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Toshikazu Yagi

Publications and source records attributed to Toshikazu Yagi.

11 recordsLinked to original sources
PubMed2006

Coronary flow velocity pattern assessed noninvasively by transthoracic color Doppler echocardiography serves as a predictor of adverse cardiac events and left ventricular remodeling in patients with acute myocardial infarction.

BACKGROUND: Quantitative assessment of microvascular injury is possible in patients with reperfused anterior myocardial infarction by invasive method. Coronary flow velocity patterns can also be assessed by transthoracic color Doppler echocardiography (TTCDE). OBJECTIVES: The purpose of this study was to determine whether the coronary flow velocity pattern assessed by TTCDE serves as a predictor of adverse cardiac events and left ventricular remodeling. METHODS: The study population consisted of 64 consecutive patients. We could analyze coronary flow velocity patterns by TTCDE in 59 of 64 patients (92%) after coronary intervention. The patients were followed up for the occurrence of complications and underwent serial measurement of left ventricular volumes. RESULTS: In patients with a short deceleration time of diastolic flow velocity, the frequency of adverse cardiac events and left ventricular remodeling was higher. CONCLUSION: It is possible to predict clinical outcome by assessing coronary flow velocity pattern by TTCDE.

Blood Flow Velocity↗
PubMed2006

Left atrial volume in normal Japanese adults.

BACKGROUND: Two-dimensional (D) echocardiography-derived left atrial (LA) volume has been shown to provide a more accurate assessment of LA size than the M-mode LA dimension. Our objective was to provide reference ranges of LA volume in healthy Japanese adults. METHODS AND RESULTS: The study subjects consisted of 105 Japanese adults, with a mean age of 39+/-13 years (range 20-63 years old). All subjects had normal ejection fraction (>55%), no wall motion abnormalities, normal diastolic function, no valvular disease, and normal sinus rhythm. The maximum LA volume, at left ventricular end-systole just before the opening of the mitral valve, was measured by using the bi-apical (4- and 2-chamber views) Simpson's rule. Both the absolute LA volume and the volume corrected by body surface area (LA volume index) were obtained. The LA volume ranged from 21 to 53 ml (mean 37+/-8 ml) and the LA volume index ranged from 13 to 30 ml/m(2) (mean 22+/-4 ml/m(2)). The mean LA volume index + 2SDs was 30 ml/m(2). CONCLUSIONS: Recognition of the upper limits of LA volume in normal Japanese subjects is of particular clinical relevance because it offers the opportunity of pathological LA remodeling diagnosis.

Adult↗
PubMed2004

Left atrial volume and the risk of paroxysmal atrial fibrillation in patients with hypertrophic cardiomyopathy.

Paroxysmal atrial fibrillation (PAF) is a common complication of patients with hypertrophic cardiomyopathy, often leading to acute or progressive heart failure and cerebral infarction. We assessed the echocardiographic data of 141 consecutive patients with hypertrophic cardiomyopathy, with and without PAF. In all, 31 patients (22%) had a history of PAF with spontaneous conversion to in sinus rhythm. Left atrial volume and left atrial volume indexed to body surface area were significantly increased for patients with PAF compared with those without PAF. Maximum left atrial volume was the most sensitive and specific parameter for the occurrence of PAF in patients with hypertrophic cardiomyopathy.

Atrial Fibrillation↗
PubMed2003

Single-beat determination of Doppler-derived aortic flow measurement in patients with atrial fibrillation.

The clinical assessment of left ventricular systolic function in patients with atrial fibrillation is unreliable and difficult because of beat-to-beat variation. We initially evaluated an index that is on the basis of the ratio of preceding R-R (RR1) to pre-preceding R-R (RR2) intervals (RR1/RR2) for the measurement of Doppler aortic flow (peak flow velocity [Vp] and time-velocity integral [TVI] proportional to stroke volume) in 20 patients (aged 65 +/- 9.6 years) with atrial fibrillation. We obtained each parameter for >13 cardiac cycles, and the relationship between each parameter at a given cardiac beat and the RR1/RR2 ratio were evaluated by linear regression analysis. The value of each parameter at RR1/RR2 = 1 was calculated from the equation of linear regression line and compared with measured average value over all cardiac cycles. Both parameters showed a significant positive correlation with the RR1/RR2 ratio (Vp, r = 0.98, y = 1.01x + 0.61; TVI, r = 0.99, y = 1.01x + 0.26). The calculated value of each parameter at RR1/RR2 = 1 was quite similar to the average value (Vp, 97.4 +/- 30.8 vs 95.7 +/- 29.8 cm/s; TVI, 17.7 +/- 6.8 vs 17.3 +/- 6.7 cm, respectively). In the additional 20 patients (aged 77.4 +/- 15.2 years), Doppler aortic flow parameters of a single beat with identical RR1 and RR2 intervals were compared with measured average value over all cardiac cycles and showed similar results (Vp, r = 0.99, y = 0.99x + 3.4, P <.0001, bias -0.5 cm/s; TVI, r = 0.99, y = 0.92x + 1.5, P <.0001, bias 0.1 cm). In conclusion, the Doppler aortic flow at RR1/RR2 = 1 allows the left ventricular systolic parameters to be accurately evaluated during atrial fibrillation and obviates the less reliable process of averaging multiple irregular beats.

Aged↗
PubMed2003

Noninvasive assessment of flow velocity and flow velocity reserve in the right gastroepiploic artery graft by transcutaneous Doppler echocardiography: comparison with an invasive technique.

BACKGROUND: The measurement of flow velocity (FV) in coronary artery bypass grafts using a Doppler guidewire has provided useful clinical and physiologic information. The recently developed transcutaneous Doppler echocardiography is a noninvasive technique to measure FV and FV reserve (FVR) in the right gastroepiploic artery (GEA) graft. The purpose of this study was to evaluate whether transcutaneous Doppler echocardiography accurately measures FV and FVR in the right GEA graft in a clinical setting. METHODS: In 33 patients who underwent graft angiography for the assessment of the right GEA graft, FV in the right GEA graft was measured by transcutaneous Doppler echocardiography under the guidance of color flow Doppler imaging at the time of examination using a Doppler guidewire. FV in the midportion of the right GEA graft was measured at baseline and during hyperemic conditions using both transcutaneous Doppler echocardiography and a Doppler guidewire. RESULTS: There were excellent correlations between the value of FV obtained by transcutaneous Doppler echocardiography and those obtained with the Doppler guidewire (averaged peak velocity: y = 0.95 x + 1.46, r = 0.98, standard error of the estimate [SEE] = 2.94 cm/s; averaged systolic peak velocity: y = 0.94 x + 1.18, r = 0.97, SEE = 3.15 cm/s; diastolic peak velocity: y = 0.97 x + 1.62, r = 0.98, SEE = 4.40 cm/s; averaged diastolic peak velocity: y = 0.95 x + 1.75, r = 0.98, SEE = 3.60 cm/s). The FVR as determined by transcutaneous Doppler echocardiography showed a good correlation with that determined using the Doppler guidewire method (y = 0.90 x + 0.21, r = 0.92, SEE = 0.31). CONCLUSIONS: Transcutaneous Doppler echocardiography proved to be an accurate noninvasive method to measure FV and FVR in the right GEA graft.

Aged↗
PubMed2003

Automated quantification of left ventricular function by the automated contour tracking method.

The automated contour tracking (ACT) method has been developed for the automated measurement of area volume using the energy minimization method without tracing a region of interest. The purpose of this study was to compare the ACT method and left ventriculography (LVG) for the measurement of left ventricular (LV) function in the clinical setting. An apical four-chamber view was visualized by two-dimensional echocardiography and recorded for off-line analysis in 14 patients with high-quality images who underwent LVG. The ACT method automatically traces the endocardial border from the recorded images and calculates LV volumes (end-diastole and end-systole) and ejection fraction (EF). Both ACT and LVG were compared by linear regression analysis for the measurement of EF. EF determined by the ACT method agreed well with that by LVG (r = 0.96, y = 0.94x + 4.6, standard error of the estimate = 3.9%). The mean difference between the ACT and LVG was -1.4%+/- 7.3%. In conclusion, the ACT method is reliable for noninvasive estimation of EF in high-quality images. This suggests that this new technique may be useful in the automated quantification of LV function.

Adult↗
PubMed2003

Membrane barrier of a porcine hepatocyte bioartificial liver.

Pores in the membrane of a bioartificial liver (BAL) allow it to function as a semipermeable barrier between its contents (i.e., liver cells) and components of the recipient's immune system. This study is designed to assess the influence of pore size on immune response to a BAL containing porcine hepatocytes. Sixteen healthy dogs were divided into four groups (four dogs per group) based on pore size of the BAL membrane and level of exposure to porcine hepatocytes. Group 1 dogs were administered porcine hepatocytes by intraperitoneal injection and served as positive controls. Group 2 dogs were exposed to porcine hepatocytes in a large-pore (200-nm) BAL, and group 3 dogs were exposed to porcine hepatocytes in a small-pore (10-nm) BAL. Group 4 dogs were exposed to a no-cell (unloaded) BAL and served as negative controls. Intraperitoneal injection of hepatocytes or 3 hours of BAL hemoperfusion was performed day 0 and 3 weeks later on day 21. Biochemical, humoral, and cellular measures of immune response were collected until day 44. The initiation of BAL hemoperfusion was associated with a rapid decline in CH(50) levels of complement and transient neutropenia and thrombocytopenia during all BAL exposures. Xenoreactive antibody response to BAL was increased by use of membranes with large pores and secondary exposures. Skin testing on day 42 showed a delayed-type hypersensitivity response to porcine hepatocytes that also correlated with level of previous antigen exposure. BAL treatment was associated with both immediate and elicited immunologic responses. The immediate response was transient and not influenced by membrane pore size, whereas elicited responses were influenced by pore size of the BAL during previous exposures.

Albuminuria↗
PubMed2003

Apoptotic cell death and function of cryopreserved porcine hepatocytes in a bioartificial liver.

We have previously shown that cryopreservation leads to increased apoptotic death of porcine hepatocytes intended for use in a bioartificial liver (BAL). This study was designed to determine if a broad-spectrum caspase inhibitor, IDN-1965, reduced apoptosis and increased function of cryopreserved porcine hepatocytes in static culture or in a BAL. Porcine hepatocytes were studied immediately after isolation and after 2 weeks of cryopreservation in liquid nitrogen using medium supplemented with 25 micromol/L IDN-1965 or vehicle. Both apoptotic and necrotic cells were observed in cultures of fresh and cryopreserved hepatocytes, but the percentage of apoptotic cells increased after cryopreservation. Cryopreservation in IDN-1965 improved hepatocyte viability and reduced apoptotic cell death determined by TUNEL assay. Cryopreservation of hepatocytes in IDN-1965 was also associated with reduced caspase 3-like activity, decreased release of cytochrome c from mitochondria, and a slower decline in mitochondrial membrane potential after thawing. These markers of apoptosis were lowest after cryopreservation when IDN-1965 was added to both the culture and cryopreservation medium. Functional markers of hepatocyte activity (albumin production, diazepam metabolism, urea production) were also increased after cryopreservation and culture of hepatocytes in medium supplemented with 25 micromol/L IDN-1965. Cryopreservation of porcine hepatocytes in the presence of caspase inhibitor IDN-1965 was associated with reduced apoptosis and improved function of porcine hepatocytes in both static culture and a perfused BAL. These data demonstrate that inhibition of apoptosis also preserves cell function.

Albumins↗
PubMed2003

[Assessment of the clinical feasibility of OptiGo for hand-held echocardiography].

OBJECTIVES: Hand-held ultrasound devices are becoming available for clinical examination, but the accuracy and precision of such devices are unclear. This study compared the accuracy of a hand-held echo device to a standard echo system. METHODS: Twenty-two patients were examined with the OptiGo (Phillips Medial Systems) hand-held ultrasound system with a 2.5 MHz transducer and SONOS 5500 (Phillips Medial Systems) standard ultrasound system with a 2 to 4 MHz wideband transducer. Patients with cardiac arrhythmia and tachycardia were excluded. Image quality, chamber size (left ventricle, left atrium), global and regional left ventricular function, valve morphology and severity of valve regurgitation were assessed. RESULTS: There was good agreement between the two imaging devices for image quality (77.3%), left ventricular ejection fraction (90.5%), regional wall motion score (> 90%), valve morphology (> 90%), severity of valve regurgitation (> 81.0%) and there was good correlation and agreement for left ventricular and left atrial size. CONCLUSIONS: Although the OptiGo has limitations, the hand-held examination appropriately estimates global and regional left ventricular function, valve morphology, valve regurgitation and chamber size.

Adult↗
PubMed2003

[Validation of a new hand-carried ultrasound device equipped with directional color power Doppler and continuous wave Doppler].

OBJECTIVES: This study evaluated the accuracy of the directional color power Doppler (DCPD) and continuous wave Doppler (CWD) methods incorporated in the new hand-carried SonoSite 180PLUS ultrasound device. METHODS: The hand-held ultrasound system with 2.5 MHz transducer and SONOS 5500 was used as a standard ultrasound system with a 2 to 4 MHz wideband transducer. The experimental study used a Doppler wire phantom to evaluate the influence of target wire speed and angle of transducer on DCPD imaging. The clinical study included 48 consecutive patients. DCPD assessment of valvular regurgitation measured the distances of DCPD signals of mitral, aortic and tricuspid valve regurgitation using the apical four-chamber view for comparison with standard echocardiography. CWD assessment measured the peak velocities of the aortic flow and tricuspid valve regurgitant flow for comparison with standard echocardiography. RESULTS: In the experimental study, DCPD signals were not influenced by target wire speed changes and transducer incident angles. In the clinical study, agreements for mitral, aortic and tricuspid regurgitation between the two methods were 89.6%, 81.8% and 78.7%, respectively. The distances of DCPD valve regurgitant signals by the hand-carried ultrasound device showed good correlation (mitral regurgitation: y = 0.84x + 0.55; r = 0.93, aortic regurgitation: y = 0.95x + 0.27; r = 0.94, tricuspid regurgitation: y = 0.86x + 0.61; r = 0.90) with those by standard echocardiography. Evaluation of CWD velocity measurements showed good agreement for the lower flow velocities (< 2.0 m/sec). However, underestimation occurred for the high flow velocities (> 2.0 m/sec) compared with those by standard echocardiography (aortic flow: y = 0.80x + 0.11; r = 0.95, tricuspid regurgitation: y = 1.00x - 0.23; r = 0.90). CONCLUSIONS: The new hand-carried ultrasound device (SonoSite 180PLUS equipped with DCPD and CWD) is clinically useful for evaluating valvular regurgitations and flow velocities. Further studies are needed to determine the mechanism of the underestimation of high flow velocities by CWD.

Aortic Valve Insufficiency↗