Jude Medical Bileaflet Mechanical Heart Research Articles

Oval housing for the St. Jude Medical bileaflet mechanical heart valve.

The St. Jude Medical bileaflet mechanical heart valve was approved by the Food and Drug Administration in late 1970s. The basic idea for the design of the valve is simply two semicircular flat plates pivoting on hinges. The overall performance of St. Jude Medical valves such as blood flow being central, the leaflets opening completely, and the pressure drop across the valve being trivial is satisfactory. St. Jude Medical valves provide an improved hemodynamics compared to the other mechanical heart valve models; however, their non-physiological hemodynamics which may lead to red blood cells lysis and thrombogenicity still remains a major issue. In this study, we hypothesize that applying ovality to the housing might improve their hemodynamics significantly which is based on the fact that the native annulus is oval by nature. A quick but precise numerical model based on the finite strip method was developed by which the regurgitation flow volume and velocity of the proposed design were assessed in the closing phase. The results are satisfactory and an improved hemodynamics is observed. The proposed design can be considered for further numerical and experimental studies and shows promise and merits further development.

Hemodynamic Performance and Thrombogenic Properties of a Superhydrophobic Bileaflet Mechanical Heart Valve.

In this study, we explore how blood-material interactions and hemodynamics are impacted by rendering a clinical quality 25mm St. Jude Medical Bileaflet mechanical heart valve (BMHV) superhydrophobic (SH) with the aim of reducing thrombo-embolic complications associated with BMHVs. Basic cell adhesion is evaluated to assess blood-material interactions, while hemodynamic performance is analyzed with and without the SH coating. Results show that a SH coating with a receding contact angle (CA) of 160° strikingly eliminates platelet and leukocyte adhesion to the surface. Alternatively, many platelets attach to and activate on pyrolytic carbon (receding CA=47), the base material for BMHVs. We further show that the performance index increases by 2.5% for coated valve relative to an uncoated valve, with a maximum possible improved performance of 5%. Both valves exhibit instantaneous shear stress below 10N/m2 and Reynolds Shear Stress below 100N/m2. Therefore, a SH BMHV has the potential to relax the requirement for antiplatelet and anticoagulant drug regimens typically required for patients receiving MHVs by minimizing blood-material interactions, while having a minimal impact on hemodynamics. We show for the first time that SH-coated surfaces may be a promising direction to minimize thrombotic complications in complex devices such as heart valves.

Effect of heart rate on the hemodynamics of bileaflet mechanical heart valves' prostheses (St. Jude Medical) in the aortic position and in the opening phase: A computational study.

To date, to the best of the authors' knowledge, in almost all of the studies performed around the hemodynamics of bileaflet mechanical heart valves, a heart rate of 70-72 beats/min has been considered. In fact, the heart rate of ~72 beats/min does not represent the entire normal physiological conditions under which the aortic or prosthetic valves function. The heart rates of 120 or 50 beats/min may lead to hemodynamic complications, such as plaque formation and/or thromboembolism in patients. In this study, the hemodynamic performance of the bileaflet mechanical heart valves in a wide range of normal and physiological heart rates, that is, 60-150 beats/min, was studied in the opening phase. The model considered in this study was a St. Jude Medical bileaflet mechanical heart valve with the inner diameter of 27 mm in the aortic position. The hemodynamics of the native valve and the St. Jude Medical valve were studied in a variety of heart rates in the opening phase and the results were carefully compared. The results indicate that peak values of the velocity profile downstream of the valve increase as heart rate increases, as well as the location of the maximum velocity changes with heart rate in the St. Jude Medical valve model. Also, the maximum values of shear stress and wall shear stresses downstream of the valve are proportional to heart rate in both models. Interestingly, the maximum shear stress and wall shear stress values in both models are in the same range when heart rate is <90 beats/min; however, these values significantly increase in the St. Jude Medical valve model when heart rate is >90 beats/min (up to ~40% growth compared to that of the native valve). The findings of this study may be of importance in the hemodynamic performance of bileaflet mechanical heart valves. They may also play an important role in design improvement of conventional prosthetic heart valves and the design of the next generation of prosthetic valves, such as percutaneous valves.

Hemodynamic study of the elliptic St. Jude Medical valve: A computational study.

Despite successful implantation of St. Jude Medical bileaflet mechanical heart valves, red blood cell lysis and thrombogenic complications associated with these types of valves are yet to be addressed. In our previous study, we proposed an elliptic housing where 10% ovality was applied to the housing of St. Jude Medical valves. Our preliminary results suggested that the overall hemodynamic performance of St. Jude Medical valves improved in both the closing and opening phases. In this study, we evaluated the hemodynamics around the leaflets in the opening phase using a more sophisticated computational platform, computational fluid dynamics. Results suggested both lower shear stress and wall shear stress values and an overall improved hemodynamic performance in the proposed design. This improvement is characterized by lower values of shear stress and wall shear stress in the regions downstream of the leaflets, lower pressure drop across the valve and smaller recirculation zones in the sinuses areas. The proposed design may open a new chapter in the concept of design and hemodynamic improvement of the next generation of mechanical heart valves.

Elliptic St. Jude Medical bileaflet mechanical heart valve

Elliptic St. Jude Medical bileaflet mechanical heart valve

Numerical analysis for the structural strength comparison of St. Jude Medical and Edwards MIRA bileaflet mechanical heart valve prostheses

This paper presents a numerical analysis for the structural strength comparison of the St. Jude Medical bileaflet mechanical heart valve prosthesis with flat leaflet and the Edwards MIRA bileaflet mechanical heart valve prosthesis with curved leaflet. Computer aided engineering systems are used in the analysis. The blood fluid pressure is applied to both flat and curved leaflets of the bileaflet mechanical heart valve prostheses for the rigid body dynamic analysis to confirm the almost same dynamic characteristics of both flat and curved leaflet motions. Thereafter, using the same blood fluid pressure and dynamic characteristics of leaflet motions, structural mechanic analyses for both flat and curved leaflets of the mechanical heart valve prostheses are carried out to show quite different stress and deformation results, respectively. Conclusively, from the viewpoint of stress, it is revealed that the St. Jude Medical bileaflet mechanical heart valve prosthesis is structurally stronger and better than the Edwards MIRA bileaflet mechanical heart valve prosthesis. Computer aided engineering systems used in this comparative structural analysis are ADAMS for the rigid body dynamic analysis, and NISA for the structural mechanic analysis.

Prospective randomized comparison of CarboMedics and St. Jude Medical bileaflet mechanical heart valve prostheses: Ten-year follow-up

This is the final report of a randomized controlled trial comparing the performance of CarboMedics (CarboMedics Inc., Austin, Tex) and St. Jude Medical (St. Jude Medical Inc, St Paul, Minn) bileaflet mechanical heart valve prostheses 10 years after surgery. Between 1992 and 1996, 485 patients undergoing mechanical heart valve replacement were randomized to receive CarboMedics (n = 234) or St. Jude Medical (n = 251) prostheses for aortic (n = 288), mitral (n = 160), or double (n = 37) valve replacements. Patients were followed annually to the end of 2004. Demographic, preoperative, and operative characteristics were similar between the 2 groups. The median follow-up was 10 years in both groups (CarboMedics 99% complete, St. Jude Medical 98% complete; 3879 patient-years of follow-up). Overall, 165 patients died, 25 of valve-related causes. Ten-year survivals were 66.4% (95% confidence interval: 59.6%-72.3%) and 64.7% (95% confidence interval: 58.0%-70.6%) in the CarboMedics and St. Jude Medical groups, respectively (P = .94). Freedom at 10 years from valve-related mortality was 95.0% (95% confidence interval: 90.8%-97.3%) in the CarboMedics group and 93.0% (95% confidence interval: 88.3%-95.9%) in the St. Jude Medical group. During follow-up, 34 patients had a thromboembolic event, 79 patients had at least 1 bleeding event, and 14 patients required reoperation. There were no significant differences between the groups with respect to freedom from complications (P > or = .12); freedom from thromboembolism at 10 years (CarboMedics: 91.5%, 95% confidence interval: 86.5%-94.7%; St. Jude Medical: 92.2%, 95% confidence interval: 87.5%-95.2%); freedom from bleeding events (CarboMedics: 83.0%, 95% confidence interval: 76.6%-87.8%; St. Jude Medical: 77.5%, 95% confidence interval: 71.1%-82.7%); and freedom from death or valve-related complication (CarboMedics: 51.6%, 95% confidence interval: 44.7%-58.0%; St. Jude Medical: 46.2%, 95% confidence interval: 39.7%-52.4%). Linearized rates per patient-year were 1.1% in the CarboMedics group and 0.8% in the St. Jude Medical group for thromboembolism; 2.3% in the CarboMedics group and 3.2% in the St. Jude Medical group for bleeding events; and 0.72% in the CarboMedics group and 0.47% in the St. Jude Medical group for nonstructural valve dysfunction. International normalized ratio values were similar between the 2 groups throughout the study period. At 10 years, the clinical outcome was similar with respect to these 2 mechanical bileaflet prostheses.

Flow‐induced Platelet Activation in a St. Jude Mechanical Heart Valve, a Trileaflet Polymeric Heart Valve, and a St. Jude Tissue Valve

Polymer heart valves have been under investigation since the 1960s, but their success has been hampered by an overall lack of durability mainly due to calcification of the leaflets and a relatively high rate of thromboembolic complications. A new polymer (Quatromer) trileaflet design was tested for its thrombogenic potential and was compared to that of existing prosthetic heart valves routinely implanted in patients: a St. Jude Medical bileaflet mechanical heart valve (MHV) and a St. Jude porcine bioprosthetic tissue valve. The valves were mounted in a left ventricular assist device and the procoagulant activity of the platelets was measured using a platelet activation state (PAS) assay. The PAS measurements indicated that the platelet activation level induced by the polymeric valve was very similar to that induced by the St. Jude Medical MHV and the St. Jude tissue valve. No significant difference was observed between the three valves, indicating that they have a comparable thrombogenic potential.

Regurgitant flow field characteristics of the St. Jude bileaflet mechanical heart valve under physiologic pulsatile flow using particle image velocimetry.

The regurgitant flow fields of clinically used mechanical heart valves have been traditionally studied in vitro using flow visualization, ultrasound techniques, and laser Doppler velocimetry under steady and pulsatile flow. Detailed investigation of the forward and regurgitant flow fields of these valves can elucidate a valve's propensity for blood element damage, thrombus formation, or cavitation. Advances in particle image velocimetry (PIV) have allowed its use in the study of the flow fields of prosthetic valves. Unlike other flow field diagnostic systems, recent work using PIV has been able to relate particular regurgitant flow field characteristics of the Bjork-Shiley Monostrut valve to a propensity for cavitation. In this study, the regurgitant flow field of the St. Jude Medical bileaflet mechanical heart valve was assessed using PIV under physiologic pulsatile flow conditions. Data collected at selected time points prior to and after valve closure demonstrated the typical regurgitant jet flow patterns associated with the St. Jude valve, and indicated the formation of a strong regurgitant jet, in the B-datum plane, along with twin vortices near the leaflets. Estimated ensemble-average viscous shear rates suggested little potential for hemolysis when the hinge jets collided. However, the vortex motion near the occluder tips potentially provides a low-pressure environment for cavitation.