Optimization of the AV delay in a recipient of Medtronic defibrillator with a prolonged PR interval

Patient

This 76-year-old man received a Medtronic Viva Quad XT CRT-D for dilated cardiomyopathy with atypical bundle branch block and a long PR interval. He was seen for a follow-up visit, 3 months after the implant.

Trace

The first line is an ECG lead with superimposed markers (MA); the second line is the bipolar atrial recording (EGM1); the third line is the bipolar RV EGM (EGM3); the fourth line is the distal (tip) LV / RV coil lead (EGM2).

sinus rhythm and BiV stimulation (AS-BV) without AdaptivCRT function;
programming of the AdaptivCRT algorithm in Auto BiV and LV mode.
temporary prolongation of the AV delay to 300 ms. Five consecutive AS-VS cycles with left bundle branch block morphology and long PR interval. The delay between bipolar atrial and RV bipolar EGM exceeds 250 ms though lasts less than 300 ms.
BiV stimulation.
Deprogramming of the AdaptivCRT function and increase in the minimum heart rate to 75 bpm.
atrial pacing and BiV stimulation (AP-BV) without AdaptivCRT function.
6: programming of the adaptivCRT algorithm in Auto BiV and LV mode.
temporary prolongation of the AV delay to 300 ms. Five consecutive AP-VS cycles with left bundle branch block morphology and long PR interval. The delay between the atrial stimulus and the bipolar RV EGM exceeds 250 ms though lasts less than 300 ms.
BiV stimulation.

Comments

This tracing illustrates other characteristics of this algorithm. The operating functions are very similar during atrial sensed and paced rhythm. The threshold used to define a normal versus abnormal AV conduction is 200 ms during spontaneous atrial rhythm and 250 ms when the atrium is paced. In this patient with a long PR interval, both AV delays are considered abnormal. However, they do not exceed 300 ms. If the AV delay after a spontaneous or paced atrial event exceeds 300 ms, BiV stimulation is delivered. The device diagnoses AV block and the time between measurements of the AV interval doubles.

Heart rate histograms show the percentage of total ventricular sensing and pacing. They also show the percentages delivered in BiV stimulation and in LV stimulation modes.

Pacing & Defibrillation

ECG

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