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Biomedical subjects

K Miyatake

Publications and source records attributed to K Miyatake.

At least 235 records · Page 13Linked to original sources
PubMed1989

Hemodynamic and prognostic value of thallium-201 myocardial imaging in patients with dilated cardiomyopathy.

We studied 70 patients with dilated cardiomyopathy to determine whether extent of perfusion defect on thallium imaging could be related to the hemodynamics and prognosis of the patients. Patients were divided into three groups according to the extent of perfusion defect, i.e., Grade I: no perfusion defect (n = 19), Grade II: apical perfusion defect (n = 22), and Grade III: extensive perfusion defect (n = 29). The patients of Grade III demonstrated marked hemodynamic deterioration compared with those of Grade I and II. Three-year survival rate showed lower value in proportion to the extent of perfusion defect (P less than 0.05). Death from progressive heart failure tended to occur in patients with extensive perfusion defect (P less than 0.05). In patients of Grade III, the perfusion defect extended mainly to the posterolateral segment. Although autopsy studies showed increased fibrosis in the left ventricular wall in these patients, the extension of the fibrosis was not related to that of fibrosis. Moreover, the perfusion defect had regressed in three of 18 patients in the follow-up examination. These results indicate that the extent of perfusion defect on thallium imaging may be of value in non-invasive evaluation and prediction of the prognosis in patients with dilated cardiomyopathy. Distribution of the perfusion defect was, however, not related to that of myocardial fibrosis.

Adolescent↗
PubMed1989

Occurrence and characterization of fructose 6-phosphate, 2-kinase and fructose 2,6-bisphosphatase in Euglena gracilis.

1. Fructose 6-phosphate, 2-kinase and fructose 2,6-bisphosphatase occurred in Euglena gracilis SM-ZK, and is located in cytosol. 2. Fructose 6-phosphate, 2-kinase and fructose 2,6-bisphosphatase were partially purified, and both enzyme activities were not separated during the partial purification. 3. The pH optimum for fructose 6-phosphate, 2-kinase activity was 7.0. The saturation curve of the enzyme activity for ATP concentration was hyperbolic, and the Km value for the substrate was 0.88 mM. On the other hand, the saturation curve of the enzyme activity for fructose 6-phosphate concentration was sigmoidal, and the K0.5 value for the substrate was 70 microM. 4. The pH optimum for fructose 2,6-bisphosphatase activity was 6.5. The saturation curve for fructose 2,6-bisphosphate concentration was sigmoidal, and the K0.5 value for the substrate was 1.29 microM. Fructose 2,6-bisphosphate showed a substrate inhibition at high concentration over 5 microM, and the enzyme activity was completely inhibited by 20 microM of fructose 2,6-bisphosphate.

Animals↗
PubMed1989

Visualization of coronary blood flow by color Doppler imaging with a transesophageal approach.

To examine whether CBF can be imaged by color Doppler technique, we visualized CBF using a transesophageal color Doppler imaging system. In 36 of 39 patients with normal coronary arteriograms after heart surgery, the LMT and the proximal LAD were clearly imaged by 2-dimensional echocardiography. Among them, CBF was coded mainly in blue in 32 patients, showing that the flow runs from proximal to distal. In some cases, yellowish and/or reddish components were seen, suggesting the occurrence of aliasing associated with augmentation of flow velocity or flow turbulence. The fast Fourier transformation spectrogram of the pulsed Doppler sampled in the colored flow showed a typical flow velocity pattern of the LAD, which mainly consisted of a predominantly diastolic component. These results indicate that the transesophageal color Doppler technique is advantageous in noninvasively imaging CBF. It should be further sought whether flow abnormality due to coronary stenosis could be determined by this technique.

Adult↗
PubMed1989

Role of echocardiography in acute pulmonary embolism.

The difficulty in making an accurate diagnosis of acute pulmonary embolism is well known. To clarify the role of echocardiography, including Doppler echocardiography, in acute pulmonary embolism, we examined hemodynamic and echocardiographic parameters in 9 patients with acute pulmonary embolism just before and after treatment with urokinase. As hemodynamic parameters normalized after treatment, echocardiographic parameters such as deformity index of the left ventricle (LV-DI), end-diastolic dimension of the right ventricle (RVDd), the left ventricle (LVDd), the inferior vena cava, and RVDd/LVDd all significantly changed toward normal. Highly significant correlations were found between the echocardiographic and hemodynamic parameters, the best of which was between the LV-DI and systolic pulmonary artery pressure (r = -0.885, p less than 0.001). Doppler echocardiography quantitatively evaluated the grade of tricuspid regurgitation, and accurately estimated systolic pulmonary artery pressure. We conclude that echocardiography, including Doppler echocardiography, sensitively reflects the right ventricular pressure and volume overload of acute pulmonary embolism, is quite useful for its diagnosis which is often difficult, and is suitable for noninvasive follow up of these patients.

Acute Disease↗
PubMed1989

Cine MR imaging in mitral regurgitation: comparison with color Doppler flow imaging.

Cine MR imaging is a new technique that combines short repetition times, limited flip angles, gradient-refocused echoes, and cardiac gating. This procedure was performed in 20 patients in whom mitral regurgitation was shown on left ventriculography, and the results were compared with those of color Doppler flow mapping. In all cases, mitral regurgitation on cine MR imaging was depicted as an area of decreased signal intensity within the left atrium. The extent and severity of the regurgitant jet as seen by the two techniques were classified visually as 4+ (severe), 3+ (moderate), 2+ (mild), and 1+ (minimal). The results of the two methods were the same in 14 (70%) of the 20 patients. In five patients the results differed by one grade and in one patient by two grades. In addition, the maximal intrusion distance and area of the regurgitant jet divided by the area of the left atrium as determined by the two methods were compared. The correlation coefficients between the two methods in regard to the length and area of mitral regurgitation were .74 and .71, respectively. These data suggest that the accuracy of cine MR imaging in assessing the severity of mitral regurgitation is comparable to that of color Doppler flow imaging.

Adult↗
PubMed1989

[Significance of disturbances of cardiac filling in constrictive pericarditis].

Using pulsed Doppler echocardiography, blood filling patterns of the right atrium and left and right ventricles in constrictive pericarditis were studied to evaluate the physiological role of the pericardium in the hemodynamics of this disease. Thirteen cases were examined including five cases with atrial fibrillation. The control subjects consisted of 16 healthy persons and six cases of lone atrial fibrillation. 1. Peak velocity of the atrial filling wave during ventricular systole was reduced, and the filling time was shortened, suggesting reduced compliance and restricted motion of the atrial wall, because of the thickening and adhesions of the pericardium. Duration of the atrial filling wave during ventricular diastole was also shortened, reflecting disturbance of the early diastolic filling of the right ventricle. 2. In healthy subjects, duration of the rapid filling wave was longer in the right ventricle than in the left ventricle, probably due to the greater compliance of the right ventricular wall as compared to that of the left ventricular wall. In constrictive pericarditis, the rapid filling time of the right ventricle is shortened, so that the difference in this time between the right and left ventricles is minimized, which may be related to a thinner right ventricular wall. Duration of the rapid filling wave of the right ventricle correlated with right ventricular end-diastolic pressure, indicating that the duration of the right ventricular rapid filling wave is proportional to the severity of constrictive pericarditis. In conclusion, constriction of the pericardium definitely influences the hemodynamics of the right side of the heart more than it does the left side in constrictive pericarditis. This difference appears to result from the difference in thickness of the myocardial layers of both ventricles.

Adult↗
PubMed1989

[Doppler echocardiographic estimates of pressure gradients in various types of stenoses: usefulness and limitations].

UNLABELLED: In the present study, the accuracy of Doppler estimates of pressure gradients in various types of stenoses was clinically and experimentally evaluated. Fifty-seven patients, including 23 with ventricular septal defect, 15 with aortic or pulmonary valvular stenosis, four with infundibular stenosis, and five with supravalvular aortic or pulmonary stenosis were observed. The peak systolic pressure gradient (dP (C] was obtained at the time of catheterization in all patients. Before catheterization, the maximum velocity was measured by pulsed or continuous Doppler echocardiography and the estimated systolic pressure gradient according to Doppler (dP (D] was calculated by the simplified Bernoulli equation. The experimental model was designed to create pulsatile flow through a stenosis model. Nine different stenotic model types were used, including three orifice-like stenoses and six truncated cones with heights of 10 mm and 20 mm distal to the stenosis. The orifices in their stenoses were 3, 4 and 5 mm, respectively. Glycerin solution containing Sephadex with a viscosity similar to that of blood was used as the circulation medium. Its specific gravity was 1.16 g/cm3. In each stenotic model, the maximum velocity and instantaneous systolic peak pressure gradient were measured at various water flow rates. CLINICAL RESULTS: In patients with ventricular septal defect or valvular stenosis, dP (D) correlated very well to dP (C), with the regression equation, y = 0.87x + 2.79 (r = 0.92) or y = 0.96x + 1.02 (r = 0.99). In the other patients except for three with patent ductus arteriosus, dP (D) overestimated dP (C) by 11 to 71 mmHg, and their post-stenotic areas had gradually widened according to angiographic findings.(ABSTRACT TRUNCATED AT 250 WORDS)

Aortic Stenosis, Subvalvular↗
PubMed1989

[Cine MR imaging in valvular heart disease].

Cine MR Imaging was carried out using FLASH (fast low angle shot) which employees TE of 16 msec and TR of 30-40 msec. Regurgitant jet was visible as discrete area of low signal intensity extending from the incompetent valve into the respective cardiac chamber. In 20 patients with mitral regurgitation, the correlation of the length and area of mitral jet by cine MR and color doppler mapping was 0.74 and 0.71, respectively. Cine MR imaging is a promising modality for detection and quantification of valvular heart disease.

Aged↗
PubMed1988

The computerized derivation of rate equations for enzyme reactions on the basis of the pseudo-steady-state assumption and the rapid-equilibrium assumption.

A computer program is developed for the derivation of the rate equation for enzyme reactions on the basis of the pseudo-steady-state assumption and the combination of the pseudo-steady-state and the rapid-equilibrium assumptions. The program not only has an easy input method, but also can obtain a complete rate equation in itself on only one run. The usefulness of the program is demonstrated by deriving the rate equations for some typical enzyme reactions. Details of the program have been deposited as Supplementary Publication SUP 50141 (42 pages) at the British Library Lending Division, Boston Spa, Wetherby, West Yorkshire LS23 7QB, U.K., from whom copies may be obtained as indicated in Biochem. J. (1988), 249, 5.

Computer Simulation↗
PubMed1988

Visualization of isolated conus artery as a major collateral pathway in patients with total left anterior descending artery occlusion.

To examine the existence of isolated conus artery (ICA) as a source of collateral circulation, we selectively visualized the ICA in patients with left anterior descending coronary artery (LAD) occlusion using a no. 5 French catheter. One hundred and fifty patients with a total LAD occlusion were selected from 639 consecutive patients who had diagnostic coronary angiography during an 18-month period; the ICA was found in 45 patients. Among these patients, 30 showed the ICA as a collateral vessel supplying the distal LAD. In nine of these patients, conventional left and right coronary angiography did not reveal any other significant collateral vessels, and the distal LAD was perfused mainly by the collaterals from the ICA. No serious complications such as ventricular fibrillation or myocardial infarction occurred during these procedures. These results indicate that the selective ICA visualization is clinically important when conventional left and right angiography does not demonstrate collaterals to the obstructed LAD.

Angiocardiography↗
PubMed1988

Doppler echocardiographic approach to the blood flow of the left anterior descending coronary artery.

Assessment of flow in the left anterior descending coronary artery by Doppler echocardiography appeared to be possible in some patients in which the coronary artery system might be wide and/or the displacement of the coronary artery might be reduced because of cardiac enlargement or of impaired cardiac function. A study of this possibility was carried out in 78 patients, 20 cases with hypertrophic cardiomyopathy, 10 with dilated cardiomyopathy, 20 with aortic valve disease, and 28 following valve replacement for aortic valve disease. The anterior interventricular sulcus was a helpful landmark to search for the left anterior descending artery. The characteristic feature of the coronary flow pattern, that the flow ran mainly during diastole, was also helpful in finding the coronary artery. Complementary roles of ultrasonic imaging and Doppler ultrasound evaluation should be emphasized for identifying a thin echo-free space in the sulcus as the coronary artery. The left anterior descending coronary artery was imaged in 26 of the 78 patients. The peak velocity ranged 24 cm/s to 75 cm/s in different patients. Because the present study was carried out in patients with some particular diseases, these results do not indicate that current techniques can be routinely used for assessing the coronary flow. The detection rate will be increased with improvements in image resolution and the Doppler sensitivity. Although the detection rate of the coronary artery was not satisfactory in the present stage, the effect of sublingual administration of nitroglycerin on coronary circulation was noninvasively assessed in some patients, where reduction of the flow velocity by about 27% was observed in real time.

Adolescent↗
PubMed1988

Clinical implications of pulmonary regurgitation in healthy individuals: detection by cross sectional pulsed Doppler echocardiography.

Pulsed Doppler echocardiography in healthy individuals often shows a disturbance of diastolic flow in the right ventricular outflow tract just below the pulmonary valve that suggests regurgitation. This disturbance of diastolic flow was studied in 50 healthy individuals and 40 patients with cardiopulmonary disease, some of whom had a pulmonary regurgitant murmur. Diastolic flow was disturbed in 39 of the 50 healthy individuals. In 32, cross sectional echocardiography gave a satisfactory image of the pulmonary valve. The characteristic Doppler signals usually lasted throughout diastole, were directed toward the right ventricular cavity, and gradually waned towards end diastole; they formed a spindle shaped area of abnormal signals that extended to within 10 mm of the coaptation of the pulmonary valve towards the right ventricular cavity and the pressure difference estimated from the signals by the modified Bernoulli equation seemed to be proportional to the normal retrograde transpulmonary pressure difference. In all 40 patients with cardiopulmonary disease, signals indicating pulmonary regurgitation were found whether or not a regurgitant murmur was present. When it was present, however, the spindle was longer than 20 mm and in patients with pulmonary hypertension the velocity of abnormal diastolic flow was higher than in healthy individuals. The Doppler signals registering disturbed flow in the healthy individuals resembled the signals caused by pulmonary regurgitation in the patients in terms of location, orientation, and configuration. These results show that healthy individuals usually have trivial pulmonary regurgitation. In practice the distance that the flow disturbance extends from the valve and estimated pressure difference across the valve are probably the most important variables for assessing the clinical significance of pulmonary valve regurgitation.

Adult↗
PubMed1988

Transient abnormal septal motion after non-surgical closure of the ductus arteriosus.

Abnormal septal motion on M mode echocardiography was seen in eight of 16 patients soon after non-surgical closure of the ductus arteriosus. Ten to twenty-nine months after the procedure the abnormal septal motion had disappeared spontaneously. The cross section of the left ventricular cavity was circular both when septal motion was abnormal and when it was normal. Cross sectional echocardiography showed that there was an exaggerated anterior swinging motion of the heart in systole in patients with abnormal septal motion on the M mode recordings. The left ventricular end diastolic diameter before closure was significantly larger, and its reduction after closure was more pronounced in those with abnormal septal motion than in those without. This suggested that the abnormal septal motion was associated with relief of long standing left ventricular volume overload. It is suggested that acute shrinkage of the heart caused temporary laxity of the pericardium, and consequently more movement of the heart within the thorax. The return of normal septal motion suggests that the pericardium gradually shrank to accommodate the smaller heart.

Adult↗
PubMed1988

Abnormal blood pathways in left ventricular cavity in acute myocardial infarction. Experimental observations with special reference to regional wall motion abnormality and hemostasis.

To elucidate the mechanism of regional hemostasis in the left ventricular (LV) cavity during myocardial infarction, the blood pathway in LV cavity was examined with contrast echocardiography injected from the left atrium before and after coronary ligation in nine canines. Before coronary ligation, contrast echoes spread over LV cavity with one rush. After ligation, smokelike echoes indicating hemostasis were observed at the apical middle of the LV cavity in five dogs with apical akinesis and at the apical area in four dogs with apical dyskinesis. The contrast echoes did not reach the apex within one diastolic period but turned upward to the outflow tract in the middle of the cavity in all dogs. In the cardiac beats that followed, some contrast echoes spread slowly toward the apex, forming a thin layer along the posterior wall in cases with akinesis but not in cases with dyskinesis. The area separated from the blood pathway developed where the smokelike echoes had been developed. Tachycardia exaggerated the abnormality of blood pathway and widened the contrast echo-free area. The abnormal pathway of the blood in apical myocardial infarction develops hemostasis in the apex. This should be one of the mechanisms of thrombus formation in myocardial infarction.

Animals↗