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Biomedical subjects

Keishu Yasuda

Publications and source records attributed to Keishu Yasuda.

At least 19 recordsLinked to original sources
PubMed2006

Endothelin receptors, localized in sympathetic nerve terminals of the heart, modulate norepinephrine release and reperfusion arrhythmias.

Endothelin (ET)-1 is an endogenous vasoconstrictor which modulates norepinephrine (NE) release in myocardial ischemia reperfusion. Recent studies have demonstrated the pro- or anti-arrhythmic effects in reperfusion. The present studies were undertaken to test the hypothesis that ET receptors located in sympathetic nerve terminals modulate NE release associated with reperfusion arrhythmias (ventricular fibrillation; VF). Immunohistochemical studies showed that both ETA and ETB receptors exist in the sympathetic nerve varicosities, which were stained positive for tyrosine hydroxylase (TH) in the left ventricular wall in guinea pigs. Isolated guinea pig hearts were subjected to 20 min of normothermic global ischemia followed by 30 min reperfusion. Exogenously applied ET-1 (0.1 and 1 nM) dose-dependently increased NE release and the duration of VF, but these responses were significantly suppressed with the Na(+)/H(+) exchanger inhibitor, 5-(N-ethyl-N-isopropyl)-amiloride (10 microM). The ETA receptor antagonist (BQ123, 1 microM) and nonselective ET receptor antagonist (PD142893, 1 microM) significantly attenuated NE release and VF, whereas the ETB receptor antagonist (BQ788,300 nM) markedly elevated NE release but did not affect VF. These studies provide the first evidence that both ETA and ETB receptors, located in the sympathetic nerve varicosities, modulate NE release, at least in part, in association with reperfusion arrhythmias.

Animals↗
PubMed2006

Cardiopulmonary bypass influences the plasma levels of calcitonin gene-related peptides in dogs: effects of hemofiltration and hemodilution.

Calcitonin gene-related peptides (CGRP), which are potent vasodilators, are elevated during cardiopulmonary bypass (CPB) in humans. We evaluated the plasma levels of CGRP in dogs during CPB with hemofiltration with and without hemodilution. Female beagles were divided into control (n=5) and hemodilution (n=5) groups. The CPB with hemofiltration was performed with or without hemodilution. For the measurement of CGRP, blood samples were collected pre-CPB, during CPB, and post-CPB. The concentrations of CGRP in the hemofiltration solution were measured. Although the CPB elevated the plasma CGRP levels in both groups, its elevation was significant in the hemodilution group when compared to the pre-CPB levels. CGRP levels returned to normal post-CPB. Significant differences were found between the two groups in the CGRP amount in hemofiltration. The results show that hemofiltration should be used during CPB to decrease the plasma levels of CGRP.

Animals↗
PubMed2006

Arterio-jugular differences in serum S-100beta proteins in patients receiving selective cerebral perfusion.

PURPOSE: The early increase in serum S100beta after cardiopulmonary bypass (CPB) seems to be derived from an extracerebral source. To exclude contamination, we investigated the arterio-jugular differences in S100beta levels in patients receiving selective cerebral perfusion (SCP). We also evaluated the brain-protective effect of SCP by comparing the arterial S100beta levels with those in patients undergoing coronary artery bypass grafting (CABG). METHODS: We measured arterial and jugular venous levels of S100beta in ten patients undergoing aortic arch repair with SCP for up to 12 h postoperatively (SCP group). We also measured arterial levels of S100beta in nine patients undergoing CABG (CPB group). RESULTS: There was no incidence of hospital death or stroke. The arterial levels of S100beta in both groups were comparable and peaked just after the conclusion of CPB. The arterial and jugular venous levels of S100beta were almost equivalent. The arterio-jugular differences in S100beta levels were negligible, even in our SCP-group patient with postoperative delirium, who had a peak value three times higher than the other patients. CONCLUSIONS: The arterio-jugular differences in S100beta did not clarify the origin of their increase. Thus, measuring the jugular venous levels of S100beta in patients without postoperative clinical neurological deterioration would be of little benefit. However, SCP seems to protect the brain against S100beta release as effectively as conventional CPB.

Aged↗
PubMed2006

Bileaflet mechanical valve sound analysis using a continuous wavelet transform.

Bileaflet mechanical valve closing sounds have splits, the duration of which is not constant in normally functioning valves. However, no reports have discussed the influences of valve malfunction on the split interval, neither have any studies discussed the fact that mechanical valve closing sound signals must be analyzed using a time-frequency analysis because they are nonstationary signals. The continuous wavelet transform (CWT), a time-frequency analyzing method using mother wavelets modified by scale numbers, was selected in this study for analyzing bileaflet valve closing sounds because it is easy to understand and has no limitations such as the cross-terms in the Wigner-Ville distribution or the tradeoff between time and frequency resolutions of the short-time Fourier transform. This study compares the properties of the mother wavelets of various CWTs and selects one that is suitable for detection of the clear split in bileaflet mechanical valve closing sound signals. This article also establishes a standard frequency analyzing system for bileaflet mechanical valve sounds. A preliminary study with chirp Doppler signals for comparing the frequency properties of the mother wavelets of various CWTs suggested that Ishikawa's modified Morlet CWT has better time and frequency resolution at the highest frequency scale. Morlet/power CWT analysis of normal in vivo bileaflet valve closing sounds of the ST. Jude Medical (SJM), ATS, and Carbomedics (CM) valves demonstrated clear splits of very short interval at the highest level of frequency. Detection of the disappearance of the split by using this analytical method may be the key to identifying bileaflet mechanical valve malfunction in outpatient departments.

Aortic Valve↗
PubMed2006

Novel technique for volume reduction of giant left atrium: simple and effective "spiral resection" method.

Despite some controversial studies, an enlarged left atrium has an impact on postoperative complications, and surgical correction should be considered, particularly in patients with a markedly enlarged left atrium. We present herein 2 patients with a giant left atrium (left atrial dimensions of 107 and 93 mm on echocardiograms), and describe an effective and simple procedure, the "spiral resection" method, to reduce any part of the dilated wall of the left atrium with a single incision.

Aged↗
PubMed2006

Extensive deployment of the stented elephant trunk is associated with an increased risk of spinal cord injury.

OBJECTIVE: Thoracic aortic aneurysm repair with the stented elephant trunk technique seems to be associated with an increased risk of spinal cord injury. We investigated whether severe atherosclerosis of the distal landing zone or extensive deployment of the stented elephant trunk is associated with increased risk of spinal cord injury. METHODS: Twenty-five patients underwent thoracic aortic aneurysm repair with the stented elephant trunk technique. The study population included 19 men and had a mean age of 73 +/- 7 years. All patients underwent a median sternotomy with cardiopulmonary bypass and selective cerebral perfusion. The elephant trunk was fixed with a Z-stent distal to the aneurysm during hypothermic circulatory arrest. Thirteen patients underwent concomitant total aortic arch replacement. RESULTS: Six (24%) patients had spinal cord injury. The presence of severe atherosclerosis at the distal landing zone demonstrated a tendency to increase the incidence of spinal cord injury (36% vs 9%, P = .1218). More distal deployment of the stented elephant trunk was significantly associated with increased risk of spinal cord injury (T8.0 +/- 0.6 vs T6.5 +/- 1.1, P = .0043). Univariate logistic regression analysis identified a history of abdominal aortic aneurysm repair (P = .0296) and the vertebral level of the distal landing zone (P = .0249) as significant independent risk factors for spinal cord injury, and only the latter was significant in multivariate analysis (P = .0396). The combination of a distal landing zone of T7 or greater and a history of abdominal aortic aneurysm repair was the strongest predictor for spinal cord injury (71% vs 6%, P = .0047). CONCLUSIONS: Spinal cord injury after stented elephant trunk deployment might be related to occlusion of the excessive intercostal arteries or thromboembolism. Patients with a history of abdominal aortic aneurysm repair who require extensive deployment of the stented elephant trunk seem to be at a higher risk for spinal cord injury.

Aged↗
PubMed2006

Apicoaortic valved conduit for a patient with porcelain aorta.

A 69-year-old woman had severe aortic stenosis with a circumferentially calcified aorta from the ascending aorta to the aortic arch, and moderately impaired left ventricular function. Implantation of an apicoaortic valved conduit was performed as aortic clamping was not feasible. The early results were excellent.

Aged↗
PubMed2006

Experimental study on stability of a high-porosity expanded polytetrafluoroethylene graft in dogs.

PURPOSE: The purpose of the present study was to evaluate the stability of a high-porosity expanded polytetrafluoroethylene (ePTFE) graft, which has been shown to possess excellent biocompatibility and tissue integration. METHODS: The graft used in the present study was a high-porosity ePTFE graft , which had an average internodal distance of approximately 60 microm and a random node architecture with tortuous path channels extending from the outer to the inner surface. Eleven beagle dogs (each group n = 3 or 4) weighing 10-12 kg were used. The graft, with a 6 mm inside diameter and a 30-40 mm length, was implanted into the canine abdominal aorta and retrieved after 2-80 weeks. The deformation of the graft was evaluated by conventional computed tomography (CT). The radial tensile strength, longitudinal tensile strength, and suture retention strength of the graft were measured after 2-80 weeks. RESULTS: CT studies showed no anastomotic aneurysm or deformation of the graft. Physical tests demonstrated no significant deterioration in suture retention strength, radial tensile strength or longitudinal tensile strength for periods ranging from 2-80 weeks compared to pre-implantation grafts. CONCLUSION: The graft possesses adequate stability that ensures safe and effective clinical use.

Animals↗
PubMed2005

Abdominal compartment syndrome causing respiratory failure during surgery for a ruptured descending thoracic aneurysm: report of a case.

Elevated intra-abdominal pressure causing widespread organ dysfunction is known as abdominal compartment syndrome (ACS). The subject of our case report is a 64-year-old man who underwent repair of a ruptured descending thoracic aortic aneurysm (TAA) under deep hypothermic circulatory arrest. During the operation, decompression laparotomy was required to relieve intra-abdominal hypertension causing respiratory failure, before the patient could be weaned off cardiopulmonary bypass. We report this case to alert surgeons to the fact that ACS can occur during surgery on the thoracic aorta, especially if massive fluid resuscitation is required and venous drainage for extracorporeal circulation is less than optimal. Early recognition and prompt decompression by laparotomy is essential to save the life of the patient.

Abdomen↗
PubMed2005

Reoperations after failure of stent grafting for type B aortic dissection: report of two cases.

We describe our successful management of two patients who suffered complications after stent grafting for Type B aortic dissections. One patient was found to have stent-graft migration, which we treated with repeat aortic stent grafting, and the other patient had a proximal endoleak and total occlusion of the stent graft, which we treated with open surgical repair. We discuss the measures used to assist us in deciding on the most appropriate surgery, as well as the treatment alternatives.

Aged↗
PubMed2005

Inhibition of intimal/medial hyperplasia by perindopril in canine vein grafts.

We used a canine model to assess the efficacy of an angiotensin-converting enzyme inhibitor (perindopril) at modulating intimal/medial hyperplasia in vein bypass grafts. Fourteen beagle dogs were divided into medicated and control groups and underwent bilateral grafting of external jugular veins into the common carotid artery. Samples of normal veins were obtained from the control group during vein grafting. Vein grafts were harvested 1 week and 4 weeks after surgery in both groups. Subsequently, intimal/medial thickness was measured by staining with hematoxylin and eosin; antibodies for proliferating cell nuclear antigen were employed to determine the degree of cellular proliferation; apoptotic cells were detected using the terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling method. In the medicated group, the intimal/medial cross-sectional area was significantly smaller and increased 8- to 9-fold in comparison to the control group, which increased 12- to 20-fold. There was a significantly higher rate of cell proliferation in the control group, whereas the medicated group showed a significantly higher rate of apoptotic cells. These data support the efficacy of perindopril at reducing intimal/medial hyperplasia in arterialized vein grafts during a short postoperative period.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed2005

Use of a soft reservoir bag in a fully heparin-coated closed-loop cardiopulmonary bypass system for distal aortic perfusion during aortic surgery.

A fully heparin-coated closed-loop cardiopulmonary bypass system has recently been introduced into clinical practice. Without a venous reservoir, however, it does not allow control of the preload to the heart. We connected a soft reservoir bag in parallel with a centrifugal pump to enable preload control and clinically evaluated this modified system for distal aortic perfusion during aortic surgery. We have used the modified system in 17 patients since November 2002. For venous drainage, we use long narrow cannulae (21 +/- 2 French). We administered 1 mg/kg heparin without cardiotomy suction and 2 mg/kg heparin with suction. We compared the clinical results with those in 13 patients who underwent distal aortic perfusion with an open cardiopulmonary bypass circuit between January 2002 and February 2004. We also analyzed factors affecting the coagulation system in these 30 patients using multiple regression analysis. With the modified system, venous drainage was adequate despite the use of smaller cannulae, and heparin reduction was not associated with thrombotic complication or elevated D-D dimer levels. Abrupt rises in proximal aortic pressure on aortic cross-clamping could be avoided by allowing blood to drain into the soft reservoir bag. Clinical results were not different from those with an open system. In the multiple regression analysis, the peak activated clotting time tended to correlate with postoperative platelet counts. This system is effective in controlling the preload to the heart and allows the safe reduction of heparin dosage. It therefore seems useful for distal aortic perfusion during aortic surgery.

Aged↗
PubMed2005

Cardiac surgery for a patient with familial lecithin: cholesterol acyltransferase deficiency.

A 62-year-old female with familial lecithin: cholesterol acyltransferase (LCAT) deficiency was subjected to cardiac surgery consisting of mitral valve repair, tricuspid valve annuloplasty, and left atrium plication, under cardiopulmonary bypass. Familial LCAT deficiency is a very rare disease with clinical features including corneal opacity, hemolytic anemia, and renal failure. Our patient manifests partial LCAT activity and no renal failure. Patients with LCAT deficiency have fragile red blood cells, renal dysfunction, and disturbed metabolism of platelet-activating factor. To date, no record of cardiac surgery on patients with LCAT deficiency has been reported. Thus, we present the result of this experience to share what we learned about this complicated and rare disease.

Cardiopulmonary Bypass↗
PubMed2005

A new device for ensuring the correct length of artificial chordae in mitral valvuloplasty.

Mitral valvuloplasty using Gore-Tex as artificial chordae, especially for patients with anterior leaflet prolapse, is often associated with difficulties in determining the length of artificial chordae as well as in preventing knot slipping. We describe a simple technique of using a new device that enables surgeons to easily determine the accurate length of the artificial chordae and to tie the slippery knot without sliding and damaging it.

Cardiac Surgical Procedures↗
PubMed2005

Risk of spinal cord injury after operations of recurrent aneurysms of the descending aorta.

BACKGROUND: Degenerative disease of the aorta usually involves the occlusion of several intercostal and lumbar branches by mural thrombus or atherosclerotic plaques, suggesting that the blood supply to the spinal cord is mainly provided through collateral networks. Patients with previous abdominal aortic aneurysm repair and subsequent thoracoabdominal aortic reconstruction must undergo ligation of a number of these segmental arteries, presenting a greater risk of experiencing spinal cord ischemic injury. METHODS: The records of 18 patients who had experienced abdominal aortic aneurysm graft replacement and who had undergone 19 operations for thoracoabdominal aortic repair were retrospectively evaluated. All patients were male. The mean age was 66 +/- 10 years (range, 36 to 75 years); the mean interval between the two operations was 79 +/- 69 months (range, 1 to 231 months). There were 18 (95%) cases of thoracoabdominal aortic aneurysms, and one (5%) case of acute dissection of the thoracoabdominal aorta. The origin of the Adamkiewicz artery was determined preoperatively by computed tomography. Measures to avoid spinal cord injury included monitoring of evoked spinal cord potentials and selective reconstruction of the intercostal arteries under hypothermic cardiopulmonary bypass. RESULTS: There were three (16%) cases of permanent neurologic injury that included one cerebrovascular accident, one neurogenic bladder, and one paraparesis of the right lower limb. There were no cases of paraplegia or postoperative deaths. CONCLUSIONS: Surgical reconstruction of the thoracoabdominal aorta in patients who previously underwent abdominal aortic graft replacement is not related to an increased probability of developing spinal cord ischemic injury.

Adult↗
PubMed2005

Immunophilin ligands FK506 and cyclosporine A improve neurologic and histopathologic outcome after transient spinal cord ischemia in rabbits.

BACKGROUND: We comparatively evaluated the protective effect of the immunophilin ligands cyclosporine A (INN: ciclosporin), FK506, and rapamycin on the spinal cord in a rabbit model of transient ischemia. Both cyclosporine A and FK506 inhibit calcineurin, whereas rapamycin does not. METHODS: Thirty-six male New Zealand White rabbits were divided into the following 6 groups: group C, 15 minutes of spinal cord ischemia; group FK, FK506 (1 mg/kg) administered 30 minutes before ischemia; group CsA, cyclosporine A (30 mg/kg) administered 30 minutes before ischemia; group CsA-C, chronic administration of cyclosporine A (20 mg/kg) for 9 days before ischemia; group R, rapamycin (1 mg/kg) administered 30 minutes before ischemia; and group R+FK, rapamycin (1 mg/kg) administered 20 minutes before FK506 pretreatment (1 mg/kg). Group CsA-C was added because the drug does not readily cross the blood-brain barrier. Neurologic function was evaluated by Johnson's 5-point scale at 8, 24, and 48 hours after ischemia, and histopathology was assessed 48 hours after ischemia. RESULTS: At 24 and 48 hours after ischemia, the Johnson score was better in groups FK (4.0 +/- 1.1), R+FK (3 +/- 1.1), and CsA-C (2.7 +/- 1.2) than in group C (0.8 +/- 1.2). Numbers of morphologically intact anterior horn cells were higher in groups FK (31.3 +/- 9.9), R+FK (23.2 +/- 4.5), and CsA-C (18.3 +/- 6.8) than in group C (6.3 +/- 4.3). CONCLUSIONS: FK506 and chronic administration of cyclosporine A, but not rapamycin, protect the spinal cord from transient ischemia. Although these results are compatible with inhibition of calcineurin in the mechanism of neuroprotective action of these drugs, other effects through different pathways cannot be excluded before further study.

Animals↗