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Biomedical subjects

K Mizushige

Publications and source records attributed to K Mizushige.

At least 91 records · Page 5Linked to original sources
PubMed1997

Adult Still's disease with myocardial dysfunction induced by microangiopathy.

A 52-year-old man with inflammatory disease of unknown origin but no specific laboratory abnormalities was referred to our hospital. He has subsequently diagnosed as having adult Still's disease. During an episode of severe inflammation he suffered reversible myocardial damage as revealed by electrocardiography, echocardiography and 201Tl myocardial scintigraphy; this was ameliorated by treatment with steroids and immunosuppressive drugs. No significant stenosis of the coronary artery was observed on coronary angiography. Interstitial mononuclear infiltration was apparent in the right ventricle on endomyocardial biopsy. Myocardial injury with adult Still's disease, which may result in heart failure, has rarely been reported. We report a case of adult Still's disease with myocardial dysfunction that may have been caused by microangiopathy.

Heart↗
PubMed1996

A new noninvasive method of diagnosing vasospastic angina based on dilation response of the left main coronary artery to nitroglycerin as measured by echocardiography.

OBJECTIVES: The purpose of the present study was to evaluate the feasibility of diagnosing vasospastic angina based on coronary artery tone as assessed by M-mode echocardiographic measurement of the dilation response of the left main coronary artery to nitroglycerin. BACKGROUND: The definite diagnosis of vasospastic angina is done by a coronary spasm provocative test using ergonovine maleate or acetylcholine during cardiac catheterization. Current noninvasive, nonpharmacologic diagnostic methods are not sensitive enough for the diagnosis of vasospastic angina. METHODS: Thirty-eight patients who had an angiographically normal left main trunk were studied. These patients were classified into four groups based on the presence or absence of more than 50% stenosis in the coronary arteries except for the left main trunk and the results of the acetylcholine or ergonovine provocative test. At 7 a.m. and at noon on the same day, the left main trunk diameter was measured by M-mode echocardiography before and after sublingual administration of nitroglycerin (0.3 mg), and its present dilation was calculated to assess coronary artery tone. RESULTS: The percent dilation of the left main trunk diameter induced by sublingual nitroglycerin at 7 a.m. and at noon was 22.4 +/- 4.7% (mean +/- SD) and 18.1 +/- 4.0% in 11 patients with vasospastic angina and without coronary stenosis, 14.9 +/- 7.1% and 11.2 +/- 6.9% in 9 patients with vasospastic angina and coronary stenosis, 6.1 +/- 3.5% and 7.0 +/- 5.1% in 8 patients without vasospastic angina but with coronary stenosis and 8.1 +/- 5.6% and 7.8 +/- 5.7% in 10 control subjects. The percent dilation at 7 a.m. was significantly greater in the vasospastic angina without coronary stenosis group than in the remaining three groups, and in the vasospastic angina groups, the percent dilation at 7 a.m. was significantly greater than that at noon. When percent dilation at 7 a.m. exceeding 15% was defined as positive for the diagnosis of vasospastic angina, the sensitivity was 80% and the specificity 94%. CONCLUSIONS: Basal tone of the left main trunk is elevated in the early morning in vasospastic angina. Dilation of the left main trunk diameter exceeding 15% induced by sublingual nitroglycerin in the early morning as measured by M-mode echocardiography is a highly sensitive and specific criterion for the diagnosis of vasospastic angina.

Angina Pectoris↗
PubMed1996

Differential responses in left ventricular diastolic filling dynamics with isometric handgrip versus isotonic treadmill exertion.

Although the hemodynamic responses to isotonic and isometric exercise are different, few data exist comparing the response to left ventricular (LV) diastolic filling dynamics with these two forms of exertion. Therefore we performed Doppler examination before and at the end of isotonic and isometric exercise in 20 normal volunteers to define the differential responses of LV filling to these two forms of exertion. Transmitral inflow velocity signals from the apical view and phonocardiography were recorded before and at the termination of treadmill exercise (TRD) to 11 METs and handgrip (HG) 50% maximal for 2 minutes). Mean blood pressure (mBP), heart rate (HR), early diastolic (E) and late atrial (A) inflow velocities, mean acceleration rate (ACC) of E wave, time velocity integral of inflow (Ti), and isovolumic relaxation time (IRT) from second heart sound to onset mitral inflow were measured. Absolute changes from baseline were significantly different for the two forms of exertion: TRD versus HG: BP = 11 +/- 9 versus 36 +/- 10 mm Hg, HR = 37 +/- 16 versus 16 +/- 9 beats/min, E = 11.6 +/- 11.3 versus -7.0 +/- 9.4 cm/sec, A = 29.9 +/- 14.5 versus 14 +/- 12 cm/sec, ACC = 164 +/- 151 versus -56 +/- 135 cm/sec2, Ti = 1.9 +/- 3.0 versus -1.7 +/- 1.7 cm, and IRT = -12 +/- 9 versus 9 +/- 10 msec, all p < 0.0001 except for A, p < 0.001). Isotonic treadmill exercise resulted in enhanced early diastolic filling manifested by increases in E and ACC and a decreased in IRT. Conversely, isometric handgrip exercise produced evidence of reduced early filling including decreased E and ACC and slightly increased IRT. Thus the response of LV filling dynamics recorded by Doppler differs for isotonic and isometric exertion and likely reflects the variable pressure and flow alterations induced by these two forms of exertion.

Adult↗
PubMed1996

[Cyclic alteration in atheroma plaque morphology observed by intracoronary ultrasound: initiation mechanism of acute myocardial infarction].

Rupture of plaque is an important factor in the initiation of acute myocardial infarction. Plaque rupture is related to stress distribution in atheroma, but morphological alteration in coronary atheroma plaque in vivo is little understood. Atheroma plaque was observed during the cardiac cycle using 3.5 or 2.8 F, 30 MHz intracoronary ultrasound (ICUS) in seven patients with coronary artery disease. Coronary ostial pressure (P) measurements were simultaneously performed. Seven of the eccentric stenotic sites were analyzed. Intima-medial thickness (Th) and regional radius of curvature (R) at the middle and lateral portions of the atheroma were measured. Delta Th and % delta Th were calculated from change in thickness from end-diastole to peak systole. These parameters of the middle portion were compared with those of the lateral portion. The lateral % delta Th was 20.1 +/- 13.6% (delta Th 0.13 +/- 0.08 mm; 0.69 to 0.56 mm), and was significantly greater than the middle % delta Th [5.8 +/- 6.6% (delta Th 0.06 +/- 0.08 mm; 1.24 to 1.18 mm), p < 0.05]. Regional radius of curvature did not significantly differ. Wall stress calculated as P x R/Th was greater at the lateral portion (peak systole 3.7 x 10(5) dynes/cm2, end-diastole 1.9 x 10(5) dynes/cm2) than at the middle portion (peak systole 1.4 x 10(5) dynes/cm2, end-diastole 0.9 x 10(5) dynes/cm2). The change in stress from end-diastole to peak systole at the lateral portion was significantly greater (1.8 x 10(5) dynes/cm2) than that at the middle portion (0.5 x 10(5) dynes/cm2). The change in stress during the cardiac cycle, caused by the increase in intracoronary pressure, was greater at the lateral than at the middle of the plaque. This imbalanced distribution of stress may result in greater thinning of plaque at the lateral portion. Therefore, the distortion of plaque may be a mechanism for atheroma rupture at the lateral portion.

Aged↗
PubMed1995

Effects of pulmonary venous flow direction on mitral regurgitation jet area as imaged by color Doppler flow mapping. An in vitro study.

BACKGROUND: Although the effects of adjacent walls and left atrial pressure on mitral regurgitation (MR) jet area imaged by color Doppler have been examined, few data exist regarding the influence of pulmonary venous (PV) filling flow on regurgitant jets. Therefore, we designed a left atrial model to examine the relation between PV flow direction and MR jet area. METHODS AND RESULTS: The left atrial chamber (7.6 cm in diameter) was built with a PV inflow (1.0 cm in diameter) and mitral valve regurgitant orifice in the same plane. The MR jet was simulated as fixed in volume and velocity (3.5 m/s) and directed with a pulsatile pump into the left atrial model. PV flow with a constant velocity (30 cm/s) was driven by gravity (83 cm H2O). With left atrial mean pressure at either 10, 30, or 50 mm Hg, four flow patterns were examined: (1) PV flow away from the mitral valve, MR jet toward the pulmonary vein; (2) PV flow toward the mitral valve, MR jet toward the pulmonary vein; (3) PV flow away from the mitral valve, MR jet away from the pulmonary vein; and (4) PV flow toward the mitral valve, MR jet away from the pulmonary vein. MR color Doppler images were recorded with a 3.5-mHz frequency transducer and at 7-kHz pulse repetition frequency. For each condition, we compared jet area, length, and width of the MR signal. MR jet areas for conditions 3 and 4 were larger at 10 mm Hg than at 30 or 50 mm Hg left atrial pressure. Especially at the lower pressures, PV flow diminished the MR jet area in condition 4 compared with that in condition 3, such that MR jets were smaller in condition 4. In conditions 1 and 2, the jets were imaged at an oblique angle and were smaller than in conditions 3 and 4 (P < .001), but they were not significantly different from each other as imaged. CONCLUSIONS: In this model, factors including the direction of PV flow, the direction of MR as relates to the angle of interrogation, and the level of left atrial pressure influenced the size of MR jets. The effect of PV flow direction was diminished by increased left atrial pressure. PV flow directed away from the mitral valve was associated with larger MR jets than when PV flow was directed toward it (condition 4), probably because of jet distortion and flattening.

Blood Flow Velocity↗
PubMed1995

[Latent impairment of left ventricular filling in hypertension without left ventricular hypertrophy and improvement by dipyridamole treatment: pulsed Doppler echocardiography study].

Left ventricular (LV) filling impairment in patients with hypertension (HT) not necessarily associated with LV hypertrophy has not been sufficiently investigated. Therefore, we examined the response of LV filling to isometric exercise in patients with HT without LV hypertrophy and LV filling abnormality at rest. We studied 25 patients (aged 40 to 66 years, mean 51 +/- 7 years) and 13 age-matched normal subjects. The HT patients were selected by the following criteria: 1) systolic blood pressure (sBP) over 160 mmHg and/or diastolic BP over 90 mmHg was observed at least three times during the last 6 months, 2) LV wall thickness was under 11 mm, and 3) the ratio of peak atrial LV inflow velocity (A) to peak early diastolic LV inflow velocity (E) was within the mean +/- SD of normal subjects. LV inflow was measured by pulsed Doppler flowmetry before and during handgrip exercise (50% maximal effort for one minute and a half) in the patients before [HT-D (-)] and after [HT-D (+)] dipyridamole (D) administration (0.28 mg/kg/4 min) and in the normal subjects (N). Doppler-derived indices were A, E, A/E, DR (the deceleration rate from peak to half of the early diastolic inflow velocity), % delta A/E (% change in A/E from baseline), and % delta DR (% change in DR from baseline). There was no significant difference in LV wall thickness between the HT and N groups. There was also no significant difference in A/E at rest between the three groups. Increase of sBP and heart rate were similar in all groups during handgrip exercise.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1995

Stiffness of human arterial wall assessed by intravascular ultrasound.

Little is known about the elastic properties of human arteries. Intravascular ultrasound (IVUS) can measure the instantaneous circumference or diameter of the arteries during a cardiac cycle, and so investigate human arterial elasticity in vivo. We studied 36 patients aged from 35 to 72 years classified into the ischemic heart disease (IHD) group (21 patients aged 39 to 71 years) and the non-ischemic heart disease (NIHD) group (15 patients aged 35 to 76 years) who had no atherogenic factors. The stiffness and wall morphology of six portions from the thoracic descending aorta to common iliac artery were measured by 8F, 15 MHz IVUS. The stiffness parameter, beta, was calculated as 1n (Pmax/Pmin)/(Cmax/Cmin-1), where P is arterial pressure, and C is the circumference of the artery. The thickness of the intima-media complex echo (Th) was used as a substitute for the wall thickness, and Th/D was calculated as an index of relative wall thickness, where D is the minimum luminal diameter. The pulse wave velocity (PWV) was measured with a conventional method. beta increased after branching of the renal artery and increased much more toward the periphery in comparison with the thoracic descending aorta in both groups. At all portions except the abdominal aorta after branching of the renal artery and the common iliac artery, beta was significantly larger in the IHD than the NIHD group. Th/D increased as well as beta in both groups. At all portions except after branching of the renal artery, Th/D was significantly larger in the IHD than the NIHD group.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

Contrast echocardiography for evaluation of left ventricular flow dynamics using densitometric analysis.

BACKGROUND: Few data exist regarding intraventricular flow patterns in the presence of left ventricular dysfunction. Therefore, we examined the relation between intracavitary left ventricular flow dynamics and the presence of ventricular contractile abnormalities using videodensitometric analysis of transpulmonary contrast echocardiography. METHODS AND RESULTS: Two-dimensional echocardiography was performed before, during, and after intravenous injection of sonicated albumin in 8 normal subjects, 22 patients with infarction, and 6 patients with dilated cardiomyopathy. Time-intensity curves were recorded, and disappearance half-times (in cardiac cycles) were measured for regions of interest at the mitral orifice (Ta) and mid-left ventricular cavity (Tb). We observed contrast enhancement of the left ventricular cavity in 28 of 36 patients. Ta and Tb were identical (19 beats) in all normal patients, but Tb was greater than Ta (19 versus 22 beats, P < .001) in patients with dyssynergy. Patients with dyssynergy were divided in three groups: group A, in whom Tb-Ta < or = 3; group B, in whom Tb-Ta > or = 4; and group C, which was composed of patients without contrast enhancement. Left ventricular end-diastolic dimension was similar in normal patients (46.1 mm) and group A patients (50.3 mm) but was less in each cohort than in groups B (58.7 mm) and C (64.1 mm) (all P < .01). Significant correlation was observed between Tb-Ta and both ejection fraction (r = -.67, P < .001) and wall motion index (r = .62, P < .001). CONCLUSIONS: Clearance of contrast from the mid-left ventricular cavity is prolonged in patients with left ventricular dysfunction. This prolongation may be related to increased left ventricular diastolic volume, impaired intracavitary mixing, or paradoxical systolic flow. Delayed left ventricular contrast washout may have implications regarding the formation of left ventricular thrombi.

Adult↗
PubMed1992

Evaluation of arterial wall histological and physical characteristics using intravascular echography.

Using a high-frequency ultrasound intravascular imaging system we evaluated the intravascular echo image by comparing it with histological findings in 57 arterial segments of 17 autopsy cases. Moreover, in 8 dogs we estimated the arterial elastic property by observing the change of the arterial section accompanying a reduction of arterial pressure due to hemorrhage (H) or nifedipine infusion (N). The characteristics of the intravascular echograms were as follows: 1) In a normal artery the arterial wall consisted of the inner high echoic, the medial low echoic and the outer high echoic layers. 2) In an aged artery the fibrous thickened intima was seen as the low echo layer giving an echo about the same as that of the normal media, and the intensity of the echo from the degenerated media was lower than that of the normal media. 3) In atheroma the echo intensity of the elastic fiber-rich region was higher than that of the surrounding region, while the calcified region showed as a brighter echo with outer echo free space due to shadowing. We measured the arterial radius, area and circumferential length on the intravascular echo image and calculated the arterial wall tension-circumferential length and the pressure-arterial area relationships. By analysing each relation, we obtained the stiffness and compliance parameters, respectively. The stiffness parameter with N was lower than that with H [(1.5 +/- 0.5) x 10(-2) vs (2.8 +/- 0.9) x 10(-2)] and the compliance parameter with N was higher than that with H (0.92 +/- 0.28 vs. 0.46 +/- 0.12).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

[Transesophageal Doppler echocardiographic imaging and blood flow measurements for the diagnosis of stenotic left coronary arteries].

To evaluate the usefulness of transesophageal Doppler echocardiography (TEE) in diagnosing left coronary artery (LCA) stenosis, we studied 26 patients with 33 proximal LCA lesions, including 5 with lesions of the left main trunk (LMT), 21 proximal anterior descending arteries (LAD), 7 proximal circumflex arteries (LCx), and 20 with normal coronary arteries. We measured blood flow velocity along the LCA using the pulsed Doppler mode (PD) and obtained velocities at multiple neighboring sites in 13 normal coronary arteries and in 12 of 26 LMTs or LADs with lesions. In all 13 normals, peak velocity tended to decline towards the periphery. By contrast, in one LMT and 10 LADs with lesions, marked increase in peak velocity (1.7 to 3.9 times) was observed at the sites diagnosed as stenotic lesions by coronary angiography. Using two-dimensional echocardiography (2DE), 24 LMTs including 3 with lesions, 4 LADs including 3 with lesions and 13 LCxs including 4 with lesions were imaged. Among them, 3 LMT, one LAD and 2 LCx lesions were correctly diagnosed. The diagnostic ratio by both PD and 2DE was 60% for LMT (PD: 20%, 2DE: 60%), 48% for LAD (PD: 48%, 2DE: 5%) and 29% for LCx (PD: 0%, 2DE: 29%) lesions. In conclusion, TEE proved to be useful in diagnosing proximal LCA stenosis. The coronary flow measurement by PD especially has the potentiality for the diagnosis of proximal LAD stenosis.

Adult↗
PubMed1991

[Imaging of coronary arteries and measurement of coronary flow using transesophageal Doppler echocardiography: a comparison with transthoracic Doppler echocardiography].

Recent advances in Doppler echocardiographic techniques, especially using transesophageal approach, enable us to observe coronary arteries and their blood flow. However, the advantages of transesophageal approach in the evaluation of coronary artery are indistinct. The aim of this study was to examine the ability of transesophageal Doppler echocardiography (TED) and transthoracic Doppler echocardiography (TTD) to visualize coronary artery and measure its flow. The study population consisted of 17 healthy subjects and 41 patients with heart diseases (arrhythmia in 2, valvular disease in 10, ischemic heart disease without complete or subtotal obstruction of coronary artery in 22, congenital heart disease in two, cardiomyopathy in four, and infective endocarditis in one). Thirty subjects were examined by TED, and 44 subjects were examined by TTD. Two patients with complete obstruction of the proximal right coronary artery (RCA), who were not included in the above-mentioned subjects, were examined by TED. The results were as follows: 1) The detection rate of coronary arteries by TED and TTD were: left main trunk (LMT); 96.7/86.4%, left anterior descending artery (LAD) and left circumflex artery (LCx); 83.3/56.8%, and RCA; 63.3/38.6%, respectively. 2) Visible length from the orifice: LMT to LAD; 22.2/30.8 mm, RCA; 20.4/22.3 mm. 3) The detection rate of coronary flow by pulsed Doppler of the two methods: LMT; 66.8/0%, LAD; 70.0/31.8%, LCx; 6.6/0%. RCA; 26.7/0%. 4) Coronary flow was detected by transesophageal two-dimensional Doppler in 73.3% of LMT, 76.6% of LAD, 6.6% LCx and 43.3% of RCA. 5) RCA flow was not detected by transesophageal two-dimensional Doppler in two patients who had complete obstruction of the proximal RCA although RCA near the orifice was obviously imaged by two-dimensional echocardiography. In conclusion, TED had an advantage over TTD in detecting coronary arteries and their blood flow, but TTD had an advantage over TED as to the visible length of coronary artery. When RCA near the orifice was clearly visualized, the absence of RCA flow by TED implied complete obstruction of the proximal RCA.

Arteries↗
PubMed1990

Evaluation of left-sided valvular regurgitation in healthy, hypertensive and myocardial infarction subjects by Doppler echocardiography.

Doppler echocardiography has become a very useful and widely employed imaging technique for evaluating valvular regurgitation, and has thus lead to the discovery of regurgitation in unexpected subjects. In this study, we examined left-sided valvular regurgitation in 31 healthy subjects, 35 patients with hypertension and 43 patients with old myocardial infarction by Doppler echocardiography. Aortic regurgitation was found in 3% of healthy subjects, 8% of hypertensive patients and 5% of patients with myocardial infarction. Mitral regurgitation was found in 35% of healthy subjects, 69% of hypertensive patients and 84% of patients with myocardial infarction. The pathogenesis of mitral regurgitation in hypertension is considered to be the impairment of the mitral leaflets, since neither anatomical nor functional abnormalities were found in the subvalvular mitral apparatus. Left ventricular dilatation and asynergy near the papillary muscles were related to the pathogenesis of mitral regurgitation in myocardial infarction. Mitral regurgitation in healthy subjects and hypertensive patients was mild and resistant to afterload stress, suggesting that it was less pathological. On the other hand, mitral regurgitation in myocardial infarction was easily worsened by afterload stress. Doppler echocardiography has thus provided us with new insights into valvular regurgitation in healthy subjects and patients without rheumatic valvular disease.

Adult↗
PubMed1990

[Intracardiac flow vector measurement by simultaneous dual-frequency two-beam pulsed Doppler echocardiography].

Conventional single-beam pulsed Doppler echocardiography has certain limitations in quantitatively measuring the intracardiac blood flow, because the Doppler incident-angle to the flow stream is uncertain. In the present study, the absolute velocity and direction of the intracardiac blood flow, i.e., flow vector, were measured using our newly-developed dual-frequency two-beam pulsed Doppler echocardiography. This instrument has two transducers with center frequencies of 3.5 MHz (main-beam) and 2.2 MHz (sub-beam) which are linked by two arms. Three potentiometers are set up by the three joints to sense the relative angles. Two velocity components at the intersection of the main- and sub-Doppler beams were measured simultaneously with different directional approaches. The flow vector was calculated manually from the two velocity components. The study population consisted of 18 healthy subjects ranging in age from 23 to 39 years. The left ventricular (LV) inflow vector was measured at the center of the mitral annulus, and the ejection flow vector was measured at the levels of the tip (E1) and the mid-portion (E2) of the anterior mitral leaflet in the LV outflow tract. The results were as follows: 1. The LV rapid inflow (R) was directed slight posteriorly towards the cardiac apex, and its average maximal velocity was 78 +/- 15 cm/sec (mean +/- SD). The LV inflow due to the atrial contraction was directed even more posteriorly than was the R, and its average maximum velocity was 43 +/- 10 cm/sec. 2. The LV ejection flows at E1 and E2 were directed slightly posteriorly rather than parallel to the interventricular septum, and the maximum velocity at E1 and E2 was 53 +/- 20 m/sec and 85 +/- 23 cm/sec, respectively. In conclusion, the dual-frequency two-beam pulsed Doppler technique allows quantitative measurement of the intracardiac blood flow dynamics regardless of the Doppler incident-angle to the flow stream.

Adult↗