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PubMed1998

Thromboembolism and mechanical heart valves: a randomized study revisited.

BACKGROUND: This study was designed to revise and substantiate previous inferences, based on short-term follow-up, about differences in the incidence of anticoagulant-related events after heart valve replacement among patients who had been randomly assigned to receive either a Björk-Shiley, Edwards-Duromedics, or Medtronic-Hall mechanical heart valve prosthesis. METHODS: Intermediate-term follow-up to January 1995 was completed in 418 of 419 patients randomized to receive one of three types of heart valve prostheses between January 1982 and January 1987. Median follow-up was 98.5 months. Multivariable analysis in the hazard function domain was performed to identify factors that influenced the incidence of time-related thromboembolism and bleeding. These findings were compared with those made previously after a median follow-up of 37.5 months. RESULTS: No differences were found among the three prostheses in rates of anticoagulant-related hemorrhage. However, the incidence of thromboembolism was higher after mitral valve replacement among patients who had received the Medtronic-Hall prosthesis (linearized rate, 5.4% per patient year; 70% confidence interval, 4.0% to 7.1%), compared with Edwards-Duromedics (1.3%; 70% confidence interval, 0.4% to 3.0%) and Björk-Shiley prostheses (1.2%; 70% confidence interval, 0.6% to 2.2%). CONCLUSIONS: At long-term follow-up, in contrast to the findings at short-term follow-up, patients with either Björk-Shiley or Edwards-Duromedics prostheses had low rates of thromboembolism, whereas higher rates occurred in patients with a Medtronic-Hall prosthesis in the mitral position.

Anticoagulants↗

PubMed1998

The development of the Starr-Edwards heart valve.

Development of the Starr-Edwards heart valve marked a new era in the treatment of valvular heart disease. Until the development of the Starr-Edwards valve, there were no published reports of patients who had lived longer than 3 months with a prosthetic valve in the mitral position. This valve was the result of a unique partnership between a young surgeon, Dr. Albert Starr, and an experienced engineer, Mr. Lowell Edwards. Working as a team, these 2 men developed and successfully implanted the 1st Starr-Edwards valve within less than 2 years of their 1st meeting. Their key to success was their willingness and ability to make repeated modifications to their design to solve each clinical problem as it arose. Their constant focus on the clinical goal aided the rapid transformation of their design from a leaflet valve to a shielded ball valve, and finally to an unshielded ball valve suitable for implantation in a human being. Along the way, they abandoned the idea of imitating the appearance of native valves, in favor of developing valves that would be clinically successful. Their work has provided help and hope for patients who otherwise would have died from the complications of rheumatic heart disease and other valvular disorders for which valve replacement is the only treatment.

Biomedical Engineering↗

PubMed2003

Inhibition of cusp and aortic wall calcification in ethanol- and aluminum-treated bioprosthetic heart valves in sheep: background, mechanisms, and synergism.

BACKGROUND AND AIM OF THE STUDY: Calcification of bioprosthetic heart valves fabricated from glutaraldehyde (GA)-pretreated heterograft tissue is frequently responsible for the clinical failure of these devices. Stentless bioprostheses fabricated from GA-fixed porcine aortic valves pose an important challenge in this regard, as pathologic calcification can affect not only the bioprosthetic cusps, but also the aortic wall segment. METHODS: A synergistic approach was used to prevent bioprosthetic cusp and aortic wall calcification. Ethanol pretreatment of bioprosthetic heart valves was shown to inhibit cuspal calcification due to multiple mechanisms, including alterations of collagen structure and lipid extraction. AlCl3 pretreatment of bioprostheses to prevent calcification was also investigated; this alters elastin structure, inhibits alkaline phosphatase, and complexes with phosphoesters, thereby inhibiting aortic wall mineralization. RESULTS: Experimental data from rat subdermal implants and sheep mitral replacements showed successful synergism with co-pretreatment of porcine aortic valve bioprostheses with ethanol and AlCl3. Significant inhibition of both cusp and aortic wall calcification was achieved by differential pretreatments that restrict AlCl3 to only the aortic wall, and not the cusp, accompanied by ethanol cuspal exposure. Sequential exposure of bioprostheses, first to AlCl3 and then to ethanol, led to unexpectedly severe cuspal calcification. CONCLUSION: Differential pretreatment of stentless bioprostheses with ethanol and AlCl3 can effectively inhibit both cuspal and aortic wall calcification.

Aluminum↗

PubMed1996

Hemodynamic assessment of carbomedics bileaflet heart valves by ultrasound: studies in the aortic and mitral positions.

The bileaflet mechanical heart valve has become a popular prosthesis for implantation in both the aortic and mitral positions and a recent design by Carbomedics has received widespread use. Noninvasive assessment of these valves by Doppler ultrasound is important in characterizing their normal performance and in assessing the course of dysfunction. This study addressed the hypothesis that Doppler predicted pressure drops will correlate with catheter pressure drops within a valve size and position. A subhypothesis is that the pressure drops agree, and we expect this subhypothesis to fail due to pressure recovery effects. In a well-controlled in vitro model it was shown that the combined effects of pressure recovery and neglecting proximal velocities resulted in overestimation of catheter pressure drops for Carbomedics bileaflet valves. Inclusion of the proximal velocity reduced overestimation of peak pressure drops for aortic and mitral valves to clinically acceptable levels, and removed overestimation of mean pressure drops. Without correction for proximal velocity, overestimation of mitral pressure drops was reduced to 3.32% when means were calculated, but mean aortic pressure drops still overestimated the catheter standard significantly. It is concluded that proximal velocities should be included in Bernoulli analysis of Carbomedics heart valves. If the proximal velocity is not available, mitral valves may be best assessed using mean pressure drops, while aortic valve Doppler data, peak or mean, should be interpreted with caution.

Aortic Valve↗

PubMed1978

Long term clinical and haemodynamic evaluation of the Ionescu-Shiley pericardial xenograft heart valve.

The experience with the Ionescu-Shiley pericardial xenograft used for heart valve replacement over a period of 7 years has demonstrated, in both the aortic and atrioventricular position, excellent long term clinical and haemodynamic results. There were very few valve related complications and none occurred with valves manufactured since May 1976 by Shiley Laboratories. The long term durability of the glutaraldehyde stabilised pericardial xenografts was demonstrated by a rigorous and complete clinical follow-up as well as by histological and haemodynamic investigations. Valve thrombosis or calcification have not been encountered in this series. The embolic rate has been very low in both the aortic and mitral positions in the absence of long term anticoagulant treatment. The superior haemodynamic performance of this valve, even in very small sizes, represents an additional advantage and makes it particularly suitable for use in patients with narrow aortic root and in children. The very good results obtained with the pericardial xenograft fully justify its continued clinical use in the aortic, mitral and tricuspid positions.

Animals↗

PubMed2005

Culture results of heart valves resected because of streptococcal endocarditis: insights into duration of treatment to achieve valve sterilization.

OBJECTIVES: To analyse the culture results of heart valves removed following streptococcal endocarditis in order to gain insight into the duration of treatment required for valve sterilization. PATIENTS AND METHODS: Retrospective review of 131 episodes of streptococcal endocarditis: 94 due to alpha-haemolytic streptococci; 15 due to beta-haemolytic streptococci; 10 due to nutritionally deficient streptococci; eight due to the Streptococcus anginosus group and four due to Streptococcus pneumoniae. Patients had their valves removed during antimicrobial treatment. Culture results were analysed with respect to duration of treatment before surgery. RESULTS: For alpha-haemolytic streptococci, 17 (18%) valves were culture-positive and 77 (82%) culture-negative after a median (range) of 4 (1-20) and 16 (4-58) days of treatment, respectively, P < 0.001. For beta-haemolytic streptococci, two valves (13%) were culture-positive; both patients had received < or = 4 days of treatment. Four patients (40%) with nutritionally deficient streptococci were culture-positive, and had received < or = 8 days of treatment. For the S. anginosus group, two valves (25%) were culture-positive; both patients had received < or = 4 days of treatment before operation. Overall, only one of 131 (0.8%) valves was culture-positive after 14 days of treatment. All valves infected with beta-haemolytic streptococci, nutritionally deficient streptococci and the S. anginosus group, who were treated for more than 8 days before surgery, were culture-negative. CONCLUSIONS: Our findings support current treatment guidelines for endocarditis caused by alpha-haemolytic streptococci. We suggest that the recommended duration of treatment for endocarditis resulting from other streptococci may be excessive and treatment trials evaluating 2 and 4 week regimens are justified.

Adult↗

PubMed1995

Magnetic resonance velocity imaging: a new method for prosthetic heart valve study.

The aim of this study was to compare different (long/short echo time, whole body/small bore scanner) magnetic resonance velocity measurement techniques and their applicability to the measurement of blood velocity downstream of prosthetic heart valves. In-vitro magnetic resonance velocity measurements were performed downstream of four normal and stenotic prosthetic heart valves (St. Jude Medical bileaflet, Monostrut tilting disc, Ionescu-Shiley Pericardial and Starr-Edwards caged-ball) under steady flow conditions in an aortic test chamber. Cross-sectional and longitudinal velocity images were obtained downstreamed of the valves. Magnetic resonance was able to measure all three components of fluid velocity downstream of the valves under normal and stenotic conditions except in regions of turbulence. The velocity was measured across the tube cross-section in 10-15 minutes producing a good visualization of the axial velocity profile. High velocity regions, shear layers and reversed/stagnant regions were identified. The flow rate calculated by integration of the magnetic resonance velocity across the cross-section of the tube was accurate to 5-6% in normal cases and slightly less accurate for stenotic valves. Although signal loss on the modulus image was adverse to the velocity images, it was found that these regions could be used to identify areas of flow disturbance. The high magnetic field, small bore scanner was able to produce images with a resolution of 0.2 x 0.2 x 1.0 mm and was less affected by turbulence producing more detailed flow images. Magnetic resonances has been shown to be a useful new tool in the measurement of the velocity downstream of prosthetic heart valves. In particular it's short data acquisition time and the possibilities to reproduce the same measurements in-vivo make it an attractive alternative to traditional methods.

Biophysical Phenomena↗

PubMed2001

Long-term results with St. Jude Medical and CarboMedics prosthetic heart valves.

BACKGROUND AND AIM OF THE STUDY: The clinical evaluation and comparison of St. Jude Medical (SJM) and CarboMedics (CM) prosthetic heart valves implanted between 1988 and 1997 is presented. METHODS: In total, 648 SJM valves were implanted in 641 patients, and 601 CM valves in 591 patients. There were 684 mitral valve replacements, 256 aortic valve replacements, 252 mitral and aortic (double) valve replacements, 16 triple valve replacements, and 41 other tricuspid-related valve replacements. Total follow up was 98%. The overall incidence of valve-related events was compared before and after establishment of a 'valve clinic' in 1993. RESULTS: The overall hospital mortality was 3.4%; late mortality was 8.2%. The five- and ten-year survival for all patients was 92.1% and 86.2%, respectively. There were 31 episodes of thromboembolism in 27 patients (including valve thrombosis in three), 21 episodes of bleeding events in 20 patients, and 18 re-replacements of implanted valves. No structural valve deterioration was observed. Freedom from thromboembolism was 97.8% at five years and 96.3% at ten years; freedom from bleeding episodes was 98.1% and 97.6%, respectively. In terms of hospital and late mortality, and incidence of thromboembolism, hemorrhagic episodes and structural valve failure, no statistically significant differences were found between the SJM and CarboMedics patient groups. Freedom from thromboembolism was 96.7% at five years before initiation of an intensive follow up program, and 99.0% thereafter (p = 0.031). In contrast, freedom from bleeding episodes fell from 99.3% to 96.1% during the same time period (p = 0.0004). CONCLUSION: Both the SJM and CM prosthetic heart valves performed well in our study, and no discernible differences in clinical performance of the two valves were detected. The intensive follow up program resulted in a reduced incidence of thromboembolism, but an increased number of bleeding complications. An optimum anticoagulation regimen to manage these two conflicting problems has yet to be elucidated.

Adolescent↗

PubMed1997

Time-frequency analysis of the first heart sound: Part 3: Application to dogs with varying cardiac contractility and to patients with mitral mechanical prosthetic heart valves.

The cone-kernel distribution (CKD) is first applied to the analysis of the intracardiac and the thoracic first heart sound (S1) of dogs in various cardiac contractile states, and secondly to the S1 of patients with mitral mechanical prosthetic heart valves. The CKD of native S1 in dogs shows that the dominant components of S1 are generally concentrated in a band at around 50 Hz with a horizontal flat or a semi-lunar shape, independently of the myocardial contractile state. There is no significant systematic rising frequency component. The instantaneous frequency of S1 shows a good cross-correlation with the time derivative of the left ventricular pressure (dP/dt), but the maximum frequency is not proportional to the maximum of dP/dt. The CKD of S1 in patients with mitral mechanical prosthetic heart valves showed a pulse-like component with a high-frequency bandwidth, which is distinct from the low constant-frequency components of S1 produced by native heart valves.

Animals↗

PubMed1995

[Differentiated evaluation of heart valve stenosis by expanded Bernoulli equation--in vitro studies of model stenoses].

A suitable measure for the hydrodynamic assessment of heart valve stenoses must be independent of flow and should correspond to the morphology of the stenoses. The "effective orifice area" according to Gorlin does not fulfil this requirement, generally, because it is constant only under special conditions. This suggests the development of a multidimensional stenosis model. The idea for doing so is based on hydrodynamic evaluation of different elementary stenosis types in comparison with a valve that behaves like Gorlin's theory. The Bernoulli equation can than be expanded definitely and one gets a set of unknown stenosis parameters corresponding to the elementary stenoses. The clinical relevance of these must be evaluated by morphological evidence and by similarity of the flow-pressure drop characteristics as compared to real heart valve stenoses. A suitable reference valve is the Björk-Shiley valve. This valve was combined with evident elastic and stiff obstacles to opening with the result of flow-pressure drop characteristics similar to biological valves written in terms of flow q: [formula: see text] where q and q2 are mean flow and mean square flow through the valve, respectively. Empirical results reported in the literature can be explained as special cases of the stenosis model as demonstrated by examples. The proposed equation can be interpreted in physically founded terms in contrast with an empirical one. It gives rise to a differentiated evaluation of heart valve stenosis by orifice area (c2), elastic properties of shape and material (c1) and pre-stress (c0) independent on flow. The model can be extended step by step as required.

Aortic Valve↗

PubMed2005

Validation and refinement of mortality risk models for heart valve surgery.

BACKGROUND: The Northern New England Cardiovascular Disease Study Group (NNE) recently published risk models for hospital mortality after heart valve surgery. The Providence Health System Cardiovascular Study Group (PHS) has been collecting similar heart valve data for 8 years, providing an ideal opportunity to both validate the NNE risk models and attempt to produce an improved model, by using some different modeling techniques. METHODS: From 1997 to 2004, 3,324 patients aged 30 to 95 years underwent aortic valve replacement (AVR), and 1,596 underwent mitral valve replacement or repair (MVRR) at one of nine PHS medical centers. We used area under the receiver operating characteristic curve (c-index) to measure model discrimination, and Hosmer-Lemeshow statistic (H-L) to measure calibration. We modified the NNE models by ungrouping continuous variables, seeking optimal transformations of continuous variables, and imputing missing values by multiple regression. RESULTS: The prevalence and the lethality of risk factors were similar in PHS and NNE patients. The NNE models fit PHS patients well: c-index (95% confidence interval) = 0.75 (0.70 to 0.80) for AVR and 0.81 (0.76 to 0.86) for MVRR; H-L = 3.95 (p = 0.861) for AVR and 7.10 (p = 0.526) for MVRR. A single PHS model performed slightly better for both positions: c-index = 0.79 (0.75 to 0.83) for AVR and 0.84 (0.80 to 0.88) for MVRR; H-L = 2.75 (p = 0.949) for AVR and 12.21 (p = 0.142) for MVRR. CONCLUSIONS: The NNE models for aortic and mitral valve surgery were successfully validated using PHS patients. Using some different statistical approaches to modeling, we produced a new, unified model for both positions.

Adult↗

PubMed2006

Cyclic flexure and laminar flow synergistically accelerate mesenchymal stem cell-mediated engineered tissue formation: Implications for engineered heart valve tissues.

Bone marrow-derived mesenchymal stem cells (BMSCs) are relatively accessible and exhibit a pluripotency suitable for cardiovascular applications such as tissue-engineered heart valves (TEHVs). Recently, Sutherland et al. [From stem cells to viable autologous semilunar heart valve. Circulation 2005; 111(21): 2783-91] demonstrated that BMSC-seeded TEHV can successfully function as pulmonary valve substitutes in juvenile sheep for at least 8 months. Toward determining appropriate mechanical stimuli for use in BMSC-seeded TEHV cultivation, we investigated the independent and coupled effects of two mechanical stimuli physiologically relevant to heart valves-cyclic flexure and laminar flow (i.e. fluid shear stress)-on BMSC-mediated tissue formation. BMSC isolated from juvenile sheep were expanded and seeded onto rectangular strips of nonwoven 50:50 blend poly(glycolic acid) (PGA) and poly(l-lactic acid) (PLLA) scaffolds. Following 4 days static culture, BMSC-seeded scaffolds were loaded into a novel flex-stretch-flow (FSF) bioreactor and incubated under static (n=12), cyclic flexure (n=12), laminar flow (avg. wall shear stress=1.1505 dyne/cm(2); n=12) and combined flex-flow (n=12) conditions for 1 (n=6) and 3 (n=6) weeks. By 3 weeks, the flex-flow group exhibited dramatically accelerated tissue formation compared with all other groups, including a 75% higher collagen content of 844+/-278 microg/g wet weight (p<0.05), and an effective stiffness (E) value of 948+/-233 kPa. Importantly, collagen and E values were not significantly different from values measured for vascular smooth muscle cell (SMC) -seeded scaffolds incubated under conditions of flexure alone [Engelmayr et al. The independent role of cyclic flexure in the early in vitro development of an engineered heart valve tissue. Biomaterials 2005; 26(2): 175-87], suggesting that BMSC-seeded TEHV can be optimized to yield results comparable to SMC-seeded TEHV. We thus demonstrated that cyclic flexure and laminar flow can synergistically accelerate BMSC-mediated tissue formation, providing a basis for the rational design of in vitro conditioning regimens for BMSC-seeded TEHV.

Animals↗

PubMed2005

[The frequency of risk factors of thromboembolic and hemorrhagic complications in patients treated with oral anticoagulants after heart valve replacement].

UNLABELLED: Thromboembolic (TE) and hemorrhagic (H) complications are the most significant problems in patients treated with oral anticoagulants (OA) after implantation of artificial valvular prostheses of heart. This problem was discussed in worlds scientific literature, but was not comprehensive investigated in Polish population of patients. The aim of the study was to assess the frequency of TE and H complications and their influence on mortality and morbidity and to determine the risk factors related to clinical and hemodynamical patients status. MATERIAL AND METHODS: Between December 1997 and December 1998, 358 patients hospitalized in our Department were qualified for cardiac surgery. There were 177 women and 181 men with a mean age 56.9+/-10.3 (range 21-80 years), who underwent 144 mitral, 172 aortic, 42 both artificial heart valve replacement. All patients were followed prospectively. RESULTS: Follow up was 100% complete and averaged 36.7+/-12.1 months. The total follow-up was 1109.8 pty. Linearized incidents of death was 2.1%/pty (30 patients). TE events were in 30 patients (2.7%/pty). H events occurred in 46 patients (4.15%/pty). The TE and H complications were the most important causes of morbidity and mortality in observed population of patients after mechanical heart valve replacement. Frequency of complications was inside the broad spectrum of values presented in the literature. CONCLUSIONS: The independent risk factors of death were: lower EF (RR: 1.06; CI 95%: 1.02-1.08), advanced functional NYHA class in presurgery period (RR: 3.5; CI 95%: 1.1-8.2) and advanced functional NYHA class in postsurgery period (RR: 7.5; CI 95%: 3.6-15.5). The independent risk factor of TE as well H complications was an advanced functional NYHA class in perioperative period (respectively for TE and H complications RR: 4.2; CI 95%: 1.9-8.9 and RR: 3.2; CI 95%: 1.5-6.7). In the group with artificial heart valve in reference to the severe (class III) complications of postoperative period-independent risk factors were atherosclerosis risk factors (hypertension, hypercholesterolemia, diabetes and smoking) (RR: 2.4; CI 95%: 1.3-5.6).

Adult↗

PubMed2001

A nonlinear anisotropic model for porcine aortic heart valves.

The anisotropic property of porcine aortic valve leaflet has potentially significant effects on its mechanical behaviour and the failure mechanisms. However, due to its complex nature, testing and modelling the anisotropic porcine aortic valves remains a continuing challenge to date. This study has developed a nonlinear anisotropic finite element model for porcine heart valves. The model is based on the uniaxial experimental data of porcine aortic heart valve leaflet and the properties of nonlinear composite material. A finite element code is developed to solve this problem using the 8-node super-parameter nonlinear shells and the update Lagrangian method. The stress distribution and deformation of the porcine aortic valves with either uniform and non-uniform thicknesses in closed phase and loaded condition are calculated. The results showed significant changes in the stress distributions due to the anisotropic property of the leaflets. Compared with the isotropic valve at the same loading condition, it is found that the site of the peak stress of the anisotropic leaflet is different; the maximum longitudinal normal stress is increased, but the maximum transversal normal stress and in-plane shear stress are reduced. We conclude that it is very important to consider the anisotropic property of the porcine heart valves in order to understand the failure mechanism of such valves in vivo.

Animals↗

PubMed1993

A comparison of aspirin with placebo in patients treated with warfarin after heart-valve replacement.

BACKGROUND: Despite the use of warfarin, major systemic embolism remains an important complication in patients with heart-valve replacement. Although the addition of antiplatelet agents has the potential to reduce this complication, their efficacy and safety when given in combination with warfarin are uncertain. METHODS: In a randomized, double-blind, placebo-controlled trial, we assessed the efficacy and safety of adding aspirin (100 mg per day) to warfarin treatment (target international normalized ratio, 3.0 to 4.5) in 370 patients with mechanical heart valves or with tissue valves plus atrial fibrillation or a history of thromboembolism. RESULTS: A total of 186 patients were randomly assigned to aspirin and 184 to placebo, and they were followed for up to 4 years (average, 2.5). Major systemic embolism or death from vascular causes occurred in 6 aspirin-treated patients (1.9 percent per year) and 24 placebo-treated patients (8.5 percent per year) (risk reduction with aspirin, 77 percent; 95 percent confidence interval, 44 to 91 percent; P < 0.001). Major systemic embolism, nonfatal intracranial hemorrhage, or death from hemorrhage or vascular causes occurred in 12 patients assigned to aspirin (3.9 percent per year) and 28 patients assigned to placebo (9.9 percent per year) (risk reduction, 61 per cent; 95 percent confidence interval, 24 to 80 percent; P = 0.005); major systemic embolism or death from any cause occurred in 13 patients (4.2 percent) and 33 patients (11.7 percent), respectively (risk reduction, 65 percent; 95 percent confidence interval, 33 to 82 percent; P < 0.001); and death from all causes occurred in 9 patients (2.8 percent) and 22 patients (7.4 percent), respectively (risk reduction, 63 percent; 95 percent confidence interval, 19 to 83 percent; P = 0.01). Bleeding occurred in 71 patients in the aspirin group (35.0 percent), as compared with 49 patients in the placebo group (22.0 percent) (increase in risk, 55 percent; 95 percent confidence interval, 8 to 124 percent; P = 0.02); major bleeding occurred in 24 and 19 patients, respectively (increase in risk, 27 percent; 95 percent confidence interval, -30 to 132 percent; P = 0.43). CONCLUSIONS: In patients with mechanical heart valves and high-risk patients with prosthetic tissue valves, the addition of aspirin to warfarin therapy reduced mortality, particularly mortality from vascular causes, together with major systemic embolism. Although there was some increase in bleeding, the risk of the combined treatment was more than offset by the considerable benefit.

Adult↗

PubMedDate not supplied

Hemodynamic comparisons of polyurethane trileaflet and bioprosthetic heart valves.

Hemodynamic comparison of two polyurethane prosthetic heart valves with a bioprosthetic valve is presented. The valves were incorporated in a pulse duplicator simulating physiologic pulsatile flow, and comparisons between the valves were made on the transvalvular pressure drop, percent regurgitation, valve orifice area, rate of opening and closing as well as the performance index. The results showed that the functional characteristics of the polyurethane valve compared favorably with that of the bioprosthetic valve. The polyurethane valve can be a viable and inexpensive alternative, especially for short-term use in a total artificial heart as a bridge to transplant.

Bioprosthesis↗

PubMed2000

Surface pitting of heart valve disks tested in an accelerated fatigue tester.

There are various reports on the fracture of mechanical heart valves implanted in humans or animals and it has been pointed out that fractures are induced by erosion of the disk surface due to cavitation bubbles. Cavitation erosion on mechanical heart valves was studied using our originally designed accelerated fatigue tester. Several valve housings with different compliance values were used. The number and position of pits on the valve disk were measured using an optical microscope. Disk-closing velocity was measured and cavitation bubbles were monitored by a high-speed video camera. It was found that disk-closing velocity increased and cavitation erosion was enhanced with an increase in compliance of the valve holder. Therefore, careful attention should be paid to the compliance of an accelerated fatigue tester.

Animals↗

PubMed1982

[Non-invasive determination of pressure gradients of heart valve prostheses using Doppler ultrasound].

Noninvasive measurements of pressure gradients by continuous wave Doppler ultrasound technique were carried out in 40 patients with correctly functioning heart valve prostheses (10 Björk-Shiley in aortic position, 10 Björk-Shiley in mitral, 10 St. Jude Medical in aortic and 10 St. Jude Medical in mitral) and in 10 patients with normal aortic and 10 patients with normal mitral valves. The pressure gradients were slightly but significantly higher in prosthetic than in normal heart valves (p less than 0.005). Pressure gradients in Björk-Shiley prostheses were higher than in St. Jude Medical prostheses both in aortic (18.4 +/- 2.6 vs 9.6 +/- 1.9; p less than 0.01) and in mitral position (8.2 +/- 1.1 vs 5.4 +/- 0.8; p less than 0.05). The pressure gradient was inversely related to valve size in Björk-Shiley prostheses (r = -0.60 for aortic and r = -0.42 for mitral valves; p less than 0.05) but not in St. Jude Medical prostheses. The non-invasive Doppler technique should be useful in the diagnosis of prosthetic valve obstruction.

Aortic Valve↗