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Biomedical subjects

R T Brownlee

Publications and source records attributed to R T Brownlee.

31 records · Page 2Linked to original sources
PubMed1980

In vitro assessment of mitral valve prostheses.

The performance of five prosthetic mitral valves (Ionescu-Shiley, Hancock, Carpentier-Edwards, Starr-Edwards, and Björk-Shiley), all of the same nominal size (29 mm), has been assessed in a hydromechanical simulation of the left heart at three pulse rates. The mean and maximum transvalvular pressure differences, the observed and/or calculated area, and the energy loss for each valve were compared. It was found that each measure of performance rates the valves in the same order or merit, with the Ionescu-Shiley valve performing the best and the Hancock the worst among the valves tested.

Biomechanical Phenomena↗
PubMed1979

Construction and evaluation of a hydromechanical simulation facility for the assessment of mitral valve prostheses.

A hydromechanical simulator of the human left heart and systemic circulation system has been built for evaluating the dynamic actions of mitral valve prostheses. The facility includes a transparent and compliant model ventricle pumping into a simulation of the systemic circulation impedance. Transparent materials permit detailed high speed photography of valve action from the left ventricular aspect. This action has been analyzed by digitizing the valve open area and computing the variation of area with time. Additionally, pressures across and flows through the valves have been measured. Comparison has been made between the maximum observed valve open areas and the areas computed using the appropriate pressure and flow measurements substituted in clinically used equations.

Heart Valve Prosthesis↗
PubMed1976

The in vitro assessment of left ventricular flow patterns on the closure of a new mitral valve "bioprosthesis".

A new pulse duplication system, which we feel closely simulates not only the geometry but the pressure and flow phenomena in the left heart under phasic conditions, has been developed. A new mitral valve replacement, in a truncated cone or frustum configuration is being evaluated, utilizing this test facility. Flow patterns around the mitral valve appear to close the leaflets well prior to the onset of gradient reversal across the orifice.

Coronary Circulation↗
PubMedDate not supplied

The in vitro function of 19-mm bioprosthetic heart valves in the aortic position.

1. The new pericardial valves tested showed better hydrodynamic performance than the porcine and the St. Jude Medical mechanical valves. 2. The Ionescu-Shiley III valve exhibited the best hydrodynamic performance, with the least transvalvular energy loss. 3. Transvalvular energy loss shows that the major loss across the 19 mm valves occurs during the forward-flow phase. 4. Our data compares well with data from other in vitro tests performed using different test apparatus. 5. The pericardial bioprostheses, in particular, function well in the 19 mm size and therefore offer an alternative to the increased operative risk associated with valve over-sizing or orifice enlarging procedures. 6. The performance of the two porcine valves tested were comparable with each other.

Animals↗