ADENOSINE-SENSITIVE ATRIAL TACHYCARDIA

Limited data suggest that adenosine termination of atrial tachycardia is uncommon. To investigate further the effect of adenosine on atrial tachycardia, adenosine (6-12 mg) was administered during sustained atr ial tachycardia in 17 patients. All patients underwent electrophysiolo gical study to exclude other mechanisms of supraventricular tachycardi a. Mean patient age was 51 +/- 20 years (range 18-82 years). Seven pat ients had no structural heart disease. The mean atrial tachycardia cyc le length was 390 +/- 80 msecs (range 260-580). Sustained atrial tachy cardia was induced with atrial extrastimuli in 8 patients, and was eit her incessant at baseline or developed spontaneously during isoprotere nol infusion in 9 patients. Adenosine terminated atrial tachycardia in 3 patients (18%), transiently suppressed atrial tachycardia in 4 pati ents (23%), and produced AV block without affecting tachycardia cycle length in the remaining 10 patients. Adenosine sensitivity was observe d in 3 of 8 patients with tachycardias initiated and terminated by atr ial extrastimuli, and in 4 of 9 patients with spontaneous, but not ind ucible tachycardias including 3 of 4 patients with isoproterenol facil itated tachycardias. Of multiple clinical and electrophysiological var iables examined as potential predictors of adenosine sensitivity, only isoproterenol facilitation of spontaneous or inducible sustained tach ycardia predicted adenosine sensitivity (P = 0.02). These observations suggest that adenosine-sensitive atrial tachycardia may be more commo n than previously recognized. Adenosine sensitivity does not appear to be specific for tachycardia mechanism and cannot be predicted by resp onse to pacing. Atrial tachycardias dependent on beta-adrenergic stimu lation are most likely to be terminated by adenosine.