Automated left ventricular threshold
The function of the automated LV threshold is often very close to that described for the RV lead. The threshold measurement is based on the analysis of the evoked response, or by observing the synchronization of the RV events sensed after a stimulated LV event. The threshold is measured at regular intervals, depending on the manufacturer, after which a safety margin is programmed, without further cycle-by-cycle verification of capture. It is noteworthy that Microport dual and triple chamber devices do not verify the cycle-by-cycle LV or RV lead capture.
Example of automatic LV pacing test. LV pacing is performed with decreasing pacing output until there is a clear change in the QRS complex on the far field channel. The device recognizes a loss of capture and saves the preceding pacing output (0.75V in this case) as the LV pacing threshold.