Adenosine bedside test for diagnosis of dual AV-Nodal physiology in patients with supraventricular tachycardia

ABSTRACT

AV-nodal reenterent tachycardia [AVNRT] is one of the most common forms of supraventricular tachycardias [SVTs]. Intravenous adenosine can terminate this arrhythmia and unmask the underlying mechanisms. Utilization of adenosine as a bedside test for diagnosis of dual AV-nodal physiology and subsequently the AVNRT The current study included 20 patients with documented SVTs and were referred for diagnostic electrophysiologic study [EPS] and radiofrequency ablation. Twelve were women and eight were men with a mean age of 33 +/- 10.6 years, range [12 to 47]. Inclusion criteria included 1] documented SVTs either by surface ECG or 24-hour Holter monitoring, 2] no history of previous EPS with or without ablation, and 3] all patients were off anti-arrythmic medications or drugs that interfer with adenosine actions. Patients with surface ECGs that showed signs of antegrade conducting pathway were excluded. Adenosine test. Adenosine was rapidly injected via one femoral vein sheath. Adenosine was administered at increasing doses of 3,6,9 and 12 mg at 2-minute-intervals till signs of dual AV-nodal pathway physiology or high-grade AV-block were observed by a 2-lead ECG and intra-. cardiac electrograms and were considered the end-points of infusion. St and ard electrophysiological study and induction of tachycardia were done through three femoral vein quadripolar catheters and a subclavian vein decapolar catheter. Patients were classified into hree groups according to EPS group I included 11 [55%] patients with slow fast atrioventricular nodal reentrant tachvcardia [AVNRT]. group II included eight patients [40%] with orthodromic atrioventricular reentrant tachycardia [AVRT]. and group III included one patient [5%] with both types of tachycardias [slow/fast AVNRT and orthodromic AVRT]. Adenosine test. The mean adenosine dose used was 9 +/- 2.2mg [range 3 to 12]. Where as the mean dose that selectively blocked the antegrade fast pathway was 7.9 +/- 2 mg. Nine. six and two patients of group I, developed signs of dual AV-nodal pathways, a significant PQ-jump > 50 msec. and echo beats, respectively. Adenosine could not induce AVNRT in patients of group II. The single patient of group III had signs of dual AV-nodal pathways. None of patients in group II and III had PQ-jump or echo beats. AVNRT was induced only in two patients of group 1 and the patient of group III. Comparing both EPS and adenosine test, the latter was 83% sensitive and 88% specific for the diagnosis of dual AV-nodal physiology in patients with SVTs. Adenosine bedside test can be considered a valuable method in diagnosis and selection of patients with AVNRT from patients with narrow-complex SVT