文献一覧: Masayoshi Yamamoto (著者)

15 0 0 0 OA Prognostic Implications of Reductions in Heart Rates in Patients With Acute Heart Failure and Atrial Fibrillation

著者: Keisuke Kida Takeshi Kitai Norio Suzuki Kohei Ashikaga Seisyou Kou Nobuyuki Kagiyama Tetsuo Yamaguchi Takahiro Okumura Atsushi Mizuno Shogo Oishi Yasutaka Inuzuka Eiichi Akiyama Satoshi Suzuki Masayoshi Yamamoto Yuya Matsue
出版者: The Japanese Circulation Society
雑誌: Circulation Journal (ISSN:13469843)
巻号頁・発行日: pp.CJ-21-0269, (Released:2021-07-09)
参考文献数: 24
被引用文献数: 3

Background:Atrial fibrillation (AF) is a common arrhythmia in patients with acute heart failure (AHF). Heart rate (HR) also changes significantly over time. However, the association between changes in HR in AF patients and prognosis is uncertain.Methods and Results:We investigated the association between HR reduction in AF achieved within 48 h of admission and 60-day mortality in patients with AHF from the REALITY-AHF study. The percentage HR (%HR) reduction was calculated as (baseline HR–HR at 48 h) / baseline HR × 100. The primary endpoint was 60-day all-cause mortality. In 468 patients with confirmed AF at both admission and 48 h after admission, the median HR at these time points was 105±31 and 84±18 beats/min, respectively. The median %HR reduction was 15.4% (interquartile range 2.2–31.4%). During the 60 days of admission, 39 deaths (8.3%) were recorded, and the %HR reduction within 48 h was significantly associated with 60-day mortality in the unadjusted model (hazard ratio [HR] 0.85; 95% confidence interval [CI] 0.77–0.95; P=0.005) and after adjusting for other covariates (HR 0.81; 95% CI 0.68–0.96; P=0.016).Furthermore, the %HR reduction was associated with a significant reduction in 60-day mortality in patients with higher baseline HR.Conclusions:%HR reduction is associated with a better short-term prognosis in patients with AHF presenting with AF, particularly in those with a rapid ventricular response.

2022-12-05 01:58:57
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12 0 0 0 OA Efficacy of Low-Dose Isoproterenol Infusion for the Exclusion of a Left Atrial Appendage Thrombus in Patients With Dense Spontaneous Echo Contrast Caused by Atrial Fibrillation

著者: Tomoko Machino-Ohtsuka Kentaro Minami Hiro Yamasaki Tomofumi Nakatsukasa Naoto Kawamatsu Kimi Sato Masayoshi Yamamoto Kazushi Maruo Tomoko Ishizu Yasushi Kawakami Masaki Ieda
出版者: The Japanese Circulation Society
雑誌: Circulation Journal (ISSN:13469843)
巻号頁・発行日: pp.CJ-23-0271, (Released:2023-06-30)
参考文献数: 26

Background: In patients with atrial fibrillation (AF) and severe blood stasis in the left atrial appendage (LAA), dense spontaneous echo contrast (SEC) disturbs the distinct visualization of the LAA interior, thus making thrombus diagnosis inconclusive. We aimed to prospectively assess the efficacy and safety of a protocol for a low-dose isoproterenol (ISP) infusion to reduce SEC to exclude an LAA thrombus.Methods and Results: We enrolled 17 patients with AF and dense SEC (Grade 4 or sludge). ISP was infused with gradually increasing doses of 0.01, 0.02, and 0.03 μg/kg/min at 3-min intervals. After increasing the dose to 0.03 μg/kg/min for 3 min, or when the LAA interior was visible, the infusion was terminated. We reassessed the SEC grade, presence of an LAA thrombus, LAA function, and left ventricular ejection fraction (LVEF) within 1 min of ISP termination. Compared with baseline, ISP significantly increased LAA flow velocity, the LAA emptying fraction, LAA wall velocities, and LVEF (all P<0.01). ISP administration significantly reduced the SEC grade (median) from 4 to 1 (P<0.001). The SEC grade decreased to ≤2 in 15 (88%) patients, and the LAA thrombus was excluded. There were no adverse events.Conclusions: Low-dose ISP infusion may be effective and safe to reduce SEC and exclude an LAA thrombus by improving LAA function and LVEF.

2023-11-24 22:09:15
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9 0 0 0 OA An evaluation of a new type of High Efficiency Hybrid Gate Drive Circuit for SiC-MOSFET suitable for Automotive Power Electronics System Applications

著者: Masayoshi Yamamoto Shinya Shirai Senanayake Thilak Jun Imaoka Ryosuke Ishido Yuta Okawauchi Ken Nakahara
出版者: The Institute of Electronics, Information and Communication Engineers
雑誌: IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences (ISSN:09168508)
巻号頁・発行日: pp.2021GCI0001, (Released:2021-11-26)

In response to fast charging systems, Silicon Carbide (SiC) power semiconductor devices are of great interest of the automotive power electronics applications as the next generation of fast charging systems require high voltage batteries. For high voltage battery EVs (Electric Vehicles) over 800V, SiC power semiconductor devices are suitable for 3-phase inverters, battery chargers, and isolated DC-DC converters due to their high voltage rating and high efficiency performance. However, SiC-MOSFETs have two characteristics that interfere with high-speed switching and high efficiency performance operations for SiC MOS-FET applications in automotive power electronics systems. One characteristic is the low voltage rating of the gate-source terminal, and the other is the large internal gate-resistance of SiC MOS-FET. The purpose of this work was to evaluate a proposed hybrid gate drive circuit that could ignore the internal gate-resistance and maintain the gate-source terminal stability of the SiC-MOSFET applications. It has been found that the proposed hybrid gate drive circuit can achieve faster and lower loss switching performance than conventional gate drive circuits by using the current source gate drive characteristics. In addition, the proposed gate drive circuit can use the voltage source gate drive characteristics to protect the gate-source terminals despite the low voltage rating of the SiC MOS-FET gate-source terminals.

2022-01-14 22:14:49
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7 0 0 0 OA A current fed full bridge converter with auxiliary resonant capacitor

著者: Tomoki Yamada Yu Yonezawa Masayoshi Yamamoto
出版者: The Institute of Electronics, Information and Communication Engineers
雑誌: IEICE Electronics Express (ISSN:13492543)
巻号頁・発行日: vol.20, no.21, pp.20230351, 2023-11-10 (Released:2023-11-10)
参考文献数: 30

This letter proposes a simpler and more efficient circuit scheme than the conventional current fed full bridge converter. In the proposed circuit, an auxiliary resonant capacitor is added to the conventional circuit to eliminate the adverse effects of leakage inductance of the transformer on the circuit operation, and at the same time, soft switching is achieved. As a result, switching losses were reduced and the efficiency was improved by approximately 4.7% compared to the conventional method, which was confirmed on LTspice. First, the basic structure of the proposed circuit is shown, followed by the principle of operation. Next, the advantages and disadvantages of the proposed method are presented. Finally, we compare the proposed method with the conventional method.

2023-12-05 05:58:27
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5 0 0 0 OA An Evaluation of a New Type of High Efficiency Hybrid Gate Drive Circuit for SiC-MOSFET Suitable for Automotive Power Electronics System Applications

著者: Masayoshi YAMAMOTO Shinya SHIRAI Senanayake THILAK Jun IMAOKA Ryosuke ISHIDO Yuta OKAWAUCHI Ken NAKAHARA
出版者: The Institute of Electronics, Information and Communication Engineers
雑誌: IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences (ISSN:09168508)
巻号頁・発行日: vol.E105.A, no.5, pp.834-843, 2022-05-01 (Released:2022-05-01)
参考文献数: 51

2022-08-24 19:42:39
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4 0 0 0 OA Effect of Dipeptidyl Peptidase-4 Inhibitors on Cardiovascular Outcome and Cardiac Function in Patients With Diabetes and Heart Failure ― Insights From the Ibaraki Cardiac Assessment Study-Heart Failure (ICAS-HF) Registry ―

著者: Masayoshi Yamamoto Yoshihiro Seo Tomoko Ishizu Isao Nishi Yoshie Hamada-Harimura Tomoko Machino-Ohtsuka Kimi Sato Seika Sai Akinori Sugano Kenichi Obara Kazutaka Aonuma
出版者: 日本循環器学会
雑誌: Circulation Journal (ISSN:13469843)
巻号頁・発行日: pp.CJ-17-0240, (Released:2017-06-06)
参考文献数: 27
被引用文献数: 9

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.

2017-06-11 00:52:29
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2 0 0 0 OA Sodium Glucose Co-Transporter 2 Inhibitors Improve Renal Congestion and Left Ventricular Fibrosis in Rats With Hypertensive Heart Failure

著者: Tomofumi Nakatsukasa Tomoko Ishizu Masumi Ouchi Nobuyuki Murakoshi Kimi Sato Masayoshi Yamamoto Kunio Kawanishi Yoshihiro Seo Masaki Ieda
出版者: The Japanese Circulation Society
雑誌: Circulation Journal (ISSN:13469843)
巻号頁・発行日: vol.86, no.12, pp.2029-2039, 2022-11-25 (Released:2022-11-25)
参考文献数: 35
被引用文献数: 4

Background: Elevated central venous pressure (CVP) in heart failure causes renal congestion, which deteriorates prognosis. Sodium glucose co-transporter 2 inhibitor (SGLT2-i) improves kidney function and heart failure prognosis; however, it is unknown whether they affect renal congestion. This study investigated the effect of SGLT2-i on the kidney and left ventricle using model rats with hypertensive heart failure.Methods and Results: Eight rats were fed a 0.3% low-salt diet (n=7), and 24 rats were fed an 8% high-salt diet, and they were divided into 3 groups of untreated (n=6), SGLT2-i (canagliflozin; n=6), and loop diuretic (furosemide; n=5) groups after 11 weeks of age. At 18 weeks of age, CVP and renal intramedullary pressure (RMP) were monitored directly by catheterization. We performed contrast-enhanced ultrasonography to evaluate intrarenal perfusion. In all high-salt fed groups, systolic blood pressure was elevated (P=0.287). The left ventricular ejection fraction did not differ among high-salt groups. Although CVP decreased in both the furosemide (P=0.032) and the canagliflozin groups (P=0.030), RMP reduction (P=0.003) and preserved renal medulla perfusion were only observed in the canagliflozin group (P=0.001). Histological analysis showed less cast formation in the intrarenal tubule (P=0.032), left ventricle fibrosis (P<0.001), and myocyte thickness (P<0.001) in the canagliflozin group than in the control group.Conclusions: These results suggest that SGLT2-i causes renal decongestion and prevents left ventricular hypertrophy, fibrosis, and dysfunction

2023-07-06 19:24:19
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1 0 0 0 OA Effect of Dipeptidyl Peptidase-4 Inhibitors on Cardiovascular Outcome and Cardiac Function in Patients With Diabetes and Heart Failure ― Insights From the Ibaraki Cardiac Assessment Study-Heart Failure (ICAS-HF) Registry ―

著者: Masayoshi Yamamoto Yoshihiro Seo Tomoko Ishizu Isao Nishi Yoshie Hamada-Harimura Tomoko Machino-Ohtsuka Kimi Sato Seika Sai Akinori Sugano Kenichi Obara Kazutaka Aonuma
出版者: 日本循環器学会
雑誌: Circulation Journal (ISSN:13469843)
巻号頁・発行日: vol.81, no.11, pp.1662-1669, 2017-10-25 (Released:2017-10-25)
参考文献数: 27
被引用文献数: 9

2017-11-21 07:51:41
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