Accessory atrioventricular pathway in an infant: prediction of location with body surface maps and ablation with cryosurgery

Electrocardiographic body surface potential mapping in the Wolff-Parkinson-White syndrome. Noninvasive determination of the ventricular insertion sites of accessory atrioventricular connections

BACKGROUND

A reliable, noninvasive procedure to determine the location of accessory atrioventricular connections in patients with Wolff-Parkinson-White syndrome would add an important diagnostic tool to the clinical armamentarium.

METHODS AND RESULTS

Body surface potential mapping (BSPM) using 180 electrodes in various-sized vests and displayed as a calibrated color map was used to determine the ventricular insertion site of the accessory atrioventricular (AV) connections in 34 patients with Wolff-Parkinson-White syndrome. Attempts were made to determine the 17 ventricular insertion sites described by Guiraudon et al. All 34 patients had an electrophysiologic study (EPS) at cardiac catheterization, and 18 had surgery so the ventricular insertion sites could be accurately located using EPS at surgery. A number of physiologic observations were also made with BSPM.

CONCLUSIONS

The following conclusions were drawn: 1) BSPM using QRS analysis accurately predicts the ventricular insertion site of accessory AV connections in the presence of a delta wave in the electrocardiogram; 2) the ventricular insertion sites of accessory AV connections determined by BSPM and by EPS at surgery were identical or within one mapping site (1.5 cm or less) in all but four of 18 cases; three of the four exceptions had more than one accessory AV connection, and the other had a very broad ventricular insertion; 3) BSPM and EPS locations of the accessory AV connections correlated very well in the 34 cases despite the fact that BSPM determines the ventricular insertion site and EPS determines the atrial insertion site of the accessory AV connection; 4) as suggested by the three cases of multiple accessory AV connections, EPS and BSPM may be complementary since BSPM identified one pathway and EPS identified the other (in the case with a broad ventricular insertion, BSPM and EPS demonstrated different proportions of that insertion); 5) BSPM using ST-T analysis is very much less accurate in predicting the ventricular insertion site of accessory AV connections unless there is marked preexcitation; 6) standard electrocardiography using the Gallagher grid methodology (but with no attempt at stimulating maximal preexcitation) was not as accurate as QRS analysis of BSPM in predicting the ventricular insertion site of the accessory AV connection; however, exact comparison is hampered by the different number and size of the Gallagher and Guiraudon insertion sites; 7) BSPM using QRS analysis appears to be very accurate in predicting right ventricular versus left ventricular posteroseptal accessory AV connections; 8) typical epicardial right ventricular breakthrough, indicative of conduction via the specialized AV conduction system, occurs in all patients with left ventricular free wall accessory AV connections; 9) epicardial right ventricular breakthrough was not observed in cases with right ventricular free wall or anteroseptal accessory AV connections; 10) epicardial right ventricular breakthrough can occur in the presence of posteroseptal accessory AV connections, whether right or left ventricular; and 11) the delay in epicardial right ventricular breakthrough in cases with left ventricular insertion may provide a marker to estimate the degree of ventricular preexcitation.

Body surface mapping of ectopic left and right ventricular activation. QRS spectrum in patients without structural heart disease

The value of simultaneous 62-lead electrocardiographic recordings in localizing the site of origin of ectopic ventricular activation in a structurally normal heart was assessed by examining body surface QRS integral maps in 12 patients during left and right ventricular (LV and RV) pacing at 182 distinct endocardial sites. A data base of 38 characteristic mean integral maps was composed after visually selecting subgroups with nearly identical total QRS integral morphology and numerically evaluating intrasubgroup pattern uniformity and intersubgroup pattern variability. Corresponding endocardial pacing site locations were computed by a biplane cineradiographic method and outlined as segments on a standardized LV and RV polar projection. LV pacing resulted in 25 markedly different mean total QRS integral patterns, showing higher electrocardiographic sensitivity for anteroseptal (18 patterns) compared with posterolateral regions (seven patterns). RV pacing demonstrated 13 mean total QRS integral patterns, exhibiting less intersubgroup variation and comparatively low electrocardiographic sensitivity for the basal anterior and outflow regions. Comparison of LV with RV pacing revealed that QRS configurations produced at LV apical and LV midseptal sites closely resembled QRS configurations generated at RV apical, RV septal, and RV anterior sites, respectively. Total QRS time integral amplitudes showed considerable intrasubgroup variation but permitted global differentiation of spatially similar QRS patterns obtained during pacing at LV and RV sites. This study demonstrates that the QRS pattern of the total body surface electrocardiogram allows discrimination among 38 different LV and RV segments of ectopic endocardial impulse formation in patients with normal cardiac anatomy.

Noninvasive recovery of epicardial potentials in a realistic heart-torso geometry. Normal sinus rhythm

The inverse problem in electrocardiography implies the reconstruction of electrical events within the heart from information measured noninvasively on the body surface. Deduction of these electrical events is possible from measured epicardial potentials, and, thus, a noninvasive method of recovering epicardial potentials from body surface data is useful in experimental and clinical studies. In the present study, an inverse method that uses Tikhonov regularization was shown to reconstruct, with good accuracy, important events in cardiac excitation. The inverse procedure was employed on data obtained from a human-torso tank in which a beating canine heart was placed in the correct anatomical position. Comparison with the actual, measured epicardial potentials indicates that positions and shapes of potential features (maxima, minima, zero potential line, saddles, etc.) are recovered with good accuracy throughout the QRS. An error in position of up to 1 cm is typical, while amplitudes are slightly diminished. In addition, application was extended from the above setting, in which the geometry was precisely known and potentials at a large number of leads were measured accurately, to a situation that is more representative of clinical and experimental settings. Effects of inaccuracy in location of the position of the heart were examined. A stylized torso that approximates the actual geometry was designed, and its performance in the inverse computations was evaluated. A systematic method of reduction of the number of leads on the body surface was proposed, and the resulting lead configurations were evaluated in terms of the accuracy of inverse solutions. The results indicate that the inverse problem can be stabilized with respect to different types of uncertainties in measured data and offer promise in the use of the inverse procedure in clinical and experimental situations.

Intracardiac recording by catheter electrode of accessory pathway depolarization

At electrophysiologic study in a patient with the Wolff-Parkinson-White syndrome, intracardiac catheter recordings demonstrated a deflection that occurred 30 ms before ventricular activation. The rapid deflection was present during ventricular preexcitation but not during normal atrioventricular conduction. All QRS complexes were preexcited to varying degrees during atrial fibrillation, yet the deflection consistently preceded ventricular activation by 30 ms. This deflection most likely represents the rare recording of a Kent bundle depolarization with an intracardiac electrode catheter.

Localization of the site of ventricular preexcitation with body surface maps in patients with Wolff-Parkinson-White syndrome

Forty-nine patients with Wolff-Parkinson-White syndrome, ages 7 weeks to 51 years, were studied with isopotential body surface maps during normal sinus rhythm, atrial pacing or induced atrial fibrillation. The location of the accessory pathway was determined by multicather electrophysiologic study or surgical ablation of the accessory pathway. When fusion was minimized and ventricular activation primarily controlled by a single accessory pathway, the distribution of positive and negative potentials on the anterior and posterior torso during QRS (observed at 40 msec) and the ST segment were an excellent index of the location of the site of the accessory pathway. The relationship between a specific sequence of QRS-T wave body surface maps and a specific preexcitation site was similar from patient to patient in the presence of marked differences in age, size, and different cardiac status due to structural congenital cardiac defects. The localization of the site of the accessory pathway using distributions too early in QRS (before 40 msec) was unreliable because the early distributions varied from patient to patient for the same preexcitation site; however, the potential distributions during the ST segment were both stable and consistent from patient to patient for the same preexcitation site. The presence of significant fusion of ventricular activation initiated via a single accessory pathway and the normal conduction system or via multiple accessory pathways complicated the interpretation of body surface distributions. Thus, one can predict accurately at least seven preexcitation sites by the combined use of QRS and ST-segment body surface maps.

Electrophysiologic evaluation and surgical correction of Wolff-Parkinson-White syndrome in children

The Wolff-Parkinson-White syndrome is due to a congenital heart malformation that is the result of one or more persistent anomalous atrioventricular pathway(s). While supraventricular tachycardia is the most commonly associated arrhythmia, there is a wide spectrum of associated arrhythmias including fatal ventricular fibrillation. It is now known that surgical ablation of the anomalous pathway(s) can result in complete cure of arrhythmias in some patients. The purpose of this report is to describe the current methods used for the preoperative and operative electrophysiologic evaluation and surgical treatment in children with the Wolff-Parkinson-White syndrome, as illustrated by the case presentation of a normal eight-year-old patient who had ventricular fibrillation.