Ionescu-Shiley Pericardial Valve Research Articles

Primary leaflet tear without dystrophic calcifications in a 25 years old Ionescu-Shiley pericardial valve in mitral position

Despite its excellent hemodynamic performance, the Ionescu-Shiley bovine pericardial bioprosthesis was removed from clinical use in 1987 because of an unacceptable high incidence of primary structural deterioration of the valve, mainly related to its design. Few examples of very long-term durability of this prosthesis have been recently reported. In all these cases, the valve dysfunction was caused by primary severe dystrophic calcification and/or pannus formation. In contrast, we describe the unexpected 25-year longevity of a mitral Ionescu-Shiley bioprosthesis which failed due to primary tears of one cusp but without dystrophic changes.

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.

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.

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)

Patterns of failure in Hancock pericardial bioprostheses

A series of Hancock pericardial valve bioprostheses was reviewed for cases of primary valve failure. Thirteen mitral and 10 aortic valve explants were recovered from 21 adult patients. Mitral valves had been in place for a mean of 56.4 months, and aortic valves for 53.8 months. All valves failed with cusp tears from stents (with a mean of 1.7 for mitral valves and 2.6 for aortic valves) in a predictable pattern, suggesting that wear and stress at cusp stitch sites are important in their pathogenesis. The topography of these tears is illustrated as are the less common associates of primary failure, such as calcification, fibrosis, and thrombosis. Similarities and differences of this valve's failure compared with that of the Ionescu-Shiley pericardial valve are discussed.

Long-term clinical results with the Ionescu-Shiley pericardial xenograft

From 1977 to 1987, 829 Ionescu-Shiley pericardial valves (Shiley, Inc., Irvine, Calif.) were implanted in 766 patients at the University of Ottawa Heart Institute. There were 476 patients who had aortic valve replacement, 234 who had mitral valve replacement, and 44 who had double valve replacement. The standard-profile design was used in 508 patients and the low-profile design in 321 patients. Follow-up was obtained for 97% of patients, with calculation of event-free probabilities. At 10 years the overall probability of freedom from structural failure was 48% +/- 7% after aortic valve replacement, 44% +/- 15% after mitral valve replacement, and 79% +/- 11% after double valve replacement. Although at 5 years the probability of failure was statistically lower with the low-profile design, this favorability was lost by 6 years. Freedom from structural failure was only 47% +/- 7% for the standard-profile valve at 10 years. Thus the probability of freedom from reoperation was only 46% +/- 7% after aortic valve replacement, 39% +/- 6% after mitral valve replacement, and 65% +/- 20% after double valve replacement at 10 years. Thromboembolism occurred in 69 patients, for a predicted freedom from this complication at 10 years of 79% +/- 3% after aortic, 73% +/- 7% after mitral, and 96% +/- 4% after double valve replacement. There were 31 cases of endocarditis. The 10-year predicted freedom from endocarditis, therefore, was 86% +/- 3% after aortic, 98% +/- 1% after mitral, and 97% +/- 1% after double valve replacement. A total of 221 operative and late deaths were recorded in this series. Prosthetic valve failure accounted for 27% of late deaths. The 10-year survival rates were estimated to be 56% +/- 5% (aortic valve replacement), 54% +/- 6% (mitral valve replacement), and 51% +/- 8% (double valve replacement). We concluded that the Ionescu-Shiley pericardial xenograft provides less than optimal clinical performance and its use has been discontinued.

Flow Characteristics of Bioprosthetic Heart Valves

A review of the in vivo and in vitro fluid dynamic performance of three bioprosthetic heart valves is presented. Data on Hancock porcine valves (standard models 242 aortic and 342 mitral and modified orifice model 250 aortic), Carpentier-Edwards porcine valves (model 2625 aortic and 6625 mitral), and the Ionescu-Shiley pericardial valve are reviewed. These valves were chosen because of their past or present popularity in clinical use and because of the variation in fluid dynamic performance reported by different investigators. The flow parameters that are reported include in vivo and in vitro mean pressure drop, cardiac output or cardiac index, regurgitant volume, effective orifice area, and performance index. These data provide a framework for differentiation of normal and abnormal bioprosthetic valve function.

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.

Long-term evaluation of the Ionescu-Shiley pericardial xenograft bioprosthesis in the aortic position.

From August 1977 through October 1984, 241 patients underwent aortic valve replacement with the Ionescu-Shiley pericardial valve. There were 130 males and 11 females in this series with an average age of 50.8 years (range 15 to 78 years). Isolated aortic valve replacement was performed in 121 patients (50.2%) and associated cardiac surgery in 120 (49.8%). Valve size was 21 mm or smaller in 107 cases (50.2%). Cumulative duration of follow-up was 1,260 patient-years with a mean follow-up of 5.16 years per patient. Five patients were lost to follow-up. Maximum follow-up was 10.5 years. There were 26 hospital deaths and 15 late deaths (1.19% per pt-yr). The expected 10.5 year actuarial survival rate is 82% +/- 2.9%. Twelve thromboembolic episodes occurred in seven patients--seven central and five peripheral events. The thromboembolic rate was 0.95% per patient-year--32% for patients with isolated aortic valve replacement and 0.63% for patients with concomitant surgery. Freedom from thromboembolic episodes at 10.5 years is 73% +/- 12%. Structural valve deterioration was found in 24 patients (1.9% per pt-yr) with an actuarial freedom from primary tissue failure of 77.5% +/- 5.4% at 10.5 years. Reoperation was required in 39 cases (3.09% per pt-yr)--primary tissue failure (n = 24), paravalvular leak (n = 7), infective endocarditis (n = 6), and valve thrombosis (n = 2).

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 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)

Velocity fields and turbulent stresses downstream of biological and mechanical aortic valve prostheses implanted in pigs.

Since detailed knowledge about velocity fields downstream of heart valve prostheses obtained from in vitro studies has not been followed up by similar detailed studies in vivo a pig model for acute velocity field studies downstream of aortic valve prostheses was established. Two mechanical and two bioprosthetic valves were studied and a dynamic three dimensional visualisation of velocity fields one diameter downstream performed under different haemodynamic conditions in a total of 22 pigs. The Ionescu-Shiley pericardial valve had velocity fields very similar to the normal native porcine aortic valve. The Edwards-Carpentier porcine valve caused a jet type flow, and the valve design of the St Jude Medical and Björk-Shiley Monostrut valves was reflected in the velocity profile. Normalised (mean(SEM] systolic Reynolds normal stresses in the total cross sectional area were: native porcine 15(1.5) Nm-2; St Jude Medical 24(3.4) Nm-2; Björk-Shiley Monostrut 25(1.6) Nm-2; Edwards-Carpentier Supra-annular 51(6.6) Nm-2; Ionescu-Shiley Pericardial 19(2.0) Nm-2. Reynolds normal stresses were higher in areas of rapidly changing or constantly high velocity gradients.

Primary tissue failure in pericardial heart valves

A number of centers have recorded a significant incidence of primary tissue failure with the standard Ionescu-Shiley pericardial valve. In most cases severe regurgitation was caused by leaflet tears adjacent to the edge of the cloth-covered stent. Our early clinical experience (up to 4 years' follow-up) with two new pericardial valves (Ionescu-Shiley low-profile and Hancock pericardial valves) has shown that primary tissue failure also occurs in these new valves. In vitro accelerated fatigue studies on seven of these valves (size 29 mm) showed that in vitro premature leaflet failure was caused by abrasion of the leaflet on the cloth-covering at the edge of the stent. Clinically, endothelialization and host tissue ingrowth on the cloth and the leaflets at the edge of the frame greatly reduced the amount of abrasion and the incidence of tissue failure. In seven of the eight explanted valves studied, leaflet tears occurred at the top of the stent posts where there was less endothelialization and tissue ingrowth, close to the points where sutures pass through the leaflets. It is likely that both abrasion and stress concentration around these sutures contributed to the tissue failures in the clinical valves.

Performance of the lonescu-Shiley Pericardial Valve in the Aortic Position: 100 Months Clinical Experience

From August 1977 through August 1984, 239 patients underwent aortic valve replacement (AVR) with the Ionescu-Shiley pericardial valve. Isolated AVR was performed in 112 patients and associated cardiac surgery in 127 patients (53.1%). One hundred twenty-eight patients were males and 111 females, with an average age of 50.6 years (range 15 to 78 years). There were 24 hospital deaths (10%) and 15 late deaths (8.9%). The expected 100 months survival rate was 82.8 +/- 5.5 (91.3 +/- 5.6% for isolated AVR, and 75 +/- 7.8% for associated AVR). All patients were postoperatively studied until December 1985. The cumulative duration of follow-up was 894.08 patient-years, with a mean follow-up of 44.9 months per patient. There were 10 thromboembolic episodes in this series (3 peripheral and 7 central), with a linearized incidence of 1.1% per patient-year. The actuarial projection of freedom from thromboembolic episodes at 100 months follow-up was 94.4 +/- 3.4% (96.9 +/- 2.2% for isolated AVR, and 92.6 +/- 3.9% for associated AVR). Twenty-five patients required reoperation (2.79% per patient-year): 6 for infective endocarditis, 3 for paravalvular leak, one for valve thrombosis, 3 for another valve explantation, and 12 for primary tissue failure (1.3% per patient-year). In conclusion, the Ionescu-Shiley valve has a satisfactory performance in the aortic position at long-term follow-up. In our experience, the higher rate of postoperative complications occurred among patients with concomitant cardiac surgery, so not necessarily related to this pericardial valve.

Rest and exercise hemodynamics following aortic valve replacement: A comparison between 19 and 21 mm Ionescu-Shiley pericardial and Carpentier-Edwards porcine valves

When aortic valve replacement is performed in a patient with a small anulus, significant obstruction of the left ventricular outflow tract may remain. Most prostheses are obstructive in the smaller sizes, and enlargement of the aortic anulus may be required to allow placement of a larger valve. To evaluate the hemodynamic performance of two commonly used tissue prostheses, the Ionescu-Shiley pericardial and Carpentier-Edwards porcine valves, 22 patients with either the 19 or 21 mm size were electively studied at rest and after exercise at a mean of 15 months after operation. The resting mean transvalvular gradient for 19 mm Ionescu-Shiley pericardial valves (n = 7), 10.6 +/- 9.2 mm Hg, was significantly lower than that for 19 mm Carpentier-Edwards valves (n = 3), 33.3 +/- 2.1 mm Hg, p less than 0.01. Following exercise, the mean gradient for 19 mm Ionescu-Shiley pericardial valves rose only to 13.8 +/- 8.5 mm Hg. No exercise data were available for the 19 mm Carpentier-Edwards valve. Among patients with 21 mm Ionescu-Shiley pericardial valves (n = 7), the mean transvalvular gradient at rest was 5.6 +/- 9.5 mm Hg, not significantly different from that of patients with 21 mm Carpentier-Edwards valves (n = 5), 9.8 +/- 18.3 mm Hg. After exercise, the gradients rose to 16.0 +/- 10.0 mm Hg and 25.5 +/- 23.8 mm Hg for the Ionescu-Shiley pericardial and Carpentier-Edwards valves, respectively (no statistical significance). Cardiac index was not different between groups. Gradients were not significantly higher in patients with body surface areas greater than 1.5 m2. It is concluded that the 19 and 21 mm Ionescu-Shiley pericardial valves possess excellent hemodynamics, even after exercise. This valve appears hemodynamically superior to the Carpentier-Edwards valve, particularly in the 19 mm size. Procedures to enlarge the aortic anulus are usually unnecessary when small Ionescu-Shiley pericardial valves are used, even in patients who have large body surface areas.

Comparison of bioprosthetic and mechanical valve replacement for active endocarditis

The choice between bioprosthetic or mechanical prosthetic valve replacement for active valvular endocarditis has been controversial. To establish the role of each, we reviewed the case histories of 185 patients who underwent valve replacement for active valvular endocarditis during the past 5 years. All patients had life-threatening, active bacterial endocarditis of a native or prosthetic valve. Group I (88 patients) had replacement with the Ionescu-Shiley pericardial valve and Group II (97 patients) with the St. Jude Medical valve. The male/female distribution, age range, and functional classification were the same in the two groups. Mean follow-up was approximately 20 months for both groups. Valve replacement was done because of native valve endocarditis in 76 patients in Group I and 49 patients in Group II. Of the remainder of the Group I patients, six had endocarditis of a bioprosthesis and six of a mechanical valve; of the remainder of Group II patients, 30 had endocarditis of a bioprosthesis and 18 of a mechanical valve. Early mortality was not significantly different between the two groups (14 deaths in each group). Of the 74 survivors in Group I, 15 underwent valve reoperation, 10 because of recurrent endocarditis and five because of sterile perivalvular leakage. The frequency of reoperation was significantly different (p less than 0.01) from that in Group II, in which only five patients underwent valve reoperation, four for recurrent endocarditis and one for sterile perivalvular leakage. The actuarial rate for freedom from reoperation was also significantly higher in Group II patients; 94.6% were free from reoperation at 4 years compared to 75% at 4 years in Group I patients (p less than 0.01). The actuarial survival rate, which also differed significantly between groups, was 78.7% at 4 years in Group I and 87.4% at 4 years in Group II (p less than 0.05). Patients receiving a bioprosthesis for active endocarditis had a significantly higher reoperation rate and a significantly greater incidence of recurrent endocarditis (p less than 0.01). Therefore, we prefer to use a mechanical valve for valve replacement in most patients who have active endocarditis.

Incidence of primary tissue valve failure with the Ionescu-Shiley pericardial valve: Preliminary results

This report provides retrospective follow-up data on 88 patients who received an Ionescu-Shiley bovine pericardial valve in the aortic position between August, 1977, and June. 1980. Seven instances of primary tissue degeneration occurred in seven of the 65 patients followed up until June, 1984. Cumulative duration of follow-up was 335.5 patient-years. The linearized incidence of primary tissue failure was 2.08% per patient-year. The actuarial rate of freedom from valve failure for patients with an Ionescu-Shiley valve in aortic position was 79% +/- 8% at 7 years of follow-up. This series shows a higher incidence of primary tissue failure with this prosthesis than with the glutaraldehyde-preserved porcine xenograft in the aortic position at 7 years' follow-up.

Ionescu-Shiley Pericardial Xenografts: Follow-up of Up to 6 Years

The results of valve replacement with the Ionescu-Shiley pericardial xenograft compare favorably with results obtained with other bioprostheses. From March, 1977, to July, 1983, 497 Ionescu-Shiley pericardial valves were implanted in 463 patients at the University of Ottawa Heart Institute. There were 292 patients who had aortic valve replacement (AVR), 140 with mitral valve replacement (MVR), 28 with double valve replacement, and 3 with triple valve replacement. The survivors were followed regularly. Actuarial analysis of late results indicates an expected survival of 71% at 6 years for patients who underwent AVR and 72% at 3 years for patients who had MVR. The only valve-related deaths were due to endocarditis, which occurred at a rate of 3.9% per patient-year for aortic valves and 0.6% per patient-year for mitral valves. Despite a low usage of formal anticoagulation, embolic complications occurred at a rate of 1.4% per patient-year for aortic valves and 4.0% per patient-year for mitral valves. Five valves were removed for intrinsic failure after 36 to 72 months of follow-up. New York Heart Association Functional Class improved an average of 1.28 classes per patient.

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

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

Fatigue-induced failure of the Ionescu-Shiley pericardial xenograft in the mitral position: In vivo and in vitro correlation and a proposed classification

Four patients had signs of primary bioprosthetic dysfunction within the fourth postoperative year after mitral valve replacement with an Ionescu-Shiley pericardial xenograft; they represent approximately 9% of patients with Ionescu-Shiley pericardial xenograft mitral valves followed up for more than 3 years at our institution. Pathological investigation showed severe incompetence of all explanted valves due to cusp tears and lacerations. Histologic study of the pericardial tissue disclosed mild to moderate collagen degeneration, without infection or calcification. Neoendothelial formation on the Dacron cloth of the sewing ring was either absent or minimal. The high incidence of valvular incompetence prompted us to try to establish a correlation between the in vivo and in vitro modes of failure of the Ionescu-Shiley pericardial xenograft. For this purpose, 10 unimplanted Ionescu-Shiley pericardial xenograft valves were tested in a fatigue test system. Severe fatigue-induced lesions occurred in this group after an average of 29.09 +/- 17.26 X 10(6) cycles; initial failure could be recognized in six of them after an average of 16.94 +/- 20.12 X 10(6) cycles. Valves tested in the fatigue test system showed tears and lacerations similar to those noted in the Ionescu-Shiley pericardial xenografts obtained from the four patients (which were assumed to have functioned for more than 100 X 10(6) cycles in each case). Correlation between results of the fatigue testing and our clinical experience enabled us to recognize four types of tears which may occur in the Ionescu-Shiley pericardial xenograft. The results of this investigation showed the following: (1) Primary tissue failure of the Ionescu-Shiley pericardial xenograft may occur suddenly. (2) A classification of tears occurring in Ionescu-Shiley pericardial xenograft valves is useful since the clinical presentation of patients may differ according to type and location of the lesion. (3) In the manufacture of pericardial valves, particular care must be observed in selection of the tissue and in the frame design. (4) Improvement of the quality control is one of the clues to enhance durability of the Ionescu-Shiley pericardial xenograft.