60-year-old man implanted with a Lumax 340 DR-T dual-chamber ICD for dilated cardiomyopathy with VT episodes; event report (yellow color) in the setting of a classified VT2.
4 channels are available: the markers with the time intervals, the shock channel (FF: far field) between the ventricular lead coil and the pulse generator, the atrial sensing channel (A), the right ventricular sensing channel (RV).
The first discrimination level of the SMART algorithm is the comparative analysis of atrial and ventricular rhythm. In this patient, the discrimination of the episode is correct (VT) in spite of an error in the count of the atrial electrograms (P wave in the post-ventricular atrial blanking period). Accurate sensing at the level of both chambers is essential for the proper operation of this dual-chamber discrimination algorithm. Atrial lead dislodgement, crosstalk with atrial oversensing of the R wave, undersensing of atrial activity due to low-voltage AF activity, and occurrence of atrial activity in the post-ventricular atrial blanking period can be associated with inaccurate dual-chamber discrimination. The post-ventricular atrial blanking period should be programmed sufficiently long to avoid crosstalk but not too long to avoid errors in the atrial electrogram counts. It should be noted that the atrial intervals falling within the PVARP (Ars) are integrated in the evaluation of the atrial rate.
