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

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.

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.

Risk factors for atrioventricular tachycardia degenerating to atrial flutter/fibrillation in the young with Wolff-Parkinson-White

BACKGROUND

Atrioventricular reciprocating tachycardia (AVRT) is common in patients (pts) with Wolff-Parkinson-White (WPW) syndrome but atrial flutter/fibrillation (AF) with rapid ventricular response (RVR) is rare. Although AF occurs in 18% of adult WPW pts, its incidence in children is unknown. We sought to determine risk factors for AVRT spontaneously degenerating to AF during electrophysiologic studies (EPS) in children with WPW.

METHODS

This was a retrospective study of children with WPW referred for accessory pathway (AP) ablation without clinical AF. Standard electrophysiologic protocols were performed to induce AVRT. To determine if AF degeneration was associated with patient characteristics, 2-sample t-tests, Chi-square, and Fisher's exact were used.

RESULTS

There were 53 (31 males) WPW pts studied. During EPS, AVRT degenerated to AF in 27/53 (51%). RVR was seen in 18/27 (67%) patients. The ventricular cycle length (CL) during AF was shorter with RVR (211 + 24 ms) than without (313 + 65 ms) (P = 0.01). AF occurred more commonly among patients with right anterior AP (P = 0.05). Patient gender, age, height, weight, body surface area, persistence of preexcitation on exercise testing, baseline CL, AVRT conduction, and AP number were not significant AF determinants. The AVRT CL was significantly shorter in patients with (265.2 + 41.5 ms) versus those without (308 + 59 ms) AF (P = 0.01). Preliminary data suggest that AP location may be related to patient ethnicity.

CONCLUSION

AF with RVR occurred following AVRT induction during EPS in 34% of our WPW patients, typically associated with right-sided AP locations. Time intervals for RVR to degenerate into ventricular fibrillation and lead to SCD are yet to be determined.