Kenichi Obara
University of Tsukuba
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Featured researches published by Kenichi Obara.
Heart and Vessels | 2004
Tomoko Ishizu; Toshiyuki Ishimitsu; Hisako Yanagi; Yoshihiro Seo; Kenichi Obara; Naoko Moriyama; Shigeyuki Watanabe; Iwao Yamaguchi
To investigate relationships between carotid arterial intima-media thickness (IMT) and age in childhood, we performed high-resolution carotid arterial ultrasonography in 60 healthy children (27 boys, 33 girls; age range, 5–14 years) determined by screening to have no dyslipidemia or hypertension. No plaque formation was found, and irregularity of IMT (root mean square roughness of IMT) did not correlate with age. Mean IMT increased in a linear manner with age [IMT in millimeters = (0.009 × age in years) + 0.35] (r = 0.39, P = 0.002). This correlation remained significant after adjustment for gender, parental smoking, systolic and diastolic blood pressure, body mass index, and serum concentrations of low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, and triglycerides. None of these known cardiovascular disease risk factors in adults had a significant relationship with age-adjusted IMT in children. While circumferential wall stress and diastolic blood pressure were not correlated with age, mean IMT and lumen diameter showed significant positive relationships with circulating blood volume, which was calculated as the function of height and weight. These data suggested that age-dependent physiologic thickening of arterial walls begins in childhood.
Heart and Vessels | 2002
Tomoko Ishizu; Toshiyuki Ishimitsu; Hideki Kamiya; Yoshihiro Seo; Naoko Moriyama; Kenichi Obara; Shigeyuki Watanabe; Iwao Yamaguchi
Abstract. Noninvasive ultrasonographic assessment of carotid artery intima-media thickness (IMT) can improve risk stratification for coronary artery disease (CAD) in certain patients. Several measurements have been used to evaluate carotid atherosclerosis by ultrasonography. Although it has been reported that angiographic arterial irregularities correlate with pathologic changes of atherosclerosis and the occurrence of cardiovascular events, only a few studies have assessed carotid arterial wall irregularity by ultrasonography. The purpose of this study was to evaluate the irregularity of IMT quantitatively, and its association with the presence or absence of CAD. The correlation of maximum and mean IMT values, and IMT irregularity with the presence or absence of CAD, was investigated in 90 patients who had undergone coronary angiography. IMT was measured by manual tracking of the far wall of the common carotid arteries, carotid bulbs, and internal carotid arteries. The IMT irregularity was defined as the root mean square (RMS) difference between each IMT and averaged IMT. Multiple logistic regression analysis, after adjustment for coronary risk factors, indicated that the RMS difference was a more accurate predictor of CAD than were the mean or maximum IMT values. These results indicate that the evaluation of IMT irregularity by ultrasonography is a useful predictor for the presence of coronary atherosclerosis.
Echocardiography-a Journal of Cardiovascular Ultrasound and Allied Techniques | 2006
Tomoko Ishizu; Yoshihiro Seo; Toshiyuki Ishimitsu; Kenichi Obara; Naoko Moriyama; Satoru Kawano; Shigeyuki Watanabe; Iwao Yamaguchi
Although an intraventricular filling delay has been observed in patients with a psuedonormalized transmitral flow pattern, little is known about the underlying hydrodynamic nature of this phenomenon. Methods: To examine those hydrodynamics, we studied every echocardiographic frame showing ventricular inflow (80 Hz) in the apical long‐axis view and M‐mode image using contrast echocardiography in 29 patients with a psuedonormalized pattern and in 26 normal controls. The velocity of the filling flow front (Vp), the ratio of Vp to E, and the mean radius of the vortices associated with the filling flow were measured. Results: In both groups, vortices were observed at the ridge of the mitral valve during acceleration of the E‐wave. The mean radius of the vortices was greater in the pseudonormalized filling group than that in the control group (8 ± 2 vs 3 ± 1 mm, P < 0.0001). Vp was smaller in the pseudonormalized group than in the control group (36 ± 6 vs 47 ± 6 cm/sec, P = 0.0008). Vp/E was <1 and smaller in the pseudonormalized group than that in the control group (0.46 ± 0.13 vs 0.59 ± 0.07, P = 0.014) and negatively correlated with the mean radius of the vortices (r = 0.54, P < 0.0001). Conclusions: Contrast echocardiography identified uniform flow characteristics with blood in the filling flow front moving in well‐developed vortices and resulting in a left ventricular filling delay in the impaired left ventricle in spite of an increased early transmitral flow velocity.
International Heart Journal | 2018
Isao Nishi; Yoshihiro Seo; Yoshie Hamada-Harimura; Kimi Sato; Seika Sai; Masayoshi Yamamoto; Tomoko Ishizu; Akinori Sugano; Kenichi Obara; Longmei Wu; Shoji Suzuki; Akira Koike; Kazutaka Aonuma
Controlling nutritional status (CONUT) uses 2 biochemical parameters (serum albumin and cholesterol level), and 1 immune parameter (total lymphocyte count) to assess nutritional status. This study examined if CONUT could predict the short-term prognosis of heart failure (HF) patients.A total of 482 (57.5%) HF patients from the Ibaraki Cardiovascular Assessment Study-HF (n = 838) were enrolled (298 men, 71.7 ± 13.6 years). Blood samples were collected at admission, and nutritional status was assessed using CONUT. CONUT scores were defined as follows: 0-1, normal; 2-4, light; 5-8, moderate; and 9-12, severe degree of undernutrition. Accordingly, 352 (73%) patients had light-to-severe nutritional disturbances. The logarithmically transformed plasma brain natriuretic peptide (log BNP) concentration was significantly higher in the moderate-severe nutritional disturbance group (2.92 ± 0.42) compared to the normal group (2.72 ± 0.45, P < 0.01). CONUT scores were significantly higher in the in-hospital death patients [4 (3-8), n = 14] compared with patients who were discharged following symptom alleviation [3 (1-5), n = 446, P < 0.05]. With the exception of transferred HF patients (n = 22), logistic regression analysis that incorporated the CONUT score and the log BNP, showed that a higher CONUT score (P = 0.019) and higher log BNP (P = 0.009) were predictors of in-hospital death, and the median duration of hospital stay was 20 days.Our results demonstrate the usefulness of CONUT scores as predictors of short-term prognosis in hospitalized HF patients.
Heart and Vessels | 2013
Hiroaki Watabe; Akira Sato; Tomoya Hoshi; Kenichi Obara; Ryo Kawamura; Kazutaka Aonuma
Coronary stent loss during percutaneous coronary intervention is rare and is often associated with significant morbidity. Several retrieval techniques, overlying stent deployment and crushing, and surgical removal can be used to deal with a stent lost in the coronary system. We successfully treated a dislodged and mechanically distorted coil stent stuck within a previously implanted drug-eluting stent (DES) by stent-crush technique. This case might provide insight into the mechanisms responsible for the longitudinal fragility of cobalt alloy and coil-structure stents and stent fracture of DES. In the DES era, careful attention should be paid to such complications when attempting to deliver a stent to a distal vessel through a pre-existing DES.
Circulation | 2017
Masayoshi Yamamoto; Yoshihiro Seo; Tomoko Ishizu; Isao Nishi; Yoshie Hamada-Harimura; Tomoko Machino-Ohtsuka; Kimi Sato; Seika Sai; Akinori Sugano; Kenichi Obara; Kazutaka Aonuma
BACKGROUND Although experimental animal studies report many pleiotropic effects of dipeptidyl peptidase-4 inhibitors (DPP-4i), their prognostic value has not been demonstrated in clinical trials.Methods and Results:Among 838 prospectively enrolled heart failure (HF) patients hospitalized for acute decompensated HF, 79 treated with DPP-4i were compared with 79 propensity score-matched non-DPP-4i diabetes mellitus (DM) patients. The primary endpoint was all-cause mortality; the secondary endpoint was a composite of cardiovascular death and hospitalization. During follow-up (423±260 days), 8 patients (10.1%) in the DPP-4i group and 13 (16.5%) in the non-DPP-4i group died (log-rank, P=0.283). The DPP-4i group did not have a significantly higher rate of all-cause mortality (log-rank, P=0.283), or cardiovascular death or hospitalization (log-rank, P=0.425). In a subgroup analysis of HF with preserved ejection fraction (HFpEF; n=75), the DPP-4i group had a significantly better prognosis than the non-DPP-4i group regarding the primary endpoint (log-rank, P=0.021) and a tendency to have better prognosis regarding the secondary endpoint (log-rank, P=0.119). In patients with HF with reduced EF (n=83), DPP-4i did not result in better prognosis. CONCLUSIONS DPP-4i did not increase the risk of adverse clinical outcomes in patients with DM and HF. DPP-4i may be beneficial in HFpEF.
Journal of The American Society of Echocardiography | 2004
Yoshihiro Seo; Toshiyuki Ishimitsu; Tomoko Ishizu; Kenichi Obara; Naoko Moriyama; Satoru Kawano; Shigeyuki Watanabe; Iwao Yamaguchi
Journal of The American Society of Echocardiography | 2004
Yoshihiro Seo; Toshiyuki Ishimitsu; Tomoko Ishizu; Kenichi Obara; Naoko Moriyama; Michiko Sakane; Hiroshi Maeda; Shigeyuki Watanabe; Iwao Yamaguchi
International Heart Journal | 2008
Tomoko Machino; Masahiro Toyama; Kenichi Obara; Noriyuki Takeyasu; Shigeyuki Watanabe; Kazutaka Aonuma
Heart and Vessels | 2017
Isao Nishi; Yoshihiro Seo; Yoshie Hamada-Harimura; Kimi Sato; Seika Sai; Masayoshi Yamamoto; Tomoko Ishizu; Akinori Sugano; Kenichi Obara; Longmei Wu; Shoji Suzuki; Akira Koike; Kazutaka Aonuma