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Biomedical subjects

Y Yokote

Publications and source records attributed to Y Yokote.

At least 73 records · Page 4Linked to original sources
PubMed1990

Early diagnosis and surgical intervention of acute aortic dissection by transesophageal color flow mapping.

To determine whether transesophageal color Doppler echocardiography (TEE) is useful for the early diagnosis and surgical intervention in acute aortic dissection, 57 serial patients with acute aortic dissection were examined. These patients were evaluated by TEE with either the single-plane probe (39 patients) or the biplanar probe (18 patients) just after admission. The intimal flap was detected in all patients, and there were 18 patients with type A dissection and 39 patients with type B dissection. The entry was visualized in 83% of type A dissection cases and in 90% of type B dissection cases. In two of 18 patients examined with the biplanar probe technique, the entry was detected in the longitudinal view only. Emergency operations were performed in 18 patients with type A dissection and in 10 patients with ruptured type B dissection. Twenty-nine of 39 patients with type B dissection were treated conservatively. The operative mortality rate of patients with type A dissection was 22%, and that of patients with ruptured type B dissection was 60%. The major advantage of TEE is its ease of application at the bedside or in the operating room, which allows immediate and accurate diagnosis of acute aortic dissection for emergency surgical intervention. Biplanar TEE provides additional acoustic windows, ease of spatial orientation, and more accurate visualization of entry. TEE is a useful and powerful diagnostic tool for acute aortic dissection, and by using this method, one may achieve a more rapid and aggressive surgical approach for patients with acute aortic dissection.

Acute Disease↗
PubMed1989

[Responses of aortocoronary bypass graft flow to nitroglycerin, nifedipine and exercise test: a two-dimensional color Doppler echocardiographic study].

To assess the effects of coronary vasodilators and exercise on the blood flow dynamics of aortocoronary bypass grafts (ACBG), two-dimensional Doppler echocardiography was performed in 43 consecutive patients with ACBG of the left coronary artery. Doppler velocity signals of 14 internal mammary artery grafts (IMAG) and three saphenous vein grafts (SVG) were imaged in 15 patients using 5MHZ and 7.5MHZ convex-linear Doppler flow probes. Cross-sectional blood flow velocities and graft internal dimensions were continuously measured before and after the sublingual administration of nitroglycerin (0.3 mg) and nifedipine (20 mg), during isometric handgrip and bicycle ergometer exercise tests. 1. Regurgitant flow in isometric contraction time to early systole was observed in 14 of the 15 patients. Pulsatile diastolic blood flow with mean velocity of 14 +/- 6 cm/sec and volume of 49 +/- 25 ml/min was significantly higher than those in systole (7 +/- 7 cm/sec and 8 +/- 7 ml/min) as observed in IMAG and SVG. IMAG showed smaller vessel dimensions, higher flow velocities and lower flow volumes compared with those of SVG. 2. Nitroglycerin and nifedipine increased blood flow volumes (75 +/- 12%, 79 +/- 11%) and velocities (29 +/- 8%, 28 +/- 8%) due to dilatation of graft vessels (18 +/- 3%, 19 +/- 3%). Nifedipine, in contrast to nitroglycerin, induced sustained increases in graft flows. 3. Isometric handgrip and ergometer bicycle exercise tests increased blood flow volumes (34 +/- 9%, 61 +/- 14%) and velocities (31 +/- 11%, 42 +/- 12%) with elevation of double products (22 +/- 14%, 37 +/- 26%). Ergometer bicycle exercise induced similar responses in systole and diastole, whereas isometric handgrip test induced higher ratios of graft flow volume in systole (67 +/- 25%) compared to those in diastole (28 +/- 9%). In conclusion, two-dimensional color Doppler echocardiography is a promising means for the quantitative analysis of blood flow dynamics, assessments of the variable effects of coronary vasodilators and the physiological responses to exercise tests for the aortocoronary bypass graft flow in the early postoperative state.

Aged↗
PubMed1989

[Visualization of internal mammary artery bypass graft flow using a linear color flow mapping system with a convex type transducer].

To evaluate noninvasively the patency of aortocoronary bypass grafts using the left internal mammary artery (LIMAG), color flow mapping Doppler echocardiography was performed in 23 consecutive patients. There were 22 males and one female. The average number of involved coronary arteries per patient was 2.5 +/- 0.6. The average number of bypassed graft anastomoses was 2.7 +/- 0.9, including 22 isolated LIMAG and one sequential LIMAG. The color flow mapping system used was a linear type 2-D Doppler system (Aloka SSD350) with a convex type transducer. Clear color flow visualization of LIMAG flow was obtained in nine of the 23 patients (39%) studied, with an average peak diastolic velocity of 22.5 +/- 8.7 cm/sec and an average systolic peak velocity of 12.6 +/- 5.7 cm/sec. The coronary angiograms of eight patients were obtained within two weeks after the echocardiographic examinations which demonstrated good graft patency in all LIMAG. Color flow visualization of LIMAG was obtained in four of the eight patients (50%). Although the detection rate was limited, LIMAG flow could be clearly visualized in nearly half the cases studied with stable reproducibility from the transcutaneous echo window. Thus, this technique can be a useful diagnostic means for long-term follow-up of LIMAG and for investigating coronary circulation in the future.

Aged↗
PubMed1988

Right ventricular aneurysm due to congenital muscular defect in an adult.

A large right ventricular aneurysm was detected by an echocardiographic examination in a 50-year-old woman presenting with weakness, collapse and hypotension. At surgery, another smaller aneurysm, arising from the anterior infundibulum of the right ventricle, was found in addition to the large one. Both were resected. Histological studies on the resected specimen revealed that much of the myocardium was replaced by adipose tissue. As far as we know this is the first reported case in Japan in which two congenital aneurysms arose from the right ventricle as a result of muscular defect.

Adipose Tissue↗
PubMed1988

Premature opening of the pulmonary valve in endomyocardial fibrosis.

Two-dimensional and Doppler echocardiographic findings in a 67-year-old man with endomyocardial fibrosis (EMF) are described. The two-dimensional echocardiogram showed typical features of EMF, right ventricular endomyocardial calcification, a thickened right ventricular wall, obliteration of the apex of the right ventricle and marked dilatation of the right atrium. In addition, premature opening of the pulmonary valve was observed during late diastole. The Doppler echocardiogram revealed forward flow from the right ventricle to the pulmonary artery, indicating the conduit state of the right ventricle. These findings were supported by cardiac catheterization and autopsy. Thus, two-dimensional and Doppler echocardiography are useful not only in making the diagnosis, but also in understanding the hemodynamic condition in EMF.

Aged↗
PubMed1988

[Left ventricular diastolic reserve during acute pressure loading in hypertrophic cardiomyopathy and dilated cardiomyopathy].

To evaluate left ventricular diastolic reserve during acute pressure loading, changes in mitral flow velocity patterns before and after the elevation of blood pressure were analyzed by pulsed Doppler echocardiography in 11 cases of hypertrophic cardiomyopathy (HCM), nine cases of dilated cardiomyopathy (DCM), and 11 control subjects. Systolic blood pressure was elevated 25% above basal values by methoxamine infusion (0.01 mg/kg/min). Before and after methoxamine, left ventricular dimension and mitral flow velocity pattern were obtained by M-mode and pulsed Doppler echocardiography, respectively. The peak velocity in the rapid filling and atrial contraction phases and time-velocity integrals were measured from the flow pattern. After methoxamine, left ventricular diastolic dimension was significantly increased in all groups, from 43.8 +/- 4.7 mm to 47.4 +/- 4.9 mm in the control subjects, from 43.7 +/- 6.3 mm to 47.2 +/- 6.0 mm in HCM, and from 57.9 +/- 6.4 mm to 60.6 +/- 5.9 mm in DCM. Left ventricular systolic dimension was significantly increased from 48.6 +/- 8.4 mm to 52.8 +/- 8.3 mm in DCM, but not in the control subjects or HCM. The peak velocity in the rapid filling phase was significantly increased from 60 +/- 16 cm/sec to 69 +/- 14 cm/sec in the control subjects and tended to be increased from 44 +/- 13 cm/sec to 52 +/- 12 cm/sec in HCM. The extent of this increase tended to be less in HCM. However, the peak velocity in the rapid filling phase tended to decrease in DCM. There were no consistent trends of changes in the peak velocity in the atrial contraction phase in any groups. The mitral velocity integral increased from 502 Hz-sec to 621 Hz-sec in the controls and from 525 Hz-sec to 613 Hz-sec in HCM, but it did not increase in DCM. These findings suggest that there is impaired diastolic reserve during acute pressure loading in HCM and DCM and that the diastolic disturbance might be reflected in the early diastolic phase, rather than in the late diastolic phase.

Adult↗
PubMed1987

Immediate and early postoperative evaluation of results of cardiac surgery by transesophageal two-dimensional Doppler echocardiography.

In cardiac surgery significant residual lesions increase postoperative morbidity and mortality. Although intraoperative epicardial real-time two-dimensional Doppler echocardiography (two-dimensional Doppler) is an accurate and efficient technique for assessing the presence and severity of a residual lesion, it requires placement of a transducer in the operating field and consequent obstruction of the operative procedure. Transesophageal two-dimensional Doppler echocardiography (transesophageal two-dimensional Doppler), which can be applied intraoperatively and postoperatively without such problems, was performed in 35 patients during cardiac surgery (12 patients) and/or at an intensive care unit within 6 hr after cardiac surgery (30 patients). In those with constrictive pericarditis, an extensive pericardiectomy was performed with effective monitoring by intraoperative transesophageal two-dimensional Doppler. Abnormal posterior wall motion was observed in the case of left ventricular rupture (type III) after mitral valve replacement 3 hr before clinical manifestation. After prosthetic valve replacement (18 St. Jude Medical valves, one Carpentier-Edwards valve, one Björk-Shiley valve), no perivalvular leakage was detected, but minor physiologic transvalvular leakage was noticed in 11 patients with St. Jude Medical valves. In two patients with congenital heart disease, a small residual shunt was detected. In a patient in which a composite valve graft with direct coronary artery reattachment (Bentall's operation) was performed, reattachment was confirmed to be satisfactory. In conclusion, intraoperative and early postoperative monitoring of cardiac function by transesophageal two-dimensional Doppler echocardiography can improve the results of cardiovascular surgery by providing accurate information on cardiovascular structure and blood flow dynamics.

Adult↗
PubMed1986

Recovery of tryptophan from 25-minute acid hydrolysates of protein.

It was found that thioglycolic acid prevents destruction of tryptophan during rapid hydrolysis of protein with a trifluoroacetic acid/HCl mixture (1:2, v/v) at 166 degrees C for 25 or 50 min. The addition of 5% (v/v) thioglycolic acid gave the maximum tryptophan recovery (88.3%) for a 25-min hydrolysate of lysozyme. Tryptophan recoveries varied slightly among three different proteins; 88% for lysozyme, 73% for alpha-chymotrypsinogen A, and 85% for apomyoglobin. However, when extrapolated to zero time, the values were close to one another: 94, 87, and 88%, respectively. The addition of thioglycolic acid was also advantageous for recovering amino acids other than tryptophan. Particularly, yields of carboxymethylcysteine and methionine were greatly improved. This modified rapid hydrolysis method gave satisfactory results without the need for separate analyses of tryptophan and cysteine, provided proteins were reduced and carboxymethylated prior to hydrolysis.

Acids↗