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Biomedical subjects

B A Angelsen

Publications and source records attributed to B A Angelsen.

44 records · Page 3Linked to original sources
PubMed1976

Transcutaneous measurement of blood flow velocity in the human aorta.

A Doppler velocity meter for measuring blood flow velocity in the human aorta is described. Using pulsed ultrasound, this instrument allows the velocity to be measured at selected depths. The instrument has been tested in laboratory experiments, and appears to give accurate estimates of mean flow velocity for both steady and pulsatile flows. Flow velocities and estimates of stroke volume have been obtained from the ascending aorta in 18 patients. It is suggested that at present only relative values for flow and flow velocity can be measured. A method for obtaining absolute values for these parameters, based on scanning in the aortic arch, is proposed.

Angina Pectoris↗
PubMedDate not supplied

Fetal and maternal aortic flow in two different maternal positions. An investigation with combined Doppler-velocimetry and ultrasonic multiple array.

To study aortic velocities in the fetus, a newly developed multirangegated Doppler velocimeter was combined with a commercial B-mode linear-array apparatus. Spectrum analysis of the Doppler shift signals was performed. The signals with the highest frequencies were selected for hard-copy, and integrated with a digitizer. In the first part of the study, the reproducibility of the method was established by serial measurements of aortic velocity in 7 near-term fetuses. It proved sufficient to evaluate 5 successive heart-cycles. The mean coefficient of variation was 5% (mean number of recordings evaluated 7.5). In the second part of the study, possible influence of aortocaval compression on fetal aortic velocity indicative of changes in fetal cardiac output, was investigated in 10 pregnant women with no symptoms of supine hypotension. Doppler monitoring of the material cardiac output from the suprasternal notch was added to the set-up described to study the supine reduction of cardiac output frequently described in pregnant women. No significant change was found either in the maternal or in the fetal circulation.

Aorta↗
PubMedDate not supplied

The velocity distribution in the aortic anulus in normal subjects: a quantitative analysis of two-dimensional Doppler flow maps.

The velocity distribution in the aortic anulus is commonly assumed to be uniform. A skewed velocity profile may have consequences for the accuracy of volume flow estimates by the Doppler echocardiographic technique. To assess this issue, the velocity distribution in the aortic anulus in 12 normal subjects was studied by computer analysis of digital velocity data from two-dimensional Doppler ultrasound flow maps. The velocity profiles in the aortic anulus were found to be flat but slightly skewed, with the highest velocities toward the septum. There was little interindividual variation. Our findings imply that the centerline velocity is the best estimate for the spatial mean velocity at the aortic anulus in normal subjects. The importance of this finding in patients is unknown. In normal subjects, the results suggest that stroke volume might be overestimated by approximately 15% by Doppler echocardiography if the cross-sectional velocity profile is not accounted for.

Adult↗
PubMedDate not supplied

Transesophageal examination of the left coronary artery with a 7.5 MHz annular array two-dimensional color flow Doppler transducer.

To determine the value of a recently developed 7.5 MHz annular array two-dimensional and color flow Doppler transducer for examination of the proximal parts of the left coronary artery, 25 patients were studied immediately after coronary artery bypass surgery, and the findings were compared with preoperative coronary angiograms. With two-dimensional imaging, the left main coronary artery was visualized in 22 patients (88%), left anterior descending in 13 patients (52%), and circumflex in 22 patients (88%). Stenoses were correctly identified in four of four left main coronary arteries, in five of seven left anterior descending arteries, and in none of four left circumflex arteries. Adding color flow to two-dimensional imaging in 20 patients, we found a disturbed flow signal, as a sign of stenosis, in five of five left anterior descending artery and two of four left circumflex artery stenoses. We concluded that these initial findings with this new 7.5 MHz annular array two-dimensional and color flow Doppler transducer, are promising in imaging and detection of stenoses in the proximal parts of the left coronary artery.

Adult↗
PubMedDate not supplied

Two-dimensional intravascular ultrasound: technical development and initial clinical experience.

This article reviews the development and current status of catheter-based, intravascular ultrasound imaging. The first section provides an introduction to some of the general technical issues encountered in the design of the catheter imaging systems and compares the potential merits of the multiple-element versus the mechanical approach. The second section of the article reviews the data from early studies correlating the intravascular ultrasound images with histologic sections (in vitro) and angiography (in vivo). The article concludes with a discussion of potential clinical applications and future technical developments.

Coronary Disease↗
PubMedDate not supplied

Systemic arterial compliance early and late after a first acute myocardial infarction.

Systemic arterial properties and left ventricular function were assessed by Doppler echocardiography and a calibrated subclavian artery pulse tracing early (5 weeks) and late (27 months) after a first acute myocardial infarction in 19 patients aged 44-77 years and in healthy subjects matched for age, gender, and arterial blood pressure. Total arterial compliance (3-element windkessel model) was reduced by 26% (p < 0.001) from early to late assessment, and left-ventricular end-diastolic and end-systolic volumes were increased by 11 and 18%, respectively (p < 0.05). Peripheral resistance and characteristic impedance were not significantly changed. The healthy matched subjects had arterial compliance similar to patients at early assessment, but tended to be higher at late. Thus, 2.3 years after a first acute myocardial infarction with moderate left ventricular dilatation, arterial distensibility was significantly decreased whereas peripheral resistance was not changed.

Adult↗
PubMedDate not supplied

Intra-arterial ultrasound: a potential tool for the vascular surgeon. Clinical review.

Intra-arterial ultrasound is a new real-time imaging technique using a miniaturized transducer in a catheter to image diseased arteries. The small size and close proximity to the structures being imaged allow the use of frequencies from 20-40 MHz, resulting in high resolution images. In addition to the stenotic lumen, it is possible to examine the composition and eccentricity of the plaque, as well as structures outside of the vessel. Such information can be used for planning and evaluating vascular interventions. The addition of Doppler measurements allows the evaluation of function as well as anatomy. Research applications include studies of lesion progression, measurement of arterial elasticity, quantitative blood flow velocities and study of intra-arterial flow patterns. Although this technique is in its infancy, it is highly probable that it will prove to be a useful aid to the vascular surgeon.

Arteries↗