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Biomedical subjects

K Miyatake

Publications and source records attributed to K Miyatake.

At least 217 records · Page 12Linked to original sources
PubMed1991

Detection of coronary blood flow associated with left main coronary artery stenosis by transesophageal Doppler color flow echocardiography.

Demonstration of disordered blood flow in a coronary artery may be helpful in anticipating the presence of stenosis. To examine the possibility of disordered coronary blood flow associated with left main coronary stenosis, left main coronary flow was visualized by transesophageal Doppler color flow echocardiography in 52 patients undergoing coronary angiography. Twenty patients had significant left main coronary stenosis (Group 1) and 32 patients did not (Group 2). Adequate two-dimensional echocardiographic images of the left main coronary artery were obtained in 17 patients in Group 1 and 30 patients in Group 2. Sixteen patients in Group 1, including five patients in whom the stenosis could not clearly be defined by two-dimensional echocardiography, exhibited the aliased reddish-yellowish elements producing the mosaic pattern at the stenotic or poststenotic segments, or both. In contrast, nonaliased bluish jets, suggesting laminar flow away from the transducer, were seen in echocardiograms from 27 patients in Group 2. This group included four patients with stenosis-like images on two-dimensional echocardiography. The aliased mosaic pattern was found in only three patients in Group 2 (p less than 0.01). Thus, sensitivity to detect the stenosis was improved when Doppler color flow imaging was applied. Flow velocity was significantly higher at the site of stenosis in patients in Group 1 (116 +/- 28 cm/s, n = 10, mean +/- SD) than in Group 2 (29 +/- 12 cm/s, n = 21, p less than 0.01), suggesting that the augmentation of flow velocity with or without turbulence due to the stenosis contributed to the appearance of the mosaic flow images.(ABSTRACT TRUNCATED AT 250 WORDS)

Blood Flow Velocity↗
PubMed1991

Application of Doppler color flow imaging to determine valve area in mitral stenosis.

This study was undertaken to examine whether Doppler color flow imaging could accurately estimate the valve area in mitral stenosis. Doppler color flow assessments were performed in both an in vitro model and in 30 patients with mitral stenosis undergoing cardiac catheterization. In the experimental Doppler study using a circuit model, color jet width correlated well with actual orifice diameter (r = 0.99). In the clinical Doppler study, the mitral valve orifice was assumed to be elliptic and the mitral valve area was calculated from the following equation: (pi/4) (a x b), where a = color jet width at the mitral valve orifice in the apical long-axis view (short diameter) and b = the width in the 90 degrees rotated view (long diameter). Mitral valve area was also determined by two-dimensional echocardiography and the pressure half-time method, and the results for all three noninvasive methods were compared with those obtained at cardiac catheterization. By Doppler color flow imaging, mitral valve area could be determined in all patients and there was a significant correlation between the Doppler jet and catheterization estimates of mitral valve area (r = 0.93). Valve area determined by two-dimensional echocardiography correlated well with catheterization measurements in 26 patients (r = 0.84). However, the area could not be determined in 4 (13%) of the 30 patients because of technical problems. Although there was a fair correlation between the valve area determined by the pressure half-time method and catheterization (r = 0.79), this method tended to overestimate valve area in patients with aortic regurgitation.(ABSTRACT TRUNCATED AT 250 WORDS)

Blood Flow Velocity↗
PubMed1991

Intracardiac mobile thrombus and D-dimer fragment of fibrin in patients with mitral stenosis.

OBJECTIVE: To investigate the relation between intracardiac thrombus and blood coagulability in patients with mitral stenosis. DESIGN: Prospective study. Cross sectional echocardiography and plasma concentrations of the D-dimer fragment of fibrin were used concurrently to detect intracardiac thrombus in patients with mitral stenosis. SETTING: Department of Medicine, National Cardiovascular Centre, Osaka, Japan. PATIENTS: 63 patients with mitral stenosis. None of them had been receiving any anticoagulants or antiplatelet agents. MAIN OUTCOME MEASURES: Plasma concentrations of D-dimer in patients with a mobile intracardiac thrombus, those in patients with a non-mobile intracardiac thrombus, and those in patients without an intracardiac thrombus. RESULTS: A mobile intracardiac thrombus was found in 10 patients and a non-mobile thrombus in eight. The remaining 45 patients had no intracardiac thrombi. Plasma concentrations of D-dimer in the 10 patients with a mobile thrombus were all greater than 300 ng/ml (mean 983.3, 95% confidence interval 498.9 to 1467.7 ng/ml) and they were significantly higher than those in the patients with a non-mobile thrombus (226.2, 33.6 to 418.8 ng/ml) and the patients without an intracardiac thrombus (147.2, 110.4 to 184 ng/ml). CONCLUSIONS: A high plasma concentration of D-dimer seemed to reflect a hypercoagulable intracardiac state and may be a helpful indicator of the possible presence of mobile intracardiac thrombus in patients with mitral stenosis.

Antifibrinolytic Agents↗
PubMed1991

[Prognostic significance of radionuclide-assessed right ventricular function in dilated cardiomyopathy].

To assess the prognostic significance of right ventricular function in dilated cardiomyopathy (DCM), we studied consecutive 57 DCM patients. There were 41 men and 16 women, whose mean age was 48 ys. (range 3-68 ys.). The mean LVEF in all patients was 29 +/- 11%, and the mean interval from the onset of symptom of cardiac failure (CHF history) was 4 ys. (range 0-33 ys.). With follow-up of 3.8 ys., five patients had died until the first year, and 14 had died until the third year. By using multivariate regression analysis, there were no prognostic significance in clinical parameters such as age, CHF history, sex, atrial fibrillation, except for NYHA class, and medication at the third year. In survival curves according to Kaplan-Meier method, RVEF and mean PA had predictive value (p less than 0.05), while LVEF did not. The patients with RVEF less than 45% had poor survival rate compared to those with RVEF greater than or equal to 45%. The patients with RVEF less than 45% showed lower LVEF and LVESVI. RVEF may offer prognostic predictive value through the effect of not only mean PA but also left ventricular parameter. In conclusion, radionuclide assessment of right ventricular function should be valuable for the prognostic evaluation of DCM patients.

Adolescent↗
PubMed1991

[Hemodynamic assessment before and after PTMC by using cardiac blood pool scintigraphy].

Rest and exercise cardiac blood pool scintigraphy with 99mTc-RBC were performed in 12 patients with symptomatic mitral stenosis before percutaneous transvenous mitral commissurotomy (PTMC) and at one week, one month after PTMC. Comparison of hemodynamic parameters before and one month after PTMC showed that LVEDV (97.4 +/- 8.9 vs. 111.4 +/- 12.1 ml; p less than 0.01) and diastolic indices (1/3FF: 23.6 +/- 6.5 vs. 30.9 +/- 4.1%; p less than 0.01) both increased, while there was no significant change in LVEF and RVEF. Comparison of symptom-limited bicycle exercise before and one month after PTMC showed that the duration of exercise time (7.6 +/- 1.6 vs. 8.6 +/- 1.4 min; p less than 0.02) and anaerobic threshold (10.6 +/- 3.0 vs. 15.4 +/- 3.2 ml/min/kg; p less than 0.01) increased. In comparison of hemodynamic response before and one month after PTMC, there were significant increases in cardiac output (CO) at the same workload (15 W: 3.9 +/- 0.7 vs. 4.8 +/- 0.8 l/min; p less than 0.05, 30 W: 3.9 +/- 0.7 vs. 5.2 +/- 1.2 l/min; p less than 0.05) despite similar CO at rest (3.5 +/- 0.8 vs. 3.9 +/- 0.7 l/min; NS). We conclude that cardiac blood pool scintigraphy is useful to evaluate improvement of hemodynamic parameters and exercise capacity after PTMC non-invasively.

Adult↗
PubMed1991

[Coagula tamponade as a complication of open heart surgery: the clinical significance and diagnostic value of transesophageal echocardiography].

The pathogenesis of low cardiac output failure (LOF) immediately after open heart surgery was studied in 41 patients with LOF and 15 control patients without LOF using echocardiography. In 35 patients, transesophageal echocardiography was also performed. Left ventricular (LV) contraction was impaired in 28 of the 41 LOF patients, in whom LV fractional shortening was less than 25%. In the other 13 LOF patients, however, it was greater than 25%. In 12 of these 13 patients, transesophageal echocardiography revealed that accumulating pericardial coagula were localized in the right side of the heart, deforming the right atrial and ventricular chambers. The LV end-diastolic diameter was significantly less than the control, indicating that the pericardial coagula disrupted the distension of the heart. Emergent coagulotomy was performed in 5 patients, and hemodynamic conditions were improved. In spite of "cardiac tamponade", the wall motion and pressure tracings of the right atrium and right ventricle in these patients differed from those in fluid tamponade. Therefore, this condition should be designated "coagula tamponade." In the other 22 patients in whom transesophageal echocardiography was employed, no coagula were observed. Since pericardial coagula can hardly be detected by transthoracic echocardiography, transesophageal echocardiography is indispensable for diagnosing pericardial coagula noted immediately after open heart surgery.

Adult↗
PubMed1991

[Human heart recovery during weaning from a left ventricular assist system: time course and outcome prediction].

To investigate the time course of recovery of a failing heart using the left ventricular assist system (LVAS) and to predict the outcome of weaning from the LVAS, 14 patients with a failing heart were studied. Among them, 5 had recovered and survived for more than 2 weeks after weaning from the LVAS (recovered group), while 9 could not be weaned or died within 2 weeks after weaning (unrecovered group). All patients were gradually weaned from the LVAS with adequate support for systemic circulation for 3 days. In the recovered group, indices of systolic time intervals (STIs) showed improvement within a week. However, improvement of STIs was slow reaching a plateau around the 10th day in the unrecovered group. On weaning from the LVAS, aortic systolic pressure and ejection time were regulated by the patients' own hearts and were nearly the same between the 2 groups. However, left atrial pressure was significantly higher in the unrecovered group than in the recovered group. These hemodynamic features were first present on the 7th day. Therefore, hemodynamic data on the 7th assistant day can be a reliable factor in predicting the possibility of successful weaning from the LVAS and recovery in patients with a failing heart.

Adult↗
PubMed1991

[Efficacy of transesophageal echocardiography immediately after open heart surgery: diagnosis of coagula tamponade].

Massive pericardial coagula were detected by transesophageal echocardiography in some patients with low cardiac output failure immediately after open heart surgery. Characteristically, the coagula were localized anterior to the right atrium and right ventricle in all patients. The coagula could not be detected by transthoracic echocardiography. Despite of low output, absence of wall motion abnormality of the left ventricle, tachycardia, elevated atrial pressure and small left ventricular cavity lead to diagnose cardiac tamponade by pericardial coagula. Neither the right atrial nor the right ventricular wall showed collapsing motion except the area with pericardial effusion. Massive coagula in the anterior mediastinum produced similar clinical manifestation, but could be differentiated from pericardial coagula by echographic identification of the anterior pericardium. Pericardial coagula were also observed in patients with superior vena cava syndrome, but low right atrial pressure differentiated it from coagula tamponade. In all of the present patients, usual transthoracic echocardiography did not offer any sufficient images for diagnosing pericardial coagula. Transesophageal echocardiography was indispensable for detecting pericardial coagula soon after open heart surgery.

Adult↗
PubMed1990

Pyruvate:NADP+ oxidoreductase from Euglena gracilis: mechanism of O2-inactivation of the enzyme and its stability in the aerobe.

O2-inactivation of pyruvate:NADP+ oxidoreductase from mitochondria of Euglena gracilis was studied in vitro, and a mechanism which consists of two sequential stages was proposed. Initially, the enzyme is inactivated by the direct action of O2 in a process obeying second-order kinetics. Although the catalytic activity for pyruvate oxidation is lost by this initial inactivation, NADPH oxidation with artificial electron acceptors still occurs. Subsequently, a secondary, O2-independent inactivation occurs, rendering the enzyme completely inactive. Pyruvate stimulates the O2-inactivation while CoA and NADP+ protect the enzyme from O2. The O2-inactivation is accelerated by reduction of the enzyme with pyruvate and CoA. Reactivation of the O2-inactivated enzyme was studied in Ar by incubation with Fe2+ in the presence of some other reducing reagent such as dithiothreitol. The evidence obtained indicates that the partially inactivated enzyme, which retains catalytic activity for NADPH oxidation, can be reactivated, but the completely inactivated enzyme is not. When Euglena cells were exposed to 100% O2 the enzyme in the cells was inactivated by O2, but the rate was quite slow compared with that observed in vitro. The enzyme inactivated by O2 in the cells was almost completely reactivated in vitro by incubation with Fe2+ and other reducing reagents in Ar, suggesting that the secondary, O2-independent inactivation does not occur in situ. When the cells were returned to air, reactivation of the O2-inactivated enzyme in the cells began immediately. The enzyme, kept in isolated, intact mitochondria, was stable in air; however, the enzyme was inactivated by O2 when the mitochondria were incubated with a high concentration of pyruvate.

Animals↗
PubMed1990

The effects of lying position on ventricular volume in congenital absence of the pericardium.

In patients with congenital absence of the left pericardium, the heart is supported by the existing right pericardium in the right lateral position, while it is not in the left lateral position. To investigate the change in ventricular size resulting from postural change, seven patients with this malformation were examined. Ventricular volumes were calculated by computed tomography, integrating areas of computed tomographic cross sections measured at 1 cm intervals from the cardiac apex to the aortic arch. In the right lateral position, right ventricular (RV) and left ventricular (LV) volumes were no different from those of five control subjects. With a change in the lying position to the left, the increase in the ventricular volume was significantly greater than that in the control subjects (35 +/- 11 versus 3 +/- 3 ml in the right ventricle and 15 +/- 13 versus 3 +/- 8 ml in the left ventricle). The increases in RV and LV end-diastolic pressure, however, were almost the same as those in the 11 control subjects. It is concluded that the cardiac ventricle, especially the right ventricle, dilates significantly with a small increase in preload in patients with congenital absence of the pericardium. It may be a clue for clarifying the ventricular distensibility being freed from physiologic restraint of the pericardium for a long period.

Adult↗
PubMed1990

Residual atrial septal perforation after percutaneous transvenous mitral commissurotomy with Inoue balloon catheter.

To estimate the incidence of residual atrial septal perforation (ASP) following percutaneous transvenous mitral commissurotomy (PTMC) with the Inoue balloon catheter and to examine the factors contributing to ASP, we studied 46 patients with mitral stenosis undergoing PTMC. Residual ASP was evaluated by Doppler color flow imaging 1 day after PTMC, and was detected in 7 out of 46 patients (15.2%). We examined the relationship between the development of ASP (ASP+) and the age of the patient, the left atrial dimension before PTMC, the mean pressure difference between left and right atrium after PTMC, and the duration of the procedure from atrial septal puncture by the Brockenbrough method to balloon inflation. There was a good correlation between the development of residual ASP and the duration of the procedure (ASP+, 51.0 +/- 34.0 minutes; without ASP, 24.6 +/- 16.2 minutes; p less than 0.01). However, there was no significant correlation between the development of ASP and other factors. In the follow-up study, ASP disappeared in four patients within 3 months. ASP persisted in two patients for 1 year after PTMC. However, the shunt in these two patients was clinically insignificant. These data suggest that residual ASP may depend on the duration of the procedure, and that most cases of ASP disappear within 1 year after PTMC.

Adult↗
PubMed1990

Improvement in mitral flow dynamics during exercise after percutaneous transvenous mitral commissurotomy. Noninvasive evaluation using continuous wave Doppler technique.

Evaluation of mitral flow dynamics during exercise is critically important in patients who receive percutaneous transvenous mitral commissurotomy (PTMC) because limited mitral flow during exercise provokes hemodynamic deterioration and involves cardiogenic symptoms in patients with mitral stenosis. To examine mitral flow dynamics during exercise, we applied continuous wave Doppler technique in 20 patients with mitral stenosis. Exercise Doppler study was performed 2 days before and 5 days after PTMC. PTMC increased mitral valve area from 1.0 +/- 0.3 (mean +/- SD) to 1.9 +/- 0.5 cm2 and decreased mean transmitral pressure gradient from 8 +/- 2 to 4 +/- 1 mm Hg at rest. Moreover, PTMC decreased mean transmitral pressure gradient from 21 +/- 6 to 11 +/- 4 mm Hg at submaximal exercise. The extent of an increase in mitral valve area by PTMC correlated with a decrease in the mean transmitral pressure gradient at the submaximal exercise (r = -0.76, p less than 0.01) and that at rest (r = -0.52, p less than 0.05). Heart rate after PTMC during exercise was significantly lower than that before PTMC, indicating that the compensatory mechanism (tachycardia) to increase cardiac output during exercise is less necessary after PTMC. Thus, we conclude that the mitral flow dynamics during exercise is improved, as well as the resting mitral flow dynamics 5 days after PTMC, and that exercise Doppler study enabled us to make a noninvasive evaluation of the mitral flow dynamics in patients who receive PTMC.

Adult↗
PubMed1990

[Doppler echocardiographic features of the atrial and ventricular filling modes and their significance in restrictive myocardial diseases].

The filling modes into the right atrium and both ventricles were observed using pulsed Doppler echocardiography in six cases of restrictive myocardial diseases, and these were compared with those of 13 cases of constrictive pericarditis, six cases of lone atrial fibrillation and 16 healthy subjects. Special attention was paid to the mechanical properties of the cardiac walls which might be reflected in the filling modes. 1. In the restrictive cases, right atrial filling from the superior caval vein during ventricular systole was reduced in velocity and duration, but the atrial filling during ventricular diastole was not appreciably changed. This flow pattern was similar to that of lone atrial fibrillation, indicating reduced distensibility or impaired contraction and ejection fraction of the right atrium. In constrictive pericarditis, the right atrial filling time was shortened both in ventricular systole and diastole, reflecting stiffening of the pericardium. 2. In the restrictive cases, the first half of the left ventricular rapid filling wave was steep and the skirt of the descending limb was prolonged, while there was no such tendency in the right ventricle. In constrictive pericarditis, the rapid filling time was shortened in the right ventricle, and was not significantly changed in the left ventricle. 3. The differences in the atrial and ventricular filling patterns between restrictive myocardial disease and constrictive pericarditis may serve to distinguish these two disease entities.

Adult↗
PubMed1990

[Venous return and collapse of the right heart in cardiac tamponade].

To elucidate the characteristics of venous inflow into the heart in cardiac tamponade, transmitral (TMF), transtricuspid (TTF) and superior vena cava (SVC) flows were examined using pulsed Doppler echocardiography in nine mongrel open-chest dogs. Cardiac tamponade was produced by the slow infusion of warmed normal saline into the pericardial sac. With increment of pericardial infusion, right atrial collapse (RAC) developed followed by right ventricular collapse (RVC). The systemic blood pressure became depressed and the left ventricular end-diastolic diameter decreased, even in the RAC state, indicating that RVC is not of the primary significance for cardiac tamponade. Characteristically, peak velocities of TMF and TTF in early diastole decreased concomitantly with RAC and RVC. Neither early diastolic filling time nor its acceleration time was altered during tamponade. These changes in blood flow were accompanied by decrements of transmural filling pressure and abnormal motion of the right ventricle. In SVC flow, the diastolic wave characteristically disappeared. This change seemed to be a reflection of the decrease in peak velocity of early diastolic filling flow into the right ventricle. That is, impairment of cardiac relaxation during cardiac tamponade is represented as decreased filling flow velocity in early diastole.

Animals↗
PubMed1990

[Progression of idiopathic mitral valve prolapse estimated by echocardiography].

To evaluate the progression of idiopathic mitral valve prolapse (MVP), a long time follow-up study (mean 7.1 years) was performed using echocardiography in 27 cases (11 males, 16 females, mean age: 50.4 years). Morphological changes, the degree of prolapse of the mitral valve, left atrial dimension (LAD) and left ventricular end-diastolic dimension (LVDd) were estimated at the first and last examinations. The degree of prolapse was assessed by measuring the distance of the dislocation between the anterior and posterior leaflets at the area of coaptation (degree I:5 mm or less, degree II: 6 to 10 mm, degree III: 11 mm or greater). The results were as follows: 1. The degree of prolapse did not progress in all 27 cases. 2. LAD increased with an advance of age. A remarkable increase of LAD was recorded in cases older than 45 years with atrial fibrillation or prolapse of degree II and III or with ruptured chordae tendineae. 3. The mitral ring was enlarged over 5 mm in six of 15 cases with prolapse of degree II and III. 4. Mitral regurgitation evaluated by Doppler echocardiography in patients with posterior leaflet prolapse was more severe than that in patients with anterior leaflet prolapse in the last examination. 5. LVDd increased gradually. In the present study, LAD was increased in most cases of MVP and it seemed to depend on complications (atrial fibrillation and ruptured chordae tendineae) or severity of regurgitation rather than the degree of prolapse.

Adult↗
PubMed1989

Pyruvate:NADP+ oxidoreductase from Euglena gracilis: the kinetic properties of the enzyme.

The kinetic properties for the native forward reaction of pyruvate:NADP+ oxidoreductase from Euglena gracilis were determined. The substrate kinetics gave a pattern of a ping-pong mechanism involving a competitive substrate inhibition of CoA against pyruvate. The Km values for pyruvate, CoA, and NADP+ were estimated to be 27, 6.6, and 28 microM, respectively, and the Ki value of CoA against pyruvate was 28 microM. CO2 inhibited noncompetitively against pyruvate and NADP+, and uncompetitively against CoA. Acetyl-CoA showed a competitive inhibition with respect to pyruvate and an uncompetitive inhibition with respect to NADP+. NADPH inhibited competitively versus NADP+, noncompetitively versus CoA, and uncompetitively versus pyruvate. The kinetic behavior is consistent with a two-site ping-pong mechanism involving the substrate inhibition. From the kinetic mechanism, it is proposed that the enzyme has two catalytic sites linked by an intramolecular electron-transport chain. One of these is a thiamine pyrophosphate-containing catalytic site which reacts with pyruvate and CoA to form CO2 and acetyl-CoA, and the other site functions in the reduction of NADP+. In contrast, when methyl viologen was used as an artificial one-electron acceptor substituting for NADP+, the reaction gave a pattern characteristic of an octa uni ping-pong mechanism involving a competitive substrate inhibition of CoA against pyruvate.

Animals↗
PubMed1989

Diastolic atrioventricular valve closure and regurgitation following atrial contraction: their relation to timing of atrial contraction.

Some authors have proposed that atrial contraction per se is able to close the atrioventricular (AV) valves. To determine whether tight closure of the AV valves can be accomplished solely by atrial contraction, the existence of diastolic regurgitation following atrial contraction and its relation to the PQ interval were examined in 13 patients with AV block (2 of the first degree, 4 of the second degree, and 7 of the third degree), using pulsed Doppler echocardiography, which allowed noninvasive estimation of valvular regurgitation in the physiological state. Diastolic mitral and tricuspid regurgitations were detected in the left and right atria near the respective AV valves in all 13 patients despite different degrees of AV block, while these valves were observed to be in apparently closed position during regurgitation on the two-dimensional and M-mode echocardiograms. The duration of regurgitant signals was prolonged with an increase in the PQ interval in the electrocardiogram, but it became short again as the P wave approached the preceding rapid filling wave. These results suggest that atrial contraction may initiate the closure of the AV valves but is not capable of closing the valves tightly, and atrial contraction with long PQ interval may contribute little to augmentation of cardiac output in patients with AV block.

Echocardiography, Doppler↗