Isotropic pyrocarbon has low radiopacity indeed. Pyrocarbon of which valves are made contains 10 % of boron. Due to presence of boron strength of the material rises significantly and low radiopacity appears on the considerable width of the material. The leaflets are visible with angiograph in profile but they are transparent full-face.
In conditions of stable, non-turbulent laminar flow the leaflets rotate strictly clockwise. They make one full turn in 100 – 600 cycles. This characteristic is checked for each valve during a pulse-duplicator test. Video of a valve tested with a pulseduplicator is attached. Though in vivo when the blood flow is unstable, unstable rotation, no rotation, counterclockwise rotation or vibration is possible. This process can be observed using an angiograph.
Loudness of the working valve depends on the myocardium condition and patients body weight. We did not carry out any research for reducing valve sonority.
The real opening angle of the leaflets is 85 º, indeed. During the valve development process I carried out special hydrodynamic research to choose the optimal opening angle of the leaflets. When the angle is bigger than 85 º the gradient decreases not significantly but regurgitation rises a lot. Leaflets of “Cardiamed” valves have complex bent shape. At the valve entrance they are parallel to the flow and on the exit they aren’t. Thus gradient on the valve stays low and the flow force applied to the leaflets grows significantly. It speeds up opening and closing of the valve and stabilizes the opening angle. Many other valves with flat leaflets have a problem with leaflets hanging when the opening angle is approximately 80 º and autovibration (“flutter”) effect.
There are three types of sewing rings according to ISO 5840: intra-, supra- and intra-supraannular. Prosthesis with intra-annular sewing ring takes place fully inside the fibrous ring of the operated valve. It causes significant constriction of hydraulic orifice and rise of gradient. These sewing rings are not popular among cardiac surgeons so we don’t produce them. Valve with supra-annular sewing ring takes place fully above the fibrous ring. Thus effective hydraulic orifice widens and pressure gradient decreases. We produce this type of sewing rings. But not all of the surgeons prefer this type of sewing ring. Most of the surgeons who use a method of sewing when fibrous ring is turned inside out (is everted) prefer intrasupra-annular cuff. In this case only a part of the sewing ring is inside the fibrous ring. Pressure gradient rises slightly but sewing becomes more hermetic, risk of fistula decreases and it’s much easier to change the suture thread with pledget if it breaks.
No event of hemolysis was revealed during the clinical investigation. This is mentioned in records and reports including Indian congress. Maybe it just was not accentuated. Hemolysis is not a problem for modern prostheses.
Using of non-relevant prosthesis size can cause an odd irregular compression of the valve housing by the heart muscles. As a result housing deformation is possible; gap between hosing and leaflets changes and leaflets become impeded. It’s a common problem for all bileaflet pyrocarbon prostheses. Thus manufacturers recommend anti-anatomical position of the prosthesis because anatomical position can bring to locking the leaflets in the hinge or non-simultaneous closing when the valve is under compression.
We have just started this research. First results confirm the leaflets rotation. We hope after the research is finished we will give the comprehensive answer.
The significant depth of the valve housing gives a possibility of simplifying the operation and saving leaflets and chordae tendinae of the operated heart valve. “Cardiamed” valves are preferable in this kind of operations because the risk of leaflets blocking is reduced due to the high valve housing used as a protector.
We were given some explanted prosthetic valves after reoperations caused by endocarditis, pannus and thrombosis. The longest running time of a valve was 13 years. Reoperation was carried out due to the pannus growth in conditions of pregnancy. No signs of deterioration was revealed. A leaflet rotation was confirmed by weak traces all over the contact surface on housing. Investigation of the valve with a pulse-duplicator fully confirmed its functionality. Characteristics like pressure gradient and regurgitation did not change compared with the archive data for this valve.
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