Electrophysiology Study:
Electrophysiology study was performed using Workmate Claris System with EP-4 Cardiac Stimulator (St Jude, SN Paul, MN, USA). Procedures were performed under local anesthesia with conscious sedation. A minimum of four catheters were used during the study. Quadripolar catheters were placed in the right ventricular apex, His bundle region, right atrial appendage and a decapolar catheter was placed in the coronary sinus. Ventricular and atrial programmed stimulation was performed. Antegrade and retrograde conduction properties of the AP were assessed. When tachycardia was induced, it was determined to be AVRT (atrioventriucular reentrant tachycardia) based on its electrophysiological properties and diagnostic pacing maneuvers during tachycardia.13,14Non-irrigated catheters were used for ablation in most patients and irrigated catheters were used if the former created ineffective lesions or for pathways in the coronary sinus.
On successful ablation of the AP, a timer was started. At 10 minutes after ablation, an intravenous adenosine bolus of 18 mg was administered through a large bore peripheral line immediately followed by a bolus of 20 ml normal saline. In patients with bidirectional AP conduction prior to ablation, it was necessary to demonstrate the absence of antegrade and retrograde AP conduction during adenosine administration. In patients with pathways capable of only unidirectional conduction, it was sufficient to demonstrate it being absent on adenosine testing. The test was considered positive or negative depending on whether adenosine resulted in the resumption of pathway conduction, albeit intermittent (Figure 1,2) or not (Figure 3). If the test was negative, programmed and burst pacing to demonstrate pathway conduction followed by intravenous adenosine was repeated at 30 minutes and the study was terminated if there was no AP reconnection. If the adenosine test at 10 minutes was positive, the pathway was remapped and ablated once there was a return of consistent conduction. Post-procedure ECG was taken after 24 hours.
If AV block and VA block were not demonstrated with the 18mg iv adenosine bolus and the presence or absence of AP conduction could not be ascertained, the test was considered indeterminate.
The sensitivity, specificity, positive and negative predictive value of adenosine testing at ten minutes to identify the recurrence of accessory pathway conduction at 30 minutes were calculated.