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Biomedical subjects

M M Webb-Peploe

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

At least 19 recordsLinked to original sources
PubMed1992

Is angiographic ventriculography necessary for the assessment of ischemic patients?

A total of 53 patients with a provisional diagnosis of ischemic heart disease and without any clinical evidence of valvular, congenital, or primary muscle heart disease were studied by echocardiography and biplane left ventricular cineangiography. For angiographic ejection fraction analysis, a program developed in our department for use on an Apple Macintosh computer interfaced to a digitizing tablet was employed. Echocardiographic outlines of systolic and diastolic images were traced with a digitizing system on the screen and ejection fractions were calculated by a program incorporated in the echo machine. Good echo windows allowing ejection fraction calculations were present in 35 patients. There was a good correlation between angiographic and echocardiographic ejection fraction (r = 0.7, SEE = 0.09), and wall motion assessment revealed no significant discrepancies between the two image modalities. The remaining 18 patients had poor echo windows, preventing accurate echocardiographic determination of the ejection fraction. However, limited assessment of left ventricular size and wall motion was possible in all patients and allowed the identification of those who had impaired left ventricular function as judged by angiography (angiographic ejection fraction < 35%). We conclude that even in patients with poor echo windows echocardiographic assessment of left ventricular function provides clinical information similar to angiography which should not be considered mandatory for the investigation of ordinary ischemic patients.

Cardiac Catheterization↗
PubMed1992

Mechanical restitution of isolated human ventricular myocardium subjected to in vivo pressure and volume overload.

OBJECTIVE: The aim was to make a comparison of the mechanical and electrical refractory properties of isolated strips of human ventricular myocardium obtained from patients with either left ventricular pressure overload, volume overload, or normal left ventricular function. METHODS: Strips of ventricular myocardium were obtained at the time of cardiac surgery from 17 patients with aortic stenosis, representing pressure overload, 14 patients with aortic regurgitation, representing volume overload, and nine patients with mitral stenosis, representing normal left ventricular function. Muscle strips were mounted isometrically in a tissue bath, superfused with physiological saline at 37 degrees C, and stimulated at 1 Hz. Mechanical restitution curves were constructed from the isometric twitch tension obtained from extrastimuli during a special stimulus protocol. Transmembrane action potentials were recorded using glass microelectrodes and restitution of the upstroke velocity of action potentials studied in the presence of high external potassium concentration. RESULTS: The aortic stenosis group was older and had higher left ventricular systolic pressures and thicker left ventricular walls than the other groups. Electrocardiographic evidence of left ventricular hypertrophy was present in both the aortic stenosis and aortic regurgitation groups. Peak tension, time to peak tension, and the maximum rates of rise and fall of tension were not significantly different between groups. The time constant of the initial rapid recovery phase of mechanical restitution (tau 1) was prolonged in the aortic stenosis group, at 603(SEM 80) ms v 367(53) ms in the aortic regurgitation group (p < 0.005), and 259(70) ms in the mitral stenosis group (p < 0.005). There was a positive correlation between tau 1 and left ventricular wall thickness (p < 0.05). Neither "normal" nor "slow" (in the presence of raised external potassium) transmembrane action potentials differed in the groups studied. The mean time constant of recovery of "slow" action potential dV/dtmax was slower in the aortic stenosis group, but this difference was not significant. CONCLUSIONS: These data are consistent with the hypothesis that the rate of recovery of calcium release from the sarcoplasmic reticulum is slowed in myocardial hypertrophy due to pressure overload in man and provides a possible explanation of the occurrence of mechanical alternans in such patients.

Action Potentials↗
PubMed1991

Primary restrictive cardiomyopathy: clinical and pathologic characteristics.

Twenty-four patients with restrictive cardiomyopathy were identified at St. Thomas' Hospital during a 17-year period. All had endomyocardial biopsy, but in two patients the biopsy specimens were small and nondiagnostic. Seven patients had amyloidosis and five had other specific heart muscle diseases. The remaining 10 patients with primary restrictive cardiomyopathy had myocyte hypertrophy or interstitial fibrosis, or both. Patients with primary restrictive cardiomyopathy presented earlier but survived longer after presentation than did those with amyloidosis. In each group, survival after cardiac catheterization was related to cardiac index but not to filling pressures. Primary restrictive cardiomyopathy was associated with complete heart block in four patients, two of whom had skeletal myopathy. One had a family history of dominantly inherited skeletal myopathy. Primary restrictive cardiomyopathy was present in a mother and daughter. Two other patients had a family history of heart failure, sudden death or complete heart block, alone or in combination, at a young age. Restrictive hemodynamics and complete heart block were present in patients even in the absence of significant fibrosis. The data suggest that primary restrictive cardiomyopathy may be a distinct myopathy with dominant inheritance and incomplete penetrance that is expressed morphologically as myocyte hypertrophy and interstitial fibrosis. Skeletal myopathy may be associated with the cardiomyopathy.

Adolescent↗
PubMed1991

Echocardiographic left ventricular wall thickness: a poor predictor of the severity of aortic valve stenosis.

Echocardiographic left ventricular hypertrophy is thought to be helpful in grading the severity of aortic stenosis. This study compared M-mode echocardiographic left ventricular wall dimensions with Gorlin aortic valve area. Good quality echocardiograms were obtained in 294 patients with aortic stenosis who also underwent cardiac catheterization. Patients with grade 3 or 4 aortic regurgitation were excluded. The correlation was calculated between the aortic valve area and the left ventricular wall dimensions. Correlation coefficients were poor; r = 0.13 for the septum, r = 0.15 for the posterior wall, and r = 0.17 for the mean wall dimension. Correlation was not improved significantly if patients with poor left ventricular function or systemic hypertension were excluded. Correlation with other hemodynamic parameters was better, peak left ventricular systolic pressure having r values of 0.36 and 0.30 for posterior wall and septum. Mean and peak aortic valve gradient had r values approaching 0.30 for both dimensions. If the peak gradient was included in multivariate analysis, the wall dimensions then had no predictive power for severity of aortic stenosis. This study demonstrates that the degree of left ventricular wall hypertrophy is not related to the severity of aortic outflow obstruction and therefore cannot be used to grade the severity of aortic stenosis.

Aortic Valve↗
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↗