Dual chamber discrimination, threshold for correlation
Patient
This 58-year-old woman underwent implantation of an Incepta single chamber defibrillator.
Trace
- sinus tachycardia;
- acceleration in the slow VT-1 zone (520 ms);
- after 3 cycles classified VT-1, analysis of the correlation;
- 8 out of 10 criterion fulfilled;
at the end of Duration, diagnosis of SVT based on high correlation between morphology during tachycardia and morphology of reference EGM; therapy withheld;
- continuation of cycle-by-cycle analysis;
- on this cycle, the criterion of correlation was no longer fulfilled. The analysis reveals <3 out of 10 cycles with >94% correlation (a programmable threshold with this type of device), despite minimal variations in the EGM morphology on the high-voltage channel. The decision to treat was made ;
- burst of ATP;
- persistence of sinus tachycardia; during redetection, no discrimination (no analysis of the level of correlation);
- second burst of ATP;
- third burst of ATP;
- the ventricular rate slows slightly and falls below the VT zone;
Comments
This episode highlights the importance of the possibility of programming the threshold for correlation. This episode of sinus tachycardia is initially appropriately diagnosed as a supra-ventricular tachycardia. However, the percentage of correlation hoovers around the programmed threshold of 94%. During a certain number of cycles, a majority of the measurements are 93% (below the threshold) explaining the occurrence of inappropriate therapies. The threshold was therefore modified to a lower value solving the problem.
Inhibition initially based on Rhythm ID, before diagnosis of VT and delivery of 3 bursts
