Sensors for rate-adaptive pacing: How they work, strengths, and limitations

Chronotropic incompetence is the inability of the sinus node to increase heart rate commensurate with increased metabolic demand. Cardiac pacing alone may be insufficient to address exercise intolerance, fatigue, dyspnea on exertion, and other symptoms of chronotropic incompetence. Rate-responsive (adaptive) pacing employs sensors to detect physical or physiological indices and mimic the response of the normal sinus node. This review describes the development, strengths, and limitations of a variety of sensors that have been employed to address chronotropic incompetence. A mini-tutorial on programming rate-adaptive parameters is included along with emphasis that patients' lifestyles and underlying medical conditions require careful consideration. In addition, special sensor applications used to respond prophylactically to physiologic signals are detailed and an in-depth discussion of sensors as a potential aid in heart failure management is provided.

Automatic Continuous CRT Optimization to Improve Hemodynamic Response: An Italian Single-Center Experience

Background. Optimization of cardiac resynchronization therapy (CRT) settings after implant can improve response to therapy. In this Italian single-center experience, we investigated the rate of hemodynamic and clinical response in heart failure patients treated with continuously and automatically optimized CRT. Methods. Patients were selected from June 2015 to April 2017 according to the most recent CRT guidelines; all were in sinus rhythm at implant and received a CRT-defibrillator system equipped with SonR, which automatically optimizes AV and VV delays every week. SonR was activated just after implant and remained active during follow-up. The rate of hemodynamic response (R-HR) was defined as ΔLVEF>5%, super-response (R-HSR) as ΔLVEF>15%, and clinical response as a negative transition of NYHA class≥−1 at 6 months follow-up vs. baseline (preimplant). Results. Mean follow-up for the 31 patients (aged 69.9±9.4 years; 61% male; NYHA class II/III 19%/81%; ischemic etiology 65%) was 6±0.7 months. At baseline, LVEF was 29.1%±4.7% and QRS duration 146±13 ms. LBBB morphology was observed in 65%. At 6 months, R-HR was 74% (23/31), R-HSR 32% (10/31), and clinical response rate 77% (24/31). Hemodynamically, patients with ischemic etiology benefited more than those without ischemic etiology, both in terms of response (80% versus 64%) and super-response (35% versus 27%). Conclusions. Continuous automatic weekly optimization of CRT over 6 months consistently improved R-HR, R-HSR, and clinical response in NYHA class II/III heart failure patients versus baseline. Patients with ischemic etiology in particular may benefit hemodynamically from this type of CRT optimization.

The interactions between respiratory and cardiovascular systems in systolic heart failure

Heart failure (HF) is a complex and multifaceted disease. The disease affects multiple organ systems, including the respiratory system. This review provides three unique examples illustrating how the cardiovascular and respiratory systems interrelate because of the pathology of HF. Specifically, these examples outline the impact of HF pathophysiology on 1) respiratory mechanics and the mechanical "cost" of breathing; 2) mechanical interactions of the heart and lungs; and on 3) abnormalities of pulmonary gas exchange during exercise, and how this may be applied to treatment. The goal of this review is to, therefore, raise the awareness that HF, though primarily a disease of the heart, is accompanied by marked pathology of the respiratory system.

Contractility sensor-guided optimization of cardiac resynchronization therapy: results from the RESPOND-CRT trial

Aims

Although cardiac resynchronization therapy (CRT) is effective in patients with systolic heart failure (HF) and a wide QRS interval, a substantial proportion of patients remain non-responsive. The SonR contractility sensor embedded in the right atrial lead enables individualized automatic optimization of the atrioventricular (AV) and interventricular (VV) timings. The RESPOND-CRT study investigated the safety and efficacy of the contractility sensor system in HF patients undergoing CRT.

Methods and results

RESPOND-CRT was a prospective, randomized, double-blinded, multicentre, non-inferiority trial. Patients were randomized (2:1, respectively) to receive weekly, automatic CRT optimization with SonR vs. 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. Responder rates were 75.0% in the SonR arm and 70.4% in the Echo arm (mean difference, 4.6%; 95% CI, −1.4% to 10.6%; P < 0.001 for non-inferiority margin −10.0%) (Table 2). 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).

Conclusion

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.

ClinicalTrials.gov number

NCT01534234

Impact of haemodynamic SonR sensor on monitoring of left ventricular function in patients undergoing cardiac resynchronization therapy

Aims

The haemodynamic SonR sensor is able to measure myocardial contractility. The isometric effort is useful in quantifying left ventricular (LV) performance. We investigated the amplitude changes in SonR signal over time and during static exercise according to the recovery of the left ventricle.

Methods and results

Twenty five patients [18 male, 70 ± 8 years, LV ejection fraction (LVEF) 29 ± 5%, in sinus rhythm] underwent biventricular SonR implantable cardioverter defibrillator implant. After procedure and at 6 months, each patient underwent detection of SonR signal and continuous measurement of blood pressure, at rest and during isometric effort. During evaluation at baseline device was programmed in VVI at 40 bpm while in DDD at 60 bpm at follow-up. At 6 months, LV reverse remodelling was investigated. Cardiac resynchronization therapy patients were considered responders when an absolute improvement in LV ejection fraction ≥ 5% occurred. At 6 months, 14 (56%) patients were responders and 11 (44%) non-responders (mean LVEF 40 ± 10% vs. 27 ± 6%, respectively). In responders, SonR value did not significantly change at follow-up compared to baseline (P = 0.894). At follow-up, SonR value was not significantly different between two groups (P = 0.651). SonR signal significantly increased during isometric effort in responders (P = 0.002) while it slightly decreased in non-responders at follow-up (P = 0.572). No differences were observed in response to isometric effort between two groups at baseline (P = 0.182, P = 0.069, respectively).

Conclusions

The absolute SonR amplitude provides limited information on the status of LV performance. The variation in SonR signal during static exercise is more likely to identify responders at follow-up.

The clinical benefit of cardiac resynchronization therapy optimization using a device-based hemodynamic sensor in a patient with dilated cardiomyopathy: a case report

Introduction

Results on the evolution of the clinical status of patients undergoing cardiac resynchronization therapy with a defibrillator after automatic optimization of their cardiac resynchronization therapy are scarce. We observed a rapid and important change in the clinical status of our non-responding patient following activation of a sensor capable of weekly atrioventricular and interventricular delays' optimization.

Case presentation

A 78-year-old Caucasian man presented with dilated cardiomyopathy, left bundle branch block, a left ventricular ejection fraction of 35 %, New York Heart Association class III/IV heart failure, and paroxysmal atrial fibrillation. Our patient was implanted with a cardiac resynchronization device with a defibrillator and the SonRtip atrial lead. Right ventricular and left ventricular leads were also implanted. Because of the recurrence of atrial fibrillation, the automatic optimization was set off at discharge. Consequently, the device did not optimize atrioventricular and interventricular delays (programming at discharge: 125 ms for the atrioventricular delay and 0 ms for the interventriculardelay). Our patient was treated with an anti-arrhythmic drug. Five months after implantation, his clinical status remained impaired (left ventricular ejection fraction = 30 %). The SonR signal amplitude had also decreased from 0.52 g to 0.29 g. Nevertheless, because our patient was no longer presenting with atrial fibrillation, the anti-arrhythmic treatment was stopped and the SonR optimization system was activated. After 2 months of automatic cardiac resynchronization therapy with defibrillator optimization, our patient’s clinical status had significantly improved (left ventricular ejection fraction = 60 %, New York Heart Association class II) and the SonR signal amplitude had doubled shortly after the first weekly automatic optimization.

Conclusion

In this non-responding patient, device-based automatic cardiac resynchronization therapy optimization was shown to significantly improve his clinical status.

Assessment of Myocardial Contractility by SonR Sensor in Patients Undergoing Cardiac Resynchronization Therapy

BACKGROUND

SonR sensor signal correlates well with myocardial contractility expressed in terms of left ventricular (LV) dP/dt max. The aim of our study was to evaluate the changes in myocardial contractility during isometric effort in heart failure patients undergoing cardiac resynchronization therapy (CRT) with right atrial SonR sensor.

METHODS

Thirty-one patients (19 men, 65 ± 7 years, LV ejection fraction [LVEF] 28% ± 5%, in sinus rhythm) were implanted with a CRT-defibrillator (CRT-D) device equipped with SonR sensor, which was programmed in VVI mode at 40 beats/min. Twenty-four hours after implantation, each patient underwent a noninvasive hemodynamic evaluation at rest and during isometric effort, including: (1) measurement of beat-to-beat endocavitary SonR signal; (2) echocardiographic assessment; and (3) continuous measurement of blood pressure with Nexfin method (BMEYE, Amsterdam, the Netherlands). The following contractility parameters were considered: (1) mean value of beat-to-beat SonR signal; (2) mean value of LV dP/dt by Nexfin system; and (3) fractional shortening (FS) by echocardiography.

RESULTS

At the third minute of the isometric effort, mean value of SonR signal significantly increased from baseline (P < 0.001). Similarly, mean value of both LV dP/dt by Nexfin and FS significantly increased compared to the resting condition (P < 0.001; P < 0.001). While in 27 (88%) patients SonR signal increased at the third minute of the isometric effort, in four (12%) patients SonR signal decreased. In these patients, both LV dP/dt by Nexfin and FS consensually decreased.

CONCLUSIONS

In CRT patients, SonR sensor is able to detect changes in myocardial contractility in a consensual way like noninvasive methods such as Nexfin system and echocardiography.

First clinical evaluation of an atrial haemodynamic sensor lead for automatic optimization of cardiac resynchronization therapy

AIMS

One option to improve cardiac resynchronization therapy (CRT) responder rates lies in the optimization of pacing intervals. A haemodynamic sensor embedded in the SonRtip atrial lead measures cardiac contractility and provides a systematic automatic atrioventricular and interventricular delays optimization. This multi-centre study evaluated the safety and performance of the lead, up to 1 year.

METHODS AND RESULTS

A total of 99 patients were implanted with the system composed of the lead and a CRT-Defibrillator device. Patients were followed at 1, 3, 6, and 12 months post-implant. The primary safety objective was to demonstrate that the atrial lead complication free rate was superior to 90% at 3-months follow-up visit. A lead handling questionnaire was filled by implanting investigators. Lead electrical performances and the performance of the system to compute AV and VV delays were evaluated at each study visit over 1 year. The complication free rate at 3 months post-implant was 99.0% [95%CI 94.5-100.0%], P < 0.001. Electrical performances of the lead were adequate whatever the atrial lead position and remained stable over the study period. The optimization algorithm was able to compute AV and VV delays in 97% of patients, during >75% of the weeks.

CONCLUSION

The atrial lead is safe to implant and shows stable electrical performance over time. It therefore offers a promising tool for automatic CRT optimization to further improve responder rates to CRT.

Clinical Relevance Of Systematic CRT Device Optimization

Cardiac Resynchronization Therapy (CRT) is known as a highly effective therapy in advanced heart failure patients with cardiac dyssynchrony. However, still one third of patients do not respond (or sub-optimally respond) to CRT. Among the many contributors for the high rate of non-responders, the lack of procedures dedicated to CRT device settings optimization (parameters to regulate AV synchrony and VV synchrony) is known as one of the most frequent. The most recent HF/CRT Guidelines do not recommend to carry-out optimization procedures in every CRT patient; they simply state those procedures "could be useful in selected patients", even though their role in improving response has not been proven. Echocardiography techniques still remain the gold-standard reference method to the purpose of CRT settings optimization. However, due to its severe limitations in the routine of CRT patients management (time and resource consuming, scarce reproducibility, inter and intra-operator dependency), echocardiography optimization is widely under-utilized in the real-world of CRT follow-up visits. As a consequence, device-based techniques have been developed to by-pass the need for repeated echo examinations to optimize CRT settings. In this report the available device-based optimization techniques onboard on CRT devices are shortly reviewed, with a specific focus on clinical outcomes observed in trials comparing these methods vs. clinical practice or echo-guided optimization methods. Particular emphasis is dedicated to hemodynamic methods and automaticity of optimization algorithms (making real the concept of "ambulatory CRT optimization"). In fact a hemodynamic-based approach combined with a concept of frequent re-optimization has been associated - although retrospectively - with a better clinical outcome on the long-term follow-up of CRT patients. Large randomized trials are ongoing to prospectively clarify the impact of automatic optimization procedures.