A coupled/paired stimulus pulse is delivered to the heart at an inter-pulse interval following one of i) detection of an intrinsic depolarization or ii) delivery of a primary stimulus pulse. Capture resulting from the coupled/paired stimulus pulse is sensed for. In response to capture by a coupled/paired stimulus pulse, the inter-pulse interval is incrementally decreased by a first amount until there is no capture by a coupled/paired stimulus pulse. In response to no capture by a coupled/paired stimulus pulse, the inter-pulse interval is incrementally increased by a second amount greater than the first amount, until capture by a coupled/paired stimulus pulse is detected. Once capture is again detected, paired/coupled pacing is delivered at the inter-pulse interval which resulted in capture for a predetermined period of time or until loss of capture occurs.
