Biomedical subjects

Koichiro Asawa

Publications and source records attributed to Koichiro Asawa.

4 recordsLinked to original sources

PubMed2006

Acute myocardial infarction: clinical characteristics and plaque morphology between expansive remodeling and constrictive remodeling by intravascular ultrasound.

BACKGROUND: According to recent intravascular ultrasound (IVUS) studies, expansive remodeling (ER) at the culprit lesion has been observed in almost 50% of patients with acute coronary syndrome and constrictive remodeling (CR) in 30%. The purpose of this study is to investigate the difference between ER and CR at the culprit lesion in patients with acute myocardial infarction (AMI). METHODS AND RESULTS: Preinterventional IVUS images of 73 patients with AMI were identified. The remodeling index (RI) was defined as the ratio of the external elastic membrane (EEM) areas at the culprit lesion to the EEM areas at the proximal reference site. Expansive remodeling was defined as an RI > 1.05; CR, as an RI < 0.95. In patients with AMI, 40 patients (55%) showed ER on IVUS, whereas CR was observed in 18 patients (25%). Patients with ER were significantly older than those with CR (P < .005). The frequency of the presence of calcifications was higher in patients with ER than in those with CR (P < .0005). In patients with AMI with ER, soft plaque with small calcium was the most frequent (58%). Multivariate analysis revealed that age and the presence of calcifications remained as independent predictors of ER. CONCLUSIONS: These findings suggest that ER relates to old age and calcification, and CR may contribute to early plaque progression than ER in patients with AMI.

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PubMed2006

Method analysis for optimal continuous imaging using intravascular optical coherence tomography.

OBJECTIVES: Optical coherence tomography(OCT)is a high-resolution imaging method that can clearly visualize vessels through the displacement of blood with flushing agents. Continuous imaging methods have not been established. This study investigated optimal methods for continuous OCT imaging. METHODS: Thirty-four arteries with stent implantation (24 peripheral and 10 coronary arteries)in 14 pigs were examined using OCT with a motorized pullback device. Two imaging methods (flush alone by liquid substance and flush with occlusion) were compared. Adequate image acquisition was defined as the entire circumferential intimal layer being detectable within continuous segments. To investigate factors that could influence image quality, stented regions were divided into 4-5 mm segments. RESULTS: The flush with occlusion method provided better OCT images compared to flush alone (flush with occlusion: 60.9%, flush alone: 8.7%, p = 0.0002). Using the flush with occlusion method, the rate of adequate image acquisition was 64.4% and visualization of > 75% intimal circumference was 83.5%. Intravascular ultrasound could detect all stented regions. Segmental analyses found more adequate images were detected in smaller vessels (adequate segment: 3.8 +/- 0.4 mm, inadequate segment: 4.2 +/- 0.8 mm, p < 0.0001) or with centered image wire position (adequate segment: center 35%, inadequate segment: center 14%, p = 0.003). In addition, side branches did not affect image quality. CONCLUSIONS: To acquire continuous OCT images, the flush with occlusion method was more effective compared to flush alone. Moreover, image quality is affected by vessel size and imaging wire position. These results suggest that optimized OCT imaging can provide continuous vessel detection.

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PubMed2004

Quadricuspid aortic valve: report of three cases.

Quadricuspid aortic valve (QAV) is a very rare congenital malformation. We have encountered three patients with QAV, of whom one patient may be the eldest reported patient with this particular anatomical abnormality. In another of our patients, there was aortic regurgitation, aortic stenosis, and healed infective endocarditis, with adhesion of the tips of the cusps. In all three patients, the cusps were all of equal size. Until now, there has been very little documented evidence about the anatomical variations in QAV or its relationship with infective endocarditis. From the available literature, we conclude that the anatomical variations in patients with QAV are similar to those in patients with quadricuspid pulmonary valve, and infective endocarditis may not be an uncommon complication.

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PubMed2004

Impact of HMG-CoA reductase inhibitors for non-treated coronary segments.

BACKGROUND: HMG-CoA reductase inhibitors (statin) have been reported to decrease coronary artery events in several angiographic studies. However, the mechanism by which statin achieve this is still unclear. The purpose of this study was to identify the effect of statin on coronary plaque using serial intravascular ultrasound analysis. METHODS AND RESULTS: In this study, 48 patients with 48 lesions were divided into the prescribed group (statin group, n = 22) or the non-prescribed group (control group, n = 26) after successful coronary artery stenting. IVUS images were obtained at consecutive 5 mm segments, 5 mm from the proximal stent edge, immediately after stenting and at 6 months follow up. External elastic membrane volume (EEMV), lumen volume (LV) and plaque volume (PV) were measured using Simpson's method. The control group revealed no significant serial change in EEMV, PV, and LV during 6 months. On the other hand, the statin group revealed significant reductions of PV (35.5 +/- 12.7 mm3 vs 30.9 +/- 15.6 mm3, p = 0.001), resulting in increase of LV (47.7 +/- 19.8 mm3 vs 52.5 +/- 22.2 mm3, p = 0.003) without EEMV change (82.8 +/- 21.8 mm3 vs 83.9 +/- 25.7 mm3, p = NS). Although percent EEMV and percent LV changes showed no differences between the two groups, a larger percent PV change was observed in the statin group compared to the control group (control; 5.8 +/- 20.3% vs statin; -20.4 +/- 21.8%, p = 0.02). CONCLUSION: The results of this study suggest that statin administration for 6 months reduces coronary plaque without positive vessel remodeling.

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