in the treatment of supraventricular tachycardia, and has less potential for adverse effects. Patients with supraventricular tachycardia should initially be treated using vagotonic physical maneuvers. Immediate electrical cardioversion is indicated if the arrhythmia is associated with hemodynamic collapse. Adenosine is the preferred drug in those patients in whom verapamil has failed or may cause adverse effects, such as those with heart failure or wide-complex tachycardia. The safety profile of adenosine suggests that it should be the drug of first choice for the treatment of supraventricular tachycardia, but only limited comparative data to support this view are available at present.

Localization of accessory pathways in Wolff-Parkinson-White syndrome by high-resolution magnetocardiographic mapping

Fifteen patients with Wolff-Parkinson-White syndrome were studied with standard 12-lead electrocardiogram, invasive electrophysiologic study, and high-resolution magnetocardiographic (MCG) mapping. In addition, intraoperative epicardial mapping was performed in seven surgically treated patients. The MCG characteristics of ventricular preexcitation for different locations of the atrioventricular accessory pathways were described in terms of morphology and field patterns. Three mathematical source models in semi-infinite conducting space were used for localization computations: the current dipole model, the truncated current multipole model and the magnetic dipole model. Finally, the localization results of MCG and invasive mappings and electrocardiograms were compared. The mean three-dimensional distance between the localization results obtained from MCG maps and electrophysiologic study was 3.9 cm for the magnetic dipole model, 4.8 cm for the truncated current multipole model, and 7.3 cm for the current dipole model. The corresponding distances in the seven intraoperatively mapped cases were 2.3 cm for the magnetic dipole model, 5.2 cm for the truncated current multipole model, and 6.3 cm for the current dipole model. In conclusion, noninvasive MCG mapping may significantly contribute to the invasive catheter mapping for optimal preoperative localization of preexcitation site and atrioventricular accessory pathways in Wolff-Parkinson-White syndrome.

Catheter ablation from right atrium of anteroseptal accessory pathways using radiofrequency current

Catheter ablation with radiofrequency current has recently been introduced as a therapeutic regimen for symptomatic patients with the Wolff-Parkinson-White syndrome or atrioventricular (AV) tachycardia mediated by a retrogradely conducting (concealed) accessory AV pathway. These pathways may be located, although infrequently, in the anteroseptal region of the heart in close proximity to the AV node-His bundle conduction system. Any attempt to interrupt an anteroseptal accessory pathway therefore is subject to the potential complication of inadvertent impairment of normal AV conduction. This study was conducted to establish whether abolition of anteroseptal accessory pathways by radiofrequency current aimed at the atrial as opposed to the ventricular insertion of the pathway can be achieved with preservation of AV node-His bundle conduction. Twelve patients (mean age 37 +/- 13 years; 10 with Wolff-Parkinson-White syndrome, 2 with a concealed accessory pathway) were studied. In the majority of patients, radiofrequency current (500 kHz; mean energy 577 +/- 207 J) was applied through a steerable catheter with a long tip electrode placed in the anterior septal space at the atrial aspect of the tricuspid anulus, with the intention to destroy the atrial insertion of the accessory pathway. All pathways were successfully ablated. The AV node or His bundle conduction was not impaired in any patient. Right bundle branch block was induced in two patients (17%). There were no complications related to the procedure. It is concluded that catheter ablation from the right atrium using radiofrequency current provides effective and safe interruption of anteroseptal accessory pathways with good preservation of the normal conduction system.

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.

Phase image triangulation of accessory pathways in patients undergoing catheter ablation of posteroseptal pathways

The outcome of posteroseptal accessory pathway ablation by direct current (DC) shocks delivered just outside the os of the coronary sinus was studied in 21 patients. Electrocardiographic and electrophysiological parameters as well as phase image patterns of equilibrium multiple-gated blood-pool scintigrams were studied to determine their usefulness in predicting the success of ablation. A second free-wall pathway was documented by electrophysiological or surgical findings in six patients, and the value of phase images in detecting this second pathway was studied as well. Ablation was successful in 57%. The cumulative mean energy of DC shocks amounted to 524 +/- 170 joules and was not predictive of ablation outcome, neither was the mean ventriculoatrial (VA) conduction time. The predictive value of the 12-lead maximally preexcited electrocardiogram was poor in the 15 patients with a single posteroseptal bypass tract. A new method to triangulate the site of the earliest phase angle on the atrioventricular (AV) valve plane successfully localized the bypass pathway in 14 of those patients. No specific phase pattern predicted successful ablation except for a symmetrical, concentric peripheral phase progression found to be predictive of ablation success in the four patients who showed this pattern. Phase analysis was able to localize the second, nonposteroseptal pathway in four of six patients. This study showed that a concentric peripheral phase progression in the gated blood-pool scintigrams is predictive for ablation success in patients with posteroseptal pathways. A free-wall localization of the earliest phase angle is suggestive of a second bypass tract in this area.

An artificial neural network to localize atrioventricular accessory pathways in patients suffering from the Wolff-Parkinson-White syndrome

The electrocardiographic localization of atrioventricular accessory pathways has been extensively described in the literature by a number of well-known electrophysiologists and surgeons. These descriptions, often represented as decision trees, are useful, but do not apply in all cases. To formalize the process of determining the proper localization, this expert human knowledge could be represented in an expert system. But since reasoning is partly based on the use of heuristic knowledge, and are often not represented in the written description of the human expert, the results will be suboptimal. On the other hand, by using a self-learning neural network approach, the causal relations between input (polarity of the delta waves) and output (the correct localization) do not have to be defined by the expert. It is derived by the neural network, by analyzing a learning set of cases consisting of the ECG plus the corresponding correct localization. In our set of 60 cases, 2 hours of training were required to learn how to localize all cases correctly. From a control set of 25 cases, 23 were interpreted by the system satisfactorily.

CONCLUSION

the neural network approach can be useful in situations where causal relations between the electrocardiogram and underlying mechanism are partly undefined.

Comparative accuracy of the vectorcardiogram and electrocardiogram in the localization of the accessory pathway in patients with Wolff-Parkinson-White syndrome: validation of a new vectorcardiographic algorithm by intraoperative epicardial mapping and electrophysiologic studies

The scalar electrocardiograms (ECGs) and vectorcardiograms (VCGs) of 41 patients with Wolff-Parkinson-White (WPW) syndrome were used to compare the accuracy of these techniques in the identification of the site of preexcitation. The location of the accessory pathway (AP) was determined by endocavitary electrophysiologic studies in all patients and the location was confirmed during intraoperative epicardial mapping in 28 of them. The ECGs were classified according to Gallagher's criteria and with Milstein's algorithm, whereas the VCGs were classified according to a new two-step algorithm. The presence of multiple accessory pathways and coexisting myocardial infarctions were major limitations in both the VCG and ECG classification procedures. In patients with a single accessory pathway, three AP localizations (right free ventricular wall, posterior, or left free ventricular wall) were identified with the first step of the VCG algorithm, with an overall sensitivity (96.5%), specificity (90.7%), and positive predictive values (80%) that were greater than those obtained with the ECG Milstein algorithm (77.1%, 91.5%, and 75%, respectively). The second step of the VCG algorithm made it possible to identify an AP location in one of the following sites: anterior right, lateral right, posterior right, posterior left, lateral left, or anterior left ventricle. The overall sensitivity, specificity, and positive predictive values were greater for the second step of the VCG algorithm than for the ECG criteria proposed by Gallagher (43.6% versus 39.3%, 92.1% versus 87.4%, and 51.5% versus 33.3%, respectively). It was concluded that the VCG seems to be more specific and sensitive than the ECG in the identification of the preexcitation site and should be given preference in the initial evaluation of the WPW syndrome.