A pacing mode using automatically increasing number of stimuli with adaptive coupling intervals was evaluated prospectively as a possible universal pacing mode, because a universal mode would save extensive testing and tailoring time. In group 1, which included 7 patients with implanted antitachycardia pacemaker systems, the test mode was compared with the previously tested and tailored mode. In group 2, which included 11 patients undergoing invasive electrophysiologic study, the test mode was compared with the scanning and asynchronous burst mode. There were 4 patients in group 3. The mode was tested prospectively in these 4 patients. Three of these patients were tested after pacemaker implantation (in supine and upright body position and after moderate exercise). The fourth patient had recurring episodes of VT, which were terminated with the test mode via an external lead. Of 209 tachycardias (156 supraventricular tachycardia [SVT] and 53 with VT) studied with the test mode, 1 episode of nonsustained atrial fibrillation was induced from the ventricle and 1 episode of VT was not terminated using the test mode and long coupling intervals. Two episodes of VT in patients with a recent myocardial infarction (MI) required direct-current countershock: due to acceleration in 1 patient and due to VF in 1. All other tachycardias were terminated promptly by the test mode without prior knowledge about successful coupling intervals or number of stimuli. Of the remaining 106 tachycardias studied (69 SVT, 37 VT) the scanning mode failed to terminate 2 episodes of SVT with up to 4 atrial premature beats and induced acceleration of VT in 1 patient with a recent MI.(ABSTRACT TRUNCATED AT 250 WORDS)