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Ripple mapping is a novel, three-dimensional, electroanatomic mapping tool that displays each electrogram at its corresponding 3-dimensional coordinate as a dynamic moving bar, which changes in length according to the electrogram voltage-time relationship. We present the case of a 43-year-old male patient with surgically repaired Ebstein's anomaly who previously underwent two unsuccessful ablation procedures for right atrial flutter (cavotricuspid isthmus and intercaval lines). Ripple mapping was decisive, enabling the arrhythmia mechanism to be appropriately recognized, and a distinction to be made between critical areas of the circuit and delayed activated bystander regions., (Copyright © 2018 Sociedade Portuguesa de Cardiologia. Publicado por Elsevier España, S.L.U. All rights reserved.)

Intra-atrial re-entrant tachycardia (IART) is a severe complication in patients with congenital heart disease (CHD). Cavotricuspid isthmus (CTI)-related IART is the most frequent mechanism. However, due to fibrosis and surgical scars, non-CTI-related IART is frequent. The main objective of this study was to describe the types of IART, circuit locations, and to analyze predictors of CTI versus non-CTI-related IART. This is an observational study that includes all consecutive patients with CHD who underwent a first IART ablation in a single referral tertiary hospital from January 2009 to December 2015 (94 patients; 39.4% women; age: 36.55 ± 14.9 years, 40.4% with highly complex cardiac disease). During the study, 114 IARTs were ablated (1.21 ± 0.41 IARTs per patient). CTI-related IART was the only arrhythmia in 51% (n = 48) of patients; non-CTI-related IART was the only mechanism in 27.7% (n = 26), and 21.3% of patients (n = 20) presented the two types of IART. Severe dilation of the systemic ventricle, absence of severe dilation of the venous atrium, highly complex cardiac defects, and nontypical electrocardiography (ECG) were related to non-CTI-related IART in univariate analysis. In multivariate analysis, nontypical ECG (odds ratio 3.64; 1.01 to 4.9; p = 0.049) and grade III CHD complexity (odds ratio 9.43; 1.44 to 11.7; p = 0.001) were predictors of non-CTI-related IART. In conclusion, in our population with a high proportion of complex CHD, CTI-related IART was the most frequent mechanism, although non-CTI-related IART was present in 49% (alone or with concomitant CTI-related IART). High-grade CHD complexity and nontypical ECG were strongly related to non-CTI IART., (Copyright © 2018 Elsevier Inc. All rights reserved.)

Background: Intra-atrial reentrant tachycardia (IART) after the Fontan operation had an early reported incidence of 10% to 35% during early and intermediate follow-up and posed substantial management challenges., Methods and Results: To reduce the incidence of IART after the Fontan procedure, we performed a randomized, double-blind study to evaluate the impact of an incision in the right atrium joining the lateral tunnel suture line and the tricuspid valve annulus. Between March 1998 and September 2003, 134 subjects (median age: 1.8 years; range: 1.3-5.2 years; 91 men) were randomly assigned to receive the incision. All 134 patients had a form of single ventricle pathological anatomy. The clinical course, electrocardiograms, and Holter monitoring were available for review in 114 subjects at a median of 8.2-year follow-up (range: 0.9-11.9 years). There were 2 late deaths, neither subject had IART. The combined incidence of sustained IART was 3.5% (4/114). There was no difference in the occurrence of sustained IART between those subjects receiving the incision and those who did not (2 in each group) during follow-up. No patients of either group experienced short-term complications., Conclusions: Despite the fact that the primary outcome of this trial was not reached, the most significant finding was that with current management, the incidence of IART is considerably lower than the early retrospective, observational studies suggested., (© 2016 American Heart Association, Inc.)

Objectives: To present and test a simple surgical technique that may prevent atrial reentrant tachycardia following surgery for congenital heart disease. This arrhythmia is one of the commonest long-term complications of such a surgery. It may occur many years (even decades) after the operation. It is usually explained as a late consequence of right atriotomy, which is an inherent component of many operations for congenital heart disease. Right atriotomy results in a long scar on the right atrial myocardium. This scar, as any scar, is a barrier to electrical conduction, and macro-reentrant circuits may form around it, causing reentrant tachycardia. However, this mechanism may be counterchecked and neutralized by our proposed method, which prevents reentrant circuits around right atriotomy scars., Methods: The proposed method is implemented after termination of cardiopulmonary bypass and tying the venous purse-strings. It consists of constructing a full-thickness suture line on the intact right atrial wall from the inferior vena cava (IVC) (a natural conduction barrier) to the atriotomy incision. This suture line is made to cross the venous cannulation sites if these are on the atrial myocardium (rather than being directly on the venae cavae). Thus, the IVC, atriotomy and cannulation sites are connected to each other in series by a full-thickness suture line on the atrial wall. If this suture line becomes a conduction barrier, it would prevent reentrant circuits around right atrial scars. This was tested in 13 adults by electroanatomical mapping. All 13 patients had previously undergone right atriotomy for atrial septal defect closure: 8 of them with the addition of the proposed preventive suture line (treatment group) and 5 without (control group)., Results: In all 13 cases, the atriotomy scar was identified as a barrier to electrical conduction with electrophysiological evidence of fibrosis (scarring). In the 8 patients with the proposed suture line, this had also become a scar and a complete conduction barrier. In the 5 patients without this suture line, there was free electrical conduction between the IVC and atriotomy scar., Conclusions: The proposed suture line becomes a scar and conduction barrier. Therefore, it would prevent reentrant circuits around atrial scars and their consequent arrhythmias., (© The Author 2015. Published by Oxford University Press on behalf of the European Association for Cardio-Thoracic Surgery. All rights reserved.)

Background: Atrial tachyarrhythmia is a major late complication in adult Fontan patients. This study examined the clinical features and risk factors of late intra-atrial reentrant tachyarrhythmia (IART) in adult patients after Fontan surgery and the mid-term outcome of Fontan conversion with or without antiarrhythmic surgery in these patients., Methods: We conducted a retrospective study on adult patients who were born before 1994 and survived at least 3 months after a Fontan operation at Seoul National University Children's Hospital., Results: We followed 160 patients over 20.9 ± 4.1 years. Sustained atrial tachycardia was identified in 51 patients, and IART was found in 41, appearing a mean 13.6 years after surgery. By the 25 year follow-up, 40% had developed IART. The incidence of IART significantly increased over time. Patients with an atriopulmonary connection (APC) (n=65) had significantly longer follow-up duration and higher incidence of IART than patients with a lateral tunnel (n=86) or extracardiac conduit Fontan (n=9). On multivariate analysis, APC, sinus node dysfunction, and nonsustained atrial tachycardia were found to be significantly associated with IART. Twenty-four patients with IART underwent Fontan conversion. Over the follow-up period, IART severity scores in the 22 patients who survived after Fontan conversion decreased significantly, and New York Heart Association functional class significantly improved. On multivariate analysis, protein losing enteropathy and ventricular dysfunction were found to be significant risk factors for mortality., Conclusions: IART was common in adult Fontan patients, and Fontan conversion with or without antiarrhythmic surgery and pacemaker placement helped to control it., (Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.)

Background & Aims: Gastric arrhythmias occur in humans and experimental animals either spontaneously or induced by drugs or diseases. However, there is no information regarding the origin or the propagation patterns of the slow waves that underlie such arrhythmias., Methods: To elucidate this, simultaneous recordings were made on the antrum and the distal corpus during tachygastrias in open abdominal anesthetized dogs using a 240 extracellular electrode assembly. After the recordings, the signals were analyzed, and the origin and path of slow wave propagations were reconstructed., Results: Several types of arrhythmias could be distinguished, including (1) premature slow waves (25% of the arrhythmias), (2) single aberrant slow waves (4%), (3) bursts (18%), (4) regular tachygastria (11%), and (5) irregular tachygastria (10%). During regular tachygastria, rapid, regular slow waves emerged from the distal antrum or the greater curvature, whereas, during irregular tachygastria, numerous variations occurred in the direction of propagation, conduction blocks, focal activity, and re-entry. In 12 cases, the arrhythmia was initiated in the recorded area. In each case, after a normal propagating slow wave, a local premature slow wave occurred in the antrum. These premature slow waves propagated in various directions, often describing a single or a double loop that re-entered several times, thereby initiating additional slow waves., Conclusions: Gastric arrhythmias resemble those in the heart and share many common features such as focal origin, re-entry, circular propagation, conduction blocks, and fibrillation-like behavior.

Background: Intra-atrial reentrant tachycardia (IART) is a common arrhythmia in adult patients with palliated congenital heart disease (CHD). Traditional treatment methods such as antiarrhythmic drugs (AADs) or radiofrequency ablation are often unsuccessful or cause side effects. These patients often require frequent cardioversion and anticoagulation. The purpose of this study is to evaluate the success of overdrive atrial pacing for the suppression of IART in CHD., Methods: Single center, investigational review board approved, retrospective review of nine patients with CHD and documented, recurrent IART. Patients served as their own historical controls for this study. Phase I was defined as the period 2 years prior to atrial pacing intervention, and Phase II was defined as > or =13 months with atrial pacing; enabled or implanted rate responsive or dynamic overdrive A pacing. During Phase II, the patients' rhythm was monitored by either symptom reporting, ECG, Holter monitoring or pacer diagnostics every 2 months., Results: Cardioversion post A pacing decreased: from 25 to 3, P < .003, patients requiring cardioversions 9 to 1, P < .001, no. AADs 18 to 7, P < .02., Conclusions: Overdrive atrial pacing, > or =70 ppm, is a viable treatment option to suppress recurrent IART. With the suppression of IART, the need for cardioversion, and AAD can be significantly reduced.

Unlabelled: Rhythm disturbances are common long after surgical repair of congenital heart disease. These arrhythmias caused by the progression of the disease itself, however, a significant proportion is a result of the presence of surgical scar. Although interventional electrophysiology procedures are complex and encounter difficulties, pharmacological therapy is often very disappointing., Aim and Methods: In the present study we aimed to describe our experience obtained between 2004 and 2006 in patients undergoing transcatheter ablation long after surgery for congenital heart disease., Results: During this period 26 patients underwent catheter ablation. The procedure was successful in 24 out of the 26 patients (92%). Three patients required redo ablations due to arrhythmia recurrences (11%). There were no major complications related to the intervention. In four patients minor complications occurred (small hematomas)., Conclusions: Our descriptive data indicate that transcatheter ablation for arrhythmias after surgery for congenital heart disease is a effective safe and more importantly curative procedure. It is associated with reasonable success rate, low complication rate, but slightly higher recurrence rate as compared to the classical electrophysiological interventions.

Introduction: The complete circuit of reentrant left atrial tachycardias (LATs) occurring after ablation for atrial fibrillation (AF) has not been well described. Identifying discrete isthmuses critical to these LATs may simplify their elimination by catheter ablation., Methods and Results: Fifteen patients (all male, 56 +/- 8 years) with 15 reentrant LATs following AF ablation underwent activation and entrainment mapping. Eleven patients (11 LATs) had a single localized site with low amplitude (0.16 +/- 0.05 mV), fractionated long duration (131 +/- 23 msec) electrograms coinciding with an isoelectric interval of 106 +/- 24 msec between flutter waves on all 12 ECG leads. Three-dimensional mapping and entrainment revealed this site to be a narrow markedly slowly conducting isthmus adjacent to ablated left (n = 8) or right (n = 3) pulmonary vein (PV) ostia, and critical to nine small diameter (15 +/- 3 mm) and two large diameter (49 +/- 2 mm) circuits. One radiofrequency (RF) application on this isthmus eliminated LAT in all 11 patients. Four patients (four LATs) with large circuits around the mitral annulus and/or PV ostia lacked isoelectric ECG intervals and slow-conducting isthmuses and required multiple RF applications across anatomically wide, rapidly conducting isthmuses., Conclusion: Focally ablatable narrow isthmuses of slow conduction are critical for the majority of reentrant LAT occurring after ablation for AF. The role and presence of these isthmuses can be anticipated by observing significant isoelectric intervals between flutter waves on all 12-surface ECG leads. Their distinctive electrophysiological characteristics allow their identification and elimination by simple RF ablation.

Computer simulation was performed to determine how reentrant activity could occur due to the spatial heterogeneity in refractoriness induced by the regional ischemia. Two regional ischemic models were developed by decreasing the intracellular ATP concentration, reducing conductance of the inward Na+ current and increasing the extracellular K+ concentration on the two-dimensional sheet. Operator splitting method was used to integrate the models. The vulnerability to reentry was estimated from the timings of premature stimuli on the constructed models, which could result in unidirectionally propagating action potentials. Two kinds of sustained spiral waves and their Pseudo-Electroscardiograms were observed in numerical simulation. The results showed that the dispersion of refractory period increased with ischemic aggravation, and led to augment of the vulnerable window. A permature stimulation within the vulnerable window could easily induce spiral reentry. The Pseudo-Electrocardiograms of the spiral waves exhibited monomorphic tachycardiac waveforms. Thus, the spatial heterogeneity in refractoriness could be a substrate for reentrant ventricular tachyarrhythmias on the regional ischemic tissue.

Sinus tachycardia, in the forms of four distinct rhythm disturbances, is frequently encountered in clinical practice but is often overlooked. The most common rhythm, normal sinus tachycardia, whether physiologic, pathologic or iatrogenic, is predominantly catecholamine driven, is virtually asymptomatic and is managed by identifying and treating the underlying cause. The other so-called primary sinus tachycardias, which include inappropriate sinus tachycardia, postural orthostatic tachycardia syndrome and sinus node re-entry tachycardia, have fundamentally different clinical features, basic underlying etiologic mechanisms and treatment strategies. Differentiation of these types from normal sinus tachycardia and from other atrial arrhythmias is crucial for successful management. Accurate diagnosis and appropriate therapy of the sinus tachycardias not only prevents multiple consultations but might also have important long-term prognostic implications.

Introduction: New methods for electrogram analysis accurately estimated reentrant circuit isthmus location and shape in a canine model. It was hypothesized that these methods also would locate reentrant circuits causing clinical ventricular tachycardia (VT)., Methods and Results: Intracardiac electrogram recordings, obtained with a noncontact mapping system, were analyzed retrospectively from 14 patients with reentrant VT who had undergone successful radiofrequency ablation for prevention of VT initiation. Unipolar electrograms from 256 uniformly distributed endocardial sites were reconstructed by mathematical transformation. Twenty-seven tachycardias were mapped; 15 (in 11 patients) had a complete endocardial reentrant circuit with a figure-of-eight conduction pattern. During sinus rhythm, the location and axis of the slowest and most uniform conduction in the region of latest endocardial activation (the primary axis), the limits of which were defined as boundaries with >15 ms difference in electrogram duration between contiguous recordings, identified the location and shape of the reentrant circuit isthmus with a mean sensitivity compared with activation mapping of 79.3% and a mean specificity of 97.6%. The midpoint of a theoretical "estimated best ablation line" drawn perpendicular to the primary axis of activation, spanning the estimated isthmus location was within 1.3 +/- 0.2 cm (mean distance +/- SD) of the actual ablation site that terminated tachycardia. Analysis of VT electrograms, based on time shifts in the far-field component of the local electrogram when cycle length changed (piecewise linear adaptive template matching [PLATM] method) in 5 of the cases, accurately estimated the time interval between activation at the recording site and the circuit isthmus slow conduction zone where the effective ablation lesion had been placed, which is proportional to the distance between the two locations (mean difference compared with activation mapping: +/-37.3 ms)., Conclusion: In selected patients with VT who have a complete endocardial circuit, isthmus location and shape can be discerned by analysis of sinus rhythm or tachycardia electrograms, and an effective ablation site can be predicted without the need to construct activation maps of reentrant circuits.

A 78-year-old man developed bradycardia with decreased level of consciousness followed by sinus arrest during femoropopliteal bypass surgery under subarachnoid anesthesia. Early in the recovery period, a similar clinical picture developed, with bradycardia but no change in level of consciousness. Sinus node automaticity or sinoatrial conduction abnormalities were suspected, and a 24-hour Holter electrocardiogram revealed bradycardia-tachycardia syndrome. The patient was prescribed amiodarone and anticoagulant therapy with acenocoumarol; no further episodes occurred during hospitalization. Bradycardia-tachycardia syndrome is a sinus node disorder that manifests intermittently. It can become apparent during or shortly after surgery, leading to problems of differential diagnosis.

Introduction: The electrophysiologic mechanism of intra-atrial reentrant tachycardia (IART) is generally thought to be a macroreentrant circuit revolving around a nonconductive or highly anisotropic barrier. However, the electrical and anatomic substrate that supports these circuits has been incompletely defined. Our objectives were to characterize the atria of patients with IART using electroanatomic mapping in sinus or atrially paced rhythm and to determine whether electrical barriers identified in sinus/atrially paced rhythm are associated with IART circuits., Methods and Results: Eighteen patients with IART and a remote history of repaired or palliated congenital heart disease were studied [8 biventricular repair, 8 single ventricle palliation (7 Fontan), and 2 Mustard repair]. Thirteen patients had a right AV valve. In sinus/atrially paced rhythm, electrical evidence of a crista terminalis was identified in 11 patients, an atriotomy in 12, and > or = 1 right atrial free-wall scar in 11. In 26 IART circuits characterized, 12 used the right AV valve as a central obstacle, 6 used a right atrial free-wall scar, 3 used an atriotomy, 3 used the crista terminalis, and 2 circuits used an atrial septal scar. All central obstacles used by IART circuits were identified in sinus/atrially paced rhythm., Conclusion: The crista terminalis, atriotomy, and right atrial scars can be identified in patients with repaired congenital heart disease by electroanatomic mapping in sinus/atrially paced rhythm. These conduction barriers frequently function as the central obstacle for IART. Demonstration of such features may help focus investigational mapping without reliance on spontaneous initiation of the tachycardia.

Unlabelled: Occurrence of supraventricular tachycardia and sinus node dysfunction was investigated pre- and postoperatively by serial ECG and Holter monitors in 63 consecutive patients with univentricular circulation after modified Fontan operation (total cavopulmonary connection 39 patients, atriopulmonary connection 24 patients). Mean age at operation was 7.2 (0.1-20.3) years. Of the 63 patients, 14 (22%) had early (< 14 d) supraventricular tachycardia or sinus node dysfunction, which was not related to the type of operation. None of 9 patients with a preoperative mean right atrial pressure < or = 2.5 mm Hg had early supraventricular tachycardia or sinus node dysfunction in contrast to 16/54 patients (30%) with a preoperative mean right atrial pressure > 2.5 mm Hg. 6/63 patients died during the early (< 14 d) postoperative period. In only 1 child, death was related to a dysrhythmia (junctional ectopic tachycardia). During a mean follow-up of 2.5 years, 15/57 long-term survivors (21%) had late supraventricular tachycardia or sinus node dysfunction. Early supraventricular tachycardia/sinus node dysfunction was a predictor or late atrial dysrhythmias, as it occurred in 8 of the surviving 14 patients with early dysrhythmias in contrast to 4 children without early atrial dysrhythmias (p < or = 0.001). After creation of an atriopulmonary connection, 10/22 patients (45%) had late supraventricular tachycardia/sinus node dysfunction, but only 2/35 patients (6%) with a total cavopulmonary connection had late atrial dysrhythmias (p < 0.001)., Conclusions: Early atrial dysrhythmias after the Fontan operation were related to preoperative hemodynamics. Early supraventricular tachycardia/sinus node dysfunction and the atriopulmonary type of Fontan connection were significant risk factors for late atrial dysrhythmias.

An analysis was made in 14 isolated and perfused rabbit hearts of the electrophysiological effects of selective radiofrequency (RF) delivery in the anterior (group I, n = 7) or posterior zone (group II, n = 7) of the Koch triangle, with the aim of modifying atrioventricular nodal (AVN) conduction without suppressing 1:1 transmission. After opening the right atrium, RF was delivered (0.5 W) with a 1-mm diameter unipolar electrode positioned in the selected zone until a prolongation of no less than 15% was obtained in the Wenckebach cycle length (WCL). Before and after (30 min) RF, anterograde and retrograde AVN refractoriness and conduction were evaluated, stimulating from the crista terminalis (CT), the interatrial septum (IAS), and from the RV epicardium. After RF, the following percentage increments were observed in group I: AH(CT) = 36% +/- 9%, AH(IAS) = 38% +/- 11%, WCL(CT) = 28% +/- 8%, WCL(IAS) = 22% +/- 6%, functional refractory period (FRP) of the AVN(CT) = 13% +/- 11%, FRP-AVN(IAS) = 13% +/- 8%, retrograde WCL = 20% +/- 19%, and retrograde FRPVA = 13% +/- 16%. The increments observed in group II and the significances of the differences with respect to group I were: AH(CT) = 11% +/- 14% (P < 0.01), AH(IAS) = 19% +/- 32% (NS), WCL(CT) = 42% +/- 14% (P < 0.05), WCL(IAS) = 42% +/- 16% (P < 0.01), FRP-AVN(CT) = 28% +/- 28% (NS), FRP-AVN(LAS) = 21% +/- 19% (NS), retrograde WCL = 35% +/- 24% (NS), and retrograde FRP = 16% +/- 13% (NS). In both groups, the AH interval variations were not correlated with those of the rest of the parameters analyzed. Truncated nodal function curves suggestive of a dual AV nodal pathway were obtained in three experiments, though in only one of them was this observed under basal conditions. In the other two experiments, with dual AV nodal physiology only after RF (one from each group), AV nodal reentrant tachycardias were triggered with atrial extrastimulus at coupling intervals equal to or shorter than at those that cause a sudden lengthening of the AH interval, RF delivered in the anterior and posterior zones of the Koch triangle produced effects of different magnitude on the AH interval and Wenckebach cycle length. In the anterior zone the AH interval was prolonged to a greater extent, while in the posterior zone the effects were greater on the Wenckebach cycle length. No correlation existed between the variations in AH interval and Wenckebach cycle length, regardless of where RF was delivered. The evaluation of anterograde AV nodal refractoriness was similar when stimulating from the crista terminalis or from the interatrial septum. By delivering RF, it was possible to induce dual AV nodal physiology and reentrant tachycardias.

A 22-year-old woman with an atrial septal defect surgically corrected during childhood presented with a wide QRS complex tachycardia with left bundle branch block morphology. Electrophysiological study was performed and bundle branch reentrant tachycardia was induced with morphology identical to clinical tachycardia. Radiofrequency catheter ablation of the right bundle branch was successful, resulting in complete right bundle branch block and cure of her ventricular arrhythmia.

Transesophageal, electrophysiologic studies were conducted in 47 patients, with clinical and ECGgraphic diagnosis of paroxysmal reciprocating supraventricular tachycardia. After admission to hospital, the patients were enrolled in the study in accordance with the criterion concerning the exclusion of patients with signs and symptoms of severe heart pump failure (ie, NYHA III and IV class were excluded). The transesophageal study was performed during paroxysmal tachycardia in each patient to measure the V-A interval and to localize the site of reentry. Thereby, the patients could be grouped into 2 subsets, ie those with A-V nodal reentrant tachycardia (no. 30 patients) and those with accessory pathway reentrant tachycardia (no. 17 patients). Moreover, the prevalence in both subsets was evaluated in the following signs and symptoms: palpitations, dyspnoea, chest pain, pulsations in the neck, significant increase in urinary output, hypotension, dizziness, near-syncope, syncope, shock, focal brain injury. From the data analysis, significantly greater prevalence of palpitations in the neck resulted in the subset of patients with reentry confined to the A-V node (no. 20 cases) compared with those suffering from reentry via accessory pathway (no. 4 cases). Moreover the arterial pressure, in A-V nodal reentrant tachycardia, showed the lowest values and the best decreases, together with the finding of a more rapid trend to decline in comparison with the accessory pathway subset. On the other hand, no significant differences could be seen about the remaining symptoms. In an attempt to provide the reliable explanation for the differences found between the 2 subsets of study, concerning both the unpleasant pulsations in the neck and the pressure decrease, we postulated a remarkable role for the length of arrhythmic circle movement. The smaller dimensions of circuit limbs, in A-V nodal reentrant tachycardia, are likely to be the principle cause of the different clinical features of 2 types of reentry. We speculate actually that in susceptible patients the critical event is most likely to be A-V functional dissociation due to early and unphysiologic activation of atria by stimulus rapidly reentrant from the bottom portion of the AV node: the simultaneous occurrence, frequent in A-V node reentry, of both, atrial and ventricular mechanical activation, would result, however, in impairment of atrial haemodynamics due to development of cannon A waves, able either to activate a vasodepressor reflex from the atria or to stimulate instantaneous release of atrial natriuretic factor in the circulation. Further studies, however, are necessary to be performed on large cases-records, to confirm our hypothesis.(ABSTRACT TRUNCATED AT 400 WORDS)

As many as 33 children with different patterns of tachyarrhythmia were subjected to transesophageal pacing of the left atrium. Thi incidence of the orthodromal pattern of reciprocal AV-tachycardia was the highest (10 patients); antidromal reciprocal AV-tachycardia was only noted in 1 patient. Four patients turned out to have latent Kent's bundle which provoked the development of tachycardia attacks. The slow-fast pattern was revealed in both cases of nodal tachycardia. Among atrial tachycardias, monofocal automatic one was encountered most frequently (9 patients) and only one patient was diagnosed to suffer from reciprocal atrial tachycardia. The determination of the pathogenesis of tachycardia in children with the WPW syndrome is of importance for solving the problem of the successive medicamentous and non-pharmacological treatment character.

Multielectrode mapping of stimulus propagation was used to investigate arrhythmias, developing in atrial preparations of frogs after vagal stimulation. Vagal stimulation produced attacks of tachycardia (one to several dozens extra-excitations) in 10 of 16 specimens. In such cases, mapping demonstrated re-entry of the excitation wave that appeared where the front of the next excitation wave from the sinus went along the border of temporarily-unexcitable area during the recovery of excitability in vagus-inhibited atrial areas. The emergence of re-entry was possible, because the excitation wave length (lambda), was shortened owing to reduced refraction and speed of conduction under vagal effect. After myocardial tissue got rid of vagal influence, lambda increased, after which re-entry was no longer possible, and arrhythmia discontinued.