Novel ventricular tachyarrhythmia detection enhancement detects undertreated life-threatening arrhythmias

Figure 1. Algorithm logic flow of VF Therapy Assurance (VFTA). VFTA is activated upon initial detection of rapid ventricular signals and continues to monitor the rhythm until ventricular tachycardia or ventricular fibrillation diagnosis is made, at which point the algorithm automatically adjusts tachyarrhythmia settings to provide therapy. VF = ventricular fibrillation; VT = ventricular tachycardia.

Figure 2. VF Therapy Assurance (VFTA) algorithm validation process. Validation of the VFTA algorithm is performed through a combination of electrogram (EGM) simulation and adjudication of tachyarrhythmia characteristics and device behavior. HV = high-voltage; SVT = supraventricular tachycardia.

Figure 3. Adjudication process to determine appropriateness. Electrograms are classified into 6 rhythm types; each rhythm type corresponds to either appropriate or inappropriate high-voltage (HV) therapy. EGM = electrogram; MVT = monomorphic ventricular tachycardia; NSR = normal sinus rhythm; PVT = polymorphic ventricular tachycardia; SVT = supraventricular tachycardia; VF = ventricular fibrillation; VFTA = VF Therapy Assurance.

Figure 4. Episode and device data summary. A: A total of 19,753/20,000 devices did not activate VF Therapy Assurance (VFTA). Of the 247 devices that activated VFTA, 67 devices delivered therapy that otherwise would not have been delivered or delivered therapy earlier than would have otherwise occurred compared to without VFTA. B: Breakdown of adjudicated rhythm devices and episodes where VFTA was activated. C: Categorization of device and episode for appropriateness and further breakdown of episode/therapy type (1 device in the appropriate categorization exhibited episodes receiving earlier and new therapy). Numbers with parentheses indicate electrogram (EGM)/episodes, numbers without parentheses indicate device/patients. ATP = antitachycardia pacing; MVT = monomorphic ventricular tachycardia; NSR = normal sinus rhythm; PVT = polymorphic ventricular tachycardia; ST = self-terminating; SVT = supraventricular tachycardia.

Figure 5. Example polymorphic ventricular tachycardia (PVT) / ventricular fibrillation (VF) episodes in which VF Therapy Assurance (VFTA) enhanced therapy delivery. A: VFTA activated during postepisode window, promptly providing high-voltage therapy (shock marker) Conventional detection incorrectly diagnosed the end of episode owing to brief slowing in the rhythm, preventing therapy from being delivered. B: VFTA activated at VF detection owing to low-amplitude far-field signals, providing therapy (shock marker). Owing to a few undersensed intervals and momentary slowing of the rhythm, conventional detection would have taken significantly longer to reach detection. C: VFTA activated after a prolonged period in potential ventricular episode, triggering a VF detection and providing therapy (shock marker), where conventional detection would have detected VT1 (monitor zone) owing to programming. Asterisks indicate device sense markers.