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Biomedical subjects

A Wirtzfeld

Publications and source records attributed to A Wirtzfeld.

At least 19 recordsLinked to original sources
PubMed1992

Improved thrombolysis in acute myocardial infarction with front-loaded administration of alteplase: results of the rt-PA-APSAC patency study (TAPS)

Thrombolysis with recombinant tissue-type plasminogen activator (rt-PA) and anisoylated plasminogen streptokinase activator (APSAC) in myocardial infarction has been proved to reduce mortality. A new front-loaded infusion regimen of 100 mg of rt-PA with an initial bolus dose of 15 mg followed by an infusion of 50 mg over 30 min and 35 mg over 60 min has been reported to yield higher patency rates than those achieved with standard regimens of thrombolytic treatment. The effects of this front-loaded administration of rt-PA versus those obtained with APSAC on early patency and reocclusion of infarct-related coronary arteries were investigated in a randomized multicenter trial in 421 patients with acute myocardial infarction. Coronary angiography 90 min after the start of treatment revealed a patent infarct-related artery (Thrombolysis in Myocardial Infarction [TIMI] grade 2 or 3) in 84.4% of 199 patients given rt-PA versus 70.3% of 202 patients given APSAC (p = 0.0007). Early reocclusion within 24 to 48 h was documented in 10.3% of 174 patients given rt-PA versus 2.5% of 163 patients given APSAC. Late reocclusion within 21 days was observed in 2.6% of 152 patients given rt-PA versus 6.3% of 159 patients given APSAC. There were 5 in-hospital deaths (2.4%) in the rt-PA group and 17 deaths (8.1%) in the APSAC group (p = 0.0095). The reinfarction rate was 3.8% and 4.8%, respectively. Peak serum creatine kinase and left ventricular ejection fraction at follow-up angiography were essentially identical in both treatment groups. There were more bleeding complications after APSAC (45% vs. 31%, p = 0.0019).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1990

Differences between atrial single chamber pacing (AAI) and ventricular single chamber pacing (VVI) with respect to prognosis and antiarrhythmic effect in patients with sick sinus syndrome.

Several studies suggest different effects of atrial (AAI) and ventricular single chamber pacing (VVI) for sick sinus syndrome with respect to the suppression of atrial tachycardias and to the prognosis. With this aspect in mind, we studied 222 patients with sick sinus syndrome, 110 of whom had been supplied with AAI systems, and 112 with VVI systems, in the period from January 1978 to December 1986. The mean observation period was 53 +/- 28 months. The cumulative 5-year survival rate was not significantly different in the two groups. After subgroups with comparable underlying diseases had been differentiated, patients with coronary heart disease showed a significantly higher survival rate (P less than 0.05) under AAI pacing, and the same was shown for patients with no underlying heart disease (P less than 0.02). The incidence of chronic atrial fibrillation was 6% in the AAI group and 19% in the VVI group. Patients with preexisting atrial tachyarrhythmias showed the lowest incidence of chronic atrial fibrillation under AAI pacing. Under VVI pacing this incidence was a function of the basic rate of the pacemaker systems. In conclusion, the pacing mode seems to have a prognostic importance in spite of all methodological difficulties. A suppressive effect of AAI pacing on atrial dysrhythmias can also be assumed.

Aged↗
PubMed1990

[30 years cardiac pacemaker therapy: a status evaluation].

Antibradycardiac pacemaker therapy has become established as one of the most effective forms of cardiological therapy for the indications AV-block, sick sinus syndrome, bradyarrhythmia, and hypersensitive carotid sinus. About 220,000 systems are implanted per year worldwide, about 32,000 in West Germany. Of the pacing modes, the fixed-rate ventricular single chamber systems (VVI) dominate with a share of almost 90%. Prognostic importance: For AV-block, the improvement of the prognosis by pacemaker therapy is unquestionable, since it increases the cumulative survival rates to 81% and 95% after 1 year and 50% to 65% after 5 years. For sick sinus syndrome, VVI-pacing proves to be a symptomatic measure, no prognostic importance can be proven. It is not conclusively clarified at present whether physiological pacing modes (AAI, DDD) have any such importance. Pacemaker therapy also has no prognostic importance for bradyarrhythmia. Hemodynamic importance: Numerous hemodynamic studies show that fixed-rate VVI-pacing fails to produce a long-term hemodynamic improvement for either an AV-block or a sick sinus syndrome. In sick sinus syndrome hemodynamic improvement can only be achieved by physiological pacing modes (AAI, DVI, DDD), whereby the increase in cardiac output is between 11% to 30%. For AV-block a long-term hemodynamic improvement can only be obtained by atrial triggered pacing modes (VAT, VDD, DDD); this is higher than the values of fixed-rate VVI-pacing by 7-25% at rest, or 10-40% under exercise. Similar results with improvements of the exercise hemodynamics between 22% and 66% are reported for rate-modulated single-chamber pacing (VVIR) for AV-block. Future trends: In the fourth decade of pacemaker therapy, developments point toward the "smart pacemaker", toward rate-modulated systems with combinations of parameters, toward rate-modulated dual-chamber systems and universal antibradycardiac and antitachycardiac systems.

Bradycardia↗
PubMed1989

[Ultra-high dose thrombolytic therapy with streptokinase in peripheral venous thrombosis].

56 patients with deep vein thrombosis (lower limb) and two patients with vena subclavia thrombosis were treated for six hours/day according to an ultrahigh dosage scheme (1,500,000 U/h streptokinase). An average number of three cycles was applied. Complete recanalization could be demonstrated in 23 patients (43%) with lower limb thrombosis, whereas a partial recanalization was demonstrable in 40% (22 patients). A complete thrombolysis could be achieved in one patient with vena subclavia thrombosis. Severe side effects were one intracerebral hemorrhage and one major lung embolism, causing death in both patients. Ultrahigh dosage thrombolysis with streptokinase is an effective therapeutic regimen and is considered to be an alternative to standard fibrinolytic procedures.

Adolescent↗
PubMed1989

Physical movement sensitive pacing: comparison of two "activity"-triggered pacing systems.

The Activitrax (A) and the Sensolog (S) pulse generator units were compared during bench tests and in patients both under ergometric conditions and during daily activities to determine the susceptibility of both systems to external noise. During the bench tests both pacemakers were mounted on a swingboard and subjected to controlled vibrational force. The patients were divided into two groups of 10 patients each, one group with A and the other with S units; the discriminating power of workload changes was examined under treadmill exercise. In six patients of each group the rate behavior of S and A during daily activities was recorded by Holter monitoring. During bench tests, S and A displayed a frequency-selective mode of operation between 2-70 Hz with the greatest sensitivity between 10-50 Hz. In patients, S showed a significantly higher discriminating power to changes in workload during treadmill exercise. According to y = 0.27x + 85.8 (r = 0.92) the relationship between the power and the pacing rate of S was linear, whereas with y = 0.04x + 89.8 (r = 0.2) the pacing rate of A was almost independent of the given power. The susceptibility to external noise occurring while riding in an auto, streetcar or train with rate increases between 7 ppm and 12 ppm did not significantly differ in both systems. Lying prone on the pacemakers produced brief (less than 1 min) rate increases of 38 ppm (S) and 18 ppm (A), respectively.

Cardiac Pacing, Artificial↗
PubMed1989

[Acute and chronic effects of UDCG 115 BS (pimobendan) in patients with advanced myocardial failure].

In a double-blind, placebo-controlled cross-over study acute hemodynamic effects of oral UDCG 115 BS (5 and 10 mg) were investigated in myocardial heart failure before (n = 16) and after (n = 13) chronic treatment (4 weeks). Before chronic treatment, UDCG 115 BS induced a similar increase in cardiac index with both doses (5 mg: from 2.4 +/- 0.7 to 3.5 +/- 0.7 l/min/m2, p less than 0.001; 10 mg: from 2.5 +/- 0.6 to 3.6 +/- 0.9 l/min/m2, p less than 0.001). Both right atrial pressure and pulmonary capillary wedge pressure were clearly reduced (p less than 0.001). Heart rate increased slightly only after 5 mg (p less than 0.05). Systemic vascular resistance was reduced (p less than 0.001), whereas mean blood pressure did not change. After chronic treatment (2 x 5 or 2 x 10 mg/d) and cessation of medication for 24 h there was no difference for control hemodynamic values as compared to placebo. Acute hemodynamic effects were considerably attenuated in comparison with the results obtained before chronic treatment. NYHA-classification, however, clearly (p less than 0.05) improved during administration of UDCG 115 BS as compared to placebo. Two patients died on placebo, whereas no patient expired on verum. This might indicate a therapeutic longterm effect of UDCG 115 BS, despite the observed development of partial tolerance.

Adult↗
PubMed1988

A new multisensor pacing system using stroke volume, respiratory rate, mixed venous oxygen saturation, and temperature, right atrial pressure, right ventricular pressure, and dP/dt.

A new multisensor pacing device using respiratory rate (RR), stroke volume (SV), oxygen saturation (SO2), temperature (T), right atrial pressure (RAP), right ventricular pressure (RVP) and right ventricular dP/dt, has been developed. It consists of a 7F multisensor catheter and an external pacing unit. It allows simultaneous recording of the input signals and the corresponding data can be compared among the different parameters under identical conditions. Furthermore, several parameters can be combined in such a way as to form a new combination better suitable for rate responsive pacing. The response of each parameter to exercise was studied in 12 healthy volunteers (mean age: 28 years). Exercise testing was carried out using a bicycle ergometer, with workloads up to 200 W. The dynamic characteristics, response and sensitivity to changes of workloads of each parameter were analyzed and compared to one another. SO2 proved to be a quick responding parameter (less than 10 sec) with higher sensitivity in the low exercise range (less than 75 W), T, on the other hand, responded slowly (greater than 30 sec) to exercise changes and had the highest sensitivity in the exercise range beyond 75 W. RR displayed a slow response (greater than 30 sec) and an adequate sensitivity was only found in the upper exercise range (greater than 100 W). SV reacted rapidly to workload changes (less than 10 sec) but showed poor sensitivity at all exercise levels. RAP, RVP and dP/dt displayed quick responses and constantly good sensitivity throughout the workload range. Furthermore, respiratory rate was easily derived from the RAP curve. Special algorithms were developed for each parameter so that pacing rate would reproduce sinus rate behavior. We found that SO2 and all pressure parameter imitated sinus rate response quite well. When using parameter combinations, SO2 and T proved to be superior. Five patients (mean age 68 years) with third degree AV-block were stimulated temporarily using this system. Compared to fixed rate stimulation (VVI 70), exercise performance improved, using SO2 as the input parameter for rate response, by 25% to 50%.

Adult↗
PubMed1988

The combined use of hysteresis and Holter functions improves diagnosis and therapy in patients with sick sinus syndrome.

We used the Holter functions of an implantable pacemaker in 12 patients with sino-atrial disease suffering from Adam-Stokes attacks to analyze the effects of hysteresis programming. The basic pacing rate of 50 ppm combined with a programmed hysteresis value of 10 to 20 ppm led to a drastic reduction in competition between paced and spontaneous beats: the percentage of paced beats decreased from 20.1% without hysteresis to 1.4% using 10 ppm hysteresis and the switches from sense to pace decreased from 2.0% to 0.06%. On the other hand, with hysteresis, no decrease in either the exercise tolerance or general well-being of the patients was observed.

Adams-Stokes Syndrome↗
PubMed1988

Analysis accuracy and susceptibility to faults of Holter functions in diagnostic pacemakers.

The analysis accuracy and susceptibility to faults of the additional diagnostic functions were tested in 16 patients (eight men, eight woman, average age 61.5 +/- 10.8 years, 14 VVI, 2 AAI) with diagnostic pacemakers (Quintech DPG 921). The average observation period was 19.7 months. With 109 follow-up intervals of an average duration of 87 +/- 39 days, this meant an observation period of 25.9 patient years. A stage-by-stage test structure over several intervals of time was applied in order to validate the data acquired through pacemaker Holter functions by means of control ECGs and mathematical test methods. The only fault to occur in the diagnostic functions was a loss of stored data. This was observed in 10% of the follow-up intervals and was on the average 28% (16%-38%) of the total events. Forty-four percent (7/16) of the pacemakers were affected by this malfunction. Our results show that the diagnostic data are certainly correctly acquired. The clinical value of the diagnostic functions is clearly reduced by this potential loss of data.

Adult↗
PubMed1988

First clinical experience with an oxygen saturation controlled pacemaker in man.

This article describes the characteristics of a new implantable pacemaker controlled by right atrial oxygen saturation and reports the first clinical experience in man. During the observation period over 5 months, there was no evidence of malfunction due to tissue growth. The system's reaction to exercise changes proved to be quick (5 s to 17 s); decay times varied depending on the magnitude of the power previously performed. Under various exercise tests, the rate increase was linear to the stress load. Measurements of cardiac output showed the system's hemodynamic feedback and its potential self-optimization of pacing rate.

Aged↗
PubMed1988

[Body movement as pacemaker induction value: comparison of 2 activity-triggered pacemakers].

This article compares the rate behavior of the activity-triggered pacemakers, the Activitrax (A) and the Sensolog (S), during bench tests as well as in patients under defined ergometric conditions and during every day life with special reference to the susceptibility of both systems to external noise. In the bench tests both pacemakers were mounted on a swingbord and subjected to controlled vibrational force. In the first experiment the frequency, in the second experiment the energy was varied. In two groups, one with S, one with A implanted, each consisting of 10 patients, the discriminating power of workload changes was examined under defined treadmill exercise. Furthermore in 5 patients of each group the rate behavior of S and A under daily life conditions and during common environmental noise was registered using Holter-ECG. In the bench tests S and A displayed a frequency-selective mode of operation between 2 Hz and 70 Hz with the highest sensitivity (resonance frequency) at 10 Hz. In patients, S showed a significantly higher discriminating power to changes of workload under treadmill exercise. According to y = 0.27x + 85.8 (r = 0.92) the relationship between the pacing rate of S and the power was linear whereas with y = 0.04x + 89.8 (r = 0.2) the pacing rate of A was almost independent of the given power. The susceptibility to external noise occurring during riding a car, streetcar or train with rate increases between 7 ppm and 12 ppm did not significantly differ in both systems.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1988

[Accuracy of analysis and susceptibility to faults in ECG detection using pacemakers with diagnostic functions].

The accuracy of analysis and susceptibility to faults of additional diagnostic functions in pacemakers were tested in 16 patients (eight men, eight women, average age 61.5 +/- 10.8 years, 14 VVI, 2 AAI) with diagnostic pacemakers (Quintech DPG 921). The average observation period was 19.7 months. With 109 follow-up intervals this meant an observation period of 25.9 patient-years. A stage-by-stage test structure over several periods of time was used in order to validate the data acquired through pacemaker Holter functions by means of control ECGs and mathematical test methods. The only fault to occur in the diagnostic functions was a loss of stored data. This was observed in 10% of follow-up intervals and was, on average, 28% (16-38%) of the total events. 44% (7/16) of the pacemakers were affected by this malfunction. Our results show that the diagnostic data are certainly correctly acquired. The clinical value of the diagnostic functions is clearly reduced by this potential loss of data.

Adult↗
PubMed1988

[Holter functions in cardiac pacemakers: expanding diagnostic possibilities and their clinical relevance].

By encompassing diagnostic multifunctions, microprocessor equipped pulse generators represent a marked improvement in the field of diagnosis and treatment. In this sense, bioelectrical data can be recorded over long periods, up to years, making a continuous follow-up possible. Changes in basic cardiac rhythm, pacemaker malfunctions, effect of parameter programming, even the assessment of antiarrhythmic therapy are some information that could be acquired. The screening function is particularly valuable for detecting sporadic arrhythmias and intermittent pacemaker malfunction which would otherwise go undetected. The limitation of this system lies in the fact that it does not render information on morphology and lacks the chronological correlation between recorded events.

Arrhythmias, Cardiac↗
PubMed1987

Physiological pacing: present status and future developments.

With the increasing tendency to implant pacemakers not only for life-threatening bradycardias but also for improving cardiodynamics in patients with bradycardia, it soon became apparent that classical VVI pacing is not truly able to optimize circulatory performance. Experience has shown that with ventricular pacing augmentation of cardiac output takes place only initially but is not maintained on a long-term basis, exercise capacity remains markedly reduced, there is only an unsatisfactory influence on the degree and course of heart failure and, in an occasional patient, cardiac function may even deteriorate as compared to the situation prior to pacing. Because the disappointing hemodynamic effect of fixed rate ventricular stimulation was at least partly due to the "unphysiological" mode of pacing provided by those systems which fail to restore AV synchrony and to increase heart rate with changing metabolic requirements, so called physiological pacemakers were developed. These pacing systems either maintain AV-synchrony and/or reestablish some way to adapt the pacing rate (Table I). This study delineates the hemodynamics of the paced heart with special reference to the role of AV relationship and rate control; it describes the clinical experience with physiological pacing and provides some ideas leading to present and future developments for rate adaptive pacing systems.

Atrial Fibrillation↗
PubMed1987

[Stroke volume, central venous oxygen saturation and blood temperature as control parameters of frequency-adapted pacemaker stimulation].

In order to compare various physiological parameters under identical conditions and to evaluate the "optimal" combination of parameters for triggering a pacing system, a multisensor-catheter of 7 F size was developed. By this catheter placed in the right ventricular cavity, sinus rate (SR), mixed venous oxygen saturation (SO2), temperature (T) and stroke volume (SV) were continuously recorded in 7 volunteers. SR, T, SO2 and SV were analysed for their steady state relationships to workload (P) and for their dynamic characteristics during standardized exercise tests. During exercise the delay times of SR, SO2 and SV were less than 10 sec., whereas that of T was markedly longer ranging from 70 sec. at low exercise levels to 30 sec. at high levels (200 Watts). During recovery delay times of SR, SO2 and SV ranged from 5 to 10 sec., that of T ranged from 20 to 30 sec. The relationship of SR to the workload (0-200 W) performed was linear (r = 0.98), that of T was linear above 50 Watts (r = 0.92), that of SO2 followed an exponential function (r = 0.89). Initial changes of SV were independent (r = 0.02) of the extent of workload. The sensitivity (S = dV/dP) was calculated from the relationship of the parameters (V) measured to the level of exercise performed. SO2 was highly sensitive at the lower range of exercise (less than 75 W), T became constantly sensitive above 50 W, below 50 W the sensitivity of T was continuously decreasing. SR was constantly sensitive over the whole range of exercise (0-200 W), the initial change of SV was not sensitive to the extent of workload.

Adult↗
PubMed1986

Rate control with an external SO2 closed loop system.

In 20 volunteers (mean age 35.5 y) and 12 pacemaker patients (mean age 68.7 y), central venous oxygen saturation (SO2) was monitored continuously by means of an optical sensor integrated in an external transvenous pacing lead placed in the right ventricular cavity. From the SO2 signal recorded at rest and during various modalities of exercise, an algorithm for controlling pacing rate of an external pacing system was developed. An open loop system was used in the volunteers, allowing the comparison of the computed pacing rate with the individual intrinsic heart rate. There was an excellent correlation between the two frequencies as far as the dynamic characteristics and the steady state relationship were concerned. In five pacemaker patients who were stimulated via the external lead, a closed loop control of pacing rate was used. In one patient with a DDD pacemaker implanted for third degree AV-block, the rate response of the SO2 driven pacemaker was well in accordance with the rate attained with the implanted atrial triggered system. With both pacing modes, exercise capacity as determined on a symptom limited treadmill test was identical. In four patients (3 AV block III, 1 bradyarrhythmia) an improvement in exercise tolerance up to 65 percent could be demonstrated with the rate responsive pacing mode. In all patients, it could be shown that an autoregulating pacemaker system with SO2 is an open possibility.

Adult↗
PubMed1986

Mitral valve closure and left ventricular filling time in patients with VDD pacemakers. Assessment of the onset of left ventricular systole and the end of diastole.

The effect of mitral valve closure on left ventricular filling time and its relation to the onset of systole were assessed from mitral valve echocardiograms and simultaneous apex cardiograms in 21 normal subjects, 11 patients with left bundle branch block, and 19 patients with VDD pacemakers programmed for atrioventricular intervals of 50, 150, and 250 ms. The interval between the electrocardiograph Q wave and the apex cardiogram upstroke was similar in normal subjects and patients with left bundle branch block, but was significantly longer in patients with VDD pacemakers at all atrioventricular intervals. Similarly there was little difference in the time interval between the Q wave and mitral valve closure in normal individuals and patients with left bundle branch block but this was considerably delayed in VDD pacemaker patients with the atrioventricular interval set at 50 ms. With increasing atrioventricular intervals the mitral valve closed significantly earlier, whereas the onset of left ventricular systole and the timing of mitral valve opening remained unchanged. Thus as a result of earlier mitral valve closure left ventricular filling time decreased progressively as the atrioventricular interval was increased. Since the onset of left ventricular systole, with respect to left ventricular stimulation, is considerably delayed in VDD pacemaker patients a short atrioventricular interval is required in these patients to maintain the normal time relations between atrial and ventricular contraction and hence maximise left ventricular filling.

Adult↗