ACUTE TREATMENT OF PAROXYSMAL TACHYCARDIA BY ADENOSINE

Background: Adenosine has proven efficacy in clinical trials and in th e electrophysiological laboratory for the treatment of paroxysmal tach ycardia. Aims: To evaluate the efficacy and safety of adenosine admini stered in a clinical setting by non-consultant staff. Methods: Increme ntal doses of adenosine were administered intravenously to five childr en and 32 adults during 39 episodes of paroxysmal tachycardia in a cli nical setting. Structural heart disease was present in 43% of patients . Results: Of 35 episodes of narrow complex tachycardia, adenosine ter minated 26 of28 episodes of supraventricular re-entrant tachycardia (S VRT), one episode of ectopic atrial tachycardia, and induced transient atrioventricular block to reveal atrial arrhythmias in four. Terminat ion of SVRT occurred at a mean (SD) dose of 9.2 (4.0) mg in adults and 0.09 (0.04) mg/kg in children, but two patients had later spontaneous reinitiation of SVRT. Two patients with narrow complex tachycardia wh o failed to respond to adenosine were subsequently found to have ventr icular tachycardia. Adenosine was therapeutic or diagnostic in three o f four episodes of broad complex tachycardia. Overall, by intention to treat by the clinician, adenosine was therapeutic or diagnostic in 34 of 39 episodes (87%). Breathlessness (26%), chest tightness (18%) and flushing (18%) occurred transiently. There were no episodes of hypote nsion. Adenosine was given safely to 15 patients in whom verapamil was considered contraindicated. Conclusions: Adenosine is a safe treatmen t for both narrow and broad complex tachycardias; usually effective fo r the former and diagnostic for the latter.