Apparatus comprising: means (18, 20, 22) for receiving a cardiac electrical signal and monitoring heart rate therefrom, said means comprising a plurality of electrodes (40, 42, 44) and an electrical sensing module that receives the cardiac electrical signal from the plurality of electrodes; means detecting a tachyarrhythmia episode based on the measured heart rate exceeding a predetermined threshold; means determining whether a detected tachyarrhythmia is a non-sustained tachyarrhythmia based on the length of the detected tachyarrhythmia episode; means identifying a plurality of events in the cardiac electrical signal during a detected non-sustained tachyarrhythmia episode as cardiac depolarizations; means determining a rate of at least some of the events; means determining that the detected non-sustained tachyarrhythmia is a suspected non-physiological non-sustained tachyarrhythmia caused by a sensing integrity condition, based on the rate, said means comprises a non-physiological non-sustained tachyarrhythmia detection module that detects the suspected non-physiological non-sustained tachyarrhythmia based on the cardiac electrical signal; and means storing an electrogram for the determined suspected non-physiological non-sustained tachyarrhythmia based on the detection, the electrogram including at least a portion of the cardiac electrical signal, said means comprising a memory and an episode storage evaluation module that controls storage of the electrogram for the suspected non-physiological non-sustained tachyarrhythmia within the memory based on the detection; said apparatus further comprising an implantable medical device coupled to the electrodes and comprising the memory, the electrical sensing module, and a processor, wherein the processor comprises the non-physiological non-sustained tachyarrhythmia detection module and the episode storage evaluation module; and wherein the implantable medical device comprises at least one of a cardiac pacemaker, a cardioverter, or a defibrillator. means (18, 20, 22) for receiving a cardiac electrical signal and monitoring heart rate therefrom, said means comprising a plurality of electrodes (40, 42, 44) and an electrical sensing module that receives the cardiac electrical signal from the plurality of electrodes; means detecting a tachyarrhythmia episode based on the measured heart rate exceeding a predetermined threshold; means determining whether a detected tachyarrhythmia is a non-sustained tachyarrhythmia based on the length of the detected tachyarrhythmia episode; means identifying a plurality of events in the cardiac electrical signal during a detected non-sustained tachyarrhythmia episode as cardiac depolarizations; means determining a rate of at least some of the events; means determining that the detected non-sustained tachyarrhythmia is a suspected non-physiological non-sustained tachyarrhythmia caused by a sensing integrity condition, based on the rate, said means comprises a non-physiological non-sustained tachyarrhythmia detection module that detects the suspected non-physiological non-sustained tachyarrhythmia based on the cardiac electrical signal; and means storing an electrogram for the determined suspected non-physiological non-sustained tachyarrhythmia based on the detection, the electrogram including at least a portion of the cardiac electrical signal, said means comprising a memory and an episode storage evaluation module that controls storage of the electrogram for the suspected non-physiological non-sustained tachyarrhythmia within the memory based on the detection; said apparatus further comprising an implantable medical device coupled to the electrodes and comprising the memory, the electrical sensing module, and a processor, wherein the processor comprises the non-physiological non-sustained tachyarrhythmia detection module and the episode storage evaluation module; and wherein the implantable medical device comprises at least one of a cardiac pacemaker, a cardioverter, or a defibrillator.