Adenosine for the management of patients with tachycardias--a new protocol

We developed a new protocol for diagnosis and treatment of patientswith sustained tachycardias (heart rate > 150 beats. min^–1).The patients first underwent vagal manoeuvres; if those remainedunsuccessful, i.v. adenosine in increasing doses of 6, 12, and18 mg was administered until sinus rhythm (SR) or transientatrioventricular (AV) block, unmasking the underlying rhythm,was recorded. In the latter and in the non-responding casesother antiarrhythmics were applied. Ninety-three episodes of tachycardia in 46 patients were treatedaccording to this protocol. Six episodes (6%) were terminatedby carotid massage, 64 of the remaining 87 episodes (74%) respondedto adenosine with return to SR. Conversion to SR occurred moreoften in episodes with narrow- than in wide-complex tachycardia(81 vs 59%, P<005). To achieve SR, the mean adenosine dosewas lower in narrow- than in wide-complex tachycardia (13±8vs 21 ± 10 mg; P<0.01). The duration of asystole afteradenosine did not differ between these two groups, whereas theduration of arrhythmia after adenosine differed significantly(8.5 ± 5.8 vs 18.6 ± 22.9 s; P<0.05). Sideeffects of adenosine such as flush, dyspnoea, and chest paindid not seem to be dose dependent and occurred in about 20%. According to our protocol, in more than 75% SR was achievedin patients with sustained tachycardias after vagal manoeuvresand adenosine.