Atrial fibrillation in patients with an accessory pathway: importance of the conduction properties of the accessory pathway

Management of Arrhythmias in the Cardiovascular Intensive Care Unit

Arrhythmias in the cardiovascular intensive care unit (CVICU) can be difficult to manage because of the complex hemodynamic and respiratory states of critically ill patients. Treating physicians must be educated to prevent, diagnose, and treat a multitude of tachyarrhythmias and bradyarrhythmias. In this review article, the authors outline a pragmatic approach to patient assessment, arrhythmia diagnosis, and management of the most common arrhythmias seen in the CVICU.

Atrial fibrillation: primary prevention, secondary prevention, and prevention of thromboembolic complications: part 1

Atrial fibrillation (AF), is the most common sustained cardiac arrhythmia. It was once thought to be benign as long as the ventricular rate was controlled, however, AF is associated with significant cardiac morbidity and mortality. Increasing life expectancy driven by improved health care and decreased fertility rates has, in most of the world, resulted in the population aged ≥65 years growing more rapidly than the overall population. As the population ages, projections suggest that the burden of AF may increase more than 60% by 2050. Although considerable progress has been made in the treatment and management of AF, primary prevention, secondary prevention, and prevention of thromboembolic complications remain a work in progress. This narrative review was facilitated by a MEDLINE search to identify peer-reviewed clinical trials, randomized controlled trials, meta-analyses, and other clinically relevant studies. The search was limited to English-language reports published between 1950 and 2021. Atrial fibrillation was searched via the terms primary prevention, hyperthyroidism, Wolff-Parkinson-White syndrome, catheter ablation, surgical ablation, hybrid ablation, stroke prevention, anticoagulation, left atrial occlusion and atrial excision. Google and Google scholar as well as bibliographies of identified articles were reviewed for additional references. In these two manuscripts, we discuss the current strategies available to prevent AF, then compare noninvasive and invasive treatment strategies to diminish AF recurrence. In addition, we examine the pharmacological, percutaneous device and surgical approaches to prevent stroke as well as other types of thromboembolic events.

Evaluation of left atrial and left ventricular functions in patients with Wolff-Parkinson-White syndrome before and after radiofrequency catheter ablation using three-dimensional speckle tracking echocardiography

BACKGROUND

Wolff-Parkinson-White (WPW) syndrome is one of the most common congenital cardiac abnormalities among ventricular pre-excitation syndromes. Radiofrequency catheter ablation (RFCA) treatment of accessory pathways (APs) in WPW patients is an established curative therapy restoring normal atrioventricular conduction. We have not encountered any studies evaluating both the LA and LV functions of these patients before and after RFCA with three dimensional-speckle tracking echocardiography (3D-speckle tracking echocardiography (STE)).

AIM

The purpose of the current study was to assess the LA and LV functions in patients with WPW syndrome before and after RFCA using 3D-STE.

METHODS

A total of 21 patients with WPW syndrome who had been scheduled for RFCA were prospectively recruited for this study. 3D-STE examinations of the patients were performed 12-24 h before ablation and 1 month after ablation.

RESULTS

The LV-global longitudinal strain (LV-GLS) and LV-global circumferential strain (LV-GCS) were significantly depressed in the pre-RFCA WPW group than in the control group (-14.3 ± 2.1 vs. -21.5 ± 2.2, p < .001; -12.6 ± 1.8 vs. -20.4 ± 1.8, p < .001, respectively). The left atrial strain-reservoir (LAS-r) and LAS-active were significantly decreased in the pre-RFCA WPW group than in the control group (31.9 ± 2.4 vs. 48.8 ± 2.6, p < .001; 11.7 ± 2 vs. 26.5 ± 2.1, p < .001, respectively). The LV-GLS, LV-GCS, LAS-r, and LAS-active values improved after RFCA compared to before.

CONCLUSION

The results of our study indicated that there are subclinical impairments in LV and LA myocardial dynamics in the apparently healthy WPW patients, and these deteriorations improve after RFCA of AP.

Speckle-tracking echocardiography can predict atrial fibrillation in patients with supraventricular tachycardia

PURPOSE

Atrioventricular nodal reentry tachycardia (AVNRT) is the most common supraventriculer arrhythmia in daily clinical practice. Comorbidity of AVNRT and atrial fibrillation (AF) has been well documented in some patients and AF development has been observed more frequently in AVNRT patients during their long-term follow-up. This study was conducted in order to investigate the left atrial two-dimensional-speckle-tracking echocardiographic (STE) parametres as the predictors of the occurence of AF in long-term follow-up in patients with spontaneously developed AF during AVNRT ablation.

METHODS

Two hundred and thirty two consecutive AVNRT patients who developed spontaneous AF during ablation procedure were included in the study. The patients were followed up for a mean follow-up period of 6.2 ± 2.1 years. All patients were evaluated using the 2D-STE method. AF was developed in 34 patients during the follow-up period. Cox regression analysis was performed in order to identify the independent predictors of AF occurence.

RESULTS

Left atrial LA-res, LA-pump, LA-SRs, LA-SRe, and LA-SRa values were found to be significantly decreased in the group of patients that developed AF during the follow-up period (p < .001 for all aforementioned values). Multivariate cox regression analysis revealed that LA-res (hazard ratio [HR], 0.367; 95% confidence interval [CI], 0.161-0.0.683, p < .001) and SRe (HR, 0.472; 95% CI, 0.346-0.825, p = .006) were independent risk factors associated with the occurrence of AF.

CONCLUSION

In conclusion, it was demonstrated for the first time with this study that 2D-STE can effectively predict the development of AF in long-term follow-up in patients with spontaneously developed AF during AVNRT ablation.

Arrhythmias with Bystander Accessory Pathways

An accessory pathway (AP) could manifest its presence exclusively during an orthodromic supraventricular tachycardia or with preexcitation during sinus rhythm (SR). The manifestations of the presence of an AP depend on its ability to conduct antegradely from atrium (A) to ventricle (V), retrogradely (V to A), or both. AP retrograde conduction is necessary to establish an atrioventricular reentrant tachycardia circuit. If an AP can only conduct antegradely, it will function as a bystander AV connection during independent arrhythmias. The correct diagnosis of this condition is very important, as it will determine the immediate and long-term management.

Incidence, clinical, electrophysiological characteristics and outcomes of patients with Wolff-Parkinson-White syndrome and atrial fibrillation

AIMS AND OBJECTIVES

Atrial fibrillation (AF) with preexcitation can be life threatening. Our study evaluated the incidence, clinical features, electrophysiologic characteristics and outcomes of patients presenting with AF and fast ventricular rates associated with an antegrade conducting accessory pathway.

METHODS

Hospital data of patients who had undergone electrophysiology study and radiofrequency ablation for AF and Wolff-Parkinson-White (WPW) syndrome was retrospectively evaluated over 10 years and prospective data was further collected over 1 year. Out of 2876 patients undergoing electrophysiology study, 320 patients had manifest preexcitation on ECG. Forty one patients who had presented with AF and fast ventricular rates were included in the study.

RESULTS

Forty one (12.8%) patients out of 320 patients of WPW syndrome patients presented with AF and fast ventricular rates. Mean age of presentation was 38.5 ± 12.3 yrs. Twenty nine (72.5%) were male. Most common presenting features were palpitations, presyncope and syncope. Twenty eight (71.1%) patients were electrically cardioverted on presentation, of which two patients having narrow complex tachycardia, when given adenosine, developed AF and fast ventricular rates and had to be electrically cardioverted. Intravenous amiodarone converted AF to sinus rhythm in 11 (28.9%) patients. Right postero-septal pathway (33.3%) followed by coronary sinus epicardial pathway (22.9%) were the most commonly located pathways associated with AF. Five (12.2%) patients had multiple pathways. CS diverticulum was seen in 6 (14.7%) patients. Ablation was done during AF in 6 (14.7%) patients. All except one had immediate successful ablation. One patient had a recurrence of preexcitation on follow up and successfully ablated during redo procedure.

CONCLUSION

AF with WPW syndrome is not uncommon. AF is commonly associated with posteriorly located accessory pathways, CS diverticulum and multiple pathways. Radiofrequency ablation has good outcomes.

Atrial fibrillation and preexcitation - A licence to kill

Atrial fibrillation becomes a potentially lethal arrhythmia in the presence of preexcitation because the rapid ventricular activation can result in ventricular fibrillation. Fortunately, radiofrequency ablation is an effective treatment for these patients. Specific points of interest regarding this association are the mechanism of increased incidence of atrial fibrillation and the current management of patients presenting in atrial fibrillation. These are discussed in this editorial.

Risk-Stratification Strategy for Sudden Cardiac Death in the Very Young Children with Asymptomatic Ventricular Preexcitation

Asymptomatic VPE refers to the presence of this abnormal ECG pattern in the absence of any symptoms. The natural history in these patients is usually benign, and most children (60%) with VPE are usually asymptomatic. However, Sudden Cardiac Death (SCD) has been reported to be the initial symptom in many patients too. The increased risk of SCD is thought to be due to the rapid conduction of atrial arrhythmias to the ventricle, via the AP, which degenerates into Ventricular Fibrillation (VF). The best method to identify high-risk patients with asymptomatic VPE for SCD is the characterization of the electrophysiological properties of the AP through an Electrophysiological Study (EPS). Also, catheter ablation of the AP with radiofrequency as definitive treatment to avoid SCD can be performed by the same procedure with high rates of success. However, the uncertainty over the absolute risk of SCD, the poor positive predictive value of an invasive EPS, and complications associated with catheter ablation have made the management of asymptomatic VPE challenging, even more in those children younger than 8-year-old, where there are no clear recommendations. This review provides an overview of the different methods to make the risk stratification for SCD in asymptomatic children with, as well as our viewpoint on the adequate approach to those young children not included in current guidelines.

Atrioventricular accessory pathways in 89 dogs: Clinical features and outcome after radiofrequency catheter ablation

Background

Atrioventricular 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/Objectives

To study clinical features, electrophysiologic characteristics, and outcome of RFCA in dogs with APs.

Animals

Eighty‐nine dogs presented consecutively for RFCA of APs.

Methods

Case series.

Results

Labrador 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/Conclusions

Accessory 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.

Asymptomatic Ventricular Pre-excitation: Between Sudden Cardiac Death and Catheter Ablation

Debate about the best clinical approach to the management of asymptomatic patients with ventricular pre-excitation and advice on whether or not to invasively stratify and ablate is on-going. Weak evidence about the real risk of sudden cardiac death and the potential benefit of catheter ablation has probably prevented the clarification of action in this not infrequent and sometimes conflicting clinical situation. After analysing all available data, real evidence-based medicine could be the alternative strategy for managing this group of patients. According to recent surveys, most electrophysiologists invasively stratify. Based on all accepted risk factors - younger age, male, associated structural heart disease, posteroseptal localisation, ability of the accessory pathway to conduct anterogradely at short intervals of ≤250 milliseconds and inducibility of sustained atrioventricular re-entrant tachycardia and/or atrial fibrillation - a shared decisionmaking process on catheter ablation is proposed.

Risk factors responsible for atrial fibrillation development between symptomatic patients with concealed or manifest atrioventricular accessory pathways

Background

Patients with manifest atrioventricular accessory pathways (mAPs) have a greater tendency to develop atrial fibrillation (AF) compared with patients with concealed atrioventricular accessory pathways (cAPs). However, the risk factors of developing AF in patients with various atrioventricular accessory pathways (APs) are not clear.

Methods

This retrospective study included 460 symptomatic patients with either cAPs (n = 246) or mAPs (n = 214) who underwent electrophysiological study and successful radiofrequency catheter ablation of APs. Clinical and electrophysiological characteristics were compared between cAPs and mAPs and between AF and non-AF groups with cAPs or mAPs. Independent risk factors of AF were analyzed using multivariate logistic regression.

Results

AF was more frequent in mAPs group than in cAPs group (23.4% vs 9.8%, p < 0.01). Clinical features were similar between cAPs and mAPs. Anterograde conduction properties served as the major electrophysiological feature of mAPs. Multivariate analysis indicated that mAPs, hypertension, post-ablation P wave dispersion (Pd), N-terminal proB-type natriuretic peptide (NT-proBNP) and creatinine were independent risk factors of AF in the complete cohort. Hypertension, post-ablation Pd and high-sensitivity C-reactive protein (hsCRP) were independent risk factors of AF in cAPs group. Post-ablation Pd, NT-proBNP, creatinine and shorter effective refractory period of anterograde accessory pathways (AAP ERP) were independent risk factors of AF in mAPs group.

Conclusions

Results from this study demonstrate that the risk factors of AF are not homogenous between concealed and manifest APs, which might suggest heterogeneous pathogenesis of AF in these two types of APs.

Assessment of atrial fibrillation and vulnerability in patients with Wolff-Parkinson-White syndrome using two-dimensional speckle tracking echocardiography

Purpose

The aim was to assess atrial fibrillation (AF) and vulnerability in Wolff-Parkinson-White (WPW) syndrome patients using two-dimensional speckle tracking echocardiography (2D-STE).

Methods

All patients were examined via transthoracic echocardiography and 2D-STE in order to assess atrial function 7 days before and 10 days after RF catheter ablation. A postoperative 3-month follow-up was performed via outpatient visit or telephone calls.

Results

Results showed significant differences in both body mass index (BMI) and supraventricular tachycardia (SVT) duration between WPW patients and DAVNP patients (both P<0.05). Echocardiography revealed that the maximum left atrial volume (LAV_max) and the left ventricular mass index (LVMI) in diastole increased noticeably in patients with WPW compared to patients with DAVNP both before and after ablation (all P<0.05). Before ablation, there were obvious differences in the levels of SRs, SRe, and SRa from the 4-chamber view (LA) in the WPW patients group compared with patients in the DAVNP group (all P<0.05). In the AF group, there were significant differences in the levels of systolic strain rate (SRs), early diastolic strain rate (SRe), and late diastolic strain rate (SRa) from the 4-chamber view (LA) both before and after ablation (all P<0.05). In the non-AF group, there were decreased SRe levels from the 4-chamber view (LA/RA) pre-ablation compared to post-ablation (all P<0.05).

Conclusion

Our findings provide convincing evidence that WPW syndrome may result in increased atrial vulnerability and contribute to the development of AF. Further, RF catheter ablation of AAV pathway can potentially improve atrial function in WPW syndrome patients. Two-dimensional speckle tracking echocardiography imaging in WPW patients would be necessary in the evaluation and improvement of the overall function of RF catheter ablation in a long-term follow-up period.

Atrial Fibrillation in the Wolff-Parkinson-White Syndrome

Since the advent of catheter ablation for atrial fibrillation (AF) aiming the pulmonary veins a few years ago, there has been an overwhelming interest and a dramatic increase in AF investigation. AF has a different dimension in the context of the Wolff-Parkinson-White (WPW) syndrome. Indeed, AF may be a nightmare in a young person that has an accessory pathway (AP) with fast anterograde conduction. It may be life-threatening if an extremely rapid ventricular response develops degenerating into ventricular fibrillation. Therefore, it is very important to know the mechanisms involved in the development of AF in the WPW syndrome. There are several possible mechanisms that may be involved in the development of AF in the WPW syndrome, namely, spontaneous degeneration of atrioventricular reciprocating tachycardia into AF, the electrophysiological properties of the AP, the effects of AP on atrial architecture, and intrinsic atrial muscle vulnerability. Focal activity, multiple reentrant wavelets, and macroreentry have all been implicated in AF, perhaps under the further influence of the autonomic nervous system. AF can also be initiated by ectopic beats originating from the pulmonary veins, and elsewhere. Several studies demonstrated a decrease incidence of AF after successful elimination of the AP, suggesting that the AP itself may play an important role in the initiation of AF. However, since AF still occurs in some patients with the WPW syndrome even after successful ablation of the AP, there should be other mechanisms responsible for the development of AF in the WPW syndrome. There is a clear evidence of an underlying atrial muscle disease in patients with the WPW syndrome. Atrial myocardial vulnerability has been studied performing an atrial endocardial catheter mapping during sinus rhythm, and analizing the recorded abnormal atrial electrograms. This review analizes the available data on this singular setting since AF has a reserved prognostic significance in patients with the WPW syndrome, and has an unusually high incidence in the absence of any clinical evidence of organic heart disease.

Evaluation of atrial vulnerability immediately after radiofrequency catheter ablation of accessory pathway in patients with Wolff-Parkinson-White syndrome

PURPOSE

The intrinsic atrial vulnerability is proposed as one of the mechanisms of paroxysmal atrial fibrillation (PAF) in Wolff-Parkinson-White (WPW) syndrome. In this study, we examined the early changes in atrial refractoriness and intra- and inter-atrial conduction times after radiofrequency (RF) catheter ablation of accessory pathway (AP).

METHODS

Twenty-four consecutive patients with WPW syndrome and documented AV reciprocating tachycardia but without history of PAF (fourteen male, mean age 39 +/- 9.5 years) and 27 control subjects (six female, mean age 51.4 +/- 10.1 years) with AV nodal reentrant tachycardia (AVNRT) who underwent ablation of the slow AV nodal pathways were enrolled into the study. Regional atrial effective refractory periods (AERPs), AERP dispersion, and intra- and inter-atrial conduction times were obtained before and 30 min after ablation and were compared between two groups. In the study group, patients with and without inducible AF were also compared regarding these parameters.

RESULTS

In the study group, AERPs in higher right atrium and right posterolateral atrium were significantly increased, and AERP dispersion, intra-atrial, and inter-atrial conduction times were significantly decreased after ablation; AERP in distal coronary sinus was unchanged. In control group, no significant difference was observed in these parameters. Inducibility of AF was significantly reduced following ablation of AP in the study group (from seven to zero of 24 patients, p = 0.016). Comparison between patients with (n = 7) and without (n = 17) AF revealed that left atrium diameter was larger, AERPs in the right posterolateral atrium before and after ablation, and ERP of AP were shorter in AF group.

CONCLUSION

In WPW syndrome patients, RF catheter ablation of AP results in an 'immediate' decrease in atrial vulnerability. Since inducibility of AF becomes more difficult in this less vulnerable atrium, the AP itself may play an important role in the development of AF.

Reentry in an accessory atrioventricular pathway as a trigger for atrial fibrillation initiation in manifest Wolff-Parkinson-White syndrome: a matter of reflection?

BACKGROUND

Patients with an accessory pathway (AP) have an increased propensity to develop atrial fibrillation (AF), but the mechanism is unknown.

OBJECTIVE

The purpose of this study was to identify crucial risk factors and to test the hypothesis that reflection and/or microreentry of atrial impulses propagating into the AP triggers AF.

METHODS

Five hundred thirty-four patients successfully treated with radiofrequency ablation of AP at two university hospitals were evaluated. Patients were separated into those with concealed vs those with manifest AP in terms of their propensity to develop AF. To investigate AF triggering mechanisms, linear and branched two-dimensional models of atrium-to-ventricle propagation across a heterogeneous 1 x 6 AP using human ionic kinetics were simulated.

RESULTS

A history of AF was twice as common in patients with manifest AP vs concealed AP irrespective of AP location. AF was more likely to occur in older males and in patients with larger atria. There was no correlation between AF history and AP refractory measures. However, the electrophysiologic properties of APs seemed to fulfill the prerequisites for reflection and/or microreentry of atrially initiated impulses. In the linear AP model, repetitive atrial stimulation resulted in progressively larger delay of atrium-to-ventricle propagation across the passive segment. Eventually, sufficient time for repolarization of the atrial segment allowed for reflection of an impulse that activated the entire atrium and by wavefront-wavetail interaction with a new atrial stimulus AF reentry was initiated. Simulations using the branched model showed that microreentry at the ventricular insertion of the AP could also initiate AF via retrograde atrial activation as a result of unidirectional block at the AP-ventricle junction.

CONCLUSION

Propensity for AF in patients with an AP is strongly related to preexcitation, larger atria, male gender, and older age. Reflection and microreentry at the AP may be important for AF initiation in patients with manifest (preexcited) Wolff-Parkinson-White syndrome. Similar mechanisms also may trigger AF in patients without an AP.

Anatomic distribution and electrophysiologic properties of accessory atrioventricular pathways in dogs

OBJECTIVE

To evaluate the anatomic distribution and electrophysiologic properties of accessory pathways (APs) in dogs.

DESIGN

Case series.

ANIMALS

10 dogs with tachyarrhythmias associated with an AP.

PROCEDURES

Each dog underwent electrophysiologic testing to determine the inducibility of documented and undocumented arrhythmias and to identify location, conduction properties, and antegrade and retrograde effective refractory periods of the APs. Radiofrequency catheter ablation was then performed.

RESULTS

15 APs were identified; 7 dogs each had a single AP, and 3 had multiple APs. Fourteen of the 15 APs were right-sided (6 right free wall, 4 posteroseptal, 3 midseptal, and 1 anteroseptal), and 1 was left-sided (left free wall). All APs conducted in an all-or-none fashion. Unidirectional retrograde conduction was observed in 11 APs, and bidirectional conduction was observed in 4. All documented tachyarrhythmias could be induced during electrophysiologic testing; atrial fibrillation was also inducible in 2 dogs. Mean +/- SD cycle duration of orthodromic atrioventricular reciprocating tachycardia was 215.80 +/- 44.87 milliseconds. Mean shortest R-R interval during atrial fibrillation was 247.33 +/- 83.17 milliseconds.

CONCLUSIONS AND CLINICAL RELEVANCE

Results suggested that in dogs, most APs are right-sided, had unidirectional retrograde conduction, and are associated with various arrhythmias, including orthodromic atrioventricular reciprocating tachycardia and atrial fibrillation without evidence of pre-excitation.

The Wolff–Parkinson–White electrocardiogram pattern in athletes: how and when to evaluate the risk for dangerous arrhythmias. The opinion of the paediatric cardiologist

Although diagnostic assessment and treatment have been described in detail in patients with symptomatic Wolff-Parkinson-White (WPW) syndrome, the management of asymptomatic subjects remains controversial. Usually they are assumed to have a benign prognosis, although they do very occasionally present with ventricular fibrillation (VF) as the first manifestation of the syndrome. Discovering a WPW pattern in a previously asymptomatic athlete on a routine electrocardiogram (ECG) identifies the necessity for more accurate screening tests. However, non-invasive methods (Holter monitoring, exercise treadmill testing) seem to be relatively incomplete for risk stratification, especially for athletes. Current guidelines do not always recommend a routine electrophysiological study (EPS) in patients with an asymptomatic WPW ECG pattern, especially in children younger than 12 years. Individuals who engage in high-risk occupations or those patients who have a pre-excitation pattern which precludes them from following their chosen career or activities may be exceptions. The presence of inducible reciprocating tachycardia during EPS, especially when it triggers atrial fibrillation with short RR interval, can represent a specific risk marker of dangerous arrhythmias.

Atrial vulnerability is a major mechanism of paroxysmal atrial fibrillation in patients with Wolff–Parkinson–White syndrome

Atrioventricular re-entrant tachycardia is the most common form of tachycardia in patients with Wolff-Parkinson-White (WPW) syndrome where one or more accessory pathways are present between atria and ventricles. Paroxysmal atrial fibrillation (PAF) is also a relatively common form of tachycardia in these patients. The mechanisms of PAF in patients with WPW syndrome are not completely understood. Previous studies have mainly focused on the role of accessory pathways in the development of PAF. However, up to 24% of patients still experience PAF after successful ablation of accessory pathways by surgical incision or radiofrequency catheter ablation techniques. We hypothesized that there are two primary mechanisms involved in the pathogenesis of PAF in patients with WPW syndrome. One is related to the accessory pathways that predispose the atria to fibrillation; the other is increased atrial vulnerability that is independent of the accessory pathways. Clarification of these mechanisms is critical in developing more effective means for the prevention or treatment of PAF in patients with WPW syndrome.

Recurrence of symptomatic atrial fibrillation after successful catheter ablation of atrioventricular accessory pathways: a multivariate regression analysis

The primary aim of this study is to investigate the factors related to the recurrence of atrial fibrillation (AF) after a successful ablation of atrioventricular accessory pathway. Thirty-seven patients with spontaneous AF (study group) were selected from 401 consecutive patients who underwent radiofrequency catheter ablation of atrioventricular accessory pathway. A multivariate regression analysis was used in order to evaluate the relationships between AF recurrence and patients' age, sex, atrial size, left ventricular function, location of accessory pathways, heart rate during atrioventricular re-entrant tachycardia and atrial vulnerability (induction of sustained AF) after a successful ablation. Atrioventricular accessory pathway was abolished in 36 of the study group patients and 351 of the control group patients. During the follow-up of 36 +/- 11 months, four patients (11.1%) from the study group experienced sustained AF. Multivariate regression analysis showed that, in patients with pre-ablation AF, older age and post-ablation atrial vulnerability were the only independent predictive factors for AF recurrence. We concluded that radiofrequency catheter ablation of atrioventricular accessory pathway greatly reduces the risk of AF in patients who had a history of symptomatic AF. Older patients and patients with inducible AF after accessory pathway ablation are at an increased risk of AF recurrence. These patients should be closely monitored after successful ablation of atrioventricular accessory pathways.

Increased dispersion of refractoriness in patients with atrial fibrillation in the early postoperative period after coronary artery bypass grafting

INTRODUCTION

Increased atrial effective refractory period (AERP) dispersion is well correlated with vulnerability to atrial fibrillation (AF). However, the preoperative electrophysiologic characteristics of atrial abnormalities that may play an important role in the development of AF postoperatively in patients with coronary artery bypass grafting (CABG) have not been investigated in detail.

METHODS AND RESULTS

Fifty-six consecutive patients who underwent CABG were enrolled in this study. Eighteen patients (14 men and 4 women; mean age 57.7 +/- 5.2 years) with AF in the early postoperative period and 38 patients (28 men and 10 women; mean age 56.3 +/- 6.4 years) without AF were compared with regard to preoperative clinical, echocardiographic, angiographic, and electrophysiologic parameters. Preoperative PA interval and AERP dispersion values were higher (P < 0.05) in patients who developed AF in the early postoperative period. PA interval (P < 0.05, odds ratio = 1.64, 95% confidence interval 1.17-2.30), AERP in the high right atrium (AERP(HRA); P < 0.05, odds ratio = 0.94, 95% confidence interval 0.91-0.97), AERP in the right posterolateral atrium (AERP(RPL); P < 0.05, odds ratio = 0.79, 95% confidence interval 0.63-0.98), AERP in the distal coronary sinus (AERP(DCS); P < 0.05, odds ratio = 0.84, 95% confidence interval 0.74-1.02), and AERP dispersion (P < 0.001, odds ratio = 1.29, 95% confidence interval 1.12-1.47) were independently related to post-CABG AF in univariate analysis. Increases in preoperative PA interval and AERP dispersion were found to be associated with a high risk for development of post-CABG AF.

CONCLUSION

AERP dispersion is a suitable electrophysiologic indicator for atrial vulnerability. The presence of increased preoperative AERP dispersion and PA interval may indicate patients at high risk for development of AF in the early postoperative period after coronary artery bypass grafting.

Evaluation and treatment of other arrhythmic causes of syncope in children and adolescents with an apparently normal heart: Wolff-Parkinson-White syndrome and right ventricular cardiomyopathy

Syncope could be a symptom of tachyarrhythmias related to the Wolff-Parkinson-White syndrome, or the consequence of the ventricular tachycardias seen in patients with Arrhythmogenic Right Ventricular Cardiomyopathy. Syncope should be considered the consequence of atrial fibrillation or flutter, with rapid conduction over the accessory atrioventricular connection in Wolff-Parkinson-White syndrome, and these patients are at risk of presenting with ventricular fibrillation and sudden death. Radiofrequency ablation of the anomalous, accessory connection, which can be performed with high success and low complication rates, should be the first line of treatment for symptomatic children and adolescents with Wolff-Parkinson-White. Arrhythmogenic Right Ventricular Cardiomyopathy is a rare disorder of the cardiac muscle affecting predominantly, although not exclusively, the right ventricle. Clinical presentation varies from asymptomatic cases to patients with severe symptoms related to life-threatening arrhythmias, right ventricular failure, or congestive heart failure with involvement of both ventricles. The clinical diagnosis is difficult. A set of major and minor criteria has been proposed to help to identify patients with this disease. Without an identified cause, the treatment of patients with Arrhythmogenic Right Ventricular Cardiomyopathy is symptomatic. Medical management of the associated congestive heart failure, pharmacologic treatment of the arrhythmias, radiofrequency ablation and implantable cardioverter-defibrillator therapy should all be considered.

Atrioventricular nodal tachycardia occurring during atrial fibrillation

We describe the case of a 32-year-old woman with palpitations and atrial fibrillation (AF) as the only documented arrhythmia. The patient underwent electrophysiologic study and was found to have inducible AV nodal reentrant tachycardia (AVNRT). During a prolonged episode of AVNRT, AF developed in both atria, but AVNRT persisted. Dissociation of the atria during AVNRT is evidence that the atrium is not necessary in AVNRT. This case also illustrates the utility of an electrophysiologic study in locating a potentially curable arrhythmia as the primary cause of AF in young patients.

Importance of retrograde atrial activation in atrial fibrillation genesis in the initiation of atrial fibrillation in Wolff-Parkinson-White syndrome. Comparison of atrial electrophysiologic parameters between patients with different atrial fibrillation genesis (initiation sites) in atria

The changes in the duration of atrial electrograms during different atrial activation sequences from a sinus rhythm were evaluated to test the hypothesis that the prolongation of atrial electrogram duration caused by the different atrial activation sequence is more prominent at the site of atrial fibrillation (Afib) genesis (initiation site) than other areas. In 39 patients with single retrograde left-sided accessory connection who had inducible transient atrial fibrillation during an electrophysiologic study, the site of Afib genesis was determined and classified into three groups, i.e., 1) high right atrial genesis (HRA), 2) low right atrial genesis (LRA), and 3) left atrial genesis (LA). Single premature extrastimuli after 8 basic drive trains (600 ms) were delivered at the HRA and the right ventricular apex. Three atrial electrophysiologic parameters were evaluated at three atrial sites, i.e., 1) HRA, 2) LRA, and 3) coronary sinus. The atrial vulnerability parameters were as follows; 1) %A2/A1: % prolongation of atrial electrogram duration during premature beat (A2) in comparison with basic drive (A1), 2) wavelength index (WLI): calculated as [effective refractory period]/[A2], and 3) retrograde activation index (RAI): calculated as [A1 during retrograde activation; i.e., RVA pacing/[A1 during antegrade activation, i.e., HRA pacing], shown as a percentage. The Afib genesis was HRA in 20, LRA in 12 and LA in 7 patients. At the HRA recording site, %A2/A1 and RAI were the largest and WLI the shortest in the HRA genesis group in comparison with the other two groups. Similarly, at the LRA and LA recording sites, %A2/A1 and RAI were the largest and WLI the shortest in the groups with Afib genesis at these recording sites. In patients with inducible Afib, %A2/A1 and RAI were the highest and WLI the shortest at the atrial recording site close to the site of Afib genesis. Atrial wave prolongation during retrograde atrial activation, possibly the anisotropic conduction, was considered to play a role in initiating Afib as well as a conduction delay during the atrial premature beat.

Assessment of accessory pathway and atrial refractoriness by transoesophageal and intracardiac atrial stimulation: an analysis of methodological agreement

AIMS

Measurement of the refractory properties of asymptomatic overt accessory pathways is performed to assess the risk for significant arrhythmias. We hypothesized that a transoesophageal atrial stimulation (TAS) protocol would accurately predict simultaneously measured invasive intra cardiac stimulation (ICS) of the anterograde effective refractory period of the accessory pathway (AP-ERP) METHODS AND RESULTS: Fourteen single pathway Wolff-Parkinson-White (WPW) syndrome patients underwent TAS during ICS and 24 h prior to it. The AP-ERP was measured using incremental atrial extra stimuli from TAS, the right atrium (RA) and the coronary sinus (CS) using drive trains of 500 and 600 ms. Stimulus latency was measured from intracardiac electrocardiograms. For methodological comparison, Altman-Bland analysis was used to create the limits of agreement (within-patient mean of differences +/- two standard deviations). There were no or small differences in the AP-ERP, as assessed by TAS, compared to RA and CS. Methodological disagreement between the three sites were common, however, and the limits of agreement ranged from +/- 30 to +/- 76 ms. The concordance between TAS and RA, with regards to the AP-ERP value of 270 ms, was 63% when measured as S1S2 and was 67% when measured as A1A2. The stimulation site delay was significantly shorter for TAS compared to RA and CS sites. The two TAS procedures performed a day apart, revealed a coefficient of variation of 9% and a coefficient of reproducibility of 63 ms.

CONCLUSIONS

Despite adequate reproducibility, TAS fails to predict the AP-ERP by ICS. Differences in stimulus latency is responsible, in part, for the disagreement. Invasive ICS cannot be replaced by TAS for risk stratifying WPW patients.

Comparison of arrhythmogenicity of atrial pacing at several right atrial pacing sites: evaluation of canine atrial electrograms during atrial pacing and arrhythmogenicity for atrial fibrillation

The changes in the duration of atrial electrograms and the appearance of AF during atrial pacing were compared among five atrial pacing sites in dogs to clarify the arrhythmogenicity of atrial pacing at different atrial pacing sites. In seven mongrel dogs (15-20 kg), the right atrial surface was exposed by right thoracotomy. Atrial electrograms were recorded via bipolar electrodes with an interelectrode distance of 1.2 mm at four right atrial sites: (1) the high right atrium (HRA), (2) the mid-right atrium (MRA), (3) the low right atrium (LRA), and (4) the center of the pectinate muscle (PM). The duration of the atrial electrograms at these four recording sites were measured during atrial pacing with fixed cycle lengths of 200, 150, and 120 ms delivered at five atrial sites: (1) the HRA, (2) the inferior vena cava (IVC), (3) the right atrial appendage (RAA), (4) Bachman's bundle (BB), and (5) the atrial septum (AS). In each dog, the atrial pacing with the 120-ms cycle length was performed five times at each pacing site to evaluate the inducibility of AF. When AF was induced, the atrial recording site which first showed a fragmented atrial electrogram was considered the initiation site of the AF. AF was induced during 9 of 35 episodes of atrial pacing at the HRA site, 11 of 35 at the IVC site, 5 of 35 at the RAA site, 3 of 35 at the BB site, and none at the AS site. The initiation site of AF was in the HRA site in 11 of 28 episodes of induced AF, in the MRA site in 9 of 28, and in the LRA site in 8 of 28. At each recording site, the shorter the paced cycle length, the longer the duration of the atrial electrogram regardless of the pacing site. During the atrial pacing with the 200-ms cycle length, the HRA pacing resulted in the shortest duration of the atrial electrogram at each recording site in comparison with the other pacing sites. However, during atrial pacing at the two shorter paced cycle lengths, the duration of the atrial electrogram was shorter during the pacing at the BB or AS sites in comparison with the other three pacing sites, i.e., the HRA, IVC, and RAA sites. These results were the same for all atrial recording sites, but the prolongation of the atrial electrogram was most prominent at the HRA and MRA recording sites, which are most likely initiation sites of the induced AF. In the canine atria, (1) the initiation sites of AF were likely to be the HRA, MRA, or LRA sites in comparison with the PM site; and (2) the atrial pacing at the BB or AS sites was considered less arrhythmogenic for AF than the pacing at the HRA, LRA, or RAA sites.

Role of atrial electrophysiology and autonomic nervous system in patients with supraventricular tachycardia and paroxysmal atrial fibrillation

OBJECTIVES

The purposes of this study were to evaluate the atrial electrophysiology and autonomic nervous system in patients who had paroxysmal supraventricular tachycardia (PSVT) associated with paroxysmal atrial fibrillation (PAF).

BACKGROUND

PAF frequently appeared in patients with PSVT. However, the critical determinants for the occurrence of PAF were not clear.

METHODS

This study population consisted of 50 patients who had PSVT with (n=23) and without (n=27) PAF. Atrial pressure, atrial size, atrial effective refractory periods (AERPs), and AERP dispersion were evaluated during baseline and PSVT, respectively. Twenty-four hour heart rate variability and baroreflex sensitivity (BRS) were also examined.

RESULTS

There was greater baseline AERP dispersion in patients with PAF than in those without PAF. The atrial pressure, atrial size, AERPs in the right posterolateral atrium and distal coronary sinus, and AERP dispersion were increased during PSVT as compared with those during baseline. Patients with PAF had greater AERP dispersion than those without PAF during PSVT. The differences of atrial size, right posterolateral AERP, and AERP dispersion between baseline and PSVT were greater in patients with PAF than in those without PAF. BRS, but not heart rate variability, was higher in patients with PAF than in those without PAF. Univariate analysis showed that higher BRS (>4.5 ms/mm Hg, p=0.0002, odds ratio=16.1), AERP dispersion during PSVT (>40 ms, p=0.0008, odds ratio=9.7), and increase of right atrial area during PSVT (>2 cm2, p=0.016, odds ratio=10.7) were significantly correlated with the occurrence of PAF in patients with PSVT.

CONCLUSIONS

Disturbed atrial electrophysiology and higher vagal reflex could play important roles in the genesis of PAF in patients with PSVT.

Retrograde multiple and multifiber accessory pathway conduction in the Wolff-Parkinson-White syndrome: potential precipitating factor of atrial fibrillation

INTRODUCTION

The determinants of susceptibility to atrial fibrillation (AF) and the existence of accessory pathway conduction have remained unidentified in the Wolff-Parkinson-White (WPW) syndrome. We tested the hypothesis that excitation inputs into the atrium over a retrograde multiple or multifiber accessory pathway during AV reentrant tachycardia (AVRT) could precipitate initiation of AF.

METHODS AND RESULTS

Two hundred fifty consecutive patients with WPW syndrome underwent electrophysiologic study and radiofrequency catheter ablation. The patients were classified into two groups according to the study results: 29 with retrograde multiple or multifiber accessory pathway (MP) and 221 with retrograde single accessory pathway (SP). Compared with the SP patients, the MP patients showed a significantly higher incidence of clinical AF (MP vs SP: 19/29 vs 51/221, P < 0.01), induced AF (12/29 vs 32/221, P < 0.01), and initiated AF during ventricular pacing and AVRT (10/12 vs 17/32, P < 0.05). There were no differences between the two groups in incidence of clinical and induced AVRT (24/29 vs 200/221 and 25/29 vs 206/221, respectively), mean cycle length of induced AVRT, or electrophysiologic parameters of the accessory pathway. AF inducibility during AVRT or ventricular pacing was eliminated by partial ablation in 7 of 10 patients with MP. After total ablation, the incidence of induced AF was similar between the two groups (MP vs SP: 1/29 vs 11/221).

CONCLUSION

The existence of a retrograde multiple or multifiber accessory pathway in patients with WPW syndrome is associated with a higher incidence of clinical and induced AF. Successful ablation of the retrograde multiple or multifiber accessory pathway can eliminate the induction of both AVRT and AF.

Pharmacologic management of supraventricular tachycardias in children. Part 1: Wolff-Parkinson-White and atrioventricular nodal reentry

OBJECTIVE

To review the literature regarding the use of antiarrhythmic agents in the management of Wolff-Parkinson-White (WPW) syndrome and atrioventricular nodal reentry tachycardia (AVNRT) in infants and children, and to discuss the advantages and disadvantages of specific agents in each arrhythmia in an effort to develop treatment guidelines.

DATA SOURCES

A MEDLINE search encompassing the years 1966-1996 was used to identify pertinent literature for discussion. Additional references were found in the articles that were retrieved via MEDLINE.

STUDY SELECTION

Clinical trials that address the use of antiarrhythmic agents for the treatment of the supraventricular tachycardias WPW and AVNRT in children were selected. Literature pertaining to dosage, pharmacokinetics, efficacy and toxicity of antiarrhythmic agents in children were considered for possible inclusion in the review, and information judged to be pertinent by the authors was included in the discussion.

DATA EXTRACTION

Although there are numerous reports of antiarrhythmic use in children, very few large studies are designed to evaluate an individual antiarrhythmic agent for a specific arrhythmia. Controlled, comparison trials of antiarrhythmic agents in children are virtually nonexistent. Ideally, controlled clinical trials are used to develop clinical guidelines; however, in this situation, most data and information must be obtained from case series of children treated. Although the results from these type of studies may be useful in developing guidelines for the optimal use of these agents, controlled trials are required for establishing standard treatment guidelines for all patients.

DATA SYNTHESIS

Despite limited scientific evaluation of conventional agents in the treatment of WPW and AVNRT in children, they continue to be used as standard of care. Most information regarding the use of conventional agents in children has been extrapolated from the adult literature. Little justification for the use of agents or dosing in children is available. Controlled trials regarding the use of new antiarrhythmic agents (propafenone, amiodarone, flecainide) are available; however, the variance in dosing schemes, presence of structural heart disease, and patient age make the development of recommendations difficult.

CONCLUSIONS

Because of greater clinical experience with these conventional antiarrhythmic agents, they continue to be first-line therapy in the management of most supraventricular tachycardia (SVT) in children. The management of SVT in children with WPW syndrome should begin with the use of a beta-blocker with the addition of digoxin or procainamide for treatment failures. The use of digoxin monotherapy, although frequently used by many practitioners in infants and children with WPW, cannot be recommended. For failures to conventional agents, flecainide is the preferred agent, while therapy with propafenone, amiodarone, and sotalol remains to be elucidated. The management of AVRNT is similar to that of WPW; however, digoxin is the agent of first choice. Trials of beta-blockers and procainamide should follow for treatment failures with flecainide again being the preferred "newer" antiarrhythmic for use in resistant cases. Additional well-designed, controlled trials are needed to further evaluate the comparative efficacy of antiarrhythmics in the management of WPW and AVNRT in children, as well as to evaluate dosing and toxicity in various age groups.

Clinical usefulness of slow pathway ablation in patients with both paroxysmal atrioventricular nodal reentrant tachycardia and atrial fibrillation

Some patients with atrioventricular (AV) node reentrant tachycardia (AVN RT) also presented with atrial fibrillation (AF). In this study we demonstrate that slow pathway ablation is able to suppress both AVN RT and AF in subjects without structural heart abnormalities, whereas in patients with structural heart abnormalities after ablation AF frequently recurs.

Atrial electrophysiological features in patients with Wolff-Parkinson-White and atrial fibrillation: absence of rate adaptation of intraatrial conduction time parameters

Clinical electrophysiology has not yet clearly defined atrial features that can predict spontaneous occurrence of atrial fibrillation (AF). The aim of this work was to identify atrial electrophysiological features that can distinguish Wolff-Parkinson-White patients with spontaneous AF from those without this arrhythmia. Sixty-nine patients with Wolff-Parkinson-White were divided into three groups: group I (16 patients) with spontaneous AF; group II (35 patients) with reciprocating tachycardia but not AF; and group III (18 patients) asymptomatic without documented arrhythmias. Atrial effective refractory periods (ERPs) and intraatrial conduction times in response to premature extrastimuli were analyzed. The latter were evaluated as the A1A2 interval minus the correspondent S1S2 interval (A1A2-S1S2), S1A2 and the interval A1A2 following the shortest S1S2 producing atrial activation (FRP'). All the parameters have been evaluated in two atrial sites and at two atrial pacing cycle lengths (600 and 400 ms). For all the parameters, the difference ("gradient") was calculated between the values of the same parameter measured at the atrial pacing cycle length of 600 ms and that found at the atrial pacing cycle length of 400 ms in the same recording site in each patient was calculated. Atrial ERP did not differ significantly in the three groups. Intraatrial conduction parameters, evaluated in the high right atrium (HRA), were longer when measured at an atrial pacing of 400 ms and showed a lack of rate adaptation in patients with spontaneous AF. In group I patients in particular, FRP' became longer with the increase of atrial rate, while in groups 2 and 3, it usually shortened. The mean gradient of HRA FRP' was -15.0 +/- 19 ms in group I as compared to 5.7 +/- 13 ms in group II and 6.4 +/- 13 ms in group III (P < 0.001); sensitivity, specificity, and negative predictive value of a negative gradient in the identification of patients with spontaneous AF, were, respectively, 83%, 75%, and 93%. Patients from groups 2 and 3 did not differ in any of the analyzed parameters. Patients with Wolff-Parkinson-White and spontaneous AF showed prolonged intraatrial conduction times and a different behavior in response to modification of heart rate.

Electrophysiologic aspects of human atrial fibrillation

This article reviews the important developments that have led to current understanding of atrial fibrillation, the data that support its mechanistic dependence on various forms of reentrant excitation, and the resultant electrophysiologic and clinical implications of clinicians' evolving understanding.

Effects of isoflurane on electrophysiological measurements in children with the Wolff-Parkinson-White syndrome

This study was designed to assess the effects of isoflurane (ISO) on the electrophysiological properties of the accessory pathway, atrium, ventricle, and AV node in children with the Wolff-Parkinson-White (WPW) syndrome. The results of programmed electrical stimulation were analyzed in 51 patients (4 months to 17 years of age) with WPW. The study population was divided into two groups. Twenty-seven patients received local anesthesia and intramuscular injection of meperidine, promethazine, and chlorpromazine (MPC group). Twenty-four patients received general anesthesia with ISO inhalation (ISO group). We compared the antegrade effective refractory period of the accessory pathway (antegrade APERP), ventricular effective refractory period (VERP), atrial effective refractory period (AERP), AH interval, and cycle length of circus movement tachycardia (CMT-CL) in 12 pairs of age and sex matched patients selected from the MPC and ISO groups. Of the 12 pairs of age and sex matched patients, antegrade APERP in patients who received ISO (299 +/- 17 ms, mean +/- SEM) was significantly longer as compared with matched patients in the MPC group (262 +/- 5 ms, P < 0.025). The VERP and AERP in patients from the ISO group were significantly prolonged compared with the MPC patients (239 +/- 7 vs 210 +/- 8 ms, P < 0.025, and 228 +/- 11 vs 180 +/- 6 ms, P < 0.01, respectively). There was no significant difference in the AH interval or CMT-CL between the two subgroups. Thus, ISO prolongs the antegrade APERPs as well as the effective refractory periods of atrial and ventricular muscle in children with WPW, while the AH interval and CMT-CL appear to be unaffected. Care must be taken in interpreting measurements of the antegrade APERP made in patients under general anesthesia for RF ablation of accessory pathways.

Longitudinal clinical and electrophysiological assessment of patients with symptomatic Wolff-Parkinson-White syndrome and atrioventricular node reentrant tachycardia

BACKGROUND

Functional changes of the accessory AV pathways and dual AV node pathways are very important for patients with Wolff-Parkinson-White syndrome or AV node reentrant tachycardia who refuse to receive long-term medication or radiofrequency catheter ablation. However, no studies of serial clinical and electrophysiological characteristics in these patients have been performed.

METHODS AND RESULTS

One hundred thirteen patients with Wolff-Parkinson-White syndrome or AV node reentrant tachycardia were included in this study. The first and second follow-up electrophysiological studies were performed in years 5 and 10 after the baseline study, respectively. Conduction properties of the accessory pathways became poor over time. After a mean follow-up period of 9 +/- 1 years, antegrade ventricular preexcitation and retrograde accessory pathway conduction disappeared in 22.5% and 7.8% (P < .01), respectively; dual AV node pathway physiology persisted and retrograde fast pathway disappeared in 10.8% of the patients. Baseline conduction properties of the antegrade and retrograde accessory pathways and the retrograde fast pathway independently predicted late loss of conduction. Spontaneous disappearance of the original tachyarrhythmias occurred in 10.3% of all patients, and newly developed tachyarrhythmias in 15.2%. The incidence (38.5%) of newly developed atrial fibrillation was significantly higher in patients with manifest accessory pathways. Furthermore, symptom scores and attack frequency increased significantly over time in the patients with accessory pathways and AV node reentrant tachycardia.

CONCLUSIONS

Disappearance of the original tachycardia and changing patterns of tachycardia, also with an increase in symptom scores and attack frequency, suggested that a detailed evaluation of these events is important and early intervention with radiofrequency ablation would be helpful.

Electrocardiographic and electrophysiologic characteristics of anteroseptal, midseptal, and para-Hisian accessory pathways. Implication for radiofrequency catheter ablation

STUDY OBJECTIVE

To investigate the ECG characteristics, the electrophysiologic properties, and an effective radiofrequency catheter ablation technique in patients with septal accessory pathways.

PATIENTS

Forty-six consecutive subjects with septal accessory pathways located in the anteroseptal, midseptal, and para-Hisian areas.

DESIGN AND INTERVENTIONS

ECGs obtained during sinus rhythm and orthodromic tachycardia, conduction properties obtained from electrophysiologic study, and results of two different ablation techniques were analyzed.

MEASUREMENTS AND RESULTS

(1) Twenty-four (52.2%) had manifest preexcitation and 15 (32.6%) had multiple accessory pathways; (2) midseptal pathways could be differentiated from anteroseptal and para-Hisian pathways by a negative delta wave in lead III and a biphasic delta wave in lead aVF during sinus rhythm, and a negative retrograde P wave in two inferior leads during orthodromic tachycardia; (2) midseptal pathways had better antegrade conduction properties and a significantly higher incidence (61.5%) of inducible atrial fibrillation; (4) radiofrequency catheter ablation using lower energy (20+/-6 W) had a comparable effect to ablation using higher energy (36+/-5 W), but without impairment of atrioventricular (AV) node conduction or development of AV block; and (5) during the follow-up period of 26+/-14 months (range, 5 to 54 months), three (6.5%) patients had recurrence.

CONCLUSIONS

Midseptal accessory pathways had ECG and electrophysiologic characteristics that were distinctive from those of anteroseptal and para-Hisian pathways. Catheter ablation of these septal pathways using low radiofrequency energy was safe and effective.

Augmented sympathoadrenal activity during treadmill exercise in patients with Wolff-Parkinson-White syndrome and atrial fibrillation

It is believed that reciprocating tachycardia and accessory pathways play important roles in atrial fibrillation (AF) in patients with Wolff-Parkinson-White (WPW) syndrome. However, the mechanism by which AF occurs is not yet fully understood. This study was performed to evaluate the contribution of sympathoadrenal activity to the onset of AF in patients with WPW syndrome. Symptom-limited treadmill exercise testing was performed and plasma norepinephrine and epinephrine concentrations were measured simultaneously in 27 patients with WPW syndrome and 20 control subjects. In 13 patients with WPW syndrome and AF, plasma norepinephrine and epinephrine concentrations increased to 3.69 +/- 2.44 and 0.76 +/- 0.69 ng/ml at maximum exercise, respectively. These values were significantly higher (p < 0.001) than those in control subjects and in patients without AF. Pretreatment with 0.2 mg/kg of propranolol significantly reduced the incidence of exercise-induced atrial premature complexes (chi 2 = 7.33, p < 0.05). With oral beta-blockade for an average of 22.8 months, the incidence of AF decreased significantly from 1.77 +/- 0.53/patient per year to 0.33 +/- 0.57/patient per year (p < 0.001). Augmented sympathoadrenal activity in patients with WPW syndrome may contribute to AF.

Age- and anesthesia-related changes in accessory pathway conduction in children with Wolff-Parkinson-White syndrome

The anterograde effective refractory period of the accessory pathway is age-dependent in pediatric patients with the WPW syndrome. Thus, age should be considered when developing electrophysiologic criteria for the risk of hypotensive arrhythmias in these patients. In addition, general anesthesia must also be considered in interpreting age-related changes in the anterograde APERP, especially in children.

Aborted sudden death in the Wolff-Parkinson-White syndrome

In a population of 690 patients with Wolff-Parkinson-White (WPW) syndrome referred to our hospital from January 1979 to February 1995, 15 patients (2.2%) had an aborted sudden death out of the hospital. This retrospective study examines their clinical and electrophysiologic characteristics. Gender, accessory pathway localization, and presence of multiple accessory pathways were compared between patients with and without spontaneous ventricular fibrillation (VF). Whereas gender and the presence of multiple accessory pathways did not significantly differ between both groups, septally located pathways occurred significantly more often in the VF group. In patients with aborted sudden death, spontaneous VF was found significantly more often in men (13 of 15). VF was the first manifestation of the WPW syndrome in 8 patients. The remaining 7 patients had documented episodes of atrial fibrillation, circus movement tachycardia, or both (n = 2). Ten of the 15 patients were exercising or under emotional stress at the time of aborted sudden death. Only 1 patient had 2 accessory pathways. The location of the accessory pathway was septal (midseptal or posteroseptal) in 11 patients, left lateral in 4, and right lateral in 1).