Use of adenosine to identify patients at risk for recurrence of accessory pathway conduction after initially successful radiofrequency catheter ablation

Early dose of Adenosine, postRadiofrequency abLation of accessory pathwaY in determining acute procedural success (EARLY study)

INTRODUCTION

Post ablation of the accessory pathway (AP), the patient is observed in the catheterization laboratory for a variable period for resumption of pathway conduction. Aim of the study was to determine whether the administration of intravenous adenosine at 10 min after ablation of AP would have the same diagnostic accuracy as waiting for 30 min in predicting the resumption of AP conduction.

METHODS

This was a prospective interventional study conducted in two centers. Post ablation of the AP, intravenous adenosine was administered at 10 min to look for dormant pathway conduction. The response was recorded as positive (presence of pathway conduction), negative (absence), or indeterminate (not able to demonstrate AV and VA block and inability to ascertain AP conduction).

RESULTS

The study included 110 procedures performed in 109 patients. Adenosine administration at 10 min showed positive result in 3 cases (2.7%), negative result in 99 cases (90%) and indeterminate result in 8 cases (7.3%). Reconnection of accessory pathway at 30 min postablation was seen in 8 cases (7.3%). Of these 8 cases, 10 min adenosine administration showed positive test in 3 patients and negative test in 5 patients. Adenosine test at 10 min has a sensitivity, specificity, positive predictive value, and negative predictive value of 37.5%, 100%, 100%, and 94.9% in identifying the recurrence of accessory pathway conduction at 30 min, respectively.

CONCLUSION

Absence of pathway conduction on administration of adenosine 10 min postablation does not help predict the absence of resumption of conduction thereafter.

Mechanisms and clinical significance of adenosine-induced dormant accessory pathway conduction after catheter ablation

BACKGROUND

Adenosine can unmask dormant pulmonary vein conduction after isolation. The role of adenosine in uncovering dormant accessory pathway (AP) conduction after AP ablation is unknown.

METHODS AND RESULTS

We evaluated 109 consecutive patients (age, 41 ± 28 years; 62 [57%] men) who were administered adenosine after successful AP ablation. Dormant AP conduction was defined as adenosine-induced recurrent AP conduction, as demonstrated by recurrent preexcitation or change in retrograde ventriculoatrial activation patterns. Dormant AP conduction was identified in 13 (12%) patients. Adenosine led to transient retrograde AP conduction in 6 patients and transient anterograde AP conduction in 8 patients. In all these cases, adenosine-induced AP conduction occurred during the bradycardia phase of adenosine effect and resulted in dormant AP conduction times shorter than atrioventricular nodal conduction times before adenosine administration. On the basis of analysis of timing of occurrence of dormant AP conduction, the mechanism of adenosine-induced AP conduction was determined to be caused by AP excitability recovery in ≥ 12 (92%) cases. The presence of dormant AP conduction was a significant predictor of chronic recurrent AP conduction requiring repeat ablation (odds ratio, 8.54; 95% confidence interval, 1.09-66.9; P=0.041).

CONCLUSIONS

Adenosine can unmask dormant AP conduction after catheter ablation. Direct effects of adenosine on the AP, possibly via AP membrane potential hyperpolarization, are the dominant mechanism of adenosine-induced AP conduction after ablation. Dormant AP conduction is associated with higher rates of recurrent AP conduction requiring repeat ablation.

High variability of retrograde fast pathway sensitivity to adenosine

BACKGROUND

Adenosine is widely used as a tool to assess the effectiveness of radiofrequency ablation of concealed accessory pathways.

HYPOTHESIS

The goal of this study was to determine the reliability of this test by studying the retrograde fast pathway sensibility in a large patient population with typical atrioventricular (AV) nodal reentry tachycardias. We sought also to determine whether AV nodal properties were predictive of a retrograde fast pathway sensitivity to adenosine.

METHODS

In all, 124 patients with inducible AV nodal reentrant tachycardia were included in this study. All patients received a clinically used standard dose of 12 mg adenosine during ventricular pacing, with 500 ms and a constant ventriculoatrial (VA) conduction via the fast pathway. Electrophysiologic parameters of the AV node were determined in all patients in order to correlate them with the adenosine sensitivity of the retrograde pathway.

RESULTS

In 74 patients, the injection of 12 mg adenosine resulted in a transient VA block, whereas no VA block occurred in the remaining 50 patients. In two patients, concealed accessory pathways were unmasked after the injection of adenosine. The adenosine sensitivity of the retrograde fast pathway was associated with longer retrograde conduction times and cycle lengths during AV nodal reentrant tachycardias.

CONCLUSION

This study shows a high variability of retrograde fast pathway sensitivity to adenosine. Thus, in 40% of patients the lack of VA block after adenosine injection is not specific for persistent accessory pathway function after radiofrequency ablation. Electrophysiologic properties of patients with AV nodal reentrant tachycardias were different in patients with and without adenosine-sensitive retrograde fast pathways, possibly indicating differential patterns of penetration of the retrograde fast pathway into the compact AV node.

The Results of Radiofrequency Catheter Ablation of Supraventricular Tachycardia in Children

BACKGROUND

Radiofrequency (RF) catheter ablation represents a major advance in the management of children with cardiac arrhythmias and has rapidly become the standard of care for the first-ling therapy of supraventricular tachycardias (SVTs). The purpose of this study was to investigate the results of the RF catheter ablation of SVTs in pediatric patients.

METHODS

From December 1989 to August 2005, a total of 228 pediatric patients (age: 9 +/- 7 years, range: 5-18 years; male:female = 117:111) with clinically documented SVT underwent an electrophysiologic study and RF catheter ablation at our institution.

RESULTS

The arrhythmias included atrioventricular reentrant tachycardia (AVRT; n = 140, 61%), atrioventricular nodal reentrant tachycardia (AVNRT; n = 66, 29%), atrial tachycardia (AT; n = 11, 5%), and atrial flutter (AFL; n = 11, 5%). The success rate of the RF catheter ablation was 92% for AVRT, 97% for AVNRT, 82% for AT, and 91% for AFL, respectively. Procedure-related complications were infrequent (8.7%; major complications: high grade AV block (2/231, 0.9%); minor complications: first degree AV block (6/231, 2.6%), reversible brachial plexus injury (2/231, 0.9%), and local hematomas or bruises (10/231, 4.3%)). The recurrence rate was 4.7% (10/212) during a follow-up period of 86 +/- 38 months (0.5-185 months).

CONCLUSIONS

The RF catheter ablation was a safe and effective method to manage children with paroxysmal and incessant tachycardia. The substrates of the arrhythmias differed between the pediatric and adult patients. However, the success rate of the ablation, complications, and recurrence during childhood were similar to those of adults.

Utility of adenosine 5'-triphosphate in predicting early recurrence after successful ablation of manifest accessory pathways

OBJECTIVES

The purpose of this study was to determine whether administration of adenosine 5'-triphosphate (ATP; 20-40 mg) after successful ablation of accessory pathway (AP) with manifest preexcitation is useful for detecting residual conduction and predicting early recurrences.

BACKGROUND

The reported incidence of recurrence of AP conduction after an initially successful procedure is 5% to 10%. Little information on the variables related to early recurrence has been reported.

METHODS

We prospectively used 108 ATP tests on 100 consecutive patients (66 men, mean age 36 +/- 15 years) with manifest preexcitation. Five minutes after successful ablation, intravenous boluses of ATP at increasing doses were injected until the target effect of second- or third-degree AV block or AP conduction was observed.

RESULTS

The effect of ATP was AV block (negative test) in 82 cases (76%), conduction over previously ablated AP (positive test) in 9 cases (8.3%), and no achievement of target effect (nondiagnostic test) in 17 cases (15.7%). Thirteen early recurrences were observed in 12 patients. In all 9 (100%) patients with positive ATP test and in 4 (4.9%) of the 82 patients with negative ATP test, conduction over the AP recurred (relative risk 20; 95% confidence interval 8-53; P < .000001). The diagnostic accuracy of the test (analyzing the target effect) was 95%, sensitivity 69%, specificity 100%, and positive and negative predictive values 100% and 95%, respectively.

CONCLUSIONS

ATP administration after successful ablation of APs has a high predictive value for early recurrence and may help optimize the duration of the ablation procedure.

Variable responsiveness of anterograde and retrograde fast pathway conduction to adenosine in patients with typical AV-nodal reentry tachycardia

Adenosine is known as a substance which depresses predominantly the slow pathway of the av-node. However, the effect of adenosine on the anterograde and retrograde fast pathway (FP) has not been studied in a large patient population. Ninety-one patients with inducible typical av-nodal reentrant tachycardias (AVNRT) were included. The clinically used dosage of 12 mg adenosine was administered subsequently as bolus injection during a constant atrial and ventricular pacing (500 ms) in all patients. Electrophysiological av-nodal parameters were determined. A higher responsiveness of the anterograde compared to the retrograde FP was observed: the majority of patients (76%) blocked anterogradely and 55% blocked retrogradely within the FP after the administration of 12 mg adenosine. Thirty-six percent of all patients revealed a differential behaviour to adenosine. Sixteen percent of all patients were completely resistant to adenosine (P=0.012). Electrophysiological parameters did not predict the responsiveness of the FP to adenosine. In patients with typical AVNRT the anterograde FP shows a higher sensitivity than the retrograde FP to adenosine. This might reflect an anatomical and/or functional distinction between anterograde and retrograde FP. The variable response to adenosine could be due to individual anatomical and electrophysiological heterogenity of the perinodal tissue and the av-node.

Imaging of adenosine bolus transit following intravenous administration: insights into antiarrhythmic efficacy

OBJECTIVE

To study the effects of the site of intravenous injection of adenosine and to assess the site of action of adenosine in the heart by correlating cardiac effects with bolus transit.

METHODS

Ten patients undergoing routine technetium (Tc-99m) gated blood pool ventriculography consented to the coadministration of intravenous adenosine. The dose of adenosine required to produce heart block during sinus rhythm was determined following antecubital vein administration. This dose (6-18 mg) was mixed with Tc-99m and given first into the same antecubital vein (proximal injection) and then repeated into a hand vein (distal injection). The ECG was recorded and the transit of the bolus was imaged using a gamma camera.

RESULTS

Heart block occurred in all 10 patients (second degree in seven, first degree in three) at (mean (SEM)) 17.5 (1.0) seconds after the proximal injection of adenosine. Distal injection produced heart block in six patients (second degree in two, first degree in four) at 21.9 (4.4) seconds (p < 0.01). In eight of 10 patients the electrophysiological effects were less with distal injection. The onset of heart block was close to the time of peak bolus Tc-99m activity in the left ventricle. Peak bolus activity was delayed (by about three seconds) and the duration of bolus activity in the left ventricle was increased with distal injection compared with proximal injection, at 17.2 (4.2) v 9.2 (3.1) seconds, p < 0.01.

CONCLUSIONS

The lesser electrophysiological effects of adenosine following distal intravenous injections were associated with delay in transit time and dispersion of the bolus. The correlation of adenosine induced heart block with bolus activity in the left heart indicated dependence on coronary arterial delivery of adenosine to the atrioventricular node.

Differential effect of adenosine on anterograde and retrograde fast pathway conduction in patients with atrioventricular nodal reentrant tachycardia

INTRODUCTION

Several studies have shown that the fast pathway is more responsive to adenosine than the slow pathway in patients with AV nodal reentrant tachycardia. Little information is available regarding the effect of adenosine on anterograde and retrograde fast pathway conduction.

METHODS AND RESULTS

The effects of adenosine on anterograde and retrograde fast pathway conduction were evaluated in 116 patients (mean age 47 +/- 16 years) with typical AV nodal reentrant tachycardia. Each patient received 12 mg of adenosine during ventricular pacing at a cycle length 20 msec longer than the fast pathway VA block cycle length and during sinus rhythm or atrial pacing at 20 msec longer than the fast pathway AV block cycle length. Anterograde block occurred in 98% of patients compared with retrograde fast pathway block in 62% of patients (P < 0.001). Unresponsiveness of the retrograde fast pathway to adenosine was associated with a shorter AV block cycle length (374 +/- 78 vs 333 +/- 74 msec, P < 0.01), a shorter VA block cycle length (383 +/- 121 vs 307 +/- 49 msec, P < 0.001), and a shorter VA interval during tachycardia (53 +/- 23 vs 41 +/- 17 msec, P < 0.01).

CONCLUSION

Although anterograde fast pathway conduction is almost always blocked by 12 mg of adenosine, retrograde fast pathway conduction is not blocked by adenosine in 38% of patients with typical AV nodal reentrant tachycardia. This indicates that the anterograde and retrograde fast pathways may be anatomically and/or functionally distinct. Unresponsiveness of VA conduction to adenosine is not a reliable indicator of an accessory pathway.