A clinical programming system for use with an implanted cardiac pacemaker to automatically determine the minimum pacing energy which is necessary to evoke an atrial depolarization. The system utilizes a series of pacing pulses of progressively decreasing energies to stimulate the atrium, and detects an evoked response during the AV delay interval that follows each pulse. Initial P-wave intervals are subjected to morphological analysis to generate a P-wave template. Subsequent intervals are similarly analyzed and the results compared with the template. The absence of similarity with the template indicates the loss of atrial capture and that the minimum pacing energy has been reached.