Fig. 3. Reproducible effect of an adenosine bolus dose on coronary flow and stimulus-to-ventricle (S-V) interval. Shown are representative examples and summary data of the A2A-adenosine receptor–mediated vasodilator response (A and B ) and of the A1-adenosine receptor–mediated S-V interval prolongation (C and D ). (C , inset ) Representative electrogram used to measure the S-V interval (arrows). Adenosine-induced increases in coronary flow are expressed as changes in the area under the flow–time curve in three hearts. Changes in S-V interval were measured at peak increase in coronary flow. Summary data are expressed as mean ± SD. A = atrium; Ado = adenosine; H = His bundle; S = stimulus artifact; V = ventricle.