Contractility Sensor-Guided Optimization of CRT

Study Questions:

What is the safety and efficacy of the SonR contractility sensor system in heart failure (HF) patients undergoing cardiac resynchronization therapy (CRT)?


RESPOND-CRT was a prospective, randomized, double-blinded, multicenter, noninferiority trial, in which patients were randomized to receive weekly, automatic CRT optimization with SonR versus an echo-guided optimization of AV and VV timings. The primary efficacy endpoint was the rate of clinical responders (patients alive without adjudicated HF-related events, with improvement in New York Heart Association class or quality of life), at 12 months.


The study randomized 998 patients. The rate of responders was 75% in the SonR group versus 70% within the echo group (mean difference, 4.6%; 95% confidence interval [CI], 1.4-10.6%; p < 0.001 for noninferiority margin 10%). At an overall mean follow-up of 548 ± 190 days, SonR was associated with a 35% risk reduction in HF hospitalization (hazard ratio, 0.65; 95% CI, 0.46–0.92; log-rank p < 0.01).


The authors concluded that automatic AV and VV optimization using the contractility sensor was safe and as effective as echo-guided AV and VV optimization in increasing response to CRT.


The SonR contractility sensor made by LivaNova is embedded in the right atrial lead. It is made to detect cardiac muscle vibrations, which reflect the first heart sound and are correlated to the left ventricular dP/dtmax. The results of this study are consistent with several other randomized clinical trials of AV and VV algorithms versus echo-guided optimization showing that the nonecho algorithms are noninferior. Unfortunately, echo-guided optimization has not been shown to be of appreciable benefit in several large multicenter studies, such as SMART-AV (Boston Scientific), FREEDOM (St. Jude), and Adaptive CRT (Medtronic), compared with a fixed 100–120 ms AV delay and simultaneous biventricular pacing (RV and LV).

Clinical Topics: Arrhythmias and Clinical EP, Heart Failure and Cardiomyopathies, Noninvasive Imaging, Prevention, Implantable Devices, SCD/Ventricular Arrhythmias, Atrial Fibrillation/Supraventricular Arrhythmias, Acute Heart Failure, Echocardiography/Ultrasound

Keywords: Arrhythmias, Cardiac, Cardiac Resynchronization Therapy, Diagnostic Imaging, Echocardiography, Heart Failure, Quality of Life, Secondary Prevention, Risk Reduction Behavior

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