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Biomedical subjects

M Anliker

Publications and source records attributed to M Anliker.

At least 37 records · Page 2Linked to original sources
PubMed1987

[Doppler sonography assessment of blood flow velocity in the ascending aorta. Problems and possible solutions].

Irregularities of the transvascular distribution of blood flow within the human ascending aorta have been documented by means of 16 Doppler gates positioned along one scanline of a sector scanner. The velocity profiles recorded from ten healthy adults, ten patients suffering from hypertrophic obstructive cardiomyopathy, ten patients suffering from hypertrophic nonobstructive cardiomyopathy, and ten patients with severe aortic insufficiency exhibited nonuniformities which varied not only from individual to individual but also between the groups and depending on the phase of the cardiac cycle. These variations prevent any local measurement from being representative for the instantaneous mean velocity in all cases. A reliable mean should therefore be determined by simultaneously taking into account all velocities within the vascular cross-section. A computer simulation in order to indicate a potential solution to this problem demonstrates that an annular array transducer can be excited in such a manner that it produces a homogeneous ultrasound beam of a transverse area a hundred times larger than the one obtained in the conventional maximally focussed mode.

Aorta, Thoracic↗
PubMed1986

Combined two-dimensional ultrasound Doppler technique. New possibilities for the screening of renovascular and parenchymatous hypertension?

A combination of a real time phased array sector scanner and a range-gated 16-channel pulsed Doppler system was used for the evaluation of renal artery flow patterns in 25 echogenic subjects. Eight of these had renal artery stenosis, 5 an increased peripheral resistance in the kidney, and 12 showed normal renal flow patterns with consistent forward flow during the entire heart cycle. In normals, the ratio of end systolic (S2) versus early peak systolic (S1) velocity was 0.52 +/- 0.11 (range 0.37-0.84). In the patients with renal artery stenosis S2/S1 ranged from 0 to 0.30. Five of the 8 patients with renal artery stenosis could be evaluated before and after percutaneous transluminal dilatation (PTA). After successful PTA (diameter reduction less than 50% and pressure gradient less than 20 mm Hg) S2/S1 returned to normal. The patients with increased peripheral resistance due to an angiographically proven small kidney exhibited a variety of flow patterns with S2/S1 ranging from 0 to 0.29, similar to the ones with renal artery stenosis. The results suggest that the noninvasive determination of the ratio S2/S1 with the aid of ultrasound Doppler measurements permits a differentiation between normal and abnormal flow patterns and can be applied for the follow-up of patients after PTA. In utilizing the described method, neither the angle between the Doppler beam and the vessel axis, nor the vessel diameter must be evaluated.

Adolescent↗
PubMed1985

Dynamics of aortic flow in hypertrophic cardiomyopathy.

The purpose of this study was to reassess left ventricular ejection dynamics in hypertrophic cardiomyopathy, to investigate whether a premature stoppage of ejection occurs, as previously reported, and whether reliable criteria for left ventricular outflow tract obstruction can be established by non-invasive evaluation of aortic flow patterns. In a group of 21 patients with hypertrophic cardiomyopathy, composed of 9 with the obstructive form (HOCM), 9 with the non-obstructive form (HNCM) and 3 with apical hypertrophy (HACM), instantaneous flow velocities across the ascending aorta were determined non-invasively with a 16-gated Doppler 2-D echo instrument. Ten normals served as controls. The 16 flow velocities were averaged over 8 heart beats and the relative volume flow rate was calculated by microprocessor analysis. Ejection time (i.e. flow time) derived from the flow curves was compared with the available ejection period as determined from the carotid pulse tracing. In normals, ejection time amounted to 94 +/- 3% of the available ejection period, in HOCM to 92 +/- 5% and in HNCM to 93 +/- 4% (no significant differences). In HACM, however, ejection time was reduced to 71 +/- 14% of the available ejection period. In contrast to HNCM, aortic flow in HOCM was characterized by an early peak followed by a plateau at a sizably lower flow level for the rest of systole. Flow time of an abnormally short duration was the hallmark of HACM. We conclude that in patients with hypertrophic cardiomyopathy, HOCM and HNCM can be distinguished by the shape of their volume flow curves. A premature stoppage of ejection is only found in patients with HACM.

Adult↗
PubMed1985

Comparison of intravenous digital subtraction cineangiocardiography with conventional contrast ventriculography for the determination of the left ventricular volume at rest and during exercise.

Left ventricular volumes were determined by means of digital subtraction cineangiocardiography (DSA) which was performed in the right anterior oblique projection after contrast agent injection into the superior vena cava. Monoplane end-diastolic (EDV), end-systolic volumes (ESV), and ejection fraction (EF) were calculated using the 'area-length' method and were compared with the same parameters obtained by conventional left ventricular cineangiocardiography. A first group of 20 patients was studied at rest and a second group of 10 patients during bicycle exercise at a work load of 64 watts during 2 min, by DSA and conventional cineangiocardiography. Three different subtraction modes were evaluated: (1) mask mode subtraction (MMS), (2) time interval difference (TID) method and (3) a combination of MMS and TID called MMS + TID method. With the MMS method good correlations were obtained for EDV, ESV and EF at rest (r greater than 0.91) and during exercise (r greater than 0.91). The TID method showed only moderate correlations for patients at rest (r greater than 0.86) and during exercise (r greater than 0.79). Similar results as with MMS were achieved by the combined method (MMS + TID) at rest (r greater than 0.91) and during exercise (r greater than 0.91). Interobserver variability indicated a high reproducibility for all methods except for TID during exercise. It is concluded that DSA is an accurate technique for left ventricular volume determination not only at rest but also during exercise. The best results are obtained with MMS or MMS + TID methods, while left ventricular contour detection is easier and more convenient with MMS + TID.

Adult↗
PubMed1985

The microvasculature of the small-intestinal mucosa of the rat: quantification of hemodynamic effects of topically applied cimetidine, ranitidine, somatostatin, and vasopressin.

The influence of topically administered cimetidine, ranitidine, somatostatin, and vasopressin on microvessels of the jejunal villus of the rat was investigated by means of an in vivo videomicroscopy technique. For all substances a dose-response curve concerning the change of vessel diameters was obtained. All four drugs induced a significant vasoconstriction at the capillary level. Maximum vasoconstriction was achieved with vasopressin. These results strongly suggest the presence and possibly importance of H2 receptors in the intestinal vascular bed of the rat.

Animals↗
PubMed1984

A comparison between single gate and multigate ultrasonic Doppler measurements for the assessment of the velocity pattern in the human ascending aorta.

The velocity pattern in the ascending aorta of 15 healthy adults was measured quasisimultaneously from the Doppler-shifts produced in 16 gates distributed equally within the cross-section along a narrow ultrasound beam which centrally traversed the vessel upstream of the brachiocephalic trunk. A comparison between the time integrals of the velocities in gates 9 (centre line), 4 and 13 (off centre) and the time integral of the weighted mean of the velocities of all gates correlated with r = 0.90, SEE = 1.05 (gate 9), r = 0.90, SEE 0.88 (gate 4) and r = 0.92, SEE 0.94 (gate 13). A better correlation (r = 0.96, SEE = 0.60) was found between the linear mean of all gates and the weighted mean. These results show that Doppler measurements in single small gates are not appropriate to determine the average cross-sectional blood flow velocity in healthy adults.

Adult↗
PubMed1984

Bone loss in premenopausal and postmenopausal women. A cross-sectional and longitudinal study using quantitative computed tomography.

Trabecular and total bone densities were determined by quantitative computed tomography in patients with untreated postmenopausal osteoporosis and in normal premenopausal and postmenopausal women. A special procedure was used for precise low-dose examinations of the distal end of the radius and the distal end of the tibia. The results indicate that the trabecular bone density of the peripheral skeleton is a reliable index of postmenopausal osteoporosis. In general, osteoporotic patients could be distinguished from patients with age-related bone loss based on differences in the magnitude of the decrease in trabecular bone density. Serial determinations of trabecular bone density in individual patients indicated that trabecular bone loss in postmenopausal osteoporotic patients shows a step-wise pattern in which phases of relative stability are followed by brief phases of bone loss. Quantitative computed-tomography measurements of bone density should provide a better understanding of the pathogenesis of postmenopausal osteoporosis and be useful in the assessment of different methods of treatment.

Adult↗
PubMed1984

Idiopathic osteoporosis in a three-year-old girl. Follow-up over a period of 6 years by computed tomography bone densitometry (CT).

In a girl suffering from idiopathic transient osteoporosis the development of vertebral deformation and recovery could be followed from the age of 3.4 to 9.3 years. Computed bone densitometry (CT) revealed values below normal for trabecular bone density (-2.6 SD at 4.3 years and -2.8 SD at 5.3 years) during the clinically symptomatic phase of the disease and normalization after the age of 6 years (-0.2 SD at 6.7 and 9.3 years). Cortical bone mineral parameters measured by CT and metacarpal bone measurements from conventional X-rays showed values at the lower range of normal and only a weak correlation with clinical symptoms, vertebral deformation and recovery, respectively. CT may probably allow to diagnose osteoporosis before the appearance of deformities or fractures; in milder forms of osteoporosis the diagnosis may be possible by CT only.

Bone Development↗
PubMed1983

Corticosteroid-induced bone loss. A longitudinal study of alternate day therapy in patients with bronchial asthma using quantitative computed tomography.

Treatment with corticosteroids can produce osteoporosis. It is generally held that bone loss occurs when steroids are administered daily, but recent findings indicate that bone may also be lost on alternate day therapy. Cortical and trabecular bone, which may be affected differently, can be assessed independently, by quantitative computed tomography. This technique has been applied to the appendicular skeleton in following 20 patients with bronchial asthma during one year of chronic alternate day corticosteroid therapy. The trabecular bone loss was considerable; prednisone 25 mg on alternate days caused an average reduction in trabecular bone of 3.5% over one year. Bone loss was dose- and age-dependent. Young patients on 50 mg/2 days lost up to 17% trabecular bone in one year. Cortical bone was not significantly affected over the same period.

Adrenal Cortex Hormones↗
PubMed1982

[Pregnancy and labor after closed mitral valve commissurotomy].

Among 171 women who had undergone mitral valvulotomy at childbearing age, 47 had a total of 62 postoperative pregnancies. The cardiological findings before and after valvulotomy show the patients with pregnancy to be a positive selection of all patients who had mitral valvulotomy in Zurich. 10% of the pregnancies were complicated by atrial fibrillation or heart failure. Three deaths related to pregnancy and birth were registered. The NYHA functional classes III and IV are considered to be contraindications for postoperative pregnancy. Other risk factors are discussed. Based on physical examination, electrocardiography, chest x-ray, ergometry and echocardiography, a woman wishing to have a child after mitral valvulotomy should be advised of the cardiological risk. During pregnancy, regular follow-up by both obstetrician and cardiologist must be expressly required.

Abortion, Spontaneous↗
PubMed1981

Development of stereopsis and cortical binocularity in human infants: electrophysiological evidence.

Dynamic random-dot stereograms and correlograms were used to elicit visually evoked brain potentials from human infants, and these potentials were compared with potentials evoked by classical checkerboard pattern reversal. The results indicate that infants begin to produce stereoscopically evoked potentials at the age of 10 to 19 weeks, several weeks after showing classical checkerboard-evoked potentials, and suggest that the onset of cortical binocularity precedes stereopsis.

Age Factors↗
PubMed1981

Quantification of trabecular bone with low dose computed tomography.

Computed tomography (CT) has the potential of providing a precise quantification of trabecular bone. A special purpose low dose CT system for applications at peripheral measuring sites has been developed. With this system, the quantification of trabecular bone can be achieved with a reproducibility on the order of 0.3%. It has been used successfully in pilot studies of immobilization osteoporosis in children and adults on a week by week basis. Currently, the method is being used in a preliminary investigation of bone loss in women in an attempt to differentiate normal changes from changes due to postmenopausal osteoporosis. Results obtained so far indicate that intervals of 3 months are adequate for following the natural course of osteoporosis or its response to therapy on an individual basis.

Adult↗