The SonR® micro-accelerometer hemodynamic sensor is enclosed in a sealed capsule at the tip of an atrial pacing lead (IS-1 compatible SonRtip lead).
The sensor measures in g (m/s2) the myocardial micro-accelerations throughout the cardiac cycle; SonR1, one of its main components, is created by the iso-volumic contraction.
The SonR1 component of this signal corresponds to the first heart sound S1. Its variations are correlated to the variations in LV maxdP/dt.
The SonR CRT-D systems digitize and analyze the SonR1 signal originating from the atrial lead. The algorithm contained in these defibrillators automatically optimizes the AV and VV delays on a weekly basis.
The SonR optimization, carried out in the night of Sunday to Monday, is an automatic weekly test of 69 combinations of AV/VV delays. Each combination of AV/VV delays is adjusted in a sequence of 3 adaptive cycles followed by 6 cycles to measure the SonR.
Test of VV delay optimization: Monday at midnight:
Seven BiV configurations are tested (from LV à RV 48 ms to RV à LV 48 ms; in 16 ms steps) using 6 different AV delays, from 30 ms to spontaneous conduction minus 50 ms.
This test includes 42 combinations and 252 SonR measurements.
Test of AV delay optimization at rest: Monday à 01:00h:
After optimization of the VV delay, 11 different AV delays, from 30 ms to spontaneous conduction minus 50 ms are tested. This test includes 11 combinations and 66 SonR measurements.
Test of paced AV delay optimization: Monday at 02:00h:
After optimization of the VV delay, 11 different AV delays, from 30 ms to spontaneous conduction minus 50 ms, are tested. This test includes 11 combinations and 66 SonR measurements.
Test of AV delay optimization during exercise: from Monday at 12:00h:
Optimization of the AV delay during exercise starts as soon as the heart rate has reached a programmed value. After optimization of the VV delay, 5 different AV delays, from 30 ms to spontaneous conduction during exercise minus 50 ms, are tested. This test includes 5 combinations and 30 SonR measurements.
Condition of implementation of AV delays or optimized VV delays:
A new VV delay is implemented only after a ≥ 14% increase in SonR1. If the new optimal VV delay differs from the previous VV delay by > 16 ms, the VV delay is progressively increased in 16 ms steps until this new optimal VV delay has been reached.
The variation in AV delay is systematically limited to 20 ms. The ranges are:
- Sensed AV delay at rest = [60-180 ms]
- Paced AV delay at rest = [92-240 ms]
Tests of AV/ VV delays optimization can also be performed during the patient follow-up, including with the LV only configuration.
The average amplitude of the SonR signal and the adaptation of the AV and VV delays optimized weekly are available in the memories of the SonR CRT-D.
The SonR signal is also recorded during episodes of tachyarrhythmia in order to examine the immediate changes in cardiac contractility and evaluate the hemodynamic tolerance of an arrhythmia.
Fall in the amplitude of the SonR signal at the time of non-sustained ventricular tachycardia
The SonR CRT-D can also transmit real-time SonR signals by telemetry.
Real-time inspection of SonR signal