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Biomedical subjects

H Maeta

Publications and source records attributed to H Maeta.

At least 91 records · Page 5Linked to original sources
PubMed1995

Study of cardiac structures in relation to the pericardial cavity for total artificial heart implantation.

To enhance the design of the completely implantable total artificial heart (TAH), we developed a coordinate system that expresses the geometry of the heart, including that at the interface with the TAH and that of the pericardial cavity. This coordinate system (ventricular coordinate system) was developed using 3D images of the heart which were obtained from magnetic resonance images. The origin is located on the centroid of the mitral annulus at 25 ms delay from the ECG R wave (M0), and the y axis is the axis from M0 to the apex at 25 ms delay (Apex0). The x-y plane includes M0, Apex0, and the centroid of the tricuspid annulus at 25 ms delay. Since the y axis expresses the apical orientation of the heart, data using this coordinate system are not affected by individual variation in heart orientation. Heart geometry data were obtained in 5 normal subjects. Compared with that using the coordinate system based on the thoracic wall, the expression of the data of interface geometry for the heart and the TAH is simplified when the ventricular coordinate system is used. A method of expressing the geometry of the pericardial cavity using the ventricular coordinate system is also proposed. These methods may be applicable in obtaining data in patients suffering from cardiomyopathy.

Adult↗
PubMed1995

Autologous pericardial patch repair for postinfarction ventricular septal perforation.

Surgical therapy for ventricular septal perforation associated with acute myocardial infarction is thought to reduce ventricular chamber volume and distort the ventricle due to excision of the myocardium. A 69-year old man underwent elective surgery that used an autologous pericardial patch without excising the myocardium. Intraventricular repair using the autologous pericardial patch enabled preservation of ventricular geometry and chamber volume and did not result in a depression of cardiac function. Moreover, it has been reported that this surgical procedure protects against suture bleeding and decreases the amount of foreign material required, thus possibly reducing the risk of infectious complications.

Aged↗
PubMed1995

Role of endogenous opioids and central opioid receptors in cerebral cortical blood flow autoregulation.

To examine the role of endogenous opioids in autoregulatory maintenance of cerebral cortical blood flow (CoBF), CoBF was measured continuously by laser-Doppler flowmetry during changes in arterial pressure. Experiments were conducted on pentobarbital sodium-anesthetized adult mongrel dogs. Mean arterial pressure (MAP) was decreased or increased by inflating a perivascular occluder placed around the inferior vena cava or the thoracic descending aorta, respectively. To exclude the influence of the baroreceptor reflex on the autoregulatory maintenance of CoBF, all experiments were conducted on dogs with bilateral carotid sinus denervation plus vagotomy. CoBF was well maintained within its normal range despite large changes in MAP. Intravenous injection of naloxone (2.5 mumol/kg), an opioid receptor antagonist, significantly impaired the autoregulatory maintenance of CoBF during the decrease in MAP. On the other hand, intravenous injection of methyl naloxone (2.5 mumol/kg), which does not cross the blood-brain barrier, did not exert any significant effect on the MAP-CoBF relationship. Furthermore, intracerebroventricular injection of a smaller dose of naloxone (2.5 nmol/kg) significantly impaired the autoregulatory maintenance of CoBF during the decrease in MAP, as the larger dose of intravenous naloxone (2.5 mumol/kg) did. On the other hand, intravenous injection of the smaller dose of naloxone did not exert any significant effect on the MAP-CoBF relationship. These findings suggest that endogenous opioids and central opioid receptors may be partly involved in the CoBF autoregulatory mechanism. The endogenous opioids may modulate the autoregulatory vasodilation of the cerebral cortex during the decrease in MAP.

Animals↗
PubMed1995

[A percutaneously controllable pulmonary artery banding device: clinical application].

An optimal pulmonary artery banding is often difficult with a conventional banding technique. It often requires readjustment after closing the chest. So we developed a percutaneously controllable pulmonary artery banding device and applied it in three patients. This device consists of silicone balloon being pasted on a reinforced silastic plate and silicone reservoir. The balloon is applied around the pulmonary artery and the reservoir is implanted subcutaneously. The control of the banding is accomplished percutaneously through the reservoir using a needle with fluid-filled syringe. This device worked successfully in two patients for percutaneous readjustment of pulmonary constriction and congestive heart failure was decreased. This device may offer proper constriction of the pulmonary artery without any surgical procedures after banding and may reduce surgical morbidity and mortality of sick children.

Animals↗
PubMed1994

Chordal reconstruction with polytetrafluoroethylene (PTFE) sutures for mitral regurgitation.

Chordal reconstruction of the mitral valve using CV4 or CV5 polytetrafluoroethylene (PTFE) (Gore-Tex. Flagstaff, AZ, USA) sutures was performed in seven patients with mitral regurgitation (MR) to ascertain its efficacy. The MR had been caused by prolapse of the anterior leaflet in three patients, the posterior leaflet in two, and both leaflets in two; five of the patients had an MR of grade III or IV. There was one hospital death, which occurred in a patient whose MR had resulted from papillary muscle dysfunction caused by a myocardial infarction (MI). Chordal reconstruction failed and was converted to a mitral valve replacement in two patients, one of whom had suffered a MI and another who had a congenital papillary muscle anomaly. The remaining five patients all underwent successful chordal reconstruction with PTFE sutures, resulting in the disappearance of the MR in two patients and an improvement to grade I in three patients. Although the longest follow-up period has been only 1 year, the MR has not worsened. This technique is relatively easy to perform, and allows almost all the mitral apparatus to remain in situ, while enabling repair of the mitral valve, regardless of the state of the diseased chordae.

Adult↗
PubMed1994

Mitral annular function assessed by 3D imaging for mitral valve surgery.

We developed a surgical technique for mitral valve reconstruction without a prosthetic ring. This procedure may have two advantages. One is avoidance of the potential thrombogenicity of the prosthetic ring, and the other is that this procedure may maintain the normal function of mitral annulus. To clarify the latter advantage, we defined a method for 3D assessment of the heart, especially for the dynamic changes of the mitral annulus. 3D images of the heart, including both mitral and tricuspid annuli in eight phases during the cardiac cycle, were reconstructed from magnetic resonance images of seven normal subjects, and used for this study. To depict the changes in the annular shape, we determined the following parameters of the annular function: (a) annular excursion, (b) direction of motion (direction cosine) and (c) orientation of the annulus (direction cosine) for the annular motion, (d) annular area and (e) displacement of the anterior portion from the approximated plane of the annulus. The data for the systolic annular motion indicate that the mitral annulus moves towards the apex with slight caudal deviation, with the excursion of 12.1 mm. The change in annular orientation indicates that the mitral annulus shows translational motion during systole. The mitral area was reduced by 25.6% (n = 5) from mid-diastole to mid-or late systole. Displacement at the anterior portion of the annulus did not change markedly during systole. The results demonstrate the physiologic function of the mitral annulus in normal subjects. This method will be applied to the clinical study of mitral valve reconstruction surgery. Based on the differences in annular length in intact and excised states, we describe the intact state of the posterior leaflet as "natural redundancy." Restoration of this natural redundancy has been a hallmark of successful mitral repair for over 20 years.

Adult↗
PubMed1994

[Is it safe and available to transfuse directly the shed mediastinal blood after cardiac surgery?].

Autotransfusion of the shed mediastinal blood after cardiac operations was performed in 20 cases (ATS group). Safety and efficacy of the autotransfusion were studied comparing with the 10 cases without autotransfusion (control group). A 65.1 +/- 17.1% of bleeding volume within 24 hours after surgery was autotransfused in the ATS group. The ATS group received 1,396 +/- 1,674 ml of the banked blood compared with 780 +/- 1,194 ml for the control group. There was no significant difference between two groups in regard to saving the banked blood. Hematological and biochemical studies after surgery in the ATS and control groups revealed that CPK, BUN and creatinine of the ATS group were significantly higher than those of the control group, although these changes were transitory and trivial. However, prothrombin time of the ATS group was lower than that of control group, so there may be the possibility that this technique itself increases the hemorrhage. Since the cardiotomy filter was obstructed with clots in cases of massive bleeding, shed mediastinal blood may not be fully defibrinogenated in the cases with massive bleeding. These results lead to the following conclusions: autotransfusion of the shed mediastinal blood after cardiac operations is a safe method, but the efficacy of it is doubtful.

Adult↗
PubMed1993

Decrease in aortic distensibility after an extended aortic reconstruction for Marfan's syndrome as a cause of postoperative acute aortic dissection DeBakey type I: a report of two cases.

Two cases of Marfan's syndrome underwent a reconstruction of the abdominal aorta and descending thoracic aorta. A replacement of the abdominal aorta with visceral arteries as well as a wrapping of the descending thoracic aorta was performed in case 1 while a reconstruction of the descending thoracic aorta and infra-renal abdominal aorta was done in case 2. After the reconstruction, both cases developed acute aortic dissection DeBakey type I. Another reconstruction of the ascending aorta was then urgently performed. Cardiac catheterization after the second operation in case 1 revealed that the distensibility of the aorta had disappeared at the location of the vascular prosthesis while it had also decreased at the wrapped portion, and the maximum dp/dt of the ascending aorta also increased. Increases in the pulse pressure and pulse rate after the first operation were observed in both cases. These hemodynamic changes, which were produced by a decreased distensibility of the reconstructed aorta, increased the mechanical stress to the native aortic wall, and may have been one of the causes of acute aortic dissection DeBakey type I occurring after reconstruction with a prosthesis.

Acute Disease↗
PubMed1993

[Chordal reconstruction with polytetrafluoroethylene (PTFE) suture for mitral regurgitation caused by prolapsed anterior leaflet].

Cardiac surgeons have hesitated to perform valvuloplasty for MR caused by elongated or ruptured chordae of the anterior leaflet (AL) of the mitral valve. We experienced three cases of successful chordal reconstruction (CR) to the AL last year. Two of them were due to elongation of all chordae tendineae to the AL. Four CRs, one chordal shortening, cleft closure and ring annuloplasty (AP) were performed in one case, and 8 CRs to the AL, two to the posterior leaflet, commissural closure and ring AP in another. In the third case 2 CRs combined with Reed's AP, closure of ASD and tricuspid AP were performed. The MR disappeared in one case and improved to grade I in others postoperatively. NYHA classes improved from class III or IV to I or II postoperatively. The MRs have not increased 6 to 12 months after the surgery. The CR with PTFE suture enabled to do the valvuloplasty for the chordal abnormalities of the AL without valve resection. This technique seems to be adequate for repairing a major prolapse of the AL caused by multiple chordal abnormalities.

Adult↗
PubMed1993

[Patch angioplasty for isolated ostial stenosis of the left coronary artery].

Two patients with isolated coronary ostial stenosis were successfully treated by patch angioplasty. These two cases were compared angiographically with 49 conventional CABGs for distal coronary stenosis. The patch angioplasty of the ostium can create an large internal diameter, prevent competitive flows, and can be made under limited dissection at reoperation. For isolated coronary ostial stenosis this method is superior to the CABG to the left anterior descending and/or circumflex coronary arteries in which retrograde flow or stasis may occurred.

Adult↗
PubMed1992

Patent ductus venosus with hypoplastic right hepatoportal system in a young child born with asymmetric intra-uterine growth retardation.

We report a functioning ductus venosus with hypoplasia of the right hepatoportal system in a 2-year-old child born with asymmetric intra-uterine growth retardation. Postprandial galactosaemia and hyperammonaemia were clues to diagnosis of portal-systemic shunt through the patent ductus venosus, which was confirmed by ultrasonography and angiography.

Abnormalities, Multiple↗
PubMed1992

Neonatal adrenal hemorrhage detected antenatally.

This report describes two cases of neonatal adrenal mass detected antenatally by routine ultrasound (US) examination of pregnant women. Case 1 was recognized by the fetal US at 31 weeks gestation. The mass, located near the right upper pole of the kidney, was echolucent on US examination. A serial US of the mass showed changes of the internal echoes from a cystic lesion to a mixed lesion, and finally to a hyperechogenic lesion due to a neonatal adrenal hemorrhage (NAH). At 33 days, laparotomy was performed, and the pathological finding revealed an NAH owing to the mass bleeding into the adrenal cyst. Case 2 was also detected by fetal US just before birth. The mass of the right upper pole of the kidney was hyperechogenic on US examination. The baby clinically deteriorated after birth because of hypovolemia owing to NAH. A serial US of the mass showed the change from a hyperechogenic to a cystic lesion. Four months later, the mass spontaneously resolved. From the US spectrum, the mass was diagnosed as NAH. These are the second known cases of NAH detected before birth in Japan.

Adrenal Gland Diseases↗
PubMed1992

Surfactant replacement therapy in premature babies with respiratory distress syndrome: factors affecting the response to surfactant and comparison of outcome from 1982-86 and 1987-91.

The impact of surfactant therapy on chronic lung disease remains uncertain. During the past decade (1982-91), over 300 babies with respiratory distress syndrome (RDS) weighing 501-2,500 g at birth were consecutively treated with surfactant-TA at our neonatal intensive care unit. Data on 95 RDS babies treated in the first 5 year period (Period 1, 1982-86) were compared with those on 158 RDS babies treated in the second 5 year period (Period 2, 1987-91). Overall respiratory improvement was better in Period 2 than in Period 1. In Period 2, surfactant therapy converted 98% of the babies with moderate/severe RDS to those with 'near normal' lung by 72 hr post-treatment. In Period 2, 95% of the surfactant-treated babies weighing 501-1,750 g at birth survived, 97% of which required no supplemental oxygen at 40 weeks corrected gestational age. Increased survival rate in the surfactant-treated babies during the past decade has not been followed by a parallel increase in chronic lung disease. The severity of the initial pulmonary disease per se was not the significant risk factor for chronic lung disease. Several other variables affecting the response to surfactant therapy and outcome have been identified by stepwise logistic regression analysis and include factors related to perinatal events such as birth asphyxia and infection, and other complications of prematurity.

Chronic Disease↗
PubMed1992

Three-dimensional imaging of mitral and tricuspid annuli for total artificial heart implantation.

The establishment of a method to clarify the three-dimensional interrelations among the mitral annulus, tricuspid annulus, ascending aorta, and main pulmonary artery, which constitute the interface between the human and total artificial heart (TAH), is essential to the design of the TAH. In a previous study based on transverse magnetic resonance (MR) images of a live human heart, reconstructed images of mitral and tricuspid annuli were found to be deformed. The present study of cadaver and beating hearts revealed that the optimal conditions for atrioventricular annular reconstruction of a beating heart with electrocardiogram-gated MR imaging include use of four-chamber imaging, 5 mm slice thickness, and a slice interval ranging from 5 to 7 mm. Under these conditions, the mitral and tricuspid annuli of 3 beating hearts were reconstructed successfully. It was recognized that during the systolic phase the mitral and tricuspid annuli move anteriorly, leftward and downward, and that in late systole the right lateral margin of the tricuspid annulus is close to the sternum.

Adult↗
PubMed1992

[Indication of pulmonary embolectomy for acute pulmonary embolism].

During the past 7 years, 15 patients with acute pulmonary embolism (APE) were treated at Kagawa Medical School and 10 patients were survived. Nine patients had an embolus in a right or left pulmonary trunk (group A) and 6 patients were peripheral APE (group B). In group A abnormal findings in a chest x-ray film and an electrocardiogram were observed in many patients, but in group B these findings were slight. In group A a shock was observed in 89% and cardiac arrest in 4 patients, although in group B neither shock nor death were observed. Marked hypoxia with hypocapnia was observed in 8 patients in group A and only in 2 in group B. All patients in group B were recovered by medical therapy. In group A, however, only 3 patients were recovered by medical therapy. Two patients in group A were performed pulmonary embolectomy (PER), but one of them, who had been in nonreversible shock, died. We conclude that the patient who had marked hypoxia (PO2 less than or equal to 50 mmHg) with hypocapnia (PCO2 less than or equal to 35 mmHg) early at an attack should be taken a pulmonary angiography, and when a large embolus is found out in the proximal pulmonary artery, the PER should be performed as soon as possible.

Acute Disease↗
PubMed1992

[Clinical profile and treatment of acute pulmonary embolism].

The clinical profiles of 15 patients with acute pulmonary embolism (APE) were analysed. The most common symptoms of APE were tachypnea and tachycardia with sudden onset. Both PO2 and PCO2 had decreased in almost all patients (mean PO2: 50 mmHg, PCO2: 30 mmHg). Chest roentgenogram (X-P) revealed hyperlucency of the lung field, prominence of proximal pulmonary artery and cardiac enlargement. ECG showed SI QIII TIII and ST-T changes in half of the cases. These changes, however, disappeared within 4 days in most patients. Lung scan and digital subtraction pulmonary angiography were useful for the diagnosis. Sixty percent of patients recovered only by medical therapy, and embolectomy was performed in only two patients. Fifty-three percent of patients were, however, considered to be candidates for the embolectomy, and half of them died because of ineffective medical therapy. From these results we concluded that the combination of severe hypoxemia and hypocapnia with abnormal chest X-P can be used for a diagnostic or therapeutic decision. If a patient has those findings, pulmonary angiography is recommended together with thrombolytic therapy. If a large embolus is detected, embolectomy is mandatory. The need for surgical therapy for APE is greater than we had imagined.

Acute Disease↗