T wave oversensing after ventricular extrasystole
Tracing
Manufacturer Abbott
Device ICD
Field Sensing
N° 19
Patient
A 21-year-old man presenting with hypertrophic cardiomyopathy, a family history of sudden death and multiple episodes of non-sustained VT, underwent implantation of an Atlas single chamber ICD. He was seen after he had received an electrical shock during exercise.
Main programmed parameters
- VF zone at 222 bpm, VT-2 zone at 182 bpm, VT-1 zone at 160 bpm
- 12 cycles in each the VF, VT-2 and VT-1 zone were needed for the diagnosis
- Maximum sensitivity programmed at 0.3 mV
- VF zone: single 20-J shock, followed by single 30-J shock, followed by four 36-J (maximum strength) shocks; VT-2 zone: 3 bursts of ATP followed by single 15-J shock, followed by single 20-J shock, followed by 2 shocks of maximal strength; VT-1 zone: 6 ramps of ATP followed by single 8-J shock, followed by single 15-J shock, followed by 2 maximum strength shocks
- Effective discrimination in the VT-1 and VT-2 zones
- VVI pacing mode at 40 bpm; VVI post-shock pacing mode at 40 bpm
Graph and trace
Narrative
Episode diagnosed as VF and treated with a 20-J shock.
Tracing
1: Probable exercise-induced sinus tachycardia at 150 bpm;
2: VES with T wave oversensing; unclassified cycle (VES) followed by F (T wave of VES) followed by F (next R wave). The T wave of the normal ventricular complexes was not sensed;
3: Increase in the frequency of VES with T wave oversensing; the cycles are unclassified, T or F; no further VS cycles, precluding the return of sinus rhythm;
4: Diagnosis of VF (12 F classified cycles) and charge of the capacitors;
5: Persistence of T wave oversensing limited to the VES; delivery of 20-J shock;
6: Run of 5 VES, illustrating the potentially proarrhythmic effect of shock delivery;
7: Return of sinus rhythm.
Other articles that may be of interest to you
The follow-up of young recipients of ICD is complicated by a heightened risk of inappropriate therapies caused by fast sinus tachycardias, lead fractures or oversensing. This patient, who suffered from hypertrophic cardiomyopathy, was only intermittently compliant with a regimen of beta-adrenergic blocker. During exercise to a heart rate of 150 bpm, and in the absence of beta blockade, VES developed with oversensing of associated T waves. The count of the events associated with the simultaneous development of sinus tachycardia, VES and T wave oversensing explains the diagnosis of VF made by the device. Furthermore, the increase in the frequency of VES due to the higher exercise level explains the shock delivery. The subsequent run of 5 consecutive VES illustrated the potentially proarrhythmic effects of inappropriate shocks.