New method of atrial and ventricular capture detection.
Polarization as a result of the pacing stimulus has always been the main factor for complicating evoked response detection. Tri-phasic pulse schemes have been developed and used for a long time to solve the polarization issue and are used in commercial products today to enable evoked T-wave detection. For measurement of the evoked R wave in the ventricle and the evoked P wave in the atrium a further optimization step had to be taken. The results presented in this paper show that by individual optimization of the lead system in all cases the evoked P- or R wave could be detected. One aspect of the tri-phasic pulse scheme is the dynamic behavior of the polarization to a change in amplitude or pulse width of the pacing pulse. The time to re-balance the electrode tissue interface and the non-linear behavior of this system can lead to incorrect detections of evoked potentials. The response time of this phenomenon was investigated. A possibility to solve this problem is described with the introduction of a double pulse scheme where a test pulse is placed in front of the regular output pulse. Changes in this double pulse balanced system never lead to a loss of capture situation and the system is given time to re-balance before it can be decided which of the two pulses was responsible for a depolarization of the myocardium.