Individual optimization of pacing sensors improves exercise capacity without influencing quality of life

Application of an accelerometer in adjusting parameters and detecting characteristics in the pacemaker rate response

Objective.To study the application of an accelerometer in adjusting the parameters, setting the sensor indicated rate (SIR) and detecting characteristics in the pacemaker (PM) rate response.Approach.Three-axis (GT9X Link-type) accelerometers were positioned on the waist and chest in 33 participants implanted with rate responsive PMs while wearing an ambulatory ECG recorder (Holter). During the walking test, by collecting vertical axis (Axis-1) activity intensity counts, Axis-1' metabolic equivalent of energy (MET_axis-1) and its expected heart rate (HR_met-axis1) were calculated by the relevant equations, and on the basis of the HR_met-axis1as the target heart rate, the SIR was set by programming the rate response slope parameter. During the following daily walking activity, the physical activity parameters and Holter ECG was recorded continuously. After the end of the whole test the analysis on these data recorded was performed retrospectively.Main results.After completing the SIR setting, in 24 participants with complete ventricular pacing the comparison between HR_met-axis1(92.5 ± 7.8 BPM) and the HR_vp-Holter(94.0 ± 10.5 BPM) showed no statistical difference (ΔHR: 1.25 ± 6.69 BPM,P: 0.568) during the last one walking test, and there was also no significant difference (ΔHR: 2.8 ± 7.1 BPM,P: 0.398) between the HR_met-axis1(90.7 ± 7.1 BPM) and HR_vp-Holter(93.4 ± 10.3 BPM) during daily walking activity. In addition, in the data of 108 time intervals selected during the daily walking activities in the abovementioned 24 participants, MET_axis-1and HR_vp-Holtercorrelation analysis showed good correlation and the regression equation was HR = 12.4 × MET±43.1 (P<0.0001).Significance.An accelerometer can play an important role in adjusting parameters, setting the SIR and detecting characteristics in the PM rate response.

Assessment of adaptive rate response provided by accelerometer, minute ventilation and dual sensor compared with normal sinus rhythm during exercise: a self-controlled study in chronotropically competent subjects

Background:

Dual sensor (DS) for rate adaption was supposed to be more physiological. To evaluate its superiority, the DS (accelerometer [ACC] and minute ventilation [MV]) and normal sinus rate response were compared in a self-controlled way during exercise treadmill testing.

Methods:

This self-controlled study was performed in atrioventricular block patients with normal sinus function who met the indications of pacemaker implant. Twenty-one patients came to the 1-month follow-up visit. Patients performed a treadmill test 1-month post implant while programmed in DDDR and sensor passive mode. For these patients, sensor response factors were left at default settings (ACC = 8, MV = 3) and sensor indicated rates (SIRs) for DS, ACC and MV sensor were retrieved from the pacemaker memories, along with measured sinus node (SN) rates from the beginning to 1-minute after the end of the treadmill test, and compared among study groups. Repeated measures analysis of variance and profile analysis, as well as variance analysis of randomized block designs, were used for statistical analysis.

Results:

Fifteen patients (15/21) were determined to be chronotropically competent. The mean differences between DS SIRs and intrinsic sinus rates during treadmill testing were smaller than those for ACC and MV sensor (mean difference between SIR and SN rate: ACC vs. SN, MV vs. SN, DS vs. SN, respectively, 34.84, 17.60, 16.15 beats/min), though no sensors could mimic sinus rates under the default settings for sensor response factor (ACC vs. SN P-adjusted < 0.001; MV vs. SN P-adjusted = 0.002; DS vs. SN P-adjusted = 0.005). However, both in the range of 1^st minute and first 3 minutes of exercise, only the DS SIR profile did not differ from sinus rates (P-adjusted = 0.09, 0.90, respectively).

Conclusions:

The DS under default settings provides more physiological rate response during physical activity than the corresponding single sensors (ACC or MV sensor). Further study is needed to determine if individual optimization would further improve adaptive performance of the DS.

Usefulness of hemodynamic sensors for physiologic cardiac pacing in heart failure patients

The rate adaptive sensors applied to cardiac pacing should respond as promptly as the normal sinus node with an highly specific and sensitive detection of the need of increasing heart rate. Sensors operating alone may not provide optimal heart responsiveness: central venous pH sensing, variations in the oxygen content of mixed venous blood, QT interval, breathing rate and pulmonary minute ventilation monitored by thoracic impedance variations, activity sensors. Using sensors that have different attributes but that work in a complementary manners offers distinct advantages. However, complicated sensors interactions may occur. Hemodynamic sensors detect changes in the hemodynamic performances of the heart, which partially depends on the autonomic nervous system-induced inotropic regulation of myocardial fibers. Specific hemodynamic sensors have been designed to measure different expression of the cardiac contraction strength: Peak Endocardial Acceleration (PEA), Closed Loop Stimulation (CLS) and TransValvular Impedance (TVI), guided by intraventricular impedance variations. Rate-responsive pacing is just one of the potential applications of hemodynamic sensors in implantable pacemakers. Other issues discussed in the paper include: hemodynamic monitoring for the optimal programmation and follow up of patients with cardiac resynchronization therapy; hemodynamic deterioration impact of tachyarrhythmias; hemodynamic upper rate limit control; monitoring and prevention of vasovagal malignant syncopes.

Design and rationale of the assessment of proper physiologic response with rate adaptive pacing driven by minute ventilation or accelerometer (APPROPRIATE) trial

Rate-adaptive sensors are designed to restore a physiologic heart rate response to activity, in particular for patients that have chronotropic incompetence (CI). Limited data exist comparing two primary types of sensors; an accelerometer (XL) sensor which detects activity or motion and a minute ventilation (MV) sensor, which detects the product of respiration rate and tidal volume. The APPROPRIATE study will evaluate the MV sensor compared with the XL sensor for superiority in improving functional capacity (peak VO(2)) in pacemaker patients that have CI. This study is a double-blind, randomized, two-arm trial that will enroll approximately 1,000 pacemaker patients. Patients will complete a 6-min walk test at the 2-week visit to screen for potential CI. Those projected to have CI will advance to a 1-month visit. At the 1-month visit, final determination of CI will be done by completing a peak exercise treadmill test while the pacemaker is programmed to DDDR with the device sensors set to passive. Patients failing to meet the study criteria for CI will not continue further in the trial. Patients that demonstrate CI will be randomized to program their rate-adaptive sensors to either MV or XL in a 1:1 ratio. The rate-adaptive sensor will be optimized for each patient using a short walk to determine the appropriate response factor. At a 2-month visit, patients will complete a CPX test with the rate-adaptive sensors in their randomized setting.

The restoration of chronotropic competence in heart failure patients with normal ejection fraction (RESET) study: rationale and design

BACKGROUND

Heart failure with preserved ejection fraction (HFpEF) is the predominant form of heart failure among the elderly and in women. However, there are few if any evidence-based therapeutic options for HFpEF. The chief complaint of HFpEF is reduced tolerance to physical exertion. Recent data revealed that 1 potential mechanism of exertional intolerance in HFpEF patients is inadequate chronotropic response. Although there is considerable evidence demonstrating the benefits of rate-adaptive pacing (RAP) provided from implantable cardiac devices in patients with an impaired chronotropic response, the effect of RAP in HFpEF is unknown.

METHODS AND RESULTS

The Restoration of Chronotropic CompEtence in Heart Failure PatientS with Normal Ejection FracTion (RESET) study is a prospective, multicenter, double-blind, randomized with stratification, study assessing the effect of RAP on peak oxygen consumption and quality of life. RAP therapy will be evaluated in a crossover paired fashion for each patient within each study stratum. Study strata are based on patient beta-blocker usage at time of enrollment. The study is powered to assess the impact of pacing independently in both strata.

CONCLUSIONS

The RESET study seeks to evaluate the potential benefit of RAP in patients with symptomatic mild to moderate HFpEF and chronotropic impairment. Study enrollment began in July 2008.

A blended sensor restores chronotropic response more favorably than an accelerometer alone in pacemaker patients: the LIFE study results

BACKGROUND

Adaptive rate sensors used in permanent pacemakers incorporate an accelerometer (XL) to increase heart rate with activity. Limited data exists regarding the relative benefit of a blended sensor (BS) (XL and minute ventilation) versus XL alone in restoring chronotropic response (CR) in chronotropically incompetent (CI) patients.

METHODS

One thousand five hundred thirty-eight patients from the limiting chronotropic incompetence for pacemaker recipients (LIFE) study were implanted with a pacemaker and 1,256 patients had data collected at 1 month. Patients performed a treadmill test 1-month postimplant while programmed in nonrate responsive mode (DDD-60) to determine CI. Only patients who completed at least three exercise stages and achieved a peak perceived exertion >or=16 were included in the analyses. The metabolic chronotropic relationship (MCR) slope was used to evaluate CR in 547 patients. Patients were randomized to XL or BS with a conservative fixed rate response factor (XL = 8, MV = 4). CI patients performed a follow-up 6-month treadmill test.

RESULTS

CI prevalence in this patient population (n = 547) was 34%. No differences in baseline characteristics existed between groups. Although both groups showed significant within-group improvements in MCR slope from 1 to 6 months (both P < 0.001), the BS group had a significantly higher MCR slope at 6 months compared to the XL group (P = 0.011). Improvement in quality of life (QOL) did not differ between groups.

CONCLUSIONS

In this general pacemaker population with CI, a BS programmed empirically restores CR more favorably than an XL sensor programmed nominally. Further studies are needed to determine if individual sensor optimization would lead to improvement in functional capacity, higher MCR slopes, and QOL.

The contribution of rate adaptive pacing with single or dual sensors to health-related quality of life

AIMS

The characteristics of sensors to perform rate adaptive pacing are well established but whether their contribution improves health-related quality of life (QoL) remains disputable. To compare the effects on QoL with an integrated dual sensor [minute ventilation (MV) and acceleration, TT sensor] with a single MV sensor, and with no rate adaptive pacing.

METHODS AND RESULTS

This Dutch multi centre, prospective, single- (patient) blind study was performed in patients after first pacemaker (PM) implant for sick sinus syndrome or AV block. After a 3-month 'sensor off'-period following DDD PM implantation, where the latter 2 months permitted the MV sensor to learn the intrinsic rhythm, a 2-month period of DDDR with TT sensor or 2 months of DDDR with MV sensor, subsequently the two modes were crossed over. Quality of life was determined with Aquarel, the disease-specific instrument for PM patients. Heart rate, percentages of sensor driven and intrinsic rhythm were retrieved from PM memories. Sixty-four patients completed the 7-month study. In sick sinus patients, percentages of sensor-driven pacing occurred significantly more frequently than in AV block patients After implant QoL improved significantly: before 71.3 and after 83.5% (P < 0.001) measured with Aquarel and in 3 of 9 SF-36 scales, but no significant additive QoL benefit with dual or MV sensor pacing was observed. Pacing diagnosis, percentages of rate adaptive pacing, and heart rate influencing medication did not influence this result.

CONCLUSION

Pacemaker implantation strongly improves QoL, but neither single- nor dual- sensor-driven pacing offered additional improvement in QoL during the initial 8 months after the first PM implant.

Is a Dual-Sensor Pacemaker Appropriate in Patients with Sino-Atrial Disease? Results from the DUSISLOG Study

BACKGROUND

Rate-responsive pacemakers (PMs) are often supplied with accelerometer (XL) and minute ventilation (MV) sensors to provide a physiologic rate response according to patient needs. No information is available about the real benefit of dual-sensor rate-responsive pacing on the daily life of patients.

METHODS

DUSISLOG (Dual Sensor vs Single Sensor comparison using patient activity LOGbook) is a two-arm prospective, randomized, multicenter study that enrolled 105 patients who received a rate-responsive PM (Insignia), Guidant Corp.). After 1 month of DDD pacing at 60 ppm lower rate, a single sensor (XL or MV, randomized) was activated for 3 months at the manufacturer's suggested nominal settings, followed by a 3-month period with dual sensors optimized with automatic response. During the last month of each period, the following data concerning patient physical activity were retrieved from PM diagnostics (Activity Log): mean percentage of physical activity, mean intensity of activity. Quality of life (QoL) scores and 6-minute walk test (WT) were also recorded.

RESULTS

Single-sensor rate-responsive pacing resulted in symptomatic benefit equally with XL and MV sensors while no additional benefit was found using dual sensor. In a subgroup analysis, patients (17%) with marked chronotropic incompetence and with 0% atrial sensing received benefits from single sensor with an additional advantage from sensor (QoL: +21 +/- 14% P < 0.05; WT: +17 +/- 7% P < 0.02).

CONCLUSION

In most patients with rate-responsive devices, a single sensor is sufficient to achieve a satisfactory rate response. A dual sensor combination and optimization provides an additional benefit only in a selected population with an advanced atrial chronotropic disease.