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Biomedical subjects

A T Miyamoto

Publications and source records attributed to A T Miyamoto.

At least 19 recordsLinked to original sources
PubMed1996

Transatrial atrioventricular valve testing in the beating, fully loaded heart.

A detailed technique is described to safely inspect visually the function of the atrioventricular (mitral, common atrioventricular, or tricuspid) valve in the beating, fully loaded, but not ejecting left or right ventricle. The heartbeat is reestablished while the ascending aorta is kept cross-clamped and air from the ascending aorta is vented out. The left or right ventricle is filled via a 6-mm internal diameter tube derived from the arterial return line. To allow filling of the right ventricle for tricuspid valve evaluation, the pulmonary artery is snared down in addition.

Heart Function Tests↗
PubMed1994

Immunohistochemical and pathological characteristics of dystrophic amyloid in surgically excised cardiac valves.

One hundred and thirty-six cardiac valves obtained surgically from 124 patients (aged 15-77 years) were examined. Microdeposition of amyloid was present in sclerotic or sclerocalcific lesions of aortic valves in 38 out of 75 (51%) and mitral valves in 21 out of 61 (34%). Amyloid deposition was not significantly related to the age of the patients. An antiserum raised against a low molecular weight protein extracted from amyloid-laden valvular tissues (about 20 g) reacted positively to amyloid in the cardiac valves. It did not react to amyloid deposition containing fibril proteins including light chain related amyloidosis, reactive amyloidosis, systemic senile amyloidosis, isolated atrial amyloidosis, beta-2-microglobulin related amyloidosis and beta protein related amyloidosis. Further, amyloid in the cardiac valves failed to react immunohistochemically to anti-AA, anti-AL, anti-TTR, anti-ANF, anti-beta 2M and anti-beta protein antibodies. These findings suggest that an unknown amyloid protein is involved in the damaged valves.

Adolescent↗
PubMed1993

H(+)-ATPase and transport of DOPAC, HVA, and 5-HIAA in monoamine neurons.

The effects of N-methylmaleimide (N-MtM), a vacuolar H(+)-ATPase inhibitor, were evaluated in the putamen of the cat to study the in vivo transport mechanisms of dopamine (DA), 5-hydroxytryptamine (5-HT), and their metabolites 3,4-dihydroxyphenylacetic acid (DOPAC), homovanillic acid (HVA), and 5-hydroxyindolacetic acid (5-HIAA), using the brain focal microdialysis technique combined with HPLC. The addition of N-MtM to the perfusate altered invariably the flux of the DOPAC, HVA, and 5-HIAA in a similar pattern, resulting in a decrease of the extracellular levels of such metabolites, its extent being N-MtM concentration dependent, thus indicating that the mechanism(s) of such a decrease is (are) related most likely to decreased transport from the intracellular to the extracellular space as the consequence of the inhibition of the vacuolar H(+)-ATPase of DA and 5-HT neurons by the N-MtM. Furthermore, N-MtM masked the release of DA and 5-HT produced by KCl 120 mmol/l. Indeed, N-MtM increased the extracellular levels of such transmitters to values exceeding 4 to 6 times of those produced by KCl 120 mmol/l alone, which suggests that vacuolar H(+)-ATPase is probably involved also in the retention and/or reuptake process of DA and 5-HT.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1993

Skeletal muscle-powered ventricle. Effects of size and configuration on ventricular function.

The optimal size and configuration of skeletal muscle-powered ventricles are still undetermined. This study was aimed at comparing three types of skeletal muscle-powered ventricle: (A) a small size (15 ml capacity) double-layered pump, (B) a small size (15 ml capacity) single-layered pump, and (C) a large size (40 to 60 ml capacity) single-layered pump constructed sequentially with the same untrained latissimus dorsi muscle of 12 mongrel dogs. The skeletal muscle-powered ventricle was connected to a mock circulation system, the stroke volumes against 40 to 160 mm Hg of afterload at 5 to 60 mm Hg of preload were measured, and the stroke work was computer analyzed on line. Raising the preload from 5 to 60 mm Hg increased the peak isovolumic developed pressure (A) from 91.3 +/- 11.0 to 215.6 +/- 26.1 mm Hg, (B) from 92.8 +/- 12.0 to 166.3 +/- 19.0 mm Hg, and (C) from 32.3 +/- 5.2 to 121.4 +/- 15.5 mm Hg (p < 0.05, C versus A and B). Similarly, the stroke volume (stroke work) against an afterload of 120 mm Hg increased (A) from 3.8 +/- 0.5 ml (0.22 +/- 0.04 x 10(6) ergs) to 14.5 +/- 1.1 ml (1.05 +/- 0.11 x 10(6) ergs), (B) from 4.5 +/- 0.7 ml (0.30 +/- 0.08 x 10(6) ergs) to 10.7 +/- 0.9 ml (0.63 +/- 0.08 x 10(6) ergs), and (C) from 1.8 +/- 0.5 ml (0.09 +/- 0.04 x 10(6) ergs) to 24.0 +/- 3.6 ml (1.94 +/- 0.41 x 10(6) ergs) (p < 0.05, C versus B at 5 mm Hg of preload; p < 0.05, C versus A and B at preloads > or = 30 mm Hg). At low preloads (5 to 15 mm Hg) both small pumps generated a significantly larger stroke volume (stroke work) than the large pump, whereas at high preloads (> or = 30 mm Hg) the large pump generated a significantly larger stroke volume (stroke work) than the small pumps. It is concluded that under physiologic preload, B (small single-layered pump) performs better than or at least as well as A (small double-layered pump) and C (large single-layered pump), despite being constructed with only one half of the muscle mass used for either A or C.

Animals↗
PubMed1992

Technique for replacing the ascending aorta and aortic valve with a modified Bentall's operation.

Composite graft replacement of the aortic root and valve poses the challenge of reimplanting both coronary ostia. The technique of sandwiching the freed button of aortic wall bearing the coronary artery ostium between an outer Teflon felt washerlike buttress and the inner composite graft provides a leak-proof anastomosis while reestablishing direct graft to coronary artery continuity regardless of the location of the coronary ostia or type of root pathology.

Aorta↗
PubMed1991

Skeletal muscle powered ventricle: comparison of double-layered small ventricle and single-layered large ventricle.

Canine left latissimus dorsi (LD) muscles were used to construct two kinds of skeletal muscle powered ventricles (SMPV): a double layered small size (10-17 mL) SMPV (A), and a single-layered large size (40-70 mL) SMPV (B). The same muscle was used sequentially for the construction of both SMPV. A mock circulation system was used for testing. This allowed for change of the preload (10-60 mmHg) and afterload (40-160 mmHg) independently. The peak developed pressure (PDP) and stroke volume (SV) were measured, and the stroke work (SW) was analyzed on line by a computer. The isovolumic PDP was 93.3 +/- 11.8 mmHg at 10 mmHg preload, and 157.7 +/- 20.2 mmHg at 60 mmHg for A, and 37.8 +/- 5.5 mHg and 107.8 +/- 8.5 mmHg for B. The SV and SW at 50 mmHg preload and 80 mmHg afterload were 18.30 +/- 1.25 mL and 1.06 +/- 0.10 x 10(6) erg for A, and 34.18 +/- 2.36 mL and 2.51 +/- 0.28 x 10(6) erg for B. The SV and SW at 20 mmHg preload and 160 mmHg afterload were 2.65 +/- 0.31 mL and 0.27 +/- 0.05 x 10(6) erg for A, and 1.03 +/- 0.23 mL and 0.04 +/- 0.01 x 10(6) erg for (B). The SW generated by the large single-layered SMPV is similar to that reported for the canine left ventricle but requires a high preload. The large single-layered SMPV showed a higher dependence on pre- and afterload changes than the double layered small SMPV, which generates a higher pressure even at low preloads.

Animals↗
PubMed1983

Right ventricular function during left heart bypass.

Right heart failure may occur during mechanical support of the left ventricle (LV). Right ventricular (RV) functional changes were studied in eight dogs (26.9 +/- 1.4 kg) subjected to various degrees of left heart bypass (LHBP) with a roller pump. The venous return to the right atrium was controlled with a second pump. RV function was evaluated by peak RV developed pressure, its first derivative (dp/dt), and mean RA pressure measurements. Left atrial, LV, and aortic pressure and both roller pump flows were determined. Incremental increases in LHBP flow ratio ([LHBP flow x 100] divided by venous return flow) to 60%, 90%, and 100% were associated with decrements in RV dp/dt from the control of 212 +/- 17 torr/sec to 192 +/- 16, 178 +/- 16, and 168 +/- 13 torr/sec, respectively. Biventricular bypass or total cardiopulmonary bypass with extracorporeal membrane oxygenation seems to be indicated if LHBP flow ratio greater than 90% is required to maintain adequate body perfusion. Maximal LV decompression to obtain the greatest reduction of LV myocardial oxygen consumption may not be the ideal goal during LV mechanical assistance.

Animals↗
PubMed1983

Coronary artery stenoses. Relationship between angiographic severity and impact on mean diastolic pressure gradient.

Coronary angiography provides important anatomic information about coronary artery stenoses. However, it is unclear whether specific assumptions about hemodynamic impact can be made from the angiogram. We therefore studied the relationship between angiographic severity of coronary stenoses and the mean diastolic pressure gradient measured directly at coronary bypass operation. We studied 29 stenoses selected because they were the only lesions in a given vessel, they were well seen in two angiographic views, and there was no change in clinical status of the patient between angiographic and surgical procedures. Fourteen stenoses were in the left anterior descending artery, nine were in the right coronary artery, and six were in the left circumflex artery. Correlation between mean diastolic gradient and percent stenosis was good (r = 0.78, p = 0.001) and especially so for lesions in the left anterior descending artery (r = 0.84, p = 0.001). Lesions over 90% had a wide range of gradients, while lesions less than 90% tended to have more predictable gradients. Collaterals invariably identified vessels with stenoses causing major pressure gradients. History of myocardial infarction was associated with major gradients in supplying vessels. Length of stenosis was not an important influence on gradient over a stenosis. We conclude that in some defined instances, generalizations about hemodynamic (and presumed functional) impact of stenoses can be made from the angiographic assessment, but precise assumptions are not possible.

Adult↗
PubMed1983

Post-myocardial infarction ventricular septal defect. Improved outlook.

Eight patients (mean age 63.75 years) were operated upon for post-myocardial infarction ventricular septal rupture (PMI-VSD) within 1 to 21 days of the infarction and 8 hours to 18 days of rupture. All but one were in low cardiac output syndrome necessitating intra-aortic balloon pumping; all had cardiac catheterization. The VSD was closed via a transinfarct ventriculotomy with an oversized folded double patch, the folded edge being incorporated in the ventriculotomy closure. Five patients received seven saphenous vein coronary bypass grafts. None had recurrent shunts. Six patients (anterior VSD, five; posterior VSD, one) are survivors (18 months to 2.5 years) in Class I (five) or Class II (one). Two patients died postoperatively, one (anterior VSD) of an arrhythmia and the other (posterior VSD) while on biventricular bypass support. Two survivors in whom prolonged preoperative stabilization was attempted required emergency operation before the planned waiting period of 3 weeks had elapsed, and both had postoperative multiorgan complications. Our present approach is to operate as soon as clinical and catheterization diagnosis of VSD is made.

Aged↗
PubMed1982

Effects of left heart bypass on right ventricular function.

Right ventricular function has been studied in a canine ejecting heart model in-situ with intact sympathetic innervation and constant cardiac output, during varying degrees of left heart bypass ratio ranging from nil to total left ventricular decompression. The right ventricular function deteriorates as the left heart bypass ratio increases, reaching the maximal degree of RV depression when the LV is maximally decompressed. Some practical implications for the conduction of left heart bypass are discussed.

Animals↗
PubMed1980

Pulmonary embolism in stroke: prevention by early heparinization of venous thrombosis detected by iodine-125 fibrinogen leg scans.

During an 8-month study of stroke patients, a 9% incidence of pulmonary embolism and a 1.5% incidence of thrombophlebitis was found among hemiparetic patients undergoing intensive rehabilitation after being medically stabilized. Patients were usually studied 10 days to 2 weeks after the onset of stroke. During the next 18 months, 141 subsequent patients were studied with 125I-fibrinogen uptake leg scans, disclosing a 29% incidence of deep venous thrombosis. Venograms were obtained in 28 patients; clots in 25 patients were confirmed in normal locations on the fibrinogen scan, and there was 1 false negative and 2 false positives. The subsequent 14 patients with clot were anticoagulated on the basis of the fibrinogen scan alone. Early anticoagulation of clinically silent leg thrombi prevented any pulmonary emboli.

Adult↗
PubMed1979

Efficacy of systolic vs diastolic pulsation beyond severe coronary stenosis flow.

This paper describes the superiority of systolic pulsatile selective coronary perfusion as compared to diastolic pulsatile coronary perfusion in improving flow beyond ischemia-producing coronary artery obstructions in the working heart. The practical implications for use in coronary support perfusion systems are discussed.

Animals↗
PubMed1979

Computed tomography: its potential as a predictor of functional recovery following stroke.

In a 6-month period, 40 consecutive patients with a diagnosis of cerebral infarction had computed tomography (CT) scanning. The purpose of this study was to evaluate the association between the location and size of the lesion on CT scan and the functional status of the patient on discharge and follow-up. The results of the CT scan were divided into the following major groups: deep (involving the basal ganglia, internal capsule and thalamus), superficial large and superficial small (involving the cerebral hemisphere up to and including the external capsule) and normal. At discharge, patients were divided into 2 major functional groups: group A, minimal assist to independent in transfers and ambulation; and group B, moderate to maximal assist in transfers and maximal assist in ambulation. Ten of 11 patients with small superficial lesions were in group A, and 10 of 13 patients with deep lesions were in group B. Of 10 patients with large superficial lesions, 5 were in group A and 5 in group B. All 6 patients with normal CT scans results were in group A. Thus, results of CT scanning appear to be associated with degree of functional recovery.

Activities of Daily Living↗