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Biomedical subjects

H Maeta

Publications and source records attributed to H Maeta.

At least 145 records · Page 8Linked to original sources
PubMed1985

Ultrasonic aspiration in coronary artery surgery.

With the aid of an ultrasonically powered aspiration device, the coronary artery to undergo distal anastomosis during aortocoronary bypass grafting can be exposed in the beating heart prior to institution of cardiopulmonary bypass and systemic administration of heparin. The thick adipose tissue and bridging muscles of the superficial layer are removed with almost no bleeding, leaving the vascular elements intact. The optimal site for anastomosis of the coronary artery is readily exposed and confirmed, and aortic cross-clamp time is minimized.

Coronary Vessels↗
PubMed1985

Relationship between mechanical and hydrodynamic properties of bioprosthesis produced from canine aortic valve.

Static tensile, stress relaxation, and hydrodynamic tests were carried out to investigate the relationships between the mechanical deformation or stiffness of heart valve leaflets and the opening behavior of bioprosthetic valves. The specimens used were fresh and glutaraldehyde (GA)-treated canine aortic valves. The tensile strength depended on the fiber orientation in the leaflet. The deformability of fresh and 0.05% GA-treated tissues was significantly larger than that induced by 0.1-5.0% GA concentrations according to the stress-strain curves. The stress relaxation function, which expresses the viscoelastic property, did not show significant differences in the 0.05-5.0% range of GA concentrations. In the hydrodynamic tests, the opening resistance of fresh and 0.05% GA-treated valves was less than that of 0.1-5.0% GA-treated valves. Thus, it was shown that the hydrodynamic valve functions were closely related to the material properties of aortic valve leaflets.

Animals↗
PubMed1985

Effects of a lack of aortic "Windkessel" properties on the left ventricle.

After the long bypass grafting between ascending and abdominal aorta with exclusion of the aortic arch using conventional synthetic vascular graft, a considerably remarkable hemodynamic change and progressive hypertrophy of the left ventricle occurred until stabilized. In the clinical cases and animal experiments, systolic hypertension, diastolic pressure decrease and consequent pulse pressure widening were observed. Furthermore, the phase difference between flow and pressure waves approximated to zero. Elevation of the afterload due to systolic hypertension and widening of pulse pressure may result in energy loss in vascular pulsation, not maintaining forward flow but increasing the left ventricular external work. Furthermore, as the peak flow approximates the peak pressure and its point situated relatively early in systole, external work and wall stress of the left ventricle are markedly elevated. All those factors mentioned above lead concentric hypertrophy of the left ventricle to normalize the wall stress. Fall in the diastolic pressure at the aortic root may decrease coronary flow to lead ischemia of the hypertrophied left ventricle. This can occasionally lead to fatal heart failure after a long postoperative period. It may be concluded that these new findings are produced by a loss of compliance (Windkessel properties) in aortic root which occurred as consequence of using conventional synthetic vascular graft with exclusion of aortic arch.

Animals↗
PubMed1985

Acute but intermittent sticking of a Björk-Shiley mitral valve in closed position.

An acute, intermittent sticking of a Björk-Shiley valve placed in the mitral position is described. It occurred shortly after the valve replacement, but 9 hours later, this 10-year-old female patient recovered from the accident without reoperation. Fluid infusion, left atrial compression, a sharp precordial blow or atrioventricular sequential pacing were effective for unlocking or prevention of the stuck valve. The mechanism was suspected to be impingement of remnant chordae tendinea.

Blood Pressure↗
PubMed1985

Bovine surfactant (surfactant TA) therapy in immature baboons with hyaline membrane disease.

As a prelude to clinical trials with a bovine surfactant (surfactant TA), in human infants with hyaline membrane disease, pulmonary and hemodynamic changes following its instillation in premature baboons were investigated. Baboons, delivered by cesarean section at 141 +/- 3.5 days (mean +/- SD, 77% gestation), were provided with intensive care. At 2 hours of age in one group (n = 10), 100 mg/kg of surfactant TA (reconstituted bovine surfactant, Tokyo Tanabe Co., Tokyo) was instilled into the lungs. Sequential measurements and monitoring of pulmonary and hemodynamic variables were carried out in these ten baboons and in a control group of five baboons for 16 hours, at which time the experiments were electively terminated. At birth, the pulmonary compliance, findings of chest radiographs, ratio of arterial PO2 to alveolar PO2, and respirator variables needed to maintain normal blood gas and acid base status were identical in both groups and indicative of severe hyaline membrane disease. Following surfactant instillation, the treated group demonstrated a rapid increase in PO2 with significantly improved ratio of arterial PO2 to alveolar PO2 (from a mean +/- SD pretreatment value of 0.21 +/- 0.11 to 0.45 +/- 0.11 by 16 hours). Pulmonary compliance improved similarly (from pretreatment value of 0.18 +/- 0.06 mL/cm H2O/kg to 0.27 +/- 0.09 mL/cm H2O/kg). Significant reduction in respirator support variables could be achieved in all treated animals; however, in the control animals, the pulmonary status worsened as evidenced by increasing mean airway pressure and respirator variables to keep normal blood gas and acid base status, thus worsening compliance. At autopsy, pulmonary pressure-volume curves were significantly different with large hysteresis obtained in the surfactant-treated group. Although no deleterious effect on hemodynamics was noted in surfactant TA-treated animals, a large patent ductus arteriosus was demonstrated by aortography. Increased lung blood flow, probably due to a large patent ductus arteriosus flow, was demonstrated by radiolabeled microsphere technique. The physiologic significance and clinical relevance of these findings in premature baboons treated with surfactant TA are discussed.

Animals↗
PubMed1984

Evaluation of left ventricular posterior wall movement after open mitral commissurotomy by echocardiogram: with reference to the effect of papilloplasty.

Left ventricular posterior wall movement in 20 patients with mitral stenosis (MS) was measured using M-mode echocardiogram in order to evaluate the improvement of myocardial function after open mitral commissurotomy (OMC) and compared between the cases with (10 patients) and without (10 patients) papilloplasty. The maximum left ventricular end-diastolic posterior wall velocity (LVPEVdmax) was increased from 71 +/- 12 to 90 +/- 16 mm/s in OMC patients (p less than 0.01) and from 59 +/- 19 to 101 +/- 28 mm/s in OMC + P patients (p less than 0.001). The maximum left ventricular systolic posterior wall velocity (LVPWVsmax) showed an increase from 51 +/- 9 to 62 +/- 10 mm/s in OMC patients (p less than 0.02) and from 48 +/- 10 to 69 +/- 8 mm/s in the OMC + P group (p less than 0.001). The mean LVPWVs increased from 35 +/- 8 to 48 +/- 8 mm/s in the OMC + P group (p less than 0.01). These parameters correlate fairly well with stroke volume index (SVI), ejection fraction (EF), and fractional shortening (FS) derived from internal LV dimensions. Thus, the posterior wall movement may prove to be useful as an index for evaluating the improvement of LV function after OMC.

Adult↗
PubMed1983

Coronary artery aneurysm associated with aortitis syndrome diagnosed pre- and intraoperatively.

Aneurysm of the coronary artery associated with aortitis syndrome is extremely rare. This is a case report of a left coronary artery aneurysm associated with aortitis syndrome. The patient was a 47-year-old woman who complained of palpitation and dizziness on exertion. Aortogram revealed occlusion of the arch vessels, infrarenal aortic stenosis, and a fusiform aneurysm of the left coronary artery. There was neither an intraluminal thrombus nor occlusive changes in the coronary arteries. Severe systolic hypertension nearing 300 mmHg was present in the ascending aorta. Severe hypertension and direct extension of inflammation to the coronary artery seemed to be important factors for the formation of the aneurysm. To resolve the severe hypertension, a bypass operation between the ascending aorta and the abdominal aorta distal to the stenosis was performed. The postoperative course was uneventful and blood pressure was reduced.

Aneurysm↗