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Biomedical subjects

K Sekioka

Publications and source records attributed to K Sekioka.

6 recordsLinked to original sources
PubMed1992

Differences in direction-dependent shortening of the left ventricular wall in hypertrophic cardiomyopathy and in systemic hypertension.

To determine whether patients with hypertrophic cardiomyopathy (HC) have an altered mode of contraction of the left ventricular (LV) wall related to underlying myocardial abnormalities, geometric changes in the LV wall were analyzed at 2 points of the cardiac cycle (end-diastole and end-systole) using 2-dimensional echocardiography. The relations between meridional and circumferential shortening of the LV midwall, mean wall thickening, and the changes in the short-axis cross-sectional area of the LV wall at the level of chordae tendineae were determined in 18 patients with nonobstructive HC, and were compared with those in 31 normal subjects and 19 patients with essential systemic hypertension. In normal subjects, no significant difference was observed between meridional (16.3 +/- 2.4%) and circumferential (17.1 +/- 4.0%) shortening, whereas cross-sectional LV wall area increased significantly at end-systole (p < 0.001). In patients with hypertension, all measured indexes were not different from those in normal subjects. In contrast, patients with HC had significantly reduced meridional shortening (p < 0.001) and mean wall thickening (p < 0.01). Consequently, a striking difference was observed between meridional (8.9 +/- 2.4%) and circumferential (16.9 +/- 3.2%) shortening (p < 0.001). Furthermore, no increase in cross-sectional LV wall area was observed at end-systole. Thus, echocardiographic detection of direction-dependent contraction can be a useful index for distinguishing HC from systemic hypertension.

Adult↗
PubMed1989

Right ventricular function under acute cor pulmonale.

Many investigators have reported the hemodynamics in acute cor pulmonale clinically and experimentally. However, earlier studies have not made quantitative evaluations of the effects of coronary perfusion pressure and hypoxia on right ventricular contractility. We simulated acute cor pulmonale in nine isolated canine hearts and investigated the relationship of the process to cardiac deterioration and restoration. The afterload and preload of the right ventricle were controlled with a computer-assisted load control servosystem. Coronary perfusion pressure (COPP) was also controlled at either normal or variable levels identical to products of measured cardiac output and assumed values of systemic vascular resistance. Critical state (CS) was defined as a condition with an initial decrease in peak systolic pressure despite increased afterload. Within the normal range of PaO2 (105 +/- 5.3 mmHg), CS developed at a COPP of 51 +/- 5.1 mmHg, while under low PaO2 (51 +/- 2.3 mmHg), it developed at a COPP of 59 +/- 8.8 mmHg. As long as the COPP was normal (90 mmHg), the contractility of the right ventricle did not decrease despite hypoxia (PaO2 51 +/- 2.3 mmHg). An increase in systemic vascular resistance or administration of a beta-stimulant at CS restored the contractility of the right ventricle. However, an increase in preload decreased the contractility of the right ventricle.

Acute Disease↗
PubMed1989

Assessments of left ventricular function during exercise in patients with dilated cardiomyopathy: comparison with ischemic cardiomyopathy.

Responses to supine bicycle ergometer exercise were assessed in a study population consisting of 26 patients with dilated cardiomyopathy (DCM) and 23 patients with ischemic cardiomyopathy (ICM). Left ventricular ejection fraction (LVEF) and regional wall motion were analyzed at rest and during supine bicycle ergometer exercise with radionuclide ventriculography. Although the same degree of LVEF between DCM (23 +/- 8%) and ICM (26 +/- 4%) occurred at rest, the left ventricular regional wall motion abnormality was more prominent in DCM. LVEF during the peak exercise stage in DCM was almost unchanged (24 +/- 8%), but in ICM it decreased significantly (22 +/- 5%). Exercise-induced regional wall motion abnormalities were detected in nine patients (35%) in DCM and 13 patients (57%) in ICM. Although patients with DCM are believed to have diffuse hypokinesis of the left ventricle, severe regional wall motion abnormalities (akinesis or dyskinesis) were frequently observed. During the follow-up period of up to six years, eight patients with DCM died of congestive heart failure. In eight patients with DCM who showed decreased LVEF during exercise, five patients died. However, only three of 18 patients without decreased LVEF during exercise died. Exercise-induced left ventricular dysfunction in DCM seems to be a poor prognostic sign.

Adult↗
PubMed1987

Estimation of ventricular source parameters and its load matching state in vivo.

Ventriculo-arterial coupling states were estimated by calculating left ventricular hydromotive pressure (Ps), source impedance (Zs) and input impedance (Zl) in 24 mongrel dogs with Fourier transforms of ventricular pressure and aortic flow immediately before and after instantaneous changes of arterial load. Calculated Ps (Psc) were compared with measured left ventricular isovolumic pressures (Psm) in various inotropic and loading states. Psc waveforms coinciding closely with those of Psm were obtained by cutting off higher frequencies within the fifth to tenth harmonics prior to the inverse Fourier transformation. The regression equation was Psc = 1.08 Psm +0.68 (r = 0.978). In control conditions, the ratio of Zs (0) / Zl (0) (function of frequency, 0 = zero Hz) was close to the ratio of ejection phase to one whole cardiac cycle, and the ratio of peak Psm to left ventricular ejection pressure was 1.85 +/- 0.25 SD. These results imply the presence of a ventriculo-arterial load matching state in control conditions.

Animals↗
PubMed1986

[Power spectrum of heart murmurs: special reference to mitral regurgitant murmurs].

Heart murmurs, especially the mitral regurgitant murmurs of 40 patients were analyzed using the fast Fourier transformation technique. 1. Three types of frequency spectral pattern of mitral regurgitation (MR) were demonstrated: A) broad, spanning 100 to 500 Hz, B) narrow, characterized by one giant peak, and C) two peaks. The reason for these patterns was not clear, but they may be related to various hemodynamic events. 2. The mean frequency (f) in MR was 295 +/- 38 Hz and it increased in proportion to the regurgitant grade: e.g., Sellers II, 258 +/- 27 Hz; Sellers III, 294 +/- 23 Hz; and Sellers IV, 311 +/- 65 Hz. The accumulated percentage of the 200-400 Hz component decreased, while that of the 400-600 Hz component increased. 3. The f in MR of various etiologies were as follows: It was higher in ruptured chordae tendineae, rheumatic cases and mitral valve prolapse syndrome, but was lower in papillary muscle dysfunction and dilated cardiomyopathy. In the latter two, the percentage of the 0-200 Hz component was greater than in other disorders. The degree of left ventricular dysfunction and of myocardial injury may be responsible for the changes in the propagation properties. In ventricular septal defect and aortic stenosis, the f was 306 +/- 12 Hz and 230 +/- 40 Hz, respectively. The frequency spectrum of the latter was lower than that of MR, which may be derived from the difference between ejection and regurgitant murmurs; whereas, that of ventricular septal defect was similar to that of rheumatic MR. 4. The relation between the frequency spectrum and the phase of systole was studied. In dilated cardiomyopathy and papillary muscle dysfunction, the f of each phase increased in late systole; whereas, the maximum f was in mid-systole in other disorders. 5. Administration of amyl nitrite resulted in a decreased f, an increased percentage of the 0-200 Hz component, and a decreased 400-600 Hz component. The spectral distribution shifted to the lower frequency region. Results of this study suggested that significant information can be obtained from the frequency analysis of heart murmurs.

Adolescent↗