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Biomedical subjects

J Kastner

Publications and source records attributed to J Kastner.

At least 19 recordsLinked to original sources
PubMed2003

Unexplained syncope in patients with structural heart disease and no documented ventricular arrhythmias: value of electrophysiologically guided implantable cardioverter defibrillator therapy.

AIMS: To evaluate electrophysiologically guided implantable cardioverter defibrillator (ICD) therapy in patients with syncope, structural heart disease and no documented sustained ventricular tachycardia (sVT). METHODS AND RESULTS: Programmed ventricular stimulation (PVS) was performed in 52 patients (age 62+/-10 years): 40 patients had ischaemic and 12 patients had idiopathic dilated cardiomyopathy. On PVS sVT and ventricular fibrillation were induced in seven and four patients, respectively, and two patients spontaneously experienced symptomatic sVT. These patients received an ICD (ICD group, n=13). Non-inducible patients were left on conventional therapy (non-ICD group, n=39). During 5+/-2.8 years five ICD patients received therapies, all appropriate. There were seven non-sudden deaths and overall survival analysis revealed no significant difference. Recurrent syncope occurred in five ICD and four non-ICD patients and did not correlate well with sVT. The positive and negative predictive values of PVS for tachyarrhythmias or sudden death were 36 and 98%, respectively. CONCLUSION: Syncope per se does not necessarily herald a bad prognosis. PVS identifies high-risk patients. Induction of ventricular fibrillation with double or triple extrastimuli is of limited value. Patients with poor left ventricular function and bad clinical condition benefit most from an ICD. Syncope and sVT are not necessarily correlated during follow-up, which may merit consideration.

Aged↗
PubMed2003

[Urologic complications in pelvic injuries].

OBJECTIVE: Urological complications of pelvic fractures include in particular rupture of the urinary bladder (RUB), injury of the posterior urethra (IPU) and erectile dysfunction (ED). The authors present their own group of patients and in particular the diagnostic and therapeutic algorithm in IPU. MATERIAL AND METHODS: In the Plzen Faculty Hospital in 1/1998 to 8/2002 a total of 19 patients were treated with serious urological complications of pelvic fractures--9x RUB, 11x IPU (once with RUB). RUB was in one instance intraperitoneal, in the remainder extraperitoneal. RESULTS: IPU was without dislocation 6x, with dislocation 5x. Primary "realignment" of the urethra was made in 6 patients (in dislocations and in concurrent rupture of the bladder). In the remaining 5 an epicystostomy was established. In 4 after an interval of 3 months a posterior resection urethroplasty was made because of a distraction defect. One patient with a distraction defect was referred to the urological department of the catchment area and in another patient after-treatment is planned. Severe ED developed in 6 IPU of 10, always in dislocations of the urethra. In one patient we lack information on erections. CONCLUSION: When IPU is suspected (urethrorhagia), dislocation of the prostate on examination p.r.) ascendent urethrography and IVU are essential. Do not catheterize before completed examination. Then needle epicystostomy is performed, in major dislocations of the urinary bladder or in associated injuries primary "realignment" of the urethra open on a catheter or endoscopically. In distraction defects after 12 weeks a posterior resection plastic operation follows.

Adult↗
PubMed2001

Boundary element method volume conductor models for EEG source reconstruction.

OBJECTIVES: The boundary element method (BEM) approximates the different compartments of volume conductor models by closed triangle meshes with a limited number of nodes. The shielding effect of the weakly conducting skull layer of the human head leads to decreasing potential gradients from the inside to the outside. Thus, there may be an optimum distribution of nodes to the compartments for a given number of nodes corresponding to a fixed computational effort, resulting in improved accuracy as compared to standard uniform distributions. METHODS: Spherical and realistically shaped surfaces are approximated by 500, 1000, 2000, and 3000 nodes, each leading to BEM models with 1500-9000 nodes in total. Electrodes are placed on extended 10/20-system positions. Potential distributions of test-dipoles at 4000 random positions within the innermost compartment are calculated. Dipoles are then fitted using 192 different models to find the optimum node distribution. RESULTS: Fitted dipole positions for all BEM models are evaluated to show the dependency of the averaged and maximum localization errors on their node distributions. Dipoles close to the innermost boundary exhibit the largest localization errors, which mainly depend on the refinement of this compartment's triangle mesh. CONCLUSIONS: More than 500 nodes per compartment are needed for reliable BEM models. For a state-of-the-art model consisting of 6000 nodes overall, the best model consists of 3000, 2000, and 1000 nodes from the inside to the outside.

Brain↗
PubMed2000

[Nonlinear dynamics, chaos theory and wavelet analysis of the heart].

Over the past years, techniques of nonlinear dynamics have gained increasing attention in cardiology. This kind of partly interdisciplinary research is supposed to provide a better understanding of cardiac disease, especially in the field of tachyarrhythmia. This article intends to introduce the principles of diagnostic procedures in terms of nonlinear dynamics, chaos theory and stochastic processes related to cardiology. An introduction to a new technique of wavelet analysis is given, and possible applications in the quantitative classification of high-risk patients for sudden cardiac death are discussed.

Arrhythmias, Cardiac↗
PubMed2000

Inhaled nitric oxide reduces pulmonary vascular resistance more than prostaglandin E(1) during heart transplantation.

UNLABELLED: Heart transplantation in patients with increased pulmonary vascular resistance is often associated with postbypass right heart failure. We therefore compared the abilities of prostaglandin E(1) (PGE(1)) and inhaled nitric oxide to reduce pulmonary vascular resistance during heart transplantation. Patients undergoing orthotopic heart transplantation for congestive heart failure were randomly assigned to either a PGE(1) infusion at a rate of 8 ng. kg. (-1)min(-1) starting 10 min before weaning from cardiopulmonary bypass (CPB) (n = 34) or inhalation of 4 ppm nitric oxide starting just before weaning from CPB (n = 34). Both treatments were increased stepwise, if necessary, and were stopped 6 h postoperatively. Hemodynamic values were recorded after the induction of anesthesia, 10 and 30 min after weaning from CPB, and 1 h and 6 h postoperatively. Immediately after weaning from CPB, pulmonary vascular resistance was nearly halved in the nitric oxide group but reduced by only 10% in the PGE(1) group. Pulmonary artery pressure was decreased approximately 30% during nitric oxide inhalation, but only approximately 16% during the PGE(1) infusion. Six hours after surgery, pulmonary vascular resistance and pulmonary artery pressure were similar in the two groups. The ratio between pulmonary vascular resistance and systemic vascular resistance was significantly less in the nitric oxide patients at all postbypass times. In contrast, the pulmonary-to-systemic vascular resistance ratio increased approximately 30% in the patients given PGE(1). Cardiac output, heart rate, mean arterial pressure, right atrial pressure, and pulmonary wedge pressure did not differ between the groups. Weaning from CPB was successful in all patients assigned to nitric oxide inhalation; in contrast, weaning failed in six patients assigned to PGE(1) (P = 0.03). IMPLICATIONS: Nitric oxide inhalation selectively reduces pulmonary vascular resistance and pulmonary artery pressure immediately after heart transplantation which facilitates weaning from cardiopulmonary bypass.

Administration, Inhalation↗
PubMed2000

Efficacy of two methods for reducing postbypass afterdrop.

BACKGROUND: Afterdrop, defined as the precipitous reduction in core temperature after cardiopulmonary bypass, results from redistribution of body heat to inadequately warmed peripheral tissues. The authors tested two methods of ameliorating afterdrop: (1) forced-air warming of peripheral tissues and (2) nitroprusside-induced vasodilation. METHODS: Patients were cooled during cardiopulmonary bypass to approximately 32 degrees C and subsequently rewarmed to a nasopharyngeal temperature near 37 degrees C and a rectal temperature near 36 degrees C. Patients in the forced-air protocol (n = 20) were assigned randomly to forced-air warming or passive insulation on the legs. Active heating started with rewarming while undergoing bypass and was continued for the remainder of surgery. Patients in the nitroprusside protocol (n = 30) were assigned randomly to either a control group or sodium nitroprusside administration. Pump flow during rewarming was maintained at 2.5 l x m(-2) x min(-1) in the control patients and at 3.0 l x m(-2) x min(-1) in those assigned to sodium nitroprusside. Sodium nitroprusside was titrated to maintain a mean arterial pressure near 60 mm Hg. In all cases, a nasopharyngeal probe evaluated core (trunk and head) temperature and heat content. Peripheral compartment (arm and leg) temperature and heat content were estimated using fourth-order regressions and integration over volume from 18 intramuscular needle thermocouples, nine skin temperatures, and "deep" hand and foot temperature. RESULTS: In patients warmed with forced air, peripheral tissue temperature was higher at the end of warming and remained higher until the end of surgery. The core temperature afterdrop was reduced from 1.2+/-0.2 degrees C to 0.5+/-0.2 degrees C by forced-air warming. The duration of afterdrop also was reduced, from 50+/-11 to 27+/-14 min. In the nitroprusside group, a rectal temperature of 36 degrees C was reached after 30+/-7 min of rewarming. This was only slightly faster than the 40+/-13 min necessary in the control group. The afterdrop was 0.8+/-0.3 degrees C with nitroprusside and lasted 34+/-10 min which was similar to the 1.1+/-0.3 degrees C afterdrop that lasted 44+/-13 min in the control group. CONCLUSIONS: Cutaneous warming reduced the core temperature afterdrop by 60%. However, heat-balance data indicate that this reduction resulted primarily because forced-air heating prevented the typical decrease in body heat content after discontinuation of bypass, rather than by reducing redistribution. Nitroprusside administration slightly increased peripheral tissue temperature and heat content at the end of rewarming. However, the core-to-peripheral temperature gradient was low in both groups. Consequently, there was little redistribution in either case.

Adult↗
PubMed2000

Enhancements in the accuracy of the center of pressure (COP) determined with piezoelectric force plates are dependent on the load distribution.

Errors up to +/- 30 mm in determining the COP with piezoelectric force plates have been reported in the literature. To compensate for these errors, correction formulas were proposed, based on measurements with single point loads. In this paper, it will be shown that the errors in the COP depend on the load distribution. Two examples are presented: (1) simulated balance study, and (2) different pressure patterns during walking. Accurate corrections can only be made for forces distributed over a small area. Errors are expected to be overcompensated if there are only a few pressure peaks separated by large distances. These errors can be as large as the statistical errors (5.8 +/- 3.7 mm) after compensation. For certain situations, it is probably better not to use correction formulas.

Biomechanical Phenomena↗
PubMed1999

Parameters influencing the accuracy of the point of force application determined with piezoelectric force plates.

Errors up to +/- 30 mm in determining the point of force application with piezoelectric force plates have been reported in the literature (Kistler, 1984. Multicomponent Measuring Force Plate for Biomechanics and Industry. Kistler, Switzerland; Bobbert and Schamhardt, 1990. Journal of Biomechanics 23, 705-710; Sommer et al., 1997. Proceedings of the XVI th I.S.B. Congress). To explain the main factors influencing the systematic errors the force plate system is modeled as a two-dimensional beam structure. By this model it is strongly indicated that the cause for the errors in determining the point of force application are bending moments in the measurement posts. The main parameters influencing the shape and magnitude of the error function are the ratios between the bending stiffness of the plate and the bending and compressive stiffnesses of the measurement posts. In the current design it is therefore not possible to eliminate the cause for the errors by changing the constructive parameters. By comparing the error functions derived with the beam model to the correction formulas given in the literature an improved algorithm is proposed. This paper shall help biomechanists in understanding the basic concepts of determining the point of force application with force plates and in constructing custom-made force plates for specific applications.

Algorithms↗
PubMed1999

Tissue heat content and distribution during and after cardiopulmonary bypass at 17 degrees C.

UNLABELLED: We measured afterdrop and peripheral tissue temperature distribution in eight patients cooled to approximately 17 degrees C during cardiopulmonary bypass and subsequently rewarmed to 36.5 degrees C. A nasopharyngeal probe evaluated trunk and head temperature and heat content. Peripheral tissue temperature (arm and leg temperature) and heat content were estimated using fourth-order regressions and integration over volume from 30 tissue and skin temperatures. Peripheral tissue temperature decreased to 19.7+/-0.9 degrees C during bypass and subsequently increased to 34.3+/-0.7 degrees C during 104+/-18 min of rewarming. The core-to-peripheral tissue temperature gradient was -5.9+/-0.9 degrees C at the end of cooling and 4.7+/-1.5 degrees C at the end of rewarming. The core-temperature afterdrop was 2.2+/-0.4 degrees C and lasted 89+/-15 min. It was associated with 1.1+/-0.7 degrees C peripheral warming. At the end of cooling, temperatures at the center of the upper and lower thigh were (respectively) 8.0+/-5.2 degrees C and 7.3+/-4.2 degrees C cooler than skin temperature. On completion of rewarming, tissue at the center of the upper and lower thigh were (respectively) 7.0+/-2.2 degrees C and 6.4+/-2.3 degrees C warmer than the skin. When estimated systemic heat loss was included in the calculation, redistribution accounted for 73% of the afterdrop, which is similar to the contribution observed previously in nonsurgical volunteers. IMPLICATIONS: Temperature afterdrop after bypass at 17 degrees C was 2.2+/-0.4 degrees C, with approximately 73% of the decrease in core temperature resulting from core-to-peripheral redistribution of body heat. Cooling and rewarming were associated with large radial tissue temperature gradients in the thigh.

Adult↗
PubMed1998

Effects of nitroglycerin and sodium nitroprusside on endexpiratory concentrations of nitric oxide in healthy humans.

The cellular origin of nitric oxide (NO) in exhaled air of healthy humans is unknown. It is currently not known, whether changes in NO concentrations that originate from pulmonary vessels, can be detected as changes in exhaled NO. Thus, we have studied the effects of increased intravascular NO generation on endexpiratory NO-levels. Twenty-four young healthy volunteers received nitroglycerin (GTN), sodium nitroprusside (SNP) or placebo i.v. in a randomized, double blind cross-over trial. Diastolic blood pressure decreased from 59 mmHg (95% confidence interval: 56-62) during placebo to 48 mmHg (CI: 45-51) and to 48 mmHg (CI: 45-50) after infusions of GTN and SNP, respectively. Heart rate increased from 69 (CI: 65-73) during placebo to 78 (CI: 72-84) and to 84 (CI: 77-92) after infusions of GTN and SNP, respectively (p<0.01 for all comparisons). However, no increase in exhaled NO was detected: endexpiratory NO-concentrations averaged 6.1 ppb (CI: 4.9-7.4), 5.7 ppb (CI: 4.4-7.0) and 6.4 ppb (CI: 5.3-7.6) under placebo, GTN and SNP infusions, respectively (Friedman ANOVA p=0.328). NO release from within the pulmonary vasculature does not significantly contribute to endexpiratory NO concentrations in non-intubated healthy humans suggesting that such NO measurements quantify NO production mainly from non-vascular pulmonary cells.

Adult↗
PubMed1998

Recurrent cardiac tamponade as first manifestation of gastric cancer.

Malignant pericardial effusion is an uncommon disorder and is usually caused by far advanced lung cancer, breast cancer, lymphoma and leukaemia. Pericardial effusion in recurrent gastric cancer has been reported in only three patients. We report the case of a 53-year-old male with sudden onset of dyspnoea, pericardial effusion and cardiac tamponade and the unexpected and the asymptomatic concurrence of gastric cancer. Recurrent haemorrhagic pericardial effusion with physical signs of cardiac tamponade as the initial and only clinical manifestation of gastric cancer has not been described previously.

Cardiac Tamponade↗
PubMed1997

The effect of systemic nitric oxide-synthase inhibition on ocular fundus pulsations in man.

There is experimental evidence that endothelium derived nitric oxide is involved in the regulation of ocular vascular tone. The purpose of this study was to investigate the effects of NO-synthase inhibition by N-monomethyl-L-arginine (L-NMMA) on ocular fundus pulsations in young healthy volunteers. Three milligrams per kilograms L-NMMA were administered i.v. over 5 minutes. Protocol 1: Measurements of blood pressure, pulse rate, fundus pulsation amplitude, NO-exhalation, and cardiac output were performed at baseline and 10, 30, 60, 90, 150, and 300 minutes after L-NMMA infusion (n = 8). Fundus pulsation amplitude, which has been shown to estimate the pulsatile component of the choroidal blood flow, was recorded with a recently developed laser interferometer. Protocol 2: Measurements of blood pressure, pulse rate, fundus pulsation amplitude, NO-exhalation, and blood flow velocity in the ophthalmic artery were performed in a randomized, placebo controlled cross over study (n = 10). Ten minutes after L-NMMA administration fundus pulsation amplitude decreased by 23 +/- 2% (protocol 1) and 19 +/- 1% (protocol 2, P < 0.01 each), cardiac output by 12 +/- 2% (P < 0.01), and exhaled NO by 55 +/- 6% (protocol 1) and 41 +/- 6% (protocol 2, P < 0.01 each). All parameters returned to baseline values within the 300 minutes observation period, with a faster recovery of fundus pulsation amplitude than of cardiac output and exhaled NO. Blood pressure, pulse rate, and ophthalmic artery blood flow velocity showed only minor changes during and after administration of L-NMMA. Our results suggest that systemic NO-synthase inhibition reduces pulsatile choroidal and most likely total choroidal blood flow in humans. The recovery of vascular tone in choroidal vessels seems to be different from the cardiovascular response. Our findings indicate that reduced fundus pulsations after L-NMMA are caused by systemic factors as well as by local reactions of the choroidal vasculature.

Adult↗
PubMed1997

Nitric oxide concentration in the gas phase of the gastrointestinal tract in man.

Nitric oxide (NO) has been implicated in various aspects of physiological regulation in the gastrointestinal tract. Hence, measurement of luminal NO concentrations is of interest for studying physiological and pathophysiological alterations in NO generation; however, at present, no reliable measurement techniques are available. Here we describe novel approaches for measurement of NO concentrations directly in the gas phase of the stomach and colon in healthy subjects and patients. Studies were conducted in young healthy volunteers (n = 13), intensive care patients (n = 8) and patients undergoing gastroscopy (n = 8) or colonoscopy (n = 8). NO concentrations were measured by chemolumininescence detection in air obtained through a nasogastric tube, after inflation into the stomach of a defined volume of air, or directly in the air suctioned from the endoscope. The mean NO concentration obtained from the stomach of healthy volunteers studied under baseline conditions was 18.0 +/- 2.8 (SEM) p.p.m. Day-to-day reproducibility of NO measurements was high. Tube feeding with a nitrite- and nitrate-free feeding solution left gastric NO concentrations unchanged, but standardized bicycle exercise caused an approximately 30% decrease in NO levels. NO concentrations in intensive care patients were approximately 2 log cycles lower than in healthy volunteers. NO levels in the colon were similar to those in the stomach. We have described two readily applicable techniques for direct, uncontaminated measurement of NO concentrations in the lumen of the gastrointestinal tract. Our finding of a striking reduction in gastric NO concentrations in intensive care patients requires further study.

Adult↗
PubMed1997

Nitric oxide synthase inhibition in the histamine headache model.

Histamine has been widely used experimentally to induce headache in healthy subjects and migraine in migraineurs. There is evidence that the vascular effects of histamine are at least partially mediated by nitric oxide (NO). Hence we hypothesized that subjective symptoms and hemodynamic effects of histamine could be reduced by systemic NO-synthase inhibition. We therefore studied the effect of pretreatment with N-monomethyl-L-arginine (L-NMMA), a competitive inhibitor of NO-synthase, or placebo on headache, flush and discomfort scores during histamine infusion. Additionally, blood flow velocities in the middle cerebral and the ophthalmic artery and ocular fundus pulsations were measured. Whereas L-NMMA blunted the effect of histamine in the ophthalmic artery and the ocular circulation, NO-synthase inhibition did not mitigate subjective symptoms. Histamine did not affect mean blood flow velocities in the middle cerebral artery. Hence, we conclude that NO-synthase inhibition reduces the histamine-induced vascular effects in the ocular circulation, but is not sufficient to attenuate or abort the subjective symptoms provoked by histamine infusion.

Adult↗
PubMed1997

Exhaled NO during graded changes in inhaled oxygen in man.

BACKGROUND: Nitric oxide (NO) is present in the exhaled air of animals and humans. In isolated animal lungs the amount of exhaled NO is decreased during hypoxia. A study was undertaken to determine whether changes in arterial oxygen tension affect levels of exhaled NO in humans. METHODS: Sixteen healthy subjects were randomised to inhale different gas mixtures of oxygen and nitrogen in a double blind crossover study. Eight gas mixtures of oxygen and nitrogen (fractional inspired oxygen concentration (FiO2) 0.1 to 1.0) were administered. Exhaled NO was measured with a chemiluminescence detector from end expiratory single breath exhalation. RESULTS: A dose-dependent change in exhaled NO during graded oxygen breathing was observed (p = 0.0012). The mean (SE) exhaled NO concentration was 31 (3) ppb at baseline, 39 (4) ppb at an FiO2 of 1.0, and 26 (3) ppb at an FiO2 of 0.1. CONCLUSIONS: The NO concentration in exhaled air in healthy humans is dependent on oxygen tension. Hyperoxia increases the level of exhaled NO, which indicates increased NO production. The mechanism behind this phenomenon remains to be elucidated.

Administration, Inhalation↗