Porcine aortic valves as replacements for human heart valves

A most important factor in the durability of porcine aortic valves used as replacements for human heart valves is the use of glutaraldehyde preservation. It appears that such a preparation becomes a nonviable but stable and complex polymer with excellent mechanical properties. Twenty out of 31 formalin-preserved stented porcine aortic valves placed in the aortic and atrioventricular position in 30 patients failed within 4 years due to detachment of one or more commissures, separation of the xenograft aortic valve from the stent, or perforation of one or more leaflets. One hundred thirty-seven stented porcine aortic valves that had been preserved in glutaraldehyde were inserted in the aortic position in 89 patients and in the mitral position in 48 patients. There have been no valve failures within 45 months of follow-up: 51 patients have been followed for more than 30 months, 33 beyond 3 years, and 5 are nearing the 4-year mark.     

Comparative analysis of long-term results with porcine-aortic, bovine pericardial and tilting disc valves

The three series with the first-generation valve prostheses were reviewed for long-term clinical evaluation in isolated aortic and mitral valve replacement. Hancock porcine xenograft was implanted in 71 patients from 1977 to 1979, ionescu-Shiley pericardial xenograft (standard model) in 271 patients from 1979 to 1983, and Bjork-Shiley tilting disc valve in 194 from 1978 to 1986. In aortic position, no any significant difference among three valve types could be demonstrated in the actuarial survival and freedom from thromboembolism and valve infection, while the actuarial freedom from valve dysfunction in lonescu-Shiley valve was significantly lower than that in other two valves. Bj?rk-Shiley valve in mitral position showed satisfactory clinical performance in terms of valve-related complications and survival in comparison with two types of bioprosthetic valves. In our conclusion at present time, Bj?rk-Shiley valve is suitable for the first choice of both aortic and mitral valve prostheses. In case of valve replacement with a bioprosthesis, however, porcine aortic valve is a better choice for aortic, and bovine pericardial valve likely for mitral replacement.     

Late failure of porcine valve heterografts in children.

Heterograft porcine valves have gained wide acceptance in replacement of diseased cardiac valves, and their clinical performance in adults has been very satisfactory over follow-up periods of up to 8 years. Valve replacement in children is relatively infrequent and experience with porcine xenografts is necessarily small. Our combined experience at three university hospitals has been with 25 children, 17 months to 16 years of age, who have been followed for 10 to 54 months (mean follow-up 33 months). Porcine valves were used to replace the aortic valve in nine, the mitral valve in seven, both valves in two, the tricuspid valve in two, and the pulmonary valve in five patients. Severe bioprosthetic valve dysfunction has occurred in five (20%) of these patients so far and necessitated replacement because of severe stenosis in mitral (two) or aortic (three) valve prostheses at 18 to 45 months after implantation; one postoperative death occurred among the five reoperations. Pathological examination showed extensive fragmentation of collagen with focal heavy calcification and degeneration. In addition we have encountered deterioration and calcification of two porcine valves in 23 valved conduits followed for 12 to 70 months (mean 43 months), requiring removal and replacement of the valves 65 and 67 months after implantation. This experience indicates a disquietingly high incidence of relatively early failure of porcine xenograft valves in children. This is significantly higher than the failure rate observed in adult patients. The failure rate is not consistently related to the small size of an implanted valve which becomes relatively narrow with the growth of the patient, leading to excessive turbulence and trauma to the prosthesis. Other factors, including increased turnover of calcium and accelerated rejection in growing children, may contribute to these failures and should be examined in order to improve long-term results. A satisfactory performance would make heterografts the ideal valvular prosthesis in children, since anticoagulation is avoided.     

Aortic Valve Replacement with Stentless Porcine Bioprostheses

The implantation of stentless porcine valves (SPVs) is technically more demanding than implantation of stented bioprosthetic valves. Implantation of the Toronto SPV bioprosthesis requires an,understanding of the relationships between the leaflets and the aortic annulus and sinotubular junction. In addition to proper alignment of the three commissures within the aortic root, the diameter of sinotubular junction should not exceed the external diameter of the porcine aortic valve after completion of the operation. The Medtronic Freestyle porcine aortic root bioprosthesis can be used for subcoronary implantation as well as for aortic root replacement. Degenerative calcification of a tricuspid aortic valve is the most common cause of aortic valve disease in older patients. Implantation of stentless valves in the subcoronary position is usually feasible because the geometry of the aortic root is well maintained in these patients. The bicuspid aortic valve is the second most common cause of aortic valve disease in older patients and the most common in younger patients. These patients frequently have dilated aortic root, and the Medtronic Freestyle bioprosthesis is ideal for implantation using the root inclusion technique. Stentless porcine bioprostheses are minimally obstructive and associated with low mean systolic gradients. In addition, they have better hemodynamic performance during exercise than stented bioprostheses. For these reasons, patient-prosthesis mismatch has not been described with stentless valves. Left ventricular function after aortic valve replacement appears to be better with stentless than with stented bioprostheses. Comparative, nonrandomized studies of aortic valve replacement with stented and stentless valves suggest that the risk of cardiac death is reduced with stentless valves and the rates of valve-related complications also appear to be lower. What remains unknown is whether stentless valves are more durable than stented ones.     

Mitral Valve Replacement with Dura Mater Bioprostheses

Dura mater bioprostheses for cardiac valve replacement were first introduced in Brazil. They have been used since 1975 at the National Heart Hospital, London, as a mitral valve replacement instead of fascia lata valves or inverted aortic homograft valves. During this period 120 patients have had dura mater valves inserted in the mitral position; 29 also received an aortic valve replacement, 6 with dura mater, 20 with an aortic homograft, 2 with an aortic xeno-graft and 1 with a prosthetic valve. Perivalvular leaks occurred with seven of these mitral valves, and another seven presented with detached cusps. All but one of these 14 valves were replaced. Emboli have occurred in four of the patients, one of whom died after 35 months with thrombus on the aortic valve, but with an unaffected mitral valve. There were 15 early deaths, a hospital mortality of 12.5%. and 10 late deaths, a postoperative mortality of 9.5%. Actuarial analysis has shown a four-year postoperative survival of 78.970.     

Homologous dura mater cardiac valves. Study of 533 surgical cases.

A group of 533 patients had cardiac valves replaced with homologous dura mater valves. The dura mater was preserved in a solution of 98 per cent glycerol and antibiotics for a period of 12 days before used. The leaflets were mounted in a stainless steel ring covered by Dacron velour. Two hundred forty-five patients had mitral valve replacement; 205 patients, aortic valve replacement; 17 patients, tricuspid valve replacement; and 2 patients, pulmonary valve replacement. Sixty-four patients were subjected to multivalvular replacements. The patients were followed for a period of 1 to 40 months after surgery with satisfactory clinical and hemodynamic results. Because 2 patients developed endocarditis produced by fungii, fungicidal drugs were added to the preservative solution. No bacterial endocarditis has been observed. No pressure gradient through the valve has been noted at rest. Anticoagulant drugs have not been used in the postoperative period.     

Failure of Hancock xenograft valve: importance of valve position (4- to 9-year follow-up)

To evaluate long-term durability of Hancock valves, we reviewed our results in 107 hospital survivors (120 valves) who were operated on during 1974 through mid-1979. Mitral valve replacement was done in 63 patients, aortic valve replacement in 20, and mitral valve replacement combined with other procedures in 24. The 7-year survival was 84 +/- 4% (standard error of the mean) for 91 patients and 97 valves. During a follow-up of 590 patient-years, 15 (12 mitral and 3 aortic) of 120 valves at risk (87 mitral, 32 aortic, 1 tricuspid) were removed from 14 patients. Six valves (3 mitral and 3 aortic) were removed because of bacterial endocarditis. One mitral valve was removed because of thromboembolism. Eight mitral valves were removed because of valve structural failure, which occurred at a mean follow-up of 42 months. These valves showed extensive calcification, leaflet perforation, or cusp tear. Structural failure was unrelated to valve size, year of implantation, or valve shelf-life. Structural failure was not seen after aortic valve replacement. Results show that structural failure of the Hancock xenograft valve in the mitral position is related primarily to valve position. After aortic valve replacement, valve failure is predominantly due to endocarditis. Although medium-term (mean, 6-year) durability of this xenograft valve compares satisfactorily with prosthetic valves, its high failure rate in the mitral position indicates the necessity for improvement in valve mounting, design, and preservation.     

Transpecies heart valve transplant: advanced studies of a bioengineered xeno-autograft

Background. Tissue engineering approaches utilizing biomechanically suitable cell-conductive matrixes should extend xenograft heart valve performance, durability, and growth potential to an extent presently attained only by the pulmonary autograft. To test this hypothesis, we developed an acellular, unfixed porcine aortic valve-based construct. The performance of this valve has been evaluated in vitro under simulated aortic conditions, as a pulmonary valve replacement in sheep, and in aortic and pulmonary valve replacement in humans.

Methods. SynerGraft porcine heart valves (CryoLife Inc, Kennesaw, GA) were constructed from porcine noncoronary aortic valve cusp units consisting of aorta, noncoronary aortic leaflet, and attached anterior mitral leaflet (AML). After treatment to remove all histologically demonstrable leaflet cells and substantially reduce porcine cell-related immunoreactivity, three valve cusps were matched and sewn to form a symmetrical root utilizing the AML remnants as the inflow conduit. SynerGraft valves were evaluated by in vitro hydrodynamics, and by in vivo implants in the right ventricular outflow tract of weanling sheep for up to 336 days. Cryopreserved allograft valves served as control valves in both in vitro and in vivo evaluations. Valves were also implanted as aortic valve replacements in humans.

Results. In vitro pulsatile flow testing of the SynerGraft porcine valves demonstrated excellent valve function with large effective orifice areas and low gradients equivalent to a normal human aortic valve. Implants in sheep right ventricular outflow tracts showed stable leaflets with up to 80% of matrix recellularization with host fibroblasts and/or myofibroblasts, and with no leaflet calcification over 150 days, and minimal deposition at 336 days. Echocardiography studies showed normal hemodynamic performance during the implantation period. The human implants have proven functional for over 9 months.

Conclusions. A unique heart valve construct has been engineered to achieve the equivalent of an autograft. Short-term durability of these novel implants demonstrates for the first time the possibility of an engineered autograft.     

The Ionescu-Shiley valve: a solution for the small aortic root

Valve replacement in patients with a small aortic anulus can cause difficult technical problems or leave the patient with a significant residual transvalvular gradient. Between August, 1977, and June, 1983, 35 patients with a small aortic root (21 mm or less) underwent aortic valve replacement with Ionescu-Shiley pericardial xenograft valves. They ranged in age from 29 to 76 years (mean 52.8 years) and in weight from 64 to 91 kg (mean 76.3 +/- 3.6 kg). Preoperatively, 26 patients were in New York Heart Association Functional Class III-IV. The valve sizes used were 17 mm in three cases, 19 mm in 16 cases, and 21 mm in 16 cases. There were four hospital deaths (11.4%) resulting from sepsis or low cardiac output. There were no late deaths. Cumulative duration of follow-up was 819.4 patient-months. Twenty-four (78%) of the 31 surviving patients are asymptomatic. Up to the time of review, there have been no episodes of thromboembolism, infective endocarditis, perivalvular leak, valve thrombosis, or primary tissue valve failure. Fifteen patients were hemodynamically evaluated 2 to 47 months (mean 14.3 months) after operation. The average resting transvalvular gradients for 19 and 21 mm valves were 15.1 and 10.8 mm Hg, respectively. Our experience suggests that the Ionescu-Shiley pericardial xenograft valve is a valid alternative in the surgical treatment of patients with a small aortic root.     

Valve Replacement with the Starr-Edwards and Hancock Prostheses: Comparative Analysis of Late Morbidity and Mortality

Although the Starr-Edwards caged-ball valve remains a standard of comparison for more recently introduced prostheses, a substantial incidence of thromboembolic and hemorrhagic complications prompted our evaluation of the Hancock glutaraldehyde-fixed porcine xenograft. We have compared the results of 435 aortic valve replacements using the Starr- Edwards valve (SE-AVR), 515 mitral valve replacements (SE-MVR), and 121 double-valve replacements (SE-AVRMVR) with 251 aortic valve replacements using the xenograft aortic valve (X-AVR), 338 mitral valve replacements (X-MVR), and 88 double-valve replacements (X-AVR-MVR). The Starr- Edwards valves were used during the period 1963 through 1973 and the xenograft valves between 1971 and 1976. No significant differences in patient age, sex, or preoperative hemodynamic data were noted between comparable groups. All patients with Starr-Edwards valves received long-term anticoagulation while anticoagulants were used only for specific indications in patients with xenograft valves. Total follow up was 3944 patient years for the Starr-Edwards patients and 947 patient years for the xenograft patients. Hospital mortality was not significantly different for comparable groups: SE-AVR 6.9% vs. X-AVR 6.4%, SE-MVR 9.7% vs X-MVR 8.6%, and SE-AVR-MVR 7.5% vs. X-AVR-MVR 10.2%. Linearized mortality and morbidity data expressed as percent per patient- year are tabulated below. Pairs which differ significantly (p < .05) are italicized.     

Stentless porcine and pericardial valve in aortic position.

Fifty-seven patients underwent aortic valve replacement with a stentless glutaraldehyde-fixed bioprosthesis; 27 received a porcine aortic valve and 30 had a bovine pericardial valve. Two groups of 30 patients each who had aortic valve replacement with a tilting-disc mechanical valve or a stented porcine bioprosthesis served as controls. There were no differences in sex, body surface area, valve lesion, and valve size among the four groups. Results were assessed on a Doppler-based determination of maximum velocity across the valve, aortic valve area, and degree of valve regurgitation. Velocity across the valve was significantly less with stentless pericardial valves than with stentless porcine valves, stented bioprostheses, and mechanical valves. Stentless valves had a significantly larger aortic valve area when compared with stented valves. Mild central aortic insufficiency was detected more often with stentless pericardial than with stentless porcine bioprostheses (p = 0.04). Stentless valves showed a higher incidence of complete atrioventricular block when compared with stented valves (p = 0.04). Long-term studies are now warranted to assess the durability of both types of stentless valves.     

The Hancock pericardial xenograft: incidence of early mechanical failures at a medium-term follow-up

The Hancock pericardial xenograft has been used in our Institution since August 1981 as an alternative to porcine bioprostheses. Up to July 1984, 97 Hancock pericardial xenografts have been implanted in 84 patients; of 76 operative survivors with a mean age of 55.2±13 years (range 13–75 years), 50 had undergone aortic valve replacement, 16 mitral valve replacement and 10 mitral-aortic valve replacement. Follow-up ranged from 0.5 to 5.2 years with a cumulative duration of 239 patient/years and is 99% complete. Actuarial survival is 92%±4% for patients with aortic valve replacement and 84%±10% for patients with mitral valve replacement at 5 years, and 77%±14% for those with mitral-aortic valve replacement at 4 years. Thromboembolic episodes occurred in 2 patients (1 after aortic and 1 after mitral valve replacement). The actuarial freedom from emboli is 100% for patients with mitral-aortic valve replacement at 4 years, and 96%±3% for patients with aortic and 93%±6% for patients with mitral valve replacement at 5 years. Reoperation was performed in 13 patients (9 aortic, 2 mitral and 2 mitral-aortic valve replacements), because of endocarditis in 3 (2 aortic and 1 mitral valve replacement), paravalvular leak in 1 (aortic valve replacement), and primary tissue failure in 9 (6 aortic, 1 mitral and 2 mitral-aortic valve replacements). Actuarial freedom from primary tissue failure is 72%±9% for aortic and 83%±8% for mitral Hancock pericardial xenografts at 5 years. Eleven xenografts explanted because of primary tissue failure were studied pathologically. All showed commissural tears with gross regurgitation; calcium deposits were severe in 2, mild but unrelated to the tears in 2 and absent in 7. Collagen disarray was observed at the site of cusp rupture while the collagen was well preserved in the intact areas of the leaflets. Our results show that: 1) Hancock pericardial xenografts have a high rate of early primary tissue failure, 2) primary tissue failure is caused by cusp rupture at the commissures and can be considered fatigue-induced, 3) tissue calcification does not influence the durability of pericardial xenografts which do not represent a valid alternative to porcine bioprostheses.     

Cardiac valve replacement in children: comparison of tissue with mechanical prostheses

Replacement of cardiac valves in children has been associated with high rates of mortality and morbidity in the past. We have compared 24 children from 2 to 18 years of age who have received mechanical valves with 24 children who have received porcine valves. The groups were similar except that (1) there were more mitral operations in the mechanical valve group and more aortic operations in the porcine valve group; (2) more porcine than mechanical valves were implanted in recent years; and (3) the porcine valve group comprised more young patients under 8 years and required more complex operations. Early and late mortality rates were higher in the mechanical than in the porcine valve group. Major late complications were seen in 50 percent of the mechanical valve group and 13 percent of the porcine group. Implantation of an adult-sized aortic valve was made possible in all patients by the use of aortic augmentation annuloplasty. Higher operative mortality rates in the mechanical valve group may have been related more to technique of myocardial preservation during operation than to type of valve. Although differing rates of late morbidity and mortality may also have been related to myocardial preservation and other technical factors, the type of valve used seemed to be an important determinant of the better results in the porcine group. Despite unknown durability of the porcine valve, our data suggest that the safest prosthetic valve to use in children at this time is the glutaraldehyde-fixed porcine prosthesis.     

Left ventricular mass reduction after aortic valve replacement: homografts, stentless and stented valves.

BACKGROUND: We studied the effect of four different types of prosthetic aortic valves on time course and extent of regression of left ventricular hypertrophy after aortic valve replacement for aortic stenosis. METHODS: Four groups of 10 patients each were randomly assigned to receive: (1) aortic homograft preserved in antibiotic solution at 4 degrees C, (2) Toronto stentless porcine valve, (3) Medtronic Freestyle stentless valve, or (4) Medtronic Intact aortic valve. The left ventricular mass index, effective orifice area index, and peak and mean transaortic gradients were measured by Doppler echocardiography before the operation and 8 months postoperatively. RESULTS: The hemodynamic performance indices were much better for the homograft and stentless valves than for the stented one. The absolute left ventricular mass index reduction was greater in the homograft group compared with the Intact (p = 0.0004) and Toronto (p = 0.007) groups. The extent of percent left ventricular mass index reduction was greater only in the homograft group versus Intact group (p = 0.005). The multilinear regression analysis showed that the only predictors of a larger percentage of left ventricular mass index reduction were the homograft type, a higher valve size index, and a higher preoperative left ventricular mass index. CONCLUSIONS: When a stentless or homograft aortic valve was used instead of a stented valve to replace a stenotic aortic valve there was more complete or at least faster regression of left ventricular hypertrophy. The hemodynamic performance of stentless porcine valves was similar to that of aortic homografts, nevertheless the aortic homografts preserved in antibiotic solution offered a faster regression of left ventricular hypertrophy during the same period of time.     

An eight-year experience with porcine bioprosthetic cardiac valves

A total of 589 porcine bioprostheses were implanted in 509 patients from January, 1976, through December, 1983. Of the valves implanted, 390 were Hancock and 199 were Carpentier-Edwards. A total of 1,633 patient-years was accrued, with a mean follow-up of 38 months per patient. Two hundred eight patients had aortic valve replacement, 209 had mitral valve replacement, and 79 had multiple valve replacements, of which 46 were aortic and mitral replacements. The mortality for isolated aortic valve replacement was 5.8%; for isolated mitral replacement, 8.6%, and for all patients, 10.9%. Late mortality was 3.9% per patient-year. The actuarial survival rate at 5 years was 79% for aortic, 68% for mitral, and 76% for aortic-mitral valve replacement. There were 12 thromboembolic events (0.73% per patient-year). Two episodes occurred in patients with an aortic bioprosthesis, nine in patients with a porcine mitral valve, and one in a patient with mitral and tricuspid bioprosthetic valves. The probability of remaining free of thromboembolism at 5 years was 99% for the group having aortic valve replacement, 93% for those having mitral replacement, and 100% for the group having aortic-mitral valve replacements. Thirteen episodes of endocarditis occurred (0.8% per patient-year). Seven of the 13 patients died as a direct result of endocarditis. The probability of remaining free of prosthetic endocarditis at 5 years was 97% for the aortic valve replacement group, 95% for the mitral group, and 97% for the aortic-mitral group. There were 20 instances of xenograft failure (1.2% per patient-year). The probability of remaining free of valve failure at 5 years was 96% for the aortic valve replacement group, 93% for the mitral group, and 93% for the aortic-mitral replacement group. Primary tissue failure of a prosthesis occurred in seven patients, all with Hancock valves (0.43% per patient-year). As yet there has been no primary tissue failure of the Carpentier-Edwards prosthesis. There also appears to be a lower incidence of thromboembolism (Edwards, 0.3% per patient-year; Hancock, 0.8% per patient-year) and endocarditis (Edwards, 0.6% per patient-year; Hancock, 1.0% per patient-year). The low incidence of complications with the porcine bioprosthetic valve, especially the Carpentier-Edwards, encourages us to recommend its continued use, especially in situations in which anticoagulation is contraindicated.     

Clinical experience with a porcine aortic valve xenograft for mitral valve replacement

Between March, 1971, and July, 1973, 103 patients underwent mitral valve replacement with a glutaraldehyde-preserved porcine aortic valve mounted on a flexible polypropylene, Dacron-covered stent. Overall operative survival was 95.1%. Actuarial analysis of late postoperative results indicates 92% survival through 2 years, with functional improvement in nearly all patients. The rate of systemic thromboembolism has been approximately 1.7% per patient-year without anticoagulants. No valve failure has occurred. We conclude that this xenograft prosthesis provides a technically and functionally satisfactory valve substitute, the durability of which appears to significantly exceed that of previously available tissue valves for mitral replacement.     

The porcine bioprosthesis. A review of 1,000 consecutive patients undergoing cardiac valve replacement

Early and late experience with 1,000 patients undergoing porcine xenograft replacement of cardiac valves from 1974 through 1981 at Emory University Hospital is presented. Hemodynamic performance of the modified orifice Hancock and the Carpentier-Edwards valves has been quite satisfactory. There has been a low incidence of thromboembolism in the absence of routine anticoagulation. Less than 20 per cent of our patients are anticoagulated long-term, the primary indication being chronic artrial fibrillation. Endocarditis has developed in 0.7 per cent of patients, an incidence comparing most favorably with that of mechanical prostheses. Valve dysfunction secondary to primary tissue failure is a definite problem. The highest incidence of tissue failure occurred in young patients after six years of implantation. Detailed analysis of long-term patient survival showed a low incidence of valve related deaths. The porcine xenograft is a satisfactory prosthesis for cardiac valve replacement. Our data suggests its use should be limited to older patients or to patients in whom anticoagulation is contraindicated. It should be explained to all patients that long-term durability is unknown and that re-replacement of these bioprostheses within a decade is quite likely.     

Prosthetic valve endocarditis: complication following cardiac surgery

Prosthetic valve endocarditis (PVE) is a rare but serious complication following valve replacement surgery. Early-phase PVE, which occurs within 60 days of valve replacement, may be associated with nosocomial or intraoperative infection. The primary organism of this type is the Staphylococcus group. Late-phase PVE, which usually occurs more than one year after valve replacement, may be caused by a mechanism similar to that of native valve endocarditis. The primary causative organism of this type would thus be similar to that of native valve endocarditis, which is the Streptococcus group. To treat PVE effectively, it is extremely important to identify the primary causative organism. If uncontrollable cardiac failure or infection occurs, a second valve replacement is absolutely indicated. A cryopreserved aortic valve allograft, if available, is the first choice for PVE. Features such as cell viability, less compliance mismatch, and postantibiotic process could be reasons for the anti-infective characteristics of cryopreserved allografts. Currently, allograft valves are not widely available in Japan; therefore, conventional prosthetic valves are usually used. The use of antibiotic-soaked prosthetic valves or stentless xenograft valves has also been attempted. A genetic or tissue engineering approach could open a new era to overcome this lethal complication.     

Long-term experience with porcine aortic valve xenografts

Between 1971 and 1975, glutaraldehyde-preserved porcine aortic valve xenografts were employed for isolated replacement of the mitral valve (MVR) in 243 patients, replacement of the aortic valve (AVR) in 167 patients, and double valve replacement (AVR and MVR) in 51 patients. Postoperatively, long-term anticoagulation was not routinely given. Operative mortality rates for AVR, MVR, and double valve groups were 7.8, 6.0, and 11.8 per cent, respectively; the majority of early postoperative deaths were associated with concomitant coronary artery disease. No death was attributable to xenograft dysfunction. Follow-up of all patients was obtained. The total duration of follow-up for the MVR group was 347 patient-years, for the AVR GROUP 148 148 patient-years, and for double valve replacement 37 patient-years; maximum follow-up for these three groups was 4.4, 4.0, and 2.4 years, respectively. Actuarial analysis of postoperative survival rates at a common interval of 3 years showed 78 per cent for MVR patients, 91 per cent for AVR patients, and 80 per cent (projected) for patients with double valve replacement (85, 96, and 91 per cent for operative survivors, respectively. At this same interval 92 per cent of MVR patients, 99 per cent of AVR patients, and 93 per cent (projected) of patients with double valve replacement were free of thromboembolic episodes. Altogether, 12 of the total 512 valves implanted exhibited some evidence of dysfunction during the entire period of follow-up evaluation, but in only 2 instances (both mitral) was intrinsic pathological involvement of the xenograft tissue documented. Actuarial analysis of xenograft dysfunction at a common interval of 3 years after operation showed 95 per cent of MVR patients, 98 per cent of AVR patients, and 97 per cent (projected) of patients with double valve replacement to be free of this complication. These data support the use of glutaraldehyde-preserved porcine xenografts as superior bioprostheses that pose a low risk of thromboembolism without anticoagulation. The over-all durability of such valves, within the restriction of a maximum current follow-up interval of 4.4 years, appears comparable to that of currently available mechanical prostheses and justifies continued clinical use.     

In vivo hemodynamic comparison of porcine and pericardial valves

The bovine pericardial valve and the SupraAnnular valve have been developed to improve the hemodynamic function of tissue valves. Hemodynamic performances of the standard Carpentier-Edwards porcine valve, the Carpentier-Edwards SupraAnnular valve, and the Carpentier-Edwards bovine pericardial valve were compared in the aortic position. One hundred patients undergoing aortic valve replacement were studied intraoperatively. Mean gradient across the valve decreased for standard and pericardial valves as valve size increased. At the same flow rate, the 23 mm pericardial valve had larger valve orifice areas, higher performance indices, and lower gradients than the 23 mm SupraAnnular valve. The SupraAnnular valve is hemodynamically superior to the standard Carpentier-Edwards porcine bioprosthesis. The Carpentier-Edwards pericardial valve, however, is less obstructive in the aortic position than either of the porcine valves.