Comparison of paced and intrinsic ECG characteristics for measurement of pacing threshold

Accurate determination of pacing threshold is required for increased longevity of pacemakers and to ensure contraction of the heart. During pacing threshold measurements, surface ECG analysis is necessary for capture verification. Time and frequency domain characteristics of paced and intrinsic surface ECG events were analyzed in 12 pacemaker patients. When compared with amplitude and slew rate, the QRS area provides the best possible discrimination between paced and intrinsic events. Frequency analysis indicates that the power spectrum of a paced ECG is distributed over a shorter frequency range when compared with the intrinsic ECG event. Parameters either in the time or frequency domain or both can be utilized to develop an algorithm for automatic determination of pacing threshold.