Pre-excited RR intervals during atrial fibrillation in the Wolff-Parkinson-White syndrome: influence of the atrioventricular node refractory period

Old stuff still trending: use of propafenone as a safety net until catheter ablation in a patient with documented pre-excited atrial fibrillation and Wolff-Parkinson-White syndrome - a classic case report

BACKGROUND

Atrial fibrillation in Wolff-Parkinson-White syndrome may result in life-threateningly rapid antegrade conduction over a bypass tract, manifested by an irregular broad-complex (pre-excited) tachycardia that can degenerate to ventricular fibrillation. The shortest pre-excited RR interval below 250 ms during atrial fibrillation (AF) predicts increased risk of sudden cardiac death.

CASE SUMMARY

We report a case of a 43-year-old man with unremarkable cardiac history who presented due to sudden-onset feeling of palpitations and pre-syncope after strenuous lifting. Electrocardiography depicted fast pre-excited AF. The shortest pre-excited RR interval was estimated at 160 ms, indicating an accessory pathway (AP) with short antegrade refractory period at risk for mediating sudden cardiac death. Direct current cardioversion restored sinus rhythm unravelling delta waves. The patient was put on propafenone 450 mg/day having an uneventful clinical course. On Day 10 post-admission, electrophysiological study induced rapid AF but the shortest pre-excited RR interval was substantially increased to 264 ms. A left anterolateral AP was ablated. The patient remained symptom free until his latest follow-up in the 3rd-month post-ablation without manifest pre-excitation on the surface electrocardiogram.

DISCUSSION

Treatment options of pre-excited AF include anti-arrhythmic agents but mainly electrical cardioversion. Cardioversion can safely restore sinus rhythm, while use of anti-arrhythmics often requires intensive care unit monitoring due to the risk of QT prolongation. Catheter ablation is the mainstay of therapy for symptomatic patients. Our rare report highlights the direct impact of propafenone on prolonging the refractoriness of the AP, effectively and safely, and reappraises propafenone's worthiness as a protective measure following pre-excited AF episode until ablation.

Endoscopy-assisted radiofrequency ablation around the coronary sinus ostium in dogs: its effects on atrioventricular nodal properties and ventricular response during atrial fibrillation

INTRODUCTION

Radiofrequency ablation of the slow pathway can prolong atrioventricular (AV) nodal properties and RR intervals during atrial fibrillation (AF) in many patients with AV nodal reentrant tachycardia. However, it is not well elucidated whether these changes are related to the presence of dual AV nodal pathway physiology. The aim of this study was to evaluate changes of AV nodal properties and RR intervals during AF caused by ablation of two specific areas in dogs.

METHODS AND RESULTS

Assisted by fiberoptic endoscopy, linear lesions were created between the coronary sinus ostium and tricuspid valve annulus (area 1) or posterior to the ostium (area 2) in 15 dogs. Three additional dogs served as controls. The measurements were made under autonomic blockade. Catheter ablation could be assisted in all dogs by means of endoscopy. Linear lesions were confirmed at autopsy. AV nodal parameters and RR intervals showed no overall changes. Individual data showed that ablation of area 1 resulted in modification of AV nodal properties in 54.5% (facilitation in 36.3% and inhibition in 18.2%), whereas ablation of area 2 induced changes in 50% (facilitation in 10% and inhibition in 40%). The RR intervals were shortened in 33.3% and 20% and prolonged in 44.5% and 40% after ablation of areas 1 and 2, respectively. The RR intervals during AF correlated well with the Wenckebach cycle length and the AV node functional refractory period before and after ablation (r = 0.78 to 0.94, P < 0.01 for each).

CONCLUSIONS

Ablation of the two specific areas around the coronary sinus ostium was equally effective in modifying AV nodal properties and the ventricular response during AF without dual AV nodal pathway physiology. The ventricular rate to AF after ablation correlated well with the residual AV nodal properties.

Radiofrequency ablation for the fast pathway of atrioventricular node reentry. Evidence for partial damage to the fast and lower common pathways

Radiofrequency ablation was attempted in a 30-year-old woman with atrioventricular (AV) node reentry of the common variety. Energy was delivered to ablate a fast pathway. After energy delivery, the atrio-His interval prolonged following transient AV node block. Retrograde conduction was no longer present. However, dual AV nodal physiology and AV node reentry with similar retrograde atrial activation sequence could be shown post-ablation. These observations suggest that both fast and lower common pathways were partially damaged by ablation.

Atrioventricular node re-entry of the common variety. Unusual location for the fast pathway

Radiofrequency ablation was attempted in a 17-year-old man with atrioventricular node re-entry of the common variety. Energy was delivered to three sites around the ostium of the coronary sinus. The third attempt resulted in a sudden increase in AH interval with loss of retrograde conduction. The arrhythmia was no longer inducible. These observations may suggest the unusual location of the fast pathway.

Effect of verapamil on an accessory pathway manifesting as "fatigue phenomenon" in Wolff-Parkinson-White syndrome

Electrophysiologic study was performed in a 52-year-old man with type A ventricular preexcitation. An accessory atrioventricular pathway with no ventriculoatrial conduction was localized to the posteroseptal region. "Fatigue phenomenon," defined as suppression of atrioventricular conduction following rapid pacing, was observed to be provoked by atrial pacing in a rate- and duration-dependent manner. Administration of 5 mg of intravenous verapamil during sinus rhythm abolished the delta waves. These observations may indicate that pathologic changes in the accessory pathway are responsible for these phenomena.