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PubMed1989

[Long-term follow-up of prosthetic heart valves].

257 patients underwent single or double heart valve replacement between 1964-1986. In 141 (55%) after isolated mitral valve replacement, operative mortality was 14.8% and after 5, 10, 15 and 20 years, actuarial survival was 84%, 70%, 59% and 44%, respectively. In 70 who underwent isolated aortic valve replacement, operative mortality was 7.1% and after 5, 10, 15 and 20 years, actuarial survival was 85%, 85%, 72% and 72%. In 46 who underwent combined aortic and mitral replacement, operative mortality was 4.3% and after 5, 10 and 15 years, actuarial survival was 78%, 71% and 71%.

Actuarial Analysis↗

PubMed1999

Videoassisted thrombectomy of mechanical prosthetic heart valves.

BACKGROUND AND AIM OF THE STUDY: Thrombosis of a bileaflet mechanical heart valve is a life-threatening clinical event. Surgical thrombectomy of bileaflet mechanical prostheses remains an appropriate treatment in selected patients. METHODS: Between 1996 and 1998, five patients (three men, two women; average age 56 +/- 1 years; range: 56 to 66 years) with thrombosis of left-sided bileaflet mechanical valves were treated with videoassisted thrombectomy of the prosthesis. Four patients had thrombosis of a bileaflet mitral mechanical valve, and one patient had thrombosis of an aortic valve prosthesis. Preoperatively, patients were in either NYHA functional class IV (n = 4) or class I (n = 1). Surgery was performed through a right anterior thoracotomy or a median sternotomy. A rigid 30 degrees thoracoscope was inserted into the left atrium or aorta to visualize the thrombosed valve. The thrombus was extracted and the prosthesis under-surface examined and cleaned. Leaflet mobility, assessed with transesophageal echocardiography, was normal following surgical thrombectomy. RESULTS: Mean cardiopulmonary bypass time was 102 +/- 30 min; mean aortic cross-clamping time was 47 +/- 25 min. There was no hospital mortality; mean hospital stay was 9 +/- 1 days (range: 6 to 11 days). Anticoagulation with intravenous heparin was resumed 24 h after surgery. Three patients were discharged on coumarin treatment alone; two patients received aspirin plus coumarin. Mean postoperative follow up was 7 +/- 8 months (range: 1 to 21 months). One patient died 21 months after thrombectomy of a mitral prosthesis, with an unconfirmed diagnosis of recurrent mitral valve dysfunction. At 1-15 months after surgery, four patients are in NYHA class I, without evidence of prosthesis dysfunction. CONCLUSION: Videoassisted thrombectomy of a bileaflet mechanical heart valve is a treatment option in patients with acute thrombosis of the prosthesis.

Anticoagulants↗

PubMed1991

Prosthetic heart valve evaluation in vitro: critical aspects of data comparability.

The technology of heart valve substitution has considerably improved in the last few years, but its reliability after implantation is still not good enough, hence the need to study new valve design and improve quality testing. Different pulse duplicators are used for heart valve testing, but the results depend very much on the system adopted and the measurement protocol. Tests on two pulse duplicators currently used at the Biomedical Engineering Laboratory at the Istituto Superiore di Sanità, Rome, are reported here. The most significant parameters for valve evaluation were measured following each system's own protocol. Attention was focused on vascular load tuning when setting up the system and on the relationship between drive unit flow waveform and valve regurgitation and energy loss measurements. Standardization criteria must be defined in order to ensure the reliable comparability of in vitro testing results.

Coronary Circulation↗

PubMed1976

[Survival of 51cr-tagged red blood cells in patients with artificial heart valves (author's transl)].

Survival of 51Cr-tagged erythrocytes is determined in 10 patients approximately 1 week after insertion of an artificial heart valve ("early hemolysis") and in 9 patients approximately 2 years after heart valve replacement ("late hemolysis"). Red blood cell survival is found to be significantly reduced in all patients following insertion of an artificial heart valve as compared to a group of control patients. Hemolysis is significantly more pronounced in the early postoperative phase than two years postoperatively. LDH and plasma hemoglobin are relatively good indicators of hemolysis but less reliable than the determination of t/2 Cr.

Adult↗

PubMed1991

[The differential diagnosis and principles of the prevention of thromboembolic complications in pregnant women with artificial heart valves].

Clinical and hemostasiologic examinations of 28 pregnant women with artificial heart valves helped detect various mechanisms of thrombophilia development. Marked platelet hyperactivity was detected in all the examinees, regarded as the principal pathogenetic risk factor of arterial thromboembolism. A wave-like course of the DIC syndrome with hypercoagulation replaced by hypocoagulation was recorded in 79.6% of pregnant women with artificial heart valves. Differentiated controlled antithrombotic therapy, administered with due consideration for the cause of thrombophilia, helped prevent thromboembolic complications.

Adult↗

PubMed2001

Heart valve surgery in China: yesterday and today.

The past 20 years have seen rapid development in heart valve surgery in China. By the late 1990s, there were 6000 heart valve operations performed each year. Statistical analysis has shown that rheumatic heart disease is still the leading cause of valvular damage leading to surgery, as it had been 40 years before. The progressive fibrosis, sclerosis and calcification of the mitral valve that characterises rheumatic heart disease caused high mortality for all forms of mitral valve surgery in China in the 1960s. At that time, the introduction of closed mitral commissurotomy, initially highly effective in alleviating symptoms, was later found to result in re-stenosis in a significant cohort of patients. This was progressively replaced with open mitral commissurotomy. Today, mitral valve replacement represents 60-70% of valvular replacement procedures, followed by double-valve (mitral and aortic) replacement (20-25%). It has been shown both in China and elsewhere that careful selection of patients for an absence of mitral calcification leads to higher success rates for surgery. Heart valve replacement surgery in China now attains international standards in terms of the numbers of cases and surgical outcomes. Further long-term data collection and analysis are essential to aid the further development of the field.

Journal Article↗

PubMed1997

Survey of cardiac surgeons' perceptions of the addition of ASA to warfarin for patients with mechanical heart valves.

Evidence suggests that the addition of acetylsalicylic acid (ASA) to warfarin therapy among patients with mechanical heart valves may reduce mortality, at a slightly higher bleeding risk. A survey was conducted of North American cardiac surgeons to assess whether they routinely use ASA in conjunction with anticoagulants among such patients. From a list of 142 cardiac surgeons and centres, questionnaires were successfully transmitted by fax to 137. Respondents were surveyed about their prescribing habits of both warfarin and ASA among patients with mechanical heart valves. Information collected included the target international normalized ratio (INR) and reasons for not routinely prescribing ASA, when applicable. One hundred and eighteen cardiac surgeons (86%) returned the questionnaire: 75% were American and 25% Canadian. All surgeons (100%) stated that they use warfarin for patients with mechanical valves, but there was little consensus about the target INR. Only 25 respondents (21%) routinely used ASA in conjunction with anticoagulants, while 90 (76%) said they would not. The most common reason cited for withholding ASA was the perceived increased risk of bleeding (49% of nonusers), while another 23% felt that there is no benefit. Of the 90 surgeons who would not routinely prescribe ASA, 50 (55%) would on occasion. The most commonly used dose of ASA was 80 to 100 mg daily (79%). Low dose ASA, in conjunction with warfarin, is underused by North American cardiac surgeons for the prevention of systemic thromboembolism among patients with mechanical heart valves. Most surgeons avoid ASA out of concern for the increased risk of hemorrhage and a belief that there is no benefit. These perceptions are not supported by recent scientific data, however.

Anticoagulants↗

PubMed1978

Cholelithiasis: a frequent complication of artificial heart valve replacement.

The results of this investigation reveal that 39 per cent of patients in a study group of 46 patients with heart valve prostheses had gallstones if they survived 18 months or longer following valve replacement. In contrast, the prevalence of gallstones in a general population of autopsied rheumatic heart disease patients, including those who had been operated for severe valvular heart disease and had not survived for more than one month, was only 12 per cent. These findings suggest that gallstones are a frequent late complication of heart valve replacement.

Adult↗

PubMed1988

Advances in prosthetic heart valves: fluid mechanics of aortic valve designs.

The in vitro hemodynamic characteristics of a variety of mechanical and tissue heart valve designs used during the past two decades were investigated in the aortic position under pulsatile flow conditions. The following valve designs were studied: Starr-Edwards ball and cage (model 1260), Björk-Shiley tilting disc (convexo-concave model), Medtronic-Hall tilting disc, St. Jude Medical bileaflet, Carpentier-Edwards porcine and pericardial (models 2625, 2650 and 2900), Hancock porcine (models 250 and 410) and Ionescu-Shiley standard pericardial. The Starr-Edward ball and cage, Björk-Shiley tilting disc, Carpentier-Edwards porcine (model 2625) and Ionescu-Shiley standard pericardial valves were designed prior to 1975, while the Medtronic-Hall tilting disc, St. Jude Medical bileaflet, Hancock porcine (model 250), Hancock II porcine (model 410), Carpentier-Edwards porcine (model 2650) and Carpentier-Edwards pericardial (model 2900) valves were designed after 1975. The pressure drop results indicated that the valves designed prior to 1975 had performance indices of 0.30 to 0.45, whereas the valves designed after 1975 had performance indices of 0.40 to 0.70. The regurgitant volumes were higher for the mechanical designs (5.0 to 11.0 cm3/beat) compared to the tissue bioprostheses (1.0 to 5.0 cm3/beat). Two-dimensional laser Doppler anemometry studies indicated that the valves designed after 1975 tended to create more centralized flow fields, with reduced levels of turbulent shear stresses. However, none of the current valve designs is ideal: they all create areas of stasis and/or regions of low velocity reverse flow; and regions of elevated turbulent shear stresses that are capable of causing sub-lethal and/or lethal damage to the formed elements of blood.

Aortic Valve↗

PubMed1990

[In vitro hydrodynamic characteristics of heart valves in tricuspid position].

At present there are many problems concerning the choice of heart valve for cardiac valve replacement in the tricuspid position. Thus, we devised an attachment head for the prosthetic valve in order to evaluate the hemodynamic characteristics of four clinically-available mechanical prosthetic valves and two xenografts in the pulsatile circulation system in the tricuspid position. Six artificial cardiac valves were used in this experiment; St. Jude Medical (SJM), Starr Edwards ball (S-E), monostrut Björk Shiley (B-S), Omnicarbon, Carpentier Edwards (CE) supraannular, CE-pericardial whose tissue annulus diameter was 27 mm. The experimental instrument similar to that of Umezu et al, was prepared to determine the mean pressure gradient, output and calculated orifice area of each valve. Since many of the patients who must undergo tricuspid valve replacement have severe multi valvular diseases with atrial fibrillation, we experimented also under the condition of atrial fibrillation. At sinus rhythm under pulsation flow, no significant difference was shown in cardiac output between the various valves, but pressure gradient was higher with xenografts than with mechanical prostheses, and the SJM valve showed the widest efficient valve orifice area. The reduction rate of the efficient valve orifice area from sinus rhythm to atrial fibrillation was about 10% in the SJM valve, which was better rate than other heart valves. We observed significant differences in cardiac output, pressure gradient and efficient orifice area at sinus and atrial fibrillation rhythm. (p less than 0.01).

Atrial Fibrillation↗

PubMed1996

A three-dimensional, time-dependent analysis of flow through a bileaflet mechanical heart valve: comparison of experimental and numerical results.

The flow through a bileaflet mechanical heart valve during the first half of systole was predicted using computational fluid dynamics (CFD). A three-dimensional model of the geometry of the ventricle, valve, sinus and aorta was developed. Flow through the valve was assumed to be Newtonian and laminar. The peak systolic Reynolds number was 1500 based on the aortic radius and the mean aortic velocity. Flow visualisation and laser Doppler anemometry (LDA) experiments were performed and the results were compared to the CFD model. Good agreement between the LDA measurements and CFD predictions was found in the jets through the major orifices of the valve. The global flow fields predicted by the CFD showed reasonable agreement with the flow visualisation. A starting vortex was shed from the valve leaflets of the CarboMedics valve and the prototype valve. As systole progressed the two major orifice jets were directed towards the aortic wall and a weaker central jet was seen in both the experimental and CFD models. Large vortices were present on either side of the central orifice jet in the sinus area of both models. The three-dimensional time-dependent CFD model was considered to give a reasonable indication of the dominant flow patterns downstream of the bileaflet heart valve and has the potential to be an extremely useful tool to analyse the different designs of existing and future bileaflet valves.

Aorta↗

PubMed2001

Computational fluid dynamics study of a protruded-hinge bileaflet mechanical heart valve.

BACKGROUND AND AIM OF THE STUDY: Following clinical experience with the Medtronic Parallel bileaflet mechanical heart valve, considerable interest has been shown in investigating fluid mechanics inside the hinge socket. Most of these studies involved hinges that are recessed into the valve housing, such as the St. Jude Medical (SJM), CarboMedics, Sorin and On-X bileaflet mechanical heart valves. The aim of this study was to investigate the flow fields of a protruded hinge under steady flow conditions, with the occluder in its fully open position. Computational fluid dynamics (CFD) simulation using the Fluent 4.4.7 commercial solver was applied in this investigation. This protruded hinge mechanism for pivoting the occluder is an in-house design from the Cardiovascular Dynamics Laboratory, Nanyang Technological University. METHODS: The Fluent 4.4.7 code was run on a Silicon Graphic Inc. computer (4-CPUx185 MHz) in the CFD simulation. A body-fitted coordinates (BFC) grid was generated to cover the entire valvular flow domain, including the interior of the hinge and leaflet. Clearance between the leaflet and pivot housing was 50-70 microm. In the vicinity of the protruded hinge, mesh cells were small compared with hinge dimensions. A power law distribution of grid points was applied to optimize the number of cells used to cluster the entire flow field. The overall computational flow domain of the valve channel, including the floating leaflet and immersed hinge, was approximately 170,000 cells in total. Inside the hinge socket, approximately 10,000 cells were generated. A comparative model with recessed hinge that resembled the SJM valve hinge design was modeled. Due to geometric difficulties, an unstructured grid scheme was applied. Great attention was focused within the hinge pocket, in particular to the clearance between the hinge pivot and leaflet. A total of 2 million cells was generated for the whole computational flow domain. RESULTS: Under steady flow conditions, with the leaflet fixed in an open position, the protruded hinge design yielded a pair of small vortices that formed behind the stoppers. A low-magnitude velocity was observed inside the hinge clearance. Vortices developed behind the protruded stopper. Migrating flow was noted beneath the leaflet clearance as a result of pressure difference across the leaflet. For the recessed hinge design, reverse flow dominated the inside of the hinge socket, and developed into a pair of vortices at high Reynolds number. CONCLUSION: The protruded hinge mechanism was designed to expose the overall hinge region to the mainstream flow for a positive washing effect. Flow in this protruded hinge design is, in general, found to be three-dimensional. Initial results under steady flow conditions showed low laminar and turbulent shear stress, while the hinge clearance was well washed.

Computer Simulation↗

PubMed1991

[Ultrastructural analysis of myocardial condition during cardioplegic protection in heart valve prosthesis].

The article deals with the results of ultrastructural study of the myocardium at three stages of cardiosurgical operations: preischemic, ischemic, and during reoxygenation. A statistically significant difference was revealed in the condition of the cardiomyocyte organelles in each of these stages, and the degree of their intraoperative destruction was determined. It is concluded that ischemia of more than 90 minutes redoubles the progress of irreparable changes of the cardiomyocytes, particularly in patients with severe damage to the myocardium in the preischemic stage. The search for means of cardioprotection for these patients must be continued.

Adult↗

PubMed1993

Potential flaws in the assessment of minor cerebrovascular events after heart valve replacement.

The specificity and sensitivity of the questionnaire method, whether through direct contact or via mail, in collecting information on thrombosis, embolism and bleeding after heart valve replacement were assessed by a critical analysis of methods currently in clinical use. The 16 questions contained in the standard questionnaire of the Albert Einstein College of Medicine searching for transient events were put to 1000 apparently healthy individuals. Additional questions related to risk factors such as previous heart valve replacement, any existing heart disease, hypertension, diabetes or current anticoagulant treatment for any reason were also asked. The male/female ratio was 54.9/45.1, and the mean age was 36.3 years with a range of 14-97 years. Eighty-five persons had one or more risk factors, 915 had none. A positive answer to at least one of the questions searching for TIA (transient ischemic attack) was given by 69.4% (n = 59) of those with, and by 54.8% (n = 501) without any risk factors. The total number of reported 'events' was 164 (1.93/person) for those with, and 1331 (1.45/person) for those without any risk factors. Four different follow up methods were applied to each of 123 patients after heart valve replacement: (a) regular follow up at an out-patient clinic, questionnaires sent at (b) six, (c) 18 and (d) 36 months after the start of the study. 57% of the transient and reversible events reported at the out-patient clinic were forgotten and not mentioned by the same patients in the 36 month questionnaire. One of the three permanent disabilities was also 'forgotten'.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗

PubMed1996

In vivo comparison of hemocompatibility of materials used in mechanical heart valves.

BACKGROUND AND AIMS OF THE STUDY: Most studies of mechanical heart valve prostheses in recent years have focused on the hydrodynamic and clinical performance of different valve designs. Little attention has been paid to the hemocompatibility (thrombogenicity) of materials used in the prostheses. METHODS: In the present study, three materials currently used in mechanical heart valves, titanium, cobalt-chromium alloy (Haynes 25) and pyrolytic carbon (Pyrolite), together with a surface-modified (methylated) titanium, were evaluated and compared for their hemocompatibility in a sheep model. The test materials in the form of discs were glued to plastic buttons and implanted into the intrathoracic venae cavae of anesthetized sheep. Four different materials were tested simultaneously in each animal: two in the superior and two in the inferior vena cava. Eight animals were used. After two hours of exposure to flowing blood, the discs were explanted and evaluated for their hemocompatibility using close-up photography and scanning electron microscopy (SEM). Thrombus formation and blood cell adhesion were studied quantitatively. RESULTS: The results showed that there was significantly more thrombus on pyrolytic carbon and methylated titanium than on titanium and cobalt-chromium (p < 0.05). More leukocytes adhered on pyrolytic carbon and cobalt-chromium than on titanium and methylated titanium (p < 0.05). CONCLUSION: The results indicate that titanium and cobalt-chromium under the present condition were more hemocompatible than pyrolytic carbon. The clinical significance of the finding remains to be investigated.

Adhesiveness↗

PubMed1987

[Comparative study of mechanical heart valves for implantation in mitral position].

For hydrodynamic comparison of mechanical heart valves, three tilting disc valves (Björk-Shiley SD, Björk-Shiley CCD, Björk-Shiley Monostrut) and two bileaflet valves (St. Jude Medical, Duromedics) with annulus diameter dA = 31 mm were perfused in a mock circulation in mitral position. Flow, pressure, and orifice area were measured during pulsatile flow. Insufficiency, maximal orifice area, mean orifice area, performance index and efficiency index were calculated. The tilting disc valves show distinctly lower orifice areas than the bileaflet valves. The mean value of maximal orifice area Amax of the Björk-Shiley prostheses varies between 227.82 +/- 7.77 mm2 and 243.21 +/- 6.21 mm2. The mean value of Amax of the Duromedics prosthesis is 295.45 +/- 7.76 mm2 and that of the St. Jude Medical prosthesis is 477.43 +/- 11.32 mm2. The calculated mean orifice areas A of the bileaflet valves are also higher than those of the tilting disc valves. The mean values of A are: Björk-Shiley SD: 183.55 +/- 10.03 mm2; Björk-Shiley CCD: 206.30 +/- 8.62 mm2; Björk-Shiley Monostrut: 210.12 +/- 4.74 mm2; St. Jude Medical: 398.69 +/- 19.55 mm2; Duromedics: 262.90 +/- 6.84 mm2. The performance index PI is qualitatively identical with the values of the mean orifice area A because in this study only heart valves of the same size were investigated. For calculation of insufficiency I the entire reflux volume VR including closing volume VS and leakage volume VL was used, thus, insufficiency was also determined in intact prostheses. The values of insufficiency of the mechanical valves investigated are higher for the bileaflet valves than for the tilting disc valves.(ABSTRACT TRUNCATED AT 250 WORDS)

Bioprosthesis↗

PubMed2002

Effects of combined therapy of clopidogrel and aspirin in preventing thrombus formation on mechanical heart valves in an ex vivo rabbit model.

BACKGROUND: The aim of our study was to investigate the efficacy of the combination of clopidogrel and aspirin in the prevention of thrombus formation on artificial heart valves in an experimental rabbit model as compared to anticoagulation with warfarin. METHODS: Studies were performed after oral administration of clopidogrel and aspirin in group I (n=9) for 5 days, after 5+/-2 days treatment with warfarin in group II (n=9) and without medication in group III (n=9). Leaflets from Sulzer Carbomedics bileaflet valves were placed in a flow chamber. The flow chamber was filled with blood in a continuous circulation between the carotid artery and the jugular vein. RESULTS: In group III, the flow chamber was clotted after a median of 15 min of circulation. Weight analysis before and after 1 h of perfusion showed that the median thrombus weight was 9.1 mg in group I, 14.4 mg in group II and 33.7 mg in group III. Further analysis by electron microscopy showed fewer platelets and erythrocytes on leaflets in group I than on leaflet surfaces in group II. CONCLUSION: Clopidogrel and aspirin were more effective than warfarin in preventing thrombus formation on artificial heart valve leaflets in our investigation. This rabbit model with a high dosage of clopidogrel and aspirin, and a short-time exposure of the heart valve leaflets to rabbit blood under laminar flow, should be further evaluated with respect to whether it can give information about antithrombotic regimens in patients after mechanical heart valve replacement.

Animals↗

PubMed2004

Late incidence and determinants of reoperation in patients with prosthetic heart valves.

OBJECTIVES: Reoperation is a relatively common event in patients with prosthetic heart valves, but its actual occurrence can vary widely from one patient to another. With a focus on bioprosthetic valves, this study examines risk factors for reoperation in a large patient cohort. METHODS: Patients (N=3233) who underwent a total of 3633 operations for aortic (AVR) or mitral valve replacement (MVR) between 1970 and 2002 were prospectively followed (total 21,179 patient-years; mean 6.6+/-5.0 years; maximum 32.4 years). The incidence of prosthetic valve reoperation and the impact of patient- and valve-related variables were determined with actual and actuarial methods. RESULTS: Fifteen-year actual freedom from all-cause reoperation was 94.1% for aortic mechanical valves, 61.4% for aortic bioprosthetic valves, 94.8% for mitral mechanical valves, and 63.3% for mitral bioprosthetic valves. In both aortic and mitral positions, current bioprosthesis models had significantly better durability than discontinued bioprostheses (15-year reoperation odds-ratio 0.11+/-0.04; P<0.01 for aortic, and 0.42+/-0.14; P=0.009 for mitral). Current bioprostheses were significantly more durable in the aortic position than in the mitral position (14.3+/-6.8% more freedom from 15-year reoperation; (P=0.018)). Older age was protective, but smoking was an independent risk factor for reoperation after bioprosthetic AVR and MVR (hazard ratio for smoking 2.58 and 1.78, respectively). In patients with aortic bioprostheses, persistent left ventricular hypertrophy at follow-up and smaller prosthesis size predicted an increased incidence of reoperation, while this was not observed in patients with mitral bioprostheses. CONCLUSIONS: These analyses indicate that current bioprostheses have significantly better durability than discontinued bioprostheses, reveal a detrimental impact for smoking after AVR and MVR, and indicate an increased reoperation risk in patients with a small aortic bioprosthesis or with persistent left ventricular hypertrophy after AVR.

Adult↗