Heart valve replacement with bioprosthesis. (1) General concepts and graft management.
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Animals↗
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Thrombotic obstruction of bileaflet mechanical prosthetic heart valves: early diagnosis and management.
BACKGROUND: Thrombosis of mechanical prosthetic heart valves (TMPHV) is one of the major complications that accounts for the highest morbidity and mortality related to Bileaflet Mechanical Prosthetic Heart Valves (BMPHV). MATERIALS AND METHODS: During the last six years we had ten cases of bileaflet mechanical valve thrombosis. All patients had undergone emergency surgical interventions except one who developed systemic embolization and massive brain insult immediately after admission for surgery and died two months later. We divided the patients in two groups, first group includes five patients who came in acute pulmonary edema and emergency operation was done either to replace the thrombosed BMPHV (in two) or successful thrombectomy was achieved (in three) and all of them have survived. The second group (four patients) presented with cardiogenic shock and required emergency femoro-femoral bypass. Two patients survived after thrombectomy and the other two could not come off bypass after changing the TMPHV and in spite of Intra-aortic balloon pump, they died 24 and 48 hours after the procedure. All patients received intravenous heparin on admission. Preoperative i.v. Streptokinase was given in two cases, of which one required thrombectomy and the other had valve replacement and died 24 hours later. RESULTS: Early diagnosis and operation still had the best results in TMPHV though thrombolytic therapy was successful in few reported early presented cases. All patients who had thrombectomy of the TMPHV have survived without any morbidity. Follow up of survived patients ranged between two months and six years with a mean of 24.1 months. It is worth attempting thrombectomy of the thrombosed BMPHV rather than re-replacement which carries higher morbidity and mortality, because of the longer ischemic arrest during operation which further depletes the energy of the myocardium. CONCLUSIONS: Though this is a small number of patients to make a definite conclusion, thrombectomy was more feasible in CarboMedics Prosthetic Heart Valves, since its in situ rotation that allows reorientation of its leaflets and declotting of valve hinge to be performed.
Adult↗
Decellularization does not eliminate thrombogenicity and inflammatory stimulation in tissue-engineered porcine heart valves.
BACKGROUND AND AIM OF THE STUDY: In tissue engineering of heart valves using decellularized xenogenic valves, it has been suggested that cell elimination would result in a biologically inert matrix. The aim of this in-vitro investigation was to evaluate different decellularization methods in regard to the completeness of cell removal, inflammatory response, and thrombocyte activation. METHODS: Decellularized porcine Synergraft valves were compared with porcine pulmonary conduits decellularized with Triton X-100, sodium deoxycholate, Igepal CA-630 and ribonuclease. Completeness of decellularization was evaluated with staining for nuclei and alpha-Gal epitope. Decellularized heart valves with and without seeding with endothelial cells (ECs) were incubated with human platelet-rich plasma and stained for CD41 and PAC-1 to evaluate thrombocyte activation. Samples were processed for laser scanning microscopy (LSM) and scanning electron microscopy (SEM). Migration of human monocytic cells towards extracted valve proteins was tested. RESULTS: In contrast to the Synergraft, complete cell removal and elimination of the alpha-gal epitope was achieved with the new decellularization method. Numerous adherent and activated platelets were found on the decellularized matrix. This was inhibited by seeding with ECs. Even in completely cell-free valve tissue extracellular matrix proteins attracted human monocytic cells as in early inflammation, depending on whether porcine or human tissue was used. CONCLUSION: Important differences were found in the decellularization efficacy of treatment methods. However, even complete elimination of cells and their remnants did not result in a biologically inert matrix. The decellularized porcine heart valve matrix has the potential to attract inflammatory cells and to induce platelet activation. These findings suggest that it will be important to control the different inflammation-stimulating factors if porcine tissues are to be used successfully in tissue engineering.
Animals↗
[Perioperative complications in at-risk patients undergoing heart valve surgery].
The success of operations of the replacement of heart valves is disturbed by perioperative complications and early lethality. A valuation of the perioperative risk individually of patients with operations of the replacement of heart valves according to defined subgroups is controlled by the perioperative course. In order to achieve the registration of patients with perioperative lesion of the myocardium and/or low output syndrome, the bedside performance of a marker protein monitoring consisting of enzymes/isoenzymes (CK, CK-MB, ALAT) and the muscle protein myoglobin, respectively, is necessary. In 38% of the patients with operation of the replacement of heart valves the preoperative risk constellation was objectified early-postoperatively with the proof of complication and thus the strategy of the preoperative individual valuation of the risk confirmed. Altogether patients with replacement of the aortic valve showed the smallest rate of perioperative complications in comparison to patients with replacement of the mitral valve (re-operation in replacement of the mitral valve, double valve replacement, replacement of the mitral valve with restricted left-ventricular function).
Bioprosthesis↗
Choice of prosthetic heart valves:update for the next generation.
Intervention for valvular heart disease poses unique clinical challenges in cardiology because the diseases are of relatively low prevalence, the interventions do not lend themselves to randomized comparative trials, and important clinical end points are assessed only after decades of follow-up. In addition, continuing advances in prosthetic heart valve technology make follow-up a moving target because long-term data by definition are available only for older prostheses. Newer tissue and mechanical prostheses afford superior hemodynamics compared with their older counterparts, and data suggest that durability and patient mortality are superior with newer compared with older bioprostheses. Arbitrary cutoffs dictating valve choice based predominantly on patient age may not give appropriate weight to individual patient perspectives. In educating and counseling patients regarding choices in heart valve prostheses, the clinician should help the patient weigh the relative merits for the individual patient of projected mortality, valve durability, and requirement for anticoagulation, with associated freedom from re-operation, hemorrhagic and thromboembolic risk, and impact on lifestyle.
Biomechanical Phenomena↗
[A new design of bileaflet heart valve to eliminate the blood flow disturbance].
The major problems of current clinically--used bileaflet heart valves are thromboembolism and hemorrhage related to anticoagulants. These bileaflet heart valves are considered as being unsatisfactory, because in the open position, two leaflets divide the ring orifice of the valve into three regions. In this obstructive orifice, the high turbulent shear stresses and the region of flow separation and stagnation all give rise to the occurrence of thrombosis. In our design of bileaflet heart valve, in the open position, no structural component or leaflet divides the ring orifice of the valve. Our bileaflet heart valve has the best possibilities for creating more natural blood flow Pattern which could decrease or eliminate the blood flow disturbance so as to reduce the risk of thrombosis and the needs for anticoagulation therapy.
Equipment Safety↗
Morphological analyses of ice-free and frozen cryopreserved heart valve explants.
BACKGROUND AND AIM OF THE STUDY: The pathophysiology of allogeneic heart valve failure is not fully understood. It is hypothesized that the rapid deterioration seen in some allograft heart valve recipients is due to disruptive interstitial ice damage that occurs during cryopreservation by freezing. METHODS: The hypothesis was tested by comparing a standard commercial heart valve freezing and ice-free, vitrification cryopreservation methods with fresh controls in: (i) a subcutaneous, juvenile rat implant model of calcification; and (ii) a descending thoracic aorta implant rat model for histopathology. Calcium concentrations in one- to six-week explants were determined using atomic absorption spectroscopy; calcification rates were also determined. RESULTS: The calcification rate of frozen valves was significantly greater (p < 0.01) than that of vitrified valves in both syngeneic and allogeneic recipients, supporting prior observations that ice-free cryopreservation reduces allogeneic heart valve calcification. Cryopreservation by freezing and vitrification resulted in mild morphological changes in two- and four-week explants, a slight decrease in leaflet cellularity, and a more rapid onset of intimal hyperplasia than in fresh valve explants. The allograft explant groups exhibited similar changes, regardless of how the valves were processed. CONCLUSION: These findings provide only weak support for the tested hypothesis, and further studies in a large animal model are warranted.
Animals↗
Eleven-year single-center experience with the ATS Open Pivot Bileaflet heart valve.
BACKGROUND: The ATS Open Pivot Heart Valve was first introduced in 1992 and has been implanted routinely at our institution since 1993. Valve selection was based on surgeon preference. The objective of this study is to retrospectively analyze our 11-year clinical results with ATS prostheses. METHODS: Between January 1993 and December 2003, 601 ATS valves (393 aortic valve replacement [AVR], 168 mitral valve replacement [MVR], 20 aortic plus mitral valve replacement [DVR]) were implanted in 581 patients (377 male, 204 female; mean age, 63.7 years; range 18 to 89). Preoperatively, 47 (8%) were New York Heart Association class I, 212 (36.5%) were class II, 267 (46%) were class III, and 55 (9.5%) were class IV. Preoperative comorbidities were coronary artery disease, 167 (29%); diabetes mellitus, 72 (12%); cerebrovascular disease, 2 (0.3%); endocarditis, 53 (9%); and atrial fibrillation, 115 (20%). RESULTS: Follow-up is 99% complete. Data represent 2,500 cumulative patient-years. Mean follow-up is 4.3 +/- 2.6 years (range, 0.1 to 11.6). Overall hospital mortality is as follows: AVR, 3.8% (15 patients); MVR, 1.8% (3 patients); DVR, 10% (2 patients). Structural valve failure was not encountered. Overall survival at 10 years is AVR, 84.7% +/- 3.1%, AVR plus coronary artery bypass, 67.5% +/- 8.2%; MVR, 59.8% +/- 7.1%, MVR plus coronary artery bypass, 39% +/- 27.8%; and DVR, 74.3% +/- 10%. Freedom from valve-related death at 10 years is AVR, 99.2%; MVR, 94.6%; and DVR, 100%. Linearized rates for postoperative complications are paravalvular leak, 0.6% per patient-year; valve thrombosis, 0.04% per patient-year; thromboembolism, 1.1% per patient-year; major bleeding, 0.5% per patient-year; and de novo prosthesis endocarditis, 0.1% per patient-year. Postoperative mortality risk was significantly elevated by diabetes (p < 0.01), but not by other comorbidities. CONCLUSIONS: Our 11-year experience demonstrates low rates of adverse events and valve-related complications with the ATS Open Pivot heart valve.
Adolescent↗
Concentrations of mezlocillin in the serum, heart valves, muscle and subcutaneous tissue of patients undergoing open-heart surgery.
4 g mezlocillin as a five-minute intravenous bolus were given preoperatively to 31 adult patients undergoing open-heart surgery. Mezlocillin serum levels declined from 42.8 mg/l at 1-2 h after injection to less than 1 mg/l at 6-8 h after application. Concentrations in muscle and subcutaneous tissue varied between 18 micrograms/g and less than 1 microgram/g. Mezlocillin levels in heart valves were higher than those in muscle and subcutaneous tissue, thus suggesting rapid diffusion of mezlocillin.
Adipose Tissue↗
The decellularized porcine heart valve matrix in tissue engineering: platelet adhesion and activation.
An approach in tissue engineering of heart valves is the use of decellularized xenogeneic matrices to avoid immune response after implantation. The decellularization process must preserve the structural components of the extracellular matrix to provide a biomechanically stable scaffold. However, it is known that in vascular lesions platelet adhesion to extracellular matrix components occurs and platelet activation is induced. In the present study we examined the effects of a decellularized porcine heart valve matrix on thrombocyte activation and the influence of re-endothelialisation in vitro. Porcine pulmonary conduits were decellularized using Triton X-100, Na-deoxycholate and Igepal CA-630 followed by a ribonuclease digestion. Cryostat sections of decellularized heart valves with and without seeding with human umbilical vein endothelial cells (HUVEC) were incubated with platelet rich plasma. Samples were either stained with fluorescent antibodies for CD41 and PAC-I (recognizing the activated fibrinogen receptor) or fixed with glutaraldehyde. Thereafter, the samples were processed for laser scanning microscopy (LSM) or scanning electron microscopy (SEM). Examination by LSM showed numerous platelets with co-localized staining for CD41 and PAC-1 on the nonseeded decellularized heart valve matrix whereas after seeding with endothelial cells no platelet activation was detected. SEM revealed platelet adhesion and aggregate formation only on the surface of the non-seeded or partially denuded matrix specimens. We show in this study that the decellularized porcine matrix acts as a platelet-activating surface. Seeding with endothelial cells effectively abolishes the platelet adhesion and activation and therefore is necessary to eliminate thrombogenicity in tissue engineered heart valves.
Animals↗
Particle image velocimetry in the investigation of flow past artificial heart valves.
Full-field measurement of instantaneous velocities in the flow field of artificial heart valves is vital as the flow is unsteady and turbulent. Particle image velocimetry (PIV) provides us the ability to do this as compared to other point measurement devices where the velocity is measured at a single point in space over time. In the development of a PIV system to investigate the flow field of artificial heart valves, many problems associated with the project arose and were subsequently resolved. Experience gained in the setting up of an environment conducive for PIV studies of artificial heart valves; from seed particle selection to refractive index matching, and the evolution of computer algorithms to satisfy the varied flow conditions in artificial heart valves are presented here. Velocity profiles and distributions are computed and drawn for a porcine tissue heart valve based on measurements with the PIV system developed.
Algorithms↗
Major hepatic resection in patients with a prosthetic heart valve receiving anticoagulation treatment.
We experienced two patients with a prosthetic heart valve, who underwent hepatic resection for hepatoma while on anticoagulation therapy. Patients with a prosthetic heart valve have the following characteristics; an increased risk of thromboembolism due to diminished anticoagulation in the perioperative period, a greater risk of endocarditis due to the artificial material in the heart, and impaired cardiopulmonary function including possible arrhythmia and heart failure. Furthermore, when such patients also have liver cirrhosis with a hepatoma, there is an increased risk of perioperative bleeding while on anticoagulation due to coagulopathy and also a risk of infection due to decreased cellular immunity. Patients with a prosthetic heart valve therefore require special care and attention whenever they have to undergo hepatic resection. With respect to anticoagulation, a minimal level is required to prevent bleeding and thromboembolism. Warfarin being administered preoperatively may be switched to heparin while closely monitoring the activated clotting time (biomaterial valve: 130-150 sec, non-biomaterial valve: 150-180 sec); the heparin should then be changed back to warfarin immediately after starting oral intake following operation. For the prevention of infection, a broad spectrum antibiotic should be used prophylactically both intra-operatively and postoperatively. The cardiopulmonary function must also be carefully monitored. For the assessment of postoperative liver function, lecithin: cholesterol acyltransferase, serum bilirubin and albumin are useful because there is no relevance of coagulation parameters such as prothrombin time under anticoagulation.
Carcinoma, Hepatocellular↗
A guide to the radiographic identification of prosthetic heart valves.
To facilitate the radiographic identification of prosthetic heart valves, radiographic silhouettes of various aortic, mitral and tricuspid valve prostheses were analyzed and shematized. Forty different prosthetic valve models (heterograft and mechanical) were obtained from seven domestic manufacturers. Each prosthesis was positioned to approximate the aortic, mitral or tricuspid valve anulus plane. The valves were then radiographed and photographed as they would appear in posteronanterior and left lateral chest radiographs. The radiographic silhouettes were examined and a scheme was designed to enable easy, yet accurate, differentiation of the many heart valve prostheses. Illustrations of the various valve types are presented as they would appear in routine chest radiographs.
Heart Valve Prosthesis↗
Mechanical heart valve cavitation.
Cavitation was first directly related to mechanical heart valves in the mid 1980s after a series of valve failures observed with the Edwards-Duromedics valve. The damages observed indicated that cavitation could be responsible. Later, several in vitro studies visualized the bubble formation and collapse of cavitation at mechanical heart valves. It was suggested that cavitation could also cause damage to the formed elements of blood and thereby enhance the risk of thromboembolic complications seen in mechanical heart valve patients. Therefore, an applicable technique for in vivo detection of cavitation is required. This article reviews techniques developed for in vivo detection of cavitation and suggests focus for future studies.
Computer-Aided Design↗
[Assessing the transvalvular gradient of a Chinese-made jiuling solid pyrolytic carbon bileaflet heart valve prosthesis].
In order to assess the transvalvular gradient of a Chinese-made Jiuling solid pyrolytic carbon bileaflet heart valve prosthesis, we determined its hydrodynamics in the laboratory and then measured the hemodynamic performance in the animals and patiens. The Jiuling prosthesis was tested in a pulsatile flow simulator in the aortic position. Six sheep subjected to mitral replacement with 21 mm Jiuling prosthesis were measured by open cardiac catheterization intraoperatively. Doppler echocardiography and open cardiac catheterization under dobutamine stress were performed in two sheep 60 months after implantation. Clinically, 14 cases of aortic valve and 10 cases of mitral valve in the patients who underwent valve replacement with Jiuling heart valve prosthesis were measured by open cardiac catheterization and Doppler echocardiopgraphy. The results showed that Juiling heart valve prosthesis had lower mean transvalvular gradient (below 10 mmHg) at any given tissue annulus diameter. In animal experiments, the transvalvular gradients of 6 sheep were 5.2 +/- 1.7 mmHg intraoperatively, and of 2 sheep 60 months after implantation were 6.1 +/- 0.3 mmHg by catheterization. In patients, the mean transvalvular gradients in the aortic position measured by means of catheterization and echocardiography were 6.26-4.10 mmHg and 9.42-7.48 mmHg; the gradients in the mitral position were 2.10-1.9 mmHg and 5.281-4.10 mmHg respectively. The above results demonstrate that Jiuling valve prosthesis has excellent hemodynamic performance.
Adult↗
The Ultracor tilting disc heart valve prosthesis: a seven-year study.
BACKGROUND AND AIM OF THE STUDY: The Ultracor heart valve is a recent entry in the evolution of the tilting disc valve. This report summarizes the experience with the Ultracor valve from three European centers. METHODS: Between 1990 and 1996, 446 patients received 499 Ultracor heart valve prostheses in 450 procedures, including 225 (50.0%) aortic, 172 (38.2%) mitral and 49 (10.9%) double valve replacements. An additional four (1.0%) patients had mitral valve replacement (MVR) added to a previous aortic valve replacement (AVR) and were considered double valve replacement (DVR) patients. The total follow up was 751 patient-years (pt-yr) for AVR (mean 3.4), 440 pt-yr for MVR (mean 2.6) and 125 pt-yr for DVR (mean 2.4). Nine patients (one AVR, eight MVR) were lost to follow up, which was 98% complete. RESULTS: The actuarial survival rate, including operative mortality rate, at five years was 90% for AVR, 77% for MVR and 82% for DVR. The linearized complication rates (%/year) for AVR, MVR and DVR were: 2.1, 4.0 and 4.0 for late mortality; 0.1, 3.0 and 0.8 for thromboembolism; 0, 0.2 and 0 for thrombosis; 2.0, 1.6 and 1.6 for anticoagulant-related hemorrhage (ACH); 0.3, 0.5 and 1.6 for prosthetic valve endocarditis (PVE); and 0.5, 0.9 and 3.2 for reoperation, respectively. The actuarial rates of freedom from complications at five years were: thromboembolism, 99% for AVR and 88% for MVR; thrombosis, 100% for AVR and 99% for MVR; ACH, 91% for AVR and 94% for MVR; PVE, 99% for AVR and 97% for MVR; reoperation, 98% for AVR and 98% for MVR. No structural failure was observed. CONCLUSIONS: Seven years' experience showed the Ultracor heart valve prosthesis to be comparable with other currently used mechanical heart valves. Continued evaluation of this prosthesis is warranted in order to obtain a more extended clinical follow up.
Adult↗
Development of the Valvo pump: an axial flow pump implanted at the heart valve position.
Pulsatile artificial hearts having a relatively large volume are difficult to implant in a small patient, but rotary blood pumps can be easily implanted. The objective of this study was to show the feasibility of using the Valvo pump, an axial flow pump implanted at the heart valve position, in such cases. The Valvo pump consists of an impeller and a motor. The motor is waterproofed with a ferrofluidic seal. A blood flow of 5 L/min was obtained at a pressure difference of 13.3 kPa (100 mm Hg) at 7,000 rpm. The normalized index of hemolysis (NIH) was 0.030 +/- 0.003 (n = 3) for a blood flow of 5 L/min at a pressure difference of 13.3 kPa. The pressure resistance of the ferrofluidic seal was 37.5 kPa in a static condition and 26.3 kPa at 10,000 rpm. The seal exhibited no leaks for 41+ days against 20.0 kPa. The results showed that the Valvo pump can maintain systemic circulation with an acceptable level of hemolysis.
Animals↗
Quality of life after heart valve replacement.
Over the last three decades, heart valve replacement has become a safe and routine surgical procedure, but replacement devices are still far from ideal. Despite improvements in materials and design, life-long anticoagulation remains mandatory for mechanical valves. The major shortcoming of the less thrombogenic bioprosthetic valves is early tissue failure. Parallel to the decrease in operative mortality after heart valve replacement, the potential quality of life for survivors has been becoming increasingly important in evaluating the late results and in selecting the appropriate device for the given patient. All factors that determine the quality of life are strongly affected by the operation due to the usually dramatic improvement both in subjective status and objective parameters postoperatively. The patient, thus, can return to normal activities, maintain self-esteem and keep normal relationships at work, in the community and at home. Psychoneurologic dysfunction was also found to decrease greatly within six months, although more than a quarter of patients were depressed preoperatively because of their disease. Overall, the experience was generally satisfying.
Adaptation, Psychological↗