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Biomedical subjects

S Yasui

Publications and source records attributed to S Yasui.

At least 73 records · Page 4Linked to original sources
PubMed1991

Simultaneous assessment of left ventricular wall motion and myocardial perfusion at rest and during exercise by technetium-99m methoxy isobutyl isonitrile.

First-pass radionuclide ventriculography followed by myocardial SPECT with technetium-99m methoxy isobutyl isonitrile (Tc-99m MIBI) was performed on 12 patients with suspected coronary artery disease at rest and during exercise. Left ventricular wall motion and myocardial perfusion were assessed simultaneously and compared on a segment-by-segment basis. Segmental agreement between Tc-99m MIBI and Tl-201 with regard to the presence of perfusion defects was 95% (57/60) at rest and 93% (37/40) during exercise. With respect to the assessment of myocardial ischemia and/or infarction, abnormalities in regional wall motion agreed with the presence of myocardial perfusion defects in 18 out of 21 segments (86%). Simultaneous evaluation of regional wall motion and myocardial perfusion by Tc-99m MIBI may provide useful information for the assessment of myocardial ischemia.

Adult↗
PubMed1991

The response of left ventricular regional function to afterload stress in patients with old myocardial infarction and ventricular aneurysm.

The functional response of the left ventricle with scar to increased afterload, was examined in 15 patients with old myocardial infarction and left ventricular aneurysm (OMI). Interventional cine left ventriculography during elevating left ventricular pressure with methoxamine. Wall motion was assessed by the radial and the centerline method. Augmented afterload didn't change ejection fraction in patients with OMI, but normalized wall motion (Z) increased in the aneurysmal region and decreased in the remote region in both methods. In the remote region in patients with OMI, afterload stress shortened left ventricular pressure-radial length (P-L) loops along length axis, and reduced percent systolic radial shortening (SS). In the aneurysmal region, P-L loops showed systolic elongation of length at rest and the slope of end-diastolic point to end-systolic point became steeper with increased afterload, resulting in a decrease of aneurysmal expansion. In summary, with increasing afterload, wall motion decreased in non-infarcted regions and increased in aneurysmal regions, in left ventricles with aneurysm. This mechanism may be interpreted as afterload-induced shifts of P-L loops in each region.

Adult↗
PubMed1991

Significant stenosis of coronary arteries in patients with single and multiple vessel diseases without previous myocardial infarction.

To determine what degree of stenosis should be counted as a significant lesion in each of 3 major coronary arteries in classification of the number of vessels involved, coronary arteriographic percent diameter narrowing (by quantitative angiography) was compared with thallium-201 scinitgraphic redistribution on treadmill exercise in 47 patients with evidence of exercise myocardial ischemia and greater than or equal to 50% diameter narrowing (visual assessment) in at least 1 major coronary artery. Severity of exercise-induced myocardial ischemia for the entire left ventricle (assessed by averaged redistribution index) was separated most sufficiently with definition of 63-64% or greater between patient groups with no- and single-, single- and double-, and double- and triple-vessel diseases. Collaterals and intraventricular contractile interaction are possibly the factors making definition more severe in extensive coronary artery disease. Since the visual method gives an overestimation of stenosis, it was concluded that vessel diameter narrowing of 70% or more should be regarded as significant in patients with single and multiple vessel diseases if the visual method is used.

Adult↗
PubMed1991

The relationship between chest pain during thallium-201 scintigraphy with dipyridamole and myocardial ischemia.

Dipyridamole thallium-201 scintigraphy (DP-Tl) and coronary angiography were studied on 74 patients with suspected coronary artery disease. We compared the clinical features, hemodynamic responses, angiographic results and scintigraphic findings of patients who had chest pain during DP-Tl testing ('chest pain' group) with those of patients who did not have chest pain ('no pain' group). Thirty eight (51%) of the 74 patients developed chest pain. Heart rate and rate pressure product during DP infusion of 'chest pain' group were greater than those of the 'no pain' group (p less than 0.05). Ischemic ST depression was more frequently observed among 'chest pain' patients (p less than 0.01). There were no differences in angiographic severity of coronary artery disease between 'chest pain' and 'no pain' group. Also, we could find no differences in extent and severity scores of perfusion defects and washout abnormalities between the two groups. However, when patients with myocardial infarction were excluded, the 'chest pain' group had significantly greater extent and severity scores of washout abnormalities than the 'no pain' group (extent score: 38 +/- 8 vs 18 +/- 5, p less than 0.05, severity score: 55 +/- 15 vs 18 +/- 7, p less than 0.01). Our study indicated that in patients without myocardial infarction, patients with 'chest pain' had more severe ischemia than 'no pain' patients. But in patients with myocardial infarction, myocardial ischemia not accompanied by chest pain might be as severe as that with chest pain. The presence or absence of myocardial infarction might have great influence on results regarding the relation of chest pain to myocardial ischemia.

Adult↗
PubMed1991

Signal-averaged body surface mapping for the assessment of low-amplitude potentials. Relation between ventricular depolarization and repolarization in normal subjects.

To examine the relation between ventricular depolarization and repolarization, body surface isopotential maps at the end of the QRS complex were studied in 32 normal subjects using a signal-averaged body surface mapping system. The number of beats averaged was 96-154 (mean 126.2). In this study, there were 8 types of isopotential map patterns at the end of the QRS complex. Mean +/- SD of QRS duration, appearance time of repolarization, and disappearance time of depolarization were 82.0 +/- 8.7 msec, 71.8 +/- 10.5 msec, and 79.7 +/- 9.4 msec, respectively. Time duration of overlapping depolarization and repolarization was 8.6 +/- 6.4 msec. The early repolarization was widely distributed on the left anterior chest and the upper sternal region. These results demonstrated the difference between the appearance time of repolarization and the disappearance time of depolarization for each lead. We concluded that it is difficult to evaluate ECG waves in the terminal portion of the QRS complex with the dipolar theory only.

Adolescent↗
PubMed1991

Relation between the incidence of arrhythmias and ischemic ST-segment depression during dipyridamole electrocardiography test in patients with coronary artery disease.

To examine the incidence of arrhythmias in dipyridamole infusion and the relation between dipyridamole-induced arrhythmias and ST-segment depression, dipyridamole electrocardiography tests were performed on 100 patients with coronary artery disease. Dipyridamole was infused at a rate of 0.568 mg/kg for 4 min, and 87-lead body surface mapping was performed to determine ischemic ST-segment depression. Positive ischemic response was defined as greater than or equal to 0.10 mV horizontal or downsloping ST-segment depression below the baseline, lasting 80 msec after the J point. Arrhythmias were observed by continuous electrocardiographic monitoring using a CM-5 lead electrocardiography. With respect to ventricular premature contractions (VPC), a group of patients with previous myocardial infarction (MI group) had a significantly higher incidence than a group of patients without previous myocardial infarction (non-MI group) before (16.7% vs. 1.7%, p less than 0.01) and after (38.1% vs. 3.4%, p less than 0.005) the dipyridamole infusion. The incidence of supraventricular premature contractions (SVPC), however, was not significantly different between the MI and non-MI groups. A group of patients with positive ischemic response had a significantly higher incidence of SVPC after the dipyridamole infusion than a group of patients with negative ischemic response (p less than 0.005). However, there was no significant difference in the incidence of VPC between the negative and positive ischemic response groups. These results suggest that dipyridamole-induced VPC is not always associated with ischemic ST-segment depression, but dipyridamole-induced SVPC is associated with dipyridamole-induced ischemic ST-segment depression in patients with coronary artery disease.

Adult↗
PubMed1990

Dopamine and 2-amino-4-phosphonobutyrate differentially modify spectral responses of H1 horizontal cells in carp retina.

Cone-driven external H1 horizontal cells (H1 HCs) in the cyprinid fish retina hyperpolarize in response to all visible lights, and their synaptic inputs have been widely believed to be excitatory. Recent experiments indicate, however, that short- and long-lambda (wavelength)-sensitive cone photoreceptors have different types of synaptic mechanisms; a conductance-decreasing, sign-reversing and short-lambda-mediating type, and a more conventional conductance-increasing class of excitatory (sign-conserving) synapse transmitting mainly long-lambda signals to H1 HCs. Here, a new set of evidence is presented for such spectrally segregated synaptic multiplicity, which also supports the notion that H1 HCs are actually color-opponent units where the depolarizing response component due to short-lambda-sensitive cones is normally overshadowed by the dominant hyperpolarizing component ascribed to long-lambda-mediating synaptic inputs. Application of dopamine to the retina preferentially enhanced the H1 HC responses to long-lambda flashes, and also depolarized the resting membrane potential in the dark. The spectral response was also examined after applying APB (2-amino-4-phosphonobutyric acid), in the presence of dopamine included to avoid polysynaptic effects of APB. This treatment enhanced the H1 HC responses to short-lambda stimuli and hyperpolarized the resting potential. These results are consistent with the suggestion that dopamine potentiates the conductance-increasing and long-lambda-mediating excitatory transmitter action, whereas APB acts as an agonist at the receptor involved in the conductance-decreasing and short-lambda-mediating transmitter action.

Aminobutyrates↗
PubMed1990

Segmental diastolic narrowing of epicardial coronary arteries in aortic regurgitation. Phase analysis by quantitative angiography of coronary artery diameter change during cardiac cycles.

A new finding of a segmental narrowing of the left anterior descending coronary artery in diastole (diastolic narrowing: DN) was reported. DN was found in 6 out of 45 patients (13.3%, 5 males, 1 female) with chronic aortic regurgitation (AR). It is likely that aortic regurgitation was more severe in terms of the history of heart failure, regurgitant fraction, left ventricular end-diastolic volume index and pressure, and aortic diastolic pressure in the patients with DN compared with those without DN. The phasic change of DN in cardiac cycles was analyzed by quantitative angiography, and indicated that DN commences at a point in mid-diastole when coronary vascular driving pressure (the instantaneous aortic and LV pressure difference) becomes abnormally reduced, reaches its maximum at end-diastole, and gradually recovers as aortic pressure increases during systole. In two patients, DN was no longer evident after valve replacement. We concluded that DN, a new coronary arteriographic finding, reflects the integrated severity of AR.

Angina Pectoris↗
PubMed1990

Clinical implications of exercise-induced chest pain: comparison of patients with and without pathologic Q waves in coronary artery disease.

We attempted to determine whether exercise-induced silent myocardial ischemia has different clinical implications in patients with and without pathologic Q waves. We studied 152 patients (121 men and 31 women) who had ischemic ST depression (greater than or equal to 0.05 mV) during exercise tests and greater than or equal to 70% narrowing in the three major coronary arteries. According to the presence or absence of chest pain during exercise, they were divided into symptomatic patients and asymptomatic patients: 104 patients without pathologic Q waves (Q(-) group) and 48 patients with pathologic Q waves (Q(+) group). In the Q(-) group, symptomatic patients (n = 56) had a significantly greater number of leads showing ST depression (p less than 0.0002), a greater maximum voltage of ST depression (p less than 0.005), a higher incidence of negative U waves (p less than 0.001), and a poorer blood pressure response (p less than 0.005) than asymptomatic patients (n = 48). However, in the Q(+) group, there were no significant differences between symptomatic (n = 24) and asymptomatic patients (n = 24) with regard to these parameters. We concluded that symptomatic patients without pathologic Q waves had more severe ischemia. On the other hand, in patients with pathologic Q waves, the severity of myocardial ischemia in asymptomatic patients might be equal to that in symptomatic patients. Chest pain during exercise testing is not a good predictor of myocardial ischemia in patients with pathologic Q waves. The presence or absence of pathologic Q waves is an important factor in the analysis of exercise-induced myocardial ischemia.

Chest Pain↗
PubMed1990

The clinical significance of exercise-induced ST segment changes in patients with previous inferior myocardial infarction.

To investigate the clinical significance of exercise-induced ST changes, we performed exercise body surface mapping (87 leads) in 52 patients (one-vessel disease [1 VD] n = 12, multivessel disease [MVD] n = 40) with previous inferior myocardial infarction (MI). ST isointegral maps were constructed and the locations of ST changes were compared with the findings of exercise thallium-201 (TI-201) myocardial scanning. Exercise-induced ST elevation was observed in 14 patients (27%) on the lower chest and on the back, corresponding to the infarcted area. Exercise-induced ST depression was observed more frequently in the MVD group (n = 30, 75%) than in the 1VD group (n = 2, 17%). Seventeen (77%) of 22 patients with ST depression had thallium-201 redistribution. There was a significant association between ST depression and TI-201 redistribution (chi2 = 13.1, p less than 0.001), but no association between ST depression and ST elevation. The body surface distribution of ST depression was shifted upward and rightward compared with its appearance in angina pectoris without MI. These findings suggest that exercise-induced ST depression reflects myocardial ischemia in patients with previous inferior MI.

Adult↗
PubMed1990

Measurements of the isometric contractile forces generated by dog periodontal ligament fibroblasts in vitro.

One hypothesis for the mechanism of tooth eruption is that the periodontal ligament fibroblasts generate the eruptive force. To assess the force generated, these fibroblasts were obtained by explant culture of ligament from mandibular premolars of a dog and were cultured in collagen gel matrices. The forces generated by them under isometric conditions were continuously measured for 120 h with a strain gauge. At the same time the number of cells in the gel was counted and the force measured was calculated as the force generated by 10(4) cells. Shortly after the start of culture, the force per 10(4) cells increased rapidly; it reached 5.2 X 10(-4) N at 8 h, and then remained at the same level for about 48 h. Our findings suggest that fibroblasts of the periodontal ligament may generate sufficient force for tooth eruption.

Animals↗
PubMed1990

Abnormalities of early depolarization in patients with remote anterior myocardial infarction and ventricular septal hypoperfusion. Diagnosis of septal MI by BSM.

The authors conducted this study to find the difference in body surface isopotential maps in 46 patients with previous anterior infarction with and without septal involvement. Thallium-201 myocardial-perfusion imaging identified 25 patients with septal infarction (group P) and 21 without (group N). In contrast to group N, group P had a prominent minimum on the anterior chest during the early phases of the QRS. According to the results obtained, the following criteria for identifying patients with septal infarction (group P) were proposed (1). Criterion 1: The absolute value of the voltage of the minimum is equal to or greater than that of the maximum at 5 ms after the onset of the QRS; (2) Criterion 2: During the early portion of the QRS the voltage of the minimum reaches -0.10 mV at the same time or earlier than the maximum reaches 0.10 mV. Both criteria had higher sensitivities (100% and 100%), specificities (71.4% and 90.5%), and predictive accuracies (87.0% and 95.7%) than either Franklead vectorcardiograms or standard 12-lead electrocardiograms in the study population. Thus, body surface isopotential mapping is considered to be useful for the diagnosis of septal involvement in patients with previous anterior myocardial infarction.

Algorithms↗
PubMed1990

Use of body surface electrocardiographic mapping to localize the asynergic site in previous myocardial infarction.

Body surface electrocardiographic (ECG) maps of myocardial infarction were analyzed using the departure mapping technique, which represents the abnormal potential distribution out of normal ranges. Body surface ECG mapping using 87 leads was performed on 65 patients with previous myocardial infarction and on 40 normal volunteers. Potential departure maps at 10, 20, 30, 40, and 50 msec after the onset of QRS were constructed; each map indicated, if present, the area of abnormal decreased potential that is more than 2 standard deviations from the normal range (-2 SD area). In patients with myocardial infarction, the appearance time and the location of the -2 SD area were specific for the sites of left ventricular asynergy; the sensitivity and specificity were 86% and 100% for the asynergy of segment 2 (20 msec, on the upper left anterior chest), 87% and 97% for segment 3 (30 msec, on the middle anterior chest), 86% and 80% for segment 4 (20 or 30 msec, on the lower right anterior chest), and 88% and 90% for segment 5 (30, 40, or 50 msec, on the middle back), respectively. The sensitivity of these criteria was better than that of 12-lead ECG, while the specificity was comparable. In the analysis of body surface ECG mapping data, departure maps aid in depicting abnormalities and in making an accurate assessment. Body surface ECG mapping can be used to improve the diagnostic ability of ECG to detect myocardial infarction.

Adult↗
PubMed1990

Relation between localization of coronary artery disease and local abnormalities in ventricular activation during exercise tests.

To examine whether or not the location of local abnormalities on body surface isochrone maps reflects the site of myocardial ischemia, 48 coronary artery disease patients without myocardial infarction were studied. Eighty-seven unipolar electrocardiograms distributed over the anterior chest and the back were recorded simultaneously before and after the submaximal treadmill exercise. For each lead, the duration from the QRS onset to the time of the most rapid decrease in QRS voltage was measured (index of ventricular activation [IVA]). Based o the data provided by these 87 leads, IVA isochrone maps (IVA map) in preexercise and in postexercise, as well as IVA maps showing the difference between preexercise and postexercise, were constructed. The IVA was defined as abnormal when it exceeded (mean + 2 SD) the normal range. We called the area with the abnormal IVA, the "+2SD area." In patients having a stenosis in the left anterior descending artery, the +2SD area in each map was located mainly on the left anterior chest, whereas in patients having a stenosis in the right coronary artery, the +2SD area in each map was located mainly on the right lower thoracic surface. Moreover, the +2SD area of patients with both left anterior descending and right coronary artery disease appeared on both the left anterior chest and the right lower thoracic surface. In patients with left circumflex artery disease, however, the location of the +2SD area did not suggest a stenotic site because of its small population. On the other hand, it was difficult to determine the ischemic site from the body surface distribution of ST segment depression.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1990

Body surface mapping of high-frequency components in the terminal portion during QRS complex for the prediction of ventricular tachycardia in patients with previous myocardial infarction.

To study the clinical significance of terminal QRS high-frequency components for the prediction of ventricular tachycardia, an 87-lead body surface signal-averaged mapping was performed in 21 healthy subjects (control) and in 41 patients with previous myocardial infarction (anterior, 20; inferior, 21). Mapping data were analyzed and averaged (129.7 +/- 26.5 beats) for 160 seconds, and the signal-averaged beat was filtered with a bidirectional bandwidth (80-250 Hz) digital filter. J-point was determined from the 87-lead RMS voltage of nonfiltered QRS. For each lead, we calculated the sum of the absolute value of filtered QRS from 20 msec ahead of the J-point to the J-point (A-20). The body surface distribution of A-20 was expressed as A-20 map. The maxima in A-20 maps were mainly located on the upper sternal region in healthy subjects, on the left anterior chest in patients with previous anterior myocardial infarction, and on the central anterior chest in patients with previous inferior myocardial infarction. In the patients in both the group with anterior myocardial infarction and the group with inferior myocardial infarction, the value of maximum was significantly greater than in the subjects in the control group (0.181 +/- 0.086 and 0.138 +/- 0.048, respectively, vs. 0.075 +/- 0.031 mV.msec; p less than 0.01). In patients with myocardial infarction (n = 41), the value of maximum was significantly greater with ventricular tachycardia (n = 11) than without ventricular tachycardia (n = 30) (0.240 +/- 0.076 vs. 0.130 +/- 0.043 mV.msec; p less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗