Dual chamber discrimination: V<A
Tracing
Manufacturer Abbott
Device ICD
Field Discrimination
N° 52
Patient
This 68-year old man, recipient of a Abbott CRT-D implanted in the background of dilated cardiomyopathy with conduction abnormalities and a history of paroxysmal AF, was seen for routine follow-up;
Main programmed parameters
- VF zone at 214 bpm, VT-2 zone at 184 bpm, VT-1 zone at 142 bpm
- 12 cycles in the VF zone, 12 cycles in the VT-2 zone and 12 cycles in the VT-1 zone were needed for the diagnosis
- Effective discrimination in the VT-1 and VT-2 zones
- V<A: if all criteria are fulfilled; morphology (60%, 5 out of 8), stability (50 ms), with 60-ms AV association delta, 12 intervals)
- V=A: if all criteria are fulfilled; morphology (60%, 5 out of 8), sudden onset (20%)
Graph and trace
Narrative
Episode diagnosed as SVT in the V<A arm; in this arm, both the morphology and the stability discrimination criteria were analyzed, both were needed for the diagnosis of VT, both indicated SVT, such that no therapy was delivered;
Tracing
- AF with automatic mode switch (AMS); irregular ventricular conduction; the morphology is in favor of SVT;
- after 3 cycles classified T1, the pacing mode during the episode is DDI;
- from this complex onward, 12 cycles elapsed before the diagnosis, during which the stability criterion was analyzed;
- from this complex onward, 8 cycles elapsed before the diagnosis, during which the morphology criterion was analyzed;
- SVT is diagnosed in the V<A arm (SVT<); the morphology of the 8 analyzed complexes is in favor of SVT (similar morphology); the rhythm is unstable: out of the 12 cycles analyzed, the second shortest and the second longest are measured at, respectively 352 and 469 ms, corresponding to a 127 ms delta. Both criteria are, therefore, in favor of SVT;
- redetection after 6 T1 cycles; confirmation of the diagnosis of SVT;
- slowing of ventricular conduction and diagnosis of return to sinus rhythm; the long-term mode of stimulation is DDDR;
- new mode switch (AMS).
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This episode of AF was accurately diagnosed. Typically, during AF, 2 out of 2 criteria indicate SVT. The rhythm was unstable (SVT) and the morphology was similar (SVT). The programming of “One of” and of “All” effectively distinguishes VT from AF.