Long-Term Clinical Performance of a Central Venous Oxygen Saturation Sensor for Rate Adaptive Cardiac Pacing

Rate adaptive ventricular pacemakers using central venous oxygen saturation (O₂Sat) to control the pacing rate have been implanted in 14 patients (mean age 71 years), with a mean follow-up period of 44 months (range 2–63 months). In eight patients the pacemakers were replaced due to signs of battery depletion after an implant duration of 39–58 months. During bicycle exercise testing the O₂Sat decreased on average from 61%± 4% at rest to 36%± 4% (P < 0,0001) at peak exercise, and the maximum pacing rate was 122 ± 5 beats/min. The time delay until the O₂Sat bad dropped 10%, 65%, and 90% of the total reduction during exercise was 4.8 ± 0.9 seconds, 39.8 ± 3.8 seconds, and 71.3 ± 7.5 seconds, respectively. The O₂Sat decreased 9.4%± 2% (P <0.005) from resting supine to resting sitting. Oxygen breathing increased the telemetered O₂Sat from the pacemaker by 8.4 %± 1 % (P < 0.001). During follow-up the O₂Sats were relatively stable in 50% of the patients, but demonstrated significant fluctuations in the others. At 1-year invasive follow-up O₂Sat measured by the pacemaker decreased 22%± 2%, and in blood samples from the right ventricle 22%± 2% from rest to 3 minutes exercise at 25 watts. There was a significant correlation between O₂Sat measured by the pacemaker and in blood samples from right ventricle (n = 105; r = 0.73; P < 0.001). In two patients the O₂Sat dropped significantly during pneumonia. In another patient episodes of angina pectoris was associated with low O₂Sat and a concomitant fast pacing rate.     

Delayed Exercise Rate Response Kinetics Due to Sensor Cross-Checking in a Dual Sensor Rate Adaptive Pacing System: The Importance of Individual Sensor Programming

By cross-checking the relative sensor activation between a nonspecific and specific sensor during extraneous interference, a multisensor rate adaptive pacemaker may he able to limit inappropriate rate responses. The effects of activity (ACT) sensor programming on rate response kinetics of a QT and ACT dual sensor VVIR pacemaker with sensor cross-checking algorithm were studied in four patients with atrial fibrillation and complete heart block. The rate adaptive setting of each sensor was individually optimized, and an equal rate contribution for the QT and ACT sensors (QT = ACT) was used in the dual sensor VVIR mode. Three maximal treadmill exercise tests were performed in random order in three different VVIR modes driven by QT only, QT = ACT, and in the dual sensor mode with the most sensitive (low threshold) ACT setting. In the two dual sensor modes, the time for onset of rate response (delay time) was reduced (both < 15 sec) compared with QT only VVIR mode (233 ± 70 sec). However, the time to 50% of rate response in the low ACT threshold dual sensor mode was delayed compared with to QT = ACT (450 ± 110 [95% confidence interval 234–666] vs 311 ± 103 [109–513]sec, P < 0.05) and was similar to the QT only mode (401 ± 120 [l66–636]sec). The time to reach 90% of rate response was similar in the three modes tested. The resting activity counts registered by the ACT sensor were < 5 and 16 ± 2 counts/mm in the optimally programmed and low threshold ACT settings, respectively. This resulted in sensor cross-checking at rest in the overprogrammed dual sensor VVIR mode, thereby limiting the rate response. Thus, the combined sensor system provides a faster initial response to exercise than the QT only sensor. Programming the ACT threshold to low will prevent this faster response because of sensor cross-checking.     

A New Mechanical Sensor for Detecting Body Activity and Posture, Suitable for Rate Responsive Pacing

In the past, thought about rate responsive pacing mainly focused on rate increase with exercise but did not consider that a rate increase with postural changes also is mandatory in order to prevent orthostatic reactions. A nightly decrease in pacemaker rate when the body is at rest and in a supine position is a further advantage for the patient's sleep and recovery. Therefore, we developed a sensor that could detect not only rest and body activity but also discriminate between a supine and an upright position. This sensor is a muiticontact tilt switch containing a small mercury ball, as shown in the left panel of the figure below. The principle of discrimination between rest and low and high body activity is realized by the movement of the mercury ball resulting from body motion, which causes openings and closures within the sensor as the ball touches the numerous sensor contacts. In the upright position, a distinct number of contacts at the bottom of the tilt switch are closed. In the supine position, there is no closure of the bottom contacts and a postural discrimination can he achieved. We studied 12 volunteers and 10 pacemaker patients with this new device both at rest and during physical exercise. The right panel of the figure illustrates that the contacts per second correlate to the increase of physical exercise, such as walking on the treadmill. Further studies with an external pacemaker containing a small sensor suitable to fit into the pacemaker are in preparation.     

Adaptive Rate Pacing Controlled by the Right Ventricular Preelection Interval: Clinical Experience With a Physiological Pacing System

In the Precept pacing system, the right ventricular intracardiac impedance waveform is used to evaluate either of two indicators of metabolic demand relative right ventricular stroke volume and preejection interval (PEI). PEI is known to reliably parallel contractility changes, which is reflective of physical and emotional stress. The stability and dynamic behavior of PEI were tested in ten patients with a Precept pacing system under various forms of exercise and during postural changes. Although significant patient-to-patient variability of the sensor values was observed, reflecting individual physiological differences, the chronic stability of PEI was excellent in the total device experience of 147 months. In all patients, PEI shortened significantly during bicycle ergometry from a mean value of 137.7 +/- 17.8 (range 96-162) to a mean value of 103.0 +/- 21.6 (range 92-109) (P less than 0.05). Low level bicycle exercise of short duration resulted in a prompt decrease in PEI and increase in pacing rate in all patients. There were no uniform postural responses overall, although some posture related rate changes were observed in two patients. We conclude that the first generation of a PEI based pacing system holds promise for adaptive rate pacing.     

Evaluation of a Dual Sensor Rate Responsive Pacing System Based on a New Concept

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.     

Quantitative Comparison of Rate Response and Oxygen Uptake Kinetics Between Different Sensor Modes in Multisensor Rate Adaptive Pacing

Although multisensor pacing may mitigate the inadequacy of rate adaptation in a single sensor system, the clinical role of multisensor driven rate adaptive pacing remains unclear. The cardiopulmonary performance of six patients (mean age 63.5 ± 10 years) who had undergone the implant of combined QT and activity VVIR (Topaz®) pacemakers was assessed during submaximal and maximal treadmill exercise with the rate response sensor randomly programmed to either single sensor mode. QT and activity (ACT), or dual sensor mode, with equal contribution of QT and ACT (QT = ACT). The rate of response, the proportionality, oxygen kinetics, and maximal exercise performance of the various sensor modes during exercise were measured and compared. The ACT sensor mode “overpaced” and the QT and QT = ACT sensor modes “underpaced” during the first three quartiles of exercise (P < 0.05). The ACT sensor mode also gave the fastest rate of response with the shortest delay (13 ± 1.5 sec vs 145 ± 58 sec and 41 ± 17 sec, P < 0.05), time to 50% rate response (39 ±2.7 sec vs 275 ± 48 sec and 203 ± 40 sec, P < 0.05), and time to 90% of rate response (107 ± 21 sec vs 375 ± 34 sec and 347 ± 34 sec, P < 0.05) and a smaller oxygen debt (0.87 ± 0.16 L vs 1.10 ± 0.2 L and 1.07 ± 0.18 L, P < 0.05) compared to the QTand QT = ACT sensor modes, respectively. These differences were most significant at low exercise workloads. Thus, different sensor combinations resuh in different rate response profiles and oxygen delivery, especially during low level exercise. However, the observed oxygen kinetics difference was workload dependent, and its clinical relevance remains to be tested. Despite the marked difference in exercise rate profile and oxygen kinetics, there was no difference in the maximal oxygen uptake, anaerobic threshold, and exercise duration between the various sensor modes during maximal exercise.     

Impact of Adaptive Rate Pacing Controlled by a Right Ventricular Impedance Sensor on Cardiac Output in Response to Exercise

COOK, L., et al. : Impact of Adaptive Rate Pacing Controlled by a Right Ventricular Impedance Sensor on Cardiac Output in Response to Exercise. This study examined the effects of adaptive rate pacing controlled by closed-loop right ventricular impedance sensing on exercise hemodynamics. Twelve patients in whom Biotronik INOS²⁺ pacemakers had been implanted 4–6 weeks earlier participated in the study. All patients completed two graded, symptom-limited exercise tests. The pacemaker was programmed to DDDR with an upper rate limit of 75–85% of the age-predicted maximum heart rate and a lower rate limit of 45–60 ppm. Heart rate was recorded continuously. An average of 5 beats during the last 10 seconds of each exercise stage was used in the analysis. Oxygen uptake (VO₂) was measured using open circuit spirometry. The VO₂ values from the final 15 seconds of each exercise stage were used for analysis. Stroke volume and cardiac output were measured during the last minute of each stage using impedance cardiography. The test-retest reliability of heart rate and cardiac output responses to graded exercise was assessed using repeated measures analysis of variance, for which the reliability coefficients were r = 0.993 and r = 0.954, respectively (P < 0.01). There were significant correlations (P < 0.01) between VO₂ and heart rate and between VO₂ and cardiac output, with correlation coefficients of r = 0.907 and r = 0.824, respectively. This method of adaptive rate pacing produced reliable, positive hemodynamic responses to graded exercise on a test-retest basis. (PACE 2003; 26:[Pt. II]:244–247)     

Clinical Observations with a Dual Sensor Rate Adaptive Single Chamber Pacemaker

The Topaz model 515 (Vitatron B.V.) is a dual sensor rate responsive pacemaker for single chamber stimulation. It can be driven by activity counts (ACT) and QT interval measurements. Inappropriate rate modulation due to one sensor can be corrected by "sensor cross-checking." It was implanted in ten patients (20-86 years) of whom seven had complete heart block and atrial arrhythmias. After implantation T-wave amplitude ranged from 0.9mV-3.5 mV. T-wave sensing ranged from 88%–99% in 9/10 patients at the follow-up of 3 weeks. Eight patients remained in default setting of the activity threshold, after evaluation with a short walking test. An exercise test was performed on all patients. In one test, QT sensing was marginal because of lead implantation in the right ventricular outflow tract. Therefore, this pacing rate was only modulated by ACT sensing. All others were tested with equal contribution of information from both sensors (ACT = QT). In 7/9, rate response was satisfactory. When the treadmill was repeated with ACT in five of these seven patients, rate generally accelerated too fast. In one patient the setting was adjusted to "QT > ACT," because of inappropriate acceleration due to activity sensing, in another it was adjusted to "QT < ACT" because of delayed response to activity. The pacing rate and the ACT during treadmill tests in "QT = ACT" mode were more closely correlated in the first 3 minutes, compared with the last 3 minutes. We feel that rate modulation with this new pacemaker is adequate. Sensor blending and sensor cross-checking are of clinical importance.     

Adaptive Rate Pacing Controlled by Right Ventricular Preejection Interval for Severe Refractory Orthostatic Hypotension

A 72-year-old African-American man with frequent recurrent syncope was found to have severe refractory orihostatic hypotension with concomitant supine hypertension. Pharmacotherupy was successful in controlling his supine hypertension but was unable to resolve his severe orihostatic hypotension. Temporary fixed rate tachypacing was only minimally effective in preventing syncope during upright tilt, while variable rate pacing based on degree of blood pressure fall was far superior. Following these observations, an adaptive rate pacing system controlled by right ventricular preejection interval was implanted (Precept DR Model 1200). The system adequately sensed the patient's fall in blood pressure when sitting or standing and augmented its rate accordingly, thus preventing syncope. While supine, the pacing rate fell to 60 ppm, thereby, avoiding an exacerbation of his concomitant supine hypertension. Over a 3-nionth follow-up period, he has had no further orthostatic or syncopal episodes. We conclude that adaptive rate pacing using right ventricular preejection interval may be an effective treatment for severe refractory orthostatic hypotension.     

Clinical Interest of a Sensor Driven Algorithm Limiting Ventricular Pacing Rate During Supraventricular Tachycardia in Dual Chamber Pacing

A sensor driven algorithm limiting ventricular pacing rate during supraventricular tachycardia (SVT) is included in a dual chamber rate modulated pacemaker sensitive to acceleration forces (Relay, 294-03, Intermedics Inc.). According to the intensity of concomitant exercise, the ventricular pacing rate is limited either to the programmed maximum pacing rate (MPR) or to an interim lower limit, called "conditional ventricular tracking limit" (CVTL). The MPR prevails over the CVTL when the sensor calculated pacing rate exceeds the minimal rate by more than 20 beats/mm. The purpose of the study is to determine the clinical safety and efficacy of this algorithm in patients with intermittent SVT. Method: a Relay was implanted in four patients with a bradycardia/tachycardia syndrome and in four patients with complete atrioventricular block (CAVB). All had episodes of paroxysmal atrial tachycardia. The units were programmed in DDDR: rate responsive parameters were adjusted by simulating the rate response during three levels of exercise to let the MPR override the CVTL only during strenuous exercise. Holter monitors and exercise testings were performed at 3-month follow-up. Results: in seven patients, Holter recordings showed Supraventricular arrhythmias at rest with a ventricular pacing rate limited to the CVTL. Appropriate rate increases during exercise testings were also demonstrated. Three devices had to be reprogrammed in DDIR tone patient suffering from nearly permanent atrial flutter and two patients not tolerating the CVTL pacing rate at rest). Conclusion: the CVTL algorithm is effective in protecting against high ventricular pacing rates during Supraventricular arrhythmias. It allows the selection of the DDDR mode even with a high MPR in patients with intermittent SVT.     

Initial Clinical Experience with a New Dual Sensor SSIR Pacemaker Controlled by Body Activity and Minute Ventilation

Fourteen patients were implanted with a single chamber dual sensor pacemaker (Legend Plus®) that measures minute ventilation (VE) via variations in impedance between a bipolar lead and the pacemaker case, and activity via a piezoelectric crystal bonded to the pacemaker case. Chronotropic incompetent patients were exercised an a treadmill and a bicycle in dual sensor mode. Activity only indicated pacing rate was measured using a strap-on pacemaker. Both implanted and strap on pacemakers were adjusted to yield a steady-state pacing rate of 100 beats/min during hall walk. Pacing rate, VE, and oxygen uptake (VO₂) were measured continuously. Linear curve fit analysis slopes for plots of VE versus pacing rate during exercise (1.33-1.49) compared favorably to values reported in normals. Peak pacing rates achieved for treadmill and bicycle testing for dual sensor mode were higher than activity mode alone. Slopes of heart rate to VE or VO₂ were not significantly different (P < 0.05) for dual sensor mode in contrast to activity alone. In conclusion, the Legend Plus dual sensor rate adaptive pacing therapy delivered pacing rates more proportional to VE and VO₂ under different types of exercise than rates indicated by a strap-on pacemaker in activity mode.     

Evaluation of a New Rate Adaptive Ventricular Pacemaker Controlled by Double Sensors

The LEGEND-PLUS, a new rate adaptive pacemaker that combines activity and minute ventilation sensing for automatic rate adaptation was implanted in the right ventricle (VVIR) in 11 patients (mean age 62 ± 9 years). Initial programming was performed using the Programmer Exercise Protocol (a 3-minute walk). This programming was evaluated by treadmill tests, up-stairs and down-stairs walking, and Holier recordings. Results: Following the final programming of LEGEND-PLUS, the mean upper activity rate was 102 ± 7 beats/rain (range 90–120 beats/min), while the mean upper minute ventilation rate was 125 ± 16 beats/min (range 100–150 beats/min). The mean rate responses during the exercise protocol and the final programming in minute ventilation and activity sensing modes were 5.4 ± 2.3 (range 1–9), versus 4 ± 2.4 (range 1–8; P < 0.01) and 7.6 ±1.1 (range 5–9), versus 7.5 ± 0.8 (range 6–9; P = 0.8), respectively. In the combined sensing mode, the acceleration rate was identical to the activity rate response and the deceleration rate mimicked the minute ventilation. Conclusion: Dual sensor VVIR pacemakers have the potential to improve rate adaptation to exercise. The rate response to exercise in patients fitted with activity and minute ventilation sensors, VVIR pacemakers closely mimics the physiological rate response.     

Closed Loop Control of Rate Adaptive Pacing: Clinical Assessment of a System Analyzing the Ventricular Depolarization Gradient

Closed loop control of rate adaptive pacing has theoretical advantages over current rate responsive pacemakers. The first available system (which senses the ventricular depolarization gradient) has been evaluated in ten patients. The pacing response to a variety of exercise and nonexercise stimuli was assessed. Response to isotonic exercise was prompt and proportional to the exertion involved while isometric exercise and mental stress produced obvious but more gradual increases in pacing rate. In seven patients, comparison between the intrinsic P wave and pacing rate showed a high correlation during exercise (r = 0.91) and mental activity (r = 0.87). Postural changes induced a paradoxical response. Closed loop rate responsive pacing based upon analysis of the ventricular depolarization gradient produces a fast and appropriate rate response to most physiological stimuli.     

The "Low Intensity Treadmill Exercise" Protocol for Appropriate Rate Adaptive Programming of Minute Ventilation Controlled Pacemakers

The objective of rate adaptive pacemakers that measure minute ventilation by tmnsthoracic impedance is to simulate the physiological relationship of the sensed signal to the sinus node response during exercise, thus achieving an appropriate matching of heart rate with patient effort. The purpose of this study was to determine the physiological relationship between heart rate and minute ventilation (HR/VE) during peak exercise testing in order to develop a database for appropriate rate adaptive slope programming of minute ventilation controlled pacemakers. Due to several clinical limitations of peak exercise testing, it was additionally determined whether the 35-watt “low intensity treadmill exercise” (LITE) protocol can be used as a substitute for peak exercise test using the “ramping incremental treadmill exercise” (RITE) protocol in order to assess the correct HR/VE slope below the anaerobic threshold. The stress tests were performed on a treadmill with the collection of breath-by-breath gas exchange. Linear regression analysis was used to determine the HR/VE slope below and above the anaerobic threshold and during the early, dynamic phase of low intensity exercise with the RITE and LITE protocols, respectively. The results of this testing in 41 healthy subjects demonstrated that the HR/VE relationship throughout treadmill exercise using the RITE protocol was not linear but curvilinear in nature, with a steeper HR/VE slope of 1.54 ± 0.51 below versus 1.15 ± 0.37 above the anaerobic threshold (P < 0.005). The HR/VE slope determined during the early, dynamic phase of the LITE protocol (1.58 ± 0.88) did not differ from the HR/VE slope from rest to anaerobic threshold obtained using the peak exercise RITE test (1.54 ± 0.51; P = 0.79), Rate adaptive pacing should simulate the curvilinear relationship between heart rate and minute ventilation from rest to peak exercise. The HR/VE slope determined during the early, dynamic phase of low intensity exercise represents the HR/VE slope derived from the RITE protocol below the anaerobic threshold. According to the peak exercise database, the slope above anaerobic threshold can easily be calculated as a percentage of the slope below the anaerobic threshold. The LITE protocol can, therefore, be effectively performed as a substitute for peak exercise stress tests to determine the correct pacemaker rate response factor in order to obtain a physiological heart rate to minute ventilation relationship for the appropriate matching of paced heart rate with patient effort.     

A Double-Blind Study of Submaximal Exercise Tolerance and Variation in Paced Rate in Atrial Synchronous Compared to Activity Sensor Modulated Ventricular Pacing

To assess the variation in paced rate during everyday activity and the importance of atrioventricular synchronization (AV synchrony) for submaximal exercise tolerance, atrial synchronous (DDD) and activity rate modulated ventricular (VVI,R) pacing were compared in 17 patients with high degree AV block. The patients were randomly assigned to either mode and evaluated by treadmill exercise to moderate exertion and by 24-hour Holter monitoring after 2 months in the DDD and VVI,R modes, respectively. At the end of the study, the patients were programmed to the pacing mode corresponding to the preferred study period. During the treadmill test, the mean exercise time to submaximal exertion (Borg 5/10), exertion ratings and respiratory rate did not differ between pacing modes despite a significantly lower ventricular rate in the VVI,R mode. The atrial rate during VVI,R pacing was significantly higher than the ventricular rate, but did not differ from the ventricular rate during DDD pacing. There was a diurnal variation in paced rate in both pacing modes. Paced ventricular rate was, however, higher and variation in paced rate greater in DDD compared to VVI,R pacing. Nine patients preferred the DDD mode, three patients preferred the VVI,R mode, while five subjects did not express any preference. The results from this study indicate that the variation in paced rate during activity sensor-driven VVI,R pacing does not match that during DDD pacing neither during everyday activities nor during submaximal treadmill exercise. Nevertheless, no differences in exercise time, Borg ratings, and respiratory rate during submaximal exercise were found. Thus, for most patients with high degree AV block, DDD and VVI,R pacing seem equally satisfactory for submaximal exercise.     

Physiological Principles of a New Method for Rate Responsive Pacing Using the Pre-ejection Interval

The pre-ejection interval (PEI) was measured in 30 patients during isotonic and isometric exercise, emotional stress, isoproterenol infusion, Valsalva maneuver, carotid massage, atropine injection and incremental pacing. In patients with complete AV block, the simultaneous atrial rate was used as a standard of comparison to assess the changes observed in PEI. The sensitivity, specificity, proportionality and speed of response were evaluated to determine the applicability of PEI for rate responsive pacing. PEI shortened promptly and proportionately to atrial cycle length with isotonic and isometric exercise, emotional stress, and isoproterenol (R values from 0.88 to 0.98, p < 0.001). It was neither affected by preload changes (Valsalva) nor by parasympathetic system (carotid massage and atropine). Incremental pacing had no effect in most of the patients but some showed a slight prolongation, similarly to what is observed with atrial cycle length. It is concluded that PEI is suitable for rate control in physiologically adaptive pacemakers.     

Multicenter Clinical Evaluation of a New SSIR Pacemaker

A multicenter clinical evaluation of Sorin Swing 100, a new SSIR pacemaker with a gravimetric sensor, was performed by seven different centers enrolling a total of 89 patients, 56 men and 33 women, mean age 73.1 years, for pacemaker implantion (73 patients) or pacemaker replacement (16 patients). Pacing mode was VVIR in 73 patients and AAIR in 16. The behavior of pacing rate was evaluated 3 months after the implant by performing a 24-hour Holter monitor, an exercise stress test, and tests for the assessment of mechanical external interference (MEI). A physiological behavior of the paced rate was always observed during Holter monitoring. In 52 completely paced patients mean diurnal, nocturnal, and maximal heart rate were, respectively, 74.9 ± 5.7 ppm, 58.1 ± 5.8 ppm, and 113.4 ± 12.7 ppm; a paced rate exceeding 100 ppm was reached on the average 5.6 times/Holter monitor. In all but two patients the sleep rate (55 ppm) was reached during the night or long resting time. During exercise stress test a direct correlation between the increase in pacing rate and the increase in workload was observed; the mean maximal heart rate reached in 49 completely paced patients was, respectively, 102.8 ± 9 ppm in 17 patients who accomplished stage 1, 116.2 ± 13.6 ppm in 28 patients who accomplished stage 2, and 133 ± 6.7 ppm in 10 patients who accomplished stage 3 of the Bruce protocol. MEI testing never increased the pacing rate over the noise rate (10 ppm over the basic rate). In only seven patients the results obtained suggested to change the nominal set up of the pacemaker. Our experience clearly indicates that Swing 100 is an effective, reliable, and easy to use SSIR pacemaker. The availability of the sleep rate allows a more physiological pattern of pacing rate and can lead to significant energy saving.     

Clinical Evaluation of a Dual Sensor, Rate Responsive Pacemaker

Dual sensor pacemakers should respond more appropriately during differing exercise modes than a single sensor device. The Topaz™ models 515 (QT and activity count [ACT] sensing) pacemaker shows appropriate rate response during treadmill exercise testing. We postulated that adjustments to relative sensor contribution should allow fine tuning of the onset of rate response. Eleven patients with this pacemaker were studied. Three standard exercise tests were performed with adjustment of sensor blending and activity threshold between each one. We also assessed the response to isometric exercise and a false positive activity signal. Results : Times to 100 ppm (3.7 ± 1.3, 4.4 ± 2.0, 5.3 ±1.5 mins), times to peak rate (6.1 ± 1.6, 5.6 ± 1.4, 6.5 ± 1.3 mins) and accelerations to peak (9.0 ± 2.4, 9.2 ± 5.3, 7.7 ± 2.8 ppm/min) were measured in all three different sensor settings (QT = ACT, QT 相似文献   

Clinical Evaluation of a Pacemaker Algorithm That Adjusts the Pacing Rate During Sleep Using Activity Variance

DURU, F., et al. : Clinical Evaluation of a Pacemaker Algorithm That Adjusts the Pacing Rate During Sleep Using Activity Variance. Even though rate responsive pacemakers are able to regulate pacing rates based on sensor activity, they are set with a minimum rate that is not adjusted to provide rate decreases during sleep. The aim of this study was to evaluate the performance of the “Sleep Rate” feature, as compared to patient diaries and a validated method that identifies sleep from wrist actigraphy. In 19 patients (15 men; age 69 ± 8 years ) with Pacesetter Trilogy DR+ pacemakers, the base rate and the sleep rate were set to 80 and 50 ppm, respectively. When the patients returned 2 days later, data recorded by the pacemaker and wrist actigraph were analyzed to find the agreement in corresponding sleep/wake periods. In 17 (89%) patients, the pacemaker went into the sleep mode. The total sleep time derived from actigraphy significantly exceeded the time during which the pacemaker was in sleep mode (1156.8 ± 83.4 vs 307.3 ± 77.2 minutes ). Frequent reversions out of the sleep mode limited the total sleep time derived from the pacemaker. Cumulative analysis of the pacemaker data showed that the maximum time in the sleep mode was 78 minutes, and exceeded 1 hour in six instances, 30 minutes in 32 instances, and 15 minutes in 83 instances. Epoch by epoch comparisons revealed a good agreement (93.6 ± 1.8% ) during wakefulness between the corresponding actigraph and pacemaker epochs. However, only 24.6 ± 3.7% of the corresponding epochs during sleep were identical, and the overall agreement was 54.4 ± 3.7% . Except for one patient who reported palpitations, patients did not suffer from a pacemaker rate change. The Sleep Rate feature provides rate reduction during sleep, while assuring rapid frequency response during physical activity. However, the current algorithm does not allow long periods of slow pacing rate during continuous sleep, possibly due to its conservative design and the presence of movement arousals, which has to be improved in future generation algorithms.