Atrioventricular node reentrant tachycardia in patients with a prolonged AH interval during sinus rhythm: clinical features, electrophysiologic characteristics and results of radiofrequency ablation

Impairment of the antegrade fast pathway in patients with atrioventricular nodal reentrant tachycardia can be functional and treated by slow pathway ablation: a case report study

Background

Slow pathway (SP) ablation is considered to be the standard treatment for symptomatic atrioventricular nodal reentrant tachycardia (AVNRT). This may be challenging in patients with documented PR interval prolongation due to the potential increased risk of atrioventricular (AV) block in some patients.

Case Summary

We report two cases of symptomatic recurrent AVNRT refractory to medical treatment with significant baseline PR interval prolongation (304 ms and 336 ms). In both of these cases, the baseline electrophysiological study demonstrated dual AV nodal physiology with a functional antegrade fast pathway and evidence for transient normalization of the PR interval. Slow/fast AVNRT was confirmed in both cases. Slow pathway ablation was successfully performed resulting in normalization of the PR interval to 144 ms and 168 ms with no evidence of AV block. After a mean follow-up of 30 months, the patients remained asymptomatic with normal PR interval, no recurrence of AVNRT, and no documentation of high degree AV block.

Discussion

Our cases illustrate a common dilemma when dealing with patients with AVNRT and prolonged baseline interval. We show that SP ablation is feasible and safe as long as a preserved antegrade FP is present.

Catheter ablation for supraventricular tachycardias: contemporary issues

The treatment of cardiac arrhythmias has evolved significantly over the last 30 years. Understanding of arrhythmia mechanisms has led to pharmacologic therapies, surgical interventions and the widely used percutaneous catheter ablation techniques. The focus of this review is centered on the current catheter ablation therapies available for supraventricular tachycardia. We will discuss current management strategies including challenges when considering catheter ablation therapy for management of supraventricular tachycardias: atrioventricular nodal reentrant tachycardia, atrioventricular reentrant tachycardia utilizing an accessory pathway, atrial tachycardia and atrial flutter. Selected contemporary issues related to supraventricular tachycardia physiology, ablation approaches and ablation outcomes and complications will be discussed. Future goals for electrophysiologists are to continue to improve procedural safety and efficiency, while maintaining the impressive success rates that have been achieved.

Catheter ablation of atrioventricular nodal reentrant tachycardia in patients with a prolonged PR interval at sinus rhythm

Radiofrequency transcatheter ablation is an effective and safe treatment for atrioventricular node reentry tachycardia. Slow pathway ablation is considered the ablative technique of choice, but when atrioventricular nodal reentrant tachycardia is associated with a prolonged PR interval at sinus rhythm, a higher risk of delayed atrioventricular (AV) block has been reported. Studies on the subject are few, enrolling low numbers of patients with variable selection criteria and producing different results. Hence, optimal ablation strategy remains controversial. The aim of this study is to review the available knowledge on the topic. Experience from our centers is also briefly reported.

Fast pathway ablation using cryotherapy for a patient with a long PR interval in sinus rhythm and AVNRT

A 53-year-old man with previous aortic valve surgery presented with paroxysmal narrow complex tachycardia, induced by exercise. His PR interval was greater than 400 ms when in sinus rhythm and atrioventricular nodal reentry tachycardia (AVNRT) was diagnosed with invasive electrophysiological studies. Single echoes were repeatedly inducible with single-paced extrastimuli. Cryotherapy was then used to ablate the fast pathway using single echoes to monitor anterograde slow pathway and retrograde fast pathway function during ablation.

Long-term follow-up of patients with P-R prolongation after catheter ablation of slow pathway for atrioventricular node re-entrant tachycardia

BACKGROUND

Long-term impact of interval between P wave and R wave (P-R) prolongation on prognosis of patients with successful catheter ablation of slow atrioventricular nodal pathway was investigated.

METHODS

Among 436 patients undergoing slow-pathway ablation for atrioventricular node re-entrant tachycardia (AVNRT), 17 (3.9%) experienced permanent P-R prolongation. Ablation target sites where conduction block was induced were located in mid- or anteroseptum. Fast junctional rhythm with ventriculoatrial conduction block was observed in eight patients immediately before atrioventricular block.

RESULTS

Antegrade slow-pathway conduction was eliminated in 16 patients, and retrograde fast- and slow-pathway conduction was abolished in all patients. There was no recurrence of AVNRT after an average of 38 +/- 12 month follow-up. There was no deterioration of atrioventricular block in these patients. Average PR interval prior to hospital discharge and at the end of follow-up was 0.24 +/- 0.02 sec and 0.23 +/- 0.02 sec, respectively (p >0.05). Left ventricular ejection fraction remained unchanged in these patients (p >0.05).

CONCLUSIONS

Radiofrequency catheter ablation of slow pathway for AVNRT is associated with a small risk of atrioventricular block. PR prolongation after successful slow-pathway ablation is associated with benign prognosis.