PubMed Health⌕ Search

Biomedical subjects

K Yasuura

Publications and source records attributed to K Yasuura.

At least 19 recordsLinked to original sources
PubMed2003

Bypass balloon pumping: a newly developed device for mechanical circulatory support in heart failure.

Various types of assist devices have been developed for severe heart failures. Among them, intra-aortic balloon pumping (IABP) has achieved popularity, mainly in the treatment of patients with either severe cardiac infarction or low cardiac output syndrome (LOS) after open-heart surgery. However, IABP has a limitation in that although it acts as a pressure support, it cannot directly support flow volume. In cases of severe pump failure, stronger pump support would be required. However, there is a limit in the clinical use of temporary mechanical support using a pump because of the costs of the expensive equipment. With this in mind, we came up with a new idea in which the motion of a balloon in IABP system is converted into a power source for creating a one-way stream. In order to realize our idea, we made a J-shaped sample model of pulsating chamber incorporating two ball valves. In the hydrodynamic experiment using our new device, flows over 2500 ml/min (Max. 3475 ml/min) were obtained. The percent changes in parameters such as TTI, DPTI and bypass flows obtained by the experiment of left ventricular bypass have demonstrated that our assist system is effective for reducing cardiac work.

Animals↗
PubMed2003

[Sequential bypass grafting with arterial grafts can be functioned? Assessment of evaluation for function of sequential bypass grafting from theoretical model].

As total arterial revascularization in coronary artery bypass grafting (CABG) has been recommended, a sequential bypass technique using arterial grafts has been induced. We evaluate whether a sequential bypass graft can be functioned or not by using a simple simulation model for coronary circulation analogous to the electrical circuit based on Ohm law. The ratio of flow between graft and native coronary artery was determined by the severity of stenosis in the bypassed vessels and the graft diameter. In selection for sequential bypass technique, these factors should be taken into consideration.

Arteries↗
PubMed2001

Transplantation of the en bloc vascular system for coronary revascularization.

OBJECTIVES: Use of the free gastroepiploic artery graft for coronary revascularization has not been very popular because of its inclination toward vasospasm. We hypothesized that the cause of free gastroepiploic artery spasm was the graft damage caused by an interruption of venous drainage from the graft. To solve this problem, we developed a new method of free gastroepiploic artery grafting. METHODS: From January 1997 to October 1999, 33 patients underwent coronary artery bypass grafting with the free gastroepiploic artery according to our new method. The gastroepiploic artery graft was harvested en bloc with its satellite veins. The gastroepiploic vein was anastomosed to the right atrial appendage for venous drainage simultaneously with the gastroepiploic artery being grafted in the aortocoronary position. RESULTS: A total of 96 distal anastomoses were performed, including 33 free gastroepiploic artery grafts according to our method, 33 in situ left internal thoracic artery grafts, 26 saphenous vein grafts, and 4 radial artery grafts. Neither operative nor hospital death occurred. Early postoperative angiography revealed that all of the 33 free gastroepiploic artery grafts performed with our method were patent without spasm, and flow competition occurred only in 2 of those grafts. On late angiography, all 15 free gastroepiploic artery grafts were patent without spasm. CONCLUSIONS: The free gastroepiploic artery grafting with venous drainage technique we developed can prevent graft spasm, leading to improved patency rate.

Adult↗
PubMed2001

[Pitfall in the choice of the in situ arterial grafts in OPCAB].

Flow capacity with arterial grafts which have been used in off-pump CABG has been discussed. To analyze the hypoperfusion syndrome when in situ arterial grafts are selected, we made the simple mathematical model which consisted of two vessels with in parallel. We speculated the flow capacity of the various grafts, and flow distribution in the distal coronary artery, based on Poiseuille's law. This theoretical model clearly demonstrated that hypoperfusion syndrome occurred in reoperative coronary bypass grafting had a close relation with the diameters and lengths of bypass grafts.

Blood Viscosity↗
PubMed2000

Theoretical analysis of right gastroepiploic artery grafting to right coronary artery.

BACKGROUND: The right gastroepiploic artery (GEA) has been used as the second reliable arterial graft for coronary artery bypass grafting (CABG). However, concern regarding the flow competition with the recipient coronary artery has remained. METHODS: An application of in situ GEA grafting to the right coronary artery (RCA) was studied by using a theoretical model. The theoretical model of CABG was given variables; ie, the diameters and the lengths of both in situ GEA and proximal segment of the RCA, and the degree of proximal stenosis in the RCA. According to the range of these variables obtained from clinical data, the ratio of the GEA flow to the flow of the RCA distal to the anastomosis was calculated. RESULTS: Main factors to determine the flows in the two parallel paths were the inner diameters of both vessels, and the degree of the proximal stenosis. When the inner diameters of the GEA were 0.5 mm larger than that of the RCA, the GEA carried more than 50% of the total flow of the RCA distal to the anastomosis despite a moderate stenosis in the RCA. When the inner diameter of the GEA was equal to, or 0.5 mm smaller than, that of the RCA, the GEA flow was dominated by the native RCA flow unless the proximal stenosis was critical. CONCLUSIONS: If the inner diameter of the GEA is 0.5 mm larger than that of the RCA, CABG with the GEA can be applied more widely. If not, the application would basically be limited.

Coronary Artery Bypass↗
PubMed2000

Maintenance of blood heparin concentration rather than activated clotting time better preserves the coagulation system in hypothermic cardiopulmonary bypass.

In cardiopulmonary bypass (CPB), despite heparin regimens in which the activated clotting time (ACT) is kept at more than 400 s, there is biochemical evidence of thrombin generation indicating activation of the coagulation system and increased fibrinolytic activity. Therefore, to reduce the coagulant activation has been one of the main issues in the improvement of CPB. The purpose of this study was to compare the heparin concentration with the ACT and to evaluate the effect of keeping higher heparin concentration on the coagulation and fibrinolytic systems during hypothermic CPB, employing moderate hypothermia (MHT) or deep hypothermic circulatory arrest (DHT). Heparin was either administered to maintain an ACT >400 s (ACT group) or to maintain a whole blood heparin concentration of 3 mg/kg (heparin group). At the lowest core temperature during CPB, the ACT and the heparinase ACT (unrelated to heparin concentration) were increased the most whereas the whole blood heparin concentration was less than half the initial concentration in both ACT groups of MHT and DHT. The thrombin-antithrombin III (TAT) content just after CPB in both MHT and DHT was significantly lower in the heparin group than in the ACT group. In conclusion, ACT does not reflect the whole blood heparin concentration during hypothermic CPB. Furthermore, maintenance of the higher heparin concentration during hypothermic CPB may suppress the activation of the coagulation system via thrombin inhibition. That effect was more remarkable in deep hypothermic CPB. Therefore, we believe that anticoagulation management during hypothermic CPB should be based on the maintenance of the higher blood heparin concentration.

Aged↗
PubMed2000

Repair of leaking postinfarction ventricular septal defect under circulatory arrest via left thoracotomy.

We treated a 60-year-old woman for postinfarction ventricular septal defect (VSD) and closed it by the infarction exclusion method. Postoperatively she was complicated by Candida sternal mediastinitis and residual shunt of VSD. After her sternal infection came under control we repaired the leaking VSD via left thoracotomy under hypothermic circulatory arrest. She recovered well and repair of the leaking VSD under circulatory arrest via left thoracotomy seemed to be a safe and promising alternative for VSD repair.

Blood Vessel Prosthesis Implantation↗
PubMed2000

Transfusion-associated graft-versus-host disease with transfusion practice in cardiac surgery.

BACKGROUND: Transfusion-associated graft-versus-host disease (TA-GVHD) in immunocompetent patients has still been underdiagnosed and underreported. Risk of TA-GVHD caused by transfusion practice in cardiac surgery should be appropriately recognized. METHODS: The correlation of TA-GVHD with transfusion practice in cardiac surgery was analyzed from our 17-year clinical experience. We retrospectively reviewed 2,686 consecutive adult patients who underwent cardiac surgery between 1980 and 1996. Classified according to transfusion practice, 847 patients (32%) received nonirradiated fresh homologous whole blood (mean per patient, 5+/-2 units) with or without other blood components; 592 patients (22%) nonirradiated stored RBCs older than 7 days (4+/-2), and 551 patients (21%) received irradiated homologous blood including, fresh whole blood (2+/-1), RBCs (4+/-1), and PCs (8+/-3), respectively. The remaining 696 patients (25%), did not require homologous transfusion. RESULTS: Four of 847 patients who received nonirradiated fresh homologous whole blood (< or =48 hours after donation) developed TA-GVHD. TA-GVHD did not occur in other patients. CONCLUSIONS: Our local experience demonstrates the incidence of TA-GVHD in patients who received fresh homologous whole blood in cardiac surgery was much higher, compared with previous reports. This result suggests that the frequency of TA-GVHD is nearly similar to the value calculated from the proportion of HLA haplotypes in the population.

Adult↗
PubMed1999

Protective effects of ONO-5046*Na, a specific neutrophil elastase inhibitor, on postperfusion lung injury.

BACKGROUND: Polymorphonuclear neutrophil elastase might contribute to postperfusion lung injury, so we evaluated the protective effect of ONO-5046*Na, a specific inhibitor of polymorphonuclear neutrophil elastase, against such an injury. METHODS: The study was done using 8 mongrel dogs that received ONO-5046*Na (15 mg/kg per hour) (group O) and 8 control dogs (group C), all of which had 1 hour of partial bypass and 5 hours of observation. RESULTS: The respiratory index showed no significant changes in group O, but increased significant in group C (1.4+/-2.0 versus 5.1+/-4.7, p = 0.0047). Pulmonary extravascular water volume increased markedly in group C but only slightly in group O (group C 20.6+/-8.7, group O 11.2+/- 2.7 mL/kg; p = 0.0005). Blood concentrations of polymorphonuclear neutrophil elastase and interleukin-6 showed more than a tenfold increase in group C (PMN elastase, group C 12.9+/-12.8, group O 2.4+/-1.3 ng/mL; IL-b, group C 11.0+/-9.3, group O 2.9+/-3.8 pg/mL; p < 0.05) but were only slightly higher in group O. Histologic examination revealed interstitial and intraalveolar edema in group C, but group O was virtually normal. CONCLUSIONS: ONO-5046*Na inhibits polymorphonuclear neutrophil elastase and maintains better pulmonary function, so it should reduce postperfusion lung injury.

Animals↗
PubMed1999

Comparative clinical study between retrograde cerebral perfusion and selective cerebral perfusion in surgery for acute type A aortic dissection.

OBJECTIVE: Selection of a brain protection method is a primary concern for aortic arch surgery. We performed a retrospective study to compare the respective advantages and disadvantages of retrograde cerebral perfusion (RCP) and selective cerebral perfusion (SCP) in patients who underwent surgery for acute type A aortic dissection. METHODS: The study reviewed 166 patients who underwent surgery at Nagoya University or its eight branch hospitals between January 1990 and August 1996. There were 91 patients who received SCP and 75 patients who underwent RCP. Results for these two groups were compared. RESULTS: There were no significant differences in age, gender, Marfan syndrome rate, DeBakey classification, or emergency operation rate. Rates of various preoperative complications were similar except for aortic valve regurgitation. Arch replacement was performed more often in SCP than in RCP patients (49% vs. 27%, P = 0.0028). There were no significant differences between groups in cardiac ischemic time or visceral organ ischemic time. However, RCP group showed shorter cardio-pulmonary bypass time (297+/-99 vs. 269+/-112 min, P = 0.013) and lower the lowest core temperature (21.6+/-3.1 degrees C vs. 18.7+/-2.1 degrees C, P = 0.0001). SCP duration was longer than RCP duration (103+/-56 vs. 54+/-24 min, P < 0.0001). Despite these differences, RCP patients were not significantly different from SCP patients with regard to any postoperative complication, neurological dysfunction (16 vs. 19%), or operative mortality (all deaths within the hospitalization; 24 vs. 21%). Regarding neurologic dysfunction, there were six cases of coma, six of motor paralysis, two of paraplegia and one of visual loss among SCP patients, and eight cases of coma, three of motor paralysis, and three of convulsion in the RCP group. The incidence of motor paralysis was higher in the SCP group, while the incidence of coma was higher in the RCP group. CONCLUSIONS: RCP can be performed without clamping or cannulation of the cervical arteries, which is an advantage in reducing the chances of arterial injury or cerebral embolization. RCP is comparable to SCP in terms of clinical outcome.

Acute Disease↗
PubMed1999

Effects of proximal ventricular septal pacing on hemodynamics and ventricular activation.

Recently the use of alternate site pacing to improve cardiac function in patients with bradyarrhythmias has increased. In the present study, hemodynamics of right ventricular septal pacing were studied in seven dogs. A bipolar screw-in lead and endocardial lead were placed in the proximal right ventricular septum and right ventricular apex, respectively. The right ventricle was paced from each site. A conductance catheter and Millar catheter were inserted into the left ventricle to determine the left ventricular pressure and the pressure-volume loop. Cardiac output was measured using the thermodilution method. In five of the seven dogs, ventricular activation was documented by isochronal epicardial activation mapping during each pacing mode. Mean arterial pressure and cardiac output during septal pacing were significantly higher than during apical pacing (110 +/- 17 mmHg vs 100 +/- 18 mmHg; 1.00 +/- 0.39 L/min vs 0.89 +/- 0.33 L/min). The positive dp/dt during septal pacing was significantly higher than during apical pacing (2137 +/- 535 mmHg/s vs 1911 +/- 404 mmHg/s). End-systolic elastance during septal pacing was significantly higher compared to apical pacing (13.1 +/- 0.3 mmHg/mL vs 8.9 +/- 4.0 mmHg/mL). The ventricular activation time during septal pacing was significantly shorter than during apical pacing. The epicardial maps generated during septal pacing were similar to those from atrial pacing. We conclude that hemodynamics and interventricular conduction are less disturbed by proximal right ventricular septal pacing than apical pacing in dogs with normal hearts.

Animals↗
PubMed1999

[The analysis for surgical procedures of coronary-artery bypass grafting: selection of graft materials].

We analyzed 222 patients undergoing coronary artery bypass grafting (CABG) in our institute. Our selection of graft materials consists of only one arterial conduit and one or more saphenous vein grafts (SVG). An arterial conduits (left internal thoracic artery (LITA) was mainly used for the left anterior descending coronary artery (LAD), while a SVG was used for coronary arterial branch. Our approach was evaluated by the mid-term prognosis as well as cardiac events. Seventy-one percent of patients with CABG could be followed. The graft patency rate was better for ITA grafts than for SVG (97.8% vs 88%). The incidence of late cardiac events was lower in patients with the LITA, to the LAD. Furthermore, these patients had a better survival rate at 4 years comparing with patients who had vein bypass grafts alone. We suggest that this selection of graft materials may be accepted in CABG for the good quality, avoiding the cardiac events.

Adult↗
PubMed1999

Transaortic approach for a closure of a residual ventricular septal defect of the tetralogy of Fallot.

BACKGROUND: A residual ventricular septal defect as part of the tetralogy of Fallot (TOF) is often difficult to close when a long interval has elapsed after a radical operation or the position of the defect is problematic. METHODS: When an accurate diagnosis and closure of a residual ventricular septal defect (VSD) were not obtainable through right atriotomy and right ventriculotomy, the ascending aorta was opened. The smooth surface of the left ventricular septum makes it possible to find the position of the defect, and close it accurately and safely. RESULTS: Three consecutive patients were operated upon using this method. They had undergone repair of tetralogy of Fallot anomalies 8 years, 26 years, and 21 years prior to this surgery, respectively. All patients survived the operation and were discharged from the hospital. None of the patients had residual defects, aortic regurgitation, or new atrioventricular block. CONCLUSIONS: This transaortic approach for closing residual ventricular septal defects related to the tetralogy of Fallot offers an alternate method when either the right atrial or right ventricular approach cannot be performed successfully. This approach may make it possible to close such defects directly.

Adult↗
PubMed1998

[Coronary artery bypass grafting in cases with poor left ventricular function].

From January 1987 through June 1992, 18 patients with poor left ventricular function (left ventricular ejection fraction [LVEF] less than 0.3) underwent elective isolated primary coronary artery bypass surgery. The mean age was 56.4 years (range, 46 to 72 years), and 15 were males and 3 were females. Mean pre-operative LVEF measured by ventriculography was 0.26 +/- 0.03 (range, 0.19 to 0.30). Sixteen patients (88.9%) had a prior myocardial infarction and 9 (50%) had a history of congestive heart failure. Complete revascularization was the goal for all patients, and the mean number of bypass grafts was 3.0 +/- 0.8 per patient. The left anterior descending coronary artery (LAD) was revascularized in all patients. There were no operative deaths. Post-operative LVEF improved significantly from 0.26 +/- 0.03 to 0.42 +/- 0.11 (p = 0.0002), and the regional left ventricular wall motion improved in the diaphragmatic and posterobasal regions (p < 0.01). The patency of the grafts was 93.9% in all, and 100% for LAD. The mean follow-up period was 77 months, and the overall actuarial survival rate was 88.9% at 10 years. During follow-up periods, two patients died of congestive heart failure (CHF), and two required three rehospitalizations because of CHF. The overall cardiac event free rate was 75.8% at 10 years. In patients with poor left ventricular function, surgical revascularization can be performed safely, but congestive heart failure sometimes occurs during follow-up periods and may be the cause of death. Therefore alternate forms of therapy such as cardiac transplantation and/or TMLR should be considered in selected patients.

Aged↗