Area Of Preexcitation Research Articles

Cardiac Memory in Patients With Wolff-Parkinson-White Syndrome

Background— Cardiac memory refers to a change in ventricular repolarization induced by and persisting for minutes to months after cessation of a period of altered ventricular activation (eg, resulting from pacing or preexcitation in patients with Wolff-Parkinson-White syndrome). ECG imaging (ECGI) is a novel imaging modality for noninvasive electroanatomic mapping of epicardial activation and repolarization. Methods and Results— Fourteen pediatric patients with Wolff-Parkinson-White syndrome and no other congenital disease, were imaged with ECGI a day before and 45 minutes, 1 week, and 1 month after successful catheter ablation. ECGI determined that preexcitation sites were consistent with sites of successful ablation in all cases to within a 1-hour arc of each atrioventricular annulus. In the preexcited rhythm, activation-recovery interval (ARI) was the longest (349±6 ms) in the area of preexcitation leading to high average base-to-apex ARI dispersion of 95±9 ms (normal is ≈40 ms). The ARI dispersion remained the same 45 minutes after ablation, although the activation sequence was restored to normal. ARI dispersion was still high (79±9 ms) 1 week later and returned to normal (45±6 ms) 1 month after ablation. Conclusions— The study demonstrates that ECGI can noninvasively localize ventricular insertion sites of accessory pathways to guide ablation and evaluate its outcome in pediatric patients with Wolff-Parkinson-White syndrome. Wolff-Parkinson-White is associated with high ARI dispersion in the preexcited rhythm that persists after ablation and gradually returns to normal over a period of 1 month, demonstrating the presence of cardiac memory. The 1-month time course is consistent with transcriptional reprogramming and remodeling of ion channels.

Body-surface distribution of changes in activation-recovery intervals before and after catheter ablation in patients with Wolff-Parkinson-White syndrome: clinical evidence for ventricular 'electrical remodeling' with prolongation of action-potential duration over a preexcited area.

T-wave abnormalities after catheter ablation in patients with manifest Wolff-Parkinson-White (WPW) syndrome have been attributed to a continuation of repolarization abnormalities induced by preexcitation (cardiac memory). To clarify changes in repolarization properties, we analyzed the activation-recovery interval (ARI) obtained from body-surface maps and the relationship between the activation time (AT) and ARI in 30 patients with WPW syndrome (group A, 18 patients with manifest left-sided accessory pathway; group B, 7 patients with manifest right-sided accessory pathway; and group C, 5 patients with concealed left-sided accessory pathway) before, 1 day after, and 1 week after ablation. The ARI significantly decreased 1 week after ablation compared with before and 1 day after ablation over the preexcited area in groups A and B. Correlation coefficients between the AT and ARI showed a significantly (P<.01) stronger inverse relationship before (r=-.58) and 1 week after (r=-.64) ablation than 1 day after ablation (r=-.46) in groups A and B. In group C, the ARI and correlation coefficients between the AT and ARI showed no significant changes. These findings suggest a prolongation of the action-potential duration over the preexcited area before and just after ablation as ventricular "electrical remodeling," a decrease in the inverse relationship between the AT and action-potential duration 1 day after ablation, and a gradual recovery of the action-potential duration over the preexcited area and inverse relationship 1 week after ablation.

Successful treatment of Wolff-Parkinson-White syndrome with concomitant mitral stenosis by simultaneous surgery

We report the case of a 61-year-old man with type B Wolff-Parkinson-White (WPW) syndrome associated with a right atrioventricular (AV) accessory pathway and concomitant mitral stenosis, who underwent successful operative treatment by simultaneous surgery. His preoperative course had been characterized by cardiac failure and repeated episodes of atrial tachyarrhythmia, in the form of fibrillation and flutter, which were difficult to control by conventional medication. Preoperative electrocardiograms (ECGs) had suggested that the accessory pathway was located in the right posterior to posteroseptal wall; however, at the time of surgery, epicardial electrophysiological mapping with sock electrodes revealed a preexcitation area in the AV groove at the lateral right margin of the heart. This discrepancy was thought to have been due to the presence of mitral stenosis or multiple accessory pathways. Thus, division and cryoablation of the accessory pathway by an endocardial approach, in addition to mitral valve replacement, were performed under cardiopulmonary bypass. His postoperative course was uneventful, and subsequent ECGs revealed that the delta waves had disappeared. The successful outcome of this patient demonstrates the effectiveness of simultaneous surgery for WPW syndrome associated with valvular disease.

Clinical magnetocardiography

Since the introduction, in 1982, of a Biomagnetic facility in the clinical environment, efforts were concentrated to investigate whether magnetocardiography could really provide new information of potential diagnostic use, even avoiding electromagnetic shielding to facilitate simultaneous biomagnetic and conventional cardiac investigations, including cardiac catheterization for invasive electrophysiological procedures. More than 350 patients have been magnetically investigated using a single-channel second-order gradiometer. Results of 281 MCG studies, whose data have been extensively analyzed with updated software programs, are reported. Magnetocardiographic (MCG) mapping during endocardial pacing was performed to quantify the accuracy of MCG localization of intracardiac dipolar sources. MCG classification of ventricular preexcitation has been attempted in 70 patients with overt preexcitation. MCG localization of the ventricular preexcited area was accurate and reproducible, provided that during mapping a sufficient degree of ventricular preexcitation was present. MCG mapping during orthodromic A-V re-entry tachycardia has been also employed to attempt the localization of retrograde atrial preexcitation as well as the site of origin of atrial and ventricular tachyarrhythmias. For validation, the results of catheter and epicardial mappings have been used. Other applications of clinical magnetocardiography are under evaluation. The use of the Relative smoothness index needs, in our opinion, a larger experience to define its reliability as a predictor of risk for sudden death. MCG follow-up study of patients with transplanted hearts seems to be a promising application, for early detection of acute graft rejection reaction. Our reported case strongly supports this potentiality. Present work is also addressed to develop an integrated system allowing easy MCG mapping during cardiac catheterization, as a new method to guide diagnostic and therapeutic procedures as close as possible to the arrhythmogenic substrate.

On the accuracy of source localisation in cardiac measurements (magnetocardiography)

Describes a localisation study of the sources of bioelectrical activity in the human heart. In particular, the atrial activation (P wave) and the activation of an extra pre-excitation area in the Wolff-Parkinson-White syndrome are investigated. Different models based on the current multipole expansion are used to calculate the inverse solution. A comparison between calculated results, invasive electrophysiological studies and known physiological data is performed. The best results were obtained by the current multipole model with dipole and quadrupole terms. Non-invasive localisation of cardiac electric sources can be useful in studies of arrhythmia patients in the future.

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.

Effect of tiapamil in the preexcitation syndrome.

The effects of tiapamil were studied in 10 patients with antegrade preexcitation using programmed stimulation of the heart. Before administration of the drug, it was possible to initiate sustained orthodromic tachycardia in 7 patients, antidromic tachycardia in 2 and atrial echoes in 1 case by premature atrial and/or ventricular stimulation. An intravenous bolus of 2 mg/kg tiapamil terminated the tachycardia in 7 out of 8 cases by blocking the A-V node. The tachycardia continued at a reduced heart rate in 1 case with a nodoventricular bypass. Tiapamil lengthened the effective A-V nodal refractory period in 1 patient in whom it could be measured and the atrial effective refractory period in 1 case but did not prolong the antegrade or retrograde refractory periods of the accessory pathway. Only in 1 case was the antegrade effective refractory period of the accessory pathway shortened by tiapamil. The A-V nodal conduction time (A-H interval) was prolonged. Following tiapamil it was not possible to initiate the tachycardia in 4 cases and atrial echoes in 1 case; in 2 patients the tachycardia zone widened and in 3 it was not altered. In the latter, the cycle length of the tachycardia increased. Tiapamil appears to be of therapeutic value for the termination of tachycardia and also for its prevention in some cases. In others, it may facilitate the initiation of tachycardia. The delayed A-V nodal conduction during sinus rhythm augments the area of ventricular preexcitation which may facilitate the electrocardiographic localization of the accessory pathway.

Effect of tiapamil in the Wolff-Parkinson-White syndrome.

The effect of tiapamil was studied in 9 patients with the Wolff-Parkinson-White syndrome using programmed stimulation of the heart. Before the drug, sustained orthodromic tachycardias could be initiated in 7 patients and antidromic tachycardia in 2 by premature atrial and/or ventricular stimulation. An intravenous bolus of tiapamil, 2 mg/kg, terminated the tachycardia in 7 out of 8 cases by a block in the atrioventricular (AV) node. Tiapamil lengthened the effective refractory period of the AV node in the only patient in whom it could be measured and the atrial effective refractory period in 1 out of 9 cases, but the drug had no influence on antegrade or retrograde refractory periods of the accessory pathway or on that of the ventricle. The AV nodal conduction time (A-H interval) was prolonged. Following tiapamil, it was not possible to initiate the tachycardia in 4 cases, in 2 patients the tachycardia zone widened, and in 3 it was unaltered. In the latter cases, the cycle length of the tachycardia was increased. Tiapamil appears to be useful for the termination of tachycardia and also for its prevention in some cases. In others, it may facilitate the inhibition of tachycardia. The delayed AV nodal conduction during sinus rhythm augments the area of ventricular preexcitation, which may facilitate the electrocardiographic localization of the accessory pathway.

Experimental and clinical study of the pre-excitation syndrome.

Ventricular pre-excitation was experimentally produced in mongrel dogs. Their ECG and epicardial maps were analyzed. Forty-two cases of W-P-W syndrome were operated on between 1969 and May, 1980. The relationship between ECG, particularly the delta wave and localization and meaning of pre-operative examinations such as vectorcardiography, echocardiography, body surface mapping, intracavitary potential study, and cardiac pacing, were presented and discussed. As an intraoperative study, epicardial mapping was indispensable and was the most accurate method in determining the ACP. Endocardial potential study was another meaningful method in certain cases. Detachment of the atrium from the ventricle with an incision along the annulus and at the opposite of the pre-excitation area resulted in complete correction in 32 out of 34 cases between 1973 and May, 1980. Six cases of multiple ACPs were also corrected, although 4 needed a second operation. Indications for surgery of the W-P-W syndrome should be extended further in view of the high success and safety rate of the surgery.

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

We operated upon 36 patients with Wolff-Parkinson-White (WPW) syndrome between 1969 and July, 1979. The relationship between the electrocardiogram (ECG), particularly the delta wave, and localization of the accessory conduction pathway (ACP) was analyzed, and the value of preoperative examinations such as vectorcardiography, echocardiography, body surface mapping, intracavitary potential study, and cardiac pacing were demonstrated. Epicardial mapping was indispensable as an intraoperative study and represented the most effective method for localizing the ACP. In some cases, endocarial potential study was found to be efficacious. Detachment of the atrium from the ventricle by an incision along the anulus at the area of earliest pre-excitation, resulted in complete correction in 26 of 28 patients operated upon between 1973 and July, 1979. In five patients multiple ACPs was corrected, although four of them required a second operation. The surgical indications in the WPW syndrome should be expanded in view of the high success rate and the safety of the operation.

Body-surface maps of heart potentials: tentative localization of pre-excited areas in forty-two Wolff-Parkinson-White patients.

Heart potentials were recorded from the entire chest surface in 42 patients suffering from Wolff-Parkinson-White syndrome. We were able to identify six types of surface maps, according to the location of the potential maximum and minimum during the delta wave. For each of these types we suggested the most likely location of the pre-excited region around the A-V rings (types 1 to 5) or in the interventricular septum (type 6). In 13 patients belonging to Types 1, 2, 3, 5 and 6 our hypotheses were in agreement with intracardiac recordings, epicardial maps or surgical results obtained by others. Isopotential surface maps provide more information on the location of the pre-excited area than conventional ECGs, particularly when these exhibit intermediate features between Types A and B.

Body surface isopotential mapping in Wolff-Parkinson-White syndrome: Noninvasive method to determine the localization of the accessory atrioventricular pathway

The body surface isopotential maps of 22 patients with WPW syndrome were obtained from the 85 unipolar lead ECG's using the on-line minicomputer system newly devised by the author's group. The map patterns were classified into three types—I, II, and III (Type I, eight; Type II, seven; Type III, three; and unclassified, four cases). In Type I, the back surface displayed the negative potential throughout the entire ventricular activation, and at the terminal stage the lower precordial area displayed the positive potential and the upper precordial area, the negative one. Type II was characterized by two longitudinal lines, one staying at its place on the back and the other moving right to left on the precordial area following the process of ventricular activation. In Type III, the right precordial area displayed negative potential in the early stage, and in the terminal stage the upper part of the right side of chest surface displayed positive potential and the lower part, negative potential. It was surmised from these patterns that the pre-excited area was located at the posterior region of the ventricles in Type I, at the right ventricle in Type II, and the right ventricular base near the posterior margin of the ventricular septum in Type III. Type A patients in the conventional ECG classification fell under Type I; Type C patients, under Type III; Type B patients under either Type I or Type II.

Arrival of excitation at the right ventricular apical endocardium in Wolff-Parkinson-White syndrome type B.

His bundle and bipolar right ventricular apex (RVA) and right ventricular outflow tract (RVOT) catheter electrograms taken from sites 1 mm apart were recorded simultaneously with various surface leads in two patients with Wolff-Parkinson-White syndrome (WPW) type B. In "fusion" beats the presence of a normal H-RVA interval indicated that the apex of the right ventricle was activated by the impulse emerging from the right branch. On the other hand, a shorter-than-normal H-RVA interval implied that the RVA was depolarized by the activation front propagating from the pre-excited site. When this occurred, the V-RVA intervals gave a rough estimate of conduction time from pre-excited area to RVA. The values obtained (40 and 50 msec, respectively) were shorter than in two other patients with WPW type A. The arrival of excitation patterns in the right ventricular endocardium were similar in WPW type B and in beats produced by RVA stimulation but differed markedly from that of left anterior hemiblock even when the surface electrocardiographic leads showed abnormal left axis deviation in all instances. This resemblance between ventricular complexes attributed to WPW type B and those resulting from stimulation of an inferior (apical) site suggests, but does not prove, that the impulses propagated from an equivalent region of the right ventricle. These simultaneously recorded His bundle and right ventricular endocardial electrograms during electrical stimulation of the heart have increased our knowledge of Wolff-Parkinson-White syndrome.

Attempted surgical division of the preexcitation pathway in the Wolff-Parkinson-White syndrome

In a patient with type B Wolff-Parkinson-White syndrome, epicardial activation sequence mapping was carried out at the time of surgery for concurrent mitral stenosis. The patient's preoperative course had been characterized by cardiac failure and repeated episodes of atrial tachyarrhythmia (fibrillation and flutter) which were difficult to control by conventional medical therapy. The mapping procedure revealed a broad area of preexcitation in the atrioventricular groove at the lateral right margin of the heart. Preexcitation was not present at the moment of incision, and attempted surgical interruption of the preexcitation pathway was unsuccessful. After surgery, there was a reduced incidence of tachyarrhythmia, but electrocardiographic evidence of preexcitation existed. Possible reasons for failure to sever the preexcitation pathway are considered.

The electrocardiogram in patients with pacemakers

A study of the pacemaker-induced ventricular complexes can be of help in determining the site of stimulation. The first step consists in separating the stimulus artefacts from the QRS complexes. Right ventricular pacing usually produces a complete left bundle branch block (CLBBB) morphology. The electrical axis can be left, normal or even right, as pacing is performed from the apex to the outflow tract. Rarely an S1-S2-S3 pattern (with negative deflection in V1 and V2) appears during right ventricular apical pacing. Left ventricular stimulation usually produces a right bundle branch block pattern with inferior and rightwards deviation of the AQRS, although a superior axis is rarely seen with inferior stimulation. In the absence of pacer failure the basic QRS morphology produced by late diastolic stimuli can change if: (a) there are significant respiratory movements; (b) stimulation occurs during the relative refractory period; and (c) fusion beats occur. The classical Wolff-Parkinson-White beat was interpreted as a fusion beat, as long as exclusive Kent bundle conduction was not present. In the latter instances pacing from the preexcited area appeared to have produced similar QRS complexes.

Evidence for propagation of activation across an accessory atrioventricular connection in types A and B pre-excitation.

The sequence of atrioventricular activation was studied in two human subjects with type B Wolff-Parkinson-White syndrome (WPW) and in a dog with spontaneous type A WPW. In all three subjects a focal spot of pre-excitation was demonstrated at the A-V margin of the right ventricle (RV). In the two human subjects with type B WPW, the area of pre-excitation was located on the anterior aspect of the RV and in the dog with type A the pre-excited area was located on the posterior aspect of the RV. A probable Kent bundle electrogram was recorded from the A-V margin in one of the human patients. Serial sections (7 µ) of a block taken from the region of pre-excitation in the dog revealed an anomalous A-V communication (Kent bundle). Propagation velocity across this pathway was estimated to be 0.3 mm/msec. Electrophysiologic data recorded from one of the human subjects at the onset and during an episode of supraventricular tachycardia demonstrated an atrioventricular-atrial sequence of excitation. The mechanism of initiation of the tachycardia was a ventriculo-atrial echo following a premature atrial contraction blocked in the anomalous pathway. Surgical separation of right atrium and RV at the site of pre-excitation normalized the activation and ECG and abolished the tachycardia in both patients. Ventricular fibrillation occurred repeatedly in the dog as a direct result of the rapid ventricular rate permitted by the Kent bundle subsequent to induced atrial fibrillation. Correlation of the activation sequence with the body surface potentials suggests an updated conceptual model for electrocardiographic typing of WPW. In a third patient, who demonstrated an atypical form of WPW, the region of pre-excitation could not be precisely defined and interruption of an accessory pathway was unsuccessful.

Location of the pre-excitation areas in the Wolff-Parkinson-White syndrome∗

Two cases are described in which right bundle branch block coexisted with type A and type B Wolff-Parkinson-White syndrome, respectively. The type B WPW syndrome made the right bundle branch block pattern normal, whereas type A did not. This indicates that the preexcitation area for type B is situated in the right ventricle and that for type A in the left ventricle.

The role of the right and left ventricles in the ventricular pre-excitation (WPW) syndrome: An experimental study in man

In three patients with Wolff-Parkinson-White syndrome, right bundle branch block was induced during right cardiac catheterization. Electrocardiograms and vectorcardiograms were obtained before and after the production of right bundle branch block. In cases with WPW type A it was possible to obtain simultaneous features of pre-excitation syndrome and an advanced degree of right bundle branch block in the electrocardiogram and vectorcardiogram. This suggests that the muscular segment prematurely activated is located in the left ventricle and that the right bundle branch block delays the right ventricular activation. Right bundle branch block did not modify the end of the ventricular activation in the case with WPW type B. It is postulated that in this type of WPW syndrome the pre-excitation takes place in the right ventricle, and therefore depolarization of this ventricle is mainly dependent on the pre-excitation phenomenon. The different topographic situations of the pre-excitation area, as has been shown by the experimental production of right bundle branch block, are in agreement with the characteristic features of the two varieties of WPW syndrome.

Vectorial interpretation of the ventricular complex in Wolff-Parkinson-White syndrome

A vectorial analysis of twenty-seven electro-cardiograms showing the Wolff-Parkinson-White syndrome found among 31,822 (0.085 per cent) tracings was made. By taking into consideration the delta wave vector orientation (SÂΔ) the cases were classified in two types: 1. WPW syndrome, type I, showing positive delta waves in lead V 2 (SÂΔ with a forward orientation) with SÂQRS pointing either forward or backward: and 2. WPW syndrome, type II, characterized by a negative pre-excitation component in lead V 2 (SÂΔ oriented backward). Based upon previously published experimental studies and considering the spatial orientation of the SÂΔ, we believe that the area of pre-excitation is probably located at the posterior septal and ventricular regions in the WPW syndrome, type I and at the right and anterior sites of the interventricular septum and right ventricle in cases of the WPW syndrome, type II. The average of the spatial angle between SÂQRS and SÂΔ showed a small magnitude (34.7 degrees), with a minimum angle of 10 degrees and a maximum angle of 90 degrees. This finding suggests that the electrical forces developed during the premature excitation may influence the orientation of the total ventricular activation. Five of six patients showing the WPW syndrome, type I, with large S waves in leads V 1 and V 2, were associated with left ventricular hypertrophy. Nine of eleven patients presenting positive T waves not opposed to the ventricular complexes in the left precordial leads had normal hearts; but all patients whose electrocardiograms showed negative T waves in leads V 6 and V 7 presented cardiopathies with left ventricular overloading. Finally, we call attention to the possibility of having the WPW syndrome with Q waves in leads V 6 and V 7 related to a particular orientation of SÂΔ.