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D S Macpherson

Publications and source records attributed to D S Macpherson.

33 records · Page 2Linked to original sources
PubMed1984

Common femoral artery Doppler wave-forms: a comparison of three methods of objective analysis with direct pressure measurements.

Doppler maximum frequency wave-forms recorded from the femoral arteries of 50 patients with arterial disease have been submitted to three methods of objective analysis in an attempt to quantify the degree of proximal narrowing. The methods were compared with direct femoral artery pressure measurements at rest and during hyperaemia. There was marked overlap between the results of both pulsatility index and Laplace transform damping when compared with pressure assessment. Principal component analysis, however, produced significantly better agreement than Laplace transform damping (chi 2 = 5.8, P less than 0.02) and in addition was found to be sensitive to the presence or absence of disease in the superficial femoral artery. Principal component analysis appears to be the most powerful method of Doppler wave-form analysis so far described and may have a place in the non-invasive assessment of the aorto-iliac segment.

Aorta, Abdominal↗
PubMed1982

On-line classification of arterial stenosis severity using principal component analysis applied to Doppler ultrasound signals.

Principal component analysis is a powerful method of feature extraction which can be applied to continuous-wave Doppler waveforms. A microprocessor system for the on-line calculation of the coefficients of principal components has been devised and tested in an experimental model. Doppler waveforms were obtained from positions distal to stenoses of known severity implanted in the iliac arteries of three dogs and classified into one of four groups. By reference to data from a previous series of experiments the microprocessor correctly classified 75% of stenoses. The remaining 25% were all classified as being one group more severe than they actually were.

Animals↗
PubMed1982

Changes in Doppler ultrasound sonagrams at varying distances from stenoses.

The effect of different degrees of arterial stenosis on Doppler ultrasound sonagrams recorded from various distances downstream has been investigated in a canine model. It has been found that even mild stenoses give rise to considerable disturbances close to the stenosis, and that more severe stenoses give rise to greater disturbances which propagate further downstream. The distance the disturbances travelled was not related to stroke volume, and it was only for stenoses of 88% area reduction and greater that such disturbances ever propagated beyond one stroke-length. Quantitative assessment of moderate degrees of proximal stenosis using continuous wave Doppler ultrasound will not be reliable unless the distance between the major stenosis and the recording site is known.

Animals↗
PubMed1982

Pyogenic liver abscess: a study of forty-four cases in two centres.

44 patients with pyogenic liver abscess, 22 each from Leicester, UK, and Göteborg, Sweden, presenting between 1972 and 1980 have been reviewed. 29 patients were diagnosed prior to specific treatment with 3 deaths (10%); 15 patients were first discovered at autopsy resulting in an overall mortality of 41%. The presentation, pathogenesis, and treatment are discussed in detail. It is concluded that the continuing high mortality of this condition largely relates to the difficulty in establishing the diagnosis. Reduced morbidity (and perhaps mortality) might be achieved with wider use of percutaneous methods of drainage.

Adolescent↗
PubMed1981

The salvage of occluded Dacron grafts.

The technical details of unblocking occluded Dacron grafts in 8 patients are described. The early results in 4 grafts in 8 patients are described. The early results in 4 unilaterally occluded bifurcation aortic grafts and 1 unilateral iliofemoral graft are encouraging with all 5 grafts patent 8-16 months postoperatively (mean 9 months). We recommend this operation as the procedure of choice in symptomatic patients presenting with a graft occlusion of this type before resorting to the insertion of a new prosthesis, and emphasize the importance of improving the outflow, usually by a profundaplasty. Only 1 out of 5 axillofemoral grafts remains patent at 8 months in spite of vigorous attention to operative detail. In this situation, an alternative procedure is suggested in the long term.

Aged↗
PubMed1981

The effect of proximal stenosis on Doppler waveforms: a comparison of three methods of waveform analysis in an animal model.

Methods of quantifying changes in spectrum analysed Doppler waveforms have been assessed in an experimental canine model. Artificial stenoses of varying (0-95%) area reduction have been inserted in the iliac artery of five anaesthetised greyhounds. 133 sets of Doppler waveforms recorded distally have been subjected to principal component analysis (PCA), transfer function analysis (TFA) and pulsatility index calculation (PI). Transfer function damping factor delta and PI were only able to distinguish those stenoses of greater than 85% area reduction. PCA, however, was more reliable in this range, and was usually able to distinguish stenoses of 65% and 77% area reduction. We conclude that PCA deserves further assessment in patients with aorto-iliac disease.

Animals↗
PubMed1980

Is aortography abused in lower-limb iscaemia?

Request for aortography on 82 patients in one hospital in 1978 were assessed to determine the effect of the investigation on the patient's subsequent management. In 49% of cases the request was fully justified. In the remaining 51% of patients, none of whom had reconstructive surgery, the request was considered either inappropriate (38%) or of marginal value (13%). The reasons for this high porportion of unnecessary aortograms were related to the clinical specialty and the level of experience of the doctor making the request. A simple algorithm which may be helpful when deciding to perform an aortogram is suggested. It is concluded that aortography should be requested only by experienced medical staff and only after a decision has been taken to offer the patient operative treatment.

Aortography↗