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Biomedical subjects

E Alt

Publications and source records attributed to E Alt.

At least 55 records · Page 3Linked to original sources
PubMed1996

Initial experience with implantation of internal cardioverter/defibrillators under local anaesthesia by electrophysiologists.

This study was designed to evaluate the implantation of internal cardioverter/defibrillators under local anaesthesia by electrophysiologists and to compare this to our former experience of implants with general anaesthesia. Forty-seven internal cardioverter/defibrillators were implanted at our institution by electrophysiologists. Twenty-nine operations were performed under general anaesthesia (isoflurane 0.4-0.6%), and 18 under local anaesthesia (mepivacain 1%). The defibrillator leads were introduced by venotomy of the cephalic vein (n = 25), puncture of the subclavian vein (n = 17) or both (n = 5). All devices were implanted beneath the pectoral muscles. The mean operation time was 99 +/- 29 min. In the group with local anaesthesia the operation time was significantly shorter than with general anaesthesia (86 +/- 20 min vs 107 +/- 31 min; P = 0.027). The defibrillation threshold with biphasic shock application was below 24 J in all patients; thus, the implantation of an additional subcutaneous patch electrode was unnecessary. There were no major complications in either group. However, modifications were required in four patients: in one a set screw had to be re-tightened after delivery of an erroneous shock in the early postoperative phase; in another, device migration occurred several weeks after implantation, but no therapeutic intervention was required; in another, a rise in pacing threshold and partial sensing loss were noted ten days postoperatively; in the fourth, a minor pneumothorax occurred after subclavian puncture, but no further treatment was necessary. There was no intra-operative or postoperative mortality in either group. Implantation of internal cardioverter/defibrillators under local anaesthesia and mild sedation is feasible, and can be safely performed by electrophysiologists experienced in basic surgery. The newly developed smaller devices allow implantation in the subpectoral region, and with "active can' configuration and biphasic shock application, subcutaneous patch electrodes become unnecessary.

Adult↗
PubMed1996

Improving accelerometer-based rate adaptive pacing by means of second-generation signal processing.

Accelerometer-based rate adaptive pacing has gained widespread clinical use. Limitations exist for the distinction between walking upstairs and downstairs. It was the aim of this study to evaluate a new signal processing algorithm for more physiological rate adaptation. A custom-made pacemaker incorporating an accelerometer was randomly fixed to the left or right chest of 16 pacemaker patients (7 females, age: 64 +/- 11 years), 18 elderly study participants (6 females, age: 62 +/- 11 years), and 15 students (7 females age: 23 +/- 2 years). Study participants walked on level ground, upstairs and downstairs at five different step rates (72, 84, 96, 108, and 120 steps/min) controlled by an acoustic quartz metronome. The accelerometer signals, recorded on a portable data recorder, were analyzed with respect to frequency content, peak average of the mean acceleration, and morphology characteristics of the acceleration signal above and below zero baseline. By calculating the quotient of the signal's duration above and below zero baseline, a reliable discrimination between walking upstairs and downstairs was possible. A correction of the Leaky integrator signal by the new quotient yielded a more adequate rate adaptation to walking up and downstairs to represent at the patient's daily life activities. A more physiological rate adaptation can be achieved when using not only the accelerometer signal's amplitude, but applying additionally the morphology criterium of the acceleration signal's content in the positive and negative direction.

Acceleration↗
PubMed1996

Activity controlled cardiac pacemakers during stairwalking: a comparison of accelerometer with vibration guided devices and with sinus rate.

Activity controlled pacemakers are the most widely used rate adaptive systems. We studied second-generation activity controlled systems (accelerometer) in 21 patients with such an accelerometer controlled system implanted during walking level and stairs. We compared them to the rate of vibration controlled, first-generation activity pacemakers and to the sinus rate of a healthy control group. A metronome directed the speed during walking and climbing stairs at 92, 108, and 120 steps/min. At 92 steps/min, the new accelerometer controlled systems showed a significant (P < or = 0.001) pacing rate increase from 107 +/- 8 beats/min during walking level to 124 +/- 8 beats/min during climbing stairs, and a significant decrease to 105 +/- 12 beats/min during walking downstairs. In contrast, first-generation activity controlled pacemakers showed a less physiological rate behavior with higher pacing rate (113 +/- 7 beats/min) walking downstairs than walking upstairs (97 +/- 9). For everyday activities at normal walking speed, accelerometer controlled pacemakers show a more physiological rate behavior than first-generation pacemakers, but they lose this physiological response with faster walking.

Cardiac Pacing, Artificial↗
PubMed1996

Three-year experience with a stylet for lead extraction: a multicenter study.

INTRODUCTION: The extraction of chronically implanted and infected pacemaker and defibrillator leads is an important issue. This article describes the experience gathered between 1990 and 1994 by seven European centers regarding a locking stylet that is uniformly applicable for a wide variety of internal pacing coil diameters. This interventional locking stylet for lead extraction has an outer diameter of 0.4 mm (0.016 inches). The stylet consists of a hollow shaft in which an inner traction wire is embedded. At the tip of the inner traction wire an anchoring mechanism, which can be opened by retraction, is applied. Removal attempts were made for 150 leads, 110 in ventricular and 40 in atrial positions. RESULTS: Complete removal was possible in 122 cases (81%). Partial removal was possible in 18 cases (12%). Failure to remove the lead with the extraction stylet was experienced in 10 cases (7%). In seven patients, the leads were removed by cardiothoracic surgery; 3 defective leads were left in place. There were no serious complications associated with the procedure. None of the patients died. CONCLUSION: The experience with this extraction stylet for lead removal has shown good results. Despite a low complication rate thus far, each case for lead removal should be judged on the individual basis of benefit-to-risk ratio.

Aged↗
PubMed1996

Reimplantation of an infected, abdominally implanted defibrillator in the subpectoral region.

This report regards a 55-year-old patient with an abdominally implanted, nonthoracotomy, cardioverter defibrillator system (Medtronic PCD 7217B) due to recurrent ventricular tachycardia and survived sudden cardiac death. Fifteen months after defibrillator implantation clinical signs of system infection occurred. The defibrillator and the two leads (Medtronic 6963 and 6966) were removed and treatment with intravenous antibiotic therapy was started. Thereafter the original resterilized ICD was re-implanted in a right subpectoral position with new right ventricular-and superior vena cava leads. This report shows that reuse of the relatively large Medtronic PCD 7217B with a new transvenous lead system in a retropectoral location is feasible and economically beneficial with regard to the high device cost.

Anti-Bacterial Agents↗
PubMed1995

[Heart rate changes in a new generation of activity controlled pacemakers during stair climbing].

OBJECTIVE: A study was undertaken to determine whether a new generation of accelerometer controlled rate adaptive pacemakers has advantages over the older type of activity controlled pacemaker. PATIENTS AND METHODS: Pacemaker rates of 21 patients (15 women, six men; mean age 64.1 [44-85] years) with the new pacemakers were compared with those of a control group of patients free of cardiac disease (four women, six men; mean age 50.5 [39-75] years) in whom a vibration controlled pacemaker system had been attached to the right pectoral area. Heart rate was monitored by a rate analyser, data recorder and rate watch throughout the period of activity. Step frequencies of 92, 108 and 120 steps/min were fixed by metronome. RESULTS: The new pacemaker responded with a rate increase at a step rate of 92/min (P < 0.001): from 106.6 +/- 7.9 beats/min on walking on the even, to 123 +/- 8.4 beats/min on stair climbing. There was a significant fall in frequency, to 105 +/- 11.7 beats/min, when descending steps. The conventional pacemakers responded with a decrease in frequency on stair climbing (97.2 +/- 8.7 beats/min compared with 112.6 +/- 7.4 when descending). CONCLUSIONS: The results indicate that the new system provides for a more physiological rate response. However, this difference between the older and the new generation of pacemakers is less marked on walking at higher step rates.

Adult↗
PubMed1995

Prevention of carbon tetrachloride-induced rat liver injury by soluble tumor necrosis factor receptor.

BACKGROUND/AIMS: Considerable indirect evidence suggests that cytokine tumor necrosis factor alpha contributes to the hepatocellular damage caused by toxic liver injury. The effects of tumor necrosis factor alpha neutralization on liver cell injury were determined in an in vivo model of toxic liver injury. METHODS: The in vivo effects of tumor necrosis factor alpha were examined in carbon tetrachloride liver injury through the administration of a soluble tumor necrosis factor receptor to neutralize the effects of this cytokine. RESULTS: Soluble tumor necrosis factor receptor treatment decreased the degree of liver injury as measured by reduced levels of serum liver enzymes and improved histology. Soluble tumor necrosis factor receptor administration also lowered the mortality from a lethal dose of carbon tetrachloride from 60% to 16%. Tumor necrosis factor alpha neutralization had no detrimental effect on liver regeneration as determined by the timing of histone gene expression and postinjury liver weight. CONCLUSIONS: These data provide direct evidence for a role of tumor necrosis factor alpha in toxin-induced liver cell injury. In addition, these investigations suggest that soluble tumor necrosis factor receptor therapy may be of benefit in the treatment of human liver disease.

Animals↗
PubMed1995

Initial clinical experience with a new dual sensor SSIR pacemaker controlled by body activity and minute ventilation.

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

Aged↗
PubMed1995

Intestinal pseudo-obstruction and ischemia secondary to both beta 2-microglobulin and serum A amyloid deposition.

We present the case of a 61-year-old man on long-term hemodialysis in whom early colonic ischemia and pseudo- obstruction were caused by amyloid deposition of both the beta 2-microglobulin and AA type. The light microscopic diagnosis of amyloidosis was confirmed by Congo red birefringence, immunohistochemistry, and electron microscopy. The two types of amyloid had separate distributions within the colon. While both types affected submucosal and serosal blood vessels, the beta 2- microglobulin amyloid also formed large masses that displaced smooth muscle cells and was associated with Class II major histocompatibility-positive multinucleated giant cells. The pathogenesis of this uncommon occurrence of two amyloids and the role of chronic inflammation in amyloidogenesis are discussed.

Colitis, Ischemic↗
PubMed1994

A targeted chain-termination mutation in the mouse Apc gene results in multiple intestinal tumors.

Germ-line mutations in the human adenomatous polyposis coli (APC) gene result in familial adenomatous polyposis, an autosomal dominant disorder characterized by the early onset of multiple adenomatous polyps in the large bowel with a high likelihood of developing colorectal carcinomas. To understand the role of APC in intestinal tumor formation, we have introduced a chain-termination mutation in the 15th exon of the mouse Apc gene and employed it to modify the endogenous gene by homologous recombination in embryonic stem cells. Mice which are heterozygous for the Apc gene modification progressively develop intestinal tumors in a manner that is similar to that observed in patients with familial adenomatous polyposis and in mice which carry a mutation called multiple intestinal neoplasia (Min). Our results indicate that the Apc gene modification is a critical event in the initiation of intestinal tumor formation and results in an autosomal dominant predisposition toward development of spontaneous colonic and intestinal tumors in mice.

Adenomatous Polyposis Coli↗
PubMed1994

Altered body composition and increased frequency of diverse malignancies in insulin-like growth factor-II transgenic mice.

The physiological role of insulin-like growth factor (IGF) II (IGF-II) in adult humans is poorly understood. Rather high levels of IGF-II persist in adult human serum, whereas, in rodents, IGF-II levels are very low. To investigate the physiological and carcinogenic effects of persistently elevated IGF-II in adults, we have produced two lines of transgenic mice in which high levels of IGF-II (20- or 30-fold increase above normal) are persistently maintained in the blood. The transgene is driven by the major urinary protein promoter, and it is highly expressed in the liver and perputial glands in both lines. The adult transgenic mice are smaller than controls, and their body composition is altered. Their lean body mass is reduced by 5-8%, whereas fat mass is reduced between 44 and 77%. The mice expressing the highest level of IGF-II (30x) develop hypoglycemia and hypoinsulinemia and IGF-I levels are normal. Mice in the lower expression line (20-fold elevated IGF-II) develop hypoglycemia progressively over their lifetime. Mice from both lines also develop a diverse spectrum of tumors at a higher frequency than controls after 18 months of age, and the most frequent types of tumors are hepatocellular carcinomas and lymphomas. Squamous cell carcinoma, sarcoma, and thyroid carcinomas also occurred in our test group. The long latent period before tumors arise and the wide spectrum of tumor types suggest that IGF-II may function primarily as a tumor progression factor in mice via autocrine and endocrine mechanisms of action.

Animals↗
PubMed1994

Behavior of different activity-based pacemakers during treadmill exercise testing with variable slopes: a comparison of three activity-based pacing systems.

A new generation of activity-based pacemakers incorporates an accelerometer sensitive to low frequency acceleration signals in the anteroposterior direction for sensing of bodily stress. The purpose of our investigation was to test a representative model of these new activity-based pacemakers (Relay) and compare it with current vibration- and housing pressure-sensing systems. We tested ten pacemaker patients with implanted Activitrax, Sensolog, and Relay systems during treadmill exercise testing with variable slopes. Devices from the three systems were also strapped externally to the chest of each patient and to ten normal test subjects in the control group. Exercise tests were conducted with changes of treadmill speed and/or treadmill slope. For comparable workloads during constant speed/variable slope and constant slope/variable speed, Relay had similar rate responses (difference not significant). Significant differences (P < 0.05) in rate adaptation attributable to the kind of treadmill exercise (change in treadmill speed or slopes) were observed in the housing pressure- and vibration-based pacemakers. Activity-based pacemakers with an acceleration sensor adapt pacing rates during treadmill exercises independent of treadmill speed or slope better than those controlled by a conventional housing pressure or vibration sensor.

Acceleration↗
PubMed1994

[Improvement in oxygen consumption by frequency-adjusted pacemaker stimulation: effect of intrinsic heart rate].

More than half of all pacemaker systems currently implanted function rate-adaptively. Our objective was to determine which patients benefit from rate-adaptive pacing in terms of improvement in maximum performance and aerobic capacity. Thirty patients with implanted accelerometer-driven, rate-adaptive pacemakers were examined ergospirometrically and patient symptom-limited while walking on a treadmill. The patients were divided into three groups depending on the intrinsic heart rate achieved during maximum workload: Group I achieved < or = 90 bpm, Group II achieved 90 to < or = 110 bpm, Group III achieved > 110 bpm. Group I demonstrated a significant increase (p < or = 0.01) in maximum oxygen uptake from 16.4 +/- 5.6 ml/kg/min with fixed-rate pacing to 23.2 +/- 11.1 ml/kg/min (+41.5%) with rate-adaptive pacing. At the anaerobic threshold, oxygen uptake significantly increased (p < or = 0.01) from 11.8 +/- 2.7 ml/kg/min to 15.7 +/- 5 ml/kg/min (+33.1%). Group II showed an increase in maximum oxygen uptake from 23.3 +/- 5.4 ml/kg/min to 25.3 +/- 4.9 ml/kg/min (+8.5%, p < or = 0.05) as well as an increase in oxygen uptake at the anaerobic threshold from 15.9 +/- 2.6 ml/kg/min to 18.1 +/- 2.9 ml/kg/min (+13.8%, p < or = 0.05) with rate-adaptive pacing. Group III demonstrated no significant difference between the two pacing methods (from 25.6 +/- 9.4 ml/kg/min to 25.9 +/- 9.3 ml/kg/min and from 15.8 +/- 5.5 ml/kg/min to 16.3 +/- 6 ml/kg/min). No difference in maximum oxygen uptake and in oxygen uptake at the anaerobic threshold was evident between the three groups when paced rate-adaptively (n.s.).(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1994

Lipopolysaccharide-neutralizing antibody reduces hepatocyte injury from acute hepatotoxin administration.

Endogenous lipopolysaccharide has been implicated as a cofactor in the hepatocellular injury and death resulting from toxic liver injury. To prevent this lipopolysaccharide-induced injury and to further understand the mechanism of this effect, an anti-lipopolysaccharide antibody was administered to rats in which toxic hepatocellular injury was induced. Rats were given the hepatotoxin galactosamine together with an isotypic control antibody B55 or the anti-lipopolysaccharide antibody E5. E5 treatment resulted in reductions of serum AST levels of 43% at 36 hr (p < 0.02) and 60% at 48 hr (NS) after galactosamine administration. These decreases in AST values were accompanied by diminished histological evidence of injury and inflammation. In carbon tetrachloride-induced liver injury, E5 similarly reduced serum AST levels at 36 and 48 hr by 47% (p < 0.04) and 54% (p < 0.03), respectively. E5 treatment was equally effective in reducing AST levels 48 hr after administration of carbon tetrachloride, whether the initial dose of antibody was given 1 hr before or 3 or 6 hr after the administration of this toxin. To understand the mechanism of this E5 effect, the activation of the toxic cytokine tumor necrosis factor-alpha and the chemotactic cytokine monocyte chemoattractant protein 1 was examined by Northern-blot analysis of RNA from rat livers after galactosamine-induced injury and treatment with B55 or E5. Despite E5's efficacy in reducing hepatocellular damage, E5 treatment did not affect the timing or magnitude of tumor necrosis factor-alpha or monocyte chemoattractant protein 1 activation during galactosamine-induced injury.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

[Ventricular fibrillation and silent myocardial ischemia in a patient without anatomic heart disease].

A 44-year-old man, apparently without heart disease, suddenly collapsed with loss of consciousness. Ventricular fibrillation was documented when an external defibrillator was connected. After cardiopulmonary resuscitation and intubation he quickly regained consciousness. Clinical examination together with echocardiography, coronary angiography and electrophysiological tests discovered no abnormalities. Biochemical tests were normal except for slightly abnormal liver functions. Several long-term ECG recordings documented asymptomatic S-T elevations. During one such episode there occurred a polymorphous ventricular tachycardia of brief duration. Because the S-T elevations persisted, despite the administration of gallopamil (50 mg twice daily for one week), a defibrillator was implanted. Gallopamil was then discontinued. Long-term ECG monitoring subsequently revealed four episodes of marked S-T elevations, three of which accompanied by ventricular arrhythmias. After resuming gallopamil, now at a dose of 50 mg three times daily, further ECG monitoring showed no abnormalities.

Adult↗