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The therapy of ventricular preexcitation-induced dilated cardiomyopathy in very small infants or infants with a high risk of ablation is tough and related articles are rare. Effective pharmacotherapy to suppress ventricular preexcitation is valuable.AimsTo evaluate the effectiveness and safety of pharmacotherapy for cardiac resynchronization in infants with ventricular preexcitation-induced dilated cardiomyopathy.Methods and resultsThree infants with ventricular preexcitation-induced dilated cardiomyopathy, due to the disappearance of ventricular preexcitation during the placement of catheter, intermittent WPW pattern, and right mid septal accessory pathway respectively, had received pharmacotherapy for cardiac resynchronization. The initial dosage of oral amiodarone was 5 mg/kg.d and it was followed by the maintenance dosage of 2–2.5 mg/kg.d 4 weeks later. Propafenone (15 mg/kg.d) served as a supplement since amiodarone was not adequate in case 3. The three infants achieved successful pharmacologic suppression of ventricular preexcitation 10, 6.5, and 4.5 weeks after the initiation of amiodarone respectively. They all got normalized contraction of interventricular septum and LVEF as well as reduced LVEDD gradually after the disappearance of ventricular preexcitation. No side effects associated with pharmacotherapy happened during the follow-up. Amiodarone had been withdrawn for 2 years and 5 months in Cases 1 and 2. They both remained free from ventricular preexcitation and retained normal LVEF and LVEDD.ConclusionsPharmacotherapy for cardiac resynchronization with oral amiodarone or in combination with propafenone for infants with ventricular preexcitation-induced dilated cardiomyopathy is effective and safe. Pharmacotherapy for cardiac resynchronization served as another therapeutic choice besides ablation.

Since the beginning of the 21st century, Stanley Kent described for the first time in the literature the presence of connections between the right atrium and the right ventricle (Kent, 1893). Following this study, these connections are called atrio-ventricular accessory pathways, later also described in dogs (Hill and Tilley 1985, Thomas et al. 2006, Santilli et al. 2006, Wright et al. 2018). Accessory pathways are abnormal muscle bundles that connect the right atrium to the right ventricle, outside the usual conduction system through the atrioventricular node–His bundle–Purikinje network (Willis R., 2018). Subaortic obstruction, also called subaortic stenosis, is characterized by the abnormal presence of tissue of endocardial origin at the subvalvular level, of the left semilunar valves, causing obstruction of the ejection tract of the left ventricle. This congenital anomaly occurs more frequently in dogs, males being more prone to this pathology than females (De Madron E., 2016). [ABSTRACT FROM AUTHOR]

BackgroundAtrioventricular accessory pathways (APs) in dogs have been reported rarely. Data regarding clinical presentation and long-term outcome after radiofrequency catheter ablation (RFCA) are limited.Hypothesis/objectivesTo study clinical features, electrophysiologic characteristics, and outcome of RFCA in dogs with APs.AnimalsEighty-nine dogs presented consecutively for RFCA of APs.MethodsCase series.ResultsLabrador retrievers (47.2% of dogs) and male dogs (67.4% of dogs) were most commonly affected. Labrador retrievers were more likely to be male than non-Labrador breeds (P = .043). Clinical signs were nonspecific and most commonly included lethargy and gastrointestinal signs. Concealed APs were more prevalent in Labrador retrievers than other breeds (P = .001). Right-sided APs (91.7%) predominated over left-sided (8.3%). Tachycardia-induced cardiomyopathy (TICM) occurred in 46.1% of dogs, with complete resolution or substantial improvement noted on one-month postablation echocardiograms. Radiofrequency catheter ablation successfully eliminated AP conduction long term in 98.8% of dogs in which it was performed. Complications occurred in 5/89 dogs. Recurrence in 3 dogs was eliminated long term with a second procedure.Clinical importance/conclusionsAccessory pathways are challenging to recognize in dogs because of nonspecific clinical signs, frequency of concealed APs that show no evidence of their presence during sinus rhythm, and intermittent occurrence of tachyarrhythmias resulting from APs. Tachycardia-induced cardiomyopathy commonly occurs with AP-mediated tachycardias and should be considered in any dog presenting with a dilated cardiomyopathic phenotype because of its good long-term prognosis with rhythm control. Radiofrequency catheter ablation is a highly effective method for eliminating AP conduction and providing long-term resolution.

Bigeminy is a cardiac arrhythmia in which there is a single ectopic beat, or irregular heartbeat, following each regular heartbeat. This case demonstrates the diagnostic challenges that can be encountered while interpreting ECGs of patients with "apparent ventricular bigeminy'. [ABSTRACT FROM AUTHOR]

In this article, we present a case of a patient with a late diagnosis of Fabry disease caused by a pathogenic variant in the GLA gene (p.1287_1288dup), who repeatedly attempted interventional treatment of Wolff-Parkinson-White Syndrome due to characteristic electrocardiographic pattern of ventricular preexcitation and paroxysmal arrhythmias. The proposed pathognomonic signs of the disease will ensure timely diagnosis and the appointment of specific treatment.

We present a case of a young boy who developed persistent tachycardia despite fluid resuscitation, antipyretics, and analgesia after a Fontan procedure. Review of telemetry and ECGs revealed repolarization abnormalities, including the appearance of T-wave alternans, for which an uncommon cause was ultimately identified. [ABSTRACT FROM AUTHOR]

The coexistence of ventricular preexcitation and Brugada syndromes is very rare, no relationship has been established between them and so far they are considered separate diseases. Both are arrhythmogenic, can cause sudden death and their treatment is difficult; since some drugs used to prevent tachycardia can cause a Brugada sign. We present two patients with common characteristics: absence of structural heart disease demonstrable by conventional methods, frequent and symptomatic orthodromic tachycardias, ventricular pre-excitation and Brugada sign (both evident and intermittent), without clinical malignant ventricular arrhythmias; which is why programmed electrical stimulation was not performed to try to provoke them. Some singularities are discussed, such as the association of intranodal and orthodromic reentrant tachycardias in the patient in whom accessory pathway ablation was performed, and the difficulty of the therapeutic approach in the patient who did not agree to undergo the procedure. [ABSTRACT FROM AUTHOR]

A 30-year-old man with an ECG demonstrating ventricular preexcitation with a normal PR interval and a QR pattern in lead V1 was evaluated. Electrophysiology studies showed a normal AH interval and a shortened HV interval at sinus rhythm; while the degree of preexcitation (QRS waveform) and HV interval were not affected by multisite or incremental atrial pacing. These findings implied ventricular preexcitation due to a fasciculoventricular pathway (FVP). Moreover, temporarily blocking FVP conduction mechanically resulted in normal HV interval, absence of delta wave, and an rSR pattern in V1, which indicated incomplete right bundle branch block (IRBBB). These findings suggested the coexistence of FVP and IRBBB, which is very rare.

Abstract The patient is a 19 years‐old man who often wakes up in dreams with palpitations and fatigue. The ECG shows: 1. Sinus rhythm; 2. Preexcitation syndrome. Transesophageal electrophysiological study (TEEPS) diagnosis:High‐risk accessory pathway. During radiofrequency catheter ablation, the patient suddenly developed atrial fibrillation and quickly converted to ventricular fibrillation. After defibrillation, ventricular fibrillation is transformed into sinus rhythm. Subsequently, the patient's high‐risk accessory pathway was successfully ablated. Studies have shown that about 25% of patients with WPW syndrome have a refractory period of less than 250 ms, which is one of the risk factors for the conversion of atrial fibrillation to ventricular fibrillation. Therefore, risk stratification is recommended for these symptomatic patients. From 1980 to 1990, there were literature reports on risk stratification of patients with preexcitation syndrome by TEEPS. But it has not become a routine examination of risk stratification in patients with preexcitation syndrome.The reason may be related to the hardware conditions and risk stratification methods used at that time. The TEEPS equipment currently used in our hospital can control the pacing voltage at about 12 mv on average. The voltage in this case report is 9 mv only. In addition, we successfully stratified the risk of patient with preexcitation syndrome without inducing atrial fibrillation. All the electrophysiological records of the patient during the examination were recorded simultaneously with the 12‐lead ECG and the esophageal lead ECG. These improvements makes TEEPS a simple, safe and reliable non‐invasive cardiac electrophysiological detection technology, which is worth popularizing in hospitals.

The patient is a 19 years‐old man who often wakes up in dreams with palpitations and fatigue. The ECG shows: 1. Sinus rhythm; 2. Preexcitation syndrome. Transesophageal electrophysiological study (TEEPS) diagnosis:High‐risk accessory pathway. During radiofrequency catheter ablation, the patient suddenly developed atrial fibrillation and quickly converted to ventricular fibrillation. After defibrillation, ventricular fibrillation is transformed into sinus rhythm. Subsequently, the patient's high‐risk accessory pathway was successfully ablated. Studies have shown that about 25% of patients with WPW syndrome have a refractory period of less than 250 ms, which is one of the risk factors for the conversion of atrial fibrillation to ventricular fibrillation. Therefore, risk stratification is recommended for these symptomatic patients. From 1980 to 1990, there were literature reports on risk stratification of patients with preexcitation syndrome by TEEPS. But it has not become a routine examination of risk stratification in patients with preexcitation syndrome.The reason may be related to the hardware conditions and risk stratification methods used at that time. The TEEPS equipment currently used in our hospital can control the pacing voltage at about 12 mv on average. The voltage in this case report is 9 mv only. In addition, we successfully stratified the risk of patient with preexcitation syndrome without inducing atrial fibrillation. All the electrophysiological records of the patient during the examination were recorded simultaneously with the 12‐lead ECG and the esophageal lead ECG. These improvements makes TEEPS a simple, safe and reliable non‐invasive cardiac electrophysiological detection technology, which is worth popularizing in hospitals. [ABSTRACT FROM AUTHOR]

Abstract Background Typical atrioventricular accessory pathways (APs) are composed of myocardial cells. They provide electrical connections between atria and ventricles separate from the normal conduction system. Accessory pathways can participate in a macroreentrant circuit resulting in orthodromic atrioventricular reciprocating tachycardia (OAVRT). Hypothesis Because of ultrastructural similarities of typical AP cells to ventricular myocardial cells, we hypothesized lidocaine would be effective in blocking AP conduction, thus terminating OAVRT. Animals Thirty‐two consecutive client‐owned dogs presenting with narrow complex tachyarrhythmias were confirmed to have OAVRT by electrophysiologic study (EPS). Methods Prospective, nonrandomized, single‐arm study with lidocaine administered IV to dogs during OAVRT in 2 mg/kg boluses to a cumulative dose of 8 mg/kg or development of adverse effects. Electrocardiograms were monitored continuously. Subsequent EPS was performed to confirm OAVRT and the absence of other tachycardia mechanisms. Results Twenty‐seven dogs experienced OAVRT cardioversion with lidocaine, before or at the time of adverse effects. Orthodromic atrioventricular reciprocating tachycardia in 5 dogs did not cardiovert before adverse effects, precluding additional dosing. Median total lidocaine dose for cardioversion was 2 mg/kg (interquartile range, 2‐5.5 mg/kg). Dogs with right free wall APs had a significantly higher rate of cardioversion than did dogs with right posteroseptal APs. Conclusions and Clinical Importance Lidocaine successfully cardioverted OAVRT in 84.4% of dogs in our study before adverse effects precluded additional dosing. In 5 dogs with dose limited by adverse effects, it is unknown whether cardioversion would have occurred at a higher cumulative dose.

Background: Significant left ventricular dysfunction may arise in right-sided accessory pathways with ventricular preexcitation in the absence of recurrent or incessant tachycardia. This has just been realized and not enough attention has been paid to it. Methods: In the last 7 years, we identified 12 consecutive children with a diagnosis of ventricular preexcitation- induced dilated cardiomyopathy. This report describes the clinical and echocardiographic characteristics of the patients before and after ablation. Results: Dyssynchronous ventricular contraction was observed by M-mode echocardiography and two-dimensional strain analysis in all patients. The basal and middle segments of the interventricular septum became thin and moved similarly to an aneurysm, with typical bulging during the end of systole. The locations of the accessory pathways were the right-sided septum (n = 5) and the free wall (n = 7). Left ventricular synchrony was obtained shortly after ablation. The left ventricular function recovered to normal and the left ventricular end-diastolic diameter decreased gradually during follow-up. Conclusions: A causal relationship between ventricular preexcitation and the development of dilated cardiomyopathy is supported by the complete recovery of left ventricular function and reversed left ventricular remodeling after the loss of ventricular preexcitation. Preexcitation-related dyssynchrony was thought to be the crucial mechanism. Ventricular preexcitation-induced dilated cardiomyopathy is an indication for ablation with a good prognosis. [ABSTRACT FROM AUTHOR]

Background: Fasciculoventricular (FV) bypass tracts (BTs) are the rarest form of ventricular preexcitation. Although they are not involved in clinically significant reentrant tachycardia, they may cause diagnostic and therapeutic confusion if not properly understood. This study aimed to assess the impact of FV BTs on the diagnosis and treatment of concomitant arrhythmias and cardiac diseases.Methods: Twenty-two patients with FV BTs who underwent electrophysiologic (EP) study were evaluated. The prevalence of concomitant arrhythmias and cardiac diseases in FV BTs was evaluated. The mechanisms of concomitant arrhythmias were determined by EP study and cardiac diseases were diagnosed by echocardiography.Results: One patient had FV BT with complete infra-Hisian atrioventricular (AV) block that mimicked a slow ventricular escape rhythm. Two patients had FV BT with atrial fibrillation or atrial flutter, which was misinterpreted as AV BT requiring emergency DC cardioversion. Eight patients had accompanying AV BTs. In 2 patients with AV BTs, unnecessary RF application was delivered after successful ablation of AV BT because conduction through a FV BT was mistaken for conduction through a residual AV BT. Five patients had no concomitant arrhythmia; however, two of them had hypertrophic cardiomyopathy with symptoms requiring beta-blocker. Patients had not been prescribed beta-blockers to avoid a proarrhythmic response before the EP study because the FV BTs mimicked AV BTs.Conclusion: FV BTs were frequently accompanied by AV BTs or other arrhythmias and cardiac diseases. They may cause misdiagnosis and inappropriate therapy and even unnecessary RF delivery when misinterpreted as AV BTs. [ABSTRACT FROM AUTHOR]

Background: Typical atrioventricular accessory pathways (APs) are composed of myocardial cells. They provide electrical connections between atria and ventricles separate from the normal conduction system. Accessory pathways can participate in a macroreentrant circuit resulting in orthodromic atrioventricular reciprocating tachycardia (OAVRT). Hypothesis: Because of ultrastructural similarities of typical AP cells to ventricular myocardial cells, we hypothesized lidocaine would be effective in blocking AP conduction, thus terminating OAVRT. Animals: Thirty‐two consecutive client‐owned dogs presenting with narrow complex tachyarrhythmias were confirmed to have OAVRT by electrophysiologic study (EPS). Methods: Prospective, nonrandomized, single‐arm study with lidocaine administered IV to dogs during OAVRT in 2 mg/kg boluses to a cumulative dose of 8 mg/kg or development of adverse effects. Electrocardiograms were monitored continuously. Subsequent EPS was performed to confirm OAVRT and the absence of other tachycardia mechanisms. Results: Twenty‐seven dogs experienced OAVRT cardioversion with lidocaine, before or at the time of adverse effects. Orthodromic atrioventricular reciprocating tachycardia in 5 dogs did not cardiovert before adverse effects, precluding additional dosing. Median total lidocaine dose for cardioversion was 2 mg/kg (interquartile range, 2‐5.5 mg/kg). Dogs with right free wall APs had a significantly higher rate of cardioversion than did dogs with right posteroseptal APs. Conclusions and Clinical Importance: Lidocaine successfully cardioverted OAVRT in 84.4% of dogs in our study before adverse effects precluded additional dosing. In 5 dogs with dose limited by adverse effects, it is unknown whether cardioversion would have occurred at a higher cumulative dose. [ABSTRACT FROM AUTHOR]

Background: As there are limited data about the clinical practice of catheter ablation in asymptomatic children and adolescents with ventricular preexcitation on ECG, we performed the multicenter "CASPED" (Catheter ablation in ASymptomatic PEDiatric patients with Ventricular Preexcitation) study. Methods and results: In 182 consecutive children and adolescents aged between 8 and 18 years (mean age 12.9 ± 2.6 years; 65% male) with asymptomatic ventricular preexcitation, a total of 196 accessory pathways (APs) were targeted. APs were right sided (62%) or left sided (38%). The most common right-sided AP location was the posteroseptal region (38%). Ablation was performed using radiofrequency (RF) energy (93%), cryoablation (4%) or both (3%). Mean procedure time was 137.6 ± 62.0 min with a mean fluoroscopy time of 15.6 ± 13.8 min. A 3D mapping or catheter localization system was used in 32% of patients. Catheter ablation was acutely successful in 166/182 patients (91.2%). Mortality was 0% and there were no major periprocedural complications. AP recurrence was observed in 14/166 patients (8.4%) during a mean follow-up time of 19.7 ± 8.5 months. A second ablation attempt was performed in 20 patients and was successful in 16/20 patients (80%). Overall, long-term success rate was 92.3%. Conclusion: In this retrospective multicenter study, the outcome of catheter ablation for asymptomatic preexcitation in children and adolescents irrespective of antegrade AP conduction properties is summarized. The complication rate was low and success rate was high, the latter mainly depending on pathway location. The promising results of the study may have future impact on the ongoing risk–benefit discussion regarding catheter ablation in the setting of asymptomatic preexcitation in children and adolescents. [ABSTRACT FROM AUTHOR]

Background: To our knowledge, no studies have assessed quality of life (QoL) in asymptomatic children with a preexcitation electrocardiogram pattern., Aim: To evaluate the QoL of children with asymptomatic Wolff-Parkinson-White (WPW) syndrome., Methods: This study involved QoL assessment of 31 children with asymptomatic preexcitation and 82 healthy children using the WHOQOL-BREF and the Pediatric Arrhythmia Related Score (PARS), a specific questionnaire that we have developed, which is related to patients' feelings and observations concerning arrhythmia., Results: There were no significant differences between the two groups in all the measured domains; however, there were significant differences regarding general satisfaction with their health condition (P = 0.01). There were no differences in general satisfaction with the QoL, but WPW children more often experienced palpitations than the control group (P <0.001) and were more likely to feel sad (P = 0.046) and nervous (P = 0.04) compared to healthy children., Conclusions: The children with WPW were more dissatisfied with their health compared to healthy children. Although both groups of children had similar levels of satisfaction with their QoL, some areas of physical and psychological parameters of QoL were worse in WPW children. The PARS questionnaire is a useful tool as a disease-specific QoL instrument, which supplements the general questionnaire and aids in clinical practice and decision-making.

Abstract Introduction Accessory pathways (APs) in dogs are mostly right-sided, display nondecremental conduction, and mediate atrioventricular reciprocating tachycardias (AVRTs). Radiofrequency catheter ablation (RFCA) is considered the first-line therapy in human patients to abolish electrical conduction along APs. Animals Seventy-six consecutive client-owned dogs. Material and Methods Retrospective study to describe the precise anatomical distribution and the electrophysiologic characteristics of APs in a large population of dogs and to evaluate long-term success and complication rates of RFCA. Results Eighty-three APs were identified in 76 dogs (92.1% with single APs and 7.9% with multiple APs); 96.4% were right-sided, 3.6% left-sided. Conduction along the APs was unidirectional and retrograde in 68.7% of the cases and bidirectional in 31.3%. Accessory pathways presented retrograde decremental properties in 6.5% of the cases. They mediated orthodromic AVRT in 92.1% of the cases and permanent junctional reciprocating tachycardia in 6.5%. In one case, no AVRT could be induced. In 97.4% of dogs, RFCA was attempted with an acute success rate of 100%. In 7.7% of cases, recurrence of the tachycardia occurred within 18 months, followed by a second definitively successful ablation. A major complication requiring pacemaker implantation was identified in 2.6% of dogs. Discussion Accessory pathway distribution and electrophysiologic properties in these 76 dogs were similar to previous report. Long-term success and complication rates of RFCA in dogs appeared very similar to results of humans. Conclusion Radiofrequency catheter ablation of APs can be performed with a high success rate and low incidence of complications. [ABSTRACT FROM AUTHOR]

Abstract: Introduction: The autonomic nervous system has a regulatory effect on cardiac electrophysiology and arrhythmogenesis. We aimed to assess cardiac autonomic status using heart rate variability (HRV) parameters in children with ventricular preexcitation. Methods: The electrocardiography, Holter monitoring, transesophageal electrophysiological study (TEEPS), and invasive electrophysiological study (EPS) results of ventricular preexcitation patients obtained over a 7‐year period in our clinic were evaluated. According to the TEEPS results, patients’ accessory pathway conduction was classified as adverse (n = 40) or nonadverse (n = 25). The HRV parameters of patients were compared according to tachycardia inducibility that assessed by TEEPS and EPS. Also, HRV parameters were compared in patients with adverse and nonadverse pathway conduction. Further, the HRV parameters of preexcitation patients were compared with those of healthy controls. Results: LF/HF, the best measure of sympathovagal balance, was statistically higher in patients with adverse conduction than in patients without adverse conduction and controls (P  =  0.001). The LF/HF ratio was higher in ventricular preexcitation patients with inducible tachycardia than those without in EPS (P  =  0.001). In addition, the LF/HF ratio was higher in symptomatic ventricular preexcitation patients than asymptomatic ones (P  =  0.001). No difference in HRV parameters was found between preexcitation patients and controls. Conclusion: Autonomic tonus in patients with ventricular preexcitation may affect accessory pathway conduction properties, tachycardia inducibility, and symptomology. The indicator of sympathovagal balance, LF/HF ratio, increased in ventricular preexcitation patients with inducible tachycardia and those that were symptomatic. [ABSTRACT FROM AUTHOR]

We present a patient with non-cardiac sarcoidosis complicated with manifest ventricular preexcitation. Initially, cardiac involvement of sarcoidosis was suspected from the echocardiographic findings showing localized hypokinesia at the left ventricular basal inferior wall. We, however, considered that the hypokinesia was a preexcitation-induced mechanical dyssynchrony rather than cardiac sarcoidosis, because polarities of the delta-waves indicated a left ventricular inferior accessory pathway. Temporal administration of oral flecainide acetate eliminated the basal left ventricular motion abnormality. Accordingly, we could successfully differentiate the mechanism of hypokinesia. In this context, we could rule out cardiac sarcoidosis, and initiation of glucocorticoid therapy was reasonably withheld. [ABSTRACT FROM AUTHOR]

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Background: Wolff-Parkinson-White syndrome is a congenital abnormality of the cardiac conduction system caused by the presence of an abnormal accessory electrical pathway between the atria and the ventricles. This can result in intermittent tachyarrhythmias such as supraventricular tachycardia. In rare occasions, sudden death may occur from atrial fibrillation with rapid ventricular conduction. Supraventricular tachycardia typically has a sudden onset and offset, classified as a paroxysmal arrhythmia. Because of the variable occurrence, Wolff-Parkinson-White syndrome may go undiagnosed in the immediate newborn period.Purpose: To highlight arrhythmia as a possible cause of sudden decompensation in infants.Case Findings/results: The clinical presentation of this infant is complex and a number of potential diagnoses were considered. Preexcitation on electrocardiogram resulted in the diagnosis of Wolff-Parkinson-White syndrome.Implications For Practice: Nurses caring for infants should be alert to tachycardia and irregularities of the heart rate, including those in the prenatal history, and should report them for evaluation. While all parents should be taught to watch for signs of illness, parents of infants with Wolff-Parkinson-White have additional learning needs, including recognizing early signs and symptoms of heart failure. [ABSTRACT FROM AUTHOR]

Background Intermittent Wolff-Parkinson-White (WPW) syndrome is considered to have a lower risk of sudden death. Fewer data exist regarding electrophysiologic (EP) characteristics and the natural history of intermittent WPW in children. Methods All patients with WPW age 1-18 years at a single institution (1996-2013) were reviewed. Patients with intermittent preexcitation were compared to those with loss of preexcitation on Holter/exercise testing and those with persistent preexcitation. High-risk accessory pathway (AP) was defined as AP effective refractory period (APERP), block cycle length, or shortest preexcited RR interval during atrial fibrillation ≤250 ms. Results A total of 295 patients were included: 226 (76.6%) persistent, 39 (13.2%) intermittent, and 30 (10.2%) loss of preexcitation Holter/exercise. There were no differences in symptoms between groups. Median interquartile range APERP was significantly longer in intermittent WPW (380 [320, 488] ms vs 320 [300, 350] ms persistent, 310 [290, 330] ms loss of preexcitation Holter/exercise; P = 0.0008). At baseline, there was no difference between groups in frequency of high-risk pathways. However, when isoproterenol values were included, high-risk pathways were more frequent among patients with loss of preexcitation on Holter/exercise (54% vs 16% persistent, 11% intermittent; P = 0.005). There was one death in a patient with loss of preexcitation on exercise testing, no EP study, and prior drug use. A second patient with persistent WPW and APERP 270 ms required resuscitation following a methadone overdose. Conclusion Intermittent preexcitation in children does not connote a lower risk AP by EP criteria or reduced symptoms. The low number of pediatric WPW patients who develop preexcited atrial fibrillation or sudden death warrants larger studies to investigate these outcomes. [ABSTRACT FROM AUTHOR]