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Biomedical subjects

K Hirosawa

Publications and source records attributed to K Hirosawa.

At least 73 records · Page 4Linked to original sources
PubMed1988

[Utility of digital perfusion images of the lung in mitral stenosis: the pathophysiological significance of the distribution of pulmonary perfusion].

The relationship between pulmonary hemodynamics (cardiac index; CI and the mean pulmonary artery wedge pressure; mPw) and the redistribution of pulmonary perfusion were studied in 300 patients with mitral stenosis using computerized Tc99m-MAA perfusion images (digital perfusion images: DPI), which consisted of isocount areas. Various types of DPI were obtained and were classified in six grades according to patterns of 100-70% of the isocount area in the right anterior DPI, i.e. grade-0 (normal), grade-1 (increased perfusion in the upper zone), grade-2 (uniform distribution), grade-3 (disappearance of the basal hyperperfusion area), grade-4 (apical hyperperfusion area) and grade-5 (decrease of perfusion at the lower zone). The mPw was thought to be one of the factors determining distribution. Thus, it was not adequate to estimate the mPw from DPI. In patients with the mPw less than 20 mmHg, an increase in perfusion at the upper zone and disappearance of the basal hyperperfusion might be noted, however, the mPw more than 20 mmHg was necessary to cause an apical hyperperfusion area. The predictive values of grades 0 and 1 for the mPw less than 20 mmHg were 70% (54/77) and those of grades 4 and 5 for the mPw less than 20 mmHg and the mPw less than 25 mmHg were 86% (110/128) and 56% (71/128), respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Humans↗
PubMed1988

Abnormal breathing patterns in patients with mitral stenosis: a possible compensatory role.

The breathing patterns of 37 patients with mitral stenosis were investigated in standing position by Konno-Mead analysis. Hemodynamic parameters were measured by cardiac catheterization, pulmonary function variables by pulmonary function testings and distribution of pulmonary perfusion by Tc-99m-MAA scintigraphy. Seventeen patients displayed rib cage dominant breathing patterns, and 6 patients displayed paradoxical breathing patterns, whereas 14 patients displayed normal breathing patterns. None of these patients exhibited an abdomen dominant breathing pattern. The patients with abnormal breathing patterns (rib cage dominant or paradoxical) displayed significantly higher values of pulmonary arterial pressure (p less than 0.01), capillary wedge pressure (p less than 0.01), total pulmonary vascular resistance (p less than 0.01) and mitral valve gradient (p less than 0.05) as well as smaller mitral valve area (p less than 0.05) and lower values of both in PaO2 (p less than 0.05) and diffusing capacity (p less than 0.05) than patients with normal breathing patterns. Abnormal distribution of pulmonary perfusion with hyperperfusion in the upper zone of the lung were found to be associated with the abnormal breathing patterns. Since rib cage dominant and paradoxical breathing patterns are known to increase ventilation in the upper zone of the lung, these abnormal breathing patterns may represent a compensatory mechanism serving to match ventilation and perfusion.

Adult↗
PubMed1987

Endomyocardial biopsy approach to patients with ventricular tachycardia with special reference to arrhythmogenic right ventricular dysplasia.

Right ventricular endomyocardial biopsies were performed in patients with repetitive ventricular tachycardia (VT; 8 patients) or ventricular premature beats (1 patient) which showed left bundle branch block morphology in electrocardiograms. These 9 male patients ranging in age from 21-55 years (mean 37.7 years) revealed enlargement and/or asynergy of the right ventricle in the ventriculogram. Randomly selected biopsied patients with dilated cardiomyopathy (DCM; 18 patients) and chronic right ventricular overloading (14 patients) who did not show the above-described arrhythmias served as controls. A histopathological analysis revealed advanced myocardial interstitial fibrosis associated with an increase in fatty tissue in 8 of the 9 patients (89%). Moreover, advanced hypertrophy of myocytes (grade 2 or more of our criteria), disarrangement of muscle bundles and endocardial thickening were prominent with incidences of 75%, 75% and 78%, respectively. Incidence of all findings was more pronounced in the ARVD group. Suggestiveness of post-myocarditic change in the biopsied specimen was high in 1 patient, showing a lower incidence (12%) than the DCM group (17%). From these results, we can conclude that different etiological factors may be the bases of these pathological changes. We believe that the presence of a large amount of fatty tissue within the myocardial tissue is an important element in the etiology of ventricular arrhythmias as it has also been recognized in patients with non-ARVD idiopathic ventricular tachycardia in our biopsy series.

Adult↗
PubMed1987

Current status of prehospital care of patients with acute myocardial infarction in Tokyo: analysis of 3-year experience with coronary care unit network.

To clarify the current status of prehospital care of patients with acute myocardial infarction (AMI) in the Tokyo metropolitan area, the availability of the coronary care unit (CCU) network during the past 3 years (January 1982 through December 1984) was analyzed, examining: final diagnosis, circumstances at the onset of AMI, course of transportation to CCU, time elapsed before admission, severity of AMI, and prognosis of patients. Of 6,939 patients admitted to CCU by means of the CCU network, 2,408 patients (34.7%) had AMI. The patient's decision time was, on the average, 12 hr 3 min, longer when the course of transportation to CCU was more complicated. The fatality for AMI was 17.2%. Causes of death were pump failure in 52.8%, arrhythmias in 62.8% and mechanical failure such as cardiac rupture in 8.5%. Patients with complicated AMI were admitted earlier and had a higher fatality than those without complications. Thus, community oriented programs are required to more fully inform the population at risk of AMI to shorten the patient's decision time, and more effective means to treat patients with pump failure and to prevent the development of pump failure need to be established.

Aged↗
PubMed1987

Structure and physiology of developing neuromuscular synapses in culture.

The structure and function of developing neuromuscular synapses in culture have been investigated. We used neuromuscular junctions formed by coculturing dissociated muscle cells and dissociated neurons obtained from Xenopus embryos. After recording nerve-evoked endplate potentials (e.p.p.s) and spontaneously occurring miniature endplate potentials (m.e.p.p.s) from a given junction, the same specimen was investigated for electron-microscopic histology. We surveyed almost the total area of the junctional region by making serial sections. Even in preparations cocultured for only a short time (4-11 hr), both e.p.p.s and m.e.p.p.s could be obtained. The junctional region of these early synapses revealed a simple structure. The presynaptic terminals contained smooth-surfaced clear vesicles, but there were no presynaptic specializations such as active zones. The width of the synaptic cleft was variable, with predominance of narrow regions (10-30 nm), and there was no basal lamina inside the cleft. When the coculture time was 1 d or longer, the junctional area started to show structural features resembling a mature neuromuscular synapse. In the presynaptic terminal there were active zones, consisting of the presynaptic density and an accumulation of vesicles near the density. In many junctions, the postsynaptic membrane showed densities and thickenings, with a widened synaptic cleft, that contained basal lamina. It is known that growth cones, prior to making neuromuscular junctions, can release the transmitter substance with a very long latency if stimulated repetitively. In contrast, e.p.p.s with short latencies can be evoked by single stimuli soon after the growth cones attach to muscle cells. However, our data did not reveal any structural changes to account for such functional changes.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1987

[Severity of aortic stenosis assessed by Doppler techniques].

Continuous wave (CW) Doppler ultrasound has facilitated accurate estimates of pressure gradient (PG) across a stenotic valve. However, the severity of stenosis cannot be assessed using PG alone because it is dependent on actual flow across the valve. In this study, Doppler techniques were used to predict PG and aortic valve areas (AVA) in adults with aortic stenosis (AS). Fifty-four adult patients undergoing cardiac catheterization for suspected AS were prospectively evaluated. There were 28 men and 26 women, who ranged in age from 25 to 68 years with a mean of 56 years. These Doppler ultrasound studies were performed using a 2 MHz transducer and an Aloka SSD-730. With CW Doppler ultrasound, the highest velocities of the aortic jet were recorded from an apical approach. Left ventricular outflow flows were recorded about 1.0-1.5 cm below the aortic annulus using high PRF. Doppler waveforms were analyzed for the AT/ET (AT: acceleration time, ET: ejection time), and Doppler PG was calculated from the maximum velocity (V) of the aortic jet based on a modified Bernoulli equation (PG = 4V2), and aortic valve area was obtained using the continuity equation-(AVA = left ventricular outflow tract stroke volume divided by AS jet velocity integral). These data were compared with hemodynamic data obtained from cardiac catheterization. The following results were obtained: 1. In eight patients with substantial aortic regurgitation, whose maximum catheter PG were from 20 to 45 mmHg, the AT/ET was less than 0.30. The ratio of AT/ET correlated with the peak velocity of the aortic jet (r = 0.88) and the maximum PG (r = 0.87) obtained from cardiac catheterization. 2. In 46 patients with AS, the maximum PG by CW Doppler showed an excellent correlation with maximum catheterization PG (r = 0.97, SEE 6 mmHg), and the mean PG as calculated by the two techniques also disclosed a good correlation (r = 0.97, SEE 5.4 mmHg).(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗
PubMed1987

[Diagnosis of tricuspid stenosis by two-dimensional and pulsed Doppler echocardiography].

This study verified the usefulness of two-dimensional (2-D) and pulsed Doppler echocardiography (PDE) in the diagnosis of tricuspid stenosis (TS), and estimated the diastolic pressure gradient (PG) across the tricuspid valve (TV). Fifty-two patients with rheumatic mitral stenosis showing a decreased EF slope of the TV less than 40 mm/sec were studied. All patients underwent cardiac catheterization, and the mean diastolic pressure gradients (PG) across the TV were calculated with simultaneous recordings of right atrial and ventricular pressures. Based on surgical findings, all patients were categorized as the TS group consisting of 10 patients with TS (mean PG less than or equal to 5.0 mmHg; seven patients, greater than 5.0 mmHg; three patients), and the non-TS group consisting of 42 patients without TS. In three patients with PG exceeding 5 mmHg, the TV disclosed typical commissural fusions between the leaflets. 1. 2-D echocardiography The diagnosis of TS was made by recording diastolic doming and thickening of the TV in the parasternal long-axis and apical 4-chamber views. Among the 52 patients, 2-DE detected stenosis in all 10 patients with TS, for a sensitivity of 100%, while excluding TS in 40 of 42 patients without TS for a specificity of 95%. 2. Pulsed Doppler echocardiography The transtricuspid flow velocity in diastole was recorded from the apical window.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1987

Natural history of atrial fibrillation.

The clinical significance of atrial fibrillation was analyzed in cases with chronic or acute heart disease and its significance at the acute and chronic stages of the disease was investigated in various disease groups. The types of disease, number of patients, and incidence of atrial fibrillation were: atrial septal defect (92, 14.1%), mitral valve disease (128, 79.7%), nonrheumatic valvular disease (32, 56.2%), aortic regurgitation (71, 2.8%), aortic stenosis (10, 10.0%), hypertrophic cardiomyopathy (181, 11.6%), dilated cardiomyopathy (111, 37.8%), acute myocardial infarction (823, 9.0%), healthy subjects (31,886, 0.3%). A histopathological and electron-microscopic evaluation of the atrial heart muscle revealed that the advancement of the morphological changes was closely related to the occurrence of atrial fibrillation. Decrease in size of F waves in the electrocardiogram correlated well with the extent of right and left atrial fibrosis. Also, it was noteworthy that the atrial fibrillation in cases with dissecting aneurysm (n = 60) was an expression of the myocardial damage due to the infiltration of the bleeding into the right atrium. Intra-atrial electrogram in 48 patients with various heart diseases revealed that the electric potentials obtained from various parts of the atrium varied to a great extent and finally the patient's condition transformed to that of atrial standstill. We conclude that atrial fibrillation is an expression of some important aspect of the progression of heart disease and is not directly associated with hemodynamic overloading to the atrium. A strategy for quinidine treatment was also introduced.

Age Factors↗