Long-term results of mechanical valves in aortic position and biological valves in mitral and tricuspid positions

The long-term results of patients undergoing aortic valve replacement (AVR) with a mechanical valve (AM), mitral valve replacement with a biological valve (MB), and tricuspid valve replacement (TVR) with a biological valve (TB) operated upon from 1977 to 1988 were retrospectively analysed. A total of 899 patients received 1117 valves (381 AM, 633 TB, 103 TB) with a follow-up 3778 patient-years and 4582 valve-years. A significant incidence of thromboembolism, hemorrhage, and endocarditis was not found among AVR, MVR, TVR, or multiple valve replacement. We found a significantly decreased incidence of survival rate in multiple valve replacement compared with AVR or MVR, and a significantly increased incidence of reoperation in MB compared with AM and TB. We use AM and TB in any adult patients as a first choice. However, we prefer a mechanical valve in the mitral position except in patients over 65 years old, who have a short life expectancy, in whom anticoagulation is thought to be difficult, and who desire a biological valve.     

Vascularized synovial flap promoting regeneration of the cryopreserved meniscal allograft: experimental study in rabbits

 The purpose of this investigation was to evaluate whether a vascularized or free synovial flap or a fibrin clot can promote regeneration of meniscal allograft in the rabbit. Seventy-eight mature New Zealand white rabbits were used. The harvested medial meniscus for the allotransplantation was frozen and stored at −80°C for 2 weeks. After resecting the medial meniscus, an allogenic meniscus was transplanted in the anatomical position (group A). The surface of the graft was covered by a vascularized synovial flap (group B), a free synovial flap (group C), or a fibrin clot (group D). The animals were killed 4, 6, 8, 12, and 16 weeks after transplantation, and the transplants were examined by gross inspection, histology, and microangiography. Connective tissue infiltration into the matrix of the graft was found to begin at 6 weeks (2/5 menisci) and to be complete at 8 weeks (5/5 menisci) in group B, whereas it began at 8 weeks (1/5) in group A. The newly formed repair tissue developed from the synovial tissue and consisted of connective tissue at the beginning and fibrocartilage later. The fibrocartilage had appeared at 8 weeks (3/5) in group B but not yet in group A (0/5). A free flap or fibrin clot coverage resulted in delayed revascularization compared to a vascularized synovial flap, but both tended to achieve faster revascularization than the controls. We concluded that regeneration of allografted meniscus with a vascularized synovial flap occurs earlier than under other conditions. Thus, allografts with synovial implantation may be considered for management of the meniscectomized knee. Received: October 18, 2001 / Accepted: September 27, 2002 Offprint requests to: K. Yamazaki     

Implantation of sensory nerve into flap: an experimental study and clinical application]

Experimental implantation of sensory nerve into flaps was done, with the purpose of restoration of sensation of the flaps. A scanty amount of nerve endings were found in the vicinity of the implantation after 2 months, obvious regeneration was observed after 3 months, and never endings similar to normal after 4 months. Sensory nerve was implanted into flaps in the hands and feet of 25 patients. 1-2 year follow-up showed that pain, temperature and tactile sensations recovered to normal, and two-point discrimination was 11-22 mm in the hands and 35-40 mm in the feet. In 3 patients, the implanted nerves were blocked with procaine, and anesthesia of the flaps ensued, thus it was proved that the flaps were innervated by the implanted sensory nerves.     

Articular cartilage restoration in load-bearing osteochondral defects by implantation of autologous chondrocyte-fibrin constructs: an experimental study in sheep

Ovine articular chondrocytes were isolated from cartilage biopsy and culture expanded in vitro. Approximately 30 million cells per ml of cultured chondrocytes were incorporated with autologous plasma-derived fibrin to form a three-dimensional construct. Full-thickness punch hole defects were created in the lateral and medial femoral condyles. The defects were implanted with either an autologous 'chondrocyte-fibrin' construct (ACFC), autologous chondrocytes (ACI) or fibrin blanks (AF) as controls. Animals were killed after 12 weeks. The gross appearance of the treated defects was inspected and photographed. The repaired tissues were studied histologically and by scanning electron microscopy analysis. All defects were assessed using the International Cartilage Repair Society (ICRS) classification. Those treated with ACFC, ACI and AF exhibited median scores which correspond to a nearly-normal appearance. On the basis of the modified O'Driscoll histological scoring scale, ACFC implantation significantly enhanced cartilage repair compared to ACI and AF. Using scanning electron microscopy, ACFC and ACI showed characteristic organisation of chondrocytes and matrices, which were relatively similar to the surrounding adjacent cartilage. Implantation of ACFC resulted in superior hyaline-like cartilage regeneration when compared with ACI. If this result is applicable to humans, a better outcome would be obtained than by using conventional ACI.     

Assessment of the Melody valve in the mitral position in young children by echocardiography

Objectives

Mitral valve replacement (MVR) in young children is limited by the lack of small prostheses. Our institution began performing MVR with modified, surgically placed, stented jugular vein grafts (Melody valve) in 2010. We sought to describe key echocardiographic features for pre- and postoperative assessment of this novel form of MVR.

Haemodynamic and echocardiographic characteristics of a stentless allograft mitral prosthesis: an in vitro study

Poor long-term durability and impaired haemodynamic performance are known disadvantages of bioprosthetic heart valves when compared to valve replacement using aortic allografts. A new stentless allograft mitral implant was developed and tested in vitro in a left ventricular model and pulsatile flow system to evaluate hydrodynamic function. Mitral valves were excised from sheep hearts and the mitral annulus reinforced by a strip of ovine pericardium. A patch of expanded polytetrafluoroethylene (ePTFE) was placed above the tips of the remaining papillary muscles. For in vitro evaluation of a total of five valves were investigated in a pulse duplicator. Transvalvular pressure gradients (ΔP) were measured over a flow range corresponding to a cardiac output of 51/min, at a heart rate of 70 beats/min, with a systole accounting for approximately 35% of the cardiac cycle. The systolic ejection period and diastolic filling period in this model were 350 and 510 ms, respectively, and aortic pressure was 120/80 mmHg. The effective orifice area was calculated from measurements of mean pressure drop and root mean square flow. Additionally, valve performance was evaluated by Doppler echocardiography. Results of in vitro studies of a 25 mm stentless allograft mitral implant, which is similar to the valves implanted in a chronic weanling sheep model, revealed a mean(s.d.) ΔP of 2.0(1.6) mmHg (range 1.0 – 4.9 mmHg). The mean calculated effective orifice area was 3.38(0.52) cm² (range 2.5 – 3.8 cm²). Doppler echocardiography showed excellent performance of the mitral valve components and valve competence could be achieved. During the in vitro studies no failure caused by tissue rupture was detected. The results of the in vitro studies revealed data for ΔP and effective orifice area superior to data obtained for standard 25 mm porcine bioprostheses.     

Prosthesis of mitral valve in mesenchimal dysplasia: anatomo-morphological aspects and technical specificities

Pathomorphological aspects of acquired mitral defects of the heart caused by manifestations of mesenchimal dysplasia were studied in 100 patients. Special attention is given to important features of surgical strategy when performing mitral valve prosthesis in such patients unlike similar procedures for mitral defects of another etiology.     

Articular cartilage degeneration after frozen meniscus and achilles tendon allograft transplantation: experimental study in sheep

Purpose: The purpose of this study was to analyze cartilage degeneration in knees after total medial meniscectomy, transplantation of fresh-frozen meniscus allograft, and Achilles tendon allograft. Type of Study: Experimental study. Methods: We have studied the articular cartilage in the medial compartment of the left knees in 32 sheep aged 5 to 6 months, with 8 animals in each group. The study was performed after meniscectomy (group I), transplantation of fresh-frozen meniscus allograft (group II), use of fresh-frozen Achilles tendon allograft (group III), and in a control group (group IV). For the histologic study, all samples were stained with Masson’s trichrome and Safranine-O. Mankin’s score was applied to grade the histologic damage to the articular cartilage. Results: The group with the greatest number of degenerative changes was group III, followed by groups I and II. The percentage of thickness of cartilage detected by Safranine-O stain was found to be significantly different in both tibia and femur between the control group and the other 3 groups, but not among groups I, II, and III. The immunoreactivity of the articular surfaces in tibia and femur showed notable differences in all the groups. Collagen X was present in the degenerative hypertrophic chondrocytes in the damaged articular surfaces. Conclusions: Meniscal replacement with meniscal and Achilles tendon allografts provides partial protection against articular damage after a meniscectomy.     

Surgical strategy for severe tricuspid valve regurgitation complicated by advanced mitral valve disease: long-term outcome of tricuspid valve supra-annular implantation in eighty-eight cases

OBJECTIVE: Although annuloplasty has been the most commonly performed surgical modality for severe tricuspid regurgitation, tricuspid valve supra-annular implantation has been performed in our hospital for more than a decade. The aim of this study was to assess the long-term outcome of tricuspid valve supra-annular implantation in a subgroup of patients with severe tricuspid regurgitation, those who also had advanced mitral valve disease. METHODS: Mitral valve replacement in conjunction with tricuspid valve supra-annular implantation was performed on 88 patients at our hospital between 1984 and 1998. The patients (mean age 57 +/- 11 years) were followed up for an average of 7.2 +/- 4.5 years after the operation (range 0-14 years); total follow-up was 643.1 patient-years. All patients except 2 (97.6%) were included in the follow-up. We evaluated the mortality, the cause of death, survival, the freedom from structural valve deterioration and reoperation, postoperative complications, and long-term echocardiographic findings. RESULTS: Overall survival at 14 years was 69% +/- 7.7%. Freedom from structural valve deterioration at 14 years was 100% and from reoperation, 88% +/- 9. 4%. There were no instances of pulmonary thromboembolism or of complications associated with fatal arrhythmias. Echocardiography showed little residual tricuspid regurgitation, no atrophic and stenotic change in the native tricuspid valve, and no thrombus formation between native valve and the implanted bioprosthesis. CONCLUSIONS: The procedure's simplicity, the good long-term durability of the bioprosthesis, and the absence of fatal arrhythmias and pulmonary thromboembolism indicate that tricuspid valve supra-annular implantation is a useful procedure for patients with severe tricuspid regurgitation complicated by advanced mitral valve disease.     

Healing of wound sutures on the mitral valve: an experimental study

Objective The aim of this study was to examine the histopathological changes that occur during the heading process of a sutured wound on the mitral valve. Methods In 12 mongrel dogs, an incision was made at a right angle to the annulus at the center of the free edge of the anterior mitral leaflet and then sutured. Animals were killed 2–16 weeks later and the wounds were examined histologically. Results Two weeks after the operation, fibrin thrombi were found on the atrial surfaces of the wound, and organized thrombi became part of the neointima thereafter. There were capillaries in the thrombi, but only a few extended from the valvular ring. On the ventricular surfaces, fibrous neointima extending from adjacent intima without capillary proliferation covered the wound at 2 weeks. These heading processes started from the valvular ring side of the wound. Processes were delayed near the free edge area, and myxomatous granulation tissue extended from the adjacent spongiosa. There were abundant collagen fibers obscuring the suture line at 4 weeks in the basal region and at 12–16 weeks near the free edge. Calcified deposits with cartilage were found in a thick scar in the basal region at 4 weeks and extended to the central area thereafter. Conclusion The healing of mitral valvular wounds is slow, especially near the free edge area. The wound is covered by organized thrombi at the atrial surface and by fibrous sheaths at the ventricular surface. These processes should be taken into consideration during the patients’ care after valvoplasty, especially during the first several months after surgery.     

Severe tricuspid regurgitation after mitral valve surgery: the risk factors and results of the aggressive application of prophylactic tricuspid valve repair

Purpose

This study aimed to examine the risk factors for severe postoperative tricuspid regurgitation (TR) in patients undergoing mitral valve surgery. We also studied the effects of prophylactic tricuspid valve repair (TVR) on severe postoperative TR.

Methods

We retrospectively studied 125 patients without severe TR who underwent mitral valve surgery from 1987 to 2006. Patients did not undergo TVR before 1998 (the early period, n = 54). In 1998 (the late period, n = 71), patients with a preoperative tricuspid annular diameter of ≥35 mm underwent TVR using an annuloplasty ring (n = 52).

Results

In the analysis of the early period, the rates of freedom from severe TR at 10 and 20 years after surgery were 76 and 59 %, respectively. A multivariate analysis identified moderate preoperative TR as a significant risk factor for severe TR. In the late period, none of the 52 patients who underwent TVR developed severe TR. However, 4/19 patients who did not undergo TVR developed severe TR, and all of these four patients had a preoperative tricuspid annular diameter of ≤35 mm.

Conclusions

Moderate preoperative TR is a significant risk factor for severe postoperative TR in patients undergoing mitral valve surgery. The aggressive application of TVR can prevent severe postoperative TR; however, tricuspid annular dilatation might not be a good indicator for TVR.

     

Abdominal aortic reconstruction in infected fields: early results of the United States cryopreserved aortic allograft registry

OBJECTIVE: Aortic reconstructions for primary graft infection (PGI), mycotic aneurysm (MA), and aortic graft-enteric erosion (AEE) bear high morbidity and mortality rates, and current treatment options are not ideal. Cryopreserved grafts have been implanted successfully in infected fields and may be suitable for abdominal aortic reconstructions. Registry data from several institutions were compiled to examine results of cryopreserved aortic allograft (CAA) placement. METHODS: The experience of 31 institutions was reviewed for CAAs inserted from March 4, 1999, to August 23, 2001. Indications for CAA, organisms, mortality, and complications were identified. RESULTS: Fifty-six patients, 43 men and 13 women, with a mean age of 66 years (range, 44 to 90 years) had in situ aortic replacement with CAA. Indications for CAA placement were PGI in 43 patients (77%), MA in seven (14%), AEE in four (7%), and aortic reconstruction with concomitant bowel resection in two (4%). Infectious organisms were identified in 33 patients (59%); the most frequent organism was Staphylococcus aureus in 17 (52%). Thirty-one patients (55%) needed an additional cryopreserved segment for reconstruction. The mean follow-up period was 5.3 months (range, 1 to 22 months). One patient died in the operating room, and the 30-day surgical mortality rate was 13% (7/56). Seven additional patients died during the follow-up period, yielding an overall mortality rate of 25% (14 patients). Two patients (4%) had graft-related mortality as the result of hemorrhage from the CAA and persistent infection. Graft-related complications included persistent infection with perianastomotic hemorrhage in five patients (9%), graft limb occlusion in five (9%), and pseudoaneurysm in one (2%). Three patients (5%) needed amputation. CONCLUSION: In situ aortic reconstruction with CAA in infected fields carries a high mortality rate, but most deaths are not the result of allograft failure. However, CAA infection and lethal hemorrhage caused by graft rupture occurs and is concerning. Early reinfection was not reported. Late graft-related complications, such as reinfection, thrombosis, or aneurysmal changes, are unknown. Preliminary data from this registry fail to justify the preferential use of CAA for PGI, MA, or AEE. A multicenter, randomized study is needed to compare results with established techniques.     

Elevated position of the irrigation outflow during arthroscopy: an experimental study

The purpose of this study was to investigate different types of irrigation systems and to record pressures and flows in a joint model. Gravity inflow and three different pumps were compared, and the level of the outflow in relation to the model was tested. Flow rates of 100-200 ml/min and pressures ranging from negative to 100 mm Hg were found. There were minor differences between the irrigation systems, mainly concerning safety aspects. Elevated position of the outflow could be of value in controlling and optimizing pressures and flows during arthroscopy.