Explanation: there was no death or serious injury associated with the inappropriate defibrillation event.Device evaluation summary: monitor sn (b)(4) and electrode belt sn (b)(4) were returned and evaluated at the distributor, in accordance with procedures recommended by zoll manufacturing corporation.The evaluation included review of downloaded software flag files and ecg strips on the day of the event and incoming functional testing.The software flag files revealed a shock occurred during the time in question and the response button was not depressed.Review of the ecg strip showed that at the time of the shock the patient's rhythm was atrial fibrillation (af) with rapid ventricular response (rvr).Additionally, incoming functional testing was conducted on the suspect device.During functional testing, a 1hz simulated normal sinus rhythm signal was applied to the ecg electrodes, followed by a 5hz simulated treatable arrhythmia signal which verified proper performance of the detection algorithm.During the transition to the 5hz signal, the device was confirmed to properly enter into a treatment sequence which includes a verification of the tactile vibration alarm, audio messaging, and siren alarms, as well as a test of the pulse delivery circuitry.The pulse delivery circuitry test verified proper charging of the high voltage capacitors and proper delivery of five full energy 150j biphasic pulses.The functional testing confirmed proper response button functionality, ecg acquisition, detection algorithm performance, and pulse delivery functionality.The investigation into the event concludes that there was no device malfunction.A cause and effect analysis was conducted using all of the available information which includes the incident report, device evaluation, software flag files, and ecg strips.The primary cause of the inappropriate shock was lack of response button use prior to shock delivery.The response buttons were pressed after the treatment was delivered.The response buttons functioned appropriately.The ecg analysis, conducted by trained ecg technicians, identified the primary cause of the false detection was af with rvr.The following factors could not be ruled out as potential contributing sources (per cause and effect diagram 90e0012_a09_revfi) to the reported problem.The factors are: rate exceeds programmed threshold.Ecg morphology change.Patient error - did not follow training or respond to ifus, alarms, voice prompts.Inappropriate defibrillations are an anticipated risk associated with the use of the lifevest.Patients are instructed through alarms, voice messages, ifu, and training to press the response buttons to prevent an inappropriate defibrillation.The current commercial inappropriate defibrillation rate is consistent with the observed rate during the pivotal clinical trial (b)(4) (0.69% per patient-month with 90% confidence).A summary of the safety and effectiveness data (ssed), including the inappropriate defibrillation safety objective supporting fda's approval of the lifevest, can be found at http://www.Accessdata.Fda.Gov/cdrh_docs/pdf/p010030b.Pdf.The lifevest detection algorithm complies with iec 60601-2-4 performance requirements for sensitivity and specificity.
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