川人 宏次

狭小大動脈弁に対する各種19mm機械弁の遠隔期心機能および予後について検討した.1990年から2002年9月までに施行した単独大動脈弁置換術(AVR)295例中で大動脈弁狭窄症(AS)に対し19mm機械弁を使用した46例を対象とし, 予後について検討した.また, 5年以上経過した25例中22例(5∿9年 : 12例, 10年以上 : 10例)に心臓超音波検査を施行した.左室駆出率(LVEF), 左室拡張末期短経(LVDd), 後壁厚(PWT), 心室中隔厚(IVST), 人工弁圧較差(PG)をそれぞれ計測し左室心筋重量(LVm), 左室心筋重量係数(LVMI)を算出し, 術前と遠隔期での結果を比較検討した.平均観察期間は63.1±43.5カ月.在院死亡はなく, 10年生存率が81.4%と良好であった.心機能に関しては保たれNYHAの悪化もなかった.また, 遠隔期に25.0mmHg程度のPGの残存を認めたもののLVm, LVMIの有意な減少を認めた.比較的高齢者や女性が多く, 体表面積(BSA)が小さいこと, 日常生活での運動負荷が少ない患者が多かったことが要因とも考えられるが, 狭小大動脈弁患者の多くは, 小柄な高齢女性であることから, 19mmサイズの弁置換術でも遠隔期のquality of lifeは保たれると思われた.

Background. In regard to postoperative bleeding, the most important consequence of cardiopulmonary bypass (CPB) is the loss of aggregability. However, the mechanism of platelet aggregation loss during CPB is unclear. Newly developed particle-counting methods that use light scattering can be used to quantify changes in the number of platelet aggregates of different sizes after application of an aggregating stimulus. Using a lightscattering method, we investigated changes in platelet aggregation during cardiac operation. Methods. Nineteen patients undergoing CPB were evaluated. Blood samples were obtained before the operation, 1 hour after initiation of CPB, at the end of CPB, at the end of the operation, and on day 1 after the operation. Platelet aggregation after stimulation by 2.5 mu mol/L adenosine diphosphate and 2.0 mu g/mL collagen was determined; small (9 to 25 mu m), medium (25 to 50 mu m), and large (50 to 70 mu m) aggregates were counted. Results. Generation of medium and large aggregates after stimulation with adenosine diphosphate and collagen were significantly decreased with CPB, whereas, in spite of hemodilution, the quantity of the small aggregates was maintained at the elevated level. Conclusions. These results reflect the fact that CPB does not affect the first phase of aggregation. It suggests that platelet dysfunction associated with CPB is mainly caused by an inhibition in the development of small aggregates into larger aggregates. (C) 1999 by The Society of Thoracic Surgeons.

術中予期せぬ弓部大動脈近傍の大血管損傷により, 修復に超低体温循環停止法 (一部逆行性脳灌流法を併用) を用いた5例について検討した. 症例の内訳は出血性損傷3例, 急性解離2例であった. 修復および手術遂行に要した体外循環時間は159～367分 (平均199分), 循環停止時間は20～44分(平均32分), 循環停止温度は膀胱温19.5～22.0℃ (平均21.0℃), 脳保護補助手段として逆行性脳灌流法を2例に使用した. 術後覚醒までの時間は持続鎮静降圧療法を施行した症例1を除き4～9時間で, 全例神経学的合併症はみられず退院した. 超低体温循環停止法は, (1) 血管壁の緊張緩和. (2) 良好な無血視野. (3) 自己血回収が可能. (4) 低体温による臓器保護. などの利点がある. 従って本法は弓部大動脈近傍の大血管損傷の修復に際して, 重大な合併症を回避しうる可能性があり, 遮断鉗子下での修復が困難な場合には速やかに選択すべき方法と考えられた.

CAPIOX EBS is a newly developed heparin-coated system for percutaneous cardiopulmonary support. Ten patients were assisted by this system after cardiac surgery because of low cardiac output syndrome in our institute, and 18 kits of CAPIOX EBS were installed in these patients. Non of the 18 kits showed any troublesome within 24 h of circulatory assist, but 6 kits were replaced over 36 h of circulatory assist because of hemolysis, annoying noise from the pump, or impaired oxygenation. Out of these 6 kits, two pumps revealed blood clot formation at the outlet and another two oxygenators showed plasma leakage. The mean running period of the other twelve kits was 142h (2-194h), and they did not show any functional waning. We needed 5 to 10 min for kit exchange, and hemodynamic deterioration during the procedure was minimal, and all patients requiring a new kit regained stable hemodynamic state immediately after kit exchange.

待機的腹部大動脈瘤 (AAA) 手術53例が対象で, 術前自己血非貯血群31例 (A群) と400ml貯血群22例に分類した. 貯血群は, B群12例 (Fe投与) と, C群10例 (FeとrHuEPO投与) に分類した. 以上3群について, 出血量, 輸血量, 同種血無輸血率, Hb値の推移について検討した. 次に, 最大瘤径7cm以下の43例とそれより大きな10例に分け, 同様の検討を加えた. 全例に術中自己血回収装置を使用した. A群, B群, C群間に年齢, 性差, 手術時間, 出血量, 輸血量に差はなかった. A群では250±370mlの同種血を, B群, C群では400mlの貯血自己血を輸血した. 同種血無輸血率は, A群58%, B群100%, C群100%であった. 術直前Hb値は, 自己血貯血に伴いB群で低下, C群では変わらなかった. 術後最低Hb値はC群で高かった. 瘤径の大小による差はなかった. 術前自己血400ml貯血により, AAA手術における同種血輸血は100%回避でき, rHuEPO併用により, より安全な手術が可能と考えられた.

We introduce the computer technology to enable an accurate, efficient, and reliable design process of an implantable axial flow VAD. The device design is computer-modeled with a parametric solid modeler. To eliminate the high negative pressure area, we performed computational fluid stress analysis on pump design. To improve efficiency and anti-thrombogenicity, CFD (computational fluid dynamics) study is performed to determine pressure and velocity of the fluid in the pump and eliminate the stagnant areas. Machining paths for prototype fabrication are generated using CAM software. And they are machined using CNC (computer numerically controlled) milling machine. Hemolytic characteristics was dramatically improved to 0.002g/100L of normalized index of hemolysis. Total system efficiency was improved to 14%. And Ex vivo 2 week implantation demonstrated excellent anti-thrombogenicity. The use of the CAD/CAM/CAE made it possible to develop a VAD rapidly and successfully.

A small ventricular assist device intended for long-term implantation has been developed by a cooperative effort between the Baylor College of Medicine and the NASA/Johnson Space Center. To date, in vitro tests have been performed to address hemolysis and pump performance issues. In this Phase 1 study, we assessed the durability and atraumatic features aiming for 2 day implantation. Eight pumps were implanted in 2 calves as paracorporeal left ventricular assist devices. The pump running times ranged from 18 to 203 h (78.1 +/- 23.7; mean +/- SEM). All the pump implantations were terminated because of thrombus formation. Plasma-free hemoglobin levels were below 13.7 mg/dl, except for 1 case complicated by inflow cannula obstruction. The pump speed was maintained between 10,100 and 11,400 rpm. Pump outputs were from 3.6 to 5.2 L/min. The electrical power required by the system ranged between 9 and 12 W. Clinically there was no detectable organ dysfunction noted, and postmortem evaluation demonstrated no pump related adverse effects in either calf except for small kidney infarctions. Thrombus deposition was observed mainly at the hub portions and the now straightener.