Adenosine-sensitive decremental conduction over short non-decremental atrioventricular accessory pathways after radiofrequency ablation: case series

Adenosine-A drug with myriad utility in the diagnosis and treatment of arrhythmias

Adenosine has been used in the emergency treatment of arrhythmia for more than nine decades. However, cardiologists are often unfamiliar about its basic mechanism and various diagnostic and therapeutic uses, considering it mainly as a therapeutic drug for supraventricular tachycardia. This article discusses the role of adenosine relevant to emergency physicians, cardiologists, and electrophysiologists. Understanding of the mechanisms of adenosine and its electrophysiological effects is discussed first, followed by dosing, side effects, diagnostic, and therapeutic uses. Finally, the role of adenosine in the electrophysiology laboratory is discussed.

The use of adenosine to identify dormant conduction after accessory pathway ablation: a single center experience and literature review

INTRODUCTION

Atrio-ventricular reentrant tachycardias (AVRT) represent around 40 percent of supraventricular tachycardias. After ablation, recurrence rates are around 10 percent. Adenosine has been described as a useful tool to assess presence of dormant conduction and predict recurrence after apparently successful ablation. We reviewed the patients of our service and assessed the role of adenosine in predicting dormant conduction and factors that could influence recurrence rates.

METHODS

We retrospectively reviewed electrophysiologic studies and medical charts of 65 patients who had AVRT ablation and had adenosine used to assess dormant conduction at a single quaternary center between 2011 and 2015. Dormant conduction was defined as transient recovery of the preexcitation (for pathways with antegrade conduction) or return of the retrograde conduction through an apparently successfully ablated concealed accessory pathway (AP).

RESULTS

One patient was found to have dormant conduction (1.5%) with early recurrence that was not further ablated due to the difficult location of the AP. The overall recurrence rate was 4.6%. General features like location of AP's, their properties, ablation times and technique were assessed.

CONCLUSION

Similar to its use in identifying other arrhythmias, adenosine may be useful in identifying dormant conduction for further ablation during initial ablation of an accessory pathway; however, the absence of dormant conduction on adenosine testing does not reliably predict non-recurrence. The low recurrence rates in our service may be related to the frequent use of irrigated tip catheters, 3D mapping and long average ablation time over the successful site of ablation.

Radiofrequency catheter ablation of accessory pathways at the site of prior valve surgery

BACKGROUND

Radiofrequency catheter ablation (RFCA) for accessory pathways (APs) at the site of prior valve surgery (VS) remains challenging. We aimed to clarify the factors associated with successful RFCA for such APs.

METHODS

Upon reviewing a RFCA registry and previous case reports, we included nine patients who underwent RFCA of APs at the site of prior VS (total-VS group; age, 34.0 [24.5-45.0] years; men, 4/9) and 196 patients who underwent RFCA of APs with no history of VS (no-VS group; age, 40.5 [23.0-54.0] years; men, 114/196). Electrophysiological features, procedural details, and outcomes were examined.

RESULTS

Accessory pathway exhibited decremental conduction in four of nine patients in the total-VS group. The number of RFCA attempts was significantly higher in the total-VS group than in the no-VS group (10.0 [4.5-14.5] vs 2.0 [1.0-3.0]; P < 0.001). In four patients who underwent mitral VS, successful RFCA was achieved using the transaortic approach, coronary sinus (CS) approach, or bipolar ablation. In three patients who underwent tricuspid VS, successful RFCA was achieved using the above-prosthetics or trans-prosthetics approach. In two patients, RFCA failed. The trans-prosthetics approach and bipolar ablation technique were effective. The transaortic and CS approaches were occasionally effective. The transseptal approach was ineffective.

CONCLUSIONS

Successful RFCA of APs at the site of prior VS can be achieved by detailed mapping of the areas both above and below the prosthetic valve, as well as by ensuring effective radiofrequency energy delivery using various catheter approaches and RFCA techniques.