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Biomedical subjects

M M Webb-Peploe

Publications and source records attributed to M M Webb-Peploe.

At least 37 records · Page 2Linked to original sources
PubMed1991

Thrombus within a submitral left ventricular aneurysm: diagnosis on cross sectional echocardiography.

Subvalvar left ventricular aneurysms are rare and occur predominantly in black Africans. A submitral left ventricular aneurysm was diagnosed on cross sectional echocardiography in a black woman born in the United Kingdom. The left parasternal long axis view showed a highly echogenic mass apparently attached to the wall of a dilated left atrium, but the apical two-chamber view showed that this was thrombus in the apex of a left ventricular aneurysm. The patient subsequently underwent surgical correction.

Adult↗
PubMed1990

Cardiac phase-related variability of border detection or densitometric quantitation of postangioplasty lumens.

We applied an automated computer program capable of simultaneous geometric (through border detection) and densitometric quantitation of digital angiograms for evaluation of the results of percutaneous transluminal coronary angioplasty (PTCA) in different phases of the same cardiac cycle. Digital subtraction coronary angiograms (DSA) of 28 patients who had undergone PTCA to a total of 30 lesions, were analyzed in diastole, in systole, and in the middle of the cardiac cycle to test the variability in coronary quantitation resulting from random frame selection relative to cardiac phase. Before PTCA there was a low degree of variation between measurements obtained from the same lesion in different phases of the cardiac cycle, in both geometric (coefficient of variation between cardiac phases = 4.2%) and densitometric (coefficient of variation between cardiac phases = 5.1%) quantitation. After PTCA, however, there was a wider variation of values in different cardiac phases, which predominated in the densitometric measurements (coefficient of variation between cardiac phases = 33.6%, compared to 20.6% for geometric measurements). There was less agreement between different post-PTCA phases in densitometry, and discrepancies as large as 47% could occur in densitometric evaluation of the stenotic areas when different phases of the cycle were used. We concluded that border detection or densitometric quantitation of the postangioplasty lumens is subject to greater variation resulting from random frame selection relative to cardiac phase, as compared to preangioplasty assessment. This variation predominates in densitometric quantitation, which seems to be dependent not only on the radiographic projection but also on the cardiac phase. The usefulness of densitometric techniques for the evaluation of PTCA results appears to be questionable.

Angiography, Digital Subtraction↗
PubMed1990

Predictors of the rate of success of angioplasty of the left circumflex artery.

Out of 45 angioplasties attempted by the same cardiologist for stenosis of the left circumflex artery at St. Thomas' Hospital in a one and a half year period, six were unsuccessful due to inability to cross the lesion. In four of these cases, the lesion was crossed with the guide wire but not with the balloon. All these failures, and sixteen of the successful cases, were studied by means of geometrical analysis of the anatomy of the circumflex artery and computer-assisted automated quantitation of digital subtraction coronary angiograms obtained at the time of the procedure. The quantitative characteristics of the lesion (the proportional diameter of the stenosis; the proportional geometric area of the stenosis and the proportional densitometric area of the stenosis) were not significantly different between the cases resulting in failure or success. Similarly, the angles of the circumflex artery proximal to the stenosis, the distance of the lesion from the orifice of the artery and the length of the main stem of the left coronary were not different between the two groups. The group in which the angioplasty was unsuccessful had significantly longer lesions, however, whereas the ratios of the diameter (or the geometric area) of the distal part of the vessel beyond the lesion as compared with the proximal (reference) part were significantly lower in the group undergoing successful dilatation. We conclude that neither the angulation of the circumflex artery as it appears on a two-dimensional projection nor the proportional diametric stenosis of the lesion can serve as easily assessible predictors fro the success of the procedure.(ABSTRACT TRUNCATED AT 250 WORDS)

Angioplasty, Balloon, Coronary↗
PubMed1989

Relation between interatrial shunts and decompression sickness in divers.

The prevalence of right-to-left interatrial shunts was determined by contrast echocardiography in a blind comparison of 61 divers who had had decompression sickness, divided into four predetermined clinical subgroups, and a control group of 63 who had not. The prevalence of shunt was 15/63 in the controls and did not differ significantly in 24 divers with onset of neurological symptoms more than 30 minutes after surfacing (4/24) or 6 with joint pain only (1/6). In divers who had neurological symptoms within 30 minutes of surfacing the prevalence of shunt was 19/29, significantly higher. Rashes soon after surfacing were related to shunts but late rashes were not.

Decompression Sickness↗
PubMed1989

Cold-induced pulmonary oedema in scuba divers and swimmers and subsequent development of hypertension.

The effect of cold and/or a raised partial pressure of oxygen was examined in eleven people with no demonstrable cardiac abnormality but who had pulmonary oedema when scuba diving or surface swimming, and in ten normal divers. These stimuli induced pathological vasoconstriction in the pulmonary oedema group, nine of whom also showed signs of cardiac decompensation when so stimulated. The pulmonary oedema patients have been followed-up for an average of 8 years. Seven have become hypertensive. Except for the onset of lone atrial fibrillation in one normotensive female diver and development of Raynaud's phenomenon in a normotensive man, there have been no cardiovascular events and no deaths.

Acute Disease↗
PubMed1989

Use of a hollow wire to facilitate angioplasty of occluded vessels.

An USCI 0.038 inch (0.97 mm) floppy tipped hollow wire was used to facilitate the passage of angioplasty guide wires across severe stenoses or vessel occlusions before balloon angioplasty. The hollow wire was passed through a standard 7 or 8 French gauge Judkins coronary catheter to establish whether the obstruction could be breached. This reduced the cost of failure because angioplasty guiding systems were not committed to procedures that were unlikely to be successful. The hollow wire provides stability for the passage of the guide wire and can be used to measure distal pressure and inject contrast. To date it has been used in a total of 15 cases of occluded vessels; it failed to cross the lesion in four cases. Successful angioplasty followed in all patients in whom the lesion was crossed.

Adult↗
PubMed1989

Inaccuracies in using aortic valve gradients alone to grade severity of aortic stenosis.

The severity of aortic stenosis is an important determinant of prognosis in patients with symptoms who do not undergo valve replacement. To assess the pitfalls of using valve gradients alone 636 patients with aortic stenosis in whom the aortic valve area had been calculated by the Gorlin formula were studied. The correlation between valve area and aortic gradients was poor. No gradient was found that was both sensitive and specific for aortic stenosis. The maximum predictive accuracy was 81% for a mean gradient of 30 mm Hg and 80% for a peak gradient of 30 mm Hg. A mean gradient of 50 mm Hg or a peak gradient of 60 mm Hg were specific with a 90% or more positive predictive value. It proved difficult, however, to find a lower limit with a 90% negative predictive value. Patients with severe aortic stenosis and low gradients (peak or mean gradient of less than 30 mm Hg) had small ventricles (on both angiographic and echocardiographic data) with good ejection fractions and so were unlikely to be detected subjectively. In comparison patients with mild aortic stenosis and low gradients tended to have more aortic regurgitation but have similar degrees of left ventricular hypertrophy on echocardiographic or electrocardiographic criteria. The aortic valve area should be measured in all patients with the suspicion of severe aortic stenosis with a mean gradient of less than 50 mm Hg (50% of patients in this study) or a peak gradient of less than 60 mm Hg (47% of patients in this study).

Age Factors↗
PubMed1988

Assessment of coronary angioplasty: comparison of visual assessment, hand-held caliper measurement and automated digital quantitation.

Digital subtraction coronary angiograms (DSA) of 27 patients who had undergone coronary angioplasty (PTCA) to a total of 32 lesions were analyzed using an automated border-detecting computer program and hand-held caliper measurement of diameter percent stenosis. The results were compared with visual interpretation of the 35-mm cineangiograms. Visual reports significantly overestimated the pre-PTCA diameter percent stenosis (P less than .001) and underestimated the residual post-PTCA narrowing compared with the automatic computer program (P less than .001). Caliper measurements overestimated significantly the pre-PTCA stenosis in comparison with the computer (P less than .01), but post-PTCA the two methods did not differ significantly (P = .105). There was a positive but poor correlation between caliper and computer measurements (r = .43, P less than .05) performed on the pre-PTCA digital angiograms. Post-PTCA the two methods correlated better (r = 0.78, P less than .001), but further statistical analysis showed important discrepancies between them. The correlation of visual reports and computer measurements was poor pre-PTCA (Kendall's tau = 0.32, P less than .05) and not statistically significant post-PTCA (tau = 0.64, P = .5). We conclude that there is observer bias in the visual reporting of angioplasty results, so that pre-PTCA lesions are overestimated, whereas post-PTCA are underestimated. Hand-held caliper measurement improves the assessment of coronary stenoses in comparison with the visual report but still may not altogether eliminate observer bias; it may overestimate the pre-PTCA stenoses compared with automated border detection.

Analog-Digital Conversion↗
PubMed1986

Streptokinase treatment of thrombosed mitral valve prosthesis monitored by Doppler ultrasound.

A case of prosthetic mitral valve thrombosis treated with streptokinase is described. The diagnosis was made and the treatment was monitored using Doppler ultrasound. Doppler may be superior to other non invasive methods for this application because of its ability to grade the dysfunction more accurately and avoid bleeding complications associated with cardiac catheterization.

Adult↗
PubMed1986

Effects of verapamil on haemodynamic function and myocardial metabolism in patients with hypertrophic cardiomyopathy.

The effect of 20 mg dose of intravenous verapamil was studied over a range of heart rates in 12 patients with hypertrophic cardiomyopathy. Six patients had an appreciable left ventricular outflow tract gradient and six did not. The drug reduced myocardial oxygen consumption in proportion to a reduction in the development of left ventricular pressure. The negative inotropic effect of verapamil was counteracted by the drug's non-specific vasodilator activity, so that cardiac index was unaltered at any heart rate and as a result myocardial efficiency was unaffected by the drug. Verapamil did not consistently alter myocardial metabolism. Some patients showed improvement in anaerobic myocardial metabolism after verapamil but an equal number showed impairment of lactate metabolism. It was not possible to predict from clinical features, echocardiographic findings, or haemodynamic variables measured before administration of verapamil which patients would demonstrate haemodynamic or metabolic improvement after the drug. In this short term study no mechanism was demonstrated by which patients with hypertrophic cardiomyopathy might obtain a consistent improvement from treatment with verapamil.

Adolescent↗
PubMed1985

Blood flow.

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Aortic Valve↗