Spurious diagnosis of ventricular tachycardia
Tracing
Manufacturer Medtronic
Device ILR
Field Reveal DX / Reveal XT
N° 9
Patient
A 74-year-old man with a history of inferior myocardial infarction and 45% left ventricular ejection fraction underwent implantation of a Reveal DX for the diagnosis of syncope preceded by palpitation. The ECG showed complete right bundle branch block and electrophysiological studies revealed a HV interval at 63 ms. Programmed ventricular pacing was unremarkable.
Graph and trace
The device automatically recorded an event labeled FVT. The patient remained asymptomatic in the wake of the episode. The recording was analyzed by the cardiologist during a routine ambulatory visit.
- normal sinus rhythm;
- noise oversensing and ultra-short interval between ventricular electrograms (FS) and undersensing of the next true ventricular event with spurious appearance of a pause;
- major noise artifacts and sensing of ultra-rapid ventricular electrograms (FS); noise is accurately diagnosed intermittently by the device (ultra-rapid VR: ignored); a VR label indicates oversensing in the ventricular refractory period; when multiple events are consecutively sensed in the refractory period, the interval is classified as noise; a VS annotation labels an event that ends a noisy episode;
- FD: sensing of an episode of FVT; sensing of noise is intermittent; while the device correctly labels some segments as noise, others are erroneously interpreted as ventricular arrhythmias;
- end of episode.
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The recording and erroneous interpretation of multiple episodes of noise that saturate the device’s memory can be limited by the optimization of device positioning at the time of implantation, in order to record ventricular electrograms of sufficiently high amplitude and without prominent cycle-to-cycle variations. It is also important to a) create a pocket of sufficiently small dimensions to prevent motion of the device, which may promote the oversensing of noisy signals, and b) program the device with a view to minimize oversensing of P and T-wave, as well as the likelihood of R-wave double counting.