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Biomedical subjects

M Oguma

Publications and source records attributed to M Oguma.

18 recordsLinked to original sources
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↗
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↗
PubMed1989

Effect of diltiazem on coronary blood flow distribution in dog heart under ischemia.

Effect of intracoronary infusion of diltiazem (1 microgram/min) on regional myocardial blood flow (RMBF) was studied using 15-microns radioactive microspheres in 11 excised cross-circulated canine left ventricles. With total coronary blood flow (CBF) and heart rate (HR) held constant, regional ischemia was induced by ligating the left anterior descending coronary artery (LAD). Diltiazem at the dose used had no effects on ventricular Emax before and after LAD ligation. RMBF expressed by the counts divided by the counts averaged in all segments in each layer significantly (p less than 0.05) increased under diltiazem only in the low-flow region that had less than 50% RMBF before diltiazem; from 21% (+/- 12%) to 35% (+/- 18%) in the epicardial, from 22% (+/- 12%) to 32% (+/- 18%) in the midwall, and from 24% (+/- 10%) to 31% (+/- 12%) in the endocardial layers. We conclude that the beneficial effect of diltiazem on the ischemic heart involves a direct action on the coronary vascular system and does not necessarily depend on the concomitant changes in hemodynamics.

Animals↗
PubMed1987

[Predictability of stress-induced myocardial ischemia from coronary arteriography in patients with organic coronary artery stenosis].

A quantitative index for describing the severity and extent of coronary artery disease has not been established yet, although it is certain that the stenosis causes myocardial ischemia induced by stress. To establish the most meaningful scoring system, we developed the grading of stenosis which is "critical" or significant in the single-, double-, and triple-vessel method (SDT), and the extent of improvement in the predictive value which may be induced by accounting for the predominance of the three major coronary arteries nourishing the left ventricle. Thirty-three patients (six were women), whose average age was 58.6 years, all having exertional angina pectoris and fixed organic coronary artery stenosis documented by coronary arteriography, but no old myocardial infarction, were the subjects of this study. For these patients the mean redistribution index (RDI) was determined by ergometer stress myocardial perfusion imaging using 201T1. The number (nST) of significant ST segment depressions by body surface ECG mapping after treadmill stress tests was compared with the sigma Pujadas grade, which is the sum of each grade assigned to each of the three major coronary arteries, and with the Pujadas score, which is the weighted sum of grades by dominance in the coronary artery distribution. The SDT method was a better predictor of ischemia if the criterion for critical stenosis is selected at a more severe stenosis (greater than 90% diameter stenosis). Among factors predicting ischemia, the length of the stenosis and the presence of collaterals did not seem to be definitive. However, the distribution of the arteries was an important factor.(ABSTRACT TRUNCATED AT 250 WORDS)

Coronary Angiography↗
PubMed1986

[Severity and extent of coronary artery disease and their relationship to left ventricular functional reserve in the chronic disease state].

Our previous observations showed that left ventricular wall motion abnormality (asynergy) induced by stress was observed in the phase response of radionuclide technique, and the severity and extent of coronary artery disease (CAD) assessed by the Pujadas score (PS) correlated well with the maximal phase delay response (delta MPD) but not with the ejection fraction response (delta EF) in patients with CAD without old myocardial infarction (MI). This study evaluated the usefulness of EF, MPD and the first-third filling fraction (FF, divided by the volume accrued throughout diastole) at rest and during stress, using ergometer and first-pass radionuclide angiocardiography (RNA), to determine the severity of CAD, and to evaluate any abnormalities in the systolic and diastolic coupling in left ventricular function during stress. Seventy-four patients with significant CAD, including 41 with previous transmural MI (MI group) and 33 without MI (angina group) were the subjects of this study. EF at rest and during stress inversely correlated, and MPD on stress linearly correlated with PS in angina group with PS greater than 10, while no such correlations were found in MI group. A normal EF response (delta EF greater than or equal to 5%) was accompanied by a greater-than-normal response in FF (delta FF) in both groups. A lower EF response was accompanied by a smaller delta FF in angina group, but by a larger delta FF in MI group. The difference was statistically significant (p less than 0.03), without significant differences by age, PS, peak heart rate, systolic blood pressure, and ischemia on ECG during stress. Resting EF and FF by the RNA method correlated with those by left ventriculography (LVG), respectively. It was suggested that RNA is an accurate method for determining EF and FF, while phase analysis may provide some additional information different from that provided by LVG. We concluded that EF and MPD during stress are as useful as delta MPD with the exception of a few cases in predicting the severity of CAD, and that scar tissue within the ventricular wall in MI may play an important role in determining the ventricular diastolic mechanical property during stress.

Angina Pectoris↗
PubMed1985

Hyperkinetic contraction of a nonischemic segment of ischemic left ventricle in anesthetized dogs.

Regional myocardial function during acute coronary artery occlusion was studied with ultrasonic dimension gauges in 20 open-chest anesthetized dogs. Two pairs of ultrasonic crystals were implanted in the left ventricular free wall near the epicardium in an ischemic segment and in a control nonischemic segment, and the segment length (SL) and maximum velocity of systolic shortening (max dL/dt) were measured. In six dogs, the wall thickness (WT) was measured simultaneously in the same regions with sonomicrometry. Left ventricular pressure (LVP), aortic pressure (AoP), and plasma norepinephrine concentration in the coronary sinus (NECS) were also measured. The heart rate was kept constant (180 beats/min) with atrial pacing. The left anterior descending coronary artery was occluded at its distal portion without propranolol in 12 dogs (group 1) and 30 min after propranolol in eight dogs (group 2). In the ischemic region, coronary artery occlusion resulted in an increase in end-diastolic SL (50% at 3 min after occlusion in group 1, P less than 0.005), and a decrease in max dL/dt in systole (36% at 5 min after occlusion in group 1, P less than 0.02). In the nonischemic region, end-diastolic SL did not change significantly, but an increase in max dL/dt (29% at 10 min after occlusion in group 1, P less than 0.005) was observed in systole. Under propranolol (group 2), the results were similar to those of group 1. There were no significant changes in LVP, AoP, AoP, and NECS during occlusion.(ABSTRACT TRUNCATED AT 250 WORDS)

Anesthesia, Intravenous↗
PubMed1985

[Functional reserve of the ischemic left ventricle with ventricular aneurysm to afterload stress: digital subtraction angiographic assessments].

Digital subtraction angiography (DSA) has been confirmed to be an accurate method for determining left ventricular function. It is a relatively non-invasive technique without inducing premature ventricular complexes. The response of left ventricular function to afterload stress was assessed using DSA for eight patients with old anterior myocardial infarction and ventricular aneurysm including that of the anterior wall (averaging 30.3 months after the acute episodes). Their ages ranged from 36 to 65 years and one patient was a woman. Prior to the investigation, we confirmed that a single DSA procedure did not alter left ventricular function in a pilot study of one patient (No. 8). After initial DSA in the basal state, methoxamine was infused intravenously (1 to 2 mg/min). When aortic systolic blood pressure increased by 30 to 50 mmHg, a second DSA was performed for each patient. Left ventricular volumes and ejection fractions were calculated by the area-length method, and regional wall motion was assessed by the visual method according to the AHA classification and the curvature radius of the apical ventricular aneurysm was calculated. Methoxamine induced neither acute heart failure nor angina pectoris in the present series. The heart rates decreased, and there were a significant increase in end-systolic volumes (p less than 0.05), end-systolic radii (p less than 0.05), and a significant decrease in ejection fractions (p less than 0.02) after methoxamine infusion. In 32 of 40 segments, regional wall motion was unchanged by methoxamine as assessed by the visual method; whereas, in the other eight, there was a deterioration.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1982

[Central hypotensive effects of guanfacine in anaesthetised rabbits (author's transl)].

The effects of intracerebroventricular (i.c.v.) injection of guanfacine, a new antihypertensive agent, on blood pressure and heart rate were investigated and compared with those of clonidine in anaesthetized rabbits. The i.c.v. injection of guanfacine or clonidine induced a decrease in blood pressure and heart rate in doses which were ineffective by an intravenous route. The depressive effect of guanfacine was less than that of clonidine, but the duration of this action was obviously longer than that of clonidine. A fall in heart rate caused by guanfacine was always less conspicuous than that by clonidine in equipotent hypertensive doses. Decrease in blood pressure and heart rate caused by the two drugs were inhibited by i.c.v. pretreatment with phentolamine and 6-hydroxydopamine, respectively. These findings suggest that presynaptic and/or postsynaptic alpha-adrenoceptors in the brain may play an important role in the hypotension and bradycardia produced by guanfacine as well as clonidine. Furthermore, the uptake mechanism at the presynaptic sites of central noradrenergic neurons may be involved in the mode of hypotensive and bradycardic actions of these two drugs since these effects were abolished by pretreatment with desipramine, an inhibitor of noradrenaline uptake into the presynaptic nerve terminals.

Animals↗
PubMed1982

The beneficial effect of diltiazem on exercise-induced ST depression, measured by body surface mapping, in stable effort angina pectoris.

The effect of diltiazem, a calcium antagonist, was examined in eight male patients with stable effort angina pectoris by means of multistage treadmill testing using body surface mapping. The area and severity of exercise-induced ST depression after 90 mg of diltiazem administered orally three hours before exercise were compared with those without diltiazem. Although the same workload was performed, the area and severity of exercise-induced ST depression were significantly diminished (P less than 0.005) after diltiazem. The reproducibility of these observations was confirmed in two of the eight patients studied and in three other patients. Because exercise-induced ST depression in patients with coronary artery disease is generally believed to reflect myocardial ischemia, our results provide objective evidence that diltiazem is able to reduce the exercise-induced myocardial ischemia in effort angina pectoris.

Aged↗