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Biomedical subjects

E Alt

Publications and source records attributed to E Alt.

At least 91 records · Page 5Linked to original sources
PubMed1988

A new rate-modulated pacemaker system optimized by combination of two sensors.

A new rate-modulated pacemaker system optimized by combination of two sensors is described. The parameter body activity and central venous blood temperature control the pacemaker rate. The specific characteristic of each parameter determines its role within the algorithm. While the motion sensor yields a fast reaction following the onset or a change of stress intensity, central venous blood temperature corresponds better to body metabolism. An indication of increased exercise from the motion sensor results in an accordingly rapid increase in the pacing rate. Unless this increased exercise is confirmed by an increase in central venous blood temperature within 2 or 3 minutes, the new motion level will be assumed to be the new baseline motion value and the pace rate will return to a basic pacing rate. Prolonged inappropriate responses are therefore avoided. Longer lasting exercise, fever and nonphysiological signals are recognized and handled safely. Exercise tests with five volunteers under various conditions showed pacing rate behavior that was close to normal.

Adult↗
PubMed1988

Which patient is most likely to benefit from a rate responsive pacemaker?

In order to provide information about indications for rate responsive pacing, we examined the exercise capacity of a typical collective of pacemaker patients. One hundred seven patients participated in the study, 50/107 (46.8%) suffered from sick sinus syndrome, 37/107 (34.6%) showed complete AV block, 12/107 (11.2%) had bradyarrhythmia and 8/107 (7.4%) had other diseases. All patients underwent treadmill exercise with increasing workloads up to the individual's maximum workload. We monitored heart rate, respiratory rate, workload, the subjective perception of stress according to the Borg scale, and the reason for the termination of exercise. Calculation of oxygen uptake was done according to an equation given by Givoni. During the tests, all implanted pacemakers have been programmed to VVI 70 mode. We found that all pacemaker patients showed a reduction of their exercise capacity compared to the age-related normal values. Particularly in patients with AV block or bradyarrhythmia, the maximum achievable workload often did not even reach levels of everyday activities such as going upstairs; patients with sick sinus syndrome showed slightly better exercise capability, probably due to the higher increase of average heart rate. Despite objective differences of maximum workload, all patients had the same subjective perception at the end of the tests; the course of respiratory rate indicated that all persons finished the tests in the range of individual maximum exercise capacity.(ABSTRACT TRUNCATED AT 250 WORDS)

Bradycardia↗
PubMed1988

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 multicontact 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 be 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.

Adult↗
PubMed1988

[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.

Aged↗
PubMed1988

First clinical results with a new temperature-controlled rate-responsive pacemaker. Comparison of Activitrax and Nova MR pacemakers with VVI/AAI pacing.

We examined the cardiopulmonary effects of maximum bicycle ergometer exercise in seven patients with implanted Intermedics Nova MR pacemakers for three types of pacing in a randomized sequence: VVI or AAI at 70 beats/min (SSI 70), rate-adaptive temperature-controlled pacing with the implanted Nova MR, and rate-adaptive activity-controlled pacing with a Medtronic Activitrax pacemaker taped to the chest wall, which triggered the implanted Nova MR in the VVT or AAT mode by skin electrodes. The maximum exercise tolerance was 67 W with SSI 70, 71 W with Activitrax pacing, and 91 W with Nova MR pacing; the maximum oxygen uptake as 17.6, 19.5, and 21.5 ml/min/kg, respectively. The highest heart rate achieved was 81 beats/min with SSI 70, 98 beats/min with the Activitrax, and 118 beats/min with the Nova MR on average; the mean rate increase from rest to maximum exercise was 11, 29, and 47 beats/min, respectively. With both rate-adaptive types of pacing (Nova MR and Activitrax), an increase in exercise tolerance and maximum heart rate could be achieved, but this increase was significantly more obvious with the temperature-controlled Nova MR than with the activity-controlled Activitrax. However, with a different form of exercise, for example, treadmill ergometry, the rate response of the Activitrax would presumably have been somewhat clearer.

Aged↗
PubMed1988

[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.

Adult↗
PubMed1987

Lead fracture in pacemaker patients.

We studied the incidence of lead fractures in 2,226 patients with a total follow-up period of 8,558 patient years. Lead fractures occurred in 100 out of 2,563 implanted leads (3.9%). This corresponds to an average rate of 1.2% per patient year. We found 62 out of 881 singlefilar coil leads fractured (7.0%), 20 out of 809 Siemens Elema 588 leads (2.5%) and only 6 out of 630 multifilar soil leads (1.0%). Lead fractures occurred at a significantly (p less than 0.05) higher rate in singlefilar coil leads than in Simens Elema 588 leads or in multifilar coil leads. Independent of the type of lead, a significantly (p less than 0.05) higher fracture rate was found with leads implanted through the internal jugular vein. Most fractures occurred either inside the pacemaker pocket or on the way from the connector to the venous entry. Only 7% of all fractures occurred within the vascular system. Patients with a second or third degree AV-block and a multifilar coil lead implanted showed a significantly (p less than 0.05) better survival rate compared to those with a singlefilar coil or a Siemens Elema 588 lead. In pacemaker-dependent patients a replacement of singlefilar coil leads might be considered.

Equipment Design↗
PubMed1987

Control of pacemaker rate by impedance-based respiratory minute ventilation.

Several studies have shown that the capability for exercise can be increased in patients with pacemakers by means of adjusting the rate. Respiration is one of the parameters considered for rate control. The aim of our study was to determine how respiratory parameters such as ventilation, tidal volume, and respiratory rate are capable of controlling the pacemaker rate, especially when measured indirectly by means of impedance plethysmography. We examined four volunteers and eight patients with implanted cardiac pacemakers using bicycle ergometry at increasing work loads. We recorded heart rate, uptake of oxygen, and ventilation directly (by pneumotachygraphy) and indirectly (by chest wall impedance plethysmography). A good correlation of directly to indirectly measured ventilation (r = 0.8687) was found. Our study suggests that respiratory minute volume is more appropriate for rate control of physiologic pacemakers than tidal volume or respiratory rate alone. Measurement by means of impedance plethysmography is sufficiently precise to be used for this purpose. Further studies must be conducted as to the optimum realization within an implantable device.

Adult↗
PubMed1987

[Heart valve replacement in patients over age 60: analysis of the peri- and postoperative course compared to patients under age 60].

During recent years, advances in cardiology and cardiac surgery have led to an increased number of older patients submitted for heart valve replacement. The following retrospective study analyses perioperative risk and long-term prognosis of 168 patients older than 60 years of age, compared with 942 patients younger than 60 years of age with heart valve replacement. There was no significant difference in 7-year actuarial survival, late mortality, late complications and postoperative functional improvement for both groups. However, early mortality was higher in patients over 60 years of age than in the group of patients under 60 years (7.9% vs. 4.5% from 1980-85, p less than 0.05), especially when multivalvular replacement was performed or the patients were in preoperative functional class NYHA IV. The results indicate that in patients over 60 years of age, heart valve replacement can be performed with a good long-term prognosis and a marked improvement in the quality of life. Early mortality can be reduced to an acceptable rate if the patient is operated in time.

Adolescent↗
PubMed1987

[Critical comparison of uni- and bipolar pacemaker systems].

More than 90% of all implanted pacemaker systems in Germany up to the present were unipolar. Stimulation and sensing therein, take place between the cathodal electrode tip and the anodal pacemaker. A relatively large chance of noise interference is allowed by the large distance between the two poles. The high sensitivity, at is needed for correct function, enables intra- and extracorporal noise signals to interfere. This disadvantage of unipolar systems is mainly avoided when using bipolar systems. Since both poles are situated close to each other within the heart, there is only a very small chance of notice interference. However, there are many arguments in favour of both systems. In recent years there has been a slight trend towards bipolar pacing. By reducing the well-known disadvantages of bipolar pacing, such as increased conductor resistivity, as inferior energy function, greater coil diameter and reduced handling, the beneficial effects of bipolar pacing--mostly the clear discrimination between physiological cardiac and extraneous signals--become more important. A new 3.2 mm universal connector (VS-1) might help to realize bipolar pacing more easily. In the future, a pacemaker system with unipolar pacing and simultaneously a bipolar sensing function, might help to increase safety in pacing.

Arrhythmias, Cardiac↗
PubMed1987

[Effect of respiration on variations of central venous blood temperature].

We examined the course of right ventricular blood temperature before, during and after treadmill exercise in three patients with implanted cardiac pacemakers, and in two healthy volunteers. Temperature measurements were performed with a specially developed 5F electrode with an incorporated thermistor (measurement accuracy: 1/100 degrees C). After electronic amplification, the temperature signals were recorded on a three-channel strip chart recorder, together with ECG and respiration (measured by impedance plethysmography). In one of the volunteers, blood flow in the jugular and femoral veins was recorded by Doppler sonography, before and after exercise. We observed a decrease in central venous blood temperature with inspiration and an increase with expiration before, during and after exercise. The amplitudes of the variations became smaller during exercise, reached a maximum immediately after exercise and returned to their resting values within a few minutes after the end of exercise. We suppose different distributions of venous blood flow in different phases of the respiratory cycle to be the reason for the respiration-induced variations in central venous blood temperature. Under exercise conditions, the influence of respiration on the blood flow in the larger veins is small compared to the influence of an increased cardiac output; at rest, respiration has a more pronounced effect on venous blood flow. The analysis of our blood flow measurements in the femoral and jugular veins supported this assumption.

Adult↗
PubMed1986

Measurement of right ventricular blood temperature during exercise as a means of rate control in physiological pacemakers.

Several biological parameters have been suggested for rate control in physiological pacemakers in the past. Up to now, measurements of central venous blood temperature have been mostly done on dogs. We studied central venous blood temperature and heart rate in 14 healthy volunteers under conditions of treadmill and bicycle exercise with different workloads. A custom-made 5F lead with a thermistor incorporated near the tip was placed at the right ventricle under fluoroscopic control. Temperature was recorded with an accuracy of 1/100 degrees C on a digital memory device at a sampling rate of 5-10 s. We found the increase in blood temperature to be not only a function of absolute workloads but also a function of the individual's maximum exercise tolerance. Independent of the absolute increase in heart rate and temperature at a given workload, the individual's relation of increase in temperature and heart rate was found to be highly correlating (r = 0.9095). At a load of 100 W, we found a mean increase in heart rate of 52 beats and of temperature of 0.57 degree C, at 150 W of 74 beats/min and 0.84 degree C. During, as well as after, the exercise, heart rate and temperature have a parallel course. According to our data, control of physiological pacemakers by means of central venous blood temperature is possible.

Blood↗
PubMed1986

Rate control of physiologic pacemakers by central venous blood temperature.

Heart rate and central venous blood temperature (CVT) were measured in 31 people with different exercise capacities by means of a thermistor integrated into a lead that was placed in the right ventricle. Bicycle ergometric and treadmill stress tests with increasing workloads were performed. The maximum increase in CVT with ergometric exercise was found to be 1.3 degrees C at 250 W in healthy young volunteers and 1.0 degrees C at 125 W in cardiac patients. Despite a relatively greater increase in CVT in the elderly patients compared with the volunteers, the correlation between the increase in CVT and that in heart rate at the end of each exercise stage was found to be very high (r = .9693 in volunteers and r = .9864 in cardiac patients), independent of physical fitness. Even with everyday activities such as walking there was a marked increase in CVT. Due to its close relationship to human metabolism, CVT represents a good parameter for physiologic control of pacing rate.

Adult↗
PubMed1985

Survival and follow-up after pacemaker implantation: a comparison of patients with sick sinus syndrome, complete heart block, and atrial fibrillation.

The number of patients receiving cardiac pacemakers for sick sinus syndrome (SSS) has increased considerably in recent years. The literature has suggested that patients with sick sinus syndrome have a shorter life expectancy with pacemaker therapy than patients with total heart block or atrial fibrillation. We studied the survival rate of 1,049 patients with complete heart block, 592 with sick sinus syndrome and 447 with atrial fibrillation. After 10 years we found a survival rate of 54.5% for patients paced for SSS, 34.4% for those with complete heart block, and 24.7% for those with atrial fibrillation (statistical significance: SSS--heart block: p less than 0.05; SSS--atrial fibrillation: p less than 0.01; heart block--atrial fibrillation: NS). Considering the calculated survival rates of a comparable normal population (i.e., 56.5%; 41.2%; 47.8%), the differences in survival expectancy are even more pronounced (SSS-normal: NS; heart block-normal p less than 0.05; atrial fibrillation-normal: p less than 0.05). For patients with sick sinus syndrome, the life expectancy parallels that of the general population, while that of patients with complete heart block or atrial fibrillation have a life expectancy that is considerably lower.

Adolescent↗
PubMed1984

[Cardiac arrhythmias and their clinical significance in mitral valve prolapse].

Among 160 patients with mitral-valve prolapse but no other illness there were 118 with cardiac arrhythmias. 30 had frequent or multifocal ventricular premature systoles, 21 had coupled ventricular extrasystoles, and seven had ventricular tachycardia. In six patients the prematurity index was under 1. Supraventricular premature systoles were registered in 56 patients, with seven each having paroxysmal atrial tachycardia and paroxysmal atrial flutter or fibrillation. Ventricular arrhythmias were significantly more frequent in late-systolic prolapse and with positive auscultation findings (systolic click or systolic murmur). Long-term ECG monitoring was more valuable than an exercise ECG. About half the patients with frequent arrhythmias had palpitations and rapid heart action. Coupled ventricular premature systoles and ventricular tachycardias, as well as R-on-T were relatively rare; our findings thus tend to suggest a relatively favourable prognosis for these arrhythmias.

Adolescent↗
PubMed1984

Regulation of pacing rate by variations of mixed venous oxygen saturation.

Right ventricular oxygen saturation (SO2) may be an ideal sensor for determining the rate of an implanted pacemaker. In order to prove this hypothesis, the obtained signals were optimally analyzed; determinations of SO2 at rest and during exercise were made in healthy volunteers and in patients with pacemakers; and an algorithm was developed for varying pacing rate as a function of measured SO2. The results suggest that this method may be applicable to the long-term implantee.

Arrhythmias, Cardiac↗
PubMed1984

Antiarrhythmic activity of esmolol (ASL-8052)--a novel ultra-short acting beta-adrenoreceptor blocking agent.

In a single-blind, placebo-controlled study, esmolol was administered intravenously to 12 patients with chronic atrial fibrillation. Esmolol produced a significant dose-dependent decrease in the ventricular rate without conversion to normal sinus rhythm in any of the patients. For most patients, a correlation was observed between the blood levels of esmolol and reductions in heart rate. There were no significant adverse effects. We conclude that esmolol is an effective and safe agent for the control of heart rate in patients with supraventricular tachycardia.

Adrenergic beta-Antagonists↗