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.