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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↗

Doppler echocardiographic assessment of prosthetic aortic valve function. Findings in normal valves.

To determine the Doppler-derived aortic flow velocity profiles in relation to type of prosthetic valve and left ventricular function, 70 patients with normal functioning aortic prosthetic valves (group 1 = 44 patients with low-profile mechanical valves and group 2 = 26 patients with high-profile mechanical valves) were evaluated. Peak flow velocity and mean systolic gradient were inversely related to valve size (r = -0.72; r = -0.76) in group 1. On the other hand, aortic flow velocity profiles had significant correlations with left ventricular end-systolic dimension (r = 0.75; r = 0.76) and left ventricular fractional shortening (r = -0.69; r = -0.66) in group 2. Thus, aortic flow velocity profiles in the low-profile mechanical valve were affected by pressure gradient caused by the valve size, whereas the hydromechanical disadvantage of the high profile mechanical valve affected the left ventricular pump function and Doppler-derived flow velocity profiles.

Aortic Valve↗

Q fever endocarditis on porcine bioprosthetic valves. Clinicopathologic features and microbiologic findings in three patients treated with doxycycline, cotrimoxazole, and valve replacement.

Three patients developed Q fever endocarditis on porcine bioprosthetic valves. They had a subacute or chronic course with nonspecific symptoms, enlargement of the liver and spleen, and cardiac failure due to destruction of the cusps, without disruption of the valve ring. High-phase I-specific IgG and IgA antibody titers against Coxiella burnetii were found. C. burnetii was isolated in each patient by inoculating suspensions of valve tissue into a human fetal diploid fibroblast cell line, which was grown as monolayers on slides contained inside rubber-stoppered tube cultures. Patients were treated successfully with doxycycline, cotrimoxazole, and valve replacement and were followed up for periods of 24 to 42 months; no evidence of deterioration was found. The human fetal diploid cell culture may be an expeditious, easy, and safe method to isolate C. burnetii from cardiac valves. Valve replacement seemed necessary to cure prosthetic-valve endocarditis due to C. burnetii infection. Combined therapy with doxycycline and cotrimoxazole may control the disease and prevent reinfection of the homografts replacing the valves.

Adult↗

Mitral valve homograft for mitral valve replacement in acute bacterial endocarditis.

Homograft use for aortic valve replacement (AVR) in aortic valve acute bacterial endocarditis (ABE) has gained in popularity, due mainly to the relative resistance of homografts to infection. Recent success with mitral valve homograft use led us to apply homograft mitral valve replacement (MVR) in a patient with severe ABE that was not amenable to valve repair. Following surgery, the patient improved rapidly with normalization of infection parameters and chest radiography, and was discharged home on postoperative day 11. Follow up echocardiography showed good function of the homograft mitral valve with no regurgitation. After four months, the patient had normal valve function, with no evidence of infection. In conclusion, MVR with a mitral valve homograft in the setting of ABE was satisfactory, though patient follow up was relatively short (four months).

Echocardiography, Transesophageal↗

Stentless valved composite graft for replacement of the aortic valve and ascending aorta.

BACKGROUND: Conduits with biological valves are rarely used for aortic root replacement because of technical problems when degeneration of the valve prosthesis requires reoperation. A composite graft as described could likely avoid this problem. MATERIAL AND METHODS: Between November 1998 and November 1999, 28 consecutive patients underwent replacement of the ascending aorta and aortic valve with a stentless valved composite graft. The indication for surgery was aneurysm of the ascending aorta (26 patients) and aortic dissection (2 patients). The composite graft was assembled during surgery using a stentless porcine aortic bioprosthesis (Toronto SPV) and a woven polyester collagen-coated vascular prosthesis (InterGard). RESULTS: There was no hospital mortality. Echocardiographic evaluation before discharge showed excellent hemodynamics with a mean transvalvular gradient of 8.5 mmHg (standard deviation I3.0 mmHg) and no regurgitation across the valve. Within a follow-up period of up to one year there was one late death because of a cerebral hemorrhage under anticoagulation. CONCLUSIONS: The valved composite graft described offers the excellent hemodynamic performance of a stentless biological valve and is expected to avoid major technical difficulties should later replacement of the biological prosthesis due to structural failure become necessary, because only the valve cusps need to be resected, leaving the tube graft untouched.

Aged↗

The use of stentless valves for root replacement during repair of ascending aortic aneurysms with aortic valve regurgitation.

BACKGROUND: Early and mid-term results of stentless valves for the treatment of ascending aortic aneurysm (AAA) were evaluated in a retrospective manner. MATERIAL AND METHODS: During a four-year period, 26 patients with ascending aortic aneurysms and aortic valve insufficiency underwent a total root replacement procedure using a stentless "Freestyle" valve (Medtronic Inc., Minneapolis MN). Mean age was 71 +/- 4 years (range 66 to 79 years). Eight patients were in NYHA Class 2, 13 in Class 3, and 5 in Class 4. Cardiopulmonary bypass (CPB) was begun with femoral artery-right atrium (two-stage) cannulation in all cases but four, in which the right axillary artery was used. Myocardial protection was established by retrograde, cold-blood cardioplegia and direct antegrade blood cardioplegia from the right coronary ostium. The left ventricle outflow tract was constructed by using 2-0 ticron sutures and incorporating a pericardial strip in between. Coronary buttons were sewn to the xenograft with 6-0 polypropylene sutures. Meanwhile, the patient was cooled down to 18 degrees nasopharyngeal temperature and the distal anastomosis with the proximal arch was performed with a Dacron graft under total circulatory arrest (TCA), using 4-0 polypropylene sutures. During rewarming, the connection between the Freestyle valve and the Dacron graft was performed. RESULTS: Ischemic time was 91 +/- 11 minutes and TCA time was 9 +/- 4 minutes. Operative mortality was zero, and there was one 30-day mortality (3.8%). At discharge, all 25 patients had a functional valve with low transvalvular gradients. Patients were followed for a mean period of 15 months, with one patient being lost to follow-up and one patient dying of non-cardiac causes. Follow-up was 97% complete, and echocardiographic control during the follow-up period revealed competent valves with gradients comparable to those at discharge. Two patients were screened with electron beam tomography (EBT) three years after the operation and there was no sign of wall or leaflet calcification. At the end of the 15 months (mean) follow-up, the functional capacity of the patients had improved significantly (p <0.05). CONCLUSIONS: Our early results suggest that use of the Freestyle valve in conjunction with a Dacron tube graft can be a good alternative for patients over 65 years of age who present with ascending aortic aneurysm with aortic valve insufficiency.

Aged↗

Regression of left ventricular hypertrophy after aortic valve replacement in patients over 55 years old with different valve types.

BACKGROUND: We planned a prospective study to evaluate the regression of left ventricular mass one year after surgery in older patients (<or=55 years) who have undergone aortic valve replacement with stentless bioprostheses or mechanical valve. MATERIAL/METHODS: Between 1998 and 2000, 54 patients had aortic valve replacement with stentless bioprostheses (14 CryoLife-O'Brien, 40 Medtronic Freestyle), and 62 patients had aortic valve replacement with St. Jude Medical mechanical valve. In preoperative echocardiographic evaluation, the St. Jude group had the highest left ventricular mass (LVM). The difference between groups was significant (O'Brien group: 329+/-75 g, Medtronic group: 382+/-116 g, St. Jude group: 445+/-138 g, p=0.006). The same level of statistical significance was achieved when LVM indexes were compared (LVMI; 192+/-39 g/m2, 217+/-65 g/m2, 255+/-78 g/m2, respectively, p=0.008). All the surviving patients were evaluated echocardiographically one year after surgery. RESULTS: Regression of LVM occurred in all patients after aortic valve replacement: 26% in the O'Brien group, 37% in the Medtronic group and 32% in the St. Jude group. The difference between the groups was not significant. LVM and LVMI's were significantly lower when compared with preoperative values, but the degree of regression was not different between groups one year after surgery. CONCLUSIONS: Regression of left ventricular mass after aortic valve replacement is directly related to the preoperative ventricular mass and independent of the valve type in older patients. The choice of prosthesis should be based on patient characteristics.

Aged↗

Results of valve preservation and repair for bicuspid aortic valve insufficiency.

BACKGROUND AND AIM OF THE STUDY: There is increasing interest in aortic valve-sparing and repair techniques for the treatment of aortic insufficiency (AI) and/or root aneurysm. The results of bicuspid aortic valve (BAV) repair at the authors' institution were evaluated. An attempt was made to assess the mode of failure and to identify surgical methods that provide durable repair results. METHODS: Aortic valve repair for BAV was performed in 71 patients (62 men, nine women; mean age 41.5 +/- 13.2 years) between 1993 and 2005. Repair techniques included cusp free margin plication (n = 47), subcommissural annuloplasty (n = 27), free margin reinforcement (n = 10), and cusp triangular resection (n = 7). Thirteen patients had remodeling of one or both aortic sinuses, and 16 had reimplantation of the aortic valve. The ascending aorta and arch were replaced in 29 and five patients, respectively. Concomitant mitral and coronary bypass surgeries were performed in 10 and three patients, respectively. RESULTS: There were no operative deaths. Early postoperative echocardiography revealed no or trace AI in 54 patients and mild AI in 17. There was only one late death which was non-cardiac-related. Eight-year freedom from endocarditis, thromboembolism and anticoagulation-related hemorrhage was 90%, 100% and 100%, respectively. Eight-year freedom from AI grade > or =3+ (moderate) and aortic valve replacement were 44% and 82%, respectively. At the latest follow up, 89% of patients were in NYHA functional class I. Patients who underwent aortic valve-sparing procedures had more stable valve function than those who had cusp repair and subcommissural plication. CONCLUSION: BAV repair is a safe procedure with good early functional results. However, recurrent AI remains a problem at five to eight years of follow up. Since dilation of the aortic root is a common cause of AI and a common feature of patients with BAV, aortic valve-sparing reimplantation operations should provide better long-term outcomes.

Adult↗

Tissue engineering of cardiac valves: re-seeding of acellular porcine aortic valve matrices with human mesenchymal progenitor cells.

BACKGROUND AND AIM OF THE STUDY: Tissue-engineered heart valves have the potential to overcome the limitations of present heart valve replacements. This study investigated the potential for re-seeding an acellular porcine heart valve matrix using human mesenchymal progenitor cells (MPC). METHODS: MPC were isolated from the bone marrow of patients undergoing hip replacement operations. Putative MPC were then cultured in several differentiation media in order to determine the multipotential differentiation capacity of the cells. The MPC were also characterized by FACS analysis. Cells at passage 8 were then seeded at between 1 x 10(4) and 1 x 10(5) cells/cm2 onto a decellularized porcine aortic valve matrix, and recellularization of the matrix was assessed. The phenotype of the re-seeded cells and re-seeded cell density was then determined by histology and immunohistochemistry. RESULTS: Putative MPC were successfully isolated and differentiated into cells of the adipogenic, neurogenic, and myogenic lineages. FACS analysis showed the cells to have a similar phenotype to those isolated by others (CD45-, CD13+, D7FIB+, CD105+, CD10+/-, LNGFR+/-, CD55+, BMP- and AP+/-). Cells seeded onto an acellular valve matrix penetrated the center of the tissue after four weeks to 2% of homograft cell density. Phenotypic analysis of the cells in the re-seeded matrix revealed the cells to have a similar phenotype to native valve interstitial cells (vimentin+, alpha-smooth muscle actin+, heavy chain myosin slow-, desmin-). However, re-seeded cells also expressed osteogenic markers (alkaline phosphatase, osteonectin, and osteopontin). CONCLUSION: This study has shown, for the first time, that human MPC have the capacity to infiltrate an acellular porcine valve matrix under static conditions in vitro. Future studies will comprise culture under pulsatile flow in a physiological heart valve bioreactor to maintain the desired cell phenotype and increase cell density.

Animals↗

A case of transient bioprosthetic valve regurgitation and hemolysis devoloping early after surgery using Carpentier-Edwards valve.

The Carpentier-Edwards pericardial bioprosthesis has been markedly improved in the long-term results and valve-related complications including valve dysfunction, compared to the previous generation bioprosthesis. We report a patient in whom transient prosthetic valve regurgitation and hemolysis occurred early after mitral valve replacement using a Carpentier-Edwards pericardial bioprosthesis and were resolved by preservative therapy. The patient was a 77-year-old female diagnosed with severe mitral valve stenosis and insufficiency. She underwent mitral valve replacement with a Carpentier-Edwards pericardial bioprosthesis. Opening and closing of the three leaflets looked good on intraoperative transesophageal echocardiography (TEE). The only prosthetic valve regurgitation was evident at the central region where the leaflets form coaptation, and no abnormal findings were seen. Serum lactate dehydrogenase (LDH) was decreased to 405 U/l after surgery. However, LDH again began to increase on the 3rd day after surgery and it increased to 1,830 U/l on the 14th day after surgery. Hemolytic urine was detected on 10th day after surgery. PVL was not detected, but moderate abnormal regurgitation from the outside of the stent pocket was detected on TEE. Revision of valve replacement was considered, but LDH thereafter to 393 U/l on 41st day after surgery. The TEE was repeated, and only a trace of central jet was detected without abnormal regurgitation, unlike the previous examination. The patient did not develop any complications thereafter and was discharged on 47th day after surgery. LDH was nearly normal at the time of discharge.

Aged↗

Mitral valve replacement: mechanical versus bioprosthetic valves--a clinical review.

A review of the literature was conducted in an attempt to justify the exclusive use of either mechanical or tissue prostheses in the mitral position. In addition, the University of Toronto experience with mitral valve replacement was reviewed, including a five year follow-up from the Toronto General Hospital. Both studies concluded that there was no significant advantage for the use of either type of valve based upon freedom from thromboembolism, freedom from anticoagulant-related hemorrhage and freedom from all valve-related mortality/morbidity. Tissue valves were shown to be significantly poorer substitutes in terms of freedom from primary valve failure (P less than 0.05) and freedom from reoperation due to valve-related complications (P less than 0.07). The clinical results from the Toronto General Hospital correlated with those reported in the literature and suggested the preferential use of mechanical valves during mitral valve replacement based primarily on their durability and a consequent lesser need for reoperation.

Bioprosthesis↗

[Closed stuck valve diagnosed by echocardiogram immediately after mitral valve replacement: a case report].

The patient was a 52-year-old woman who suffered from mitral valve regurgitation due to torn chordae. Mitral valve replacement (Medtronic-Hall 27 mm) was performed on Jan. 30, 1990. Immediately after the operation cardiac pacing was necessary for bradycardia, but one hour later cardiac rhythm changed to atrial fibrillation and the patient received an injection of verapamil. After the treatment of tachycardia, electro-mechanical dissociation (EMD) appeared on monitor. Bed side M-mode echocardiogram disclosed a restriction of the disc opening, but abnormal structures were not detected by B-mode echocardiogram. By repeated echocardiogram, the disc opening was normally demonstrated on M-mode, but B-mode showed an abnormally high echo structure in the left ventricle just below the prosthetic valve. Under the diagnosis of stuck valve in the closed position due to remnants of chordae, reoperation was performed. An eight mm remnant of chorda was found on the posteromedial side of the posterior leaflet, and it was supposed that the compression of the remnant between the disc and the valve ring restricted the valve opening. The remnant was resected through the large orifice of the Medtronic-Hall valve. After the reoperation, EMD was not detected and prosthetic valve insufficiency was not noted on echocardiogram. The patient left the hospital in a good condition three weeks after MVR.

Echocardiography↗

[An experimental study of the use of fresh aortic valve homograft for the usage of the vena caval valve. Part 1. The evaluation of hemodynamics and cineangiographic study].

The purpose of this study is to develop a vena caval valve using the fresh aortic valve homograft. A preliminary study was performed in six dogs by interposing a cryopreserved aortic valve homograft with sinus Valsalva into SVC. After making the tricuspid regurgitation, the aortic valve homograft was closed by the regurgitant flow in the systolic phase and opened by the venous return in the diastolic phase. The preliminary study showed that the cryopreserved aortic valve homograft with sinus Valsalva was useful as a vena caval valve immediately after the implantation. Fresh aortic valve homografts were implanted in 11 dogs in the same manner. Eighteen pressure studies and cine-angiographies were performed in six dogs on 8 to 165 days after the implantation. Pressure studies showed minimal/small pressure gradients across the implanted homografts. However, cineangiography revealed appearance of regurgitation through the implanted homograft three months later. Thromboembolism was not happened in all dogs at all. Therefore, we concluded that the fresh aortic homograft with sinus Valsalva might be clinically feasible for use as a vena caval valve.

Animals↗

[Results of valve-sparing correction of aortic valve insufficiency].

The risk of valve-related complications and the necessity of anticoagulation in patients with prosthetic valves, has led to new operative techniques in the correction of severe aortic insufficiency. In the last 2 years, 35 patients (mean age 41.3 years, range 10-80 years) with aortic insufficiency underwent reconstructive valves surgery. Eighteen patients had a commissuroplasty with or without triangular resection. In 5 patients with perforation, the valves could be reconstructed with a pericardial patch. In 12 patients with insufficiency due to aortic aneurysm, the valves were resuspended within the aortic prosthesis. In 2 patients the aortic valves were replaced intraoperatively because of unsatisfactory results. The perioperative mortality was 5.7%. The echocardiographic degree of aortic insufficiency decreased from 3.3 +/- 0.5 preoperatively to 0.45 +/- 0.53 postoperatively. Two patients were reoperated within the first week. Five of 23 patients at 1-year follow-up have mild to moderate aortic insufficiency. Mean ventricular dimensions and function at discharge and after 1-year follow-up are normal. With the new operative techniques described recently, valve-sparing corrections of aortic insufficiency are possible in an increasing number of patients, and autologous valve tissue can be saved. With more refinement of surgical technique, early postoperative results will further improve.

Adolescent↗

In vitro comparison of bileaflet aortic heart valve prostheses. St. Jude Medical, CarboMedics, modified Edwards-Duromedics, and Sorin-Bicarbon valves.

The hydrodynamic performance of four currently used bileaflet heart valve prostheses (St. Jude Medical, CarboMedics, modified Edwards-Duromedics, and Sorin-Bicarbon) with a nominal tissue anulus diameter of 27 mm were measured in the aortic position. All experiments were performed in nonpulsatile flow and in an electrohydraulic, computer-controlled pulse duplicator simulating the left side of the human circulatory system. Testing conditions were set at cardiac outputs of 3.0, 4.5, 6.5, and 8.0 L/min at a constant heart rate of 70 beats/min. The Sorin-Bicarbon valve had the lowest pressure difference with regard to nonpulsatile (mean 5.4 mm Hg at 30 L/min) and pulsatile (mean 2.2 mm Hg at 8 L/min) flow, followed by the St. Jude Medical, CarboMedics, and modified Edwards-Duromedics valves. The leakage volumes under static and pulsatile flow conditions were lowest for the modified Edwards-Duromedics and Sorin-Bicarbon valves. The energy loss in pulsatile flow was lowest for the Sorin-Bicarbon valve, mainly because its systolic, closure, and leakage energy losses were low. Systolic sequential velocity profiles showed the most even flow distribution pattern for the St. Jude Medical and Sorin-Bicarbon valves. These findings correspond with lower overall Reynolds shear stress levels for the St. Jude Medical and the Sorin-Bicarbon valves than for the modified Edwards-Duromedics and CarboMedics valves.

Aortic Valve↗

Prosthetic valve endocarditis. The case for prompt valve replacement.

Treatment of patients with prosthetic valve endocarditis with existing guidelines has failed to reduce the over-all mortality rate to below 50 per cent. However, subgroups with high or lower risk of death can be delineated on the basis of risk factors such as early onset following surgery, high-risk causative organisms, cardiodynamic failure, and septic emboli. High-risk patients comprise more than 70 per cent of those with prosthetic valve endocarditis in recent series. Analysis of previously reported series indicates that the mortality rate for high-risk patients with late onset of prosthetic valve endocarditis treated by valve replacement was less than that of patients receiving only medical therapy. We have treated 6 consecutive patients with prosthetic valve endocarditis (3 early onset, 3 late onset) by valve replacement before completion of a course of antibiotics. All patients survived surgery but one patient died after 4 1/2 months of noninfectious causes. Prompt valve replacement is technically feasible and should become the standard therapy for patients with prosthetic valve endocarditis who do not fall into the lower risk group.

Adult↗

Mitral valve replacement with the Hancock stabilized glutaraldehyde valve. Clinical and laboratory evaluation.

From March 1971 through April 1975, one hundred twenty patients underwent mitral valve replacement with a Hancock "stabilized glutaraldehyde process" porcine aortic xenograft. A simultaneous canine experimental series was also carried out. In the clinical series, the early mortality was 8.3%. Actuarial analyses of all patients predicts survival at two years of 81.0% and at four years of 70.0%. The predicted survival for patients without coronary disease or prior prosthetic valve replacement is 87.5% at two years and 77.5% at four years. There were four thromboembolic episodes, a rate of 2.4% per patient-year. None were fatal. No valve failure were noted. Histologic examination and shrink temperature analysis of recovered valves show excellent tissue preservation at 40 months. The data indicate that the Hancock valve is durable, enjoys a low incidence of thromboembolism, and may be the valve of choice for mitral valve replacement.

Adult↗

How to deal with recipients of valves prone to structural failure in the 2000s: Padua experience with the TRI Technologies valve.

BACKGROUND: TRI Technologies (TT) valves evidenced a propensity to structural failure, consisting in fracture of the pivoting system, leading to leaflet escape. At our institution, between 2000 and 2002, 36 TT valves were implanted in 34 patients. Here we report the final results of the Tritech survey program. METHODS: In February 2002, the first valve-related death occurred. After the event, patients were enrolled in the TT valve survey program and strictly followed up. The option of a reintervention was advised to each patient and weighed against the redo operative risk. The prophylactic TT valve replacement program took place in two time frames, dependent on each patient's personal choice: between September 2002 and October 2003 (first phase), and between September 2004 and October 2004 (second phase). Overall, 22 (10 women, 12 men) patients underwent reoperation. Mean time interval between TT valve implantation and replacement was 23 +/- 11 months. Patients' mean age was 59 +/- 11 years (median age, 64 years). RESULTS: All recipients adhering to the program successfully underwent reoperation. Operative mortality was 0%. CONCLUSIONS: We believe that the timing of the second surgery was fundamental for the favorable outcome of each patient and the absence of operative mortality. We are convinced that the tailored programming of the reintervention, together with the strong motivation of each patient, contributed in minimizing the risks related to surgery. The circumscribed cohort of patients involved was compatible with a tailored therapeutic plan. We strongly advise prophylactic reoperation of recipients of TT valves.

Aged↗