Biomedical subjects

Hajime Yamashita

Publications and source records attributed to Hajime Yamashita.

7 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.

Age Factors↗

PubMed2006

Risk stratification in patients with Brugada syndrome: analysis of daily fluctuations in 12-lead electrocardiogram (ECG) and signal-averaged electrocardiogram (SAECG).

INTRODUCTION: Risk stratification between symptomatic and asymptomatic patients with Brugada syndrome is not yet established. We compared daily fluctuations in 12-lead electrocardiogram (ECG) and signal-averaged ECG (SAECG) characteristics between symptomatic and asymptomatic patients with Brugada syndrome to identify new markers for distinguishing between high- and low-risk patients. METHODS AND RESULTS: Thirty-five patients with Brugada syndrome underwent ECG and SAECG simultaneously at least 4 times every 3 months. We evaluated daily fluctuations (differences between maximum and minimum values) in ECG and SAECG characteristics and compared them between symptomatic (N = 11), and asymptomatic (N = 24) patients. On ECG, the daily fluctuations in r-J interval (interval from QRS onset to J point) in leads V1, V2, and V6 were significantly larger in symptomatic than in asymptomatic patients (V1; 20 +/- 6 vs 10 +/- 8 msec, P < 0.01, V2; 22 +/- 8 vs 11 +/- 4 msec, P < 0.01, and V6; 24 +/- 7 vs 14 +/- 7 msec, P < 0.01). On SAECG, daily fluctuations in filtered QRS (f-QRS) duration and LAS40 were significantly larger in symptomatic than in asymptomatic patients (f-QRS; 15 +/- 7 vs 9 +/- 4 msec, P < 0.05, and LAS40; 21 +/- 7 vs 10 +/- 6 msec, P < 0.05). CONCLUSIONS: Instability of depolarization appears to be related to the risk of fatal ventricular arrhythmias in patients with Brugada syndrome. Daily fluctuations in ECG and SAECG characteristics could be useful for distinguishing between high- and low-risk patients with Brugada syndrome.

Brugada Syndrome↗

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.

Animals↗

PubMed2005

Comparison of levels of serum matrix metalloproteinase-9 in patients with acute myocardial infarction versus unstable angina pectoris versus stable angina pectoris.

Matrix metalloproteinases (MMPs) are important for resorption of extracellular matrixes and may degrade the fibrous cap of an atherosclerotic plaque, thus contributing to coronary plaque rupture. Histologic studies have shown MMP expression in lesions of acute coronary syndrome. In this study, we evaluated the relation between plaque morphology as obtained by intravascular ultrasound before percutaneous coronary intervention and serum MMP levels in patients who had coronary artery disease. We enrolled consecutive 47 patients who had acute myocardial infarction (AMI), 23 who had unstable angina pectoris (UAP), and 19 who had stable effort angina pectoris and underwent intravascular ultrasound before percutaneous coronary intervention followed by successful primary percutaneous coronary intervention. Peripheral blood was obtained from all patients before angiography and serum levels of MMP-1,-2, and -9 were analyzed. Serum levels of MMP-9 in the AMI and UAP groups were significantly higher than that in the stable effort angina pectoris group (p = 0.007 and 0.04, respectively). From the intravascular ultrasound findings before percutaneous coronary intervention, plaque rupture was detected in 26 patients (55%) in the AMI group and in 11 patients (48%) in the UAP group. In these 2 groups, patients with plaque rupture had significantly higher levels of MMP-9 than patients who did not have plaque rupture (p = 0.03 and 0.01, respectively). Multiple logistic regression analysis showed that MMP-9 was the only independent predictor of plaque rupture (p = 0.004). In conclusion, high levels of MMP-9 in patients who have AMI and UAP are related to the presence of plaque rupture in the culprit lesion.

Aged↗

PubMed2004

Spotty calcification typifies the culprit plaque in patients with acute myocardial infarction: an intravascular ultrasound study.

BACKGROUND: Calcification is a common finding in human coronary arteries; however, the relationship between calcification patterns, plaque morphology, and patterns of remodeling of culprit lesions in a comparison of patients with acute coronary syndromes (ACS) and those with stable conditions has not been documented. METHODS AND RESULTS: Preinterventional intravascular ultrasound (IVUS) images of 178 patients were studied, 61 with acute myocardial infarction (AMI), 70 with unstable angina pectoris (UAP), and 47 with stable angina pectoris (SAP). The frequency of calcium deposits within an arc of less than 90 degrees for all calcium deposits was significantly different in culprit lesions of patients with AMI, UAP, and SAP (P<0.0001). Moreover, the average number of calcium deposits within an arc of <90 degrees per patient was significantly higher in AMI than in SAP (P<0.0005; mean+/-SD, AMI 1.4+/-1.3, SAP 0.5+/-0.8). Conversely, calcium deposits were significantly longer in SAP patients (P<0.0001; mean+/-SD, AMI 2.2+/-1.6, UAP 1.9+/-1.8, and SAP 4.3+/-3.2 mm). In AMI patients, the typical pattern was spotty calcification, associated with a fibrofatty plaque and positive remodeling. In ACS patients showing negative remodeling, no calcification was the most frequent observation. Conversely, SAP patients had the highest frequency of extensive calcification. CONCLUSIONS: Our observations show that IVUS allows the identification of vulnerable plaques in coronary arteries, not only by identifying a fibrofatty plaque and positive remodeling, but also by identifying a spotty pattern of calcification.

Aged↗

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.

Aged↗

PubMed2003

Marked improvement of left ventricular function after parathyroidectomy in a hemodialysis patient with secondary hyperparathyroidism and left ventricular dysfunction.

A 52-year-old woman, a hemodialysis patient, was admitted because of exertional dyspnea. Echocardiography showed left ventricular (LV) dilatation and reduced contraction. Coronary angiography showed no fixed stenosis. She had elevated levels of parathyroid hormone (PTH) as a result of secondary hyperparathyroidism with advanced renal failure. After parathyroidectomy, marked improvement of LV function following immediate decrease of blood levels of PTH was observed. It is suggested that PTH might have a significant role in the pathogenesis of LV dysfunction and that parathyroidectomy might be effective as a therapy for heart failure in some patients with secondary hyperparathyroidism and LV dysfunction.

Electrocardiography↗