Mitral valve replacement with the glutaraldehyde-preserved porcine heterograft

Microporous collagen spheres produced via thermally induced phase separation for tissue regeneration

Collagen is an abundant protein found in the extracellular matrix of many tissues. Due to its biocompatibility, it is a potentially ideal biomaterial for many tissue engineering applications. However, harvested collagen often requires restructuring into a three-dimensional matrix to facilitate applications such as implantation into poorly accessible tissue cavities. The aim of the current study was to produce a conformable collagen-based scaffold material capable of supporting tissue regeneration for use in wound repair applications. Microporous collagen spheres were prepared using a thermally induced phase separation (TIPS) technique and their biocompatibility was assessed. The collagen spheres were successfully cross-linked with glutaraldehyde vapour, rendering them mechanically more stable. When cultured with myofibroblasts the collagen spheres stimulated a prolonged significant increase in secretion of the angiogenic growth factor, vascular endothelial growth factor (VEGF), compared with cells alone. Control polycaprolactone (PCL) spheres failed to stimulate a similar prolonged increase in VEGF secretion. An enhanced angiogenic effect was also seen in vivo using the chick embryo chorioallantoic membrane assay, where a significant increase in the number of blood vessels converging towards collagen spheres was observed compared with control PCL spheres. The results from this study indicate that microporous collagen spheres produced using TIPS are biologically active and could offer a novel conformable scaffold for tissue regeneration in poorly accessible wounds.

Glutaraldehyde cross-linked chitosan microspheres as a long acting biodegradable drug delivery vehicle: studies on the in vitro release of mitoxantrone and in vivo degradation of microspheres in rat muscle

Chitosan microspheres were prepared from 74% deacetylated chitin by the glutaraldehyde cross-linking of an aqueous acetic acid dispersion of chitosan in a mixture of liquid paraffin and petroleum ether stabilized using sorbitan sesquioleate as the surfactant. Cross-linking and hardening of the spherical particles were achieved by the addition of glutaraldehyde-saturated toluene through the organic phase. A relatively novel antineoplastic agent, mitoxantrone, was incorporated into the microspheres and the drug release was studied in vitro into phosphate buffer for over 4 weeks at 27 degrees C. Drug release was found to be effectively controlled by the extent of cross-linking. Only about 25% of the incorporated drug was released over 36 days from microspheres of high cross-linking density. Implantation of placebo chitosan microspheres in the skeletal muscle of rats was carried out in order to assess the biocompatibility and biodegradability of the microspheres. Histological analysis showed that the microspheres were well tolerated by the living tissue. However, no significant biodegradation of the material was noticed over a period of 3 months in the skeletal muscle of rats. Data obtained indicate the possibility of using cross-linked chitosan microspheres as a drug carrier for sustained drug release for very long periods.

Normal values of prosthetic valve Doppler echocardiographic parameters: a review

Doppler echocardiography plays an important role in the evaluation of patients with prosthetic valves. The evaluation of flow velocities across prosthetic valves is more complicated compared with native valves, and flow velocities are specific for various types, positions, and sizes of prostheses. Because all prosthetic valves are at least mildly stenotic and a significant proportion is regurgitant, information regarding normally functioning prosthetic valves is important. Eighteen studies resulting in data on 1105 patients with normally functioning prosthetic valves were reviewed. Significant differences among the various types and sizes of prosthetic valves were found in both the aortic and mitral positions. The results are summarized in tables and figures that can be used for reference in a clinical laboratory.

Hemodynamic evaluation of porcine bioprostheses in the mitral position by Doppler echocardiography

Twenty-four patients with porcine bioprostheses in the mitral position were studied by Doppler echocardiography followed by cardiac catheterization within 24 hours. Doppler mean diastolic mitral valve gradient was calculated by a 3-point method and mitral valve area was determined by the pressure half-time method. Data from Doppler echocardiography and cardiac catheterization were compared. There was a strong correlation between Doppler echocardiography and catheterization-determined mean diastolic gradient: r = 0.9, standard error of estimate (SEE) = 1.4 mm/Hg (regression equation y = 0.63x + 1.41), p less than 0.001. There was also a strong correlation between Doppler echocardiography and catheterization-determined mitral valve area: r = 0.86, SEE = 0.18 cm2 (regression equation y = 0.64x + 0.52), p less than 0.001. Fourteen patients whose valvular function was considered normal by clinical evaluation had Doppler-calculated mean diastolic gradients of 4.5 to 9.5 mm Hg (mean 6.5 +/- 1.4); the Doppler-determined valve area was 1.15 to 2.0 cm2 (mean 1.54 +/- 0.3). Ten patients had a malfunctioning bioprosthesis, 7 had severe mitral regurgitation and 3 had stenosis. Valvular malfunction in all 10 patients was detected by Doppler echocardiography and confirmed by catheterization and angiocardiography. Nine patients underwent reoperation. Doppler hemodynamic evaluation of porcine bioprostheses in the mitral position provided noninvasive information comparable to that obtained by cardiac catheterization.

Preparation of [3H]collagen for studies of the biologic fate of xenogenic collagen implants in vivo

Reduction of a commercially available, pepsin-solubilized, bovine dermal collagen (Vitrogen 100) with sodium [3H]borohydride provided radiolabeled collagen preparations with specific activities ranging from 7.1-12.0 muCi/mg collagen. These specific activities were 2-3 times greater than those obtained by reduction of intact rat tail tendon collagen under similar conditions. The alpha, beta, and higher aggregate components of type I collagen were radiolabeled as well as the alpha component of a small amount of type III collagen present in the samples. Fractionation of cyanogen bromide peptides showed that alpha 1(I)CB7, alpha 1(I)CB8, and alpha 2(I)CB3,5 were the predominant peptides labeled by this procedure. Amino acid analysis indicated that the majority of the radioactivity was in reducible cross-links, precursors of these cross-links, and in hexosyllysine residues. Reconstitution experiments comparing this radiolabeled collagen with nonlabeled collagen showed them to be indistinguishable. Bacterial collagenase digestion of this reconstituted fibrillar collagen in both a lightly cross-linked (glutaraldehyde 0.0075%) and noncross-linked form provided evidence that digestion of labeled and nonlabeled collagens proceeded at similar rates. Thus, labeling did not change the properties of the collagen. Cross-linking made the preparation refractory to proteolytic degradation. Injection of fibrillar collagen preparations, spiked with radiolabeled collagen, into the guinea pig dermis followed by quantitation of the amount of radioactivity recovered from implant sites as a function of time, indicated that the lightly cross-linked samples also were more resistant to degradation in vivo than the noncross-linked preparation. The half-life of noncross-linked collagen was about 4 days while that of the cross-linked collagen was about 25 days. These degradation rates were much faster than observed for similar, nonlabeled samples injected into the dermis of humans, presumably due to a higher metabolic activity in the guinea pig dermis.

Doppler echocardiographic evaluation of patients with porcine mitral valves

The application of Doppler echocardiography to the study of valvular function has recently been extended to include prosthetic valves. We have used Doppler echocardiography to evaluate 40 patients with porcine mitral valves (PMV) implanted 0.5 to 99 months prior to examination. Three parameters of PMV flow were assessed: maximum diastolic left ventricular inflow velocity (Vmax), pressure half-time (P1/2t), and presence or absence of mitral regurgitation (MR). Normally functioning PMV (n = 29) were characterized by Vmax less than or equal to 180 cm/sec and P1/2t less than or equal to 160 msec. Within this group, P1/2t was not correlated significantly with the age of the patient nor with prosthesis size. Doppler correctly identified all 10 patients with MR. Among these 10 patients, Vmax was 206 +/- 53 cm/sec, significantly higher than the mean observed in normally functioning prostheses (136 +/- 24 cm/sec, p less than 0.001). In eight patients with stenosis of the PMV, mean P1/2t was 220 +/- 63 msec, and in seven of eight, it was greater than or equal to 180 msec (p less than 0.001 compared to normals). We conclude that: (1) Vmax less than or equal to 180 cm/sec, P1/2t less than or equal to 160 msec, and absence of systolic turbulence in the left atrium characterize normally functioning PMV; (2) P1/2t greater than or equal to 180 msec identifies patients with stenosis of the PMV; and (3) Doppler echocardiography can detect MR and separate mitral from tricuspid regurgitation.

Hemodynamic differentiation of pathologic and physiologic stenosis in mitral porcine bioprostheses

Porcine bioprostheses are physiologically stenotic valves. Degenerative calcification leading to pathologic stenosis is an increasingly recognized serious late complication of mitral valve replacement with a porcine bioprosthesis. Hemodynamic differentiation of pathologic from physiologic stenosis is important for identification of porcine bioprosthetic valve dysfunction. In 42 patients with a normal Hancock porcine bioprosthesis (standard model, sizes 27 to 33 mm), mean diastolic flow (65 to 461 ml/s), mean gradient (2.0 to 13.4 mm Hg) and effective orifice area (1.1 to 4.4 cm2) were determined at rest, during epicardial pacing (90, 110 and 130/min) and with isoproterenol infusion. A statistically significant increase in mean gradient occurred with increases in flow and decreases in valve size (p less than 0.05). Effective orifice area increased significantly as flow rate increased and as valve size increased (p less than 0.05). These measurements were compared with those in 16 patients with pathologically confirmed porcine bioprosthetic valve stenosis: 8 patients with reoperation (1.1% per patient-year) 3 to 8.5 years after mitral valve replacement and 8 previously reported abnormal cases. Stenotic failure rate was inversely related to valve size (2.1, 1.4, 0.5 and 0% per patient-year for sizes 27 to 33 mm). Stenotic and normal bioprostheses were not accurately differentiated on the basis of a single value for gradient or effective orifice area. A mathematical model that related flow to the square root of the mean gradient allowed complete separation of stenotic from normal prosthetic valve function, after valve size was accounted for and normal confidence limits were established (r = 0.74 to 0.94, sizes 27 to 33, p less than 0.0001). The effective orifice area-flow relation did not provide accurate differentiation of abnormal from normal function. Thus, normal mitral bioprostheses have significant transvalvular gradients whose magnitude depends on flow. Risk of stenotic failure is increased in the smaller valves, which have a larger gradient at implantation. Differentiation of pathologic from physiologic stenosis cannot be made on the basis of a single value for gradient or effective orifice area. Accurate hemodynamic differentiation is achieved by relating mean gradient to mean diastolic flow rate and valve size.

An examination of the biologic response to injectable, glutaraldehyde cross-linked collagen implants

The biologic response to injectable, glutaraldehyde cross-linked, fibrillar collagen implants in the rat subcutaneous model was shown to be a function of the concentration of glutaraldehyde used for cross-linking. The collagen was prepared from bovine hide by pepsin solubilization and reconstituted as a fibrillar suspension of 35 mg collagen/mL. Fibrillar collagen implants cross-linked with glutaraldehyde concentrations equal to or less than 0.01% exhibited a response characterized by fibroblast invasion, neovascularization and little, if any, evidence of inflammation. Implants cross-linked with 0.1 and 1.0% glutaraldehyde elicited a foreign body/giant cell reaction and varying degrees of implant erosion. The interaction of human skin fibroblasts with 0.01% glutaraldehyde cross-linked collagen in vitro was found to be dependent on the culture conditions utilized to evaluate the interaction. When the ratio of cell culture media to collagen was 20:1, cell invasion of the cross-linked preparations was observed, whereas, when this ratio was reduced to 1:1, such interactions could not be detected. Noncross-linked preparations were colonized by cells regardless of the experimental conditions used. Studies of implants in both the rat and guinea pig subcutaneous models indicated that glutaraldehyde cross-linking concentrations as low as 0.0075% provided enhanced wet weight recovery (wet weight persistence) and resistance to biologic degradation (collagen persistence) as compared to noncross-linked fibrillar collagen preparations. These cross-linked implants also exhibited a greater degree of fibroblast infiltration and vascularization. Between 30 and 60 days, some degree of calcification developed in both collagen formulations implanted in rats and guinea pigs; however, the reaction occurred with greater frequency and intensity in cross-linked preparations in guinea pigs. Calcification in the guinea pig was followed by the appearance of focal areas of ossification.

Clinical experience with porcine xenografts in the mitral position

In a 7-year period, 120 porcine xenografts, 16 of Hancock and 104 of Carpentier-Edwards type, were implanted in the mitral position in patients with isolated mitral valve disease. The operative mortality was 4.2%. The actuarial survival after 5 years was 93%. Death during the observation period was valve-related in two cases. Three valves had to be exchanged, one because of calcification and two because of prosthetic endocarditis. The risk of contracting prosthetic endocarditis was 0.38% per patient year. All the patients received peroral anticoagulant medication indefinitely. Two minor embolic episodes occurred, both in the first 6 post-operative months. The probability of freedom from thromboembolism was thus 98.2% after 7 years. In functional evaluation of 92 patients observed for at least 6 months, more than 90% were in NYHA class I or II. Porcine xenograft is a good valve substitute in the mitral position with a low incidence of complications, especially of thromboembolism, in patients on maintenance anticoagulant therapy. Long-term observations of this type of valve substitute are not yet available, however.

Prosthetic heart valves: a review

There are a number of difficulties inherent in the analysis of such a large and diverse quantity of data. In a substantial number of clinical trials, there is no significant effort made to evaluate prosthetic performance as a function of preoperative cardiac anatomy. Hemodynamics have not been systematically studied in relation to preexisting left ventricular size, shape, or configuration, mitral annular orientation, or left atrial size. Postoperative anticoagulation protocols vary from one institution to another and occasionally within study groups themselves. Less tangible variables such as alteration in surgical technique over time and differential familiarity of cardiovascular surgeons with the prostheses employed are chronic problems in any study of this sort. Perhaps the greatest variable in evaluating the postoperative performance of valvular prostheses over the past 20 yr is the radical improvement in techniques of intraoperative myocardial preservation. Notwithstanding, comparisons are possible within the confines of certain criteria. The caged ball value remains in use after 20 years of clinical experience. It has sustained the greatest number of modifications, probably because it has been the most extensively studied. Hemodynamics are adequate although its centrally obstructed design is responsible for increased turbulence, hemolysis, and neointimal proliferation, particularly in the aortic position. The device has been shown to be durable with virtually no reports of ball variance since the alteration of the silicone curing procedure in 1965. Thromboembolic rates are acceptable in the anticoagulated patient while prosthetic thrombosis is not a grave threat in the non-close clearance device. Incidence of endocarditis is not particularly different from that associated with all nonbioprosthetic valves, although there is a much greater published volume of clinical experience concerning recognition and treatment of late prosthetic valve endocarditis in patients with caged ball valves than there is for any other replacement device. Perhaps the most serious disadvantage to caged ball design is its size. Its large spatial requirements have led to anatomic complications in patients with small aortic roots, isolated mitral stenosis, left ventricular hypertrophy, and double valve replacement, among others. Nevertheless, this is still the valve of choice in some centers.(ABSTRACT TRUNCATED AT 400 WORDS)

Heterograft valve replacement experience

Survey of implantation of porcine heterograft valves in the Dunedin Cardiac Surgical Unit has been reviewed covering 140 patients and 166 valves with a follow-up ranging from 1-55 months. The low mortality, minimal complication rate and absence of long term anticoagulants in the post operative regime are emphasized. Discussion centres on the low rate of complications and the usefulness of this valve. As with all biological valves durability is still in question.

Early leaflet perforation as a cause of bioprosthetic dysfunction

Of 699 patients with 900 bioprostheses, who lived longer than six months, three cases of early perforation of bioprosthetic leaflets are reported. In two cases the cut ends of the suture used for valve insertion had perforated the bioprosthetic cusps from repeated trauma. Insertion of the sutures in the periphery of the sewing ring and cutting the sutures flush with the knots should avoid this complication. The third case showed massive collagen breakdown with destruction of most of the cusp tissue. A possible explanation for such a massive early tissue breakdown could be an inadequate collagen fixation by glutaraldehyde.

Spontaneous heterograft aortic valve failure

Glutaraldehyde-treated porcine aortic valve prostheses have been in clinical use for ten years. The long-term durability of these valves remains unknown although they have functioned well in most large clinical series for more than five years. At the present time, several manufacturers produce bioprostheses mounted on flexible stents. This report concerns the failure of an Edwards porcine xenograft in the aortic position 15 months following implantation. At reoperation, the right and left coronary leaflets of the explanted valve were torn from the aortic wall. The loss of wall integrity suggests that during the process of mounting the xenograft on the flexible stent, the aortic walls of the bioprosthesis may have been thinned beyond a critical point of maintenance of wall strength. The pathological and clinical findings of similar cases are reviewed.

Early calcification and obstruction of a mitral porcine bioprosthesis

A patient is described in whom severe prosthetic valvular stenosis developed ten months after mitral valve replacement with an Angell-Shiley porcine heterograft. At emergency operation, calcification of the prosthesis was revealed. Early calcification and stenosis of a porcine heterograft valve is a life-threatening complication that must be recognized promptly and treated by emergency valve replacement.

Porcine valves

To date, the glutaraldehyde porcine aortic valve xenograft has proved a good choice for valve replacement in both the aortic and mitral positions. Late thromboembolisms in the absence of long-term anticoagulation is virtually nonexistent in aortic valve replacement and very low in mitral valve replacement patients without a predisposing history. The hemodynamic performance of the porcine xenograft is adequate and comparable to that of mechanical prostheses. The potential for improved hydrodynamic function, particularly of very small sized valves, is great and already being realized. In spite of over 8 yr of xenograft experience, long-term durability remains the primary concern. Histologic study suggests that these valves undergo progressive postimplantation morphological alteration. However, to date, the incidence of tissue failure is very low. Although detailed reports of long-term valve series are surprisingly few, at present, there is no valve replacement device with a 10-yr experience proven structural integrity and a negligible incidence of valve-related morbidity. It will be 3-4 yr before a significant number of porcine xenograft patients either reach this point or experience valve failure. While this review of the valve literature does not permit a statistical comparison of valve types, we feel that it does allow us to attempt a general projection. On the basis of combined survival and valve-related complication rates, at 4 yr, the porcine xenograft appears to be a better choice than the mechanical prosthesis. Excessive tissue failure during the next 3-4 yr might reverse this opinion. However, even if an increase in valve failure does occur, the advantage of noncatastrophic disfunction and decreased valve-related complications may balance the risk of reoperative morbidity and mortality and continue to favor the porcine exnograft. Thus we could speculate that: (1) The tissue valve would be the valve of choice if (A) durability of 10 yr or more is proven, and valve complications with the xenograft remain as presently reported; (B) the incidence of valve complications with the mechanical prostheses at 10-yr follow-up continues to increase. (2) Mechanical prostheses would be the valves of choice if (A) xenograft valve failure is greater than 20% at 10 yr of follow-up; (B) the incidence of valve complications with the mechanical prostheses remains unchanged. (3) The choice of xenograft versus mechanical prosthesis will remain an open issue if valve failure and related complications with both types of device remain below 20% at 10-yr follow-up...

Porcine xenograft valves. Long-term (60-89-month) follow-up

An analysis of 211 patients who had porcine xenograft valve replacements at Henry Ford Hospital between October 1971 and March 1974, was accomplished, with 100% follow-up. The follow-up period extended from 60-89 months after implantation. One hundred sixty-seven patients with 192 valves survived the perioperative period and were subjected to life table analysis. Hemodynamically significant porcine xenograft degeneration that required reoperation occurred in 18 patients, two of whom had infective endocarditis. Only four valves failed within 48 months of surgery. Ten of 42 (23.8%) patients with isolated aortic valve replacement and eight of 102 patients (7.8%) patients with isolated mitral valve replacement required reoperation (p < 0.01). In patients under 25 years of age, six of nine surviving patients had repeat operations. Our data indicate that porcine xenograft degeneration is related to the duration of implantation and the age of the patient at the time implantation was performed. In addition, porcine xenograft valves in the aortic position are more likely to degenerate than are those in the mitral position.

Acute hemodynamic alterations after mitral valve replacement with the glutaraldehyde-treated porcine heterograft prosthesis

Perioperative hemodynamic changes following mitral valve replacement using the porcine heterograft prosthesis were measured in 21 patients with acquired mitral valve disease. Preoperatively, a state of compensatory cardiac failure was suggested by the following: an increased heart rate (HR) (96 beats per minute); low cardiac and stroke volume (SVI) indices (2.3 +/- 0.10 L/min/m2 and 25 +/- 2 ml/beat/m2); and increased systemic vascular resistance (SVR) (1,626 +/- 116 DYNE SEC CM-5). Bothe the mean pulmonary artery PAP) and pulmonary capillary wedge pressures (PCWP) were elevated as well (32 +/- 3 and 22 +/- 2 torr). Immediate hemodynamic improvement followed valve replacement. HR, SVR, PAP, and PCWP all decreased significantly. Twenty-four hours after valve replacement, PAP (23 +/- 1 torr) and PCWP (13 +/- 1 torr) demonstrated marked declines, SVR was reduced by one-third (1,173 +/- 87 dyne sec cm-5), HR had decreased by 10 beats per minute, and SVI had increased to 30 +/- 2 ml/beat/m2. The prompt circulatory improvement of patients soon after mitral valve replacement using the porcine heterograft compares favorably with studies in which other valve types were employed and in which postoperative cardiovascular depression was encountered frequently.

Severe calcification of glutaraldehyde-preserved porcine xenografts in children

Despite the widespread use of glutaraldehyde-preserved porcine xenografts, severe short-term calcification of these valves has been infrequently reported. This report describes four cases of glutaraldehyde-preserved porcine xenografts in the mitral valve position in which severe calcification occurred within 17 to 25 months of implantation. All four patients were children, aged 13 to 15 years. The clinical presentation in all four cases occurred at a late stage when there was severe xenograft obstruction, with acute symptoms of cardiac decompensation in the presence of pulmonary hypertension and right heart failure. There was rapid cardiac deterioration resulting in a low output state and episodic pulmonary edema necessitating urgent mitral valve replacement. In only one case was there clear auscultatory evidence of severe mitral stenosis. Calcification of these xenografts occurred in the presence of normal serum calcium levels and was not related to infective endocarditis. Histologic examination of the calcified xenografts strongly suggested dystrophic calcification resulting from primary collagen degeneration. The exact cause is unclear, but it appears that glutaraldehyde-preserved porcine xenografts may produce severe short-term calcification with acute hemodynamic deterioration necessitating urgent valve replacement and that this accelerated calcification may be a complication in young persons,

Hemodynamic factors that affect calculated orifice areas in the mitral hancock xenograft valve

From June 1974 to December 1978, 714 Hancock valves have been placed in 605 patients. One hundred seventy-five patients with a mitral xenograft have been restudied. The results were questionable due to the wide scatter and disparity between the calculated and the theoretical orifice of each valve size. To elucidate these differences, the hemodynamic data of 40 isolated, normal functioning mitral Hancock valves were reviewed. Early, middle and late diastolic mitral valve gradients were measured by planimetry and their corresponding flows were estimated by angiography. The paired data were fitted to exponential functions and specific lines for each Hancock valve size were obtained. By superimposing Gorlin's pressure and flow curves on these lines, the instantaneous effective orifice for each Hancock valve can be determined. We concluded that 1) the Hancock valve effective orifice is flow related and always lower than its theoretical opening; 2) normal function frequently cannot be firmly established by the mean effective area; and 3) the nomogram described may help in determining the time-related variations of a particular valve.

Infection of glutaraldehyde-preserved porcine valve heterografts

Gross, histologic and ultrastructural changes associated with bacterial infection are described in four porcine valve heterografts that had been in place in patients for 6 days to 28 months. In one patient, culture of the aortic tissue tag included in the heterograft container grew Mycobacterium chelonei; however, examination of the heterograft, recovered at necropsy 6 days after implantation, revealed small colonies of bacteria that differed morphologically from mycobacteria. A second heterograft was the site of staphylococcal infection associated with extensive destruction of collagen in the leaflets. Similar destruction was observed in a third heterograft, which was found to have organisms on ultrastructural study even though bacterial cultures of the valve were negative. The fourth heterograft, from a patient who died of coronary embolism secondary to dislodgment of vegetative material, contained structures resembling lysed bacteria. Observations in these 4 patients and review of published reports of infection involving 43 other patients with porcine valve heterografts indicates that infection in these valves: (1) develops in the fibrin layer that covers the cusps, (2) can involve the collagen in the leaflets, and (3) is uncommonly (three patients) associated with valve ring abscesses.

Structure-related thrombosis involving a porcine xenograft valve

A patient developed acute congestive heart failure following chordal rupture and underwent mitral valve replacement with a porcine xenograft. He recovered adequate hemodynamic function but died one month later with widespread bronchopneumonia. Postmortem examination revealed a prominent muscular shelf in the right coronary leaflet of the xenograft, and focal thrombosis involving the adjacent sewing ring and left atrial wall. The location of the thrombus suggests that it formed as a result of local stasis behind the large muscular shelf. Limiting the size of this muscular shelf by valve selection and construction may reduce the thrombogenicity of this prosthesis.

Is the Hancock porcine valve the best cardiac valve substitute today?

Valve replacement with the Hancock stabilized glutaraldehyde porcine aortic valve has been accomplished in 454 patients. Hospital mortality (influenced by a high proportion of patients in New York Heart Association Functional Class IV) was 17.6% (80/454). The first 221 patients discharged from hospital were followed for 36 to 75 months after valve replacement. There have been 26 late deaths among these patients; 88% (195/221) are alive. Of these 221 patients, 185 had single-valve replacement, (125 mitral and 60 aortic), and 36 underwent multiple-valve replacement. There have been 260 valves at risk up to 6 1/4 years, which is equivalent to 12,984.5 valve-months or 1,082 valve-years. Average follow-up is 4.16 years. There have been 13 valve failures in 10 patients. In 4 patients endocarditis was proved to be the cause of failure, and in 5 it was suspected; in 1 patient the failure the failure is unexplained. The pathological similarity between those in whom infection was documented and the other 5 is remarkable and raises the question of whether low-grade infections may be the cause of certain types of valve failure.

Hemodynamic evaluation of Lillehei-Kaiser and Starr-Edwards prosthesis

The central-flow low profile disc-valve prosthesis has been offered as an alternative to ball- and tissue-valve prostheses. Extensive laboratory investigation with both pulse duplicator and experimental animals has been reported for the Lillehei-Kaster prosthesis. A series of patients receiving this prosthesis underwent postoperative cardiac catheterization to better define the hemodynamic function of this prosthesis in vivo. Because of the variations in reports of hemodynamic data from various institutions, the results of post-operative studies in an earlier group of patients with Starr-Edwards prostheses were used as a standard for comparison. Good hemodynamic function was found with the pivoting-disc prosthesis in all but the smallest valve sizes. Lillehei-Kaster and early model Starr-Edwards prostheses with equivalent tissue annulus dimensions were found to have nearly equal valve areas in vivo in the aortic position. The Lillehei-Kaster mitral valves provided larger areas than Starr-Edwards prostheses in large tissue annulus sizes.

Echocardiographic evaluation of porcine heterograft valves in the mitral and aortic positions

We evaluated 15 porcine heterograft valves in the mitral position and seven in the aortic position by echocardiography. Combining our quantitative description of valve stent and leaflet motion with 31 previously reported cases, we suggest echocardiographic criteria for the range of normal porcine heterograft valve motion in the mitral position. Quantitative evaluation of valve leaflet and stent motion for valves in the aortic position is described for the first time. Correlative hemodynamic and echocardiographic data is provided for three patients who underwent postoperative catheterization. The use of echocardiography in following the function of porcine heterograft valves is discussed.

Severe and early stenosis of porcine heterograft mitral valve

A patient who had aortic and mitral valves replaced by Carpentier porcine heterografts for bacterial endocarditis developed severe heart failure 18 days after operation. A second emergency operation revealed that the mitral prosthesis had become severely stenosed and calcified. A loud Graham Steell murmur had developed during the 12 hours before reoperation but no distinct murmurs of mitral stenosis had been detected.

Mitral valve repair for significant mitral insufficiency

There has been skepticism since the early days of open heart surgery that good long-term or even short-term results were possible with repair of pure mitral insufficiency. The authors report 145 patients in whom a markedly insufficient mitral valve was repaired 6 months to 17 years previously and another 55 patients in whom repair of the insufficient mitral valve was performed along with myocardial revascularization from 6 months to 7 years previously. Comparative data with other published work reveals superior results with repair than with replacement with Starr-Edwards and Hancock glutaraldehyde-treated porcine valves and with far less emboli. Conservatism is urged in operating upon patients with mitral insufficiency. Repair of the valve rather than replacement is stressed for those patients requiring surgery.

The problem of valve prosthesis-patient mismatch

Valve prostheses have played an important part in the past two decades in the management of patients with valvular heart disease. However, many of the devices used in valve replacement have introduced new clinical problems. This paper deals with some of the problems associated with valve replacement, including one not previously emphasized--valve prosthesis-patient mismatch, which may cause obstruction to ventricular outflow and/or inflow.

Structural changes in glutaraldehyde-treated porcine heterografts used as substitute cardiac valves. Transmission and scanning electron microscopic observations in 12 patients

Scanning and transmission electron microscopic studies were made of (1) 12 glutaraldehyde-treated porcine valvular heterografts that had been implanted in patients for 2 days to 76 months; (2) 3 unimplanted commercially processed porcine aortic valves; and (3) 1 unprocessed porcine aortic valve. Comparison of unprocessed porcine valves and unimplanted commercially processed valves showed loss of endothelium and acid mucopolysaccharides during preimplantation processing. Short-term (less than 2 months) changes after implantation consisted of insudation of plasma proteins, penetration of erythrocytes into surface crevices, formation of a thin surface layer of fibrin, and deposition of macrophages, giant cells and a few platelets. Longer-term (more than 2 months) changes were proportional to the time interval after implantation and consisted of progressive disruption of collagen, erosion of the valve surfaces, formation of aggregates of platelets and accumulation of lipid. The surfaces of the leaflets did not become covered with endothelium or with a fibrous sheath. Calcific deposits were found in one valve and bacterial organisms in another. Thus, progressive breakdown of collagen appears to be a critical factor in determining the long-term durability of glutaraldehyde-treated porcine valvular heterografts.