65-year-old man implanted with a triple-chamber defibrillator Viva XT CRT-D for idiopathic dilated cardiomyopathy with left bundle branch block; 3 months post implant interrogation.
The first line corresponds to an electrocardiographic lead with superimposed markers, the second line to the bipolar right ventricular EGM (EGM3) and the third line to the bipolar atrial recording (EGM1);
- atrial and biventricular pacing (AP-BV) without AdaptivCRT function;
- programming of the AdaptivCRT algorithm to Auto Bi-V and LV mode;
- temporary prolongation of the AV delay to 300 ms; 5 consecutive AP-VS cycles with a LBBB morphology; the delay between the atrial pacing and the bipolar right ventricular EGM is less than 250 ms;
- LV pacing with fusion.
As explained previously, the device first dichotomizes patients between those with preserved atrioventricular conduction and those with impaired conduction (long PR or complete atrioventricular block). The functioning and philosophy of the algorithm subsequently differs completely according to this assessment. If the conduction is considered "normal", the objective of the algorithm is to seek a fusion between spontaneous right ventricular activation and left ventricular pacing. This algorithm is therefore specifically adapted for patients with left bundle branch block that have normal right ventricular activation which should theoretically be preserved, and an asynchronous and delayed left ventricular activation which should conversely be changed and reversed. In these patients, the potential benefit of this algorithm is twofold:
- reduction in energy consumption and prolongation of the lifetime of the device; indeed, the right ventricle is not paced, which allows reducing battery wear;
- long-term hemodynamic and/or clinical benefit; an ongoing study on a significant number of patients with left bundle branch block will allow assessing the clinical impact of this type of algorithm and its putative effect on the percentage of nonresponse to resynchronization.
This tracing shows the functioning of this algorithm in this setting. In order for the patient to be paced in pure LV mode, the following elements must be met, which is the case in this patient:
- the patient's heart rate must be less than or equal to 100 beats per minute;
- the conduction delay between spontaneous atrial EGM and spontaneous right ventricular EGM must be less than or equal to 200 ms;
- the conduction delay between paced atrial EGM and spontaneous right ventricular EGM must be less than or equal to 250 ms. If one of these criteria is not found, the patient is paced biventricularly.