Patient - EN
A 60-year-old man received an Analyst Accel single chamber ICD after suffering an episode of aborted sudden cardiac death. He was on a regimen of beta-adrenergic blocker and anticoagulation for paroxysmal atrial fibrillation.
Main programmed parameters
- VF zone at 230 bpm, VT-2 zone at 181 bpm, VT-1 zone at 141 bpm
- 12 cycles in each the VF, the VT-2 and the VT-1 zones were needed for the diagnosis
- Maximum sensitivity programmed at 0.3 mV
- VF zone: six 36-J shocks (maximum strength); VT-2 zone: 3 bursts followed by 3 ramps of ATP, followed by a single 25-J shock, followed by 2 shocks of maximal strength. The VT-1 zone was set on monitor
- Effective discrimination in the VT-1 and VT-2 zones
- VVI pacing mode programmed at 40 bpm; VVI post-shock pacing mode at 60 bpm
Graph and trace
Narrative
Episode labeled by the ICD as supraventricular tachycardia (SVT) lasting 1 min 38 sec without the delivery of therapy. The absence of sudden onset and the unstable rhythm prompted the diagnosis of SVT (marked SVR).
Tracing
- Sensing of ventricular depolarization. A signal with a fixed morphology was sensed very regularly by the ICD at a rate of approximately 35 bpm throughout the tracing;
- Detection of regular activity at a rate of approximately 140 bpm, and a different morphology than the preceding complex, probably consistent with an atrial tachycardia;
- After 12 T1 cycles, the VT-1 counter was filled and the recording of EGM was triggered. The duration of EGM memorization before the trigger (in this case 14 sec) was programmable. Diagnosis of SVT was made by the ICD. The irregular occurrence of ventricular events among atrial EGM sensed in the ventricle gave the pseudo-tachycardia an irregular appearance;
- After 6 T1 classified cycles, the T-1 redetection counter was filled. The discrimination analysis was repeated and the diagnosis of SVT was re-confirmed throughout the episode;
- 30 sec after the onset of recording, the memorization of EGM was temporarily interrupted and restarted for 14 sec before the diagnosis of return to sinus rhythm replaced the initial diagnosis of SVT;
- Diagnosis of return of sinus rhythm after 3 consecutive VS, accounting for intervening unclassified intervals.
NID old - EN
902
AV conduction in this patient was abnormal. Long ventricular diastoles were present after the onset of an atrial tachycardia. The atrial activity was sensed in the ventricular channel. This rapid oversensed rhythm inhibited ventricular pacing. The intermittent occurrence of ventricular EGM explains the « irregular » appearance and instability of the arrhythmia. The diagnosis of SVT made by the ICD prevented the delivery of inappropriate therapy. A first choice consisted of lowering the ventricular sensitivity to prevent the oversensing of atrial activity, which, however, incurs a risk of VF undersensing. A second choice would consist of repositioning the lead.