Hancock Porcine Xenograft Research Articles

A 20-year experience with the Hancock porcine xenograft in the elderly

Background. The availability of 20 years of follow-up data on the Hancock porcine valve (Medtronic Inc, Irvine, CA) allows determination of long-term actual and actuarial failure rates in the elderly. Methods. We analyzed outcomes after mitral or aortic valve replacement with the Hancock porcine valve in 491 consecutive patients, comparing actual and actuarial valve failure rates in the elderly (age 65 or older) with those in younger patients. Results. The average age of aortic valve replacement recipients was 68 ± 14 years (N = 243) and of mitral valve replacement recipients, 64 ± 12 years (N = 248). Average follow-up was 7.0 years (1,673 patient-years) for aortic valve replacement and 7.3 years (1,781 patient years) for mitral valve replacement recipients. The median time to reoperation or structural failure was 15.9 years for aortic valve replacement patients and 14.3 years for mitral valve replacement patients. However, few elderly patients survived to 15 years (22% of the elderly aortic valve replacement and 13% of the older mitral valve replacement patients). The 15-year actual reoperation rate was therefore only 10% in the elderly aortic valve replacement compared to 30% in the younger aortic valve replacement patients. For mitral valve replacement, the 15-year actual reoperation rate was 11% in the elderly and 36% in the younger patients. The lifetime reoperation risk (the maximum potential number of patients who might ever undergo reoperation during their lifetime) is the sum of actual survival and actual reoperation rates. The lifetime reoperation risk was 20% or less for elderly aortic valve replacement patients and 18% or less for elderly mitral valve replacement patients. Conclusion. These data suggest that about 1 in 10 elderly patients (65 years or older) receiving a Hancock valve will require reoperation within 15 years and less than one in five will ever require reoperation in their lifetimes.

CHOOSING A PROSTHETIC HEART VALVE

Although most of the available prosthetic heart valves function remarkably well, the variety of available choices attests to the inability of any single one to fulfill the requirements of the ideal valve substitute. The mechanical prostheses include the caged-ball, tilting-disc, and bileaflet valves. Tissue valves available in the United States are the Carpentier-Edwards and Hancock porcine heterograft valves and the Carpentier-Edwards pericardial valve. Review of several large comparative studies on valve performance reveals that the overall results with tissue and mechanical valves are about equal at the end of 10 years. The characteristics of each type of valve substitute dictate the selection of one prosthesis in preference to others for a particular patient. Mechanical prostheses are recommended for patients without contraindications for anticoagulants. Tissue valves are reserved for patients over 65 years of age or for patients in whom anticoagulation is contraindicated. Multiple other patient-related factors need to be considered in selecting the appropriate valve, including the psychosocial situation and patient preference.

Hemodynamic evaluation of small-size aortic prostheses

Surgeons are presently able to choose from a variety of satisfactory valve prostheses, depending on the individual situation. The durability, thromboembolic potential, and hemodynamic properties of any valve must be balanced against specific anatomic and clinical factors. Thus, if a surgeon is most concerned about durability, he might choose the bare strut Starr-Edwards ball valve or the Smeloff-Cutter valve, the most proven valves by length of service. However, the Bjork-Shiley, Lillehei-Kaster, and Hancock valves all have good durability records to seven years.Thromboembolic potential is markedly decreased with tissue valves such as the Hancock porcine xenograft, Carpentier-Edwards porcine xenograft, Ionescu-Shiley pericardial valve, or dura mater valve. Patients with these valves do not usually require chronic anticoagulation, which is associated with significant morbidity and mortality. In clinical situations that contraindicate long-term anticoagulation or when the threat of thromboembolism or bleeding is very high, the use of a tissue valve is particularly indicated.Hemodynamic considerations may be paramount in some patients with restrictive anatomy; the small diameter, tilting disc valves have the best hemodynamic performance, although new modifications in the Hancock porcine heterograft may reduce the hemodynamic obstruction in these small diameter valves and allow their implantation without long-term anticoagulation.A number of durable and effective devices exist today for valve replacement, and the type of valve used can be individualized according to the valve characteristics, clinical indications, and anatomic considerations.

Determinants of the occurrence of and survival from prosthetic valve endocarditis: Experience of the Veterans Affairs Cooperative Study on Valvular Heart Disease

For the determination of the risk factors associated with the development of and death caused by prosthetic valve endocarditis, data were reviewed from 66 patients who were prospectively entered into the Veterans Affairs Cooperative Study on Valvular Heart Disease and in whom prosthetic valve endocarditis subsequently developed. Data were recorded at 13 medical centers between October 1977 and September 1982 in patients randomized to receive a mechanical valve (Björk-Shiley spherical disc, n = 510 patients) or a bioprosthetic valve (Hancock porcine heterograft, n = 522 patients). The average rate of prosthetic valve endocarditis development was 0.8% per year over an average follow-up period of 7.7 years. Of the 66 patients in whom prosthetic valve endocarditis developed (5.8%), 15 cases occurred within 2 months of operation (early) and 51 occurred after operation (late). The most significant preoperative predictor of prosthetic valve endocarditis was active endocarditis at the time of operation (7.4% versus 0.9%) (p = 0.001). Early prosthetic valve endocarditis occurred more frequently in patients who underwent operation for multivalvular disease (p = 0.023). Significantly related perioperative variables were coma, prolonged mechanical ventilation, deep postoperative wound infection, postoperative jaundice, ventricular tachycardia, ventricular fibrillation, and replacement of more than one valve (p < 0.05). Multivariate predictors were hypoxia (p = 0.001), preoperative endocarditis (p = 0.003), preoperative valve lesion (p = 0.020), and resident surgeon (p = 0.05). Significant preoperative variables predictive of late prosthetic valve endocarditis were mitral stenosis and mixed mitral stenosis-regurgitation. The only multivariate predictor of late prosthetic valve endocarditis was superficial wound infection (p = 0.004). Of deaths attributable to prosthetic valve endocarditis, 41% occurred in patients treated with antibiotics alone, 48% occurred in patients treated with surgical intervention and antibiotics, and death resulted in both patients who received no treatment. No difference was found in the risk of early or late postoperative prosthetic valve endocarditis developing in patients receiving the mechanical valve versus those receiving the bioprosthetic valve. (J THORAC CARDIOVASC SURG 1994;108;207-14)

Determinants of the occurrence of and survival from prosthetic valve endocarditis

Abstract For the determination of the risk factors associated with the development of and death caused by prosthetic valve endocarditis, data were reviewed from 66 patients who were prospectively entered into the Veterans Affairs Cooperative Study on Valvular Heart Disease and in whom prosthetic valve endocarditis subsequently developed. Data were recorded at 13 medical centers between October 1977 and September 1982 in patients randomized to receive a mechanical valve (Bjork-Shiley spherical disc, n = 510 patients) or a bioprosthetic valve (Hancock porcine heterograft, n = 522 patients). The average rate of prosthetic valve endocarditis development was 0.8% per year over an average follow-up period of 7.7 years. Of the 66 patients in whom prosthetic valve endocarditis developed (5.8%), 15 cases occurred within 2 months of operation (early) and 51 occurred after operation (late). The most significant preoperative predictor of prosthetic valve endocarditis was active endocarditis at the time of operation (7.4% versus 0.9%) ( p = 0.001). Early prosthetic valve endocarditis occurred more frequently in patients who underwent operation for multivalvular disease ( p = 0.023). Significantly related perioperative variables were coma, prolonged mechanical ventilation, deep postoperative wound infection, postoperative jaundice, ventricular tachycardia, ventricular fibrillation, and replacement of more than one valve ( p p = 0.001), preoperative endocarditis ( p = 0.003), preoperative valve lesion ( p = 0.020), and resident surgeon ( p = 0.05). Significant preoperative variables predictive of late prosthetic valve endocarditis were mitral stenosis and mixed mitral stenosis-regurgitation. The only multivariate predictor of late prosthetic valve endocarditis was superficial wound infection ( p = 0.004). Of deaths attributable to prosthetic valve endocarditis, 41% occurred in patients treated with antibiotics alone, 48% occurred in patients treated with surgical intervention and antibiotics, and death resulted in both patients who received no treatment. No difference was found in the risk of early or late postoperative prosthetic valve endocarditis developing in patients receiving the mechanical valve versus those receiving the bioprosthetic valve. (J THORAC CARDIOVASC SURG 1994;108;207-14)

Atrioventricular valve replacement with a Hancock porcine xenograft

The Hancock porcine xenograft valve was the first commercially prepared, quality-controlled tissue valve. The National Institutes of Health group began implantation of this valve in 1970 and reported on the first 5 years of their results, which was one of the longest follow-ups of that valve at that particular time. Since then there have been a number of centers that have had long-term experience with thousands of these valves, In retrospect, it is now clear that some of the conclusions made by the National Institutes of Health group have not come to pass, such as this valve being the “valve of choice” for all patients. “Valve of choice” is a relative term and may be one valve for one patient and another valve for another patient. This report was important in bringing together some of the first medium-term data and pointing out that, even in this valve, there was some small degree of thromboembolism. The paper also provided a historical look at the methods of data analysis that were in use in the early 1970s compared with those now used in 1991. Actuarial curves were not yet commonly used, nor were percent/patient-year linearized results. Valve types were mixed as well. Hemodynamic data, always a strong point of National Institutes of Health data analysis, were excellent. The use of this valve became a fairly standard device and has been retrospectively analyzed by a number of centers, suggesting that now it is better used in the older patient or in patients who cannot take warfarin sodium. It is a 10- to 15-year valve, less effective in terms of durability in the mitral position than in the aortic. Data still support the original premise that in the patient in sinus rhythm this is an excellent valve replacement device to minimize thromboembolic complications without the benefit of anticoagulation after valve replacement.

Influence of prosthetic design on durability of the liotta porcine valve in the mitral position

From March 1979 to December 1984, the Liotta low-profile porcine bioprosthesis was employed for mitral valve replacement in 71 patients to avoid potential left ventricle-prosthesis mismatch occasionally observed with the standard, high-profile, Hancock porcine xenograft. Follow-up of 61 operative survivors showed at 10 years an actuarial survival of 67% ± 7%, freedom from thromboemboli of 96% ± 2%, freedom from structural deterioration of 63% ± 11% and freedom from all Liotta bioprosthesis-related complications of 53% ± 10%. Complications related to excessive protrusion of the stent into the left ventricular cavity were eliminated with the Liotta bioprosthesis; the peculiar stent configuration, however, was responsible for an increased rate of structural deterioration requiring reoperation in 10 patients (2.8% ± 0.9%/patient-year) at a mean interval of 76 ± 18 months after mitral valve replacement (range, 45 to 106 months). Common findings in all expiants were cusp prolapse, cusp tears, and commissural rupture related to various degrees of tissue calcification, constantly leading to severe prosthetic incompetence. As also shown experimentally, such structural changes have been attributed to increased systolic stresses on the closed cusps, favored by excessive reduction of the stent height. Our experience shows that the Liotta bioprosthesis used for mitral valve replacement does not provide any clear-cut advantage over standard porcine bioprostheses and that its long-term durability appears affected by the unique prosthetic design.

13 ブタ大動脈弁の長期遠隔成績

13 ブタ大動脈弁の長期遠隔成績

Six month postoperative hemodynamics of the Hancock heterograft and the Björk-Shiley prosthesis: Results of a Veterans Administration Cooperative prospective randomized trial

In a Veterans Administration Cooperative Study involving 13 medical centers, 575 patients undergoing single valve replacement were prospectively randomized to receive either the standard Björk-Shiley prosthesis or the Hancock porcine heterograft (with a modified orifice for sizes 23 and smaller). The hemodynamic data in the 268 patients who underwent cardiac catheterization an average of 6 months (range 3 to 12) postoperatively are reported. Statistical analyses were performed on valve sizes 23, 25 and 27 in the aortic position, and 29, 31 and 33 in the mitral position.A wide variation was observed in mean pressure gradient and calculated orifice area in both valve types within all sizes in both the aortic and the mitral positions. In the aortic position, the Björk-Shiley prosthesis tended to have a lower pressure gradient and larger calculated orifice area than the Hancock heterograft, but the differences in gradient between the two valve types were significant only in the larger-sized valves. The difference in calculated area between the two valve types was not significant within each valve size. In the mitral position, there were no differences in gradient and calculated orifice area between the two types of prostheses.The postoperative cardiac index, regurgitant volume, pulmonary artery systolic and mean pressures, left ventricular end-diastolic pressure, left ventricular ejection fraction and left ventricular end-diastolic volume index did not differ in patients receiving the Björk-Shiley prosthesis from values in patients receiving the Hancock heterograft. Hence, the overall hemodynamic performance of both types of valves is remarkably similar. The choice between these two prostheses should, therefore, be governed not by the hemodynamic performance, but by other factors such as valve durability, risk of anticoagulation and incidence of valve-related complications.

Hancock弁置換患者の術後5.2～11.9年における遠隔成績の検討:生体弁の臨床的評価

Hancock弁置換患者の術後5.2～11.9年における遠隔成績の検討:生体弁の臨床的評価

Comparison of outcome after valve replacement with a bioprosthesis versus a mechanical prosthesis: Initial 5 year results of a randomized trial

The Veterans Administration Cooperative Study on Valvular Heart Disease was organized to compare survival and incidence of valve-related complications between patients receiving a bioprosthesis (the Hancock porcine heterograft) and a mechanical prosthesis (the Björk-Shiley spherical disc valve). Five hundred seventy-five patients undergoing single aortic or mitral valve replacement were randomized at surgery to one of the two valve types. At an average follow-up of 5 years (range 3 to 8) there are no statistically significant differences in survival between patients with the two valve types in the aortic valve replacement group. There is a statistically nonsignificant trend toward improved survival in patients undergoing mitral valve replacement with a bioprosthesis compared with a mechanical prosthesis (5 year survival probability was 0.70 +/- 0.05 and 0.58 +/- 0.06, respectively). Fatal and nonfatal valve-related complications occurred significantly less frequently in patients with a bioprosthesis compared with a mechanical prosthesis for both mitral and aortic valve replacement. Five year complication-free probability was 0.67 +/- 0.05 and 0.45 +/- 0.06, respectively, for patients with mitral valve replacement and 0.63 +/- 0.04 and 0.53 +/- 0.04, respectively, for those with aortic valve replacement. The difference in overall complication rates was largely due to the increased number of clinically significant but nonfatal bleeding episodes in patients receiving a mechanical prosthesis. Adjustment for differences in baseline characteristics between patients receiving a mitral mechanical prosthesis and a mitral bioprosthesis reduced the statistical significance of the difference in both mortality and complications.

Frequency analysis of Ionescu-Shiley prosthetic closing sounds in patients with normally functioning prostheses.

To document the frequency distribution of lonescu-Shiley (IS) bovine pericardial xenograft valve sounds, a study was conducted on three groups of clinically stable subjects with valves implanted for less than 5 years. These groups consisted of 61 subjects with aortic IS valves, 28 subjects with mitral IS valves and 18 subjects with mitral Hancock porcine xenograft valves. Multiple comparisons with a Scheffe with mitral Hancock porcine xenograft valves. Multiple comparisons with a Scheffe test at level a=0.01 showed that the spectral characteristics of closing sounds produced by normal IS and Hancock xenografts implanted in the mitral position were both significantly different from those of IS xenografts implanted in the aortic position but not significantly different from each other. In addition, the spectral distribution of IS closing sounds was highly reproducible and very slightly affected by the duration of the implant up to 5 years.

Long-term comparative analysis of the Björk-Shiley and Hancock valves implanted in 1975

The long-term results in all patients undergoing isolated mitral, aortic, or double mitral-aortic heart valve replacement operated upon in 1975 has been retrospectively analyzed. A total of 153 patients received the standard Björk-Shiley (flat pyrolytic disc) mechanical prostheses and 150 patients received the noncomposite Hancock porcine xenograft. Overall operative mortality was not significantly different between groups. All patients receiving a Björk-Shiley prosthesis, but none in the Hancock group, received long-term anticoagulant therapy. Medium and long-term actuarial survival rates (5 and 10 years postoperatively) were comparable for the two groups (88% for Björk-Shiley and 84% for Hancock [NS] at 5 years; 86% for Björk-Shiley and 80% for Hancock at 10 years [NS]). The incidence of systemic embolism was similar in the two groups (1.6% +/- 0.4% per patient-year for the Björk-Shiley group and 1.3% +/- 0.3% per patient-year for the Hancock group [NS]). Also the incidence of endocarditis was similar (0.6% +/- 0.2% per patient-year for the Björk-Shiley group and 0.8% +/- 0.3% per patient-year for the Hancock group [NS]). In the Hancock group the overall incidence of reoperations was significantly higher than in the Björk-Shiley group (4.2% +/- 0.6% per patient-year versus 0.9% +/- 0.3% per patient-year (p = 0.001). The major cause for reoperation in the Hancock group was primary tissue failure (3% +/- 0.5% per patient-year). In the Björk-Shiley group the major cause of reoperation was valve thrombosis (0.5% +/- 0.2% per patient-year). Therefore, accepting the fact that other bioprostheses may behave differently from the Hancock noncomposite xenograft, we currently restrict our indications for valve replacement with bioprostheses.

Prognosis in valvular heart disease: I. Description of Purpose, Organization, Data Collection Techniques, Estimates of Statistical Power, and Criteria for Termination of Patient Entry

This report describes the design of a multicenter study with two major goals: (1) the identification of valvular heart disease patients at risk for death or a serious complication, and (2) the comparison of hemodynamic function and late outcome of a mechanical prosthetic valve (Björk-Shiley) with a bioprosthesis (Hancock porcine heterograft valve). Strengths of the study design are quantitative assessment of valvular and left ventricular function before and 6 months after valve replacement, measurement in a central laboratory of critical data items such as valve orifice area and left ventricular volumes, and assignment of cause of death and valve-related complications by a committee blinded to valve type. Statistical power calculated by a simulation technique shows only modest loss of power with frequent examination of outcome compared to infrequent examination. Guidelines for premature termination of the study because of superiority of one valve type are described; this includes a critical region with a sloping boundary, which allows for greater chance variation early in the study when the number of patients and events is small, gives the greatest statistical power, and yet appears to provide adequate protection for the subjects in the study.

Two-dimensional echocardiographic assessment of bioprosthetic valve dysfunction and infective endocarditis

Two-dimensional echocardiography of Hancock porcine heterograft valves was evaluated by correlation with clinical, hemodynamic, angiographic and pathologic findings in 80 patients. Ninety-five aortic and mitral bioprostheses were categorized by the type of valvular abnormality: group I, dysfunction due to primary tissue failure (41 valves); group II, dysfunction due to paravalvular leakage without infection (5 valves); group III, infective endocarditis with or without hemodynamic dysfunction (28 valves); and group IV, control cases without dysfunction or infection (21 valves). Increased size of a bioprosthetic leaflet image (minimal dimensions 3 x 5 mm) was observed in 46% (19 of 41) of cases with primary tissue failure and in 62% (10 of 16) of cases with leaflet vegetations due to endocarditis. Prolapse of leaflet echoes to below the level of the bioprosthetic sewing ring occurred in 76% (28 of 37) of cases with torn leaflets and also in 46% (6 of 13) of valves with vegetations on intact leaflets. Antegrade extension of leaflet echoes to beyond the level of the stents, observed in 4 of 16 cases with leaflet vegetations, was the only echocardiographic sign distinguishing leaflet infection from leaflet degeneration. Aortic bioprostheses with ring dehiscence affecting 40 to 90% of the anular circumference showed motion discordant with the motion of the adjacent aortic root and native anulus. Although echocardiographic abnormalities are frequently observed with bioprosthetic leaflet degeneration or infection, the echocardiographic appearance often does not distinguish between these two major complications and is best interpreted concurrently with other clinical and laboratory assessment.

Longevity of the formaldehyde-preserved Hancock porcine heterograft

Longevity of the formaldehyde-preserved Hancock porcine heterograft

Risk-benefit analysis of warfarin therapy in Hancock mitral valve replacement

The purpose of this investigation was to analyze the thromboembolic and/or major bleeding complications of 124 consecutive but nonrandomized patients who had only mitral valve replacement with the Hancock porcine xenograft between September, 1974 and June, 1979. These patients were treated either with or without anticoagulants. Four basic study groups were created: Group 1, warfarin; Group 2, aspirin; Group 3, no anticoagulants; and Group 4, warfarin and aspirin. Group 5 combined Groups 1 and 4 (warfarin and warfarin plus aspirin) and Group 6 combined Groups 2 and 3 (aspirin and no anticoagulants). The cardiac rhythm, history of embolism, and intraoperative findings of a thrombus in the left atrium were examined as risk factors for later thromboembolism . Follow-up time was 3.03 years (range 2.0 to 4.2 years). The embolic rate was not significantly different in any group (n = NS). In Groups 5 and 6 the embolic rate was 2.97 and 3.25 embolisms per 100 patient-years, respectively. Warfarin therapy resulted in significant major bleeding episodes, including two deaths (p less than 0.05). The number of patients with a history of a previous embolism, the finding of an intraoperative left atrial thrombus, or abnormal cardiac rhythm was insufficient to test embolic risk in the four treatment groups. We conclude that long-term warfarin therapy increases the risk of bleeding complications but may not significantly influence the incidence of thromboembolism arising from the Hancock porcine xenograft mitral valve. Other and larger studies are needed to confirm this last point.

122 HEART BLOCK COMPLICATING TRICUSPID VALVE REPLACEMENT IN CHILDREN

Evaluation of pediatric patients following tricuspid valve replacement (TVR) with Hancock porcine heterograft valves indicated a high incidence of complete heart block (CHB). Eight patients who received Hancock valves in the tricuspid position were identified. Their ages ranged from one and one half to 18 years. All patients had insufficient tricuspid valves: three had Ebstein's anomaly, three with enlarged right ventricles underwent TVR three to eight years after repair of tetralogy of Fallot, one had congenital tricuspid insufficiency associated with ventricular septal defect and pulmonic stenosis, and one had tricuspid insufficiency associated with d-transposition and mitral atresia. All patients developed at least transient CHB after surgery, five required cardiac pacing, and the two youngest received permanent pacemakers. Four of eight patients died. One died from massive bleeding in the immediate postoperative period and another from disruption of the prosthetic valve by bacterial endocarditis one and one half months after surgery. One patient with a permanent pacemaker died suddenly three months after surgery, and another who did not require cardiac pacing died suddenly 22 months after surgery. The nature of the injury to the conduction system is unknown. It is clear that CHB can be expected to complicate TVR in pediatric patients, that temporary or permanent cardiac pacing may be required after surgery, and that the long term prognosis despite pacing is only fair.

Marked thrombosis and calcification of porcine heterograft valves.

Prosthetic valvular dysfunction resulting in clinically significant complications occurred in six patients with Hancock porcine heterografts. In one patient with a prosthetic valve in the aortic position, massive prosthetic thrombosis resulted in sudden death. In two patients who had a mitral prosthesis, thrombosis resulted in congestive heart failure and systemic embolization; in one of the latter patients, the thrombi were infected with Candida sp. Calcification of organizing thrombi and cusp tissue resulted in valvular stenosis and congestive heart failure in one patient with an aortic prosthesis and in two patients with mitral prostheses. Four of the six patients died. The prosthetic valves had been in place for 6 months to 3 years before onset of complications. During the same 4-year interval, over 400 porcine prosthese were inserted. This report provides further clarification of the nature and frequency of clinical complications related to degeneration and thrombosis of Hancock porcine heterograft valves.

An important complication of Hancock mitral valve replacement in children.

Nine children ages 2--15 years have undergone mitral valve replacement (MVR) with Hancock porcine heterograft valves for severe mitral insufficiency. The etiology of the mitral valve disease was rheumatic in two patients, and congenital in seven. Porcine valve sizes ranged from 19--31 mm. Follow-up has been from 1.6 to 6.1 years (mean, 4.3 years). All nine children have had marked postoperative improvement, no thromboembolic complications despite no long-term anticoagulations, and no episodes of endocarditis. There have been no early or late deaths. Although six of the nine patients remain asymptomatic, three others developed severe fibrocalcific obstruction of the heterograft, requiring valve re-replacement at 3.5, 3.6, and 4.8 years following the initial valve replacement. This complication has not been previously reported in children. It is a factor that must be considered when deciding on MVR for children and their postoperative management.