Determination of pacing capture in implantable defibrillators: Benefit of evoked response detection using RV coil to can vector

Automatic detection of capture in ICDs would be useful for ensuring normal pacing function and lead integrity and may increase device longevity. Evoke d response detection can be difficult due to postpace polarization. Polariz ation on the RV coil to can vector, however, should be absent when pacing w ith a true bipolar lead (pace tip to ring). Polarization on the HV coil to can vector should be low in an integrated bipolar lead due to the large sur face area of the coil. Ventricular-paced responses were prospectively recor ded in 20 patients during ICD implantation or replacement. Capture and loss of capture responses were noted during threshold searches with electrogram s recorded between the RV coil and can. A detector wets designed to discrim inate between capture and noncapture-paced responses using data from the fi rst 11 patients and validated on the remaining 9. The detector had a sensit ivity of 99.9% (detected capture on capture beats), and had a specificity o f 100% (defected no capture on noncapture beats) for all lead configuration s. There was no measurable polarization with true bipolar leads. in integra ted bipolar leads, maximum polarization ranged from 0.0 to 16.7mV. In concl usion, paced evoked responses can be detected in ICDs using the HV coil to can vector using standard pacing waveforms. Special polarization reducing p acing waveforms are not required. These observations could be used to desig n ICDs with automatic pacing threshold defection.