Cardiopulmonary stress test in variable frequency stimulation: a comparison of Activitrax and Nova-MR pacemakers in VVI/AAI stimulation

In seven patients with implanted intermedics NOVA MR pacemakers, we examined the cardiopulmonary effects of maximum bicycle ergometer exercise for three types of pacing in a randomized sequence: VVI or AAI at 70/min (SSI 70), rate adaptive temperature controlled with the implanted NOVA MR, and rate adaptive activity controlled by means of a Medtronic Activitrax pacemaker taped to the chest wall, which triggered the implanted Nova MR in the VVT or AAT mode via skin electrodes. The maximum exercise tolerance was 67 W with SSI 70, 71 W with Activitrax and 91 W with Nova MR. The maximum oxygen uptake was accordingly 17.6 ml/min/kg with SSI 70, 19.5 ml/min/kg with Activitrax, and 21.5 ml/min/kg with Nova MR. The highest heart rate reached was 81 beats/min with SSI 70,98 beats/min with Activitrax and 118 beats/min with Nova MR. The rate increase from rest to maximum exercise was 11 beats/min with SSI 70,29 beats/min with Activitrax and 47 beats/min with Nova MR. An increase in exercise tolerance and maximum heart rate could be achieved with both rate adaptive types of pacing, but significantly more clearly with the temperature controlled Nova MR than with the activity controlled Activitrax. However, using a different form of exercise, e.g. treadmill ergometry, the rate response of the Activitrax would presumably have been somewhat clearer.     

Single-Chamber Rate Adaptive Pacing

Ventricular rate adaptiie pacemaker are the pacing systems of choice in patients with atrioventricular block and permanent or persistent atrial arrhythmias. A number of different pacemaker models are available, relying on different sensors of activity or metabolic demand. None of the sensors are perfect, each having its own advantages and disadvantages. Rate adaptive pacing is possible in the atrium as well as the ventricle, and at rial systems have a role in the management of patients with a poor sinus node response to exercise (chronotropic incompetence). The major groups of rate adaptive pacemakers are discussed in the following article, together with indications for use and possible future developments.     

Optimum pacing mode for patients with angina pectoris

A within patient double blind prospective study of symptoms and exercise tolerance was designed to determine the preferred pacing mode in 10 patients with programmable dual chamber pacemakers who also had angina pectoris. Patients were randomly allocated to one month in each of the following modes: ventricular pacing at 70 beats/min (VVI) or atrioventricular synchronous upper rate 150 beats/min (DDD 150) or 100 beats/min (DDD 100). Medications were unchanged throughout the study; none was taking beta blockers. At the end of each month patients underwent an exercise test. During each month patients recorded symptoms and their preferred pacing mode. DDD 100 was the preferred mode (seven patients). There was significantly less chest pain with this mode than with either of the other modes. There were significantly more episodes of dizziness in VVI, and two patients who developed pacemaker syndrome were unable to complete the pacing period. Three patients developed angina during exercise testing in DDD 150. Atrial synchronous ventricular pacing is better than ventricular pacing for the control of symptoms in patients with angina pectoris provided that the upper atrial tracking rate is limited.     

Optimum pacing mode for patients with angina pectoris.

A within patient double blind prospective study of symptoms and exercise tolerance was designed to determine the preferred pacing mode in 10 patients with programmable dual chamber pacemakers who also had angina pectoris. Patients were randomly allocated to one month in each of the following modes: ventricular pacing at 70 beats/min (VVI) or atrioventricular synchronous upper rate 150 beats/min (DDD 150) or 100 beats/min (DDD 100). Medications were unchanged throughout the study; none was taking beta blockers. At the end of each month patients underwent an exercise test. During each month patients recorded symptoms and their preferred pacing mode. DDD 100 was the preferred mode (seven patients). There was significantly less chest pain with this mode than with either of the other modes. There were significantly more episodes of dizziness in VVI, and two patients who developed pacemaker syndrome were unable to complete the pacing period. Three patients developed angina during exercise testing in DDD 150. Atrial synchronous ventricular pacing is better than ventricular pacing for the control of symptoms in patients with angina pectoris provided that the upper atrial tracking rate is limited.     

Programming of Rate Responsive Pacemakers

Rate adaptive pacing adds a new dimension to pacemaker therapy. The possibility of near physiological pacing utilizing the piezoelectric sensor is now offered to a broad range of patients with varied clinical problems. Improved cardiac output during exercise increases exercise capabilities and patient satisfaction. Single-chamber rate adaptive pacing has been demonstrated to improve cardiac performance. The expansion of this technology into a dual-chamber pacing unit achieves the combined benefit of AV synchrony with synthesized chronotropic competence. The challenge in clinical practice is to construct an appropriate rate responsive regimen and then to confirm the adequacy and safety of the programmed parameters. Considerable experience with single- and dual-chamber rate adaptive pacemakers led us to develop a protocol for initial pacemaker selection, subsequent programming of these units, and confirmation of optimal function. A practical method for evaluation of rate adaptive pacemaker patients is outlined with programming guidelines.     

Rate-modulated cardiac pacing based on transthoracic impedance measurements of minute ventilation: correlation with exercise gas exchange

The relation of pacing rate to physiologic variables of metabolic demand was examined in 10 consecutive patients with a minute ventilation-sensing, rate-modulating ventricular pacemaker implanted for complete heart block. All patients had paroxysmal (seven patients) or chronic (three patients) atrial fibrillation and were referred for catheter ablation of the atrioventricular junction. Treadmill exercise testing with measurement of expired gas exchange and respiratory flow was performed before ablation and 4 weeks after pacemaker implantation, with the pacemaker programmed to both the fixed-rate VVI and rate-modulating minute ventilation VVIR pacing modes in random sequence. The relation of pacing rate to oxygen consumption (VO2), expired carbon dioxide concentration (VCO2), respiratory quotient, tidal volume, respiratory rate and minute ventilation was determined during exercise in the rate-modulating minute ventilation pacing mode. Pacing rate was highly correlated with minute ventilation (r = 0.89), respiratory quotient (r = 0.89), VCO2 (r = 0.87), tidal volume (r = 0.87), VO2 (r = 0.84) and respiratory rate (r = 0.84). The mean exercise duration increased from 8.3 +/- 2.8 min in the fixed rate pacing mode to 10.2 +/- 3.4 min in the rate-modulating, minute ventilation mode (p = 0.0001). The maximal VO2 increased from 13.4 +/- 3.4 to 16.3 +/- 4.1 cc/kg per min (p = 0.0004). The maximal heart rate achieved in the minute ventilation pacing mode was 136 +/- 9.7 beats/min, similar to that observed in the patient's intrinsic cardiac rhythm before ablation (134.9 +/- 30.1 beats/min, p = NS).(ABSTRACT TRUNCATED AT 250 WORDS)     

Single-chamber cardiac pacing with activity-initiated chronotropic response: evaluation by cardiopulmonary exercise testing

In this study, sequential cardiopulmonary exercise testing was used to assess the physiologic benefits of a single-chamber ventricular pacing system that utilizes a piezoceramic sensor to adjust heart rate by detecting "physical activity." An initial exercise test was conducted with the pacemaker programmed (based on a randomization table) to either the fixed rate (VVI, 70 beats/min) or rate-variable (VVI-Act) mode, and the results were compared with those obtained during a second exercise test in which the pacemaker was programmed to the alternate pacing mode. A 1.5 to 2 hr rest period was permitted between exercise tests, each of which consisted of a symptom-limited constant speed (3.0 mph) Balke protocol with 2 min stages commencing at 0.0% grade with increments of 2.5% at end of each stage. Compared with findings during fixed-rate VVI pacing, VVI-Act pacing was associated with greater exercise-induced positive chronotropic response (mean maximum heart rate VVI-Act 128 +/- 15.3 beats/min vs VVI 90 +/- 28.4 beats/min; p less than .01), prolongation of exercise duration (VVI-Act 10.2 +/- 3.8 min vs VVI 7.7 +/- 2.5 min; p less than .01), increased peak oxygen consumption (VVI-Act 1617 +/- 656 ml O2/min vs VVI 1325 +/- 451 ml O2/min; p less than .01), and onset of anaerobic threshold at a higher oxygen consumption (VVI-Act 1208 +/- 343 ml O2/min vs VVI 1064 +/- 377 ml O2/min: p less than .01). Additionally, of 44 comparable exercise stages tested in the two pacing modes, perceived exertion (assessed by a numerical grading system) was lower in 38 of 44 instances during VVI-Act compared with VVI pacing.(ABSTRACT TRUNCATED AT 250 WORDS)     

Shuttle walking test: a new approach for evaluating patients with pacemakers.

OBJECTIVE: To validate an incremental field walking test, the shuttle walking test, as a means of assessing pacing modes and to aid programming of rate responsive pacemakers. DESIGN: Three separate groups of patients were recruited. Reproducibility (n = 10) of the shuttle walking test was assessed by performing three consecutive tests. Comparison of the shuttle walking test with a 10 min walk was assessed in 20 patients. In the third group (n = 10) patients with rate responsive pacemakers were programmed to either VVI fixed rate 70 beats/min or VVIR with the optimal rate response to show the discriminative value of the test. SETTING: Pacing clinic in a regional cardiothoracic centre. PATIENTS: 30 patients with chronotropic competence and dual chamber pacemakers with varying functional capacity and 10 patients with rate responsive pacemakers. INTERVENTIONS: Continuous haemodynamic monitoring was obtained using an ambulatory nuclear monitor, the Capintec VEST. Two exercise tests either shuttle walking test or 10 min corridor walk. The shuttle walk is an incremental walking test conducted on a 10 m course where the walking speed is dictated by bleeps on an audio cassette. RESULTS: Reproducibility was demonstrated over three consecutive tests with mean (1 SD) exercise times of 7.6 (1.7) min, 7.7 (1.6), and 7.7 (1.7) min. During the shuttle walk the test patients walked for a mean of 8.3 (1.2) min producing peak relative cardiac outputs of 78 (21) end diastolic volume/min compared with 64.9 (17) end diastolic volume/min for the 10 min walk (P < 0.001); peak heart rates were 118 and 104 beats/min (P < 0.03) respectively. In the third group relative peak cardiac output was significantly greater in VVIR (70 (24) v VVI 52 (15) end diastolic volume/min) (P < 0.009) as were exercise times (VVIR 8.8 (1.3) min v VVI 8.1 (1.3) min) (P < 0.003). CONCLUSIONS: The shuttle walk is an easy test to administer, requiring little equipment. It produces a symptom limited maximal performance and will be a useful aid to pacemaker programming as it is reproducible and able to show differences in exercise capacity between pacing modes.     

The Activitrax rate responsive pacemaker system

Bipolar Medtronic Activitrax rate responsive pacemakers were implanted in 31 patients for ventricular (28) or atrial (3) pacing. Mean follow-up was 16 months (range 10 to 26). Twenty pacemakers were implanted after catheter ablation of the His bundle, 7 for sick sinus syndrome. 1 for atrioventricular block and 3 for sick sinus syndrome with atrioventricular block. A rate response value was selected that gave a pacing rate of about 100 pulses/min during walking. Of the 31 patients, all had 24-hour ambulatory electrocardiographic monitoring with diary, 11 walked a 20-minute circuit, including a flight of stairs, and 20 had a treadmill exercise test. In 9 patients the pacing rate could be compared with the underlying sinus rate during exercise and was seen to match it very closely. In 12 patients the pacing rate during car driving was found to be similar to the sinus rate of 5 volunteers under similar conditions (mean minimum and maximum rate was 80 and 99 pulses/min, respectively). No pacing-induced arrhythmias were seen during ambulatory electrocardiographic monitoring. At high pacing rates slightly irregular pacing intervals were sometimes observed, which was due to polarization sensing. Sporadically, 1 pacing interval shortened to the upper rate value, because of a known and now resolved timing anomaly. Neither anomaly was of clinical consequence and the first could be resolved by reprogramming.(ABSTRACT TRUNCATED AT 250 WORDS)     

Cardiopulmonary exercise test in patients with DDD pacemaker: report of two cases with increased exercise capacity by decreased ventricular tracking limit rate setting]

We reported 2 patients with complete A-V block with a DDD pacemaker whose exercise capacity was increased by decreased ventricular tracking limit rate setting (VTL) of their pacemakers. Cardiopulmonary exercise test was used for estimating exercise capacity. Case 1: A 15-year-old girl complained of fainting. Her electrocardiogram (ECG) revealed complete A-V block (atrial rates 100/min, ventricular rates 39/min). After implantation of a DDD pacemaker and the VTL setting at 152/min, her bradycardia disappeared, however, she complained of dyspnea after a few minutes' walk. We performed symptom-limited cardiopulmonary exercise test with a motor-driven treadmill. When the pacing rate reached VTL (152/min), ECG suddenly changed to approximately 2:1 pacing (80/min) and the patient complained of dyspnea. Concomitant rapid increases in VE, VCO2 and RQ suggested that dyspnea was caused by the marked change in pacing rates on VTL. With the lowered VTL (110/min), there was no rapid increase in VE, VCO2 and RQ, and dyspnea subsided when the pacing rate reached VTL. At the same time, the peak VO2 and exercise time were increased by 15% and 8%, respectively. Case 2: A 47-year-old man complained of syncope. His ECG revealed complete A-V block (atrial rates 100/min, ventricular rates 33/min). After a DDD pacemaker implantation (VTL: 150/min), he experienced dyspnea while walking up the stairs in his office. Like in Case 1, when the VTL was lowered from 150/min to 110/min, both the peak VO2 and exercise time were increased by 11%.(ABSTRACT TRUNCATED AT 250 WORDS)     

频率适应式起搏器的临床应用和生理性起搏效应

采用动态心电图和超声心动图观察植入频率适应式起搏器９０例患者的日常活动，并观察运动试验时起搏频率和运动耐量。结果显示：４１例起搏器依赖患者的运动持续时间和最大心输出量分别较非频率适应式起搏增加３７％（３４７±６３ｓＶＳ２４７±５３ｓ，Ｐ＜０．００１）和５２％（１０．２±２．１Ｌ／ｍｉｎＶＳ６．７±１．６Ｌ／ｍｉｎ，Ｐ＜０．０５）。提示频率适应式起搏器可明显改善患者的生活质量和运动耐量。笔者体会术前应通过活动平板试验，评估患者心脏变时功能，以恰当掌握适应证；术后用动态心电图监测起搏频率及症状，以合理调整频率适应参数。     

Exercise performance and beta-adrenergic blockade in patients with complete heart block treated with ventricular inhibited pacing.

The effect of beta-adrenergic blockade (propranolol) on exercise performance was studied in 15 patients (12 men and 3 women, mean age 70 years) with complete heart block treated with a ventricular-inhibited pacemaker (VVI). In a double-blind procedure, the patients were randomly given either 0.1 mg/kg of propranolol or saline solution i.v. before a first exercise test and vice versa before a second test. The interval between the tests was 24 hours. Nine patients were in sinus rhythm, 4 patients had atrial flutter, and 2 others had atrial fibrillation. The exercise capacity was on an average 11% lower with propranolol than with placebo (p less than 0.001). The most marked reductions (20 and 33%) were found in the two patients with atrial fibrillation. The atrial rate in patients with sinus rhythm was significantly lower with propranolol than placebo both at rest (68 vs. 83 beats/min, p less than 0.001) and at maximal work load (91 vs. 141 beats/min, p less than 0.001). The present findings show that beta blockade has negative effects on exercise capacity in patients with complete heart block treated with VVI pacemakers. This finding should be considered in the selection of drug treatment in patients with fixed rate pacing and concomitant hypertension and/or ischemic heart disease.     

Evaluation of six minute walking test in patients with single chamber rate responsive pacemakers.

OBJECTIVE--To validate a simplified exercise protocol (the six minute walk) as a means of evaluating pacing modes and rate responsive pacemakers. DESIGN--Two groups of patients with different pacemaker types (activity and dual sensor) were randomly assigned to four consecutive pacing settings (fixed rate--or VVI at 60, 85, and 110/min, and optimal rate response--or VVIR). A third group of elderly patients without arrhythmias or conduction disturbances formed a control population. SETTING--Ambulatory consultation for patients with a pacemaker in a tertiary referral centre for treatment of arrhythmias. SUBJECTS--16 patients with rate responsive pacemakers for complete heart block and limited functional capacity and 13 controls with normal chronotropic competence. INTERVENTIONS--Submaximal exercise protocol with 6 minutes walking and continuous recording of electrocardiogram. MAIN OUTCOME MEASURES--Achieved distance and scored degree of exertion during walking in the four settings in the patients with a pacemaker; differences in rate behaviour in VVIR mode between the two pacemaker types; comparison of the pacing rate with the heart rate of the control population. RESULTS--The six minute walk was performed better in VVIR than VVI 60. In VVI 85 the distance was also significantly longer than in VVI 60. The rise in pacing rate of activity pacemakers was steeper than that of the dual sensor pacemakers and differed from the heart rate in the controls at 90 seconds. CONCLUSIONS--The studied test protocol was able to show differences in exercise capacity between pacing modes. Different rate responses between the evaluated sensor types could be established. The six minute walking test gives enough information to program and reprogram single chamber rate responsive pacemakers.     

Defining the optimum upper heart rate limit during exercise: a study in pacemaker patients with heart failure.

AIMS: There is no non-invasive method to determine the individual optimum of maximum exercise heart rate. Knowledge of this value is of particular interest in patients with structural heart disease who are prone to tachycardia intolerance. The purpose of this study was to define the optimal maximum heart rate using cardiopulmonary exercise testing and exercise Doppler echocardiography and to compare the results of both approaches. METHODS AND RESULTS: In 49 pacemaker patients with chronotropic incompetence, the optimum upper heart rate limit was determined using cardiopulmonary exercise testing and exercise Doppler echocardiography. The optimum upper rate limit was given by the highest pacing rate which still produced an increase in oxygen consumption, or by that pacing rate which was linked to the lowest value for the Doppler-derived myocardial performance index. In patients with normal left ventricular ejection fraction (>or=55%) the optimum upper rate limit was 86% of age-predicted maximum heart rate, in patients with left ventriuclar dysfunction (ejection fraction 相似文献   

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.     

Arrhythmia in patients with a DDD bicameral pacemaker

Dual chamber pacemakers, with coordinate atrial and ventricular sensing and stimulation (DDD), even if allowing "physiological" pacing, exhibited new and complicated arrhythmic manifestations, whose real frequency is still unascertained. In 65 patients (mean age 68 +/- 12 years), implanted with a DDD multiprogrammable device (15 pts. Medtronic Versatrax 7000 A, 50 pts. Pacesetter AFP 283), we carried out a 24 hours Holter monitoring while pacemaker was programmed with standard parameters. In a subset of 15 patients Holter monitoring was performed before and after pacemaker implantation. We evidenced: a) atrial sensing and/or pacing malfunction in 3 patients (4.5%); b) pacer-unrelated arrhythmias in 49 patients (75%): atrial extra beats 35 patients (54%), ventricular extra beats 23 patients (35%), non-sustained ventricular tachycardias 10 patients (15%), atrial tachyarrhythmias 8 patients (12%); c) supraventricular arrhythmias with PM-mediated high rate ventricular pacing in 12 patients (18%); d) PM induced and sustained endless loop tachycardias in 31 patients (47%); e) arrhythmias depending on over-sensing in 11 patients (17%): myopotential interferences 9 patients (14%), cross-talk ventricular pacing inhibition 2 patients (3%). The prevalence of ventricular arrhythmias was not different before and after the pacemaker implantation. The prevalence of atrial extrasystoles (53% versus 40%) and atrial tachyarrhythmias (26% versus 6%) decreased after the pacemaker implantation. Aimed reprogramming with progressive extension of atrial refractory period (from 250 to 400 msec and DDX) achieved disappearance of PM-endless loop tachycardias in 95%. Use of multi-programmability lowered the incidence and symptoms of most PM-related arrhythmias. Drug therapy was of choice in clinical arrhythmias unrelated to pacer.     

Usefulness of transcutaneous triggering of conventional implanted pulse generators by an activity-sensing pacemaker for predicting effectiveness of rate response pacing

A noninvasive procedure has been developed to assess effectiveness of activity-sensing rate response ventricular (VVIR) pacing systems in patients with implanted conventional fixed-rate ventricular (VVI) pacemakers capable of triggered mode operation (VVT). A VVIR pacemaker (activity threshold medium or low, rate response 6 to 10, upper rate 125 or 150 beats/min) was strapped to the chest wall (prepectoral area) of patients with previously implanted fixed-rate VVI pacemakers. In 17 of the 18 patients included in the study, the implanted pacemaker was capable of triggered mode operation (VVT). Triggering of the conventional pacemaker was achieved by reprogramming it to the VVT mode (high sensitivity, short refractory) and connecting the output of the "strapped-on" VVIR pacemaker (5 volts, 1.5-ms pulse width) to 2 standard cutaneous electrodes positioned so as to be in proximity to the implanted intracardiac electrode system. Patients underwent symptom-limited treadmill exercise tests during both VVI and VVIR pacing. Triggering conventional VVI pulse generators by a "strapped-on" VVIR pacing system proved feasible in 16 of 17 cases and improved overall heart rate response (fixed rate 86 +/- 22 vs VVIR 118 +/- 7 beats/min) and exercise duration (fixed rate 6.6 +/- 4.9 vs VVIR 10.1 +/- 4.8 minutes) (mean values for all patients studied during exercise testing). Triggering of a previously implanted permanent pacemaker by a strapped-on activity-triggered device may be useful to assess rate response pacing before implantation of a VVIR device in patients in whom elective pulse generator replacement is planned.     

Comparison of Permanent Left Ventricular and Biventricular Pacing in Patients with Heart Failure and Chronic Atrial Fibrillation: A Prospective Hemodynamic Study

BACKGROUND: Left ventricular pacing (LVP) and biventricular pacing (BVP) have been proposed as treatments for patients with advanced heart failure complicated by discoordinate contraction due to intraventricular conduction delay. For patients in sinus rhythm, BVP works in part by modulating the electronic atrial-ventricular time delay and thus optimizing contractile synchrony, the contribution of atrial systole, and reducing mitral regurgitation. However, little is known of the mechanisms of BVP in heart failure patients with drug-resistant chronic atrial fibrillation. HYPOTHESIS AND METHODS: LVP differs from BVP because hemodynamic and clinical improvement occurs in association with prolongation rather than shortening of the QRS duration. We sought to determine if LVP or BVP improves mechanical synchronization in the presence of atrial fibrillation. Thirteen patients with chronic atrial fibrillation, severe heart failure and QRS >or=140 ms received (after His bundle ablation) a pacemaker providing both LVP and BVP. The mean age was 62 +/- 6 years and left ventricular ejection fraction was 24 +/- 8%. After a baseline phase of one month with right ventricular pacing, all patients underwent in random order 2 phases of 2 months (LVP and BVP). At the end of each phase, an echocardiogram, a hemodynamic analysis at rest and during a 6-minute walking test and a cardio-pulmonary exercise test were performed. RESULTS: LVP and BVP provided similar performances at rest (p = ns). The 6-minute walking test revealed similar performances in both pacing modes but patients were significantly more symptomatic at the end of the test with LVP ( p = 0.035). The cardio-pulmonary exercise test showed higher performances with BVP (92 +/- 34 Watts) vs. LVP (77 +/- 23; p = 0.03). LVP was associated with significantly more premature ventricular complexes recorded during the 6 minute walking test (49 +/- 71) than BVP (10 +/- 23; p = 0.04). CONCLUSIONS: In this small series of patients with atrial fibrillation, congestive heart failure and a prolonged QRS duration, LVP and BVP provided similar hemodynamic effects at rest whereas BVP was associated with better hemodynamic effects during exercise and fewer premature ventricular complexes. Although the mechanisms for the observed differences are uncertain, it is possible that there is worsening of right ventricular function due to a rise in left-to-right electromechanical delay during exercise. Increased catecholamines release might contribute to the lower exercise tolerance and greater number of premature ventricular complexes recorded during exercise observed during LVP compared to BVP. RECOMMENDATIONS: Patients with atrial fibrillation, heart failure and QRS prolongation who are candidates for His-bundle ablation and cardiac resynchronization therapy may respond better to BVP rather than to LVP.     

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.     

Transesophageal echocardiography in combination with atrial stimulation for detection of ischemia-induced disorders of myocardial wall motion]

The diagnostic value of exercise echocardiography has been widely reported. In up to 20% of patients conventional transthoracic exercise echocardiography however is impossible due to impaired image quality related to exercise. In addition some patients will not be able to perform a conventional bicycle exercise test due to joint disease or peripheral vascular disease or a sufficient stress is not possible because of lack of patient motivation. In an attempt to overcome these limitations, a system has been developed which combines transesophageal echocardiography with simultaneous transesophageal atrial pacing via the same probe. Three circular silver pacing electrodes were installed at a distance of 7,9 and 12 cm from the tip of the echoscope. Square wave pulses of 10 ms and an intensity of 7 to 20 mA were delivered. After baseline recording at the patient's spontaneous heart rate, atrial pacing was initiated at a rate of 100 beats/min and increased stepwise every 2 min by 20 beats/min up to 85% of the age-predicted maximal heart rate. Pacing endpoints were designated to be the development of angina pectoris or dyspnea, persisting horizontal or downsloping ST-segment depression (0.2 mV 80 ms after the J-point in the 12-lead ECG) or the development of new segmental wall motion abnormalities. In a group of 50 patients with suspected coronary artery disease, coronary artery disease (luminal narrowing of more than 70% of at least one major vessel) was detected with high sensitivity (greater than 93%) and specificity (greater than 100%).(ABSTRACT TRUNCATED AT 250 WORDS)