PubMed Health⌕ Search

Biomedical subjects

F Cassot

Publications and source records attributed to F Cassot.

11 recordsLinked to original sources
PubMed1992

Near velocity field downstream prosthetic valves in aortic position.

Using a cardiovascular simulator to duplicate in vitro the flow conditions through valves in aortic position, bidimensional velocity maps very near the valve are reconstructed, from an ultrasonic 8 Mhz doppler system, in an elastic model of the ascending aortic arch. Three mechanical heart valves representative of the different types of commercial models (a tilting disc, a ball in cage and a two-leaflet valve) and a new bileaflet prototype were investigated. From examination of the velocity field, it is possible to define the main characteristics of the valve wake and to observe the development of negative velocities associated with regurgitant flows. From a comparison with tests in rigid tubes, the role played by the arch elasticity is analysed.

Aortic Valve↗
PubMed1987

Velocity field of a Björk-Shiley valve prosthesis: influence of the disc orientation.

An experimental investigation was carried out on the development of physiological flows downstream of a Björk-Shiley valve prosthesis. The post-valvular velocity field was determined by an ultrasonic method in an elastic model of the aortic arch. The flow development in the ascending aorta was strongly dependent on the orientation of the tilting disc. The rotating direction of the vortices and the site of the maximum velocity were influenced by the orientation.

Aorta↗
PubMed1987

[In vitro determination of the pressure-diameter relationship and velocity profiles by ultrasonic technics. In vivo application].

A good knowledge of arterial flow mechanics and of the phenomena associated with fluid-boundary interactions is necessary for the determination of some fundamental parameters such as velocity, pressure and pressure-diameter relationship during a cardiac cycle. Ultrasonic techniques were developed on a test bench and directly applied to animals without major modification. On such a test bench allowing a good simulation of physiological type flows, velocity field and pressure-diameter relationship were determined. In vivo application of these techniques allowed a systematic analysis of velocity profiles in the rabbit abdominal aorta and a precise approach of rheological properties of the vascular wall.

Animals↗
PubMed1985

Velocity profiles in the wake of two prosthetic heart valves using a new cardiovascular simulator.

In this paper we present a study of the post valvular flow field on a new cardiovascular simulator including an elastic model of the aortic arch. Transverse and vertical two-dimensional velocity measurements are performed with an ultrasonic velocimeter. Two prosthetic heart valves are tested in the aortic position. The behaviour of the velocity vectors patterns during one pulsatile cycle is one of the most striking features of the flow.

Aorta, Thoracic↗
PubMed1978

Heat and mass transfer of a thermal indicator in pulsatile flow through the cardio-pulmonary system. I. Modeling.

The construction of a physico-mathematical model which describes the mechanism of indicator dispersion in the circulation and which fits the thermal dilution curves (TDC) is presented. Because of its more evident physical meaning, formulation of the problem in terms of heat and mass transfer is preferred to stochastic theory. Hypotheses necessary to simplify the general system of governing equations are clearly defined and discussed. This deductive method leads to a one-dimensional convective heat transfer model in which pulsatility and form of injection appear naturally. Simulations of TDC in constant and pulsatile flow cases are performed on a digital mini-computer which demonstrates the model's ability to represent different experimental or clinical observations. This will facilitate hemodynamic parameter identification from TD techniques and will increase the accuracy of this identification.

Aorta↗
PubMed1978

Heat and mass transfer of a thermal indicator in pulsatile flow through the cardio-pulmonary system. II. Identification of cardiac output.

Hamilton's celebrated formula for cardiac output measurement is simple but its validity is dependent on several methodologic requirements which are not generally fulfilled, particularly in thermal dilution. A quite different method, based on a physico-mathematical model of the indicator dispersion in the circulation, is proposed. It allows direct derivation of cardiac output once the model's parameters have been identified. Combined deconvolution and least squares procedures are used with truncated data for this identification. Numerical tests and application to clinical observations are presented. Both limitations and possibilities of further developments in estimation of pulsatile flow conditions from TD technique are discussed.

Blood Circulation↗
PubMed1975

Mechanical aspect of the heart sound emission.

The present paper deals with a physical study of the relation between the phonocardiogram and left ventricular pressure (LVP) fluctuations. Fourier analysis comparison of the two signals-simultaneously recorded either on pathologic human hearts or during experiments on dogs-does not point out an obvious relation between the phonocardiogram and a linear combination of the first pressure derivatives.-A mechanical model of the heart enabling the description of the sound emission mechanism provides a qualitative relation between the phonocardiogram and LVP fluctuations: the acceleration of the thoracic area is equal to the product of LVP by a time function depending on the mechanical properties of the muscle. - A theoretical thoracic acceleration obtained by transformation of the experimental LVP is compared with the experimental phonocardiogram through linear filtering analysis. The theoretical signal is in good agreement with the experimental one.

Fourier Analysis↗