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Biomedical subjects

S Kawada

Publications and source records attributed to S Kawada.

At least 19 recordsLinked to original sources
PubMed2005

Excitation of toroidicity-induced Alfvén eigenmodes by the electrodes inserted in a heliotron/torsatron plasma.

A novel method of exciting shear Alfvén waves using electrodes inserted in a plasma was developed for basic study of Alfvén eigenmodes in a heliotron/torsatron plasma. The electrodes can induce excitation current along the confinement field line, and generate magnetic perturbations perpendicular to the confinement field. By sweeping the frequency of the current in a cold plasma, the toroidicity-induced Alfvén eigenmode was resonantly excited at the predicted frequency and radial location. Plasma response to the applied magnetic perturbations indicates a fairly large damping rate caused by continuum damping.

Journal Article↗
PubMed2001

Surgical treatment for a ruptured thoracic aortic aneurysm.

OBJECTIVE: The treatment for a ruptured thoracic aortic aneurysm remains controversial. This study was undertaken to assess the outcome from surgery. METHODS: Between 1993 and 1998, we have performed 19 operations for a ruptured thoracic aortic aneurysm. Patients with an impending rupture or a chronic false aneurysm were excluded. There were 11 men and 8 women, with a mean age of 70.5 +/- 6.7 years. The aneurysm was caused by dissection in 8 patients. Of these, 7 were acute (Stanford type A, 6; type B, 1), and the other one was chronic (type B). Aortic rupture occurred into the pericardial cavity (n = 7), into the left lung (n = 6), the mediastinum (n = 3), the pleural cavity (n = 2), or into the esophagus (n = 1). Severely unstable hemodynamics were noted in 12 patients with a rupture into the pericardium, mediastinum, or pleural cavity (Group A). Inotropic support was required in each of these patients. Metabolic acidosis developed all but 1 patient. The 7 patients with a rupture into the lung or esophagus coughed or vomited blood (Group B). The operative approach was anterior (n = 17) or lateral (n = 2). Grafts were placed in the ascending aorta (n = 4), ascending and transverse arch aorta (n = 7), transverse arch aorta (n = 3), or in the descending thoracic aorta (n = 5). Selective cerebral perfusion was used in 13 patients. RESULTS: There were 5 hospital deaths (26.3%). The postoperative complications included central nervous system dysfunction (n = 3), low cardiac output syndrome or cardiac arrhythmias (n = 3), respiratory failure (n = 4), acute renal failure (n = 1), and local or systemic infections (n = 4). The perioperative event-free rate was 36.8% overall, 25% in Group A, and 57.1% in Group B. CONCLUSIONS: Patients with unstable hemodynamics require prompt operative intervention. Rupture into the esophagus is associated with a high mortality rate. Rupture in a thoracic aortic aneurysm can be successfully treated with emergency surgery.

Aged↗
PubMed2001

Optimal positioning of temporary epicardial atrial pacing leads after cardiac surgery.

OBJECTIVES: Atrial pacing plays an important role in preventing low output syndrome and arrhythmia after cardiac surgery. We studied the optimal positioning for temporary epicardiac atrial pacing. METHODS: The performance of temporary epicardiac atrial pacing leads was examined after 13 cases of elective coronary artery bypass grafting between October 1999 and January 2000. Two bipolar electrode leads were used--1 on the cephalic atrial wall between the left and right atrial appendages, where the Bachmann bundle indwells (site A), and the other on the interatrial groove (site B). To assess pacing performance on postoperative days 1, 2, and 7, we measured 3 pacing patterns--bipolar use of sites A and B leads, and combined use of the 2 with the site A lead acting as the negative electrode and the site B lead as the ground. The pacing threshold was measured at a 0.5 ms pulse width, using the P wave amplitude and slew rate as indicators of sensing performance. RESULTS: Bipolar pacing both at sites A and A-B was superior to that at site B in pacing threshold and sensing parameters. CONCLUSIONS: The negative electrode at site A is mandatory for high atrial pacing and sensing performance.

Cardiac Pacing, Artificial↗
PubMed2001

Port-access cardiac surgery. Experience with 34 cases at Keio University Hospital.

OBJECTIVES: We reviewed our experience with port-access cardiac surgery and evaluated the medical effects and benefits of this technique in view of postoperative quality of life and medical expenses incurred during hospitalization. METHODS: From June 1998 to August 2000, port-access cardiac surgery was conducted on 34 patients--22 with atrial septal defect, 6 with mitral regurgitation, 2 with coronary artery disease, 2 with partial endocardial cushion defect, 1 with ventricular septal defect, and 1 with atrial and ventricular septal defects. Two types of endoaortic-balloon catheters were used to execute aortic cross-clamping. Skin incisions were 5 cm long. RESULTS: No hospital or late deaths were observed. Patients with atrial septal defect were discharged on postoperative day 3.7, patients of mitral regurgitation on postoperative day 4.2, and patient of ventricular septal defect on postoperative day 4.0 on the average. None were readmitted. Patients appeared undisturbed by early discharge and were able to resume physical work on day 22 on the average after discharge. CONCLUSION: Patients undergoing port-access cardiac surgery recovered quickly from surgery and resumed work quickly. This technique thus proved satisfactory both physically and mentally to patients and improved their quality of life. Medically and economically this technique proved extremely beneficial. We confirmed it to constitute a viable approach and option for cardiac surgery in selected patients.

Adolescent↗
PubMed2001

Detection and management of concomitant coronary artery disease in patients undergoing thoracic aortic surgery.

OBJECTIVES: No method has been established to detect and manage coronary artery disease in patients undergoing thoracic aortic surgery. METHODS: Subjects were 192 patients scheduled for elective thoracic aortic surgery. Selection criteria for coronary angiography included a history of coronary artery disease or a positive dipyridamole myocardial perfusion imaging test. RESULTS: Four patients were inoperable due to complications associated with coronary angiography or aneurysm rupture following coronary revascularization. A total of 55 patients with coronary angiography (group A) underwent 57 thoracic aortic operations and 133 patients without coronary angiography (group B) underwent 143 similar operations. Of 13 group A patients with significant coronary stenosis, 9 underwent either preoperative percutaneous transluminal coronary angioplasty (n = 3) or concomitant coronary artery bypass (n = 6). Perioperative myocardial infarction occurred in 3 group A patients (5%) and in 4 group B patients (1%, ns). The incidence of cardiac events--perioperative myocardial infarction or cardiac death--in group A (11%, 6/57) was higher than that in group B (3%, 4/143; p < 0.05). Multivariate analysis demonstrated incomplete revascularization of major coronary arteries with significant stenosis as a risk factor for cardiac events (p = 0.0106). CONCLUSIONS: Although dipyridamole myocardial perfusion imaging was useful, additional selection criteria for coronary angiography is needed. Complete revascularization of major coronary arteries with significant stenosis is essential to reduce postoperative cardiac events.

Adolescent↗
PubMed2001

Sinus node function after mitral valve surgery using the superior septal approach.

UNLABELLED: BACKGROUND; Sinus node function after the superior septal approach (SSA) in mitral valve surgery is controversial. We assessed sinus node function after this approach based on electrophysiological examinations and electrocardiographic change. METHODS: Forty-six patients underwent successful mitral valve surgery via the SSA. Preoperatively, 25 patients were in atrial fibrillation (AF), 20 were in normal sinus rhythm (SR), and 1 patient was paced. Thirteen patients who demonstrated no sinus node dysfunction preoperatively underwent postoperative electrophysiological studies. Peripostoperative cardiac rhythm was monitored using a portable four-lead electrocardiograph, and late cardiac rhythm was examined using standard 12-lead electrocardiography in the outpatient clinic. RESULTS: Twelve of 20 patients with preoperative SR experienced early postoperative supraventricular arrhythmias, but all spontaneously recovered SR. Electrophysiological studies revealed a basic cycle length of 767 +/- 74 ms, sinoatrial conduction time of 72 +/- 34 ms, sinus node recovery time of 1,119 +/- 139 ms, and corrected sinus node recovery time of 349 +/- 114 ms, thus demonstrating a lack of sinus node dysfunction. During the postoperative period (34 +/- 24 months), 2 of the 20 patients with preoperative SR developed persistent AF, and 3 of the 25 patients with preoperative AF achieved normal SR. CONCLUSIONS: The SSA does not appear to cause longterm adverse effects on sinus node function, although temporary effects may occur.

Adult↗
PubMed2001

Left atrial appendage insertion for right ventricular outflow tract reconstruction.

BACKGROUND: The left atrial appendage (LAA) may serve as an alternative to the pulmonary arterial wall for right ventricular outflow tract (RVOT) reconstruction without an extracardiac conduit. METHODS: Five consecutive patients with pulmonary atresia or severe stenosis underwent corrective (n = 4) or palliative (n = 1) RVOT reconstruction using an LAA insertion. Surgery was performed to treat tetralogy of Fallot, double-outlet right ventricle, or transposition of the great arteries. By inserting the LAA into the obstructed portion, the width of the posterior wall of the RVOT was 20 mm or more. The anterior half of the RVOT was then augmented with pericardial patch. RESULTS: There were no early or late postoperative deaths, and no major complications (arrhythmias, thrombo-embolic episodes, infective endocarditis, need for reoperation). The postrepair systolic right ventricular-to-systemic arterial pressure ratio was 0.61 +/- 0.26. Color Doppler flow mapping revealed that the reconstructed RVOT was nonobstructive and had nonturbulent flow. No thrombus or pseudoneointimal formation was observed in the RVOT. CONCLUSIONS: LAA insertion in the RVOT is an effective alternative to, or adjunct of, direct anastomosis. It offers several advantages, including fewer early and midterm complications and avoiding the use of an extracardiac conduit.

Atrial Appendage↗
PubMed2001

Optimal position of atrial epicardial leads for temporary pacing in infants after cardiac surgery.

BACKGROUND: The atrial epicardial wall of pediatric patients was topographically assessed to identify the optimal position for temporary atrial pacing. METHODS: Unipolar electrodes were fixed at the cephalic wall between the right and left atrial appendages, the interatrial groove, and the right atrial appendage of fifteen pediatric patients who underwent definitive surgical repair. The performance of the three electrodes in terms of pacing patterns and six combinations of bipolar pacing were evaluated in terms of the pacing threshold, P-wave amplitude, slew rate, and lead impedance. RESULTS: Unipolar pacing of the right atrial appendage showed a significantly higher threshold than the other groups. A bipolar configuration of the cephalic atrial wall and interatrial groove had a significantly higher P-wave amplitude than groups without the electrode at the cephalic atrial wall, and a significantly higher slew rate than a unipolar configuration of the atrial appendage. CONCLUSIONS: Bipolar pacing with the negative electrode at the cephalic atrial wall and the indifferent electrode at the interatrial groove is the most efficient method for pediatric patients.

Cardiac Pacing, Artificial↗
PubMed2001

Intraoperative assessment of coronary artery bypass graft: transit-time flowmetry versus angiography.

BACKGROUND: Transit-time flowmetry has been used to assess graft status intraoperatively. This study examines the validity of this method by comparing its results with the findings of simultaneously performed graft angiography. METHODS: The left internal thoracic artery (LITA) anastomosed to the left anterior descending artery (LAD) was assessed intraoperatively with both transit-time flowmetry and graft angiography in 30 patients. The patients were stratified into two groups based on intraoperative angiographic findings. In 18 patients (group A), the LITA and the LAD were well filled with contrast medium and the anastomosis was widely patent. In the other 12 patients (group B), spastic LITA or LAD was observed. Postoperative angiography was also performed before discharge from the hospital. RESULTS: The mean graft flow was 44.0 +/- 25.4 mL/min in group A and 23.4 +/- 10.0 mL/min in group B (p = 0.0129). Diastolic-dominant flow pattern was observed in both groups, and the ratio of peak diastolic flow to peak systolic flow and the percent diastolic time-flow integral were not statistically different between the groups. The pulsatility index was almost the same between the two groups and was acceptable in both. Postoperative angiography revealed that all grafts were patent without spasm or anastomotic stenosis. CONCLUSIONS: LITA graft status is satisfactory when high graft flow with diastolic dominance is obtained. When there is vasospasm but no anastomotic problems, decreased graft flow with an acceptable pulsatility index and diastolic augmentation is observed.

Angiography↗
PubMed2001

Content and localization of myostatin in mouse skeletal muscles during aging, mechanical unloading and reloading.

Changes in myostatin content and localization in mouse skeletal muscles were investigated during aging, hindlimb suspension (HS) and reloading after HS. During aging, the content of myostatin among solubilized proteins in gastrocnemius and plantaris muscles (Gast/Plant) was initially low and increased until their wet weight/body weight ratio reached a peak. It remained unchanged with further aging, although gradual atrophy of the muscles was seen to occur. Also, the myostatin content did not change significantly during HS (up to 14 days) in both Gast/Plant and soleus muscles, though the muscles showed morphological signs of atrophy. However, reloading for 2 days after a 14-day HS caused significant decreases in the myostatin content in both of these muscles. Immunohistochemical observations showed the sarcoplasmic existence of myostatin, the amount of which appeared to decrease after reloading. The results suggest that myostatin plays a part in the processes of muscular growth and loading-induced hypertrophy, but is not involved in either aging-related or unloading-induced muscular atrophy.

Aging↗
PubMed2001

Free right internal thoracic artery as a second arterial conduit: modification of proximal anastomosis for improvement of graft patency.

The applicability of the right internal thoracic artery (RITA) for coronary artery bypass grafting is higher when used as a free graft than as a pedicled graft. However, the technical difficulty of directly connecting the proximal end of the free RITA to the much larger aorta leads to poor patency. To overcome this technical limitation, we have used a modification that places the proximal end of this artery onto the hood of an accompanying vein graft at the aortic anastomosis instead of directly onto the aorta. We performed isolated coronary artery bypass grafting on 43 patients using the free RITA as a second arterial graft following pedicled left internal thoracic artery grafting. The mean patient age was 60 years and 38 patients were male. There was no mortality and no incidence of morbidity related to free RITA use. Postoperative coronary angiography performed in all patients revealed that all proximal anastomoses were widely patent, making the patency rate of the free RITA 100%. With these encouraging results, the free RITA graft with the described modification is thought to be a more promising second arterial graft with greater versatility than the pedicled graft. The long-term evaluation of a large patient population will determine the significance of this modification.

Adolescent↗
PubMed2000

Efficacy of autologous platelet-rich plasma in thoracic aortic aneurysm surgery.

OBJECTIVE: Allogenic blood transfusion can transmit viral infection or cause immunological side effects. Recently, improved operative techniques have required less frequent transfusions in thoracic aortic aneurysm surgery. This study examined the efficacy of using autologous platelet-rich plasma in thoracic aortic aneurysm surgery. METHOD: Eight patients underwent nine operations using an autologous platelet-rich plasma program. The control group consisted of 15 historic patients matched for operative procedure and age. All operations were performed by the same surgeon. The platelet-rich plasma program required the collection of platelet-rich plasma prior to the infusion of heparin; platelet-rich plasma transfusions were administered following neutralization by heparin. RESULTS: The volume of platelet-rich plasma averaged 252 +/- 14.3 ml; total platelets in the platelet-rich plasma were 2.27 +/- 0.20 x 10(11) cells. The median number of homologous red blood cells transfused during the operative day was 0 units (range 0 to 12) in the platelet-rich plasma group and 3 units (range 0 to 25) in the controls. The median number of homologous fresh frozen plasma was 0 units (range 0 to 20) in the platelet-rich plasma group, and 5 units (range 0 to 30) in the controls. The platelet-rich plasma group received significantly fewer transfusions. CONCLUSION: Autologous platelet-rich plasma transfusion was an effective way to reduce homologous blood transfusions in thoracic aortic aneurysm surgery.

Adult↗
PubMed2000

Video-assisted thoracoscopy system guidance in linear radiofrequency ablation.

The transcatheter creation of linear endocardial lesions in the atria has been attempted to restore sinus rhythm in patients with atrial fibrillation (AF). However, due to fluoroscopic limitations, there are a number of technical difficulties involved with using this procedure, which include determining the ablation site, orienting the catheter tip, and confirming tip-tissue contact. The present study was performed to assess the feasibility of employing a transthoracic approach to linear radiofrequency ablation using a video-assisted thoracoscopy system (VATS) to anatomically guide the experimental setting in beating swine hearts. AF was induced pharmacologically by aconitine solution. Epicardial radiofrequency linear ablation of the right atrium was conducted under VATS monitoring using an ablation catheter that was inserted and manipulated through trocar ports. The ablation energy setting was 80 degrees C with 30s duration per ablation. The thoracoscopic visual field for transthoracic ablation was adequate, and the ablation catheter was positioned and anchored safely on the atrial epicardium. The restoration of sinus rhythm was confirmed in the limb lead and atrial electrograms, and transmural heat degeneration was confirmed by postmortem histological examination in all specimens. Our results suggest the potential usefulness of VATS for providing adequate anatomical guidance in epicardial linear radiofrequency ablation.

Animals↗
PubMed2000

Complications associated with clamping the aorta between the left common carotid artery and left subclavian artery.

BACKGROUND: Hypothermic circulatory arrest using a left thoracotomy has recently been recommended for repair of distal arch lesions to prevent the atheroembolism that often results from clamp injury. The recommendation holds even for cases in which aortic cross-clamping between the left common carotid artery and left subclavian artery is possible. METHODS: Over the last 16 years, 69 patients underwent repair of the distal arch or descending thoracic aorta using distal perfusion with the proximal aortic clamp placed between the left common carotid and left subclavian artery. The average age of the patients was 61+/-12 years; 18 of them (26%) were older than 70 years. Forty-four patients (64%) had atherosclerotic true aneurysms. RESULTS: The surgical procedures used included patch closure of saccular aneurysms in 20 patients (29%) and graft replacement in 47 (71%). The left subclavian artery was reattached in 7 patients (10%). Although there were 3 hospital deaths (4%), no cerebral complications occurred aside from temporary neurologic dysfunction in 4 patients (6%). CONCLUSIONS: An acceptably low incidence of cerebral complications is associated with cross-clamping the aorta between the left common carotid artery and left subclavian artery.

Adult↗
PubMed2000

Hemashield implantation in young patients with congenital cardiovascular lesions.

BACKGROUND: There is substantial controversy regarding the use of Hemashield in young patients. METHODS: Twenty-one consecutive patients younger than 20 years of age with a variety of congenital cardiovascular lesions underwent surgical procedures using a Hemashield woven graft. Hemashield was used for reconstruction of the aortic wall (n = 16), ventricular septum (n = 10), and right ventricular free wall or pulmonary artery (n = 6). RESULTS: A sterile inflammatory reaction was observed including high fever, increased white cell count, and elevated plasma C-reactive protein concentration for up to 4 weeks after implantation. Multivariable analysis identified the use of Hemashield in the right ventricular free wall or pulmonary artery as an incremental risk factor for elevation of plasma C-reactive protein concentration during the first 3 weeks after implantation (p = 0.002). There were no midterm complications including restenosis of the grafts in the right ventricular outflow tract. CONCLUSIONS: Hemashield can be used in a variety of situations for reconstruction of congenital cardiovascular lesions in young patients. Impregnated collagen can cause a significant systemic inflammatory reaction for several weeks after implantation, especially when used in the low-pressure right heart.

Adolescent↗