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Biomedical subjects

K Bachmann

Publications and source records attributed to K Bachmann.

At least 127 records · Page 7Linked to original sources
PubMed1991

Biomagnetic localization of ventricular arrhythmias.

The magnetic fields caused by electrical activity of the human heart can be coherently measured with a highly sensitive, multichannel, superconducting quantum interference-device system and can enable noninvasive localization of the underlying electrical activity. The magnetocardiograms (MCGs) of 10 patients with spontaneous premature ventricular complexes (PVCs), three patients with ventricular tachycardia (VT), and four healthy subjects with induced paced beats were recorded for 2-15 minutes. After correction for superimposed repolarization activity, the site of origin of the arrhythmias was localized from the magnetic field distribution at the onset of the ectopic beats. The localization results of paced beats showed an error of a few millimeters in relation to the position of the catheter tip. The results of spontaneous PVC and VT were confirmed with endocardial mapping or associated with ischemic lesions. The authors conclude that multichannel magnetocardiographic studies enable the completely noninvasive localization of ventricular arrhythmias.

Adult↗
PubMed1991

Chronotherapy in coronary heart disease: comparison of two nitrate treatments.

The purpose of this study was to assess the ischemic burden and the hemodynamic changes during daily activities in patients with coronary heart disease. Three exercise tests were performed during the day (10:00 a.m., 2:00 p.m., 6:00 p.m.), recording ST-segment depression, pulmonary artery pressure, pulmonary wedge pressure, and cardiac output as well as heart rate and systemic blood pressure during placebo and nitrate therapy. With placebo as well as nitrate therapy there was a gradual increase of ischemia and preload and a decrease of cardiac output during the day. High nitrate concentrations led to a significant reduction of both preload and ST depression with a marked circadian phase dependency of cardiovascular effects.

Aged↗
PubMed1991

[Localized 31 phosphorus NMR spectroscopy of the human heart--development of a measuring method and initial clinical application].

In this work, the technique of 31P-NMR-spectroscopy is applied for the first time to diagnose coronary heart disease in patients, using a suitable measuring technique. In 13 healthy volunteers we applied a method comfortable and tolerable for patients, which enabled us to examine the myocardium inside the reception area of a surface coil. Concerning myocardium-specific selectivity and sensitivity the localization techniques FROGS (Fast-ROtating-Gradient-Spectroscopy), 1-D-ISIS (1-Dimensional-Image-Selected-In-vivo-Spectroscopy) and 3-D-ISIS were compared. By a combination of the 3-D-ISIS-technique with magnetic resonance imaging, we obtained a monitored position of the volume of interest (VOI) within the myocardium, thus gaining a selective measurement. The cube-shaped VOI with a lateral length of 50 mm was placed into the apical-septal area of the myocardium. On the basis of the obtained results, we examined seven patients suffering from coronary heart disease, which was symptomatic and verified by coronary angiography. The 31P-NMR-spectra of the two examined groups were computed into numbers representing the relative content of the myocardial high-energy-phosphates. In addition, the quotients PCr/ATP and Pi/ATP were calculated and compared. With this small number of cases the evaluation of the PCr/ATP-ratios already showed a significant difference of 0.34 (p less than 0.01) between patients with coronary heart disease (0.49 +/- 0.19) and healthy volunteers (0.83 +/- 0.27). The findings suggest the conclusion that 31P-NMR-spectroscopy is able to be instrumental in the diagnostic detection assessment of the metabolic state in coronary heart disease.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine Triphosphate↗
PubMed1991

[Magnetic resonance rheography in comparison to Doppler ultrasonography in the assessment of mitral valve stenosis].

Ultrasound-Doppler-technique and heart catheterization today are used routinely for the evaluation and graduation of mitral valve stenosis. A new magnetic resonance-technique of intracardial blood-flow registration now allows the grading of mitral valve stenosis. Good reliability and practicability of the demonstrated method in comparison with the ultrasound-Doppler-technique is shown. Future development of an alternative, completing magnetic-resonance method for the evaluation of valvular heart disease and shunt diagnosis is expected.

Adult↗
PubMed1990

[Acute isolated ischemia of the right ventricle with ST elevation in V1 to V4].

An acute anteroseptal infarction was diagnosed in a 51-year-old man whose ECG showed ST elevations in leads V1-V4 after acute retrosternal pain for about 20 min. Angiography revealed proximal occlusion of the right coronary artery, while the dominant left coronary artery was fully patent. After successful recanalization of the right coronary artery with intracoronary infusion of urokinase, the ST elevations quickly disappeared and impending right-heart infarction was avoided. Isolated right-heart infarction can imitate the ECG pattern of anteroseptal infarct and should be considered if the height of ST elevations diminishes from V1 to V4.

Angiocardiography↗
PubMed1990

Failure of ceftibuten to alter single dose theophylline clearance.

Twelve volunteers participated in a two-way crossover trial in which the effects of ceftibuten on the pharmacokinetics of theophylline were evaluated. Subjects were given single intravenous doses of theophylline (4 mg/kg) with no ceftibuten treatment and on the sixth day of ceftibuten treatment. Ceftibuten 200 mg was taken orally twice daily (7:00 AM and 7:00 PM). A total of 13 blood samples per subject were collected over 48 hours following theophylline administration. Ceftibuten failed to alter either the systemic clearance of theophylline (CL), its volume of distribution (Vss), or its elimination half-life (t1/2). The 24-hour plasma theophylline concentration measured both by high performance liquid chromatography (HPLC) or fluorescence polarization immunoassay (FPIA) was used for a single sample estimate of theophylline clearance (CL), and it was found to provide a suitable estimate of the multisample value for CL.

Administration, Oral↗
PubMed1990

Changes in the steady-state pharmacokinetics of theophylline during treatment with dirithromycin.

The steady-state plasma concentrations and pharmacokinetic characteristics of theophylline were studied during intermittent treatment with dirithromycin. The addition of dirithromycin (500 mg orally once daily at 7:00 AM) to a sustained-release theophylline dosing regimen (200 mg every 12 hours) elicited small changes in the steady-state pharmacokinetics of theophylline. Mean steady-state plasma theophylline trough concentrations (Cmin) were invariant before, during, and after dirithromycin treatment; however, mean average steady-state plasma theophylline concentrations (Cav) declined by 18% during dirithromycin treatment (P less than .05), and mean peak plasma concentrations (Css,max) declined by 26% (P less than .01). Theophylline clearance (CL/F) exhibited an increase of comparable magnitude during dirithromycin treatment, although the increase in CL/F was not statistically significant (.05 less than P less than .1). Dirithromycin treatment alters the steady-state pharmacokinetics of theophylline; however, the magnitude of the changes is small and is not likely to modify treatment outcomes.

Administration, Oral↗
PubMed1990

[The computer simulation of orthodontic tooth movements].

A personal computer programme is presented which allows the prediction of orthodontic tooth movement under the influence of any given force and moment. The changes in position of the front teeth caused by the chosen forces appear on the monitor as a three-dimensional diagram and as a movie-like picture sequence.

Computer Simulation↗
PubMed1990

Elimination of electronic offset and physiological background activity in magnetocardiographic localization.

A method has been developed to eliminate disturbing magnetic signals in the biomagnetic localization of arrhythmogenic sources in the heart. The procedure consists of two steps: Superimposed background activity of the heart is eliminated by subtraction of a template of pure background activity. Systematic and electronic offset is subsequently eliminated by baseline-correction during periods of zero activity. The method was applied to several kinds of arrhythmias. It was demonstrated that elimination of background activity is the prerequesite for exact localization and that the proposed procedure yields correct results.

Algorithms↗
PubMed1990

Circadian variation of cardiac performance in coronary heart disease.

To study the circadian variation of cardiac performance in patients with coronary heart disease, three exercise tests on a bicycle ergometer were performed during the active part of the day (10 a.m., 2 p.m. and 6 p.m.), recording ST-segment depression and pulmonary capillary wedge pressure. Ten male patients with angiographically documented coronary heart disease underwent bicycle ergometry during placebo and during nitrate therapy (placebo controlled, double-blind crossover 2 x 20 mg IS-5-MN and 1 x 120 mg ISDN sustained release). During placebo as well as during nitrate therapy there was a gradual decrease of cardiac performance during the day, documented by the increase in ST-depression and pulmonary capillary wedge pressure at equal work loads. High nitrate concns led to a significant reduction of both ST-depression and preload with a marked circadian-phase dependency of cardiovascular effects.

Aged↗
PubMed1989

Predicting toxicokinetic parameters in humans from toxicokinetic data acquired from three small mammalian species.

Values for the independent kinetic variables, clearance (CL) and volume of distribution (V), for six xenobiotics--antipyrine, ethosuximide, phencyclidine, theophylline, valproic acid and warfarin--were culled from the literature for each of three small subhuman species and for humans, and then allometrically scaled. Scaling was performed in two ways. First, using kinetic data acquired for three small subhuman species and for man, scaled parameters were observed for goodness of fit to a standard allometric expression. Second, scaled parameters were averaged for three subhuman species. Mean scaled kinetic parameters from only three species were used to predict half-life values of the xenobiotics in humans. Finally, predicted percentages of the xenobiotic burdens remaining in humans at the end of four allometrically-predicted half-lives were compared with the expected percentages of remaining xenobiotic based upon four actual half-lives in humans. The results suggest that it may be feasible to estimate, using three small subhuman species, allometrically-derived toxicokinetic parameters of some substances in man with sufficient accuracy to be of practical value.

Animals↗
PubMed1989

[Afterload reduction by long-term nitrate therapy].

Tolerance to arterial and venous effects is a common problem in longterm-therapy with nitrates when dosing schemes with multiple, regulary timed intervals throughout the day are applied. A balanced effect on preload and afterload is essential for a successful therapy of congestive heart failure. Interval therapy, the once daily medication of a nitrate, has a proven tolerancefree effect on preload. This study addresses the problem of afterload reduction under longterm interval therapy with nitrates. Nine patients with coronary heart disease NYHA II-III with congestion under exercise where included in the study. After a washout period they where treated with once-daily 120 mg ISDN s.r. Measuring mean arterial pressure and cardiac output, we compared the effect of the first dose (acute) with the effect after 5 weeks 1 x 1 120 mg ISDN s.r. (chronic). After acute therapy the mean arterial pressure under exercise was reduced by 14% from 121 +/- 12 mmHg to 104 +/- 11 mmHg. The average reduction of blood pressure under exercise was unchanged during chronic therapy (105 +/- 8 mmHg). Peripheral resistance was reduced by 21% from 914 +/- 266 to 722 +/- 190 dynsec/cm5 after the first dose. The afterload reduction was maintained during chronic therapy (727 +/- 176 dynsec/cm5).

Blood Pressure↗
PubMed1989

[Ambulatory invasive and noninvasive blood pressure monitoring].

Indirect arterial blood pressure measurement has not changed substantially since its introduction by Riva-Rocci in 1986, Korotkoff in 1905 and Recklinghausen in 1906. Random measurements in the clinic or practice reflect only incompletely the dynamic nature of the blood pressure. Blood pressure recordings by patients themselves have provided more information through better temporal resolution, however, exact characterization of the pressure response throughout the entire day and, in particular, during physical exertion are not enabled; the latter are especially important with regard to diagnosis and treatment of hypertension. In 1966, therefore, radiotelemetric transmission of direct, continuously-measured arterial blood pressure was developed which enabled beat-to-beat registration of blood pressure, outside the laboratory, during normal daily life and sport activities. The initial results showed a marked variability of the blood pressure during the course of the day (Figure 1). Excessive blood pressure increases were observed during exposure to cold, static and dynamic exercise and to a lesser degree during automobile driving and exposure to heat (Figure 3). Recording of the pressure curves via transmission by radiotelemetry shows a high degree of accuracy and temporal resolution, spatial and situational freedom but is invasive and costly in terms of personnel. The same holds true for direct continuous blood pressure registration and storage on a portable tape recorder. Portable, automatic blood pressure measuring units for ambulatory monitoring employ indirect auscultatory or oscillometric recording with a cuff. As compared with the radiotelemetric direct continuous blood pressure measuring method, the indirect method has subordinate temporal resolution, that is, the measurements are only intermittent.(ABSTRACT TRUNCATED AT 250 WORDS)

Ambulatory Care↗
PubMed1989

[Hemodynamic study of the development of tolerance in intravenous nitrate therapy].

UNLABELLED: To investigate possible tolerance development under an intravenous treatment with nitrates, 22 patients with coronary artery disease were randomly assigned to receive either 4 mg/h of ISDN (n = 12) or placebo (n = 10) and were given additional 10 mg of ISDN or placebo after 23 h. Pulmonary artery pressures (PAP), cardiac output, and heart rate were registered before, and 4 h, 22.5 h, and 24 h after the beginning of treatment. At baseline both groups were similar with regard to pulmonary artery diastolic pressure (PADP) at rest and at comparable work load. Each patient of the placebo group showed identical PAPs at work. ISDN led to a 42-59% decrease of PADP at rest and 29-37% decrease at comparable work load. After 22.5 h a statistically insignificant reduction of ISDN effect was observed which could be reversed by additional ISDN p.o. A detailed analysis of the ISDN group showed seven patients with a persistently lowered PADP, (table; see text) whereas five patients demonstrated a partial diminuation of the ISDN effect. No patient showed a complete tolerance. In the placebo group blood pressure did not show any change during the treatment period (143 +/- 21/84 +/- 10 mmHg vs 137 +/- 17/79 +/- 10 mmHg), whereas ISDN infusion resulted in a continuously lowered blood pressure (150 +/- 22/83 +/- 11 mmHg vs 125 +/- 15/72 +/- 9 mmHg (p less than 0.001). Cardiac output and heart rate were similar under ISDN and placebo treatment. CONCLUSION: Continuous infusion of 4 mg of ISDN/h over 24 h and an additional dose of 10 mg of ISDN after 23 h provided a significant reduction in PADP, blood pressure and rate pressure product over 24 h at rest and during exercise.

Administration, Oral↗