Osamu Ishii

Endothelialized networks with a vascular geometry in microfabricated poly(dimethyl siloxane).

One key challenge in regenerating vital organs is the survival of transplanted cells. To meet their metabolic requirements, transport by diffusion is insufficient, and a convective pathway, i.e., a vasculature, is required. Our laboratory pioneered the concept of engineering a vasculature using microfabrication in silicon and Pyrex. Here we report the extension of this concept and the development of a methodology to create an endothelialized network with a vascular geometry in a biocompatible polymer, poly(dimethyl siloxane) (PDMS). High-resolution PDMS templates were produced by replica-molding from micromachined silicon wafers. Closed channels were formed by bonding the patterned PDMS templates to flat PDMS sheets using an oxygen plasma. Human microvascular endothelial cells (HMEC-1) were cultured for 2 weeks in PDMS networks under dynamic flow. The HMEC-1 cells proliferated well in these confined geometries (channel widths ranging from 35 μm to 5 mm) and became confluent after four days. The HMEC-1 cells lined the channels as a monolayer and expressed markers for CD31 and von Willebrand factor (vWF). These results demonstrate that endothelial cells can be cultured in confined geometries, which is an important step towards developing an in vitro vasculature for tissue-engineered organs.

Efficacy of pulmonary vein isolation for the elimination of chronic atrial fibrillation in cardiac valvular surgery

BACKGROUND Haissaguerre and colleagues emphasize the importance of the pulmonary veins as a source of ectopic foci for initiating paroxysmal atrial fibrillation (AF). We hypothesized that ectopic foci from the pulmonary veins could also act as drivers for maintaining chronic AF, and that surgical ablation of the pulmonary vein orifices could terminate chronic AF. METHODS Using a computerized 48-channel mapping system, we performed intraoperative atrial mapping in 12 patients with chronic AF associated with mitral valve disease. Patient age ranged from 24 to 82 years (mean, 60.4 years). AF duration ranged from 3 to 240 months (mean, 92+/-84 months). Simple surgical isolation of the pulmonary vein orifices was performed during the mitral valve operation. RESULTS Regular and repetitive activation was found in the left atria of 9 out of 12 patients, and irregular and chaotic activation was found in both atria of 3 out of 12 patients. Chronic AF in the 9 patients (75%) with regular and repetitive activation of their left atria was successfully treated by a simple surgical isolation of the pulmonary vein orifices. The other 3 patients did not recover sinus rhythm after this procedure. In 1 case of recurrent AF, the patient recovered sinus rhythm during the follow-up period (AF-free rate, 83%). CONCLUSIONS Surgical ablation of the pulmonary vein orifices was effective in the treatment of chronic AF associated with mitral valve disease. Intraoperative mapping may be useful in predicting the efficacy of a single pulmonary vein orifice isolation procedure.

Endovascular stent-grafting via the aortic arch for distal aortic arch aneurysm : an alternative to endovascular stent-grafting

OBJECTIVE We have experienced transaortic stent-grafting for treating distal arch aneurysm or type B dissection. This paper is to mainly report the surgical aspect of these procedures. METHODS Fifteen patients underwent this surgery, including 12 men and three women ranging from 47 to 83 years. Twelve had aneurysms and three aortic dissection. Concomitant surgery was necessary in seven patients (coronary artery bypass grafting in five, tricuspid annuloplasty in one, and replacement of ascending aorta and/or total arch replacement in three cases). A stent graft (Gianturco Z-stent and Intervascular prosthesis) was loaded in a 30-F sheath catheter. Under circulatory arrest, selective cerebral perfusion was established, and the sheath catheter was inserted through aortotomy into descending aorta and the stent graft was deployed at an appropriate level. The proximal end of graft was sutured to the aorta just distal to the left subclavian artery with inclusion method at the posterior wall. Concomitant surgery was done during cooling or rewarming period. TEE was utilized to visualize every endovascular manipulation to avoid unintended intimal injury or misplacement of graft and to assess the surgical results in the operative theater. RESULTS Aneurysm was successfully excluded except in one patient who had a proximal endoleak and distal endoleak due to underestimation of aortic diameter. There was one operative mortality caused by cerebral infarction, possibly due to debris from femoral arterial cannulation. In the remaining patients, there was no enlargement of residual aneurysm. The excluded aneurysmal sac gradually regressed and disappeared within 2 years in five patients and the thrombosed false lumen completely shrunk within 1 year in two patients. One patient had paraplegia, possibly because the graft was intentionally advanced deeply to cover the thick and fragile atheromatous layer in order to avoid destruction of the atheroma by an expanded graft. CONCLUSIONS Endovascular stent graft via the aortic arch is an acceptable treatment for distal arch aneurysms close to or involving left subclavian artery or type B dissections, especially for those cases requiring other cardiac procedures. It can lead to regression and disappearance of aneurysm or dissection in the mid-term follow-up.

Cardiac Papillary Fibroelastoma on the Mitral Valve

A 68-year-old male had dysphagia and an esophageal tumor was visualized by gastrc-esophagocamera. Preoperative transthoracic echocardiography revealed a finger-size mass (1 0 mm X 10 mm) in the left ventricle (Fig. 11, diagnosed as a cardiac tumor and he was referred to our hospital. lntraoperative transesophageal echocardiography (TEE) demonstrated a heterogeneous mobile mass measuring approximately 1 X 1 cm in the left ventricle. The mass was attached to the anterolateral papillary muscle by a short stalk. After a median sternotomy, cardiopulmonary bypass using bicaval cannulas with moderate hypothermia was instituted. The ascending aorta was cross-clamped, and cardiac arrest was obtained. A left ventricular vent was not inserted in order to avoid intraoperative embolic episodes. An incision initially was made in the right side of the left atrium to vent the left ventricle through the mitral valve. The left ventricular cavity was not observed through this incision because the left atrium was

Postoperative Hypoxia in Obese Patients following Coronary Artery Bypass Grafting.

体外循環手術後の低酸素血症を予測する因子について検討した. 術後人工呼吸器から離脱可能であったCABG単独症例53例を対象とした. 実測70%以上の高濃度酸素吸入を必要とした症例群 (H群)29例と70%以下の酸素吸入を行った群 (L群) 24例について周術期おける各種因子との関係について検討した (H群vs L群). 術前因子では body mass index (25.6±3.5vs. 23.3±2.8, p=0.012) がH群において有意に高値であった. Respiratory index は両群ともに体外循環前後で低下するがH群においてはとくに抜管後より低下遷延していた. H群中3例は再挿管を要し全例晩期死亡した. 肥満例 (BMI≥26.5) では周術期を通じ有意にRIは低下遷延していた. 術前より低酸素血症を予測する因子は乏しいが肥満症例に対しては厳重な呼吸管理が要求されると思われた.