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Biomedical subjects

P Decoodt

Publications and source records attributed to P Decoodt.

29 records · Page 2Linked to original sources
PubMed1979

Assessment of left ventricular filling by echocardiography in normal subjects and in subjects with coronary artery disease and with asymmetric septal hypertrophy.

To examine the time course of left ventricular filling, a computerized analysis of echocardiograms was performed in 16 normal subjects, 10 patients with coronary artery disease (CAD) but no cardiac enlargement and 7 patients with asymmetric septal hypertrophy (ASH). After hand-controlled digitization of the echocardiogram, a plot of the left ventricular diameter time-curve demonstrated separate phases of rapid filling, slow filling and atrial contribution. The left ventricular diameter at end-systole and at the end of the three diastolic phases was determined by pattern analysis of the diameter-time curve. On analysis of successive beats in the normals, the coefficient of variation for each of these four values of the left ventricular diameter was less than +/- 5%. Between CAD, ASH and normals there was no significant difference in left ventricular end-diastolic diameter, nor in the extent and percentage of diameter shortening during systole. In contrast, abnormalities of the filling pattern were found in CAD and ASH. The maximal rate of diameter lengthening was not different in CAD (13.0 vs 13.7 cm/sec in normals, N.S.) but decreased in ASH (9.3 cm/sec, p less than .01). The percentage of diameter lengthening occurring in the rapid filling phase was decreased in both patient groups (55% in CAD and ASH vs 73% in normals, p less than .001). The slow filling phase did not contribute to more diameter lengthening (13% in CAD and 17% in ASH vs 12% in normals, N.S.). In CAD and ASH, the atrial contribution was markedly increased (33% in CAD and 28% in ASH, vs 15% in normals, p less than .001), and there was a higher rate of diameter lengthening during the atrial contraction (7.6 cm/sec in CAD, p less than .001 and 5.7 cm/sec in ASH, p less than .01, vs 3.1 cm/sec in normals). In conclusion, after computer processing, noninvasive measurements of the left ventricular diameter allows to identify a typical filling pattern in patients with CAD and ASH, consistent with an abnormal compliance of the left ventricle and a compensatory increased atrial contribution.

Adult↗
PubMed1975

Determination of glomerular intracapillary and transcapillary pressure gradients from sieving data. II. A physiological study in the normal dog.

The two theoretical models proposed previously to calculate the intracapillary and transcapillary glomerular pressure gradients from the sieving of macromolecules such as PVP have been used to analyse in 22 normotensive dogs the sieving curve relating the sieving coefficients, phi, to molecular size (phi: glomerular clearance of PVP fractions/GFR). Neither the "local c2" model-filtrate unmixed at the outer face of the capillaries walls--nor the constant c2 model-filtrate well mixed--allowed to obtain realistic values for the hemodynamical parameters. Indeed with the local c2 model, the best fit between calculated and experimental sieving curves could be obtained only by reversing the intracapillary pressure gradient; conversely the constant c2 model obliged to decrease the intracapillary pressure so abruptly along the capillaries, that retrofiltration took place in the distal parts of the vessels. This difficulty has been overcome by combining the two models; the so-called "hybrid model" considers that the filtrate is well mixed in the vicinity of the urinary pole only. The following results were obtained: 1. PGCa and PGCe (intracapillary pressures at the afferent and efferent extremities of the capillaries) equal to 49.7 +/- 1.03 and 41.8 +/- 1.00 mm Hg respectively. 2. Pressure equilibrium is generally reached at the efferent extremity of the vessels. 3. The slope of PGC (see article) varies inversely to FF. (filtration fraction). 4. The model, however, does not allow to rule out the possibility of retrofiltration.

Animals↗
PubMed1975

Determination of glomerular intracapillary and transcapillary pressure gradients from sieving data. I. A mathematical model.

Determination of glomerular intracapillary and transcapillary pressure gradients from sieving data. A biomathematical model is described to calculate the intracapillary and transcapillary glomerular pressure gradients from the sieving coefficients (phi: fractional clearances/GFR) of macromolecules such as polyvinylpyrrolidone (PVP). Two differential equations have been developed. The first one calculates local values for GFR in terms of local values for PGC (intracapillary hydrostatic pressure) and pi (oncotic pressure). The second equation calculates the clearance of PVP equimolecular fractions, the sieving equations previously described (24) being used to derive the concentrations of PVP in the filtrate (c2). Two variants of the second equation have been considered, assuming the filtrate in contact with the membrane either "well stirred" or "unstirred" (constant c2 and local c2 gradient models respectively). Computer simulations have been used to illustrate how the sieving curve is modified when the five parameters on which depends the shape of the curve are changed one by one. The sieving curve relates phi to a(s) (hydrodynamically equivalent molecular radius). The determining parameters are: GFP, the mean effective glomerular filtration pressure, epsilon, the slope of the intracapillary pressure, FF, the filtration fraction, Cp0, the protein concentration in arterial plasma and r, the pore radius which is the only structural parameter involved when one assumes the glomerular membrane crossed by cylindrical pores of uniform size and length. The shape of the sieving curve is modified significantly enough by changing GFP, FF and r within reasonable limits, to make it possible to derive GFP and r from experimental sieving data for macromolecules such as PVP or dextrans.

Capillaries↗
PubMed1975

A model for sieving of macromolecules by the glomerular membrane of the kidney.

The transport of water and of macromolecules across the glomerular membrane of the kidney depends on the membrane parameters (radius, length and number of pores) as well as on the hydrostatic and oncotic pressures on either side of the membrane. The filtration pressure decreases along the capillary loops from afferent to efferent end. Water and solute flows are thus given by a system of two differential equations. The sieving coefficient of the macromolecules is the ratio of solute to water flow. In the program described the differential equations are solved by the Runge-Kutta method (fourth order). Rosenbrock's method of minimization is used to adjust the theoretical to the experimental sieving coefficients. The pore radius, total pore area per unit of path length and conductance of the membrane, as well as the intracapillary hydrostatic pressure and its gradient can thus be determined.

Biological Transport↗
PubMed1975

The role of membrane parameters and of filtration pressure in the determination of the shape of the polyvinylpyrrolidone sieving curve. An in vitro and in vivo study.

The theoretical equations describing the transport of a solute across a porous membrane predict that the shape of the sieving curve (ratio of solute concentrations in filtrate and filtrand versus molecular size) depends not only on the porosity of the membrane but also on the filtration pressure. This has been verified experimentally on an artificial membrane (Amicon XM-50). This model has been used to interpret the effects of angiotensin II on the shape of the glomerular 125I PVP sieving curve. The mean effective filtration pressure is increased by the intrarenal perfusion of angiotensin II.

Angiotensin II↗
PubMed1973

Measurement of the permeability of biological membranes. Application to the glomerular wall.

The transport equation describing the flow of solute across a membrane has been modified on the basis of theoretical studies calculating the drag of a sphere moving in a viscous liquid undergoing Poiseuille flow inside a cylinder. It is shown that different frictional resistance terms should be introduced to calculate the contributions of diffusion and convection. New sieving equations are derived to calculate r and A(p)/Deltax (respectively, the pore radius and the total area of the pores per unit of path length). These equations provide a better agreement than the older formulas between the calculated and the experimental glomerular sieving coefficients for [(125)I]polyvinylpyrrolidone (PVP) fractions with a mean equivalent radius between 19 and 37 A. From r and A(p)/Deltax, the mean effective glomerular filtration pressure has been calculated, applying Poiseuille's law. A value of 15.4 mm Hg has been derived from the mean sieving curve obtained from 23 experiments performed on normal anesthetized dogs.

Biological Transport↗
PubMedDate not supplied

The spectrum of mitral regurgitation in idiopathic mitral valve prolapse: a color Doppler study.

To characterize the spectrum of mitral regurgitation in mitral valve prolapse, one hundred patients were studied by color Doppler flow mapping. The findings were correlated with the clinical presentation and with the possible complications. Mitral regurgitation was absent in 46 patients, mild in 26 patients, moderate in 18 patients and severe in 10 patients. The jet orientation was central in 15 patients, antero-medial in 13 patients and postero-lateral in 26 patients. The regurgitation was early systolic in 7 patients, late systolic in 20 patients and holosystolic in 27 patients. A good agreement was observed between the color flow patterns and the presence, timing and radiation of a murmur. Systolic clicks were not predictors of the presence or the severity of regurgitation. The grade of mitral regurgitation was positively correlated with, age, left heart enlargement and valvular redundancy. No sex difference was observed. The prevalence of serious arrhythmias or cerebral ischemic events was not significantly increased when a regurgitation was present.

Adolescent↗
PubMedDate not supplied

[Myocarditis].

The definition, pathogenesis and clinical picture of myocarditis are reviewed. Recent studies emphasize the importance of immune mechanisms in the genesis of the myocardial damage. Among particular forms of myocarditis, Coxsackie B viral infections, HIV infections, Lyme disease and Chagas disease are successively considered. The main measures for the treatment of myocarditis remain a restriction of physical activities along with the classical medications of heart failure. Due to the increased embolic risk, anticoagulation is often indicated.

Chagas Disease↗