Therapeutic effect of a dualchamber pacemaker with the optimized program-control mode on long-qt syndrome

Objectives To explore the optimized program-control mode of a dual-chamber pacemaker combined withβ-blocker to treat congenital long QT syndrome(LQTS). Methods 12 LQTS patients in our hospital that still have symptoms despite use of regular drug therapies or that can not endure the therapies were implanted with DDD cardiac pacemaker.The QT/QTc intervals of those patients were measured at different pacing rates respectively.Their cardiac pacemakers were all programmed to selectively turn on and turn off some related functions at the pacing rate of 80 beats/min.The dosage ofβ-blockers was adjusted according to the patients’ PR intervals and blood pressures.The MACE and the cardiac function of the patients were recorded after operation.Results The measured QT / QTc interval decreased with the pacing rate increasing.The pacing rate of 80 beats/min can make QT/QTc interval basically normal. The MACE of the patients were statistically declined(P = 0.003) and no negative effect on cardiac function was found during the follow-up.Conclusions The optimized program-control mode of a dual-chamber pacemaker combined withβ-blocker to treat congenital LQTS are:to pace at the rate of 80 beats/min and program to turn off lag,sleep,automatic preventing PMT and automatic threshold-capture feature and turn on the PVC,rate adaptation and atrioventricular node priority function.     

双腔起搏器优化程控对长QT综合征的疗效影响

目的探讨双腔起搏器联合B受体阻滞剂治疗先天性长QT综合征（LQTS）的最优程控方式。方法12例正规药物治疗无效或无法耐受的LQTS患者植入DDD起搏器,分别测量不同频率起搏时QT／QTc间期的变化,然后以80次／min的频率起搏,选择性地程控开放或关闭起搏器的部分相关功能,并根据PR间期和血压情况调整B受体阻滞剂用量,随访患者植入术后心脏事件的发生情况和心功能变化情况。结果起搏频率越快,QT／QTC间期越短。80次／min频率起搏时QT／QTc间期可基本恢复正常,植入术后心脏事件发生次数明显减少（P〈0．01）,且对心功能无影响。结论双腔起搏器联合B受体阻滞剂治疗LQTS时,最优程控方式是：以80次／min的频率起搏并程控关闭滞后、睡眠、自动终止起搏器介导的心动过速和自动阈值夺获功能,开放设置室性早搏后反应、频率适应性和房室结优先功能。     

High incidence of pacemaker syndrome in patients with sinus node dysfunction treated with ventricular-based pacing in the Mode Selection Trial (MOST)

OBJECTIVES: We evaluated the incidence, predictors, and treatment of pacemaker syndrome in patients with sinus node dysfunction treated with ventricular-based (VVIR) pacing in the Mode Selection Trial (MOST). BACKGROUND: Pacemaker syndrome, or intolerance to VVIR pacing, consists of cardiovascular signs and symptoms induced by VVIR pacing. METHODS: The definition of pacemaker syndrome required that a patient with single-chamber VVIR pacing develop either congestive signs and symptoms associated with retrograde conduction during VVIR pacing or a >or=20 mm Hg reduction of systolic blood pressure during VVIR pacing, associated with reproducible symptoms of weakness, lightheadedness, or syncope. RESULTS: Of 996 patients randomized to VVIR pacing, 182 (18.3%) met criteria for pacemaker syndrome in follow-up. Pacemaker syndrome occurred early in most patients (13.8% at 6 months, 16.0% at 1 year, increasing to 19.7% at 4 years). Baseline univariate predictors of pacemaker syndrome included a lower sinus rate and higher programmed pacemaker rate. Previous heart failure, ejection fraction, and drop in systolic blood pressure with VVIR pacing at implantation did not predict the development of pacemaker syndrome. Post-implantation predictors of pacemaker syndrome were a higher percentage of paced beats, higher programmed low rate, and slower underlying spontaneous sinus rate. Quality of life decreased at the time of diagnosis of pacemaker syndrome and improved with reprogramming to atrial-based pacing. CONCLUSIONS: Severe pacemaker syndrome developed in nearly 20% of VVIR-paced patients and improved with reprogramming to the dual-chamber pacing mode. Because prediction of pacemaker syndrome is difficult, the only way to prevent pacemaker syndrome is to implant atrial-based pacemakers in all patients.     

Effect of right ventricular pacing on ventricular rhythm during atrial fibrillation

In 13 patients with atrial fibrillation, the effect of right ventricular pacing at various rates on spontaneous RR intervals was studied. Five hundred consecutive RR intervals were recorded and measured before and during varying right ventricular pacing rates. As anticipated, all RR intervals longer than the right ventricular pacing intervals were abolished. However, RR intervals shorter than the right ventricular pacing intervals were also eliminated. It is difficult to explain the elimination of RR intervals shorter than the pacing intervals with the accepted concepts concerning the mechanisms governing the rate and rhythm of the ventricular response to atrial fibrillation. An alternative explanation may be that during atrial fibrillation the atrioventricular node behaves as a nonprotected pacemaker that is electrotonically modulated by the chaotic atrial electrical activity. The result is a random ventricular rhythm. With right ventricular pacing, the automatic focus is depolarized by the retrogradely concealed conducted ventricular impulses, the short RR intervals are not generated as a consequence and the rhythm becomes pacemaker dependent.     

Doppler echocardiographic study of mitral and aortic flow at various rates and atrioventricular intervals in patients with dual chamber pacemakers

The aim of this study was to measure the changes in mitral and aortic blood flow induced by rate changes and different atrioventricular intervals in dual chamber pacemaker patients. Ten totally pacemaker dependant patients were studied under basal conditions, in double atrial and ventricular stimulation mode, by pulsed Doppler recordings of mitral and aortic flow, at three different pacing rates (80, 100 and 120/mn) and with three different atrioventricular intervals at each rate (short, 90 or 115 ms; medium, 165 or 190 ms; and long, 240 ms). The increase in pacing rate and prolongation of the atrioventricular interval significantly shortened the duration of mitral flow. Increasing the pacing rate induced a significant fall in stroke volume measured from the aortic flow. The optimal atrioventricular interval tended to shorten when the pacing rate was increased; a long atrioventricular interval had a deleterious effect on stroke volume compared with medium and short atrioventricular intervals; however, the difference between the short and medium atrioventricular intervals was not statistically significant even at 120 mn. These observations emphasise the hemodynamic advantages of shortening of the atrioventricular interval of dual chamber pacemakers when the pacing rate increases.     

Behavior of central venous blood temperature in short duration and repeated stress--possibilities for temperature controlled frequency-adapted pacemaker stimulation

Although an exercise-induced increase in blood temperature has been well-known for some time, there was still some doubt whether the change in central venous blood temperature with short-lasting and repetitive physical exercise can be measured and utilized by a temperature controlled pacing system. We studied the central venous blood temperature with short-lasting and repetitive exercise in ten healthy young volunteers and in ten pacemaker patients. The blood temperature was measured intracardially while they walked upstairs. A height of 20 m was covered within 100 +/- 5 s. An oxygen uptake of 27 ml/min/kg was calculated for this level of exercise. After walking upstairs once, the volunteers had an increase in central venous blood temperature of 0.3 degrees C and the pacemaker patients of 0.37 degrees C. After walking upstairs three times, the volunteers had an overall rise in blood temperature of 0.67 degrees C and the pacemaker patients of 0.86 degrees C. Thus, the central venous blood temperature shows a pronounced, measurable increase with short-lasting exercise as well. However, the rises in blood temperature accumulate with repetitive exercise, as the duration of exercise (100 s) when walking upstairs once is not sufficient for a new level of temperature to be reached according to the level of exercise. Thus, a temperature controlled pacing system should take these complex changes into consideration.     

心脏再同步治疗对心肌复极离散度的影响

目的观察心室不同位点起搏时心电图上心肌复极标志的变化,了解以双心室起搏技术为核心的心脏再同步治疗（CRT）对心肌复极离散的影响。方法 入选接受CRT植入的患者在起搏器植入后1周内记录12导联心电图,分别将起搏器程控为无起搏、右心室内膜下起搏（RV—EndoP）、左心室外膜起搏（LV—EpiP）及双心室同步起搏（BivP）四种不同状态并记录心电图。阅读不同起搏位点时的QRS时限、QT问期及TP-E时限。QTc用Bazett公式[QTc=实测QT／（RR）1／2]进行矫正。结果基线QYc为（489．2±51．2）ms,而RV—EndoP、LV—EpiP起搏导致QR明显延长[RV-EndoP（537．3±45．7）ms,P〈0．05;LV—EpiP（592．4±60．2）ms,P〈0．001],而BivP起搏为（491．3±52．7）ms,P〉0．05;基线TP．F（113．8±15．7）ms,RV-EndoP、LV—EpiP均导致TP-E明显延长[RV．EndoP（124．8±24．7）ms,P〈0．05;LV．EpiP（133．3±37．8）ms,P〈0．005],BivP时TP-E时限为（109．9±17．1）ms,有轻度缩短,但差异没有统计学意义（P〉0．05）。结论左心室外膜起搏可明显延长心肌复极离散指标;双心室同步起搏可减少由单纯左心室外膜起搏引起的复极离散度的增大。     

Evaluation by pulsed Doppler echocardiography of the atrial contribution to left ventricular filling in patients with DDD pacemakers

To evaluate the significance of the left atrial (LA) contribution to left ventricular (LV) filling in cardiac pacing, LV inflow velocity was recorded with pulsed Doppler echocardiography in 20 patients with a DDD pacemaker. The pacemaker was programmed to atrioventricular (AV) sequential pacing with AV intervals of 50, 100, 150, 200 and 250 ms, and then to VVI pacing at a fixed rate of 70 beats/min. To evaluate the relative changes of LV filling volume in individual patients, the percent change in time-velocity integral of LV inflow velocity in each pacing mode was calculated as the ratio to that of AV sequential pacing with an AV interval of 150 ms. To estimate the degree of LA contribution to LV filling, the ratio of time-velocity integral during LA ejection phase to that during total LV filling phase was measured at the optimal AV interval. The percent LV inflow volume in AV sequential pacing was 74% for an AV interval of 50 ms, 87% for 100 ms, 98% for 200 ms and 90% for 250 ms. The percent LV inflow volume in VVI pacing was 72%. The percent LV inflow volume at AV intervals of 150 ms was significantly greater than that at an AV interval of 50, 100 and 250 ms, and in VVI pacing (p less than 0.05). The degree of LA contribution to LV filling showed a positive correlation with the percent increase of LV inflow volume with mode conversion from VVI to AV sequential pacing (p less than 0.005) and also with age (p less than 0.005).(ABSTRACT TRUNCATED AT 250 WORDS)     

Adaptive Rate Pacing at Submaximal Exercise: The Importance of the Programmed Upper Rate

The contributions of rate response and different programmed upper rates to sub-maximal exercise were studied in 12 patients with implanted adaptive rate pacemakers (9 Meta, 3 Activitrax). Their median age was 69 years (range 33–80). All were paced from the right ventricle except for one patient with sinoatrial disease who received an atrial Meta pacemaker. In the constant rate pacing (SSI) mode, the reproducibility of a Submaximal stress test (maximum distance covered within a 12-minute walking test) was investigated by repeating the test three times. An initial training effect was obserbed between the first and the second test, but no further increase in walking distance occurred between the second and third test and the distances covered were highly reproducible (r = 0.99). The rate adaptive function was activated with the upper rate randomly programmed to 100, 125, 150, and 165 beats/min. Compared with exercise in the SSI mode, rate adaptive pacing with the upper rate programmed to 125 and 150 beats/min resulted in enhancement of exercise distance (4.7%± 1.2% and 4.4%± 1.2%, respectively, P < 0.005). Upper rates of 100 and 165 beats/min did not improve submaximal exercise performance, and at an upper rate of 165 beats/min, three patients developed complications (angina, dyspnea, and atrial fibrillation). It is concluded that the 12-minute walking test is a reproducible method to assess exercise capacity in pacemaker patients. Adaptive rate pacing improved exercise performance during daily activities, although the extent of the benefit appeared to be small and dependent on the programmed upper rate. An exercise test such as a 12-minute walking test should be performed before a high upper rate is programmed.     

可对情绪变化起反应的闭环频率适应性起搏器的临床应用

目的　目前应用以感知运动的传感器为基础的频率适应性起搏器,在患者发生情绪变化时不能够提高起搏频率,本组报道新近开发的可感知情绪变化的闭环频率适应性起搏器的临床应用。方法　７ 例患者,男性５ 例,女性２ 例,因窦房结变时功能障碍,植入双腔频率适应性起搏器,其传感器为感知心室电极周围血液及心肌阻抗的变化的闭环传感器,不仅在运动时,而且可在情绪激动时增加起搏频率。术后对患者在平卧体位进行紧张试验,以观察在患者情绪变化时起搏器的频率适应功能。测试以患者倒数数的方法使患者保持情绪紧张。结果　患者试验前,平均起搏频率为６４ｐｐｍ ,情绪紧张时起搏频率上升至平均８６ｐｐｍ 。结论　感知心肌阻抗变化的闭环频率适应性起搏器在患者情绪紧张时可有效地使起搏频率增加,满足生理需求     

Cardiac pacing in the long QT syndrome: review of available data and practical recommendations

A review of published data on cardiac pacing in the long QT syndrome (LQTS) is presented, in the hope that optimization of patient selection and pacemaker programming will prevent arrhythmic death. LQT3 patients may derive particular benefit from pacing because the dispersion of repolarization worsens steeply during bradycardia in this genotype. However, concluding that other genotypes will not benefit from pacing is premature. Pacing may be especially beneficial for patients with "pause-dependent" arrhythmias. Programming should include a sufficiently fast lower rate limit. Features that allow heart rate slowing beyond the lower rate limit or that may trigger pauses must be programmed "off" because pauses are proarrhythmic in this population. Pause-prevention pacing algorithms may be beneficial.     

Postextrasystolic potentiation: analysis of methods of induction

Studies were conducted in 15 patients with coronary artery disease to determine if the type of pacing used to induce an extrasystole had a bearing on subsequent postextrasystolic potentiation (PESP) and if the fact that these were evaluated in jeopardized or nonjeopardized portions of the ventricle altered the ability to assess PESP. Two types of pacing were used. In the first group, all beats in the test sequence (basic heart rate, extrasystole, and postextrasystole) were delivered from a programmed external pacemaker. This group was termed the "all-paced" (AP) group, and the postextrasystole was introduced before a compensatory pause could occur, so that loading conditions within the ventricle at the last regular beat and after the extrasystole were not different. In the second group, the extrasystole was coupled to the sensed intrinsic heart rate of the patient, and the postextrasystole was allowed to occur spontaneously. This group was termed the "sensed-paced" (SP) group. Despite differences in basic heart rates and postextrasystolic intervals between the two groups, comparable results were obtained with the two techniques. However, the postextrasystole in the SP group occurred much earlier than expected, probably due to intrinsic cardioacceleration during ventriculography. The net result was that loading conditions in this group before and after the extrasystole were also not different from each other. Results from the pacing techniques were not influenced by whether they were obtained from jeopardized or nonjeopardized segments.(ABSTRACT TRUNCATED AT 250 WORDS)     

Relation between QT interval and heart rate. New design of physiologically adaptive cardiac pacemaker.

The relation between QT interval and heart rate has been studied in a group of patients undergoing physiological exercise, in a group undergoing atrial pacing without exercise, and in a group with complete heart block undergoing exercise at a fixed ventricular rate controlled by cardiac pacing. The expected shortening in QT interval during physiological exercise is only in part the result of the intrinsic effect of increased rate, since patients undergoing atrial pacing to comparable rates show only a small decrease in measured QT interval and patients exercising at fixed rates in heart block exhibit a decreasing QT interval related to the independent atrial rate. QT interval changes appear mainly to be governed by factors extrinsic to heart rate. The physiological control of QT interval has been used to construct a cardiac pacemaker which senses the interval between the delivered stimulus and the evoked T wave, and uses the stimulus-evoked T wave interval to set the subsequent pacemaker escape interval. Thus physiological control of cardiac pacing rate, independent of atrial activity, using conventional unipolar lead systems is possible.     

Long-term efficacy of physiologic dual-chamber pacing in the treatment of end-stage idiopathic dilated cardiomyopathy.

The long-term efficacy of physiologic dual-chamber (DDD) pacing in the treatment of end-stage idiopathic dilated cardiomyopathy was evaluated in a longitudinal study of up to 5 years in 17 patients. The considerable clinical improvement achieved after implantation of a pacemaker programmed for DDD pacing at an atrioventricular delay of 100 ms was maintained throughout the follow-up period or until death and was associated with a consistent decrease in New York Heart Association class and an increase in left ventricular ejection fraction. Cardiothoracic ratio, heart rate and echocardiographic dimensions progressively decreased, and systolic and diastolic blood pressures increased. Median survival time was 22 months. During follow-up, 4 patients received donor hearts, 9 had a sudden death at home without defined cause or after a thromboembolic event, and 1 died from adenocarcinoma. Three patients survived the follow-up. No patient needed rehospitalization owing to a worsening of heart failure after pacemaker implantation. An interruption of pacing in DDD mode for 2 to 4 hours was followed within the first months by a marked decrease in left ventricular ejection fraction and an increase in cardiothoracic ratio and echocardiographic dimensions, but this response consistently decreased during follow-up. The data indicate that DDD pacing can be recommended as a useful tool in the long-term treatment of end-stage idiopathic dilated cardiomyopathy, with progressive improvement in cardiac function and a reduction of the dilatation of the left ventricle.     

Long-term follow-up of patients treated with the QT interval sensing rate-responsive pacemaker

Thirty-seven patients (mean age 70 years) with QT-interval sensing (TX) rate-responsive pacemakers were followed for a mean of 27 months. This pacemaker measures the QT interval of the paced beat and, if the QT shortens, the pacing rate increases according to a programmed relationship, the 'slope'. With TX pacing the heart rate was 56% and the exercise tolerance 15% higher than with fixed-rate ventricular-inhibited (VVI) pacing during exercise. Holter ECG monitoring showed a physiological rate variability. Six patients (16%) have died during follow-up, and programming to the VVI mode was necessary in six patients (16%). The remaining patients were alive with a subjectively adequate TX function at the end of follow-up. Including the five patients who were on TX pacing at the time of death, satisfactory TX pacing was obtained in 84% of the patients. Although the TX pacemaker has been reliable and provides an adequate rate response during exercise, complaints of worsening angina pectoris and the somewhat complicated programming of the device are problems with the current models.     

Acute effect of DDD versus VVI pacing on arterial distensibility

Pulse wave velocity (PWV) is a new technique and frequently used today to determine the elastic distensibility of great arteries. Increased arterial stiffness and PWV have been proposed as possible mechanisms in the initiation and/or progression and/or complications of atherosclerosis and cardiovascular disease. We evaluated the acute effect of two frequently used pacing modes (DDD vs. VVI) on arterial distensibility using PWV. METHODS: Seventeen patients (age, 56 +/- 14 years) implanted with DDD pacemakers were included in the study. All patients were pacemaker dependent and continuously paced at the programmed rate. PWV was measured first in DDD mode, and then the mode was switched to VVI, and PWV was measured again at the same programmed heart rate as in the DDD mode. RESULTs: Although systolic blood pressure significantly decreased from 129 +/- 18 to 119 +/- 16 mm Hg (p = 0.001) after switching the mode from DDD to VVI, diastolic blood pressure (81 +/- 12 vs. 80 +/- 13 mm Hg; p = 0.38) did not change. In addition, PWV significantly increased from 11 +/- 2.46 m/s in DDD mode to 11.29 +/- 2.43 m/s (p = 0.01) after having been programmed to VVI mode. CONCLUSIONS: Our results suggest that VVI pacing increases PWV, and therefore decreases arterial distensibility, and thus may contribute to the development and progression of atherosclerosis.     

Cardiopulmonary stress: control of the function of frequency variable pacemaker systems

Based on the linear relationship between cardiac output and oxygen uptake direct breath-to-breath gas exchange measurements during exercise allow accurate determinations of cardiopulmonary function. We used cardiopulmonary exercise testing to assess the physiologic benefit of rate response VVIR pacing in 17 patients with chronotropic incompetence. 13 patients had an activity-rate-response pacemaker, two patients had a temperature-controlled pacemaker and two patients a respiratory-dependent system. Exercise testing was performed with the pacemaker, either programmed to fixed rate VVI or to rate variable VVIR pacing. All patients were exercised on a bicycle using a ramp protocol with 10 to 20 watts/min increments. Maximal oxygen uptake and the anaerobic threshold were determined. Compared with findings in the VVI mode, rate response VVIR pacing increased maximal exercise heart rate from 74 +/- 10 to 118 +/- 21 bpm (p less than 0.001). This increase in heart rate was associated with an increase of maximal oxygen uptake from 14.3 +/- 5 to 18.3 +/- 6 ml/kg per min (p less than 0.04) and a delay of the anaerobic threshold to a higher oxygen consumption of 14.6 +/- 5 vs 10.6 +/- 5 ml/kg per min (p less than 0.04). The individual increase in oxygen uptake was a direct function of the change in exercise heart rate independent of the implanted pacing device. The improved aerobic capacity resulted in a 17% increase in exercise tolerance and a 19% increase of exercise time. Cardiopulmonary exercise testing appears to be a useful noninvasive technique to quantify the cardiopulmonary benefit of rate response pacing.     

不同起搏频率对清醒狗血流动力学的影响

本文在7条清醒狗上观察不同起搏频率时安静和自由活动状态下血流动力学的变化。结果表明,按需型起搏器的起搏频率最好选用正常状态下24小时的平均心率(90次/分),因为此时24小时平均动脉压和心房率的平均值都接近于正常时的数值。与一般常用的起搏频率(75次/分)相比,还具有提高心脏储备能力的优点,能减少活动时增加每搏输出量的负担,而且,心房率相对减少可以减少房室同时收缩而引起起搏综合征的可能性。     

Instructions to Authors

ABSTRACT. Programmable atrial inhibited pacemakers were implanted in two patients with orthostatic hypotension due to autonomic failure. They were paced at 95 beats/min during the day and programmed themselves to 55 beats at night. This treatment resulted in virtual disappearance of orthostatic symptoms during a two-year follow-up. Haemodynamic studies showed a mean increase in erect systolic blood pressure from 47 mmHg pre-implantation to 85 mmHg at nine months post-implant during pacing. Cardiac output averaged 3.0 1/min without pacing and 3.8 1/min with pacing at two investigations. Rapid heart rate and high supine blood pressure at night were avoided by programming the pacemaker.     

闭环式频率适应性起搏器对情绪刺激的反应

目的 比较情绪反应在起搏器程控为闭环刺激(CLS)和加速度计(DDDR)方式时心房起搏频率的变化.方法 共54例患者植入具有CLS和加速度计两种频率适应性算法的起搏器,比较分别将起搏器程控为CLS和DDDR方式时,患者情绪反应对心房起搏频率的影响.结果 随访3个月,有35例患者符合情绪反应测试要求,进行情绪反应测试.与将起搏器程控为DDDR方式比较,将起搏器程控为CLS方式时情绪反应引起的心房起搏频率相关性更好,平均心房起搏频率(70.57±4.80)次/min vs(61.72±3.68)次/min,(P<0.001).结论 闭环式频率适应性起搏器比体动方式频率适应性起搏器在情绪反应方面具有更好的心房起搏频率调节作用.