AdaptivCRT algorithm in a patient with a long PR interval

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Medtronic Devices: CRT Field: AV & VV delays optimization
Patient

76-year-old man implanted with a triple-chamber defibrillator Viva Quad XT CRT-D for ischemic cardiomyopathy with a left bundle branch block and a long PR interval; follow-up 6 months after implant.

Graph and trace

The first line corresponds to an electrocardiographic lead with superimposed markers (MA), the second line corresponds to the bipolar right ventricular EGM (EGM3) and the third line to the bipolar atrial recording (EGM1);

  1. sinus rhythm and biventricular pacing (AS-BV) without AdaptivCRT function;
  2. programming of the AdaptivCRT algorithm in Auto Bi-V and LV mode;
  3. temporary prolongation of the AV delay to 300 ms; 5 AS-VS cycles with a LBBB morphology and a long PR interval; the delay between bipolar atrial EGM and the right ventricular bipolar EGM exceeds 200 ms but lasts less than 300 ms; 
  4. biventricular pacing;
    Deprogramming of the AdaptivCRT and reprogramming to the Auto Bi-V mode;
  5. sinus rhythm and biventricular pacing (AS-BV) without the AdaptivCRT function;
  6. programming of the AdaptivCRT algorithm in Auto Bi-V mode;
  7. temporary prolongation of the AV delay to 300 ms, 5 consecutive AS-VS cycles with a LBBB pattern and a long PR interval; the delay between the bipolar atrial EGM and the right ventricular bipolar EGM exceeds 200 ms but lasts less than 300 ms;
  8. biventricular pacing.
Comments

The various manufacturers offer in their defibrillator or CRT pacemaker platforms, a specific algorithm dedicated to the automatic optimization of the AV and VV delays.

The AdaptivCRT algorithm proposed by MedtronicTM is available with 3 different programming modes:

  1. Adaptive Bi-V: automatic optimization of AV delay and VV delay with biventricular pacing;
  2. Adaptive Bi-V and LV: the device first dichotomizes patients between those with preserved atrioventricular conduction and those with impaired conduction (long PR or complete atrioventricular block); in the first instance, the patient is paced only in the left ventricle with the search for an optimal fusion between LV pacing and spontaneous activation; in the second instance, optimization of AV delay and VV delay with biventricular pacing;
  3. Non adaptive CRT: no automatic adjustment by the device.

The Adaptive CRT algorithm is based on regular measurements of (1) the atrioventricular conduction time measured by the leads corresponding to the delay between the EGM sensed by the right atrial lead and the EGM sensed by the right ventricular lead, 2) the width of the P waves corresponding to the delay between the atrial EGM sensed by the atrial bipolar channel and the end of the atrial EGM measured on the defibrillator far-field channel and 3) the width of the QRS complexes corresponding to the delay between the right ventricular EGM sensed by the RV ventricular bipolar channel and the end of the ventricular EGM measured on the far-field channel.

This algorithm never leads to the programming of extreme values (very short AV delay or very long AV delay). The sensed AV delay range for the AdaptivCRT function is between 80 ms and 140 ms (never less than 80 ms or more than 140 ms). The paced AV delay range for the AdaptivCRT function is between 100 ms and 180 ms. The corresponding V-V pacing delay range for the AdaptivCRT function is between 0 ms and 40 ms (left or right pre-excitation).

Theoritical features / Basic concepts

  Basic concepts : AV delay and VV delay optimization AV delay optimization VV delay optimization LV pacing alone or biventricular pacing ? AdaptivCRT algorithm   AV DELAY AND VV DELAY OPTIMIZATION Biventricular resynchronization provides significant clinical benefit, a reverse remodeling with reduction of the cardiac volume, and a decrease in morbidity and mortality in heart failure patients with wide QRS. The main limitation of this therapy is that all studies found a significant percentage of patients that do not respond favorably to the resynchronization therapy. Different approaches have been proposed to reduce the percentage of non-responders. Once the patient is implanted, a sub-optimal adjustment of the CRT device can contribute to alter the quality of the response. The principle...