Dual chamber discrimination: V<A
Tracing
Manufacturer Abbott
Device ICD
Field Discrimination
N° 54
Patient
This 68-year-old woman, recipient of a St Jude medical Promote Accel CRT-D implanted in the context of dilated cardiomyopathy with left bundle branch block, had a history of paroxysmal AF and His bundle ablation and was seen for a routine follow-up.
Main programmed parameters
- VF zone at 214 bpm, VT-2 zone at 184 bpm and VT-1 zone at 150 bpm
- 12 cycles in the VF zone, 12 cycles in the VT-2 zone and 16 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 (50%, 5 out of 8), stability (45 ms), with 60-ms AV association delta, 12 intervals
- V=A: if all criteria are fulfilled; morphology (50%, 5 out of 8), sudden onset (18%)
Graph and trace
Narrative
Episode diagnosed as SVT in the V<A arm. This patient needed 2 out of 2 criteria for the diagnosis of VT; however, the discriminators were discordant, as morphology indicated SVT while stability indicated VT. Hence, SVT was diagnosed and no therapy was delivered.
Tracing
- AMS for AF, biventricular stimulation and no AV conduction;
- regular tachycardia with unclassified cycles initially;
- the pacing mode during the episode is DDI after 3 T1 classified cycles; it is noteworthy that the percentage of similarity was above the programmed 50% threshold;
- from this complex onward, 12 cycles elapsed before the diagnosis, during which stability was analyzed;
- from this complex onward, 8 cycles elapsed before the diagnosis, during which morphology was analyzed;
- diagnosis of SVT in the V<A arm (<SVT); the morphology of the 8 analyzed complexes is in favor of SVT (>50% similarity of morphology); the rhythm is stable, without AV association: out of the 12 analyzed cycles, the second shortest and second longest measured, respectively, 387 and 410 ms, representing a 23-ms delta. Because all criteria were needed for a diagnosis of VT, SVT was diagnosed and therapy was not delivered;
- spontaneous termination of the arrhythmia and diagnosis of return to sinus rhythm.
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This patient, who had undergone His bundle ablation, was pacemaker-dependent and no discrimination of arrhythmias should have been programmed, particularly since morphology might be misleading, as in this example. This tracing shows, once again, that a high proportion of arrhythmic episodes end spontaneously. In this case, the error of discrimination had the advantage of preventing a non-indispensable therapy since the arrhythmia ended spontaneously.