Electrophysiological features of orthodromic atrioventricular reentry tachycardia in patients with wolff-Parkinson-white syndrome and atrial fibrillation

Electrocardiographic patterns of ventricular pre-excitation in dogs with right-sided accessory pathways

INTRODUCTION

The aim of the study was to describe the electrocardiographic features of ventricular pre-excitation (VPE) patterns characterized by the presence of delta (δ) wave, short P-δQRS interval, wide δQRS complexes in dogs with right-sided accessory pathways.

ANIMALS, MATERIALS AND METHODS

Twenty-six dogs with a confirmed accessory pathways (AP) via electrophysiological mapping were included. All dogs underwent a complete physical examination, 12-lead ECG, thoracic radiography, echocardiographic examination and electrophysiologic mapping. The AP were located in the following regions: right anterior, right posteroseptal, right posterior. The following parameters were determined: P-δQRS interval, δQRS duration, δQRS axis, δQRS morphology, δ-wave polarity, Q-wave, R-wave, R'-wave, S-wave amplitude, and R/S ratio.

RESULTS

In lead II, the median δQRS complex duration was 82.4 (IQR 7.2) and the median P-δQRS interval duration was 54.6 (IQR 4.2) msec. The median δQRS complex axis in the frontal plane was: + 68° (IQR 52.5) for right anterior APs, - 24 ° (IQR 24) for right postero-septal APs, - 43.5 ° (IQR 27.25) for right posterior APs (P = 0.007). In lead II, the polarity of the δ wave was positive in 5/5 right anterior APs and negative in 7/11 postero-septal APs and 8/10 in right posterior APs. In precordial leads of all dogs, R/S was ≤ 1 in V1 and > 1 in all leads from V2 to V6.

CONCLUSION

Surface electrocardiogram can be used to distinguish right anterior APs from right posterior and right postero-septal ahead of an invasive electrophysiological study.

Radiofrequency catheter ablation of accessory pathways in the dog: the Italian experience (2008-2016)

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.

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.

Electrophysiological characteristics of orthodromic reentrant tachycardia in patients with Wolf-Parkinson-White syndrome and atrial fibrillation

The aim of this study was to evaluate differences in the electrophysiological features of atrioventricular reentrant tachycardia (AVRT) in patients with Wolf-Parkinson-White syndrome (WPW) associated with or without atrial fibrillation (AF). We included 119 patients with WPW and orthodromic AVRT during electrophysiological study. The patients were divided into two groups; group I with documented episodes of AF (n=39, mean age 33.3+/-11.5 years), and group II without AF (n=80, mean age 35.3+/-13.8). We compared parameters of accessory pathway (AP), atrium and ventricle between two groups and found no significant difference. We next assessed the electrophysiological parameters of AVRT in both groups in terms of conduction times and atrioventricular (AV) activation relations. A significant negative correlation was found in group II between anterograde and retrograde conduction times measured as AV and VA intervals at the site of the earliest atrial activation (r=-0.43, P<0.0001), whereas no significant correlation was seen in group I (r=-0.29, P=0.1). Comparative analysis between two groups revealed significant difference in A-V/V-V index (P=0.05). These data suggest the presence of different electrophysiological properties of AP during AVRT in only few respects in patients with AF compared to those without it.

[Recurrence of atrial fibrillation after successful radiofrequency catheter ablation of accessory pathway in patients with Wolff-Parkinson-White syndrome]

INTRODUCTION

Paroxysmal atrial fibrillation (AF) occurs in 11.5-39% of the patients with Wolff-Parkinson-White (WPW) syndrome and frequently, but not always, disappears after successful accessory pathway (AP) ablation.

OBJECTIVE

To determine AF recurrence rate, time to AF recurrence and predictors of AF recurrence after radiofrequency (RF) catheter-ablation of AP in WPW-patients with AF.

METHODS

Data from 245 consecutive patients with WPW-syndrome who underwent RF catheter-ablation of AP were analysed. A total of 52 patients (43 men, mean age: 42.5 +/- 14.1 years) with preablation history of spontaneous AF were followed up after definitive AP ablation. At baseline, structural heart disease and comorbidities were diagnosed in 19.2% and 21.2% of the patients, respectively.

RESULTS

During the follow-up of 5.2-3.7 years, 3 patients (5.7%) died; one of these patients, previously known for recurrent AF, died from ischaemic stroke. Symptomatic recurrence of AF was detected in 9 of 52 patients (17.3%). In 66.7% of these patients, AF recurrence was identified in the first year following the procedure. Kaplan-Meier analysis demonstrated that freedom from recurrent AF after 3 months was 94.2%, after 1 year 87.5% and after 4 years 84.3%. Univariate analysis showed that older age (p = 0.023), presence of structural heart disease (p = 0.05) and dilated left atrium (p = 0.013) were significantly related to AF recurrence. However, using multivariate Cox regression, older age was the only independent predictor of AF recurrence (HR = 2.44 for every life decade; p = 0.006). Analysis of ROC curves showed that, after the age of 36, the risk of AF recurrence abruptly increased.

CONCLUSION

Symptomatic recurrence of AF was detected in 17% of WPW-patients after definite RF ablation of AP. The time-dependent occurrence of AF recurrences and age-dependent increase in the rate of AF recurrence were identified. Closer follow-up and/or extension of drug therapy in older patients, at least in the first year after the procedure, seem prudent.

Internal Atrial and Ventricular Defibrillation During Electrophysiology Procedures

Over the last twenty years internal defibrillation has evolved from an experimental technique into an important adjunctive procedure in the electrophysiology laboratory. Internal deflbrillation is used for treating persistent atrial fibrillation and refractory ventricular arrhythmias. Atrial defibrillation can be performed with several electrode configurations but generally shocks from 1 to 50 joules are delivered between electrodes placed in the coronary sinus and lateral wall of the right atrium. Ventricular defibrillation is usually performed with electrodes in the right ventricle and superior vena cava, although "unipolar" configurations with an internal ventricular electrode and a skin electrode can be used. Currently, internal deflbrillation can be required in 5-10% of cases within the electrophysiology laboratory and will become more commonly used as electrophysiologists perform more complex catheter ablation procedures.