A fully automatic, implantable cardioverter-defibrillator algorithm to prevent inappropriate detection of ventricular tachycardia or fibrillation due to T-wave oversensing in spontaneous rhythm

BackgroundT-wave oversensing (TWOS) may cause inappropriate shocks in patients with implantable cardioverter-defibrillator (ICD). Programming options to prevent TWOS are usually implemented only after TWOS has occurred, and they may compromise sensing of ventricular fibrillation (VF).ObjectiveTo evaluate an ICD algorithm that differentiates TWOS from ventricular tachycardia (VT) or VF to prevent inappropriate detection of VT/VF when TWOS occurs.MethodsWe developed a TWOS algorithm based on both the differential frequency content of R vs T waves and their alternating pattern. Algorithm parameters were developed from a database of stored electrograms. The algorithm was validated on a hardware system consisting of actual ICD circuitry by using an independent database of stored electrograms including inappropriate detections of both VT/VF caused by spontaneous TWOS and induced true VF to assess delays in detection.ResultsWe tested 83 inappropriate detections of VF due to TWOS from 22 patients. All 22 patients had at least 1 successful rejection of TWOS, and rejection was effective in 80 of the 83 episodes. After adjustment for multiple episodes per patient, specificity was 96.6% (95% confidence interval 90.3%–98.8%). In 166 episodes of true VF in 92 patients, the sensitivity for VF detection was 100% (95% confidence interval 98.2%–100%) at a nominal sensitivity of 0.3 mV; the new TWOS algorithm did not delay the detection of VF.ConclusionA novel TWOS rejection algorithm is designed to operate in real time. The algorithm reduced inappropriate detections of VF in spontaneous TWOS episodes by 96.6% while maintaining 100% sensitivity for detecting true VF.