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Kiyoshi Yoshida

Publications and source records attributed to Kiyoshi Yoshida.

At least 19 recordsLinked to original sources
PubMed2006

Effects of angiotensin II on NO bioavailability evaluated using a catheter-type NO sensor.

We investigated the acute or chronic effects of angiotensin (Ang) II on the bioavailability of NO in Ang II-infused rabbits using the catheter-type NO sensor. Male New Zealand White rabbits were infused with vehicle (sham), Ang II at a rate of 200 ng/kg per minute, either alone or in combination with hydralazine, Ang II type I receptor antagonist (valsartan), or an antioxidant (tempol) for 24 hours or 14 days. Plasma NO concentration was measured using the catheter-type NO sensor located in the aorta. We then infused saline (vehicle) and acetylcholine (ACh) into the aortic arch with or without pretreatment with N(G)-methyl-l-arginine. An increase in plasma NO levels in response to ACh was significantly attenuated in the Ang II group compared wit the control group. The decrease in the basal plasma NO concentration was significantly lower in the Ang II group than in the control group. Plasma peroxynitrite concentrations in Ang II group were significantly higher than in the control group. The negative effects of Ang II, that is, the decrease in basal and ACh-induced NO production and the increase in oxidative stress, were significantly suppressed by the cotreatment with either valsartan or tempol. Short-term treatment with Ang II significantly increased the ACh-induced increase in plasma NO concentration, as well as basal NO release. Although Ang II stimulates release of NO in the short term, chronic treatment with Ang II elicits the decreased NO bioavailability in the aorta of the Ang II-infusion rabbit model.

Angiotensin II↗
PubMed2006

Assessment of coronary arterial thrombus by optical coherence tomography.

We analyzed optical coherence tomographic (OCT) characteristics of different types of coronary thrombi that had been confirmed at postmortem histologic examination. We examined 108 coronary arterial segments of 40 consecutive human cadavers. OCT images of red and white thrombi were obtained and the intensity property of these thrombi was analyzed. Red and white thrombi were found in 16 (17%) and 19 (18%) of the 108 arterial segments, respectively. Red thrombi were identified as high-backscattering protrusions inside the lumen of the artery, with signal-free shadowing in the OCT image. White thrombi were identified as low-backscattering projections in the OCT image. There were no significant differences in peak intensity of OCT signal between red and white thrombi (130+/-18 vs 145+/-34, p=0.12). However, the 1/2 attenuation width of the signal intensity curve, which was defined as the distance from peak intensity to its 1/2 intensity, was significantly different between red and white thrombi (324+/-50 vs 183+/- 42 microm, p<0.0001). A cut-off value of 250 microm in the 1/2 width of signal intensity attenuation can differentiate white from red thrombi with a sensitivity of 90% and specificity of 88%. We present the first detailed description of the characteristics of different types of coronary thrombi in OCT images. Optical coherence tomography may allow us not only to estimate plaque morphology but also to distinguish red from white thrombi.

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PubMed2006

Assessment of coronary arterial plaque by optical coherence tomography.

The purpose of this study was to analyze the ability of optical coherence tomography (OCT) to identify coronary arterial plaque diagnosed by histologic examination. We examined 166 sections from 108 coronary arterial segments of 40 consecutive human cadavers (24 men and 16 women; mean age 74 +/- 7 years). The plaque type was classified as fibrous (n = 43), fibrocalcific (n = 82), or lipid-rich (n = 41). The accuracy of OCT and intravascular ultrasound (IVUS) in characterizing the plaque type was studied, with the histologic consensus diagnosis serving as the gold standard. OCT, as well as IVUS, had high sensitivity and specificity for characterizing the different types of atherosclerotic plaque. OCT had a higher sensitivity for characterizing lipid-rich plaques than IVUS (85% vs 59%, p = 0.03). In conclusion, the high resolution of OCT permitted evaluation of lipid-rich plaques more accurately than IVUS.

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PubMed2006

Measurement of the thickness of the fibrous cap by optical coherence tomography.

BACKGROUND: Identification of the fibrous cap is important because its thickness is a major determinant of plaque vulnerability in lipid-rich plaque. Thus, a high-resolution imaging technique may be a promising method for the identification of the fibrous cap within lipid-rich plaque. The purpose of this study was to investigate the feasibility of using optical coherence tomography (OCT) to measure the thickness of the fibrous cap within lipid-rich plaque. METHODS AND RESULTS: We examined 35 lipid-rich plaques from 102 coronary arterial segments of 38 human cadavers (22 men and 16 women; mean ages, 74 +/- 7 years). Optical coherence tomography and corresponding histological images were digitized for measurement of the thickness of fibrous cap, and the results between OCT and histological examination were compared. There was good correlation of the thickness of the fibrous cap between OCT and histological examination (y = 0.97x + 28.49; r = 0.90; P < .001). A Bland-Altman test showed good agreement of the thickness of the fibrous cap between OCT and histological examination (mean difference, -24 +/- 44 microm). CONCLUSIONS: Optical coherence tomography provides an accurate representation of the thickness of the fibrous cap and may prove useful in assessing plaque vulnerability in lipid-rich plaque.

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PubMed2006

Geometric differences of the mitral valve tenting between anterior and inferior myocardial infarction with significant ischemic mitral regurgitation: quantitation by novel software system with transthoracic real-time three-dimensional echocardiography.

We sought to investigate the 3-dimensional geometric differences of mitral leaflet tenting in ischemic mitral regurgitation, comparing inferior and anterior myocardial infarction (MI). Using real-time 3-dimensional echocardiography, we obtained transthoracic volumetric images for patients with significant ischemic mitral regurgitation (9 inferior and 7 anterior). With our novel software system, 3-dimensional images of the leaflets were reconstructed for quantitation. Mitral leaflet configuration was then represented in contour in which the degree of the tenting could be observed. Calculated percent of tethered leaflet area (>5-mm tenting from the annular level) was compared in inferior and anterior MI. Percent of tethered leaflet area was significantly smaller in inferior than anterior MI, reflecting the localized leaflet tenting in inferior MI (16.7 +/- 18.8% vs 38.9 +/- 9.7%, P = .01). In anterior MI, mitral valve leaflets were widely tethered toward the left ventricle, in contrast with inferior MI showing localized tenting of the leaflet.

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PubMed2006

Heterogeneity of myocardial perfusion in distal coronary embolism with different particle sizes.

BACKGROUND: We hypothesized that altered myocardial perfusion distribution patterns could be seen with coronary distal emboli of different particle sizes using myocardial contrast echocardiography. METHODS: In 16 open-chest anesthetized dogs, microsphere suspensions of 9 or 500 microm in diameter were injected into the left anterior descending coronary artery until the mean left anterior descending coronary artery flow rate was reduced to less than 30% of baseline flow. During baseline conditions and after maximal embolization, real-time myocardial contrast echocardiography was performed by intravenous infusion of an echocontrast agent. RESULTS: In animals infused with 9-microm microspheres, a transmural perfusion defect was seen at the time of maximal embolization. In contrast, in animals infused with 500-microm microspheres, a subendocardial perfusion defect was observed. CONCLUSIONS: The particle size of coronary distal emboli affects myocardial perfusion distribution.

Animals↗
PubMed2006

Rate of progression of valvular aortic stenosis in patients undergoing dialysis.

BACKGROUND: In patients undergoing dialysis, aortic valve calcification and aortic stenosis are frequently found. However, the rate of progression of aortic stenosis is still unclear. METHODS: In all, 55 consecutive patients undergoing dialysis were followed up by echocardiography for a period of 12 months. Patients were divided into two groups: noncalcification (no or mildly calcified aortic valve) and calcification (moderate or heavily calcified aortic valve). RESULTS: The rate of progression of maximum aortic jet velocity and degression of aortic valve area were more rapid in calcification group than in noncalcification group (0.37 +/- 0.36 m/s and 0.17 +/- 0.29 m/s, P = .027; 0.17 +/- 0.15 cm2 and 0.04 +/- 0.07 cm2, P < .001, respectively). CONCLUSIONS: The degree of aortic stenosis progressed more rapidly in patients undergoing dialysis with aortic valve calcification than without aortic valve calcification.

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PubMed2005

Low-dose aspirin for prevention of stroke in low-risk patients with atrial fibrillation: Japan Atrial Fibrillation Stroke Trial.

BACKGROUND AND PURPOSE: Although the efficacy of anticoagulant therapy for primary prevention of stroke in patients with nonvalvular atrial fibrillation (NVAF) has been established, efficacy of antiplatelet therapy for low-risk patients is disputable in Japanese patients because of the frequent hemorrhagic complications. We examined the efficacy and safety of aspirin therapy in Japanese patients with NVAF in a prospective randomized multicenter trial. METHODS: Patients with NVAF were randomized to an aspirin group (aspirin at 150 to 200 mg per day) or a control group without antiplatelet or anticoagulant therapy. Primary end points included cardiovascular death, symptomatic brain infarction, or transient ischemic attack. RESULTS: A total of 426 patients were randomized to aspirin group and 445 to no treatment. The trial was stopped earlier because there were 27 primary end point events (3.1% per year; 95% CI, 2.1% to 4.6% per year) in the aspirin group versus 23 (2.4% per year; 95% CI, 1.5% to 3.5% per year) in the control group, suggesting a low possibility of superiority of the aspirin treatment for prevention of the primary end point. In addition, treatment with aspirin caused a marginally increased risk of major bleeding (7 patients; 1.6%) compared with the control group (2 patients; 0.4%; Fisher exact test P=0.101). CONCLUSIONS: For prevention of stroke in patients with NVAF, aspirin at 150 to 200 mg per day does not seem to be either effective or safe. Further prospective studies are needed to determine the best preventive therapy for cerebrovascular events in Japanese patients with NVAF.

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PubMed2005

Comparison of high-frequency two-dimensional transthoracic echocardiography versus intravascular ultrasound for evaluation of the left anterior descending coronary artery.

The purpose of this study was to evaluate the feasibility of high-frequency transthoracic echocardiography for measuring the wall thickness and luminal area of the left anterior descending coronary artery (LAD). Fifteen patients underwent simultaneous high-frequency transthoracic echocardiography and intravascular ultrasound (IVUS) examinations. There were good agreements for wall thickness (0.38 +/- 0.05 vs 0.38 +/- 0.06 mm, p = 0.0004) and luminal area (3.24 +/- 1.05 vs 3.32 +/- 1.34 mm2, p <0.0001) between high-frequency transthoracic echocardiography and IVUS measurements. High-frequency transthoracic echocardiography was reliable in the measurement of the wall thickness and luminal area of the LAD.

Angina Pectoris↗
PubMed2005

Mitral annulus flattens in ischemic mitral regurgitation: geometric differences between inferior and anterior myocardial infarction: a real-time 3-dimensional echocardiographic study.

BACKGROUND: New surgical strategies to restore the saddle shape of the mitral annulus are expected to increase annuloplasty effectiveness. Preoperative and postoperative configuration of the curved annulus, however, is difficult to quantify with 2-dimensional echocardiography. We sought to investigate the geometric deformity in the mitral annulus in ischemic mitral regurgitation (MR), comparing inferior and anterior myocardial infarction (MI) with the use of a custom quantitation software system with transthoracic 3-dimensional echocardiography. METHODS AND RESULTS: We performed real-time 3-dimensional echocardiography in 23 patients with ischemic MR attributable to inferior MI or anterior MI and in 10 controls. Three-dimensional data were cropped into 18 radial planes, and we manually marked the annulus in mid systole. Three-dimensional annular images were reconstructed, and annular circumferences, areas, and heights were quantified. Annulus was significantly more dilated and flattened in ischemic MR than in controls and was further deformed in anterior MI as compared with inferior MI (control: circumference 9.9+/-0.7 cm, area 9.6+/-0.5 cm2, height 5.0+/-0.7 mm; inferior MI: circumference 11.5+/-1.2 cm [P<0.01 compared with control], area 11.4+/-2.0 cm2 [P<0.05 compared with control], height 3.5+/-1.6 mm [P<0.05 compared with control]; anterior MI: circumference 14.2+/-2.4 cm [P<0.0001 compared with control, P<0.05 compared with inferior MI], area 13.7+/-2.8 cm2 [P<0.01 compared with control, P<0.05 compared with inferior MI], height 1.7+/-1.5 mm [P<0.0001 compared with control, P<0.05 compared with inferior MI]). CONCLUSIONS: Mitral annulus flattens in ischemic MR. Deformity of the mitral annulus was greater in anterior MI group than in the inferior MI group.

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PubMed2005

Evaluation of bioavailability of nitric oxide in coronary circulation by direct measurement of plasma nitric oxide concentration.

Although bioavailability of NO in the coronary circulation is commonly evaluated by acetylcholine (ACh)-induced vasodilation, a change in plasma NO concentration and its relation to the flow response after injection of ACh are still unknown. Thus, we directly measured the concentration of NO in the coronary sinus by using a catheter-type NO sensor for coronary sinus. An NO-sensitive sensor was located and fixed in a 4-Fr catheter with a soft tip for protection of vascular wall. After calibration with an NO-saturated pure water, the catheter-type NO sensor was located in the coronary sinus in anesthetized dogs. The coronary flow velocity (CFV) was measured with a Doppler guide wire. Intracoronary injection of ACh (0.4 and 1.0 microg/kg) increased plasma NO concentration in a dose-dependent manner (3-10 nM). Although ACh increased CFV by 95%, there was no significant difference between the two ACh doses. After ACh, the peak value of plasma NO concentration was observed significantly later than CFV. N(G)-methyl-L-arginine (NO synthase inhibitor) decreased basal NO concentration by 3 nM and suppressed the ACh-induced NO synthesis with no significant change in average peak velocity. We conclude that production of NO in the coronary circulation can be evaluated in the coronary sinus. Although ACh increases both CFV and NO concentration, CFV dose not reflect NO concentration in terms of magnitude and time course. Direct measurement of plasma NO concentration by the catheter-type NO sensor is useful to evaluate bioavailability of NO in the coronary circulation.

Acetylcholine↗
PubMed2005

Quantitation of mitral valve tenting in ischemic mitral regurgitation by transthoracic real-time three-dimensional echocardiography.

OBJECTIVES: We sought to investigate the geometric changes of the mitral leaflets and annulus, clarify the maximum tenting site of the leaflets, and quantify the valve tenting in ischemic mitral regurgitation (MR) using three-dimensional (3D) echocardiography. BACKGROUND: Although the understanding of the mechanisms of ischemic MR has advanced recently, the geometric changes of the mitral leaflets and annulus have been assessed by two-dimensional echocardiography in the clinical setting, despite the unique configuration of the leaflets and annulus. METHODS: Utilizing real-time 3D echocardiography, we obtained transthoracic volumetric images in 12 patients with ischemic MR presenting with global left ventricular dysfunction and in 10 controls. Original software was used to crop the 3D data into 18 radial planes, and we marked the mitral annulus and leaflets in each plane in mid-systole. The 3D images of the leaflets and annulus were reconstructed for the quantitative measurements. RESULTS: In ischemic MR, the annulus flattened with apparent tenting of the leaflets. Maximum and mean tenting length were longer and tenting volume was larger in ischemic MR than control subjects (maximum tenting length: 9.8 +/- 2.0 mm vs. 3.1 +/- 1.2 mm, p < 0.0001, mean tenting length: 3.7 +/- 0.9 mm vs. 0.7 +/- 0.5 mm, p < 0.0001, tenting volume: 4.09 +/- 1.22 ml vs. 0.45 +/- 0.29 ml, p < 0.0001). The maximum tenting site was located in anterior leaflet in all patients. CONCLUSIONS: We clearly demonstrated 3D geometric deformity of the mitral leaflets and annulus in ischemic MR using novel software for creating images by 3D echocardiography. This technique will be helpful in making a proper decision for the surgical strategy in each patient.

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PubMed2005

Reduced coronary flow reserve in patients with congestive heart failure assessed by transthoracic Doppler echocardiography.

BACKGROUND: Although coronary flow reserve (CFR) has been reported to be restricted in various conditions, there has been no report of CFR for patients with congestive heart failure (CHF). The purpose of this study was to assess coronary flow characteristics for patients with CHF. METHODS: We studied 15 patients with CHF: 8 with dilated myocardiopathy and 7 with hypertensive heart disease. Phasic coronary flow velocities were obtained in the left anterior descending coronary artery at rest and during hyperemia (0.15 mg/kg/min adenosine triphosphate infusion intravenously) by transthoracic echocardiography before and after treatment of CHF. CFR was obtained from the ratio of hyperemic/baseline diastolic mean velocity. RESULTS: CFR was significantly restricted in the condition of CHF compared with that after improvement of CHF (1.5 +/- 0.2 vs 2.0 +/- 0.3, P < .01). Baseline diastolic mean velocity in the condition with CHF was significantly greater than that after improvement of CHF (41 +/- 13 cm/s vs 33 +/- 13 cm/s, P = .04), although maximal hyperemic diastolic mean velocity was not significantly different before and after improvement of CHF (63 +/- 20 cm/s vs 61 +/- 19 cm/s, P = .68). After improvement of CHF, heart rate, along with left ventricular end-diastolic volume and dimension, were significantly decreased, and deceleration time of transmitral early filling flow was increased compared with before treatment of CHF. Blood pressure and ejection fraction were not significantly different before and after treatment of CHF. CONCLUSIONS: Restriction of CFR is demonstrated during CHF because of the elevation of baseline resting flow velocity, which might be related to increase in left ventricular preload and heart rate.

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PubMed2005

Transthoracic Doppler echocardiographic assessment of coronary flow velocity pattern in patient with acute myocardial infarction implies progression of myocardial damage.

BACKGROUND: Coronary flow velocity (CFV) pattern with a rapid deceleration time of diastolic flow velocity and small average systolic peak velocity immediately after reperfusion implies poor wall-motion recovery in patients with acute myocardial infarction. Microvascular injury has been demonstrated to progress after coronary reperfusion. The purpose of this study was to assess whether CFV 1 day after reperfusion (day 1) may reflect accurately the degree of myocardial damage. METHODS: In the left anterior descending coronary artery in 29 patients with anterior acute myocardial infarction, CFV was measured immediately and 1 day after recanalization using transthoracic Doppler echocardiography, respectively. Regional wall motion was estimated as anterior wall-motion score index (AWMSI) by echocardiography before recanalization and 1 month after the onset of acute myocardial infarction. RESULTS: Although significant correlation was observed among deceleration time of diastolic flow velocity, average systolic peak velocity, and average peak velocity immediately after reperfusion and 1-month AWMSI (r = -0.62, P < .001; r = -0.61, P < .001; and r = -0.55, P < .01, respectively), much better correlation was demonstrated between those at day 1 and 1-month AWMSI (r = -0.72, P < .0001; r = -0.68, P < .0001; and r = -0.60, P < .001, respectively). Deceleration time of diastolic flow velocity, average systolic peak velocity, and average peak velocity in poor wall-motion recovery group (1-month AWMSI > 2.0, n = 14) were significantly smaller (P < .01, P < .05, and P < .05, respectively) at day 1 compared with those immediately after reperfusion. CONCLUSIONS: CFV pattern assessed by transthoracic Doppler echocardiography at day 1 provides the degree of myocardial damage much more accurately than that immediately after reperfusion. These results may suggest that myocardial damage progresses after reperfusion.

Blood Flow Velocity↗
PubMed2005

Assessment of coronary intima--media thickness by optical coherence tomography: comparison with intravascular ultrasound.

BACKGROUND: Optical coherence tomography (OCT) is a new imaging method. With a resolution of approximately 10-20 Em, which is approximately 10-fold higher than that of intravascular ultrasound (IVUS). METHODS AND RESULTS: This study compared the coronary intima - media thickness (IMT) and the intimal thickness of 54 coronary arterial segments evaluated by histological examination with the results of OCT and IVUS. There was better agreement in IMT between OCT and histological examination than between IVUS and histological examination (r = 0.95, p < 0.001, mean difference = -0.01+/-0.07 mm for OCT; r = 0.88, p < 0.001, mean difference = -0.03+/-0.10 mm for IVUS). There was good agreement in the intimal thickness between OCT and histological examination (r = 0.98, p < 0.001, mean difference = 0.01+/-0.04 mm). CONCLUSIONS: IMT could be measured more accurately by OCT than IVUS. In addition, the intimal thickness could be evaluated by OCT and correlated well with the histological examination.

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PubMed2005

Assessment of coronary microcirculation in patients with takotsubo-like left ventricular dysfunction.

BACKGROUND: The precise mechanism of takotsubo-like left ventricular (LV) dysfunction remains unclear. METHODS AND RESULTS: Eight consecutive patients with takotsubo-like LV dysfunction were studied. In the acute phase and 3 weeks later, the coronary flow velocity spectrum and coronary flow velocity reserve (CFVR) were recorded by Doppler guidewire. The deceleration time of diastolic velocity (DDT; ms) was measured from the peak diastolic velocity to the point where the extrapolated line intersected the baseline. In all cases, CFVR of the 3 coronary arteries increased during follow-up (1.7+/-0.5 to 2.4+/-0.5 for the left anterior descending artery (p < 0.05), 1.7+/-0.5 to 2.7+/-0.8 for the left circumflex artery (p < 0.05) and 1.7+/-0.3 to 2.5+/-0.4 for the right coronary artery (p < 0.05)). In addition, the DDT of all coronary arteries increased during follow-up. CONCLUSIONS: Decreased CFVR and short DDT were demonstrated in patients with takotsubo-like transient LV dysfunction in the acute phase, and these findings improved 3 weeks later, which suggests that coronary microvascular dysfunction may be a causative mechanism.

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