Patient with ischemic cardiomyopathy implanted with a dual-chamber ICD (Evera XT DR); the following tracings will allow detailing the operation of the PR Logic algorithm in the setting of an episode of fast conducted AF.
The graph is relatively similar to the previous graph however the device concludes to SVT based on the morphology criterion.
This tracing allows emphasizing the different stages of discrimination during a conducted AF episode. The joint programming of PR Logic and Wavelet significantly reduces the risk of inappropriate therapies in this setting. Indeed, in order for the device to be fooled, the tachycardia must necessarily stabilize sustainably in the VT zone without any long interval which would reset the VT counter. The recommendation to increase the number of required intervals (at least 30 in the VT zone) significantly limits the risk of inappropriate therapies in this setting (30 consecutive intervals in the VT zone without any long interval). In a second step, if the VT counter is filled, PR Logic intervenes. We have seen on the previous tracing that if the ventricular rhythm is irregular, PR Logic concludes to a conducted AF. In this example, the different analysis steps of the PR Logic algorithm reveal:
For a tachycardia with an atrial rate greater than or equal to the ventricular rate, when PR Logic suspects a VT, the morphology analysis can correct a diagnostic error. In this example, it can be seen that 7 of the 8 analyzed QRS complexes display a value greater than the programmed threshold of 70%, which is indicative of a conducted AF; the final diagnosis is therefore SVT and no therapy is delivered.
