Vibration, acceleration, gravitation, and movement: activity controlled rate adaptive pacing during treadmill exercise testing and daily life activities

Enhancement of bicycle exercise capacity in patients with chronotropic incompetence through closed-loop stimulation: a randomized crossover trial

AIMS

This study aimed to investigate the effectiveness of closed-loop stimulation (CLS) pacing compared with the traditional DDD mode in patients with chronotropic incompetence (CI) using bicycle-based cardiopulmonary exercise testing (CPET).

METHODS AND RESULTS

This single-centre, randomized crossover trial involved 40 patients with CI. Patients were randomized to receive either DDD-CLS or DDD mode pacing for 2 months, followed by a crossover to the alternative mode for an additional 2 months. Bicycling-based CPET was conducted at the 3- and 5-month follow-up visits to assess exercise capacity. Other cardiopulmonary exercise outcome measures and health-related quality of life (QoL) were also assessed. DDD-CLS mode pacing significantly improved exercise capacity, resulting in a peak oxygen uptake (14.8 ± 4.0 vs. 12.0 ± 3.6 mL/kg/min, P < 0.001) and oxygen uptake at the ventilatory threshold (10.0 ± 2.2 vs. 8.7 ± 1.8 mL/kg/min, P < 0.001) higher than those of the DDD mode. However, there were no significant differences in other cardiopulmonary exercise outcome measures such as ventilatory efficiency of carbon dioxide production slope, oxygen uptake efficiency slope, and end-tidal carbon dioxide between the two modes. Patients in the DDD-CLS group reported a better QoL, and 97.5% expressed a preference for the DDD-CLS mode.

CONCLUSION

DDD-CLS mode pacing demonstrated improved exercise capacity and QoL in patients with CI, highlighting its potential as an effective pacing strategy for this patient population.

Rate-Responsive Cardiac Pacing: Technological Solutions and Their Applications

Modern cardiac pacemakers are equipped with a function that allows the heart rate to adapt to the current needs of the patient in situations of increased demand related to exercise and stress ("rate-response" function). This function may be based on a variety of mechanisms, such as a built-in accelerometer responding to increased chest movement or algorithms sensing metabolic demand for oxygen, analysis of intrathoracic impedance, and analysis of the heart rhythm (Q-T interval). The latest technologies in the field of rate-response functionality relate to the use of an accelerometer in leadless endocavitary pacemakers; in these devices, the accelerometer enables mapping of the mechanical wave of the heart's work cycle, enabling the pacemaker to correctly sense native impulses and stimulate the ventricles in synchrony with the cycles of atria and heart valves. Another modern system for synchronizing pacing rate with the patient's real-time needs requires a closed-loop system that continuously monitors changes in the dynamics of heart contractions. This article discusses the technical details of various solutions for detecting and responding to situations related to increased oxygen demand (e.g., exercise or stress) in implantable pacemakers, and reviews the results of clinical trials regarding the use of these algorithms.

Identifying the Potential Differentially Expressed miRNAs and mRNAs in Osteonecrosis of the Femoral Head Based on Integrated Analysis

Purpose

Osteonecrosis of the femoral head is a common disease of the hip that leads to severe pain or joint disability. We aimed to identify potential differentially expressed miRNAs and mRNAs in osteonecrosis of the femoral head.

Methods

The data of miRNA and mRNA were firstly downloaded from the database. Secondly, the regulatory network of miRNAs-mRNAs was constructed, followed by function annotation of mRNAs. Thirdly, an in vitro experiment was applied to validate the expression of miRNAs and targeted mRNAs. Finally, GSE123568 dataset was used for electronic validation and diagnostic analysis of targeted mRNAs.

Results

Several regulatory interaction pairs between miRNA and mRNAs were identified, such as hsa-miR-378c-WNT3A/DACT1/CSF1, hsa-let-7a-5p-RCAN2/IL9R, hsa-miR-28-5p-RELA, hsa-miR-3200-5p-RELN, and hsa-miR-532-5p-CLDN18/CLDN10. Interestingly, CLDN10, CLDN18, CSF1, DACT1, IL9R, RCAN2, RELN, and WNT3A had the diagnostic value for osteonecrosis of the femoral head. Wnt signaling pathway (involved WNT3A), chemokine signaling pathway (involved RELA), focal adhesion and ECM-receptor interaction (involved RELN), cell adhesion molecules (CAMs) (involved CLDN18 and CLDN10), cytokine-cytokine receptor interaction, and hematopoietic cell lineage (involved CSF1 and IL9R) were identified.

Conclusion

The identified differentially expressed miRNAs and mRNAs may be involved in the pathology of osteonecrosis of the femoral head.

Closed-Loop Quantitative Verification of Rate-Adaptive Pacemakers

Rate-adaptive pacemakers are cardiac devices able to automatically adjust the pacing rate in patients with chronotropic incompetence, i.e., whose heart is unable to provide an adequate rate at increasing levels of physical, mental, or emotional activity. These devices work by processing data from physiological sensors in order to detect the patient’s activity and update the pacing rate accordingly. Rate adaptation parameters depend on many patient-specific factors, and effective personalization of such treatments can only be achieved through extensive exercise testing, which is normally intolerable for a cardiac patient. In this work, we introduce a data-driven and model-based approach for the automated verification of rate-adaptive pacemakers and formal analysis of personalized treatments. To this purpose, we develop a novel dual-sensor pacemaker model where the adaptive rate is computed by blending information from an accelerometer, and a metabolic sensor based on the QT interval. Our approach enables personalization through the estimation of heart model parameters from patient data (electrocardiogram), and closed-loop analysis through the online generation of synthetic, model-based QT intervals and acceleration signals. In addition to personalization, we also support the derivation of models able to account for the varied characteristics of a virtual patient population, thus enabling safety verification of the device. To capture the probabilistic and nonlinear dynamics of the heart, we define a probabilistic extension of timed I/O automata with data and employ statistical model checking for quantitative verification of rate modulation. We evaluate our rate-adaptive pacemaker design on three subjects and a pool of virtual patients, demonstrating the potential of our approach to provide rigorous, quantitative insights into the closed-loop behavior of the device under different exercise levels and heart conditions.

Effect of rate-adaptive pacing on performance and physiological parameters during activities of daily living in the elderly: results from the CLEAR (Cylos Responds with Physiologic Rate Changes during Daily Activities) study

Aims

For most elderly pacemaker patients, evaluation of rate-adaptive pacing using treadmill and bicycle tests is impractical and not representative of typical daily activities. This study was designed to compare the performance and physiological response of the closed-loop stimulation (CLS) rate-adaptive sensor to accelerometer (XL) and no rate sensor (DDD) during typical daily activity testing.

Methods and results

Subjects recently implanted with a Cylos pacemaker completed timed activities of daily life testing, which included walking, sweeping, and standing from a seated position. Activity performance and physiological response from each sensor mode was evaluated for subjects requiring ≥80% pacing. Overall, 74 subjects needed ≥80% pacing during at least one test. An increase in the area swept (CLS vs. XL, 1.67 m² difference, P = 0.009; CLS vs. DDD, 1.59 m² difference, P = 0.025) and a decrease in the prevalence of orthostatic hypotension (OH) after standing 1 min (CLS vs. XL, odds ratio = 0.16, P = 0.006; CLS vs. DDD, odds ratio = 0.18, P = 0.012) was observed in the CLS mode as compared with XL and DDD. No statistical difference in walk distance was observed between CLS and XL or CLS and DDD.

Conclusion

In acute testing, as compared with XL and DDD, CLS provides a more physiological response during the performance of activities of daily living for subjects with ≥80% pacing. This is clinically reflected in better performance during the sweep test as well as a decrease in the prevalence of OH in our elderly population.

Clinicaltrials.gov identifier: NCT00355797

Clinical and Quality of Life Comparison of Accelerometer, Piezoelectric Crystal, and Blended Sensors in DDDR-Paced Patients with Sinus Node Dysfunction in the Mode Selection Trial (MOST)

INTRODUCTION

Permanent pacemakers are capable of increasing heart rate in response to physical activity by a variety of sensors including accelerometers, piezoelectric crystals, or blended sensors. The impact of these different physiologic sensors on cardiovascular events and quality of life is not known.

METHODS

Of 2,010 patients randomized in the Mode Selection Trial, 1,245 patients were selected with the most commonly used pacemakers with these three sensors. Clinical characteristics and quality of life were compared between groups at baseline, 3 months, and then yearly.

RESULTS

There were 449 patients with an accelerometer sensor device, 682 with a piezoelectric sensor, and 114 with a blended sensor. The groups were similar in terms of age (mean 74 years), gender, and cardiac risk factors but differences existed in weight, heart rate, mitral regurgitation, revascularization history, and drug therapy. The median ventricular pacing frequency was 80% (25th, 75th percentiles 42, 97). After a median follow-up of 33.1 months, the risk of death, heart failure hospitalization, atrial fibrillation, and the combined endpoint of mortality and stroke was not significantly different between the sensor types, after adjustment for baseline differences. Quality of life analyses demonstrated that patients with blended sensors had significantly worse (P < 0.01) physical function than did patients with the other two sensor systems. Moreover, patients receiving blended sensors had the poorest absolute scores, without reaching statistical significance, on 9 of 13 quality of life measures after adjusting for differences in the groups.

CONCLUSION

We found no significant differences among the three most utilized sensors in clinical endpoints. Those patients who received blended sensors had worse physical function quality of life scores. However, clinical selection of the most sophisticated sensor for the most ill patients cannot be excluded as an explanation of these results.

Indications and techniques of pediatric cardiac pacing

There are special challenges associated with the use of transvenous pacemakers in children. For example, a child's chest cavity or vascular dimensions could be too small to host the generator and leads available or required. If leads are implanted, they may stretch as the child grows. This increases the risk that the leads will later dislodge or fracture. Moreover, children requiring pacemakers often have coexisting congenital heart defects and the structural abnormalities of those could hinder easy placement of the pacing system. This article will first review the indications for permanent pacing in children and will then describe the unique challenges associated with such use.

Successful use of an acceleration rate response pacemaker with a transvenous steroid-eluting screw-in lead for third-degree atrioventricular block in a labrador retriever

Permanent pacemakers are commonly used in veterinary practice and can have a dramatic effect on the treatment of heart block. A Labrador Retriever dog suffering from exercise intolerance secondary to third degree atrioventricular block was treated with a new pacemaker system. A steroid-eluting screw-in type lead that has the advantage of being more fixed to the myocardial wall without increasing the pacing threshold was used. The heart rate was regulated with an acceleration sensing pacemaker generator that included several automatic modulation systems. Nineteen months after implantation, the dog has a normal level of activity. The present case suggests that this pacemaker design may offer important advantages for canine patients.

Cardiac pacing. A review

Pacing is a field of rapid clinical progress and technologic advances. Clinical progress in the 1990s included the refinement of indications for pacing as well as the use of pacemakers for new, nonbradycardiac indications, such as the treatment of cardiomyopathies and CHF and the prevention of atrial fibrillation. Important published data and studies in progress are shedding new light on issues of pacing mode selection, and they may influence future practice significantly. Important technologic advances include development of new rate-adaptive sensors and sensor combinations and the evolution of pacemakers into sophisticated diagnostic devices with the capability to store data and ECGs. Automatic algorithms monitor the patient for appropriate capture, sensing, battery status, and lead impedance, providing better patient safety and pacemaker longevity.

Influence of the pacing rate on the atrioventricular conduction time during aerobic and anaerobic exercise: basic concepts for a dromotropically controlled rate responsive pacemaker

The dromotropic pacemaker concept needs a rate responsive algorithm in which the pacing rate is controlled by the atrioventricular conduction time (AVCT). To develop basic concepts for such a rate responsive algorithm, the influence of the pacing rate on the AVCT was investigated. Seven patients (62 +/- 7.8 years) with sick sinus syndrome and intact atrioventricular conduction underwent two cardiopulmonary exercise tests (CPX) on a treadmill. According to the determination of the anaerobic threshold (AT) and the patients maximum capacity in the first incremental CPX the work rate for two exercise levels below and above the AT were chosen for the second constant workload CPX. The calculation of the optimal pacing rate (HRopt) was based on the oxygen uptake (VO2) during exercise after reaching steady-state conditions. According to the increase of the VO2 from 14.8 +/- 2.3 mL/min per kilogram during aerobic work (38.3 +/- 16.0 W) to 19.4 +/- 4.7 mL/min per kilogram during anaerobic work (80.6 +/- 32.3 W), the HRopt was calculated to be 98.6 +/- 6.9 beats/min and 116.4 +/- 4.7 beats/min. Starting from HRopt, the pacing rate was increased (overpacing) and decreased (underpacing) by about 5 beats/min every minute. At optimal pacing rate the AVCT decreased significantly from 233.0 +/- 30.5 ms during aerobic work and to 226.4 +/- 27.3 ms during anaerobic work (P < 0.05). Whereas overpacing induced a significant prolongation of the AVCT during aerobic work (4.17 +/- 1.78 ms per 10 beats/min) and anaerobic work (3.84 +/- 1.60 ms per 10 beats/min), underpacing yielded a significant shortening of the AVCT by about 4.49 +/- 2.64 ms per 10 beats/min during aerobic work and 4.75 +/- 1.87 ms per 10 beats/min during anaerobic work (P < 0.01). The slopes of the regression lines of the relationship between AVCT and pacing rate were not significantly. different. Based on the reciprocal relationship of heart rate (HR) and AVCT, basic concepts may be established for a dromotropic rate responsive algorithm.

[Measurement and evaluation of three-dimensional acceleration signals for rate adaptation of cardiac pacemakers]

The aim of this study was to determine which of the one-dimensional acceleration signals best correlates with the heart rate under the conditions of daily activities, or whether such correlation is shown by three-dimensional acceleration signals. A commercially available biosignal system (ZAK, Germany) was used to record electrographic data and acceleration caused by body movements in the three directions vertical, sagittal and lateral. The evaluation was performed on 12 young healthy volunteers and 4 elderly volunteers with cardiovascular disorders but adequate chronotropic function. Informed consent was given by all participants. Activity signals and heart rate were recorded while walking under two different conditions. For analysis, the pathways were divided into segments with different gradients. All the acceleration signals were analysed statistically and temporally with regard to peak-to-peak value, root mean square value, and step frequency by means of cross correlation. Both statistical and temporal analysis showed that the correlation of heart rate and all one-dimensional acceleration signals and the three-dimensional acceleration signal was relatively low (r < or = 0.6). Walking uphill even showed a negative correlation between acceleration signals and heart rate. Despite the widespread use of activity-controlled pacemakers, the correlation between heart rate and acceleration signals is not satisfactory.

Relationship between atrioventricular delay and oxygen consumption in patients with sick sinus syndrome: relevance to rate responsive pacing

To develop a dromotropic-controlled rate adaptive algorithm for patients with sick sinus syndrome (SSS) and intact AV conduction, 14 pace-maker patients with SSS underwent cardiopulmonary exercise testing (CPX). During exercise, the pace-maker was programmed in an AAT mode without rate adaptation, whereby 3 patients developed supraventricular arrhythmia and 11 patients kept sinus rhythm. Chronotropic incompetence (CI) at heart rate (HR) < 95 beats/min at the anaerobic threshold (AT) was found in five patients. In patients with chronotropic competence (CC), the HR increase was significantly greater than in CI patients (rest: 73.2 +/- 12.6 vs. 64.2 +/- 4.0 beats/min;AT:101.2 +/- 6.2 vs. 82.0 +/- 5.1 beats/min;peak: 135.2 +/- 10.7 vs. 103.2 +/- 10.9 beats/min). There was no significant difference in the AVD between CC and CI patients (rest: 167.7 +/- 38.6 vs. 170.8 +/- 22.5 ms, AT: 156.2 +/- 30.7 vs. 163.6 +/- 21.6 ms, peak: 144.7 +/- 29.0 vs. 152.4 +/- 15.0 ms). The correlation coefficient between HR increase and VO2 was +1.0 and between AVD decrease and VO2 - 1.0 in both groups. An increase in pacing rate from 75 beats/min to 120 beats/min without exercise (overpacing) led to a prolongation of the AV interval of about 30.6 +/- 14.2 ms. Based on this closed loop control with negative feedback, a dromotropic rate adaptive algorithm for patients with SSS and intact AV conduction could be developed.

Evaluation of a dual sensor rate responsive pacing system based on a new concept. French Talent DR Pacemaker Investigators

The minute ventilation is known to be one of the most physiological indicators of exercise. A curvilinear relationship between VE and the normal sinus rhythm (NSR) has been demonstrated in healthy patients. The aim of this study is to show that a pacemaker based on a VE sensor can reproduce such a relationship. Eighty-one patients received a Talent DR 213 (ELA Medical, Montrouge, France) pacemaker with a third-generation rate responsive algorithm. At 1-month follow-up, the patients underwent a treadmill exercise test, after which three groups were defined: group 1 had 6 patients who were 100% paced throughout the exercise test; group 2 had 10 patients who maintained NSR throughout the test; and group 3 had 12 patients who had cardiopulmonary recording during the exercise test. In group 1 patients, the simulation function computed the simulated rate (sim-rate), which was compared to the sensor-driven rate (SDR). In group 2 patients, sim-rate was compared to the NSR. In group 3 patients, cardiac and metabolic reserves were compared to determine the appropriateness of the rate response to exercise (HRR% vs MR%). The results showed that the mean correlation coefficient between sim-rate and SDR was 0.983 +/- 0.005 (P < 0.001); the mean correlation coefficient between NSR and SDR was 0.92 +/- 0.07 (P < 0.001); and a linear relationship was found between HRR% and MR%, with a mean slope of 1.1 +/- 0.2 that was significantly equal to the theoretical value of 1 (P = NS). In conclusion, combining an activity-driven sensor with a physiological sensor allows the preservation of a physiological rate response during exercise.