In an implantable heart stimulating device and a method of the operation thereof, device has a control circuit that detects an evoked responses to delivered pacing pulses and to carry out an automatic capture routine. The control circuit is arranged to automatically temporarily disable the automatic capture routine on the basis of at least one of the following criteria: a1) if more than a predetermined number of threshold searches have been performed during a certain time, and b1) if a variable time delay with which the device operates is changed such that a pacing pulse may be delivered by the device during the evoked response time window.
