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Biomedical subjects

T Takamoto

Publications and source records attributed to T Takamoto.

At least 37 records · Page 2Linked to original sources
PubMed1997

Severity of coronary artery calcification detected by electron beam computed tomography is related to the risk of restenosis after percutaneous transluminal coronary angioplasty.

To assess the relationship between coronary artery calcification and the late success rate of percutaneous transluminal coronary angioplasty (PTCA), we performed electron beam computed tomography (EBCT) in 22 patients with ischemic heart disease who underwent PTCA. The calcification score in each coronary artery vessel was estimated and compared with the occurrence of restenosis at 3 months after PTCA. Angioplasty had been performed in 28 sites in 22 patients, and 12 sites exhibited restenosis. The mean calcium score in the unsuccessful PTCA vessels was significantly higher than in successful sites (228 vs 92). The overall late success rate of PTCA with moderate to severe calcification was extremely low at 29%. Coronary segments with diffuse and extensive calcification were not optimal target lesions for PTCA. Prediction of the late success rate after PTCA may be possible by prior evaluation of coronary artery calcification utilizing EBCT.

Aged↗
PubMed1997

Left ventricular hypertrophic patterns and wall motion dynamics in hypertrophic cardiomyopathy: an electron beam computed tomographic study.

To investigate the left ventricular hypertrophic patterns and wall motion dynamics in hypertrophic cardiomyopathy, 51 patients were studied using electron beam computed tomography. The subject consisted of 26 asymmetrical hypertrophy, 9 diffuse hypertrophy, 14 apical hypertrophy and 2 papillary muscle hypertrophy. Concerning the wall motion dynamics in hypertrophic wall, 7 demonstrated homogeneous wall thickening involving the non-hypertrophic wall, 36 showed decrease wall thickening, 6 showed normal wall thickening, and 2 cases of papillary muscle hypertrophy had increased wall thickening in the apical wall. The percent wall thickening in hypertrophic wall was significantly reduced in relation to the increase of wall thickness; 14 +/- 8% in the wall over 20 mm, 23 +/- 12% in 16-9 mm and 56 +/- 36% in 13-15 mm. The reduced wall motion dynamics in hypertrophic wall were clearly observed by electron beam computed tomography.

Adult↗
PubMed1997

A left atrial myxoma complicated with acute myocardial infarction.

A 43-year-old female, admitted because of acute infero-posterior myocardial infarction, showed angiographic findings of 100% occlusion of left circumflex artery. Echocardiographic findings showed inferior hypokinesis, while a large left intraatrial tumor was also observed. The coronary angiography on the 17th hospital day showed complete reperfusion of the culprit lesion without stenosis. On the 21st hospital day, the removal operation of the tumor was performed. Pathological findings showed typical cardiac myxoma, and the etiology of the occlusion at the culprit vessel was presumed to be closely related to the existence of the left atrial tumor.

Adult↗
PubMed1996

Large right ventricular myxoma in a 79-year-old male.

A 79-year-old male, admitted because of severe dyspnea on exertion, showed echocardiographic findings of a large tumor in the dilated right ventricle. The right ventricular outflow tract was nearly occluded by the tumor mass, and the mass was attached to the interventricular septum by a pedicle. The tumor removal operation was successful. The size of the tumor was 40 mm x 90 mm, and the weight 70 g. Microscopic findings showed typical myxomatous tissue with high cellularity, and no malignancy was observed. This is the oldest reported patient with right ventricular myxoma which was cured by operation.

Aged↗
PubMed1995

Decrease of optic disc cupping and pallor of ocular hypertensives with timolol therapy.

PURPOSE: The purpose of this study was to determine whether timolol drops compared to placebo drops had a significant effect on optic disc cupping and pallor in ocular hypertensives. METHODS: Thirty-seven ocular hypertensives were randomly assigned to placebo or 0.5% timolol drops to both eyes in a double masked clinical trial. Measurements of ocular pressure and photographs of the optic disc for cupping by photogrammetry and pallor by computerized image analysis were made at about 3 month intervals, for 18 to 24 months of follow-up. RESULTS: None of the subjects developed visual field loss when tested with the Goldmann perimeter by kinetic and static means at six month intervals. Subjects treated with timolol developed a significant decrease in ocular pressure and a significant decrease in optic disc cupping with a smaller decrease in pallor compared to subject treated with placebo. Multivariate analyses indicated that the decrease of optic disc cupping and pallor was not associated with the ocular pressure on treatment or the decrease in ocular pressure during the trial. CONCLUSION: Timolol treatment was associated with a decrease in optic disc cupping and pallor. The effect of timolol appears to be related to mechanisms other than the decrease in ocular pressure.

Double-Blind Method↗
PubMed1995

Increase of retinal nerve fiber layer thickness in ocular hypertensives with timolol therapy.

PURPOSE: The purpose of this study was to determine whether timolol drops compared to placebo drops had a significant effect on retinal nerve fiber layer thickness in ocular hypertensives. METHODS: Thirty-seven ocular hypertensives were randomly assigned to receive placebo or 0.5% timolol drops to both eyes for 18 to 24 months in a double masked clinical trial. Measurements of ocular pressure and photographs of retinal nerve fiber layer using stereophotogrammetric techniques were made at about 3 month intervals for 18 to 24 months of follow-up. RESULTS: None of the subjects developed visual field loss when tested with the Goldmann perimeter by kinetic and static means at six month intervals. Subjects treated with timolol had a significant decrease in ocular pressure and developed a significant increase in retinal nerve fiber layer thickness compared to subjects treated with placebo. Multivariate analyses indicated that the increase of retinal nerve layer thickness was not associated either with the ocular pressure on treatment or the decrease in ocular pressure on treatment. CONCLUSION: Timolol treatment was associated with an increase of retinal nerve fiber thickness. The effect of timolol appears to be related to mechanisms other than the decrease in ocular pressure.

Double-Blind Method↗
PubMed1995

Increase of retinal vessel width in ocular hypertensives with timolol therapy.

PURPOSE: The purpose of this study was to determine whether timolol drops compared to placebo drops had a significant effect on retinal vessel width in ocular hypertensives. METHODS: Thirty-seven ocular hypertensives were randomly assigned to receive placebo or 0.5% timolol drops to both eyes for 18 to 24 months in a double masked clinical trial. Measurements of ocular pressure and retinal vessel width by computerized image analysis from fundus photographs were made at about 3 month intervals for 18 to 24 months of follow-up. RESULTS: None of the subjects developed visual field loss when tested with the Goldmann perimeter by kinetic and static means at six month intervals. Subjects treated with the placebo showed no change in ocular pressure and a significant decrease in retinal vessel width over time especially in the right eye. Subjects treated with timolol had an increase in retinal vessel width compared to the placebo group significant especially for the superior temporal vein. Multivariate analyses indicated that the increase of retinal vessel width was not associated mainly with the ocular pressure on treatment or decrease in ocular pressure on treatment. CONCLUSION: Timolol treatment was associated with an increase of retinal vessel width. The effect of timolol appears to be related primarily to mechanisms other than the decrease in ocular pressure.

Double-Blind Method↗
PubMed1995

Optic nerve head circulation in untreated ocular hypertension.

AIMS: The laser Doppler technique was used to compare the capillary blood speed measured at localised sites of the optic nerve head in stable, untreated ocular hypertensive patients with that measured in healthy normal subjects. The stereophotogrammetric technique was also used to measure the retinal nerve fibre layer thickness at the disc margin in the eyes of the patients. METHODS: Doppler broadening measurements were made at superior and inferior temporal disc sites in 18 eyes of 10 ocular hypertensive patients and in 12 eyes of seven age and sex-matched normal subjects. RESULTS: On average, Doppler broadening and, hence, capillary blood speed were significantly higher (p = 0.018) in the patients than in the normal subjects. The largest values of Doppler broadening in the patients were measured at sites adjacent to the thinnest retinal nerve fibre layer. Linear regression analysis showed a significant inverse relation (p = 0.0004) between Doppler broadening and nerve fibre layer thickness in left eyes, and a nearly significant relation (p = 0.06) in right eyes. At temporal sites of the optic nerve head there is a compensatory relation between a thinning nerve fibre layer and a locally increasing blood supply to the optic nerve head. CONCLUSION: Together with previous observations of fluorescein filling defects in similar patients, these results indicate that there is spatial heterogeneity of blood flow in the optic nerve head in stable, untreated ocular hypertensive patients.

Adult↗
PubMed1994

Postprandial hemodynamic changes evaluated by a Doppler echocardiographic method.

To evaluate postprandial hemodynamic changes, Doppler measurements of stroke volume before and after lunch were carried out in 10 healthy volunteers (all men) with a mean age of 28 years. The stroke volume was calculated as the product of echocardiographically determined aortic valve area and the ejection flow velocity integral obtained by continuous wave Doppler. The stroke volume before lunch was 61 +/- 7 ml, which was increased to 72 +/- 8 ml 1 hour after lunch and remained constant for the next 4 hours. Five hours later the stroke volume was then decreased to the baseline. M-mode echocardiography revealed an increase in left ventricular end-diastolic dimension and ejection fraction after lunch. Another 9 healthy subjects (6 women and 3 men) with a mean age of 52 years received a 75 g oral glucose tolerance test (OGTT) instead of a common lunch; stroke volumes were not altered in association with the elevation of plasma glucose level. In conclusion, ingestion of food had a positive inotropic effect and caused circulating blood volume expansion with an increment of heart rate. Therefore, Doppler studies that are not standardized for patients' mealtimes may affect the validity of data in serial studies of left ventricular function.

Adult↗
PubMed1993

Laser scanning tomography and stereophotogrammetry in three-dimensional optic disc analysis.

Laser scanning tomography (LST) and computed stereophotogrammetry (CSP) are sophisticated diagnostic tools for the three-dimensional analysis of optic nerve head topography. The two methods are based on different physical principles. To compare the information about the shape of the cup of an optic nerve head obtained by LST and CSP, we evaluated the volume profile (VP; i.e., the cross-sectional area of the cup from top to bottom) in 36 discs of 36 patients (20 control group discs C, 16 glaucoma discs G). The Spearman correlation coefficient between the photogrammetric and the laser scanning VP-slope measurements was rs = 0.931; P < 0.001 (rs = 0.935 G, P < 0.001; rs = 0.910 C, P < 0.001). The results suggest that confocal laser scanning provides readings of the shape of the optic disc cup that are similar to the measurements of computed stereophotogrammetry.

Adolescent↗
PubMed1993

Differences of retinal nerve fiber layer thickness between normal and glaucoma-like optic disks (physiological cups) matched by optic disk area.

We matched by disk area size 23 eyes of patients with glaucoma-like disks (physiological cups) with normal ocular pressures and no visual field loss with 23 eyes of normal subjects. Using stereophotogrammetry we found a significant decrease in retinal nerve fiber layer thickness in the eyes with glaucoma-like disks compared to the normal eyes (P = 0.0081), especially in the nasal quadrant (18.1%). A similar significant decrease was noted in the neuroretinal rim area and a significant increase in cup volume, area, depth and slope for the total disk and its quadrants. The use of computerized image analysis also showed a significant increase in pallor area for glaucoma-like disks compared to normal disks. Eyes with glaucoma-like disks or physiological cups showed evidence of an optic neuropathy and may be manifesting the same damage to the optic nerve occurring in high pressure open angle glaucoma.

Aged↗
PubMed1992

Anaerobic metabolism as an indicator of aerobic function during exercise in cardiac patients.

To determine whether patients with heart disease depend more than normal subjects on anaerobic metabolism to perform the same level of exercise, the anaerobic threshold, slope of the increase in carbon dioxide output with respect to oxygen uptake (delta VCO2/delta VO2) and the slope of the increase in oxygen uptake with respect to the increase in work rate (delta VO2/delta WR) both below and above the anaerobic threshold during exercise were evaluated. A total of 106 patients with chronic heart disease and 42 healthy subjects performed a symptom-limited incremental exercise test in a ramp pattern on a cycle ergometer. Peak oxygen uptake was significantly lower in the patients with heart disease than in the normal subjects. The anaerobic threshold, which was 20 +/- 4.6 ml/min per kg in normal subjects, decreased significantly with progressing severity of functional class: 16 +/- 2.4, 14.1 +/- 2.5 and 11.3 +/- 1.5 ml/min per kg, respectively, in patients in class I, class II and class III. The slope of delta VO2/delta WR, which represents the degree of aerobic metabolism, was also decreased both below and above the anaerobic threshold with increasing severity of heart disease. delta VCO2/delta VO2 below the anaerobic threshold was approximately 0.9 (p = NS between normal subjects and patients). However, delta VCO2/delta VO2 above the anaerobic threshold became steeper with increasing severity of heart disease: 1.37 +/- 0.17 in normal subjects versus 1.55 +/- 0.24, 1.67 +/- 0.3 and 1.8 +/- 0.35 respectively, in patients in functional class I, class II and class III.(ABSTRACT TRUNCATED AT 250 WORDS)

Aerobiosis↗
PubMed1992

Cardiac output-O2 uptake relation during incremental exercise in patients with previous myocardial infarction.

BACKGROUND: The cardiac output-O2 uptake (VO2) relation, which is thought to be linear and predictable in normal humans, has not been clarified in cardiac patients. We evaluated the relation between cardiac output and VO2 during the incremental exercise test in patients with previous myocardial infarction. METHODS AND RESULTS: Twenty-two patients (age, 58.1 +/- 8.0 years) with previous myocardial infarction performed a symptom-limited exercise test on a cycle ergometer. VO2 was calculated from the expired gas analysis, and cardiac output was measured by a computerized cadmium telluride detector every 10 seconds during exercise. The ratio of increase in VO2 to the increase in work rate (delta VO2/delta WR) below and above the anaerobic threshold (AT) was 11.1 +/- 3.6 and 11.1 +/- 2.9 ml/min/W, respectively, showing no significant difference. However, the ratio of increase in cardiac output to increase in work rate (delta CO/delta WR) below the AT was 50.1 +/- 26.6 ml/min/W and was significantly decreased to 11.8 +/- 25.3 ml/min/W above the AT (p = 0.0002). The decreased delta CO/delta WR above the AT primarily would be due to silent myocardial ischemia produced by exercise, as there was the presence of 201Tl redistribution in 15 of 16 patients in whom myocardial 201Tl scintigraphy with dipyridamole or exercise stress testing was evaluated. delta CO/delta VO2, which has been reported to be approximately 5.5 in normal subjects, was only 4.4 +/- 2.6 at work rates below the AT and was decreased to 1.1 +/- 2.3 at work rates above the AT. CONCLUSIONS: The relation between cardiac output and VO2 during exercise in patients with previous myocardial infarction differs profoundly from that reported in normal subjects. These findings must be considered when we noninvasively estimate the change in cardiac output during exercise by obtaining VO2 in patients with coronary artery disease.

Adult↗
PubMed1992

Development of a new investment for high-frequency induction soldering.

This study developed a new investment for induction soldering using high frequency induction heating. Ninety-five mass% magnesia clinker and 5 mass% dental stone were selected for the main constituents. The magnesia investment itself was scarcely affected by induction heating, so the addition of metal powders such as Fe, Ni, Co were investigated. Among these three powders, the addition of 10 mass% cobalt powder was most effective. This investment needed only 40 seconds of high frequency induction heating to go from room temperature to 900 degrees C without preheating. Thermal expansion of this investment in a vacuum atmosphere was 1.25% at 1000 degrees C. Dimensional changes during induction soldering were measured using German-silver and silver solder. When the new magnesia investment containing 10 mass% Co powder was used, the dimensional change was -0.2%. This contraction was less than when a magnesia investment without metal additives was used.

Cobalt↗
PubMed1992

Measurement of retinal nerve fiber layer thickness and its functional correlations with the visual field.

We have developed a technique for stereophotogrammetric measurements of retinal nerve fiber layer thickness at the disc margin. This technique has a reproducibility ranging from 3.9% to 6.0% in normal, ocular hypertensive and high pressure open angle glaucomatous eyes. The presence of a halo or scleral crescent had no effect on the reproducibility of the measurements. The measurements have shown that ocular hypertensive eyes have about an 18% decrease of retinal nerve fiber layer thickness compared to normals. High pressure open angle glaucomatous eyes have about a 43% decrease in retinal nerve fiber layer thickness compared to normals. This technique allows the development of maps of retinal nerve fiber layer thickness so that localized changes at the disc margin can be detected. The thinnest nerve fiber layer occurs primarily in the temporal segment. This technique has also correlated measurements of nerve fiber layer thickness with other measurements of the optic disc, particularly showing a significant correlation with area of pallor as well as measurements of the width of optic disc cup at about halfway between surface and the bottom of the cup. A significant correlation with visual field loss has been shown in high pressure open angle glaucomatous eyes, primarily with the temporal quadrant of the retinal nerve fiber layer and the nasal visual field. The rate of the visual field change in primary open angle glaucoma has been correlated with the initial nerve fiber layer thickness, with the greater the retinal nerve fiber layer thickness the greater the rate of the visual field loss during follow-up. These findings suggest that retinal nerve fiber layer thickness discriminates between normal, ocular hypertensive eyes as well as those with open angle glaucomas and may be useful in following patients with open angle glaucoma prior to development of the visual field loss.

Glaucoma, Open-Angle↗
PubMed1992

[Prosthetic valve function evaluated by ultrafast computed tomography (Imatron C-100)].

Ultrafast computed tomography (UFCT) is a new diagnostic modality that includes not only imaging of cardiac structures, but also movement of cardiac muscles and valves. It can be useful in the evaluation of prosthetic valves, because the scan time is extremely short and whole cardiac structures are imaged with a slice thickness of 8 mm and within 7 cardiac cycles. We review our experience using UFCT to observe prosthetic valve function in 22 cases with various valvular diseases.

Adult↗