St. Jude Medical Valve Research Articles

PROSE: Prospective Randomized Trial of the On-X Mechanical Prosthesis and the St Jude Medical Mechanical Prosthesis Evaluation: Part 2: Study results—prostheses, positions, and economic development

ObjectivesThe Prospective Randomized On-X Mechanical Prosthesis Versus St Jude Medical Mechanical Prosthesis Evaluation (PROSE) trial purpose was to investigate whether a current-generation mechanical prosthesis (On-X; On-X Life Technologies/Artivion Inc) reduced the incidence of thromboembolic-related complications compared with a previous-generation mechanical prosthesis (St Jude Medical Mechanical Prosthesis; Abbott/St Jude Medical). This second report documents the valve-related complications by individual prostheses and by Western and Developing populations. MethodsThe PROSE trial study was conducted in 28 worldwide centers and incorporated 855 subjects randomized between 2003 and 2016. The study enrollment was discontinued on August 31, 2016. The study protocol, and analyses of 10 demographic variables and 24 risk factors were published in detail in 2021. ResultsThe total patient population (N = 855) included patients receiving an On-X valve (n = 462) and a St Jude Medical valve (n = 393). The overall freedom evaluation showed no differences at 5 years between the prostheses for thromboembolism or for valve thrombosis. There were also no differences in mortality. There were several differences between Developing and Western populations. The freedom relations at 5 years for mortality favored Western over Developing populations. Valve thrombosis was differentiated by position and site: aortic < mitral (P = .007) and Western < Developing (P = .005). In the mitral position there were no cases in Western populations, whereas there were 8 in Developing populations (P = .217). ConclusionsThe On-X valve and St Jude Medical valve performed equally well in the study with no differences found. The only differentiation occurred with valve thrombosis in the mitral position more than the aortic position and occurring in Developing more than Western populations. The occurrence of valve thrombosis was also related to a younger population possibly due to anticoagulation compliance based on record review.

Characteristic localization patterns of thrombus on various brands of bileaflet mitral mechanical heart valves as assessed by three-dimensional transesophageal echocardiography and their relationship with thromboembolism.

Three-dimensional transesophageal echocardiography (3D-TEE) provides detailed images of prosthetic valve thrombosis (PVT). However, data regarding PVT localization patterns based on 3D-TEE and their association with clinical findings among various bileaflet mitral prosthetic valve brands is lacking. The locations of thrombi were classified into 4 groups according to hinge and annulus involvement based on 3D-TEE: ring-like PVT involving entire mitral annulus (type-1), PVT involving peri-hinge(s) region and extends through some part of the annulus (type-2), PVT involving mitral annulus without involving hinge(s) region (type-3), and PVT involving only (peri)hinge(s) area (type-4). This study was conducted in 265 patients (male: 71, mean age: 46.3 ± 12.7years) with mitral PVT, including 150 St Jude Medical (SJM), 65 Carbomedics, 29 Medtronic ATS open-pivot, and 21 Sorin bileaflet mechanical valves. There was a significant difference in most common PVT localization patterns between different prosthetic valves (type-1 for Carbomedics and Sorin; type-2 for SJM and type-3 for ATS valves; p < 0.001). Additionally, PVT involving only (peri)hinge region(s) (type-4) was mostly observed in patients with SJM valves (18%). (Peri)hinge(s) area involvement was observed in the majority of study patients (78.1%). In patients who presented with thromboembolism, the most common PVT localization pattern was type-1 (53%). Increased age, low international normalized ratio on admission, PVT with a mobile part > 2mm, type-1 and type-4 PVT were associated with thromboembolic events. In conclusion, thrombus can be displayed in distinct locations in several types of bileaflet mechanical valves due to different design, hinge and pivot mechanisms, which can be complicated with thromboembolic events.

The Apex bileaflet mechanical heart valve

Mechanical Heart Valves (MHVs) are known for their excellent lifespan and feasibly are the most reliable and stable valves amongst all prosthetic valves. Successful bileaflet MHVs such as the St. Jude Medical (SJM) are known for providing central blood flow and minimal pressure drop across the valve. However, due to their non-physiological flow conditions, they still suffer from hemodynamic complications, that is, red blood cell (RBC) lysis and/or thrombogenicity, to date. Our hypothesis is that the design of MHVs can be improved so that their hemodynamics can be comparable to those of tissue valves. In this study, a new concept for the design of MHVs is proposed. To accomplish this, we identified the major design limitations of bileaflet MHVs, such as the gold standard SJM valve as well as the believed contributing factors to their thrombogenicity. We developed a novel design architecture for bileaflet MHVs that addressed these limitations, and from it, the Apex Valve (AV). Our experimental assessment of the AV found that its hemodynamics were closer to that of a bioprosthetic valve than of a bileaflet MHV. This design has been filed as a US Provisional Patent.

A turbulence in vitro assessment of On-X and St Jude Medical prostheses

ObjectiveThe objective of this study was to investigate and compare the hemodynamic and turbulence characteristics upon implantation of St Jude Medical (SJM) (St Jude Medical, St Paul, Minn) and On-X (On-X Life Technologies, Kennesaw, Ga) bileaflet mechanical valves. Both valves are considered highly successful bileaflet mechanical valves characterized by good clinical outcomes despite their numerous design differences. Although thromboembolism remains the main disadvantage of bileaflet mechanical valves, On-X valves have been shown to need less anticoagulation therapy. MethodsHemodynamic assessment of a 23-mm On-X bileaflet mechanical valve and a 23-mm bileaflet SJM valve implanted in an aortic root was performed under pulsatile physiologic conditions. Time-resolved and phase-locked particle-image-velocimetry images and high-speed imaging data were acquired. Pressure gradients, effective orifice areas, dimensionless area index, leaflet position tracking, velocity, and principal Reynolds shear stress were calculated. ResultsPressure gradient for the On-X valve was 4.15 ± 0.099 mm Hg versus 4.75 ± 0.048 mm Hg for SJM (P < .001). Effective orifice area for the On-X valve was 2.61 ± 0.045 cm2 versus 2.36 ± 0.022 cm2 for SJM (P < .001). Area index was higher with SJM (0.87 ± 0.008) than with On-X (0.73 ± 0.013) (P < .001). On-X showed fluctuating leaflet behavior during systole, whereas SJM leaflets were stable. At peak systole, the maximal velocity with On-X was 1.86 m/s versus 2.33 m/s with SJM. Reynolds shear stress was higher with On-X compared with SJM at peak systole (95 vs 72 Pa). Higher velocity fluctuation was noted with the On-X valve. ConclusionsThis study shows that despite the design differences that characterize the On-X valve, the hemodynamic and turbulence parameters were not necessarily improved compared with SJM.

Ten-year experience of tricuspid valve replacement with the St. Jude medical valve

Bioprosthetic valves for tricuspid valve replacement (TVR) have become increasingly popular in recent years, but mechanical valves remain valuable, particularly for the patients who want to avoid reoperation for bioprostheses malfunction. The aim of this study was to review our 10-year experience in adult patients who underwent TVR with the St. Jude Medical (SJM) valve. From 2005 to 2015, 265 TVRs with SJM valves were performed at our institution. The mean age at operation was 44.1 ± 9.7 years, and 207 cases (78.1%) were female. The mean follow-up was 4.9 ± 2.7 years. Preoperative atrial fibrillation was present in 199 cases (75.1%) and ascites in 26 (9.8%). Of all cases, 88.7% were characterized as New York Heart Association class III or IV. The hospital mortality was 6.4%. There were 9 deaths (3.8%) during late follow-up. The overall survival rates were 89.2% ± 2.2% at 5 years and 86.6% ± 2.9% at 10 years. The linearized rates of valve thrombosis and bleeding events were 0.8%/patient-year and 1.5%/patient-year, respectively. Three cases (1.3%) were reoperated due to prosthetic valve thrombosis. There was no reoperation for sperivalvular leakage and structural failure. The freedom from reoperation was 98.6% ± 0.8% at 5 years and 98.6% ± 0.8% at 10 years. The SJM valve in the tricuspid position is a reliable mechanical prosthesis with a low rate of valve thrombosis and reoperation. It is a reasonable choice for the patients who require mechanical valve replacement in the tricuspid position.

PROPOSED OVAL ST. JUDE MEDICAL VALVE: EFFECT OF HEART RATE

In this study, the hemodynamic performance of the conventional St. Jude Medical (SJM) valve and our proposed design known as the oval SJM valve are studied and compared. These studies are based on a wide range of physiological heart rates, i.e., 70–130[Formula: see text]bpm, in the opening phase. We designed and developed a precise computational platform to assess the hemodynamics of bileaflet mechanical heart valves for laminar and turbulent regimes. Also, as one of the fundamental changes applied to the conventional SJM vales, the housing is considered oval similar to oval shape of annulus. Results clearly indicate hemodynamic improvements in the proposed design over the SJM valve. The improvements are characterized by lower shear stress and wall shear stress distributions around the valve and leaflets, and lower valve pressure drop compared to that of the conventional SJM model. The proposed design shows potential and merits additional development.

Mitral valve replacement at Tygerberg Hospital: a 5 year follow-up

This study provides 5-year follow-up data of isolated mitral valve replacements with mechanical prosthesis at a large South African tertiary hospital. It also assessed the significance of pre-operative parameters to predict mortality. This is a retrospective study of 187 patients that underwent isolated mitral valve replacement at Tygerberg Hospital from Jan 1998-Dec 2002. Twenty seven patient’s data was incomplete and they were excluded from the study. All patients had rheumatic mitral valve disease and the valve lesions included mitral incompetence, mitral stenosis and mixed mitral valve disease. All patients had a mechanical prosthesis implanted (St Jude medical or Orbis bileaflet valves). The mean follow-up time was 5.41-years. The 30 day mortality was 5.62% and the 5-year survival was 80%. Pre-operative risk factors that significantly increased mortality were pulmonary hypertension and mitral stenosis. Valve-related complications were more common in this series compared to other First World populations but our results compare well with other Third World population groups. Valve thrombosis 4.32% (0.8%/yr), thromboembolism 8.71% (1.61%/yr), anticoagulant related haemorrhage 6.87% (1.27%/yr), prosthetic valve endocarditis 3.08% (0.57%/yr) and re-operation 8.12% (1.5%/yr). Conclusion: Mechanical valve replacement for mitral valve disease that requires valve replacement is still a good treatment option even in third world population groups. In our series, severe pulmonary hypertension, mitral stenosis and reoperation was statistically significantly more common in the “non-survivors” group.

A novel computational model for the hemodynamics of bileaflet mechanical valves in the opening phase.

A powerful alternative means to study the hemodynamics of bileaflet mechanical heart valves is the computational fluid dynamics method. It is well recognized that computational fluid dynamics allows reliable physiological blood flow simulation and measurements of flow parameters. To date, in almost all of the modeling studies on the hemodynamics of bileaflet mechanical heart valves, a velocity (mass flow)-based boundary condition and an axisymmetric geometry for the aortic root have been assigned, which, to some extent, are erroneous. Also, there have been contradictory reports of the profile of velocity in downstream of leaflets, that is, in some studies, it is suggested that the maximum blood velocity occurs in the lateral orifice, and in some other studies, it is postulated that the maximum velocities in the main and lateral orifices are identical. The reported values for the peak velocities range from 1 to 3 m/s, which highly depend on the model assumptions. The objective of this study is to demonstrate the importance of the exact anatomical model of the aortic root and the realistic boundary conditions in the hemodynamics of the bileaflet mechanical heart valves. The model considered in this study is based on the St Jude Medical valve in a novel modeling platform. Through a more realistic geometrical model for the aortic root and the St Jude Medical valve, we have developed a new set of boundary conditions in order to be used for the assessment of the hemodynamics of aortic bileaflet mechanical heart valves. The results of this study are significant for the design improvement of conventional bileaflet mechanical heart valves and for the design of the next generation of prosthetic valves.

Elliptic st. jude bileaflet mechanical heart valves

Abstract St. Jude Medical (SJM) bileaflet mechanical valves were approved by the Food and Drug Administration in 1977. The SJM valve design consists of two semicircular leaflets which pivot on hinges. Compared to other mechanical heart

Aortic Root Compliance Influences Hemolysis in Mechanical Heart Valve Prostheses: An In-Vitro Study

Mechanical heart valve prostheses are known to activate coagulation and cause hemolysis. Both are particularly dependent on the leaflet dynamics, which in turn depends on the flow field in the aortic root influenced by the aortic root geometry and its compliance. Compliance reduction of large vessels occurs in aging patients, both in those who have atherosclerotic diseases and those who do not. In this study we investigated the correlation between hemolysis and the compliance of the proximal aorta in a novel, pulsatile in vitro blood tester using porcine blood. Two mechanical heart valves, the St Jude Medical (SJM) bileaflet valve and a trileaflet valve prototype (Triflo) were tested for hemolysis under physiological conditions (120/80 mm Hg, 4.5 l/min, 70 bpm) and using two different tester setups: with a stiff aorta and with a compliant aorta. Valve dynamics were subsequently analyzed via high-speed videos. In the tests with the Triflo valve, the free plasma hemoglobin increased by 13.4 mg/dl for the flexible and by 19.3 mg/dl for the stiff setup during the 3-hour test. The FFT spectra and closing speed showed slight differences for both setups. Free plasma hemoglobin for the SJM valve was up by 22.2 mg/dl in the flexible and 42.7 mg/dl in the stiff setup. Cavitation induced by the higher closing speed might be responsible for this, which is also indicated by the sound spectrum elevation above 16 kHz.

Influence of three mechanical bileaflet prosthetic valve designs on the three-dimensional flow field inside a simulated aorta

The current design of the bileaflet valve, the leaflets of which open outside first, differs significantly from the natural valve whose leaflets open center first. This difference generates a completely different flow field in the bileaflet valve compared to that in the natural heart valve. In a previous study, it was demonstrated that the valve design greatly affects the aortic flow field as well as the circulatory flow inside sinuses of Valsalva, using saline solution as a working fluid. A limited discussion on the turbulence flow field that could be generated by the valve was provided. In this continuation of that study, therefore, a dynamic PIV study was conducted to analyze the influence of the heart valve design on the aortic flow field, and particularly on the turbulent profile. This study also aimed to determine the influence of the viscosity of the testing fluid. Three bileaflet prostheses-the St. Jude Medical (SJM), the On-X, and the MIRA valves-were tested under pulsatile flow conditions. Flow through the central orifice of the SJM valve was slower than that through the newer designs. The newer designs tend to show strong flow through all orifices. The On-X valve generates simple jet-type flow while the MIRA valve with circumferentially curved leaflets generates a strong but three-dimensionally diffuse flow, resulting in a more complex flow field downstream of the aortic valve with higher turbulence. A 180° orientation that is more popular clinically seems to provide a less diffuse flow than a 90° orientation. The effect of increasing the viscosity was found to be an increase in the flow velocity through the central orifice and a more organized flow field for all of the valves tested.

Device Thrombogenicity Emulator (DTE) − Design optimization methodology for cardiovascular devices: A study in two bileaflet MHV designs

Patients who receive prosthetic heart valve (PHV) implants require mandatory anticoagulation medication after implantation due to the thrombogenic potential of the valve. Optimization of PHV designs may facilitate reduction of flow-induced thrombogenicity and reduce or eliminate the need for post-implant anticoagulants. We present a methodology entitled Device Thrombogenicty Emulator (DTE) for optimizing the thrombo-resistance performance of PHV by combining numerical and experimental approaches. Two bileaflet mechanical heart valves (MHV) designs, St. Jude Medical (SJM) and ATS, were investigated by studying the effect of distinct flow phases on platelet activation. Transient turbulent and direct numerical simulations (DNS) were conducted, and stress loading histories experienced by the platelets were calculated along flow trajectories. The numerical simulations indicated distinct design dependent differences between the two valves. The stress loading waveforms extracted from the numerical simulations were programmed into a hemodynamic shearing device (HSD), emulating the flow conditions past the valves in distinct ‘hot-spot’ flow regions that are implicated in MHV thrombogenicity. The resultant platelet activity was measured with a modified prothrombinase assay, and was found to be significantly higher in the SJM valve, mostly during the regurgitation phase. The experimental results were in excellent agreement with the calculated platelet activation potential. This establishes the utility of the DTE methodology for serving as a test bed for evaluating design modifications for achieving better thrombogenic performance for such devices.

Assessment of the St. Jude Medical Regent Prosthetic Valve by Continuous-Wave Doppler and Dobutamine Stress Echocardiography

The St. Jude Medical (SJM) Regent prosthetic valve (St. Paul, MN), a recently developed mechanical valve, is an improvement on the conventional SJM valve, having a wider valve area than the SJM HP valve. We evaluated this mechanical valve by Doppler echocardiography and dobutamine stress echocardiography (DSE). The functions of the SJM Regent valve were evaluated by continuous-wave Doppler echocardiography and DES in 58 cases of aortic valve replacement during a stable postoperative period. The peak pressure gradient of the replaced valves sized 17, 19, 21, and 23 mm was 27.5 +/- 11.1, 20.0 +/- 9.8, 15.6 +/- 5.7, and 14.3 +/- 9.1, mm Hg respectively, and the effective orifice area index was 0.97 +/- 0.32, 1.01 +/- 0.29, 1.09 +/- 0.30, and 1.41 +/- 0.54 cm(2)/m(2), respectively, with prosthesis-patient mismatch (PPM) found in 1, 3, 2, and 0 cases for the 17-, 19-, 21- and 23-mm valves, respectively, with a total incidence of 10.3%. In 20 cases, the peak pressure gradient and the effective orifice area index were significantly increased during DSE compared with those at rest. Although the PPM incidence was 6.6%, it was deemed from the data of DSE and clinical symptoms that there were no clinical issues for such cases of PPM in the early and intermediate phases after operation. Particularly, the effectiveness of the 17- and 19-mm valves in patients with a small aortic annulus was demonstrated, confirming the satisfactory functions of the SJM Regent prosthetic valve.

Dynamic particle image velocimetry study of the aortic flow field of contemporary mechanical bileaflet prostheses

The characteristics of mechanical bileaflet valves, the leaflets of which open at the outside first, differ significantly from those of natural valves, whose leaflets open at the center first, and this fact affects the flow field down-stream of the valves. The direction of jet-type flows, which is influenced by this difference in valve features, and the existence of the sinus of Valsalva both affect the flow field inside the aorta in different ways, depending on the valve design. There may also be an influence on the coronary circulation, the entrance to which resides inside the sinus of Valsalva. A dynamic particle image velocimetry (PIV) study was conducted to analyze the influence of the design of prosthetic heart valves on the aortic flow field. Three contemporary bileaflet prostheses, the St. Jude Medical (SJM) valve, the On-X valve (with straight leaflets), and the MIRA valve (with curved leaflets), were tested inside a simulated aorta under pulsatile flow conditions. A dynamic PIV system was employed to analyze the aortic flow field resulting from the different valve designs. The two newer valves, the On-X and the MIRA valves, open more quickly than the SJM valve and provide a wider opening area when the valve is fully open. The SJM valve's outer orifices deflect the flow during the accelerating flow phase, whereas the newer designs deflect the flow less. The flow through the central orifice of the SJM valve has a lower velocity compared to the newer designs; the newer designs tend to have a strong flow through all orifices. The On-X valve generates a simple jet-type flow, whereas the MIRA valve (with circumferentially curved leaflets) generates a strong but three-dimensionally diffuse flow, resulting in a more complex flow field downstream of the aortic valve. The clinically more adapted 180 degrees orientation seems to provide a less diffuse flow than the 90 degrees orientation does. The small differences in leaflet design in the bileaflet valves generate noticeable differences in the aortic flow; the newer valves show strong flows through all orifices.

Biofilm formation on pyrolytic carbon heart valves: Influence of surface free energy, roughness, and bacterial species

The aim of this study was to analyze the interaction of surface free energy and roughness characteristics of different pyrolytic carbon heart valves with three bacterial species on biofilm formation. Three pyrolytic carbon heart valves (St Jude Medical [St Jude Medical Inc, Minneapolis, Minn], Sulzer Carbomedics [CarboMedics Inc, Austin, Tex], and MedicalCV [Medical Incorporated, Inver Grove Heights, Minn]) were tested. Roughness was measured by interferential microscopy and surface free energy by contact angle technique. To obtain a biofilm, prostheses were inserted into a bioreactor with Staphylococcus aureus P209, Staphylococcus epidermidis RP62A, or Pseudomonas aeruginosa PAO1. Adhesion was quantified by counting sessile bacteria. Morphologic characteristics of biofilms were evaluated with scanning electron microscopy. Roughness analysis revealed significant differences between the MedicalCV (35.18 +/- 4.43 nm) valve and St Jude Medical (11.03 +/- 3.11 nm; P < .0001) and Sulzer Carbomedics (8.80 +/- 1.10 nm; P < .0001) valves. Analysis of surface free energy revealed a higher level for the MedicalCV valve (41.03 mJ x m(-2)) than for both the Sulzer Carbomedics (38.93 mJ x m(-2)) and St Jude Medical (31.51 mJ . m(-2)) models. These results showed a correlation between surface free energy and bacterial adhesion for S epidermidis and P aeruginosa species. Regardless of the support, we observed significant adhesion differences for the three bacterial species. S aureus was the most adherent species, S epidermidis was the least, and P aeruginosa was intermediate. Our results suggest that adhesion of S epidermidis and P aeruginosa are dependent on pyrolytic carbon surface free energy and roughness, although S aureus adhesion appears to be independent of these factors. Improvement of pyrolytic carbon physicochemical properties thus could lead to a reduction in valvular prosthetic infections.

A SWINE MODEL FOR LONG‐TERM EVALUATION OF PROSTHETIC HEART VALVES

The objective of this study was to develop a porcine model of mitral valve replacement (MVR) for long-term evaluation of prosthetic heart valves. Sixteen 25-kg male Bama miniature pigs underwent MVR using St Jude Medical valve (21 mm). Each animal was allocated to an anticoagulation protocol after surgery (group I, s.c. heparin injection and warfarin (n = 8); group II, s.c. low-molecular-weight heparin and warfarin (n = 8)) and was followed for up to 20 weeks. Terminal studies were carried out on all animals having survived for more than 140 days or died. Fourteen animals survived for more than 1 month without signs of heart failure. One of group I animals died from haemorrhagic (haemopericardium) complications on the 9th postoperative day, and another animal of group I died on the 18th postoperative day because of valve thrombosis. Compared with other species, humans and pigs show remarkable anatomical and physiological similarities. This model is promising for long-term preclinical evaluation of prosthetic heart valves and evaluation of postoperative anticoagulant agents.

Thrombosed mechanical pulmonary valve successfully treated with thrombolysis

Prosthetic heart valve thrombosis is a serious complication with a high mortality. We report the case of a thrombosed St Jude Medical valve placed in the pulmonary position, in a patient who had undergone repair of tetralogy of Fallot, which was successfully treated with intravenous thrombolytic therapy with streptokinase.

Dynamic particle image velocimetry flow analysis of the flow field immediately downstream of bileaflet mechanical mitral prostheses

New dynamic particle image velocimetry (PIV) technology was applied to the study of the flow field associated with prosthetic heart valves. Four bileaflet prostheses, the St. Jude Medical (SJM) valve, the On-X valve with straight leaflets, the Jyros (JR) valve, and the Edwards MIRA (MIRA) valve with curved leaflets, were tested in the mitral position under pulsatile flow conditions to find the effect of the leaflet shape and overall valve design on the flow field, particularly in terms of the turbulent stress distribution, which may influence hemolysis, platelet activation, and thrombus formation. Comparison of the time-resolved flow fields associated with the opening, accelerating, peak, and closing phases of the diastolic flow revealed the effects of the leaflet shape and overall valve design on the flow field. Anatomically and antianatomically oriented bileaflet valves were also compared in the mitral position to study the effects of the orientation on the downstream flow field. The experimental program used a dynamic PIV system utilizing a high-speed, high-resolution video camera to map the true time-resolved velocity field inside the simulated ventricle. Based on the experimental data, the following general conclusions can be made. High-resolution dynamic PIV can capture true chronological changes in the velocity and turbulence fields. In the vertical measuring plane that passes the centers of both the aortic and mitral valves (A-A section), bileaflet valves show clear and simple circulatory flow patterns when the valve is installed in the antianatomical orientation. The SJM, the On-X, and the MIRA valves maintain a relatively high velocity through the central orifice. The curved leaflets of the JR valve generate higher velocities with a divergent flow during the accelerating and peak flow phases when the valve is installed in the anatomical orientation. In the velocity field directly below the mitral valve and normal to the previous measuring plane (B-B section), where characteristic differences in valve design on the three-dimensional flow should be visible, the symmetrical divergent nature of the flow generated by the two inclined half-disks installed in the antianatomical orientation was evident. The SJM valve, with a central downward flow near the valve, is contrasted with the JR valve, which has a peripherally strong downward circulation with higher turbulent stresses. The On-X valve has a strong central downward flow attributable to its large opening angle and flared inlet shape. The MIRA valve also has a relatively strong downward central flow. The MIRA valve, however, diverts the flow three-dimensionally due to its peripherally curved leaflets.

Prevalence and Avoidance of Patient-Prosthesis Mismatch in Aortic Valve Replacement in Small Adults

It is still controversial as to whether a small prosthesis should be inserted or a small aortic annulus should be enlarged to minimize patient-prosthesis mismatch (PPM). This retrospective study reviewed our strategy for avoiding PPM. Isolated or combined aortic valve replacement was performed in 181 patients, including 24 patients (13.3%) aged less than 65 years with a small aortic annulus (< or = 21 mm) who underwent enlargement of the annulus by the Manouguian (n = 18) or Nicks (n = 6) procedure. In patients aged 65 years or more, a Carpentier-Edwards Perimount pericardial (CEP) valve was implanted with few exceptions. We assessed our strategy for avoiding PPM by comparison with published normal reference values for the indexed effective orifice area. A CEP valve was implanted in 53 patients, and St. Jude Medical (SJM) mechanical valves were used in 128 patients. A standard 21-mm SJM valve was only used in 4 patients and no 19-mm valves were employed. However, 19-mm CEP valves were used in 12 older patients with a small body surface area (1.43 +/- 0.14 m2). No patient receiving an SJM valve had an indexed effective orifice area of 0.85 cm2/m2 or less, and PPM developed in only 2 (3.8%) of 53 patients receiving CEP valves. Consequently, the prevalence of PPM was 1.1%. The 10-year survival rates of patients receiving CEP or SJM valves with or without annular enlargement were similar. The prevalence of PPM was low in patients more than 65 years old with a relatively small body size who received bioprosthetic valves. In patients less than 65 years old with a small annulus, the method of first choice for avoiding PPM is aortic annular enlargement.

Effect of the flow field of mechanical bileaflet mitral prostheses on valve closing

Antianatomically installed Jyros (JR) and ATS valves were compared with the St. Jude Medical (SJM) valve in the mitral position to study the effects of valve design on the downstream flow field and associated closing sounds using a particle image velocimetry (PIV) method utilizing a high-speed video flow visualization technique to map the velocity field and sound measurement to confirm claims by the manufacturer. Based on the experimental data, the following general conclusions can be made: in the velocity field directly below the mitral valve, where distinct characteristic differences in valve design can be seen, symmetrical twin circulations were observed because of the divergent nature of the flow generated by the two inclined half-disks installed in the antianatomical orientation; the SJM valve, which produced central downward circulation, is contrasted to the two other valves, which produced peripheral downward circulation. These differences may play an important role in the closing behavior of the valve leaflets, thus affecting the generation of the valve closing sound.