SPATIAL AND TEMPORAL INHOMOGENEITY OF ADENOSINES EFFECT ON ATRIAL REFRACTORINESS IN HUMANS - USING ATRIAL FIBRILLATION TO PROBE ATRIAL REFRACTORINESS

Introduction: Adenosine is an antiarrhythmic agent widely used for the diagnosis and treatment of supraventricular tachyarrhythmias. Bolus a dministration of adenosine has been associated with transient atrial f ibrillation, but the underlying mechanisms have not yet been delineate d, due in part to the technical limitations resulting from adenosine's short half-life. In this study, the rapid, repetitive activation of a trial tissue during atrial fibrillation was exploited to yield a nearl y continuous estimate of atrial refractoriness, enabling a description of adenosine's action on atrial refractoriness in humans. Methods and Results: Simultaneous right and left atrial, narrow-spaced, bipolar e lectrograms were recorded in 15 patients before, during, and after bol us administration of 12 mg of adenosine during atrial fibrillation, By estimating the local cycle length of excitation from the atrial activ ation frequency, a refractory period index (RPI) of local tissue was o btained. Adenosine dramatically increased the activation frequency fro m 6.4 +/- 0.7 to 12.2 +/- 12.2 Hz in the right atrium and from 6.1 +/- 0.6 to 8.7 +/- 1.2 Hz in the left atrium, corresponding to a decrease in the RPI from 156 to 82 msec (P < 0.0001) and from 163 to 116 msec (P < 0.0001), respectively. The magnitude of adenosine's effect was gr eater (47% vs 29% shortening) (P < 0.001) and the duration of adenosin e's effect longer (28 vs 19 sec) (P < 0.05) in, the right Compared ed to the left atrium. Conclusion: Adenosine, at doses routinely used cli nically, produces a transient, but spatially and temporally inhomogene ous, shortening of atrial refractoriness, which may explain the increa sed propensity toward atrial fibrillation associated with its use.