The Cryolife-O'Brien stentless aortic porcine xenograft valve

Decellularized Human Dermis for Orthoplastic Extremity Reconstruction

The reconstruction of patients who possess multi morbid medical histories remains a challenge. With the ever-increasing number of patients with diabetes, infections, and trauma, there is a consistent need for promotion of soft tissue healing and a reliable substrate to assist with every aspect of soft tissue reconstruction, as well as the loss of fascial domain. Several proprietary products filled some of these needs but have failed to fulfill the needs of the clinician when faced with reconstructing multiple soft tissue systems, such as the integument and the musculoskeletal system. In this paper we discuss the use of decellularized human dermis (DermaPure®, Tissue Regenix, Universal City, TX, USA) through which a unique human tissue processing technique (dCELL® technology, Tissue Regenix, Universal City, TX, USA) and the creation of multiple product forms have proven to exhibit versatility in a wide range of clinical needs for successful soft tissue reconstruction. The background of human tissue processing, basic science, and early clinical studies are detailed, which has translated to the rationale for the success of this unique soft tissue substrate in orthoplastic reconstruction, which is also provided here in detail.

Early Hemodynamic Results of the Shelhigh SuperStentless Aortic Bioprostheses

BACKGROUND

Stentless valves have been demonstrated excellent hemodynamic performances favoring the recovery of left ventricular function and the ventricular hypertrophy regression. The aim of the study was to evaluate the early hemodynamic performance of the Shelhigh SuperStentless aortic valve (AV).

METHODS

Between July 2003 and June 2005, 35 patients (18 females; age 70.8 +/- 11.7 years, range: 22-85) underwent AV replacement with the Shelhigh SuperStentless bioprostheses. Most recurrent etiology was senile degeneration in 25 (71%) patients and 24 (69%) were in New York Heart Association (NYHA) functional class III or IV. Concomitant coronary artery bypass grafting was performed in nine patients (25.7%) and mitral valve surgery in two patients (5.7%). Doppler echocardiography was performed before surgery, at six-month and one-year follow-up.

RESULTS

There were no hospital deaths and no valve-related perioperative complications. During one-year follow-up, no endocarditis or thromboembolic events were registered, no cases of structural dysfunction or valve thrombosis were noted. Mean and peak transvalvular gradients significantly decrease after AV replacement, with an evident reduction to approximately 50% of the preoperative values at six months. A 20% reduction was also observed for left ventricular mass (LVM) index at six months, with a further regression at one year. Correspondingly, significant increases in effective orifice area (EOA) and indexed EOA were determined after surgery (0.87 +/- 0.14 versus 1.84 +/- 0.29 cm2 and 0.54 +/- 0.19 versus 1.05 +/- 0.20 cm2/m2, respectively). Valve prosthesis-patient mismatch was moderate in five patients and severe in one case.

CONCLUSIONS

Shelhigh SuperStentless AV provided good and encouraging hemodynamic results. Long-term follow-up is necessary to evaluate late hemodynamic performance and durability of this stentless bioprosthesis.

"Less stented" bovine pericardial xenograft: a new concept

The in vitro hemodynamic behavior of a bovine pericardium xenograft with discontinuity of the annular support, named the "Less Stented" bovine pericardial xenograft, was analyzed. A "Less Stented" bovine pericardial xenograft consisting of a glutaraldehyde-treated bovine pericardium prosthesis manufactured in Braile Biomédica Ltd, São José do Rio Preto, São Paulo, Brazil, was used according to the same protocols of the stented bioprosthesis manufacturer. Bovine pericardial xenografts were tested in a pulse simulator and analyzed in a cardiac simulator, with respect to the transvalvular gradient, regurgitant fraction and leakage volume, discharge coefficient, performance, and efficiency index. Analyses were performed by Pearson's correlation test and simple linear regression. The transvalvular gradients ranged between 6.37 and 11.62 mm Hg with a mean flow between 4.39 and 7.96 L/min, giving a good correlation (0.8291) on the regression curve with an increase in flow. The regurgitant fraction ranged between 10.95 and 17.94% and leakage volume between 4.49 and 7.87%. The discharge coefficient, performance, and efficiency index showed favorable behavior with the flow increase, with good correlation coefficient (0.9385, 0.9332, and 0.9024, respectively). The initial results of the "Less Stented" bovine pericardial xenograft size 25 analyses demonstrated a satisfactory in vitro performance. Evaluations of the hemodynamic performance of small size "Less Stented" bovine pericardial xenograft should be made to clarify the biological behavior of this new xenograft.

Technique for implant of the stentless aortic valve Freedom Solo

In this presentation we provide a summary of aortic valve replacement with a supra-annular stentless aortic valve, the Freedom Solo prosthesis. Stentless valves were designed to provide more physiological flow and lower transvalvular gradient, which is offered by the novel design of the valve and by its implantation technique. The supra-annular stentless aortic valve implantation is demonstrated with a special emphasis on its surgical technique peculiarities.

Novel Geometries for Tissue-Engineered Tendonous Collagen Constructs

A promising approach to addressing the performance limitations of currently available mechanical and bioprosthetic heart valves lies in tissue engineering. Tissue-engineered valves should incorporate the complex microstructure of the native valves to mimic their unique mechanics. This would include a layered topology, mesh networks, and branched collagen fiber bundles. Our approach to heart valve tissue engineering is to develop the functional components of the aortic valve cusps separately in vitro and, once they are mature, integrate them into a composite valve structure. Here we report on our efforts to create more complex collagenous structures, suitable for heart valve tissue engineering. Collagen fiber bundles were fabricated using the principle of directed collagen gel contraction, using neonatal rat aortic smooth muscle cells and acid-soluble type I rat-tail tendon collagen. The collagen gels were cast into rectangular or branched wells with porous end holders that constrained the gels longitudinally but allowed contraction to occur transverse to the long axis. Pairs of such constructs were placed in direct contact with each other and cultured further to determine whether they integrated to form continuous tissue. After 6-8 weeks of culture, highly compacted and aligned collagen fiber bundles formed. Mechanical testing revealed that linear constructs (2 free ends) with an 8:1 aspect ratio were significantly stronger than similar constructs with an aspect ratio of 2:1 (mean +/- SD, 298 +/- 90 kPa vs. 152 +/- 49 kPa; p < .001). Branching reduced mechanical strength considerably. Constructs fabricated with 4 free ends were significantly weaker than constructs with 3 ends (31 +/- 32 kPa vs. 116 +/- 66 kPa; p < .003). Histologic images demonstrated the integration of the crossed collagen bundles, with a bonding strength of 2.1 +/- 1.1 g (0.02 N). We found that the geometry of the molds into which the collagen constructs are cast can greatly affect their mechanical strength: multibranched constructs were the weakest, and long, linear constructs were the strongest. We also found that integration of collagen constructs occurs in vitro and that the fabrication of a composite structure in vitro is probably feasible.

Eight-year results after aortic valve replacement with the CryoLife-O'Brien Stentless Aortic Porcine Bioprosthesis

OBJECTIVE

The long-term durability and hemodynamics of stentless valves are largely unknown. In this study we prospectively analyzed 8-year clinical results with the CryoLife-O'Brien Stentless Aortic Porcine Bioprosthesis (CryoLife Inc, Kennesaw, Ga) and assessed its hemodynamic performance by serial echocardiography.

METHODS

A total of 206 patients with a mean age of 72.8 years were followed up prospectively after aortic valve replacement with the CryoLife-O'Brien stentless bioprosthesis. Patients have been followed up from 2 to 96 months for mean 56 months. Echocardiography was performed by a single echocardiographer preoperatively, intraoperatively, postoperatively at discharge, 3 to 6 months later, and annually thereafter.

RESULTS

The 30-day operative mortality was 4.8%. Sixty-five percent of patients received a valve 25 mm in diameter or larger, and 37% underwent concomitant coronary bypass grafting. Twelve late deaths, none valve-related, have occurred. Severe aortic insufficiency caused by oversizing led to early reoperation in 3 patients. The peak and mean systolic gradients decreased significantly during the first 12 months after implantation (P < .001), and the effective valve areas increased significantly during this interval (P < .001). At 8 years, 2 patients have mild to moderate aortic insufficiency. The actuarial survival at 8 years was 82% +/- 3%. The freedom from endocarditis was 100%, and the freedom from thromboembolic events was 93%.

CONCLUSION

Despite more demanding surgical technique than with conventional bioprostheses, the CryoLife-O'Brien bioprosthesis can be implanted safely in a population predominantly older than 70 years at the time of the operation, with excellent measures of hemodynamics, clinical outcomes, prosthesis durability, and survival through 8 years.

Single–suture line placement of a pericardial stentless valve

OBJECTIVE

Implantation of bioprostheses in the supra-annular position with the single suture line was first applied by O'Brien to porcine stentless valves. The aim of this study was to evaluate the clinical performance of the Pericarbon Freedom stentless bioprosthesis (Sorin Biomedica Cardio, Saluggia, Italy) implanted in supra-annular position with the single-suture line technique. The single-suture approach for the Pericarbon Freedom stentless bioprosthesis is obtained by trimming away all the extra tissue of the valve inflow side and scalloping the outflow side.

METHODS

Between February 2002 and August 2004, a total of 65 consecutive patients at our institution (48% male, mean age 69 +/- 12 years) underwent aortic valve replacement with Pericarbon Freedom stentless bioprostheses implanted with a single suture line. Most recurrent etiology was senile degeneration (80%). Pericarbon Freedom 25-mm and 27-mm valves were the most frequently implanted. Thirty patients had concomitant procedures (mainly coronary artery bypass grafting, 16 patients). Overall crossclamp time was 76 +/- 21 minutes.

RESULTS

All patients survived intervention. One patient died early of multiorgan failure (postoperative day 16). There were 4 early non-valve-related complications and no late complications at a mean follow-up of 491 +/- 270 days. Four patients showed trivial central prosthetic regurgitation at intraoperative transesophageal echocardiography; among these cases, only 1 was confirmed at 6-month transthoracic echocardiography. At postoperative echocardiographic assessment, mean pressure gradient for the 25- through 29-mm size group was 10.2 +/- 7.1 mm Hg, and peak pressure gradient was 18.1 +/- 12.3 mm Hg.

CONCLUSION

Our initial experience combined a well-established supra-annular implantation technique with the Pericarbon Freedom stentless bioprosthesis, a latest-generation pericardial stentless valve. The combination showed excellent results in terms of safety and reliability, although this technique required adequate experience. Clinical outcomes are similar to those obtained with other techniques, with satisfactory hemodynamic performance.

Heart Valve Tissue Engineering

Tissue-engineered heart valves have been proposed by physicians and scientists alike to be the ultimate solution for treating valvular heart disease. Rather than replacing a diseased or defective native valve with a mechanical or animal tissue-derived artificial valve, a tissue-engineered valve would be a living organ, able to respond to growth and physiological forces in the same way that the native aortic valve does. Two main approaches have been attempted over the past 10 to 15 years: regeneration and repopulation. Regeneration involves the implantation of a resorbable matrix that is expected to remodel in vivo and yield a functional valve composed of the cells and connective tissue proteins of the patient. Repopulation involves implanting a whole porcine aortic valve that has been previously cleaned of all pig cells, leaving an intact, mechanically sound connective tissue matrix. The cells of the patients are expected to repopulate and revitalize the acellular matrix, creating living tissue that already has the complex microstructure necessary for proper function and durability. Regrettably, neither of the 2 approaches has fared well in animal experiments, and the only clinical experience with tissue-engineered valves resulted in a number of early failures and patient death. This article reviews the technological details of the 2 main approaches, their rationale, their strengths and weaknesses, and the likely mechanisms for their failure. Alternative approaches to valvular tissue engineering, as well as the role of industry in shaping this field in the future, are also reviewed.

Midterm Results After Aortic Valve Replacement With a Stentless Bioprosthesis Aortic Valve

BACKGROUND

It is suggested that a simplified implant model Cryolife-O'Brien (CryoLife International, Kennesaw, GA) offers less satisfactory outcome compared with standard stentless models. This study was conducted to prospectively evaluate the midterm results after aortic valve replacement with the Cryolife-O'Brien stentless bioprosthesis.

METHODS

In 1996, a prospective clinical trial using different stentless valves was initiated. From September 1996 through September 2002, 156 consecutive patients with a mean age of 74.5 years underwent aortic valve replacement with the Cryolife-O'Brien porcine stentless bioprosthesis. The predominant aortic valve lesion was stenosis in 128 and insufficiency in 28 cases. Patients have been followed from 2 to 72 months (mean, 42 months). Echocardiography was performed by one echocardiographer preoperatively, intraoperatively, postoperatively at discharge, 2 to 6 months later, and annually thereafter.

RESULTS

Sixty percent of patients received a valve 25 mm in diameter or larger; 39% had concomittant coronary bypass grafting. The 30-day operative mortality rate was 6.4%. Ten late nonvalve-related deaths have occurred. Severe aortic insufficiency caused by oversizing leads to early reoperation in 3 patients. The peak and mean systolic gradients decreased significantly during the first 12 months after implantation, p < 0.001, and the effective valve areas increased significantly during this time interval p < 0.001. At 5 years, ten patients have moderate aortic insufficiency. The actuarial survival at 5 years was 88 +/- 3%. The rate for freedom from endocarditis was 100% and for freedom from thromboembolic events was 94%.

CONCLUSIONS

Midterm results after aortic valve replacement with the Cryolife-O'Brien stentless bioprosthesis are encouraging. Good hemodynamics have been coupled with low rate of valve-related complications, thus representing a very good alternative to conventional stented bioprostheses.

CryoLife-O'Brien Stentless Valve: 10-Year Results of 402 Implants

BACKGROUND

This truly stentless porcine valve is composite, without Dacron, and implanted supra-annularly. Ten-year analysis with magnetic resonance imaging is presented.

METHODS

From 1992 to 2002, 402 patients (mean 73.5 years) had aortic valve replacement. Associated procedures were required in 252 patients (63%). Serial echoes provided 1340 studies. Clinical follow-up was 100%. Magnetic resonance imaging focused on aortic annulus extensibility.

RESULTS

The 30-day mortality was 0.99% (4 deaths). Morbidity comprised thromboembolism (40 patients including 18 patients with permanent strokes); endocarditis (9 patients); and reoperation (9 patients [periprosthetic leak, 2; endocarditis, 5; technical needle damage, 1; and structural degeneration, 1]). Of 402 valves more than 10 years, five valves were explanted, one only for structural failure. Except for endocarditis (2 patients), no late deaths (69 patients, 1.5 months to 5.7 years) were valve related. Echocardiography demonstrated low gradients with good orifice areas, excellent ventricular regression (p = 0.0001 preoperative and postoperative comparisons) and late incompetence (mild in 45 patients and moderate in 9 patients). No living patient has severe incompetence. Magnetic resonance imaging demonstrated the annulus 'expanding and relaxing' throughout the cardiac cycle, the mean increase in cross-sectional area being 37%, resembling normal aortic root dynamics.

CONCLUSIONS

Elderly patients received this hemodynamically acceptable valve with its simple, supra-annular implantation and satisfactory mid-term morbid-free lifestyle to 10 years maximum follow-up. With only one structural failure, restoration of valve annular extensibility may have a favorable influence on long-term durability.

The evolution of bioprosthetic heart valve design and its impact on durability

Bioprosthetic heart valves have evolved over the years into remarkably useful and predictable devices. During this process, a number of specific designs have come and gone, and a few have remained. Many design changes were successful, and many were not. This article will describe the successes and failures of the various bioprosthetic valve designs and will detail the specific reasons why a particular design change succeeded or failed to improve bioprosthetic valve performance.

The stentless xenograft aortic valve: The wheel turns around

BACKGROUND

A brief overview of the historical pathways of both stented and stentless porcine xenografts is presented in order to understand the return to and continuing clinical use of stentless devices. In addition, 7-11 years of durability with various models of stentless porcine valves has now accumulated and is beginning to be of relevance in determining the future place of this xenograft. Stentlessness and anticalcium agents, coupled with the poor results of stented xenografts in certain patient groups, have led to a resurgence of the clinical use of stentless xenograft valves for aortic valve replacement. An overview of the present state and future of stentless valves is given.

METHODS

At both The Prince Charles Hospital and St Andrew's War Memorial Hospital, Queensland, Australia, 307 patients have received the Model 300 CryoLife-O'Brien stentless composite aortic xenograft from December 1992 to February 2000. Associated procedures were required in 56% of patients (mostly coronary artery bypass, mean 2.4 grafts, in 144 patients (47%) and left ventricular myomectomy in 34 patients (11%)).

RESULTS

The hospital mortality (four early deaths) has been 1.3 +/- 1% (CL 95%) and the follow-up 100% for this analysis. The mean patient age was 73 years (range 57-89 years with 16% being 80 years and over). Morbid events have included six perivalvar leaks: four trivial and identified only on echo Doppler (no clinical murmurs) and two patients requiring reoperation at 10 days and 12 weeks with simple successful repair verified on subsequent echocardiograms. Of the 307 patients over the 7 year period, three valves only have been explanted, two for endocarditis at 1.5 and 3.5 years and one for possible technically induced structural failure at 15 months (probable needle damage). With this exception, there has been as yet no other intrinsic leaflet failure. Four early thromboembolic events (4 days-5 weeks) in patients with atrial fibrillation (no anticoagulants used postoperatively with the first 80 patients) constituted the important early morbid events. Late mortality of this elderly patient cohort has occurred in 27 patients over 7 years of maximum follow-up. One death (endocarditis) has been valve related at 5 years. Serial echocardiography (some 700 echoes in the study of this valve) has demonstrated a mean gradient of 7-9 mmHg with a very low incidence of trivial incompetence (96%) on Doppler examination with implant valve sizes ranging from 21 to 29 mm. One patient had significant regurgitation requiring reoperation. There has been no progression of either incompetence or stenosis of the remaining patients in this follow-up, now into the eighth postoperative year.

CONCLUSION

The early and intermediate results appear excellent in this elderly patient cohort. Nevertheless, important surveillance is obviously required to determine the durability at 10-12 years, a crucial time when stented porcine xenografts began to show an obvious failure rate from structural deterioration, in the middle and elderly aged patient cohort. An attempt is made to outline the future of this type of stentless xenograft and to justify that its cautious use should probably be extended down to the over 50 year age patient cohort.

Symptomatic calcific stenosis of a Toronto stentless porcine valve

We describe the calcific structural failure of a Toronto stentless porcine valve (TSPV) which had been used to replace a calcified bicuspid aortic valve in a 46-year-old man. Against expectations, left ventricular hypertrophy persisted and the transvalvular pressure gradient rose to 125 mmHg by 6 years with the patient becoming symptomatic and requiring redo surgery. On removal the TSPV showed atypical calcification of the leaflet hinges and wall. To our knowledge this is the first case reported and it may have implications for long term durability and future surgery using this prosthesis.