Early experience with the mosaic bioprosthesis: a new generation porcine valve.

BACKGROUND: The Mosaic bioprosthesis is a new generation stented porcine valve. METHODS: Between May 1995 and April 1998, this valve was implanted in the aortic position in 98 patients (70 men; mean age, 69.2 years [34.2 to 83.6 years]). Preoperatively 35 patients were in New York Heart Association functional class 3 or 4. Fifty-nine patients underwent concomitant procedures. The mean duration at follow-up in January 1999 was 23.7 +/- 10.2 months (0.3 to 39.4 months) and totaled 193 patient-years. All but one survivor was in New York Heart Association class 1 or 2. RESULTS: Early complications included 1 death, 3 reoperations for bleeding, greater than mild regurgitation (paravalvar) in 1 patient and thromboembolism in 4 patients. Late complications included four deaths, study-valve endocarditis in 3 patients, more than mild regurgitation or hemolysis in 2, and thromboembolism in 2 patients. Late follow-up echocardiography in all survivors showed a mean transaortic gradient of 13.6 +/- 6.7 mm Hg, and an aortic valve area of 1.80 +/- 0.61 cm2. Valve replacement was followed by a significant and sustained decrease in left ventricular mass for all valve sizes. There has been no primary structural valve failure. CONCLUSIONS: The early experience with the Mosaic valve in the aortic position has been promising.

The medtronic intact porcine valve: ten-year clinical review.

OBJECTIVE: Our objective was to assess the long-term mortality and morbidity associated with the Medtronic Intact valve (Medtronic, Inc, Minneapolis, Minn). METHOD: Between 1983 and 1996, 447 patients (280 men and 167 women) received 466 Intact valves: 280 aortic, 156 mitral, and 30 tricuspid. The mean age was 57 years (median 63 years), with 45% younger than 60 years. The mean New York Heart Association class was 3.1. The follow-up was 98% complete and extended for 39 months (1-154 months) and 1324 patient-years. There were 32 valves at risk at 10 years after implantation. Doppler echocardiography was performed whenever possible in patients followed up for longer than 4 years (mean 8 years) after implantation. RESULTS: Ten-year overall actuarial survival was 30% +/- 6% (14% +/- 7% for New York Heart Association classes IV-V and 39% +/- 8% for classes I-III). At 10 years freedom from infective endocarditis was 92% +/- 3%, freedom from thromboembolism was 80% +/- 5%, and freedom from nonstructural valve deterioration was 95% +/- 2%. Ten-year freedom from explantation was 64% +/- 6%, freedom from valve-related events was 51% +/- 6%, and freedom from valve-related death was 88% +/- 3%. There were 26 examples of structural valve deterioration, mainly caused by leaflet calcification (in 17 cases) and by buttress detachment (in 6 cases). In the aortic position at 10 years freedom from structural valve deterioration was 81% +/- 9%, but with only 1 event in patients older than 40 years (freedom 92% +/- 8%) and 100% freedom in patients older than 60 years. There was also 100% freedom from structural valve deterioration in the tricuspid position. In the mitral position freedom was 65% +/- 8%, with no significant difference between age groups. CONCLUSION: The Intact valve provides superior results in the aortic position in patients older than 40 years and in the tricuspid position at all ages.

Long-term outcome after the mustard repair for simple transposition of the great arteries. 28-year follow-up.

OBJECTIVES: This study examines the late outcome in patients with simple transposition of the great arteries (TGA) after a Mustard operation. BACKGROUND: Continuing medical follow-up for patients after the Mustard procedure, now extending to three decades, is required. The quality of life of adult survivors has not been well documented. METHODS: Survival and quality of life among 113 hospital survivors of the Mustard operation performed for simple TGA between 1964 and 1982 were assessed by medical review and a lifestyle questionnaire. The incidence of right ventricular failure and echocardiographic right ventricular dysfunction (RVD) were determined. A measure of lifestyle, the ability index, was determined. RESULTS: Actuarial survival was 90%, 80%, and 80% at 10, 20, and 28 years, respectively, with 76% of survivors being New York Heart Association class 1. Sudden death, with an incidence of 7% without identifiable risk factors, was the most common cause of late demise. RVD was identified in 18% of patients who had echocardiography, but there was right ventricular failure in only two patients. Seventy-five percent of current survivors lead a normal life, 20% have some symptoms or lifestyle modification, and 5% are unable to work. CONCLUSIONS: The survival of patients to 28 years with the Mustard repair has been good. Late sudden death is the most worrisome feature. There is a 97% freedom from right ventricular failure to date. The quality of life of late survivors is good, most achieving a normal level of education and employment.

Age-dependent changes in the radial stretch of human aortic valve leaflets determined by biaxial testing.

The maximum radial elastic extensibility (stretch) of human aortic valve leaflets was measured as a function of the donor age using biaxial testing techniques. The 36 leaflets tested were removed from 18 unimplanted cryopreserved aortic allograft valves retrieved from donors aged 15 to 58 years. The stretch was measured at a traction of 60 Nm-1 and analyzed as a function of the age of the donor. It was found that at 15 years, the radial stretch is about 80% but declines rapidly (linearized rate of 4% per year) to be 40% by the age of 25 years. The stretch stays approximately constant until the age of 40 years and then undergoes a steady decline at the rate of about 1% per year at least until the age of 58 years. These results demonstrate that stretch, which is important for the maintenance of adequate coaptation area, is not permanent but may be lost at a relatively rapid rate for reasons that are not yet understood. Stretch loss in the leaflets also must be a contributing factor to the development of aortic incompetence. The probability of postoperative stretch loss needs to be allowed for in sizing protocols for aortic allografts.

Biaxial mechanical properties of explanted aortic allograft leaflets.

The leaflets of 33 aortic allograft valves inserted using the freehand method were retrieved at reoperation, and the mechanical properties of the tissue were measured using biaxial testing methodology. Before insertion, the valves had been sterilized for 24 hours in either PSKA or CLPVA antibiotic solutions and then were either wet stored or cryopreserved. The cryopreserved valves were sterilized with CLPVA only, so there were three different treatment types in all. The controls were a set of unimplanted cryopreserved aortic valves. The radial stretch of the valve leaflets was measured and was analyzed as a function of the age of the donor in the case of the controls and the age of the donor plus the duration of implantation for the explanted valves. The biaxial tension test was used to determine the maximum radial stretch of each leaflet because this variable dictates the area of coaptation and, ultimately, valve competency. It was found that the radial stretch of the allograft leaflets after implantation declined faster with time than did the stretch of the native aortic valve leaflet controls. This greater rate of stretch reduction depended mostly on the degree of similarity between the stretch of the donor leaflets and that of the recipient at the time of implantation. No conclusion could be reached about the influence of the preimplantation storage method because of the different time intervals of implantation applicable to each case. After matching for annulus size, matching the ages of donor and recipient is a good graft-selection strategy, but it may be better to use a slightly older donor.(ABSTRACT TRUNCATED AT 250 WORDS)

Mechanical properties of porcine pulmonary valve leaflets: how do they differ from aortic leaflets?

This study measured the biaxial properties of pulmonary and aortic leaflets in extension in the fresh state and then in the same samples after fixation with glutaraldehyde. The results showed that when fresh, the valves had a similar response to load in the circumferential direction, but the pulmonary leaflets were more extensible in the radial direction. They were also less stiff. Fixation decreased the tissue extensibility and increased the stiffness of the pulmonary leaflets much less than in the aortic leaflets. This was interpreted to mean that the collagen content of the pulmonary leaflets is significantly less than that in the aortic leaflets. Reduced collagen content would be expected to enhance hemodynamic performance because of increased leaflet stretch and reduced stiffness. However, lower collagen levels may reduce implant durability.

Outcome of pregnancy after the Mustard operation for transposition of the great arteries with intact ventricular septum.

OBJECTIVES: This study examined the outcome of pregnancy in patients with transposition of the great arteries and an intact ventricular septum after a Mustard operation. BACKGROUND: Before the introduction of surgical treatment, most children with transposition of the great arteries died in early infancy. A number of these patients have now reached their reproductive years. There is little information about the effect of pregnancy on cardiovascular status, particularly the ability of the right ventricle to adjust to the hemodynamic changes of pregnancy. The outcome for the offspring and their risk of congenital heart disease are also unknown. METHODS: Twenty-three female late survivors after the Mustard operation > 15 years of age were reviewed in relation to the occurrence of pregnancy and its outcome. Serial echocardiographic estimates of right ventricular volume during pregnancy were made in three local patients. RESULTS: Nine women had 15 pregnancies. They were asymptomatic before pregnancy and remained free from cardiac symptoms during each pregnancy. Right ventricular volume in the three patients studied increased during pregnancy but returned to normal at 8 to 11 weeks postpartum. There were 12 live births, 2 spontaneous abortions and 1 intrauterine death. None of the liveborn infants had evidence of congenital heart disease. CONCLUSIONS: In this small group of women with good quality late survival after a Mustard operation, pregnancy was well tolerated. We suspect that the incidence of congenital heart disease in infants of mothers with transposition of the great arteries will be at the lower end of the range for mothers with different types of congenital heart disease, but further data will be needed to confirm this.

What is the best bioprosthetic operation for the small aortic root?: allograft, autograft, porcine, pericardial? Stented or unstented?

Durability is assessed with regard to valve position, patient age, and the techniques of graft preparation for each of the tissue valves. Design affects both durability and the effective orifice area. It is assessed for each of the available devices, with particular emphasis on the stentless porcine valve. The effect that differences between this glutaraldehyde fixed device and the allograft valve may have on techniques of implantation is analyzed. On the basis of this information, an attempt is made to grade the currently available tissue valves with a satisfactory intermediate-term performance for use in the small aortic root.

Aortic valve replacement in the elderly.

Aortic valve replacement is an established mode of therapy that enhances and prolongs life in patients with significant aortic valve disease. This is true for the elderly, but with a higher reported mortality and morbidity than in younger patients. One hundred and eighty-three elderly patients aged 70 years and over were considered suitable candidates for isolated aortic valve replacement (n = 97) or aortic valve replacement combined with coronary artery bypass surgery (n = 86) in the decade 1980-89. The mean age at surgery was 73.2 years (70-80). The hospital mortality and morbidity of this group were compared to 340 consecutive patients aged 60-69 who underwent similar surgery over the same period. There was no significant difference in hospital mortality: 4.4% for elderly patients and 4.1% for those aged 60-69. Measures of hospital morbidity were similar except for the perioperative stroke rate, which was 4.4% in the elderly patients and 1.5% in the younger group (p < 0.05). Detailed long term follow up was obtained in 75 of the 76 elderly patients who underwent aortic valve replacement or aortic valve replacement combined with coronary artery bypass surgery in the first five year period. Hospital survival was 99% (one hospital death). The overall five year actuarial survival was 81% and greater than the age and sexmatched general population (73%). Of the 44 patients alive at the time of review, 35 (80%) were free of angina and 32 (73%) had no significant symptoms of heart failure. Additionally, these patients were questioned about their quality of life.(ABSTRACT TRUNCATED AT 250 WORDS)

The zero pressure fixed medtronic intact porcine valve: an 8.5 year review.

The Medtronic Intact valve is the only porcine valve which is fixed in glutaraldehyde at zero pressure. This preserves near normal extensibility of the leaflet collagen, enabling full leaflet opening without kinking, which in turn should improve durability compared with low and high pressure fixed valves. From 1983 to 1991, 265 patients had 276 Intact valves inserted (125 aortic, 129 mitral, 22 tricuspid). The mean age was 53 years (10-81), with 24% below 40 years. The 100% follow up represents 911 patient years and averaged 50 months (3-106) in survivors. The actuarial survival was 54% +/- 9% at eight years, compared with a matched general population of 82%. The mean NYHA class was 3.2 preoperatively and 1.2 at follow up. At eight years, freedom from infective endocarditis was 97% +/- 1%, from thromboembolism 89% +/- 3%, and from non-structural dysfunction 96% +/- 2%. Reoperation was required in three patients for infective endocarditis, in six for non-structural dysfunction and in seven for structural valve deterioration (SVD). Freedom from SVD in the aortic position (mean age 59 years) was 100%, in the tricuspid position (mean age 48 years) 80% +/- 7%. In the mitral position, freedom from SVD was 86% +/- 10% in patients aged 60 years or more (n = 39, two events), 96% +/- 4% in those aged 40-59 years (n = 23, one event in a patient with renal failure), 67% +/- 16% in those aged 20-39 years (n = 31, three events in two following pregnancy) and 38% +/- 28% in those under 20 years (n = 9, two events).(ABSTRACT TRUNCATED AT 250 WORDS)

The stentless bioprosthesis: surgical challenges and implications for long-term durability.

An attempt is made to analyse the factors which are expected to influence clinical results following implantation of a stentless porcine bioprosthesis. Long experience with implantation of allograft aortic valves provides a meaningful basis for comparison with a glutaraldehyde-fixed device. Morphological differences between the two valves involve the aortic wall and muscle shelf, and differences in valve preparation include the strength and stiffness of the aorta and the extensibility of the valve leaflets. As a result of these differences, sizing of the porcine valve is expected to be more critical than the allograft valve and the porcine valve is also expected to be more obstructive. Methods for reducing the obstructive element include the use of a composite aortic valve, a porcine pulmonary valve, or a valve in which the aorta is glutaraldehyde-fixed under pressure while the leaflets are pressure-free. The techniques available for implantation, namely freehand insertion, total root replacement and mini-root replacement, are examined.

Clinical experience with the zero-pressure-fixed Medtronic Intact bioprosthetic valve.

The Medtronic Intact porcine valve bioprosthesis was inserted in 219 patients between 1983 and 1990. Mean patient age was 52 years and mean follow up 33.3 months. There was only one example of structural valve degeneration at 25 months, giving an actuarial freedom of 99% at 6 years. Reoperation was performed in 7 patients. Freedom from reoperation was 93% at 6 years, from infective endocarditis 96%, from thrombo-embolism 91% and from valve-related complications 86%. Doppler echocardiography revealed non-significant incompetence in 8 instances and mild leaflet thickening of 5 valves. Valve gradients and areas were unchanged between two Doppler studies 2 years apart of valves in the mitral position, and were reduced in valves in the aortic position from 17 +/- 5.2 mmHg to 13 +/- 2.8 mmHg (P = 0.02). These medium-term results are considered very encouraging. The theoretical considerations underlying the use of zero-pressure glutaraldehyde fixation, which is the technique used for the Intact valve, are detailed elsewhere in this issue [1]. The Intact valve is treated with toluidine blue as a calcium-retarding agent and is mounted on a Dacron-covered acetyl copolymer (Celcon) stent with flexible posts. The normal profile of the porcine aortic valve is maintained.

Identification of a failure mode of the antibiotic sterilized aortic allograft after 10 years: implications for their long-term survival.

Freehand aortic allograft valves that had been previously sterilized with antibiotics were recovered at reoperation for biomechanical testing. The elastic extensibility of two leaflets from each explanted allograft stored in modified Hank's solution at 4 degrees C were measured using biaxial testing techniques. It was found that the leaflets had lost a significant amount of the natural, preimplant tissue extensibility. Computer simulation was used to investigate the likely consequences of such a profound change in the biomechanical characteristics of the leaflets on whole valve function. We found that the valve becomes progressively more incompetent as leaflet extensibility is lost and the stress levels at the commissures rise sharply with reduced coaptation. The stress levels in the load-bearing leaflet center are increased in the ventricularis as load is transferred from the fibrosa. The measured change in the radial extensibility of the aortic allograft leaflet needs to be allowed for when sizing the graft at insertion. Inserting the largest possible graft will maximize the time to the onset of central incompetence and improve valvar longevity by lowering the stress during diastole.

On stress reduction in bioprosthetic heart valve leaflets by the use of a flexible stent.

It has been postulated that flexible stent posts can reduce tensile stress at the commissures of tissue heart valves by about 90% when compared with the same valve mounted on a rigid stent. We have used a detailed computer model to investigate the role of flexible stent posts in reducing stress in the leaflets of three types of bioprosthetic heart valves: the bovine pericardial and the high- and zero-pressure fixed porcine valves. The models use stress/strain data from biaxial experiments to characterize the tissue properties and are subjected to a back pressure of 120 mmHg. We found that strain was reduced linearly with stent post deflection and that this was a purely static process--it did not require the load to be applied impulsively. This finding was in close agreement with earlier experimental studies, which measured the same strain reduction whether the valve was loaded quasi-statically or at physiological rates. In addition, we found that for this mechanism to be effective the valve must have good coaptation at the center and the tissue should be stiff; in other cases, the advantages of strain reduction through the use of a flexible stent are considerably diminished.

The zero pressure fixed medtronic intact porcine valve: clinical results over a 6-year period, including serial echocardiographic assessment.

Between 1983 and 1990, 219 patients had 224 Medtronic Intact porcine valves inserted. There were 94 aortic, 110 mitral, and 20 tricuspid valve replacements. The mean patient age was 52 years. Mean follow-up was 33.3 months and was 97.7% complete. There was only one example of structural valve degeneration occurring at 25 months, giving an actuarial freedom of 99% at 6 years. Reoperation was performed in seven patients. At 6 years, actuarial survival was 71%, freedom from infective endocarditis 96%, freedom from thromboembolism 91%, freedom from reoperation 93%, and freedom from valve-related complications 86%. Doppler echocardiography was performed in 48 of the 70 patients operated upon between August 1983 and October 1986 and who remained alive at the current review. Their follow-up averaged 4.7 (3-6.7) years. The results were compared to a similar examination performed in 1987 by the same operator. No patient had significant regurgitation. Valve gradients and areas remained the same in the two studies in the mitral position (3.8 +/- 1.33 mmHg) and the mean aortic gradient had reduced from 17 +/- 5.2 mmHg in 1987 to 13 +/- 2.8 mmHg in the current study (p = 0.02). These medium-term results are considered encouraging.

Rest and exercise hemodynamics of 20 to 23 mm allograft, Medtronic Intact (porcine), and St. Jude Medical valves in the aortic position.

Doppler echocardiography was used to measure gradients and valve areas at rest and after supine bicycle exercise in 35 patients with valve replacements 20 to 23 mm in size. Thirteen patients with a St. Jude Medical valve (St. Jude Medical, Inc., St. Paul, Minn.) were matched to 13 patients with an allograft valve, and seven patients with a Medtronic Intact (porcine) valve (Medtronic, Inc., Minneapolis, Minn.) to seven patients with an allograft valve. Patients were matched for age, sex, valve size, body surface area, and left ventricular systolic function. There was no statistically significant difference between the matched groups for body surface areas, resting cardiac output, exercise heart rate, or workload achieved. Mean pressure gradient was higher for St. Jude Medical than for allograft groups, both at rest (11.8 +/- 6.67 mm Hg for St. Jude Medical versus 6.67 +/- 2.98 mm Hg for allografts) and after exercise (16.4 +/- 8.47 mm Hg versus 9.7 +/- 3.94 mm Hg), but the differences were of borderline significance (p = 0.016 and 0.027, respectively). Valve area at rest was similar for both devices (1.4 +/- 0.45 cm2 for St. Jude Medical versus 1.8 +/- 0.56 cm2 for allograft; p greater than 0.1). There were highly significant differences between patients with Intact and those with allograft valves for resting mean pressure gradient (19.3 +/- 4.23 mm Hg for Intact versus 5.9 +/- 3.68 mm Hg for allograft; p less than 0.001) and for exercise mean pressure gradient (27.8 +/- 8.63 mm Hg versus 8.1 +/- 8.43 mm Hg; p less than 0.001). The differences between the valve areas at rest also were significant (1.1 +/- 0.12 cm2 versus 2.2 +/- 0.62 cm2; p less than 0.01). It is concluded that when a tissue valve is indicated in patients with a small aortic root, the freehand allograft aortic valve is an ideal device from the hemodynamic perspective and is superior to the Intact valve. It is also probably superior in this respect to the St. Jude Medical valve, although the analysis may be biased slightly in favor of the allograft valve.

Use of aortic valve allografts from hepatitis B surface antigen-positive donors.

Over a 28-month period, 31 patients undergoing aortic valve replacement received valve allografts from hepatitis B surface antigen-positive, hepatitis B e antigen-negative donors. At the time of operation, 22 recipients were immune to hepatitis B infection; 19 had antibodies to hepatitis B surface antigen, and 3 were hepatitis B surface antigen positive. Nine patients were regarded as being susceptible to hepatitis B; 7 lacked hepatitis B markers, and records of serological status could not be found for the other 2. Four of the susceptible patients received hepatitis B immunoglobulin postoperatively, and 1 of them also received one 10-micrograms dose of hepatitis B vaccine. The 9 susceptible patients underwent hepatitis B serological studies a mean of 17 months (range, 4 to 31 months) postoperatively. In only 1 patient, tested 29 months after operation, had antibodies to hepatitis B surface, hepatitis B core, and hepatitis B e antigens developed. He had not experienced a clinical episode of hepatitis, and results of liver function tests were normal. He had not received prophylaxis. Because hepatitis B virus may be transmitted by hepatitis B surface antigen-positive, hepatitis B e antigen-negative valves, prophylaxis should be given whenever they are used and follow-up serological studies undertaken.