Stentless bioprosthetic valves have been implanted for treatment of aortic valve disease, especially in elderly patients ; these valves have the advantage of durability and excellent hemodynamics compared with stented bioprosthetic valves. Although good long-term results in patients with stentless bioprosthetic valves have been reported recently, reoperation has been gradually increasing. We performed reoperation for the SJM Toronto SPV and Medtronic Freestyle valves in one patient each. The SJM Toronto SPV was used in a 30-year-old woman ; however, 8 years later, the valve showed severe calcification and adhesions, and could not be completely removed (Case 1). The other reoperation case, wherein a 69-year-old man underwent aortic valve replacement with the Medtronic Freestyle 4 years previously, showed no adhesion around the implanted valve, which could be easily removed from the autologous aortic annulus. Consequently, the first patient required reimplantation of a small mechanical valve (SJM #19). In contrast, we were able to use a stentless bioprosthetic valve (Prima Plus #23) for the second patient. Further observations on stentless bioprosthetic valves are required.

Prosthetic and bioprosthetic materials currently in use lack growth potential and therefore must be repeatedly replaced in pediatric patients as they grow. Tissue engineering is a new discipline that offers the potential for creating replacement structures from autologous cells and biodegradable polymer scaffolds. In May 2000, we initiated clinical application of tissue-engineered vascular grafts seeded with cultured cells. However, cell culturing is time-consuming, and xenoserum must be used. To overcome these disadvantages, we began to use bone marrow cells, readily available on the day of surgery, as a cell source. Since September 2001, tissue-engineered grafts seeded with autologous bone marrow cells have been implanted in 44 patients. The patients or their parents were fully informed and had given consent to the procedure. A 3 to 10ml/kg specimen of bone marrow was aspirated with the patient under general anesthesia before the skin incision. The polymer tube serving as a scaffold for the cells was composed of a copolymer of lactide and ε-caprolactone (50: 50) which degrades by hydrolysis. Polyglycolic or poly-l-lactic acid woven fabric was used for reinforcement. Twenty-six tissue-engineered conduits and 19 tissue-engineered patches were used for the repair of congenital heart defects. The patients' ages ranged from 1 to 24 years (median 7.4 years). All patients underwent a catheterization study, CT scan, or both, for evaluation after the operation. There were 4 late deaths due to heart failure with or without multiple organ failure or brain bleeding in this series; these were unrelated to the tissue-engineered graft function. One patient required percutaneous balloon angioplasty for tubular graft-stenosis and 4 patients for the stenosis of the patch-shaped tissue engineered material. Two patients required re-do operation; one for recurrent pulmonary stenosis and another for a resulting R-L shunt after the lateral tunnel method. Kaplan-Meier analysis in relation to patients' survival was 95% within 3 years. There was only 1 patient (who underwent a total cavo-pulmonary connection procedure) requiring re-intervention in the tubular graft group and the material-related event-free rate was 96% within 3 years. This tissueengineering approach may provide an important alternative to the use of prosthetic materials in the field of pediatric cardiovascular surgery. As it is living tissue, these vascular structures may have the potential for growth, repair, and remodeling. However, this approach is still in its infancy, further studies to resolve the problems presented, and longer follow-up in patients are necessary to confirm the durability of this approach.

A 61 year old woman who had been receiving treatment for ulcerative colitis for 14 years complained of respiratory discomfort on exertion and was diagnosed with severe mitral regurgitation due to mitral valve prolapse. Minimally invasive mitral valvuloplasty with right mini-thoracotomy was performed in our facility. Laboratory findings showed elevated levels of serum creatine kinase (CK) and CK-MB immediately after surgery. In addition to elevated levels of myocardial enzymes, ST depression was seen in an electrocardiogram on postoperative day 2 ; therefore, we suspected myocardial ischemia during the surgery. Despite the persistently elevated levels of myocardial enzymes, coronary angiography showed no significant abnormalities. Because of the possibility of false CK elevation, we performed CK electrophoresis, which revealed the presence of macro-CK type 1. CK-MB activity is often falsely elevated when determined by immune-inhibition in macro-CK patients, and that leads to the suspicion of myocardial ischemia. We considered that it may be highly difficult to identify macro-CK in a patient after cardiovascular surgery owing to elevated levels of myocardial enzymes in most such patients.

We report a case of redo mitral valve replacement (MVR) for a Björk-Shiley Delrin valve implanted 47 years previously. A 71-year-old man initially underwent MVR for mitral regurgitation at our hospital at the age of 16 years. Following the operation, follow-up examinations were performed at the outpatient clinic and annual transthoracic echocardiogram findings showed only mild mitral regurgitation, with no adverse events noted. However, a transthoracic echocardiogram examination performed 45 years after the operation revealed mild to moderate mitral regurgitation, while dyspnea with exertion was also noted at that time. As part of a more detailed examination, transesophageal echocardiogram results showed moderate transvalvular leakage. Redo MVR was subsequently performed under the diagnosis of prosthetic valve dysfunction. Analysis of the explanted prosthetic valve revealed wear of the Delrin disk, and widening of the gap between the disk and strut, which were presumed to be the cause of transvalvular leakage. A half century has passed since introduction of the Björk-Shiley valve and the present is a rare case of valve malfunction. Presented here are related details, along with a review of existing literature and results of Björk-Shiley valve use at our hospital.