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Biomedical subjects

K Kiyonaga

Publications and source records attributed to K Kiyonaga.

17 recordsLinked to original sources
PubMed2000

Plasma level of triglyceride-rich lipoprotein remnants is closely associated with the activation of coagulation factor VII in patients with myocardial infarction.

Remnant-like particles, which have been recognized to be atherogenic derivatives of chylomicrons and very low density lipoproteins, can be measured using a new assay kit. The purpose of the present study was to investigate the association of remnant-like particles with the coagulation system that has an important role in the pathogenesis of myocardial infarction. We assayed blood levels of total cholesterol, triglyceride, HDL-cholesterol, apolipoproteins, remnant-like particles-cholesterol, remnant-like particles-triglyceride, fibrinogen, factor VII antigen, activated factor VII, and tissue factor in 111 patients with a history of myocardial infarction and 128 control subjects. In simple regression analysis, plasma levels of remnant-like particles-cholesterol and remnant-like particles-triglyceride showed a significant positive correlation with the levels of activated factor VII (r=0.319, p<0. 001, and r=0.286, p=0.002, respectively) and the activated factor VII/factor VII antigen ratio (r=0.241, p=0.011, and r=0.249, p=0.008, respectively) in patients with myocardial infarction. In contrast, there were no significant differences between remnant-like particles and activated factor VII in control subjects. In stepwise multivariate regression analysis, the significant determinants of activated factor VII were remnant-like particles-cholesterol (10.2%), apolipoproteins A-I (5.1%), and E (7.1%); for the activated factor VII/factor VII antigen ratio, remnant-like particles-triglyceride (6. 2%), age at blood sampling (5.1%), and apolipoprotein A-I (4.0%) in patients with myocardial infarction. However, the significant determinants of activated factor VII and the activated factor VII/factor VII antigen ratio were HDL-cholesterol (9.9% and 9.2%, respectively) in control subjects. It is concluded that remnant-like particles may be a risk factor for myocardial infarction by activating the extrinsic coagulation pathway.

Adult↗
PubMed1999

Morphological effects on in-stent restenosis assessed by intravascular ultrasound imaging.

The purpose of this study was to evaluate the rupture and dissection of the vessel wall immediately after balloon dilatation by intravascular ultrasound (IVUS) imaging and to predict restenosis in patients who underwent subsequent coronary stent implantation. Stent implantation improves the long-term results of coronary angioplasty by reducing lesion elastic recoil and arterial remodeling. However, several studies have suggested that neointimal hyperplasia is the cause of instant restenosis. We recruited 60 patients in whom IVUS studies were performed immediately after successful balloon dilatation and just before stent implantation. We compared IVUS parameters with 6-month follow-up quantitative coronary angiography. This was performed in 51 lesions of 51 patients (85%). Qualitative analysis included assessment of plaque composition, plaque eccentricity, plaque fracture and the presence of dissection. In addition, minimal luminal diameter, percent diameter stenosis, percent area stenosis and plaque burden were quantitatively analyzed. Two morphological patterns after balloon dilatation were classified by IVUS. Type I was defined as absence or partial tear of the plaque without disclosure of the media to lumen (22 lesions). Type II was defined as a split in the plaque or dissection of the vessel wall with disclosure of the media to the lumen (29 lesions). At 6 months follow-up, angiographic restenosis occurred in 17 of the 51 lesions (33%). Restenosis was significantly (p < 0.05) more likely to occur in type II (13/29: 45% incidence) than in type I (4/22: 18% incidence). The assessment of plaque morphology immediately after balloon dilatation and before stent implantation provides important therapeutic and prognostic implications.

Aged↗
PubMed1994

Early assessment of reperfusion therapy using cardiac troponin T.

OBJECTIVES: The purpose of this study was to investigate the utility of cardiac troponin T for early assessment of reperfusion therapy. BACKGROUND: Several biochemical markers are used for early noninvasive detection of reperfusion during intravenous thrombolytic therapy. However, cardiac troponin T, a new myocardial-specific marker, has not been used previously for this purpose. METHODS: We measured troponin T and creatine kinase, MB isoenzyme (CK-MB) levels in 38 patients with acute myocardial infarction whose infarct-related artery was totally occluded before reperfusion therapy. Subjects comprised 14 patients with successful angioplasty (group 1), 12 patients with successful thrombolytic therapy (group 2) and 12 patients with unsuccessful attempted reperfusion (group 3). Blood samples were taken every 15 min, and coronary angiography was performed every 5 to 8 min until 60 min after reperfusion (groups 1 and 2) or after the initiation of treatment (group 3). We calculated the increase in troponin T (delta troponin T) and CK-MB (delta CK-MB) 60 min after treatment was initiated and 60 min after reperfusion in groups 1 and 2. RESULTS: Mean (+/- SD) delta troponin T and delta CK-MB levels were 9.35 +/- 7.83 ng/ml and 125 +/- 83 mU/ml in group 1 and 3.23 +/- 3.08 ng/ml and 130 +/- 137 mU/ml in group 2, respectively, 60 min after treatment and were 10.1 +/- 8.35 ng/ml and 131 +/- 84 mU/ml in group 1 and 6.84 +/- 8.30 ng/ml and 158 +/- 146 mU/ml in group 2, respectively, 60 min after reperfusion. These values were significantly higher than those 60 min after treatment in group 3: 0.16 +/- 0.19 ng/ml and 10 +/- 9 mU/ml, respectively. The predictive accuracy for detecting reperfusion using a threshold value of 0.50 ng/ml of delta troponin T and 25 mU/ml of delta CK-MB was 100% in group 1 and 92% in group 2 60 min after treatment, respectively. There was significant correlation between delta troponin T and delta CK-MB. CONCLUSIONS: Serial measurements of cardiac troponin T as well as of CK-MB are useful for early assessment of reperfusion therapy.

Aged↗
PubMed1990

Clinical value of magnetic resonance imaging for cervical myelopathy.

The magnetic resonance imaging (MRI) findings in 115 cases of cervical myelopathy, 121 cases of cervical radiculopathy, and 64 cases of neck pain with no neurologic deficit were prospectively studied to investigate the clinical value of MRI for cervical myelopathy. The MRI findings in the T1-weighted sagittal projection were classified into four groups according to the degree of the compressed deformities of the cervical cord. The degree of compression of the cervical cord on MRI findings showed a significant correlation with the severity of myelopathy, the anteroposterior diameter of the spinal column, and the degree of compression of the dural tube in the myelograms (P less than 0.01). Fifty-one patients of cervical myelopathy had undergone both preoperative and postoperative MRI. Of these, the spinal canal of 47 patients that was well decompressed was recognized according to plain computed tomography (CT). However, 24 (51%) of these 47 patients showed on MRI a deformity in the spinal cord amounting to cord atrophy. The correlation between the clinical function of the spinal cord and the recovery of the cord deformity on MRI at the operative levels was accurately investigated in 34 patients who had no cord deformities in the adjacent intervertebral levels. Twenty patients with cord atrophy had slightly poor clinical results, although no significant difference was found between these 20 and 14 patients with recovery in the cord deformities. From these results, it was evident that T1-weighted MRI is useful in the accurate diagnosis of compression myelopathy, in accurately deciding the level of the disease focus, and in the accurate assessment of the surgical results.

Cervical Vertebrae↗
PubMed1987

Influences of localized aortic valve damage on coronary artery blood flow in acute aortic regurgitation: an experimental study.

We examined the influences of localized aortic valve damage on coronary artery blood flow and the prognosis in acute aortic regurgitation. Aortic regurgitation was produced in 18 open-chest dogs by extensively cutting one of the three aortic cusps with a nerve knife introduced via the cardiac apex. The dogs were separated into three groups of six dogs each. In each group the noncoronary cusp (NCC), the right coronary cusp (RCC), or the left coronary cusp (LCC) was cut. Aortic and left ventricular pressures; the phasic aortic, left anterior descending (LAD), and right coronary artery (RCA) blood flows; and electrocardiograms were simultaneously recorded before and after production of acute AR. All dogs in the NCC and RCC groups survived for at least 30 to 60 min, but all dogs in the LCC group died after 5 to 9 min of production of acute AR due to left ventricular failure. After 2 min of aortic regurgitation, the total, systolic, and diastolic LAD flows were 39 +/- 14, 19 +/- 9, and 20 +/- 8 ml/min (mean +/- SD) in the NCC group, 41 +/- 15, 31 +/- 9, and 10 +/- 6 ml/min in the RCC group, and 9 +/- 5, 19 +/- 5, and -10 +/- 2 ml/min in the LCC group, respectively. The corresponding RCA flows were 19 +/- 9, 15 +/- 6, and 4 +/- 3 ml/min in the NCC group, 13 +/- 8, 21 +/- 12, and -8 +/- 4 ml/min in the RCC group, and 14 +/- 4, 19 +/- 4, and -5 +/- 1 ml/min in the LCC group, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Acute Disease↗
PubMed1985

[Mechanism of systolic anterior motion of the mitral valve in dogs].

The mechanism of systolic anterior motion (SAM) of the mitral valve remains somewhat controversial. We previously reported that SAM can be produced in dogs using dobutamine infusion. In the present study, dobutamine infusion, dextran infusion and venesection were performed in 13 anesthetized closed-chest dogs to study the mechanism of SAM. The degree of SAM was determined by M-mode echocardiography. End-systolic and end-diastolic short-axis areas of the left ventricle at the level of the chordae tendineae and the fractional area changes were measured by two-dimensional echocardiography. SAM was produced in six of the 13 dogs during dobutamine infusions (Group 1), but not in the other seven dogs (Group 2). During dobutamine infusions, % fractional area changes were greater in Group 1 (85 +/- 5; mean +/- standard deviation) than in Group 2 (65 +/- 15) (p less than 0.01), and the end-systolic short-axis area of the left ventricle was smaller in Group 1 (0.7 +/- 0.4 cm2) than in Group 2 (1.9 +/- 0.3 cm2) (p less than 0.01), although no significant change was observed between Groups 1 and 2 in the end-diastolic short-axis area of the left ventricle. Subsequent injections of dextran (mean 340 ml) in Group 1, decreased the degree of SAM and increased the end-diastolic and end-systolic short-axis areas of the left ventricle. Subsequently, venesections (mean 400 ml) in Group 1 resulted in increases in the degrees of SAM and decreases in the end-diastolic and end-systolic short-axis areas of the left ventricle.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1984

[Detection of a shunt flow through a defect in secundum atrial septal defect by right parasternal approach using pulsed Doppler echocardiography].

Pulsed Doppler echocardiography combined with two-dimensional echocardiographic (2-DE) system was performed to detect a shunt flow through a defect in the interatrial septum (IAS) in patients with secundum atrial septal defect (ASD) utilizing right parasternal approach (RPA). RPA is a method which provides an accurate evaluation of a defect in the IAS on a 2-DE image by placing a transducer on the right of the sternum because the ultrasonic beam passes in a plane almost perpendicular to the IAS. The subjects consisted of 20 patients with ASD (25 +/- 22 yrs) diagnosed by cardiac catheterization or 2-DE with peripheral contrast material injection, and 10 cases of healthy subjects (34 +/- 18 yrs). Defects in the IAS were clearly visible in 19 patients with ASD on 2-DE images by RPA. By placing the sample volume in the center of the defect, Doppler flows could be obtained in 17 of them. In 13 with sinus rhythm, except a case of Eisenmenger syndrome, Doppler signals showed mainly a laminar flow toward the transducer (positive flow), but a transient flow of low velocity away from the transducer (negative flow) was also observed. The positive flow had its peaks in late systole and atrial systole and occasionally in mid-systole, early diastole and mid-diastole. The negative flow occurred in early systole, mid-diastole and late diastole. In a patient with Eisenmenger syndrome and tricuspid regurgitation (TR), a negative turbulent flow was observed from early systole to mid-diastole. In three patients with atrial fibrillation, Doppler signals were variable. The Doppler echogram of a patient with atrial fibrillation but no complication showed a laminar positive flow with its peaks in late systole and mid-diastole, and a negative flow in early systole. One patient with atrial fibrillation and TR had a systolic negative turbulent flow and a mid-diastolic laminar positive flow. In a patient with TR and mitral regurgitation, the Doppler echocardiogram showed a laminar positive flow throughout the entire cardiac cycle with its peaks in early diastole and mid-diastole. Doppler signals from the left atrium (LA) to the right atrium (RA) through a defect coincided in timing with the appearance of negative contrast echo from the defect to the RA on 2-DE image and signals from the RA to the LA coincided with the appearance of the contrast echo into the LA from the RA through the defect. Doppler signals disappeared after the closure of the defect in all six patients examined.(ABSTRACT TRUNCATED AT 400 WORDS)

Adolescent↗
PubMed1984

[An experimental study on the relationship between interventricular septal echograms and interventricular pressure gradient].

To evaluate the correlation between the configuration and motion of the interventricular septum (IVS) and the interventricular pressure gradient, six closed-chest dogs were studied. M-mode and two-dimensional echograms, the left (LVP) and right ventricular pressures (RVP), the interventricular pressure gradient (LVP-RVP), phonocardiograms in the left and right ventricles and electrocardiograms were simultaneously recorded. The RVP was gradually elevated by injecting Lycopodium in a peripheral vein. In all six dogs, there were good correlations between the curvature of the IVS and the interventricular pressure gradient in end-systole and in end-diastole. In M-mode echograms of the IVS, three dips were recognized in early diastole (isovolumetric relaxation period, D1 dip), in late diastole (atrial kick, D2 dip) and in early systole (isovolumetric contraction, S1 dip) when the RVP was elevated. Three negative dips on interventricular pressure gradient curves were observed to occur simultaneously with D1, D2, and S1 dips, respectively. A D1 dip was demonstrated in all six dogs, a D2 dip in four dogs, and an S1 dip in six dogs. In conclusion, the curvature of the IVS reflects the change in the interventricular pressure gradients in diastole as well as in systole. D1, D2 and S1 dips in the IVS echogram also reflect changes in the interventricular pressure gradients.

Animals↗
PubMed1982

The effect of digoxin on cardiovascular responses to hypoxia and reoxygenation in anesthetized dogs.

To clarify the efficacy of digitalis in acute hypoxia and reoxygenation, we estimated the effects of digoxin on cardiovascular hemodynamics in anesthetized dogs. Hypoxia caused significant increases in aortic pressure, pulmonary artery pressure, left ventricular (LV) pressure, rate of change in LV pressure (LVdp/dt), cardiac output (CO) and plasma catecholamines. These changes in LVdp/dt, CO and plasma catecholamines induced by hypoxia were returned to the control levels within 3 min by reoxygenation with 70% O2. The injection of digoxin (0.05 mg/kg) in hypoxic dogs resulted in significant increases in LVdp/dt, CO and stroke volume (SV) but no changes in levels of plasma catecholamines, heart rate, mean aortic pressure and mean pulmonary artery pressure. However, the injection of digoxin resulted in no significant changes in cardiovascular response to reoxygenation. Our experiments demonstrate that digoxin caused significant increases in CO, SV and LVdp/dt in dogs with hypoxia but resulted in no significant changes in cardiovascular responses to reoxygenation.

Anesthesia↗
PubMed1981

Effects of hypoxia on myocardial digoxin uptake and levels of plasma catecholamines in anaesthetised dogs.

The effect of hypoxia on digoxin pharmacokinetics, myocardial digoxin uptake and levels of plasma catecholamines in dogs was studied to clarify the mechanism of enhanced sensitivity to digitalis in hypoxia. Sixteen mongrel dogs were anaesthetised and artificially respired; eight with room air, eight with 8% oxygen in nitrogen, and digoxin (0.05 mg . kg-1) was intravenously given to each dog. There was no difference between hypoxic and non-hypoxic dogs in pharmacokinetic curves of digoxin. The level of myocardial digoxin in hypoxic dogs was significantly lower than that in non-hypoxic dogs. The level of plasma adrenaline in hypoxic dogs was significantly higher than that in non-hypoxic dogs (P less than 0.01). These data suggest that enhanced sensitivity to digoxin in hypoxia may be attributable not to abnormal digoxin pharmacokinetics or increased myocardial digoxin uptake but partly to higher levels of plasma catecholamines.

Animals↗