Initial forces of ventricular depolarization in the Wolff-Parkinson-White Syndrome. Analysis based upon localization of the accessory pathway by epicardial mapping

Engineered electrical conduction tract restores conduction in complete heart block: from in vitro to in vivo proof of concept

BACKGROUND

Cardiac electrical conduction delays and blocks cause rhythm disturbances such as complete heart block, which can be fatal. Standard of care relies on electronic devices to artificially restore synchrony. We sought to create a new modality for treating these disorders by engineering electrical conduction tracts designed to propagate electrical impulses.

OBJECTIVES

This study sought to create a new approach for treating cardiac conduction disorders by using engineered electrical conduction tracts (EECTs).

METHODS

Paramagnetic beads were conjugated with an antibody to gamma-sarcoglycan, a cardiomyocyte cell surface antigen, and mixed with freshly isolated neonatal rat ventricular cardiomyocytes. A magnetic field was used to pattern a linear EECT.

RESULTS

In an in vitro model of conduction block, the EECT was patterned so that it connected 2 independently beating neonatal rat ventricular cardiomyocyte monolayers; it achieved coordinated electrical activity, with action potentials propagating from 1 region to the other via EECT. Spiking the EECT with heart-derived stromal cells yielded stable structures with highly reproducible conduction velocities. Transplantation of EECTs in vivo restored atrioventricular conduction in a rat model of complete heart block.

CONCLUSIONS

An EECT can re-establish electrical conduction in the heart. This novel approach could, in principle, be used not only to treat cardiac arrhythmias but also to repair other organs.

Localization of Accessory Pathways in the Wolff-Parkinson-White Pattern?Physician Versus Computer Interpretation of the Same Algorithm

BACKGROUND

There are several published algorithms for the prediction of accessory pathway (AP) location in the Wolff-Parkinson-White syndrome from the 12-lead electrocardiogram (ECG). Most depend on stepwise criteria, and minor disagreements between observers over QRS transition point or delta wave axis may lead to different classification of pathway location. We compared the utility of a computerized program in identifying pathway location from the ECG using the algorithm published by Fitzpatrick and coworkers(3) against physician assessment with the same algorithm.

METHODS

Thirty-one 12-lead ECGs with an overt preexcitation pattern were examined by three physicians and AP localized to one of eight anatomical sites using the Fitzpatrick algorithm, with disagreements resolved by consensus. Similarly, pathway location was determined by the Glasgow ECG program with the Fitzpatrick algorithm incorporated into its logic.

RESULTS

The agreement between each physician and their consensus was 28/31, 29/31, and 29/31. Similarly, assessment by the Glasgow program produced agreement with the physician consensus in 29/31 cases. Of the 24 patients who underwent radiofrequency ablation, the program localized the pathway to the true or adjacent annular region in 20, compared to 20/24 by physician assessment of the algorithm, producing a similar predictive accuracy to published data.

CONCLUSION

This study has shown that incorporation of the Fitzpatrick algorithm for AP location into a widely used computer program results in the same level of performance as that of experienced physicians and may be useful in clinical practice as an aid to referral for electrophysiological study and ablation.

Noninvasive three-dimensional activation time imaging of ventricular excitation by means of a heart-excitation model

We propose a new method for imaging activation time within three-dimensional (3D) myocardium by means of a heart-excitation model. The activation time is estimated from body surface electrocardiograms by minimizing multiple objective functions of the measured body surface potential maps (BSPMs) and the heart-model-generated BSPMs. Computer simulation studies have been conducted to evaluate the proposed 3D myocardial activation time imaging approach. Single-site pacing at 24 sites throughout the ventricles, as well as dual-site pacing at 12 pairs of sites in the vicinity of atrioventricular ring, was performed. The present simulation results show that the average correlation coefficient (CC) and relative error (RE) for single-site pacing were 0.9992+/-0.0008/0.9989+/-0.0008 and 0.05+/-0.02/0.07+/-0.03, respectively, when 5 microV/10 microV Gaussian white noise (GWN) was added to the body surface potentials. The average CC and RE for dual-site pacing were 0.9975+/-0.0037 and 0.08+/-0.04, respectively, when 10 microV GWN was added to the body surface potentials. The present simulation results suggest the feasibility of noninvasive estimation of activation time throughout the ventricles from body surface potential measurement, and suggest that the proposed method may become an important alternative in imaging cardiac electrical activity noninvasively.

ESCWGA/NASPE/P experts consensus statement: living anatomy of the atrioventricular junctions. A guide to electrophysiologic mapping. Working Group of Arrhythmias of the European Society of Cardiology. North American Society of Pacing and Electrophysiology

Current nomenclature for the AV junctions derives from a surgically distorted view, placing the valvar rings and the triangle of Koch in a single plane with anteroposterior and right-left lateral coordinates. Within this convention, the aorta is considered to occupy an anterior position, whereas the mouth of the coronary sinus is shown as being posterior. Although this nomenclature has served its purpose for the description and treatment of arrhythmias dependent on accessory pathways and AV nodal reentry, it is less than satisfactory for the description of atrial and ventricular mapping. To correct these deficiencies, a consensus document has been prepared by experts from the Working Group of Arrhythmias of the European Society of Cardiology and from the North American Society of Pacing and Electrophysiology. It proposes a new, anatomically sound, nomenclature that will be applicable to all chambers of the heart. In this report, we discuss its value for description of the AV junctions and establish the principles of this new nomenclature.

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

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

Regular wide QRS complex tachycardia during atrial fibrillation in a patient with preexcitation syndrome: a case report

We report an unusual case of a relatively regular wide QRS complex tachycardia alternating with periods of an irregular narrow QRS complex tachycardia during atrial fibrillation in a patient with Wolff-Parkinson-White syndrome. Both tachycardias resulted from atrial fibrillation, the wide QRS complex tachycardia being due to 2:1 AV conduction of a type I atrial fibrillation across a posteroseptal accessory AV connection.

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)

Usefulness of adenosine in augmenting ventricular preexcitation for noninvasive localization of accessory pathways

Adenosine was administered to test the hypothesis that it would maximize preexcitation and facilitate noninvasive localization of accessory pathways in 22 patients with suspected accessory pathway-mediated tachycardias. Twelve-lead electrocardiograms and 2-dimensional echocardiograms were recorded at baseline and during adenosine-augmented ventricular preexcitation to localize the accessory pathway. Phase analysis was performed on digitized 4-chamber and short-axis views using a first harmonic Fourier transformation. At baseline, 15 patients had manifest preexcitation. In 14 of these patients (93.3%), preexcitation became more prominent after adenosine. Four patients without preexcitation at baseline clearly had it after adenosine. In patients who had preexcitation in response to adenosine, the electrocardiogram correctly identified the accessory pathway locations in 18 of 19 patients at a regional level and was incorrect in 1 of 19 patients. Echocardiographic phase analysis correctly identified the accessory pathway location in all 17 patients, who had technically adequate studies, at a regional level. In conclusion, administration of adenosine accentuates preexcitation, allowing for more accurate electrocardiographic and echocardiographic accessory pathway localization.

Body surface mapping and nontraditional ECG leads in patients with Wolff-Parkinson-White syndrome

A method of ECG mapping from 90 points on the chest surface is described in 41 male and 17 female patients, aged 6 to 59 years. All also underwent invasive electrophysiological investigation and intraoperative epicardial mapping. Fifty-two patients had one, three patients two, and one patient had three anomalous accessory pathways. Two patients had nodoventricular tracts (Mahaim fibers). We distinguished seven zones along the atrioventricular groove (AVG) to compare the data derived from epicardial, endocardial, and body surface mapping. A microcomputer was used for the analysis of all ECGs to construct and analyze the isopotential maps. The criterion for localization of the anomalous accessory pathways was determined after analysis of the data from all 58 patients. The localization criterion was the appearance of a minimal deflection (-0.09 +/- 0.03 mV) on the surface isopotential maps within the first 0.28 msec of the QRS complex. This criterion for localization of anomalous accessory pathways from the chest surface was proposed on the basis of comparison of data from selective coronary angiography, the ventriculogram, and the chest X ray i.e., radiographic-topographic-anatomical data. In 20 patients, 10-20 nontraditional ECG leads were recorded from the chest to reflect the atrioventricular groove. The number of nontraditional ECG leads depended on patient age, weight, and height. Localization of the accessory pathway in one of the seven zones was established by the earliest delta wave and its maximum deviation. It was possible to localize the anomalous accessory pathway and to suspect multiple pathways in 95% of cases using nontraditional ECG leads and the listed criteria.(ABSTRACT TRUNCATED AT 250 WORDS)

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.

Electrocardiographic localization of the site of origin of ventricular tachycardia in patients with prior myocardial infarction

The utility of the 12 lead electrocardiogram (ECG) in identifying the site of origin of sustained ventricular tachycardia in patients with previous myocardial infarction was studied. A new mapping grid, based on biplanar fluoroscopic imaging of the heart, was utilized for the definition of left ventricular endocardial sites. On the basis of QRS configurations resulting from left ventricular endocardial pacing at disparate sites in 22 patients (Group I), ECG features that were specific for particular sites were identified and used to construct an algorithm. Apical and basal sites were differentiated by the QRS configuration in leads V4 and aVR, anterior and inferior sites by that in leads II, III and V6 and septal and lateral sites were differentiated using leads I, aVL and V1. The algorithm was used to predict the site of earliest endocardial activation during 44 episodes of sustained ventricular tachycardia in a second group of 42 patients (Group II) in a blinded fashion. Anterior sites were correctly predicted in 83% of cases, inferior sites in 84%, septal sites in 90% and lateral sites in 82% of cases. Apical and basal sites were each correctly predicted in 70% of cases, whereas intermediate sites were less well predicted (29 to 55%) on the basis of QRS configuration. Precise localization of the site of origin of ventricular tachycardia (in all three planes) was achieved in 17 cases (39%), and in 16 cases (36%) the site of origin was immediately adjacent to the predicted site. Prediction of the site of origin of ventricular tachycardia from the 12 lead ECG may serve as a useful, time-saving adjunct to, but not a substitute for, activation sequence mapping during ventricular tachycardia.

Catheter recording of left atrial activation from left pulmonary artery in the Wolff-Parkinson-White syndrome: validation of the technique with intraoperative mapping results

Accurate localization of accessory pathways (AP) in the Wolff-Parkinson-White (WPW) syndrome requires detailed atrial mapping. Coronary sinus catheterization is so far the most accurate method of left atrial mapping, but it can be technically difficult in some patients. We evaluated the feasibility of left atrial mapping from the left pulmonary artery in 24 patients with WPW syndrome. All patients except one underwent surgical cryoablation of their AP and the results of intraoperative mapping are available for comparison. Mapping in sinus rhythm showed recording of atrial activity in the distal left pulmonary artery occurred 56 +/- 20 ms after activation of high right atrium and 24 +/- 4 ms after activation in the His bundle area, but coincident with left atrial activation in the distal coronary sinus (56 +/- 20 and 53 +/- 13, respectively). Mapping during ventricular pacing or orthodromic tachycardia could differentiate patients as having a right sided, left sided or paraseptal first site of activation. Eleven patients had a left lateral AP, four had a left posterior AP, five had left posteroseptal AP and one had a left anterior AP. The remaining three patients had a right sided AP. Intraoperative results correlated with pre-operative findings in 22 out of 23 (95%) patients who underwent surgical ablation of AP. Thus, recordings form the left pulmonary artery reflect left atrial activity and may be of aid in localizing an AP, especially when coronary sinus recordings cannot be obtained. This technique, however, should not replace the more accurate method of coronary sinus mapping.

Value of the resting 12 lead electrocardiogram and vectorcardiogram for locating the accessory pathway in patients with the Wolff-Parkinson-White syndrome

The resting 12 lead electrocardiogram and vectocardiogram were reviewed in 47 patients with the Wolff-Parkinson-White syndrome (a) who had pre-excitation on the resting 12 lead electrocardiogram, (b) who had a single anterograde conducting accessory pathway assessed and located during preoperative electrophysiological study and during epicardial mapping at operation, and (c) in whom surgical division of the accessory pathway resulted in loss of pre-excitation. The site of the accessory pathway established during operation was compared with that established by evaluating the polarity of the delta wave and QRS complex on the resting 12 lead electrocardiogram. The electrocardiogram was assessed by the Rosenbaum criteria (Wolff-Parkinson-White type A, left-sided pathway; or type B, right-sided pathway), the Gallagher criteria (atrial pacing resulting in maximal pre-excitation), and the World Health Organisation criteria (a composite of previous studies). The Gallagher and World Health Organisation criteria were derived from patients demonstrating maximal pre-excitation that often required atrial pacing. The present study was designed to determine whether these criteria could be accurately applied to the resting 12 lead electrocardiogram on which the degree of pre-excitation was variable. The Rosenbaum criteria correctly identified a left sided accessory pathway in 26 of 34 patients and a right-sided accessory pathway in nine of 13 patients. The Gallagher and World Health Organisation criteria correctly identified the location in only 15 (32%) of the 47 patients. The resting vectorcardiogram was inaccurate for locating the accessory pathway. Although published criteria are useful for identifying the site of the accessory pathway from an electrocardiogram obtained when rapid atrial pacing is being used to achieve maximal pre-excitation, they are not suitable for identifying the exact site of an accessory pathway from the resting 12 lead electrocardiogram.

Concordance of distinguishing electrocardiographic features during sinus rhythm with the location of accessory pathways in the Wolff-Parkinson-White syndrome

Knowledge of the location of accessory pathways in patients with Wolff-Parkinson-White (WPW) syndrome is pertinent to patient management. Despite the recognition that features of delta waves present during maximal preexcitation reflect ventricular activation at different sites around the anulus fibrosus, the value of electrocardiographic patterns observed during sinus rhythm, when ventricular preexcitation is often not maximal for identifying accessory pathway locations, has not been determined. In this study, 12-lead electrocardiograms recorded during sinus rhythm from 66 patients with WPW syndrome were analyzed for delta-wave polarity, QRS axis in the frontal plane, the pattern of precordial R-wave transition, and concordance between electrocardiographic patterns and the site of the accessory pathway determined using catheter and intraoperative computer mapping. Electrocardiograms from patients with left lateral sites showed negative delta waves in leads I or aVL, a normal QRS axis and early precordial R-wave transition (20 of 24 patients); left posterior sites manifested negative delta waves in II, III and aVF and a prominent R wave in V1 (14 of 16 patients); posteroseptal sites had negative delta waves in II, III and aVF, a superior QRS axis and an R less than S in V1 (all 16 patients); right free wall locations manifested negative delta waves in aVR, a normal QRS axis, and R-wave transition in V3-V5 (6 of 6 patients); and anterior septal sites had negative delta waves in V1 and V2, a normal QRS axis, and R-wave transition in V3-V5 (4 of 4 patients). Characteristic electrocardiographic patterns were not observed in 5 patients because of insufficient preexcitation. Each had a left lateral or left posterior pathway. Overall, the proposed electrocardiographic criteria derived during sinus rhythm identified correctly the accessory pathway location in 60 of 66 patients (91%). Thus, the electrocardiogram provides the physician with a reliable noninvasive means of regionalizing the location of accessory pathways in patients with WPW syndrome.

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

The bypass tracts of the WFW syndrome may be situated anywhere along the AV ring. Accurate localization of such tracts has in the past been largely effected by electrophysiologic studies, particularly epicardial mapping. During recent years, however, criteria for localization of the bypass tracts from the conventional 12-lead ECG have become increasingly apparent. The preceding presentation constitutes a review and state of the art governing these rapidly developing diagnostic principles.

When is the vectorcardiogram superior to the scalar electrocardiogram?

The clinical usefulness of the vectorcardiogram is well documented by the numerous reports published in the last 3 decades. It has been found more reliable than the electrocardiogram for the diagnosis of atrial enlargement and right ventricular hypertrophy. It is more sensitive than the electrocardiogram in the recognition of myocardial infarction, especially if the infarction is inferior or if it occurs in the presence of left bundle branch block or left anterior hemiblock. It is helpful in the diagnosis of ventricular pre-excitation and in the localization of the bypass tract. Some repolarization abnormalities are more clearly demonstrated by the vector display. However, some information, such as that on cardiac chamber size and myocardial damage, can also be obtained by other noninvasive tests that are often performed on the same patients. With the increasing awareness of cost-effectiveness of various laboratory procedures in medicine, the vectorcardiogram should no longer be considered a routine cardiac test and should be requested only for a specific clinical purpose. When properly utilized, vectorcardiography should remain a valuable diagnostic as well as teaching tool.

Wolff-Parkinson-White VCG patterns that mimic other cardiac pathologies: a correlative study with the preexcitation pathway localization

Vectorcardiograms (VCGs) of 44 patients with a Wolff-Parkinson-White (WPW) syndrome have been analyzed with the aim to correlate the QRS loop patterns with specific preexcitation sites. The VCG QRS loops were analyzed to determine whether conduction abnormalities and myocardial infarction (MI)-like patterns observed in the WPW syndrome could be related to specific preexcitation sites identified by surgery as well as by body surface potential mapping (BSPM). Left bundle branch block pattern was observed with anteroseptal (AS) preexcitation, anterior MI pattern was seen with lateral right ventricle (LRV) preexcitation, left anterior fascicular block was observed with posterior right ventricle (PRV) preexcitation, inferoposterior and strictly posterior MI pattern was found with posteroseptal (PS) and posterior left ventricle (PLV) preexcitation, right bundle branch block was seen in lateral left ventricle (LLV) preexcitation, and right bundle branch block was observed with left posterior fascicular block in anterior left ventricle (ALV) preexcitation. These VCG criteria seem to identify accurately the preexcitation sites as observed by delta wave BSPM and at surgery investigations. Consequently, they could be useful in localizing the preexcitation site in cases of ambiguous delta vector orientation.

Electrophysiologic profile of asymptomatic Wolff-Parkinson-White pattern

Electrophysiologic testing in patients with asymptomatic Wolff-Parkinson-White syndrome (WPW) may be useful in defining arrhythmic substrates and predictors of fatality. Forty-two patients with asymptomatic WPW, mean age 36 years, underwent electrophysiologic studies and were followed prospectively. They were compared with a matched control group of patients studied within the same period for documented tachycardia associated with the WPW syndrome. Asymptomatic patients had longer anterograde effective refractory periods of the accessory pathway, longer minimum cycle lengths maintaining 1:1 conduction over the accessory pathway, longer minimum RR intervals between consecutive preexcited beats during atrial fibrillation (AF) and longer mean RR intervals during AF than their symptomatic counterparts. Sustained reciprocating tachycardia could not be induced in most patients and induction of AF required rapid atrial pacing in all patients. Nine patients had an anterograde effective refractory period of less than 270 ms and 17% had minimum cycle length less than 250 ms during induced AF. Over a follow-up of 29 +/- 18 months, 1 patient died of noncardiac causes and the rest remained asymptomatic. Thus, patients with asymptomatic WPW have deficient electrophysiologic substrates to maintain orthodromic reciprocating tachycardia under baseline conditions and do not have atrial vulnerability. Seventeen percent of patients had potentially lethal ventricular rates during induced AF.

An evaluation of the diagnostic efficacy of phase analysis of data from radionuclide ventriculograms in patients with Wolff-Parkinson-White syndrome

It has been suggested that phase analysis of radionuclide ventriculograms may be of value for detecting and localising the abnormal sequence of ventricular contraction secondary to Wolff-Parkinson-White (WPW) syndrome. The present study was undertaken to test this hypothesis. The space--time sequences of right- and left-ventricular action obtained from radionuclide ventriculograms obtained during rest studies were evaluated in 8 patients with WPW syndrome (confirmed by 12-lead surface electrocardiography) and compared to those of 14 normal subjects. All of the latter showed a consistent ventricular activation pattern, i.e. the first site of ventricular activity in the upper septal region followed by a second site either at the base of the left ventricle or located apically. It was possible to diagnose 11 of the 14 normal subjects (specificity, 79%) and 7 of the 8 patients (sensitivity, 88%). The 4 patients who had been classified as having a left-sided accessory bundle by surface electrocardiography were likewise diagnosed by phase analysis, as were the 2 patients with a confirmed right-sided bypass tract. Two patients with septal posterior accessory pathways could not be identified by phase analysis. Furthermore, cases with an activation pattern which closely resembled that of the 2 patients with right-sided accessory bundles were found to be normal from their ECGs. It is now necessary to evaluate phase analysis against invasive electrophysiological methods in such patients.

Criteria for intraventricular conduction disturbances and pre-excitation. World Health Organizational/International Society and Federation for Cardiology Task Force Ad Hoc

In an effort to standardize terminology and criteria for clinical electrocardiography, and as a follow-up of its work on definitions of terms related to cardiac rhythm, an Ad Hoc Working Group established by the World Health Organization and the International Society and Federation of Cardiology reviewed criteria for the diagnosis of conduction disturbances and pre-excitation. Recommendations resulting from these discussions are summarized for the diagnosis of complete and incomplete right and left bundle branch block, left anterior and left posterior fascicular block, nonspecific intraventricular block, Wolff-Parkinson-White syndrome and related pre-excitation patterns. Criteria for intraatrial conduction disturbances are also briefly reviewed. The criteria are described in clinical terms. A concise description of the criteria using formal Boolean logic is given in the Appendix. For the incorporation into computer electrocardiographic analysis programs, the limits of some interval measurements may need to be adjusted.

A quantitative method for the localization of the ventricular pre-excitation area in the Wolff-Parkinson-White syndrome using singular value decomposition of body surface potentials

In order to localize quantitatively the site of ventricular pre-excitation, singular value decomposition (SVD) was applied to the body surface potential distributions of patients with the Wolff-Parkinson-White syndrome. The body surface potentials of sixty-two patients were recorded during sinus rhythm and pre-excitation by means of thirty electrodes placed on the anterior thoracic wall. The sites of the anomalous bundles had been determined beforehand by multicatheter electrophysiologic study. Considerable data reduction was obtained by using the SVD technique and displaying the potential distribution during the delta wave on two isofunction maps of the first two positional vectors and their corresponding two singular values (SV). A distinction was made between two types of isofunction maps. A type-S (single extreme) and a type-D (double extremes). A quantitative analysis was performed with the orientation of the zero line on the isofunction map being represented by the angle alpha or beta, and the singular values quotient (SVQ) of the two first singular values. The angle beta belonging to type D was used to subdivide this group of pre-excitation areas. The parameters SVQ and alpha belonging to type-S were illustrated in a graph on which a distinction between the various locations of the pre-excitation areas can be seen.

Wolff-Parkinson-White syndrome and supraventricular tachycardia during infancy: management and follow-up

The records of 90 patients with Wolff-Parkinson-White syndrome who presented with supraventricular tachycardia in the first 4 months of life were reviewed. Among these, 63% were male. Structural heart disease was present in 20%, most commonly Ebstein's anomaly. All patients presented with a regular narrow QRS tachycardia, and pre-excitation became evident only when normal sinus rhythm was established. Only one infant had atrial flutter and none had atrial fibrillation. Type A Wolff-Parkinson-White syndrome was most common (49%), with heart disease occurring in only 5% of these patients. In contrast, heart disease was identified in 45% of those with type B syndrome. Initially, normal sinus rhythm was achieved in 88% of the 66 infants treated with digoxin with no deaths. Normal sinus rhythm resumed after electrical countershock in 87% of the 15 infants so treated. Maintenance digoxin therapy was used in 85 patients. The Wolff-Parkinson-White pattern disappeared in 36% of the patients. Four infants died of cardiac causes during the mean follow-up period of 6.5 years. Two of these four infants had congenital heart disease; the third, with a normal heart initially, developed ventricular fibrillation and died from a cardiomyopathy considered related to resuscitation. The remaining infant, with a normal heart, died suddenly at 1 month of age. All were receiving digoxin. A wide QRS tachycardia later appeared in three patients, all with heart disease, one of whom died.(ABSTRACT TRUNCATED AT 250 WORDS)

Spatial vectorcardiography in the Wolff-Parkinson-White syndrome: correlation with epicardial mapping findings

The spatial vectorcardiograms (VCG) of 13 patients with WPW syndrome due to single accessory pathways were analyzed and correlated with the excitation analysis obtained on epicardial mapping. The azimuth angle of the initial 10 ms cardiac vector was greater than + 90 degrees (directed right and anteriorly) in patients with a left ventricular free wall; it ranged between 0 degree to 90 degrees (left and anteriorly) in those with a left or right paraseptal free wall and was -30 degrees (left and posteriorly) in one patient with a right ventricular free wall location. The elevation angle of the initial 10 and 20 ms cardiac vector was either zero or positive (inferiorly directed) in those with right and left ventricular free wall pathway. Among six patients with a paraseptal location, the elevation angle was negative (superiorly directed) in four and positive in two. Both the patients with a clockwise inscription of a QRS loop in the horizontal plane (HP) had pathways located to the left ventricle. Among the paraseptal group, at surgery, the accessory pathway could not be excised in two in spite of dissection very close to the IV (interventricular) septum. The elevation angle in both these patients was markedly negative (-45 degrees and -62 degrees) in contrast to the other in whom surgical excision was successful.+

Multiple circus movement tachycardias with multiple accessory pathways

A patient with the Wolff-Parkinson-White syndrome manifesting four types of tachycardia is described. The location and the participation during tachycardia of two different types of accessory atrioventricular pathways were documented during a programmed stimulation study. Unusual modes of initiation of tachycardias were observed, such as the initiation of an orthodromic circus movement tachycardia by an atrial premature beat that conducted in anterograde direction down the accessory pathway.

Preexcitation syndromes. Mechanisms and management

Ventricular preexcitation occurs when, in relation to atrial events, some or all of the ventricular muscle is activated earlier by the atrial impulse than would be expected if conduction of the impulse activated the ventricles by way of the normal atrioventricular conduction system. The purpose of this article is to review the pathophysiology of the variants of preexcitation and to discuss the therapeutic approach to patients who have tachyarrhythmias.

Syncope in the Wolff-Parkinson-White syndrome: incidence and electrophysiologic correlates

Syncope in the patient with Wolff-Parkinson-White (WPW) syndrome raises the specter of rapid tachyarrhythmias and the possibility of sudden cardiac death. We reviewed the records of 55 consecutive WPW patients referred for electrophysiologic evaluation of known or suspected arrhythmias to determine the incidence and significance of syncope. Twelve patients (22.6%) reported the occurrence of at least one episode of syncope. In eleven (20%) of these, syncope was preceded by rapid palpitations. Forty-three patients (77.4%) had no syncopal episodes. These two groups did not differ significantly with regard to age, sex, presence of associated cardiac or neurologic disease, drug history or accessory pathway location. There was no significant difference in cycle length of reciprocating tachycardia (syncope = 295.6 +/- 59.8 vs non-syncope = 334.5 +/- 59.6 ms, p less than .5), shortest R-R intervals between preexcited beats (260 +/- 78.6 vs 246.7 +/- 55.4 ms, p less than .5) and average R-R interval (364.4 +/- 37.9 vs 367.4 +/- 77.5 ms, p less than .5) measured during atrial fibrillation. The anterograde effective refractory period of the accessory pathway (292.1 +/- 31.9 vs 299 +/- 58.1 ms, p less than .5) and the shortest cycle length with 1:1 conduction over the accessory pathway (306.7 +/- 75 vs 289.1 +/- 77.5 ms, p less than .5) similarly did not differ. We conclude that syncope occurs in approximately 20% of patients with the Wolff-Parkinson-White syndrome referred for assessment of tachycardia. Patients with syncope do not have distinct clinical features or a more malignant electrophysiologic profile, suggesting that other extracardiac factors may play an important role in the genesis of syncope in this group.

Sequential regional phase mapping of radionuclide gated biventriculograms in patients with sustained ventricular tachycardia: close correlation with electrophysiologic characteristics

Radionuclide (RNA) gated studies were performed during sinus rhythm and during spontaneous or induced sustained ventricular tachycardia (VT) in six patients with clinical VT. Fourier analysis of time-activity variation was used to calculate a RNA phase value for each pixel in the image. Color coding of each pixel according to its calculated phase resulted in a RNA phase map of the ventricles. The following results were considered to be consistent with the known electrophysiology of VT: (1) the phase map correlated with QRS morphology and axis in most but not all tachycardias; (2) earliest phase usually demonstrated the VT origin to be at the border of the ventricular wall motion abnormality; (3) endocardial mapping (available in one patient) showed close correlation with RNA phase mapping; (4) in three patients with ischemic heart disease, VT with left bundle branch block (LBBB) pattern had earliest LV phase along the septum; and (5) for one patient imaged during two different VT morphologies, the tachycardias had earliest phase at different borders of the same wall motion abnormality with differing progression of phase across the ventricles. RNA phase mapping of VT is feasible and appears to provide data consistent with the electrophysiology of this arrhythmia.

Paroxysmal atrial fibrillation in the Wolff-Parkinson-White syndrome

Eighty-eight patients with preexcitation were studied to determine how 30 patients with documented spontaneous paroxysmal atrial fibrillation differed from 58 patients without this arrhythmia. Inducible reentrant tachycardia was present in 23 (77 percent) of the 30 patients with, versus 28 (48 percent) of the 58 patients without, atrial fibrillation (p less than 0.025). Heart disease was present in 13 (43 percent) of the 30 patients with, versus 15 (26 percent) of the 58 patients without, atrial fibrillation (not significant). Inducible reentrant tachycardia or heart disease, or both, were significant). Inducible reentrant tachycardia or heart disease, or both, were present in 29 (97 percent) of the 30 patients with, versus 34 (59 percent) of the 58 patients without, atrial fibrillation (p less than 0.0005). Of 51 patients with inducible reentrant tachycardia, 23 patients with atrial fibrillation did not differ from 28 patients without this arrhythmia with respect to clinical features and atrial, sinus nodal, or anomalous pathway properties, or cycle length of induced reentrant tachycardia. Spontaneous degeneration of induced reentrant tachycardia to atrial fibrillation was observed in 6 (26 percent) of 23 patients with, versus none of 28 patients without, atrial fibrillation (p less than 0.025). In summary, patients with preexcitation and documented spontaneous paroxysmal atrial fibrillation almost always have inducible reentrant tachycardia or heart disease, or both. It is likely that in many patients with inducible reentrant tachycardia, spontaneously occurring reentrant tachycardia relates to induction of atrial fibrillation. However, it is unclear why some patients with inducible reentrant tachycardia have atrial fibrillation and others do not. In many patients with organic heart disease, atrial fibrillation could relate to hemodynamic changes.

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.

Enhanced atrioventricular nodal conduction in a patient with dual extranodal pathways

A patient was admitted to the hospital with wide complex tachycardia and a history of recurrent palpitations. Electrophysiologic studies showed evidence of dual atrioventricular (AV) accessory pathways. One proved to be an anteroseptal (possible right anterior) pathway probably capable of only unidirectional conduction. The other pathway was in the posterior septum and conducted only in the retrograde direction. The tachycardia circuit involved anterograde conduction via either the AV node-His axis or the anteroseptal pathway and retroconduction over the posteroseptal accessory pathway. In addition, enhanced AV nodal conduction coupled with two accessory AV nodal pathways has rarely been described in English medical literature. Previous reports have carefully described anatomic, electrocardiographic, and electrophysiologic evidence of more than one accessory pathway in patients with the Wolff-Parkinson-White syndrome. The introduction of surgical techniques for ablation of an accessory pathway demands precision in the electrophysiologic evaluation of patients with ventricular preexcitation. Reported herein is a patient with the unique finding of two extranodal accessory pathways and enhanced atrioventricular (AV) nodal conduction (or AV nodal bypass).

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

A 10-month-old infant with multiple muscular ventricular septal defects, congestive heart failure, Wolff-Parkinson-White syndrome, and supraventricular tachycardia is presented. The site of ventricular pre-excitation was predicted by analysis of ST-T wave isopotential body surface maps to be in the posterior free wall of the right ventricle. The site was confirmed by epicardial mapping of the ventricles during surgery. The pathyway was cryoblated and the ventricular defects were closed. The patient has been free of pre-excitation and supraventricular tachycardia for over two years since surgery.

Surgery for life-threatening ventricular tachyarrhythmias

Among 203 left ventricular aneurysmectomies performed since 1970, the operative mortality rate was 18.7 percent. In 49 patients (24 percent), left ventricular aneurysmectomy was performed for refractory life-threatening ventricular arrhythmias. Eight additional patients had coronary bypass grafting without ventricular aneurysmectomy. One of these patients had bypass grafting followed later by ventricular aneurysmectomy. All 56 patients had underlying coronary artery disease. The operative mortality rate was 19.6 percent. In patients with a recent myocardial infarction, the rate was 60 percent, whereas it was 11 percent in patients with a remote myocardial infarction. Other high risk variables in these patients included coronary bypass grafting without myocardial resection, and an elevated left ventricular end-diastolic pressure. The late mortality rate was 17.9 percent, but only one of these deaths was sudden and unexpected. The 35 long-term survivors have been followed up for a mean of 40.7 months (range 7 to 92 months). Of these, 20 remain on antiarrhythmic medications for palpitation or documented ventricular premature complexes, whereas 15 are free of detectable rhythm disturbances and do not require antiarrhythmic agents. Only 4 of 35 (11 percent) have had recurrent documented ventricular tachycardia. Left ventricular aneurysmectomy may be performed for refractory ventricular tachyarrhythmias with an acceptable operative mortality, particularly if the patient has survived longer than 6 weeks after myocardial infarction. Although epicardial mapping techniques may be useful in localizing the reentrant pathway of the ventricular tachycardia, ventricular aneurysmectomy without mapping techniques produces a satisfactory clinical result in the vast majority of long-term survivors.

Body surface potential distributions in posterior ventricular pre-excitation

Waveform of the QRS complex during ventricular pre-excitation is subject to the influence of both the site of pre-excitation and the time of pre-excitation relative to that of excitation via the normal AV path. This paper reports a case in which lead V1 of the electrocardiogram (ECG) could be altered from an R to an rS pattern by the administration of atropine sulfate. The provable mechanism was that of reduced conduction time in the normal AV path with altered time phase of normal excitation and pre-excitation. This mechanism was simulated in experiments on dogs and yielded similar findings. Body surface mapping in both the patient and the dogs provided evidence that pre-excitation could be recognized by that means with varied time phase of normal excitation and pre-excitation. It was demonstrated that the QRS complex of right sided precordial leads could be altered from an R to an rS pattern by altering the time phase of normal excitation and pre-excitation of the posterior ventricular wall. This alteration was related to the degree to which negative potentials on the anterior chest wall due to right ventricular breakthrough of normal activation developed in relation to the time of pre-excitation.

Disorders of heart rate and rhythm

The clinical approach to a child with a disorder of the heart beat is still that of a careful history, physical examination, and an ECG with a long rhythm strip. A diagnostic approach is presented which is based on rate, rhythm, and mechanism. Newer diagnostic methods are presented as well as advances in the basic cellular electrophysiology. Disorders of automaticity, triggerable cells, and re-entry are analyzed. Finally, therapy is revised for conventional drugs, and new and nonapproved drugs are listed. Indications and limitations for cardioversion, electrical pacing, and surgery are presented.