Biomedical subjects

K Bachmann

Publications and source records attributed to K Bachmann.

At least 109 records · Page 6Linked to original sources

PubMed1993

[Quantitative evaluation of aortic valve insufficiency in magnetic resonance tomography].

Flow-encoded magnetic resonance (MR) sequences allow the quantitative evaluation of blood flow in any plane of the heart and vessels. For the first time, ejection and regurgitation volumes of the left ventricle in the ascending aorta can be measured noninvasively. Thus, the regurgitation fraction as a reliable measure of aortic valve insufficiency can be determined. The quantitative evaluation of aortic valve insufficiency was done by MR in comparison to ultrasound-Doppler and, in some cases, in comparison to heart catheterization. A good correlation of grading aortic valve insufficiency by the new MR-technique in comparison to clinical graduation is shown. The development of a new noninvasive standard for quantification of aortic valve insufficiency seems possible.

Adult↗

PubMed1993

[Digital subtraction angiocardiography: reliability of densitometric determination of left ventricular volume and ejection fraction].

The angiographic assessment of left ventricular volume (LV) and ejection fraction (EF) by means of the area-length method (ALM) is based upon geometric assumptions, which might lead to erroneous results. With the development of digital subtraction angiocardiography in real-time, densitometric procedures of calculating left ventricular parameters can be used on-line. This study examines both reliability and accuracy of a densitometric technique for evaluating LV and EF in comparison to the single-plane ALM. Contrast images of heart casts and left ventricular angiograms of 54 patients suffering from different cardiac diseases were obtained by the image acquisition and processing system Polytron 1000 VR (Siemens AG, Erlangen, FRG). Digital images of both heart casts and patients were evaluated densitometrically and geometrically by two independent observers. In the phantom study the densitometric method exhibited a significantly (p < 0.01) better agreement with the true values than the ALM. The evaluation of left ventricular angiograms in patients comparing densitometry with the ALM demonstrated a relatively high residual deviation (enddiastolic volume Syx = +/- 27 ml, endsystolic volume Syx = +/- 19.4 ml). This is mainly due to systematic, method-related errors of densitometry and the morphometric technique. The intra- and interobserver variability in calculating EF showed a significantly (p < 0.05) smaller residual deviation for densitometry than for ALM; no significant differences were found for the calculation of LV. In conclusion, we demonstrated that the presented densitometric technique offers an objective and simple means of determining LV and EF with comparable reliability and validity to the area-length method.

Absorptiometry, Photon↗

PubMed1993

A new approach for evaluating circadian blood pressure levels and variability from 24 h ambulatory blood pressure profiles.

In 24 h blood pressure monitoring the severity of arterial hypertension is generally classified on the basis of the arithmetic mean of the diastolic blood pressure between 6 AM and 10 PM. In the present study Fourier analysis was used for evaluation of circadian blood pressure level and variability. A common reference profile was calculated on the basis of a group of 50 normotensive profiles. This reference profile is characterized by the fact that the sum of the squares of the distances between the individual profiles and the reference profile is a minimum. The individual 24 h profiles of 103 patients with untreated arterial hypertension were also each described by a Fourier series and were then compared with the normotensive reference profile. The comparison was made not only with respect to the absolute pressure over 24 h but also with respect to the circadian fluctuations in blood pressure. Our results show that the Fourier analysis of 24 h blood pressure profiles presented here can be used for more precise evaluation of 24 h blood pressure profiles.

Adult↗

PubMed1993

[Ambulatory blood pressure monitoring: significance of blood pressure variability for progression of heart hypertrophy].

It is known that ambulatory blood-pressure monitoring gives a better prediction of target organ damage and prognosis than clinical blood pressure. Many studies have found a closer correlation for ambulatory blood pressure with left ventricular hypertrophy than clinical blood pressure. One question that is discussed controversely is whether the variability of blood pressure is also a determinant of target organ damage independent of the average level. In 52 patients with elevated casual blood pressure a 24-h ambulatory blood-pressure measurement (Space Labs 90202) was performed and left ventricular hypertrophy was evaluated by M-mode echocardiography. The following parameters of blood pressure variability were calculated from the profiles: the standard deviation of the mean value, the variation coefficient and the parameter of variability as proposed by Schächinger et al. Furthermore a Fourier analysis of the blood pressure data was performed to quantify blood pressure variability. We found no statistically significant correlation between blood pressure variability and left ventricular mass. However, systolic and diastolic blood pressure level showed a significant correlation with left ventricular hypertrophy (r = 0.45 and r = 0.49, p < 0.05). Thus, blood pressure variability as calculated from the ambulatory, non-invasive blood pressure monitoring is a poor predictor for secondary damage of the heart.

Adult↗

PubMed1992

[Rhabdomyolipoma of the right ventricle].

Echocardiography on a 29-year-old woman with exercise-unrelated tightness in the left chest for some months demonstrated an echo-dense space-occupying lesion in the outflow tract of the right ventricle (RV). Nuclear magnetic imaging revealed an ovular, fat-containing tumour, 3 x 2 x 2 cm in size. Because of threatened obstruction of the RV outflow tract removal of the tumour under cardiopulmonary bypass was undertaken. But complete removal was possible only by resecting a 2 x 3 cm area of the anterior wall of the RV, the resulting defect being covered with a Goretex patch. Histological examination identified the tumour as a rhabdomyolipoma. The patient was free of symptoms 1 year postoperatively.

Adult↗

PubMed1992

Comparative investigation of the influence of nizatidine, ranitidine, and cimetidine on the steady-state pharmacokinetics of theophylline in COPD patients.

The influence of usual regimens of the H2 blocking drugs, cimetidine, ranitidine, and nizatidine on the steady-state plasma concentrations and pharmacokinetic characteristics of theophylline was studied in seventeen patients with chronic obstructive pulmonary disease (COPD). Patients were dosed to steady-state with an oral, sustained-release formulation of theophylline given in therapeutic doses twice daily for 2 weeks. Over the next 4 weeks, each patient received a week-long regimen of each H2 blocker concomitantly with theophylline, and a week-long regimen of theophylline alone (control). At the end of each of the latter 4 weeks the steady-state pharmacokinetics of theophylline were assessed. Neither ranitidine nor nizatidine treatment altered the steady-state pharmacokinetics of theophylline relative to the control phase (i.e. no H2 blocker treatment). Values for theophylline C(ave), Cssmax, AUC0-12, and CLoral were significantly different during cimetidine treatment compared with all other treatments (ranitidine, nizatidine, and control). Cimetidine increased theophylline Cssmax, AUC0-12 and Cave by approximately 32%, and decreased theophylline oral clearance by approximately 23%. The authors conclude that cimetidine alters the steady-state pharmacokinetics of theophylline in COPD patients, whereas ranitidine and nizatidine are without effect.

Administration, Oral↗

PubMed1992

Assessment of spatial and temporal velocity profiles distal of normally functioning Björk-Shiley prosthesis by the Doppler method.

By Doppler echocardiography, the performance of heart valve prostheses is assessed with the aid of maximal transprosthetic velocities, which, however, may not be representative for the full spatial velocity profile in the vicinity of mechanical valve substitutes due to flow separation by the open occluder. The purpose of this study was to determine characteristics of velocity profiles downstream of a normally functioning Björk-Shiley prosthesis. In a pulsatile flow apparatus, different flow rates of 6.3 and 8.4 l/min were delivered. Using a spatially and temporally resolving ultrasonic Doppler method, velocity profiles 20 and 30 mm distal from the prosthesis were registered and displayed in a three-dimensional grid. The spatial velocity profile was found to deviate substantially from a flat profile at these transducer positions at the two flow conditions. Distal to the minor orifice, velocities measured only 70 and 80% of those downstream of the major orifice. In between, a region of relatively slow moving flow was present. The shape of the profiles remained essentially unchanged during acceleration and deceleration of flow. Thus, spatially resolved velocity profiles downstream of mechanical prostheses can be registered by an ultrasonic Doppler device. These findings may be useful for the detection of beginning malfunction both in the experimental and the clinical setting.

Blood Flow Velocity↗

PubMed1992

Assessment of cardiac adrenergic supply in mitral valve prolapse using m-[123I]iodobenzylguanidine scintigraphy.

Presynaptic as well as postsynaptic adrenergic regulation abnormalities are reported in symptomatic patients with mitral valve prolapse. This study was undertaken to evaluate presynaptic sympathetic supply by m-[123I]iodobenzylguanidine scintigraphy in 17 preselected patients with mitral valve prolapse and symptoms suggestive of hyperadrenergic dysautonomia as compared to normal scintigraphic findings. Mitral valve prolapse was echocardiographically proven within the left parasternal long axis view. Percentual activity of m-[123I]iodobenzylguanidine in 33 sectors of all oblique slices along the short axis was calculated relative to the maximal uptake, set at 100%. In general, no significant differences of mean values of sectoral quantitative uptake of m-[123I]iodobenzylguanidine were detectable between patients and the control group. Only in two sectors of the basal anterolateral region P values < 0.01 were present. Thus, using m-[123I]iodobenzylguanidine scintigraphy as marker of cardiac adrenergic supply, no evidence of altered presynaptic hyperadrenergic supply was present in patients with mitral valve prolapse. These findings suggest postsynaptic regulation abnormalities to be preponderant in this condition.

3-Iodobenzylguanidine↗

PubMed1992

Cardiodynamic changes during passive tilt and acute nitrate therapy.

In six patients with normal left ventricles and seven post-myocardial infarction patients cardiodynamic changes during tilt and acute nitrate medication were investigated. The conductance catheter was used for on-line registration of left ventricular volumes and a microtip manometer for high-fidelity pressure recordings. We analysed left ventricular end-diastolic volume index (EDVI) ejection fraction (EF), cardiac index (CI), heart rate (HR), end-systolic pressure (ESP) and end-diastolic pressure (EDP) in the supine position and 30 s after passive upright tilt. Supine and standing measurements were performed without medication and 2 min after acute nitrate medication (0.8 mg sublingual nitroglycerin). After unloading by upright tilt there was a similar reduction of average EDVI in the control group (-18 +/- 7 ml.m2) and in the post-infarction group (-21 +/- 18 ml.m2). The effect of nitroglycerin on EDVI (-12 +/- 4 ml.m2 control, -7 +/- 6 ml.m2 post-infarction) was less than the effect of upright tilt. EF in the control group improved by +8 +/- 5% (in absolute values) during passive tilt; the combined effect of tilt and nitrate was +12 +/- 6% EF (p < 0.05). In the post-infarction group EF did not change significantly during tilt and/or nitrate therapy. In the patients with normal regional ventricular function, CI during tilt was maintained at a constant level. In the post-infarction group the reduction in CI was not significant. Although the reduction in EDVI was similar in the control and infarction groups, the infarction group did not respond to the cardiodynamic change by increasing EF.(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Sublingual↗

PubMed1992

Ventricular performance in relation to heart rate and AV delay at rest.

The influence of heart rate (HR) and AV delay (AVD) on left ventricular haemodynamics was studied in 12 patients classified as having coronary heart disease (CHD), hypertensive heart disease (HHD), dilated cardiomyopathy (DCM) or who served as controls. Using the conductance catheter technique, haemodynamics were measured during pacing rates of 80 to 180 beat.min-1 at AV delays of 0 to 240 ms. A 3-D linear regression analysis of the data quantified the influence of HR and AVD in principle for each group. An increase in HR resulted in a rise in the cardiac index without changing ejection fraction in the control group only, but led to a decrease in these parameters in HHD and DCM; cardiac index remained constant in CHD. CHD patients frequently had a more pronounced left ventricular end-diastolic pressure (LVEDP) elevation with higher HR, whereas left ventricular end-diastolic volume (LVEDV) and stroke volume decreased. In patients with HHD, lengthening of the AVD resulted in an increase in LVEDV and a decrease in LVEDP and left ventricular end-systolic volume (LVESV) leading to a higher ratio of stroke volume to LVEDP than in the other subsets. In DCM, longer AVD also resulted in a higher SV/LVEDP ratio, but in contrast to HHD the influence of AVD variation on LVEDP and therefore on the LVEDV/LVEDP ratio was missing.

Adult↗

PubMed1992

Haemodynamic analysis of atrioventricular tachycardia.

The aim of the study was to delineate the influence of the ventriculo-atrial interval (VAI) in tachycardia with regard to the underlying heart disease. Haemodynamic studies were performed by the conductance catheter technique during paced tachycardia with a HR of 140, 160 and 180 beat.min-1 at various VAI in 10 patients; three with coronary heart disease (CHD), three with hypertensive heart disease (HHD) and four serving as controls. The influence of the VAI accounted for an overall change in cardiac index (CI) of 30 +/- 14%. Alterations in left ventricular peak systolic pressure (LVPSP) depending on VAI were significantly higher (P < 0.01) in CHD patients (32 +/- 9%) than in other groups (14 +/- 9% in the controls and 17 +/- 8% in HHD patients). The influence of VAI on left ventricular end-diastolic pressure (LVEDP) did not differ between the subgroups and accounted for a mean overall change of 32 +/- 14%. Atrial activation during the last third of the cardiac cycle led to the highest values of CI, LVEDP and LVPSP in the control group, whereas in HHD and CHD groups minimal values of CI were correlated with maxima of LVEDP and LVPSP. Conversely, with atrial activation during the medium third of the cardiac cycle minima of CI and LVEDP were observed in the controls, whereas in HHD and CHD patients the highest cardiac index coincided with the lowest LVEDP. Thus tachycardias have different haemodynamic effects depending on the nature of myocardial impairment and the timing of AV coupling.

Atrioventricular Node↗

PubMed1992

In vivo evidence that ethosuximide is a substrate for cytochrome P450IIIA.

The role of various subfamilies of rat hepatic cytochrome P450 in the oxidation of ethosuximide was evaluated by comparing ethosuximide clearance in control rats and those pretreated with relatively selective P450 inducers and/or inhibitors. Clotrimazole pretreatment increased ethosuximide clearance threefold (p less than 0.005). Dexamethasone increased ethosuximide clearance twofold (p less than 0.001), and the dexamethasone effect was completely abolished by a single dose of triacetyloleandomycin. These results suggest a prominent role for cytochrome P450IIIA in ethosuximide metabolism in the rat. Isoniazid increased ethosuximide clearance twofold (p less than 0.001), and this effect was abolished by a single dose of diallylsulfide, suggesting that ethosuximide is also processed by cytochrome P450IIE1 in rats. Phenobarbital pretreatment increased ethosuximide clearance 2-2.7 fold (p less than 0.001); an effect that was only partially reversed by orphenadrine, an inhibitor of cytochrome P450IIB/IIC enzymes. This suggests a quantitatively less important role for the IIB/IIC subfamilies in processing ethosuximide, since phenobarbital is an inducer of P450 subfamilies IIB, IIC, IIE, and IIIA. Neither the cytochrome P450IA inducer, beta-naphthoflavone, nor the inhibitor, alpha-naphthoflavone altered ethosuximide clearance. Ajmaline, an inhibitor of cytochrome P450IID, had no effect on ethosuximide clearance. Together, these findings suggest that ethosuximide is principally oxidized by cytochrome P450IIIA, and that cytochrome P450IIE may play an important role. Cytochromes P450IIB/C play less prominent roles in ethosuximide oxidation, and neither cytochrome P450IA nor cytochrome P450IID is involved.

Animals↗

PubMed1992

[Analysis of circadian blood pressure profiles using Fourier analysis].

Blood pressure is subject to considerable circadian and situational fluctuation. In 24-h blood-pressure monitoring the severity of arterial hypertension is generally classified on the basis of the arithmetic mean of the diastolic blood pressure between 07.00 and 22.00 hours. In the present study Fourier analysis was used to generate continuous functions from the discrete blood-pressure values measured during 24-h blood-pressure monitoring in a sample of 50 normotensive persons aged from 25 to 80 years. A common reference profile was then constructed from these 50 profiles. This reference profile is characterized by the fact that the sum of the integrals over the squares of the distances between the individual profiles and the reference profile is the smallest possible. The reference profile is thus the best approximation of all normotensive profiles and practically ignores individual blood pressure fluctuations. The individual 24-h profiles of 80 patients with untreated arterial hypertension were classified on the basis of the daytime mean as mild, moderate or severe arterial hypertension and also each is described by a Fourier series. The pathological profiles were then compared with the normotensive reference profile. The comparison was made, not only with respect to the absolute pressure over 24 h, but also with respect to the circadian fluctuations in blood pressure. Comparison of the profiles shows that the Fourier analysis of 24-h blood-pressure profiles presented here permits reliable analysis and classification of arterial hypertension and can thus be used for more precise evaluation of the influence of antihypertensives on 24-h blood-pressure profiles.

Adult↗

PubMed1992

[Rate of success and restenosis of PTCA in patients over 75 years of age].

In 82 patients (pts), ages 75-90 years (52 m, 30 f; mean age 77 +/- 3 years) with mainly unstable angina (59 pts) or acute myocardial infarction (7 pts) a PTCA or recanalization was attempted. Successful PTCA was achieved in 57 of 69 pts (83%); occlusions could be reopened in all six pts with myocardial infarction and totally occluded infarct related artery, and in three of seven pts with stable or unstable angina pectoris. The primary success rate of PTCA alone in pts with unstable angina was 81%, and improved to 92% in pts with stable angina. Sixteen procedures were multiple vessel and six were multiple lesion PTCA, so that the lesion-related success rate of PTCA was higher (87%). One patient died in connection with the procedure (procedure related-mortality 1.2%), two pts underwent myocardial infarction (2.4%), one patient emergency bypass grafting (1.2%). The in-hospital mortality was 4.9% and concerned exclusively patients with unstable angina and unsuccessful procedure. Local complications at the puncture site occurred in two patients. The angiographic restenosis rate of PTCA was 58% (44% in patients with stable and 63% in patients with unstable angina pectoris). Seventeen patients with 19 restenoses had successful repeat PTCA; reintervention failed in two patients. We conclude that PTCA can be performed in patients of old age with a resulting comparable primary success rate as in younger patients. Complications seem to be more frequent. The restenosis rate is higher, but with regard to stable and unstable angina, not significantly so. The prognosis in patients with unstable angina and unsuccessful procedure is apparently unfavorable.

Aged↗

PubMed1991

Hypertrophic obstructive cardiomyopathy as a manifestation of a cardiocutaneous syndrome (Noonan syndrome).

The case of a 50-year-old patient with hypertrophic obstructive cardiomyopathy is reported. The patient demonstrated somatic signs of the Turner phenotype, but a cytogenetically normal karyotype was shown. These findings were compatible with the diagnosis of Noonan syndrome. The most commonly diagnosed cardiac disease in this syndrome is pulmonary stenosis, followed by hypertrophic cardiomyopathy. The patient's prognosis is limited by the natural history or the typical complications of the underlying cardiac lesion.

Cardiomyopathy, Hypertrophic↗

PubMed1991

[Magnetocardiography. Biomagnetic localization of impulse development and transmission of the heart].

Magnetocardiography is a non-invasive biomagnetic technique for measuring magnetic fields produced at the surface of the body when the heart is stimulated to beat. The measurement is contact-free and is independent of tissue resistance. For the first time, magnetocardiography employing multi-channel systems permits the accurate, non-invasive localization of accessory conduction pathways and ectopic ventricular activity.

Cardiac Complexes, Premature↗

PubMed1991

Clinical magnetocardiography: experience with a biomagnetic multichannel system.

The magnetic fields caused by the human heart's electrical activity were coherently recorded with a biomagnetic multichannel system (KRENIKON) during 1 to 10 minutes in 49 patients. 31 to 37 magnetic channels were recorded simultaneously with the ECG and respiration. Comparison of a magnetic index and the Sokolow-Lyon index to echocardiographic findings in the quantification of left ventricular hypertrophy demonstrated the superiority of the magnetocardiogram (MCG) as compared to the ECG. The magnetocardiographic investigation of patients with WPW-Syndrome, ventricular extrasystoles, ventricular tachycardia, and paced ventricular beats demonstrated that multichannel magnetocardiography permits the non-invasive three dimensional localization of arrhythmogenic tissue with high spatial accuracy.

Action Potentials↗

PubMed1991

Congenital myocardial sympathetic dysinnervation (CMSD)--a structural defect of idiopathic long QT syndrome.

Concerning the pathogenetic mechanism of idiopathic long QT syndrome (LQTS), the hypothesis of a specific sympathetic imbalance has gained general acceptance, but its validity has never been proven. To test this hypothesis I-123-MIBG, an analogue of norepinephrine and guanethidine, was used to provide scintigraphic display of the efferent cardiac sympathetic innervation. Twelve members of four LQTS families (mean age 38.2 +/- 17.2 years, eight males) and eight healthy volunteers (mean age 48.2 +/- 13.3 years, five males) were studied by means of I-123-MIBG single photon emission computed tomography (SPECT). A quantitative analysis of all scans was performed. All scans of the healthy volunteers show a uniform tracer uptake with sometimes slightly decreased activity in the apex. (1) All patients with QTc greater than 440 msec (n = 5); (2) all, who had suffered from at least one episode of torsade de pointes, ventricular fibrillation (VF) or syncope (n = 5); and (3) all symptomatic patients with QTc prolongation (n = 4) have reduced or abolished (P less than 0.02) MIBG uptakes in the inferior and inferior septal parts of the left ventricle (congenital myocardial sympathetic dysinnervation [CMSD]). Additionally, one female without symptoms or QTc prolongation (LQT) shows an abnormal MIBG SPECT similar to the one of her daughter, who has LQT and symptoms. One male without LQT, who had suffered from VF shows CMSD similar to his father, who has LQT, but no symptoms. All members of the families with normal MIBG SPECTs have neither LQT nor symptoms. In all families CMSD fulfills the criteria of autosomal-dominant inheritance. Normal QTc-interval predicted only in 57% normal cardiac sympathetic innervation in the present LQTS families. Therefore, quantitative I-123-MIBG SPECT enables to identify myocardial sympathetic dysinnervation as structural defect in LQTS. CMSD is associated with and without LQT and presents a pattern of autosomal-dominant inheritance. LQT at rest or during exercise was specific (100%), but less sensitive (63%) in the assessment of CMSD than I-123-MIBG SPECT.

3-Iodobenzylguanidine↗