Ventricular-triggered atrial pacing: A new maneuver for slow-fast atrioventricular nodal reentrant tachycardia

BACKGROUND

Atrioventricular (AV) node duality is suggested by several electrophysiological findings, none of which are strong predictors of AV nodal reentrant tachycardia (AVNRT).

OBJECTIVE

The purpose of this study was to propose a novel maneuver to study conduction over the AV node and attempt to induce slow-fast AVNRT.

METHODS

Ventricular-triggered atrial pacing (VTAP) with decremental VA delay was carried out in 36 consecutive patients with slow-fast AVNRT and in 21 controls after conventional electrophysiology study. Maneuvers were repeated after ablation in patients with AVNRT.

RESULTS

VTAP resulted in a hysteretic conduction curve in 21 of 36 patients (58%) in the AVNRT group but only 4 of 21 patients (19%) in the control group (sensitivity 58; specificity 81%). This finding demonstrates sustained conduction in a slow conducting pathway and concealed retrograde conduction over a fast pathway. VTAP resulted in AVNRT induction in 15 of 25 inducible patients at baseline (60%), 4 of which were not inducible with incremental pacing or programmed atrial stimulation. VTAP resulting in a suspended p wave had 51% (39%-64%) sensitivity and 100% (89%-100%) specificity for predicting noninducibility in a given autonomic state.

CONCLUSION

VTAP is useful in patients with suspected slow-fast AVNRT. A hysteretic conduction curve demonstrates sustained conduction over a slow pathway and concealed retrograde conduction through the fast pathway, a finding in favor of slow-fast AVNRT. VTAP may facilitate AVNRT induction and proves to be an interesting complement to classic maneuvers. A suspended p-wave response specifically predicts noninducibility of slow-fast AVNRT in a given autonomic state, providing an interesting surrogate to noninducibility as a procedural end point.

A simplified approach for evaluating sustained slow pathway conduction for diagnosis and treatment of atrioventricular nodal reentry tachycardia in children and adults

PURPOSE

During incremental atrial pacing in patients with atrioventricular nodal reentrant tachycardia, the PR interval often exceeds the RR interval (PR > RR) during stable 1:1 AV conduction. However, the PR/RR ratio has never been evaluated in a large group of patients with pacing from the proximal coronary sinus and after isoproterenol challenge. Our study validates new site of pacing and easier method of identification of PR > RR.

MATERIAL AND METHODS

A prospective protocol of incremental atrial pacing from the proximal coronary sinus was carried out in 398 patients (AVNRT-228 and control-170). The maximum stimulus to the Q wave interval (S-Q = PR), SS interval (S-S), and Q-Q (RR) interval were measured at baseline and 10 min after successful slow pathway ablation and after isoproterenol challenge (obligatory).

RESULTS

The mean maximum PR/RR ratios at baseline were 1.17 ± 0.24 and 0.82 ± 0.13 (p < 0.00001) in the AVNRT and controls respectively. There were no PR/RR ratios ≥1 at baseline and after isoproterenol challenge in 12.3% of the AVNRT group and in 95.9% of the control group (p < 0.0001). PR/RR ratios ≥1 were absent in 98% of AVNRT cases after slow pathway ablation/modification in children and 99% of such cases in adults (P = NS). The diagnostic performance of PR/RR ratio evaluation before and after isoproterenol challenge had the highest diagnostic performance for AVNRT with PR/RR > = 1 (sensitivity: 88%, specificity: 96%, PPV-97%, NPV-85%).

CONCLUSIONS

The PR/RR ratio is a simple tool for slow pathway substrate and AVNRT evaluation. Eliminating PR/RR ratios ≥1 may serve as a surrogate endpoint for slow pathway ablation in children and adults with AVNRT.

Ablation of atrioventricular nodal reentrant tachycardia using remote magnetic guidance (stereotaxis) requires lower temperature and power settings because of improved local contact

INTRODUCTION AND OBJECTIVES

The Stereotaxis(R) remote magnetic navigation system provides a new approach to ablation that could increase catheter stability. The aim was to determine whether improved tissue contact necessitates a change in traditional radiofrequency ablation parameters.

METHODS

The study compared ablation of atrioventricular nodal reentrant tachycardia (AVNRT) using remote navigation (4-mm catheter) in 19 patients with conventional ablation in 18 patients (4-mm catheter, temperature 60-65 degrees C, power 50 W). The radiofrequency energy needed to ensure that no more than a single nodal echo beat could be induced was measured.

RESULTS

Charring was observed with traditional parameters on the first applications of the remotely navigated catheter. Hence, the energy was subsequently reduced (to 50 degrees C and 40 W). There was no difference in the number of applications between remote navigation and conventional groups (median: 6 vs. 8.5; interquartile range [IQR]: 11 vs. 9). Applications lasting <or=5 s were usually due to catheter dislodgment. Only four patients in the remote group had applications <or=5 s compared with 11 in the conventional group (P=.041). Ablation using remote navigation was equally effective and required lower temperatures and powers (mean+/-SD temperature: 46+/-2 degrees C vs. 50+/-4 degrees C, P< .001; median [IQR] power: 29 [14] W vs. 50 [7] W, P< .001), with no difference in total energy delivered. With remote navigation, the range of impedance values between applications was less (mean+/-SD: 10.4+/-7.6 Omega vs. 19.3+/-15.4 Omega; P=.035) and the temperature variation tended to be less, suggesting greater stability between applications. There were no complications.

CONCLUSIONS

In this initial series, remote magnetic navigation was safe and effective in AVNRT ablation. Improved tissue contact reduced catheter dislodgment and necessitated a reduction in radiofrequency energy to avoid charring.

[Update on arrhythmias and cardiac electrophysiology]

This article contains a review of the most important developments in clinical arrhythmology and interventional cardiac electrophysiology that have been reported during the past year. Special emphasis has been placed on clinical conditions that are most prevalent in the general population as well as on progress that has been achieved using the main therapeutic approaches, whether pharmacologic or interventional.