Abstract: A method and apparatus are provided for detecting and arresting a condition of tachycardia. Stimulating pulses are provided in a search routine within a selected time interval after a tachycardia beat. The heart is monitored after each pulse application and the search is terminated when a normal heartbeat is detected. In a preferred search routine, the refractory interval of the heart adjacent the electrode is determined during a first search routine. If the first search routine does not terminate the tachycardia, the refractory interval found during the search is stored. A second pulse is then applied in a time interval following the refractory interval pulse to break the tachycardia. The breaking interval is determined through a second search routine generated in an interval following the refractory interval pulse.