Ionescu-Shiley Valve Research Articles

Long-Term Survival and Freedom From Reoperation After Placement of a Pulmonary Xenograft Valved Conduit

The optimal choice for pulmonary valve replacement (PVR) remains controversial. This study hypothesized that xenografts used for PVR would result in prolonged long-term survival and freedom from reoperation. Children and adults with congenital heart disease requiring PVR using a xenograft from 1980 to 1985 were reviewed. In all cases, the xenograft valve was either sewn or manufactured into a Dacron conduit, andthe conduit was sewn to the pulmonary artery bifurcation. Clinical data were analyzed, and survival and freedom from reoperation were determined using Kaplan-Meier analysis. Twenty-four patients received a xenograft forPVR at 14.6 ± 5.6 years. Conduit size ranged from 21to 27mm. Most patients received a Carpentier-Edwards valved conduit (n= 17), followed by a Hancock valved conduit (n= 5) and an Ionescu-Shiley valve sewn into aDacron graft (n= 2). No perioperative deaths occurred. Reoperation was required mainly for pulmonary stenosis (72.7%), followed by pulmonary insufficiency (18.2%), or both stenosis and insufficiency (9%). Freedom from reoperation was 90%, 56%, 43%, and14% at 10, 20, 25, and 30 years, respectively. At mostrecent follow-up the was only death, which was related to severe biventricular failure 25 years after conduit implant. PVR using a xenograft valved conduit results in prolonged freedom from reoperation and excellent long-term survival. These data, which provide long-term follow-up information on xenograft valves after PVR.

心音図法(II-OS時間)による僧帽弁位Ionescu-Shiley弁の弁機能評価

心音図法(II-OS時間)による僧帽弁位Ionescu-Shiley弁の弁機能評価

Unusual 25-Year Durability of an Ionescu-Shiley Pericardial Bioprosthesis

Ionescu-Shiley valve was withdrawn from clinical use in 1987 for its early structural failure after implantation. This was due to valve design rather than the natural properties of bovine pericardium itself. We describe the unexpected 25-year survival of an Ionescu-Shiley bioprosthesis in the mitral and tricuspid positions, implanted to treat endomyocardial fibrosis. This report makes 2 important points: (1) pannus overgrowth may be a favorable determinant of the durability of xenografts, and (2) bovine pericardial valves may have excellent hemodynamic performance and tissue durability for more than 20 years in the mitral position even in young patients.

Twenty-six-year durability of an Ionescu–Shiley standard profile pericardial aortic valve

The Ionescu-Shiley pericardial valve (Shiley, Inc, Irvine, CA, USA) is a first generation bioprosthesis made from bovine pericardium. Despite its excellent hemodynamic performance, use of this prosthesis ceased because it had an unacceptably high rate of early structural deteriorations, especially in the era of the standard profile valve. We experienced a rare case of very long durability of an Ionescu-Shiley standard profile (ISSP) bioprosthesis.

Outcomes of mitral valve replacement in children: A competing-risks analysis

ObjectiveWe sought to define patient characteristics, outcomes, and associated factors after mitral valve replacement in children.MethodsWe included 104 children undergoing at least one mitral valve replacement between 1980 and 2003 and reviewed clinical records. Competing-risks methodology was used to determine time-related prevalence and associated risk factors after initial mitral valve replacement for death and repeat replacement.ResultsThe underlying mitral valve disease was congenital in 83%, rheumatic in 13%, Marfan syndrome in 3%, and isolated endocarditis in 1%, with 64% having primarily regurgitation, 16% having stenosis, 20% having both, and 32% having undergone previous valvotomy, valvuloplasty, or repair. There were 137 valve replacements, with 26 patients having more than one. Valve prosthesis type was St Jude Medical in 37%, Björk-Shiley in 25%, Carbomedics in 20%, Ionescu-Shiley in 10%, and other types in 8%. Both early and late complications were common. Median age at the initial replacement was 5.9 years (range, birth to 19 years). Competing-risks analysis predicted 19% to have died at 15 years after initial replacement, with risk factors including noncongenital valve morphology, lower weight, and longer duration of cardiopulmonary bypass. A repeat replacement was predicted for 71%, with risk factors including the presence of multiple left-heart obstructive lesions and Ionescu-Shiley valve prosthesis.ConclusionsMitral valve replacement might be necessary in children with extremely dysplastic valves and severe hemodynamic impairment or after failed repair. However, with the appropriate selection of the prosthetic valve and reduction of cardiopulmonary bypass time, surgeons might decrease mortality and increase prosthesis longevity. We sought to define patient characteristics, outcomes, and associated factors after mitral valve replacement in children. We included 104 children undergoing at least one mitral valve replacement between 1980 and 2003 and reviewed clinical records. Competing-risks methodology was used to determine time-related prevalence and associated risk factors after initial mitral valve replacement for death and repeat replacement. The underlying mitral valve disease was congenital in 83%, rheumatic in 13%, Marfan syndrome in 3%, and isolated endocarditis in 1%, with 64% having primarily regurgitation, 16% having stenosis, 20% having both, and 32% having undergone previous valvotomy, valvuloplasty, or repair. There were 137 valve replacements, with 26 patients having more than one. Valve prosthesis type was St Jude Medical in 37%, Björk-Shiley in 25%, Carbomedics in 20%, Ionescu-Shiley in 10%, and other types in 8%. Both early and late complications were common. Median age at the initial replacement was 5.9 years (range, birth to 19 years). Competing-risks analysis predicted 19% to have died at 15 years after initial replacement, with risk factors including noncongenital valve morphology, lower weight, and longer duration of cardiopulmonary bypass. A repeat replacement was predicted for 71%, with risk factors including the presence of multiple left-heart obstructive lesions and Ionescu-Shiley valve prosthesis. Mitral valve replacement might be necessary in children with extremely dysplastic valves and severe hemodynamic impairment or after failed repair. However, with the appropriate selection of the prosthetic valve and reduction of cardiopulmonary bypass time, surgeons might decrease mortality and increase prosthesis longevity.

Outcomes of mitral valve replacement in children: A competing-risks analysis

We sought to define patient characteristics, outcomes, and associated factors after mitral valve replacement in children. We included 104 children undergoing at least one mitral valve replacement between 1980 and 2003 and reviewed clinical records. Competing-risks methodology was used to determine time-related prevalence and associated risk factors after initial mitral valve replacement for death and repeat replacement. The underlying mitral valve disease was congenital in 83%, rheumatic in 13%, Marfan syndrome in 3%, and isolated endocarditis in 1%, with 64% having primarily regurgitation, 16% having stenosis, 20% having both, and 32% having undergone previous valvotomy, valvuloplasty, or repair. There were 137 valve replacements, with 26 patients having more than one. Valve prosthesis type was St Jude Medical in 37%, Bjork-Shiley in 25%, Carbomedics in 20%, Ionescu-Shiley in 10%, and other types in 8%. Both early and late complications were common. Median age at the initial replacement was 5.9 years (range, birth to 19 years). Competing-risks analysis predicted 19% to have died at 15 years after initial replacement, with risk factors including noncongenital valve morphology, lower weight, and longer duration of cardiopulmonary bypass. A repeat replacement was predicted for 71%, with risk factors including the presence of multiple left-heart obstructive lesions and Ionescu-Shiley valve prosthesis. Mitral valve replacement might be necessary in children with extremely dysplastic valves and severe hemodynamic impairment or after failed repair. However, with the appropriate selection of the prosthetic valve and reduction of cardiopulmonary bypass time, surgeons might decrease mortality and increase prosthesis longevity.

Serial Doppler echocardiographic evaluation of Carpentier-Edwards pericardial valve dysfunction: Comparison with Ionescu-Shiley valve

Background: Doppler echocardiography is a valuable noninvasive method for evaluating of the occurrence and degree of either prosthetic valve stenosis or regurgitation. By using serial Doppler echocardiographic examination, we evaluated the incidence and the mode of the Carpentier-Edwards pericardial valve (CEPX) dysfunction compared with that of the Ionescu-Shiley valve (IS). Methods and Results: After aortic and/or mitral valve replacement, 80 patients with CEPX and 111 with IS underwent Doppler echocardiography at intervals of at least 2 years after surgery. The average durations of follow-up were 6.1 ± 2.9 years for patients with CEPX and 7.2 ± 3.0 years for those with IS. Bioprosthetic valve stenosis was defined as reduced excursion of the bioprosthetic valve leaflets and peak gradient ≥60 mm Hg after aortic valve replacement and mean gradient ≥7 mm Hg after mitral valve replacement. Bioprosthetic valve regurgitation caused by bioprosthetic valve dysfunction was defined as grade ≥3 transvalvular regurgitation. In the aortic position, although there was no significant difference in the actuarial rate of freedom from bioprosthetic valve stenosis between patients with IS and those with CEPX (10 years after surgery, 88% ± 7% vs 90%, NS), bioprosthetic regurgitation caused by bioprosthetic valve dysfunction occurred less frequently in patients with CEPX than in those with IS (10 years after surgery, 86% vs 54% ± 9%, p < 0.05). In the mitral position, bioprosthetic valve stenosis occurred more frequently in patients with CEPX than in those with IS (10 years after surgery, 54% ± 11% vs 72% ± 8%, p < 0.01). Although grade ≥3 transvalvular bioprosthetic regurgitation occurred later in patients with CEPX than in those with IS, there was no significant difference in the actuarial rate of freedom from that regurgitation between patients with CEPX and those with IS (10 years after surgery, 63% ± 10% vs 54% ± 7%, NS). Conclusions: For aortic valve replacement, CEPX has good long-term durability because of the low incidence of bioprosthetic regurgitation. For mitral valve replacement, long-term durability of CEPX is poor, although medium-term durability is satisfactory. (Am Heart J 1998;135:1086-92.)

Hemodynamics of various designs of 19 mm pericardial aortic valve bioprosthesis

The hemodynamics of five designs of 19 mm pericardial aortic valve bioprostheses were examined in 47 resting patients by Doppler echocardiography. The salient differences among the five designs are that valve leaflets are mounted inside the support frame in one (the Carpentier-Edwards valve, evaluated in 4 patients) and outside the frame in the other four (the Ionescu-Shiley (16 patients), Mitroflow (4), Bioflo (8) and Labcor-Santiago (15)); and that two models have either total (Bioflo) or partial (Labcor-Santiago) protective pericardial sheaths on the stent, while the other three do not. The hemodynamic parameters determined included transvalvular pressure drop, valve area, left ventricular outflow tract diameter, subvalvular/valvular velocity ratio and subvalvular/valvular velocity-time integral ratio. There were no significant differences among the various valves as regards left ventricular outflow tract diameter, subvalvular/valvular velocity ratio or subvalvular/valvular velocity-time integral ratio. Negative correlation between left ventricular outflow tract diameter and subvalvular velocity (r = -0.66, P < 0.001) confirmed the need to correct for prevalvular velocities when using the Bernouilli equation to calculate the pressure drop across small pericardial aortic valve bioprostheses. The Bioflo design caused significantly greater pressure drops (peak 38.3 +/- 8.3 mmHg, mean 24.6 +/- 4.8 mmHg) and smaller areas (0.82 +/- 0.17 cm2) than the Ionescu-Shiley (20.3 +/- 5.6 and 11.7 +/- 3.8 mmHg, 1.19 +/- 5.3 and 10.1 +/- 3.1 mmHg, 1.27 +/- 0.12 cm2) valves.

Long-term experience with the ionescu-shiley pericardial valve

To determine the long-term durability of the Ionescu-Shiley valve, we analyzed our experience with this valve at the University of Ottawa Heart Institute. To 1988, 780 patients have had aortic valve replacement (AVR = 528) or mitral valve replacement (MVR = 252). Of the aortic valves, 310 were standard profile and 218 were low profile. Of the mitral valves, 143 were standard profile and 109 were low profile. Actuarial survival at 10 years was as follows: AVR, 62% +/- 3%; MVR, 58% +/- 4%; p = 0.42. At 14 years, the results were AVR, 44% +/- 1% and MVR, 46% +/- 5%; p = 0.40. Reoperation was required in 197 patients. Structural failure was present in 85% of these valves, with leaflet tears alone in 69%, tears with calcification in 21%, and calcification alone in 10%. Leaflet tears occurred in 95% after AVR and in 78% after MVR (p = 0.006) and were seen in 95% of low-profile valves and 87% of standard-profile valves (p = 0.16). The actuarial freedom from reoperation at 10 years was: AVR, 58% +/- 3%; MVR, 62% +/- 5%; p = 0.49. At 13 years, these rates were 38% +/- 4% for AVR and 25% +/- 9% for MVR (p = 0.79). For AVR, the 10-year rate of freedom from reoperation was 57% +/- 4% for standard-profile valves and 57% +/- 8% for low-profile valves (p = 1.0). Similarly for MVR, the 10-year freedom from reoperation was 61% +/- 6% for standard-profile valves and 68% +/- 8% for low-profile valves.(ABSTRACT TRUNCATED AT 250 WORDS)

Ionescu-Shiley valve failure II: Experience with 25 low-profile expiants

A group of patients who had low-profile Ionescu-Shiley valves implanted, 237 aortic and 130 mitral, was reviewed for cases of bioprosthetic failure requiring explantation. Fourteen such aortic and 11 mitral valves were recovered at operation. The most common reason for explantation was valvular insufficiency due to cusp tears, accounting for 50.0% of aortic and 82.0% of mitral explants. Morphologic examination of the valves suggested a common mode of failure with tears, and this is illustrated. The clinical and pathologic patterns of this valve's failure are compared with those of the standard-profile Ionescu-Shiley valve, and many similarities exist. A tendency for a larger proportion of mitral valve failures with tears is, however, in contrast to observations of the standard-profile valve, in which aortic failures are more common. Additionally, low-profile valves, in either the aortic or mitral positions, fail after a shorter time in situ than their standard-profile counterparts, at a mean of 45.1 months versus 78.0 in the aortic position ( p < 0.01) and at 52.2 months versus 73.8 in the mitral position ( p < 0.05). These differences in the performance of the Ionescu-Shiley valve models may have implications for the design of future bioprostheses.

Ionescu-Shiley valve failure I: Experience with 125 standard-profile explants

A group of standard-profile Ionescu-Shiley valve implants, 357 aortic and 190 mitral, was reviewed for cases of failure requiring surgical explantation. To date, 90 (25.2%) of the aortic and 35 (18.4%) of the mitral valves have failed, and are the subject of this analysis. Observations of these explants confirm previous suggestions about the clinical and pathologic patterns of the Ionescu-Shiley valve's failure, but are extended in this study to allow more confident statistical analyses. Cusp tear with insufficiency remains the most important reason for explantation, precipitating removal to date of 19.1% of the aortic and 10.0% of the mitral valves implanted. This difference, aortic versus mitral, is significant ( p < 0.006) and the reverse of observations made in other studies of pericardial valves. In this review there is no significant difference in the proportion of aortic and mitral valves that failed with calcification (2.2% and 3.1%, respectively). Aortic Ionescu-Shiley valves failing with tears had a mean of 3.1 tears per valve, whereas mitral valves had 1.2. Aortic valves also showed considerably more pretear wear than did mitral valves. Although the large number of these Ionescu-Shiley valve failures has been a profound clinical disappointment, it has provided an opportunity to observe and detail the pathology of their failure.

Long-term results of Ionescu-Shiley valve in the tricuspid position

A retrospective analysis of the long-term results of using the Ionescu-Shiley pericardial bioprosthesis in the tricuspid position was carried out on 73 patients (8 men, 65 women). Of these procedures, ten were tricuspid valve replacement alone and the remainder were in combination with other valve procedures. The mean follow-up was 9.6 years (range, 4 to 18 years). The mean age of the patients was 53 years (range, 27 to 78 years). Seventy-one of the patients suffered tricuspid valve dysfunction from rheumatic heart disease. There were 13 postoperative deaths (within 30 days), giving a mortality rate of 17.8%. The actuarial survival at 10 years was 71% ± 4.2%. Of the survivors, 49 (79.6%) were in functional class I or II. Primary tissue valve failure in the tricuspid position occurred in 1 patient 12 years after implantation and required reoperation. In another patient bioprosthetic tricuspid valve endocarditis developed. There was no incidence of thromboembolic complications. We conclude that the lonescu-Shiley pericardial bioprosthesis was a satisfactory prosthesis in the tricuspid position in patients with acquired valvar dysfunction.

Results in 117 patients with 17 and 19 mm valves

The Ionescu-Shiley pericardial valve was our bioprosthetic valve of choice between 1981 and 1985 for patients in whom the aortic anulus could not accept a valve larger than 19 mm in outer diameter or in whom the avoidance of warfarin sodium (Coumadin) was important A series of 117 consecutive patients who received 17 or 19 mm valves for isolated aortic valve replacement or aortic valve replacement combined with coronary artery bypass grafting or other valvular procedures was analyzed. Overall, 74% of the patients were female, with a mean age of 70.9 years and a body surface area of 1.67 ± 0.19 m 2 ; 92.3% were in New York Heart Association class III-IV, and the operation was urgent or emergent in 46%. The operative mortality rate was 7.7%, with no deaths in patients undergoing isolated elective first-time aortic valve replacement Mean follow-up for survivors was 2.5 years (10 to 62 months). There were 20 late deaths, of which three were valve related, three were due to sudden death or arrhythmias, and two were due to persistent heart failure. The actuarial survival rate at 5 years was 68%. Clinical follow-up revealed a low incidence of valve-related complications, and 96.4% of survivors were in class I-II. Postoperative echocardiography before hospital discharge revealed a maximum instantaneous gradient of 18.4 ± 3.0 mm Hg in five patients having a 17 mm valve and 31.3 ± 12.7 mm Hg in 20 patients having a 19 mm valve. Doppler echocardiography was performed in 22 patients at a mean follow-up of 39.3 ± 11.7 months. The maximum instantaneous gradient was 25 ± 17.2 mm Hg for 17 mm and 17.41 ± 5.4 mm Hg for 19 mm valves at late follow-up. The effective orifice area was 0.85 ± 0.1 cm 2 for 17 mm and 1.21 ± 0.21 cm 2 for 19 mm valves. This study defines the normal range of Doppler echocardiographic transprosthetic gradients for the Ionescu-Shiley valve and confirms that low operative mortality and excellent clinical improvement can result from the use of small Ionescu-Shiley valves in elderly patients despite moderate postoperative transvalvular gradients.

Automatic detection of sounds and murmurs in patients with Ionescu-Shiley aortic bioprostheses.

The problems encountered in the automatic detection of cardiac sounds and murmurs are numerous. The phonocardiogram (PCG) is a complex signal produced by deterministic events such as the opening and closing of the heart valves, and by random phenomena such as blood-flow turbulence. In addition, background noise and the dependence of the PCG on the recording sites render automatic detection a difficult task. In the paper we present an iterative automatic detection algorithm based on the a priori knowledge of spectral and temporal characteristics of the first and second heart sounds, the valve opening clicks, and the systolic and diastolic murmurs. The algorithm uses estimates of the PCG envelope and noise level to identify iteratively the position and duration of the significant acoustic events contained in the PCG. The results indicate that it is particularly effective in detecting the second heart sound and the aortic component of the second heart sound in patients with Ionescu-Shiley aortic valve bioprostheses. It has also some potential for the detection of the first heart sound, the systolic murmur and the diastolic murmur.

Pericardial heterografts: a comparative study of suture pull-out and tissue strength

The force required to pull sutures out of glutaraldehyde fixed bovine pericardium, for four different suture bites: 0.5 mm, 1 mm, 1.5 mm and 2.0 mm, was compared with the tissue strength. The mean suture pull-out force was significantly lower than the tissue strength for all bites, with a minimum value of 2.86 ± 1.02 N for the 0.5 mm bite and a maximum value of 6.32 ± 0.77 N for the 2.0 mm bite. The mean force which produced failure of the chemically modified pericardium was 15.49 ± 8.48 N . The mean force at pull-out of the sutures lay on a regression line: force at failure = 1.68 + 2.25 × Bite. A video film of the experiments showed that the suture does not cut through the pericardium. It pull a V-shaped band of collagen fibre bundles through the stationary pericardium. Eventually this band breaks away from the free edge of the tissue specimen. The specimens under uniaxial load failed by laminate debonding of two layers of tissue, rupture of the serosal surface layer followed by shear and fibre slippage. These results indicate that any suture which bears load, during the normal functioning of a heart valve substitute, will be a source of weakness, compared to the overall tissue strength. As a consequence the alignment/holding suture of the Standard Ionescu-Shiley valve and the modified stitch of the low profile valve are likely to be potential sites of fatigue failure.

Porcine versus pericardial bioprostheses: A comparison of late results in 1,593 patients

From 1976 to 1988, 1,593 patients underwent valve replacement with a porcine (878 patients) or a pericardial bioprosthesis (715 patients). There were 701 aortic, 678 mitral, and 214 multiple-valve replacements. Follow-up was obtained for 1,559 patients (98%). Early mortality was 9% (79 patients) in the porcine valve group and 5% (37 patients) among patients with a pericardial valve ( p < 0.01). Late survival after replacement with porcine valves was 80% ± 1% and 62% ± 3% at 5 and 10 years, respectively. With pericardial valves, 5-year survival was 79% ± 2%. Among valve-related complications, rates of freedom from thromboembolism, endocarditis, and hemorrhage after 6 years were similar for both valve groups. Freedom from reoperation at 6 years was also similar after aortic (96% versus 91%) or multiple-valve replacement (95% versus 88%). However, for mitral valve replacement, freedom from reoperation was significantly better with porcine valves than with pericardial valves at 6 years (92% versus 68%; p < 0.001). This difference was mainly due to the Ionescu-Shiley valve, which accounted for 83% of primary tissue failures among pericardial bioprostheses implanted in the mitral position ( 10 / 12 patients). After 6 years, freedom from primary tissue failure of mitral valves was 92% ± 2% with porcine and 70% ± 11% with pericardial bioprostheses ( p < 0.0001). The degree of clinical improvement among survivors was similar with both valve types. Thus, in the aortic position, pericardial valves compare with porcine valves up to 6 years, whereas in the mitral position, the durability of the former is significantly less, mainly because of the suboptimal performance of the Ionescu-Shiley pericardial bioprosthesis.

The Ionescu-Shiley Pericardial Valve: Results in 473 Patients

From January 1, 1980, through December 31, 1985, 473 patients underwent valve replacement with an Ionescu-Shiley valve. Overall hospital mortality was 7.8%. Major associated procedures and preoperative New York Heart Association (NYHA) Classes IV and V influenced hospital mortality significantly. The mean follow-up was 2.6 ± 1.3 years. Late mortality was 5.9%. Overall actuarial survival was 81% at 5 years. A chief cause of reoperation was cusp rupture of a mitral prosthesis in 5 patients (all after aortic and mitral valve replacement). The overall actuarial reoperation-free incidence was 93% at 5 years. Thromboembolic (TB) phenomena occurred at a linear incidence of 1.4 ± 0.3% per patient-year or an actuarial thromboembolism-free incidence of 92% at 5 years. Univariate and multivariate analyses showed that postoperative NYHA Class, rhythm at follow-up, and anticoagulant therapy significantly influenced the incidence of TE phenomena.

Pulsed, continuous, and color flow Doppler echocardiographic assessment of normal and abnormal Ionescu-Shiley pericardial valves.

We studied the value of pulsed, continuous, and color flow Doppler echocardiography for identifying normal and abnormal function in 51 Ionescu-Shiley bovine pericardial valves. In 15 patients with clinically normal functioning mitral valves, the peak and mean pressure gradients as calculated by the modified Bernoulli equation were 8.5 +/- 4.9 mmHg (mean +/- SD) and 2.6 +/- 2.9 mmHg, respectively. The mitral valve area as calculated by the pressure half-time method was 2.2 +/- 0.6 cm2. In 18 patients with normally functioning aortic valves, the peak and mean pressure gradients were 22.9 +/- 9.0 mmHg and 11.1 +/- 5.0 mmHg, respectively. In five patients with suspected mitral prosthetic dysfunction, two-dimensional and Doppler echocardiography showed: two had mitral stenosis with a mean gradient of 14.2 mmHg and mean mitral valve area of 1.0 cm2, two had severe mitral regurgitation, and one was thickened but nonstenotic. In 13 patients with suspected aortic prosthetic dysfunction, two-dimensional and Doppler echocardiography showed: two patients had markedly thickened leaflets and mean aortic gradient of 41.5 mmHg, two patients had mild aortic regurgitation, four patients had severe aortic regurgitation, and five patients had systolic murmurs secondary to pathology unrelated to the prosthetic aortic valve. Of the three patients with severe aortic regurgitation who had color Doppler, the site and direction of the regurgitant jet was correctly identified in all compared to intraoperative assessment. Pulsed, continuous, and color flow Doppler are useful as noninvasive techniques in assessing Ionescu-Shiley valve hemodynamics and function.

Experimental evaluation of the mitroflow pericardial heart valve prosthesis. Part II. Pathologic examination.

The results of the morphologic and histopathologic examination of 37 bovine pericardial heart valve prostheses that were retrieved after experimental implantation in Chacma baboons for periods of one to twelve months are presented in this study. The implanted prostheses consisted of 33 Mitroflow valves, size 21 mm, that belonged to four different groups according to the method of preparation of the pericardium (process I to IV) and 4 commercially available Ionescu-Shiley valves, size 19 mm. All implantations were in the mitral position, except 1 Mitroflow and 1 Ionescu-Shiley prosthesis, which were implanted in the tricuspid position. Moderate or abundant noninfected thrombotic deposits were found on the cusps of 13 of the 33 Mitroflow valves (39%). The Ionescu-Shiley valves shared this tendency, perhaps to a lesser extent, for the formation of thrombus on the valve cusps. Results of transmission electron microscopy, scanning electron microscopy, and calcification analysis are also presented. In this experimental study, the authors did not identify any significant characteristics in the Mitroflow bovine pericardial heart valve prosthesis that would lead to improved or extended durability of this device over the commercially available Ionescu-Shiley bovine pericardial heart valve prosthesis and probably over any other glutaraldehyde-treated bioprosthesis. They would suggest, therefore, that any clinical investigations of the prosthesis be undertaken very cautiously.

Experimental evaluation of the mitroflow pericardial heart valve prosthesis. Part I. In vivo hemodynamic evaluation.

Evaluation of possible enhanced durability of the Mitroflow pericardial heart valve prosthesis was undertaken in an experimental animal model using the Chacma baboon. For comparison purposes a small series of 4 Ionescu-Shiley pericardial valves were also implanted. The 33 Mitroflow prostheses implanted were all manufacturer's size 21mm and belonged to 4 different groups according to the process used for the preparation of the pericardium (Process I to IV). The Ionescu-Shiley prostheses were all manufacturer's size 19mm and were commercially available valves. The valves were implanted in the mitral position, except one each Mitroflow and Ionescu-Shiley prosthesis that was implanted in the tricuspid position. Four animals died in the early postoperative period, between 2 and 14 days. Two died from a probable viral infection, one from a low cardiac output state and the fourth one from bacterial endocarditis. The clinical evaluation of the animals for an implantation time of up to twelve months was unremarkable. Hemodynamic studies were performed immediately after implantation (n = 29), at an intermediate cardiac catheterization at 9 months after implantation (n = 4) and at the time of terminal elective sacrifice of the animals (n = 33). From the data obtained the resultant prosthetic valve area at the time of elective sacrifice of the animals was also calculated. The data obtained for each of the 5 groups of valves tested are presented in the text. Transvalvular gradients measured at the time of sacrifice of the animals were elevated.(ABSTRACT TRUNCATED AT 250 WORDS)