Biomedical subjects

S Tadaoka

Publications and source records attributed to S Tadaoka.

At least 19 recordsLinked to original sources

PubMed1999

Measurement accuracy of the flow velocity in pulsed ultrasound Doppler velocimeter.

This paper presents a numerical simulation method for evaluating the measurement accuracy of the high-frequency pulsed ultrasound Doppler velocimeter (PUDV). The frequency distribution of the Doppler signal from a sample volume is calculated by dividing the sample volume into small cells and using the statistics of the velocities of the cells. The distribution is used to analyze the accuracy of the poststenotic velocity measurements of a 20-MHz 80-channel PUDV. The target flow field is obtained by solving Navier-Stokes equations numerically. It was shown that the velocities evaluated by the zero-cross and Fourier transform methods agreed well with the given velocities, and that flow separation was successfully detected. It was also shown that the tube diameter should be at least twice as large as the diameter of the sample volume to obtain accurate measurements.

Blood Flow Velocity↗

PubMed1993

Decreased mid-to-late diastolic decay of diastolic coronary artery flow velocity in pressure-overloaded left ventricular hypertrophy.

This study was carried out to investigate the characteristics of coronary arterial flow in left ventricular hypertrophy secondary to systemic hypertension. The blood velocities in the left anterior descending coronary artery (LAD) were measured by a No. 3F 20 MHz Doppler catheter in 23 hypertensive patients with left ventricular hypertrophy (systolic/diastolic pressure: 181 +/- 15/100 +/- 4 mmHg) and 13 patients with atypical chest pain, but without left ventricular hypertrophy and any abnormal hemodynamic findings. All patients had normal coronary arteriograms. The LAD blood velocity waveforms in pressure overloaded left ventricular hypertrophy were characterized by both a decreased mid-to-late diastolic deceleration rate (delta V/delta T) and a normalized value of delta V/delta T by peak diastolic velocity [delta V/(delta T.Vpeak)], as well as delayed early diastolic inflow (time for diastolic rise; TDR). The values of the delta V/(delta T.Vpeak) in the patients with hypertensive left ventricular hypertrophy and in the normotensive controls were 1.26 +/- 0.61 and 3.03 +/- 1.18/s, respectively (P < 0.001). The TDR was 145 +/- 56 and 66 +/- 15 ms (P < 0.001). In patients with hypertensive left ventricular hypertrophy, the delta V/(delta T.Vpeak) correlated well with the degree of hypertrophy (r = 0.75, P < 0.01) and with the TDR (r = 0.82, P < 0.01). The coronary flow reserve, calculated from the ratio of the diastolic mean velocity after intracoronary injection of papaverine to the resting flow velocity increased with the delta V/(delta T.Vpeak) (r = 0.68, P < 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1993

Velocity profiles and phasic flow patterns in the non-stenotic human left anterior descending coronary artery during cardiac surgery.

OBJECTIVE: The aim was to investigate the phasic characteristics of normal human left coronary artery flow and velocity profiles across the vessel. METHODS: The phasic characteristics of flow in the human left anterior descending coronary artery, the centreline flow velocities, and the velocity profiles were measured in 10 patients during corrective surgery for atrial septal defect after closure of the defect. None of these patients had any detectable coronary artery stenosis or left ventricular hypertrophy. Measurements were made with a 20 MHz 80 channel pulsed Doppler velocimeter. RESULTS: The velocity waveform displayed a diastolic-predominant pattern with a systolic to diastolic velocity ratio of 0.29(SD 0.17). Reverse flow was observed in early systole in five patients and in mid to late systole in six patients. The values of peak Reynolds number, unsteadiness parameter, and pulsatility index were 504(198), 2.5(0.6), and 5.9(4.4) respectively. The velocity profiles during diastole showed considerable variability in shape, ranging from symmetrical to skewed to M shaped patterns. The peak wall shear rate was 765(250) s-1 on the epicardial wall of the vessel and 712(301) s-1 on the myocardial wall; the difference was not statistically significant. CONCLUSIONS: The velocity waveform displayed a diastolic-predominant pattern. Considerable variability in shape of the velocity profile was found and was perhaps due to the time evolution of the velocity profile within the diastolic time period.

Adolescent↗

PubMed1992

[Possible pathogenesis of giant negative T and negative U waves in hypertrophic cardiomyopathy: a report of two cases].

Giant negative T (GNT) and negative U (NU) waves are electrocardiographic findings which have been frequently observed in hypertrophic cardiomyopathy (HCM). Here we report 2 cases. For the first patient, electrocardiographic and left ventriculographic studies before and after the development of GNT and NU waves and left ventricular high voltage during the follow-up period were performed. For the second patient, electrocardiographic and echocardiographic findings were obtained before and after onset of posterior myocardial infarction. In the first patient, posterior papillary muscle hypertrophy was evident on left ventriculography after appearance of GNT and NU waves. In the second patient, both GNT and NU waves disappeared after posterior myocardial infarction. Two-dimensional echocardiograms demonstrated akinesis in the posterior wall, including the posterior papillary muscle, after 8 weeks of posterior infarction. Therefore, we suggest that apical hypertrophy, especially of the posterior papillary muscle, may play an important role in the pathogenesis of GNT and NU waves in HCM.

Aged↗

PubMed1992

[Effect of heart rate on cardiac hemodynamics in patients with aortic regurgitation].

We evaluated the effects of heart rate on cardiac hemodynamics in 10 patients with aortic regurgitation (AR, mean regurgitant fraction: 64.3%). Cardiac catheterization was performed in all patients, and the hemodynamic parameters were obtained by increasing heart rate (80.100.120.140) using right atrial pacing. Regurgitant fraction and total systemic resistance were improved up to 100/min, but aggravated on further increase in heart rate. Cardiac function curve was remarkably improved up to 100/min, but aggravated on further increase in heart rate. LV end-diastolic pressure-volume relation was moved toward the left lower direction up to 100/min, but toward the left upper direction on further increase in heart rate. Thus, it was concluded that in severe AR, cardiac function was improved up to 100/min, but aggravated on further increase in heart rate.

Aortic Valve Insufficiency↗

PubMed1991

Effect of left ventricular hypertrophy secondary to systemic hypertension on left coronary artery flow dynamics.

STUDY OBJECTIVE: The aim was to clarify the characteristics of the phasic blood velocity pattern and their possible causes in left ventricular hypertrophy secondary to systemic hypertension. DESIGN: Measurements of blood velocities in the left anterior descending coronary artery were made with a 20 MHz Doppler catheter with a top mounted annular crystal. All patients had normal coronary arteriograms. PATIENTS: 23 hypertensive patients [systolic/diastolic pressure: 181(SD 15)/100(4) mm Hg)] with left ventricular hypertrophy, and 13 atypical chest pain patients without left ventricular hypertrophy or any abnormal haemodynamic findings (normal controls) entered the study. MEASUREMENTS AND MAIN RESULTS: The left anterior descending coronary artery blood velocity waveform in pressure overloaded left ventricular hypertrophy was characterised by delayed early diastolic inflow. The diastolic rise time of coronary flow (TDR), ie, the time from the beginning of diastole to peak velocity, was higher in patients with hypertensive left ventricular hypertrophy than in normal controls, at 145(56) v 66(15) ms, p less than 0.001. In patients with hypertensive left ventricular hypertrophy, TDR correlated well with the degree of hypertrophy (r = 0.83, p less than 0.01) and also with peak left ventricular systolic pressure (r = 0.62, p less than 0.01). The coronary flow reserve, calculated from the ratio of the diastolic mean velocity after intracoronary injection of papaverine to the resting flow velocity, decreased with prolongation of TDR (r = 0.58, p less than 0.02). CONCLUSIONS: (1) Impairment of early diastolic coronary arterial inflow is the most remarkable characteristic in pressure overloaded left ventricular hypertrophy; (2) preceding systolic vascular compression and impaired left ventricular relaxation correlate with the delayed early diastolic inflow; (3) the delayed inflow is an important possible cause of the decreased coronary flow reserve in the hypertensive left ventricular hypertrophy.

Adult↗

PubMed1991

[Exercise induced precordial T wave normalization associated with U wave inversion in detection of left anterior descending artery stenosis].

Although normalization of inverted T wave is not an uncommon finding during exercise tests, it's clinical significance is still unclear. Exercise 12-lead electrocardiograms (ECGs) were recorded by using Master's 2-step or ergometer. T wave normalization in the anterior chest leads was found in 20 patients with, and 14 patients without coronary artery disease (CAD). Coronary angiography and/or exercise Tl-201 myocardial imaging were also performed in every patient. Exercise-induced T wave normalization was defined as "inverted T wave at rest becoming upright during exercise". ST segment, T and U wave amplitudes were measured before and immediately after exercise. 1) All of the 20 patients (100%) with CAD demonstrated critical stenosis of the left anterior descending artery (LAD). 2) ST deviation was noted in none of the 14 patients (0%) without CAD, and in only 4 of the 20 patients (20%) with CAD. 3) T wave amplitude increased equally in patients both with and without CAD. 4) Exercise-induced U wave inversion was found in 16 of the 20 patients (80%) with CAD, whereas it was found in only 1 of the 14 patients (7%) without CAD. 5) The sensitivity of "U wave inversion" in detection of LAD stenosis was 80%, and the specificity was 93%. We conclude that exercise-induced T wave normalization associated with U wave inversion in anterior chest leads is highly indicative of the specific presence of critical LAD stenosis.

Adult↗

PubMed1991

[Left ventricular hypertrophy secondary to systemic hypertension: its effect on coronary hemodynamics].

To clarify the characteristics and possible causes of phasic blood velocity patterns in pressure overload hypertrophy, we measured blood flow velocities in the left anterior descending coronary arteries in 16 patients with left ventricular hypertrophy secondary to systemic hypertension. These measurements were made with a 20MHz Doppler catheter. All patients had normal coronary arteriograms. The blood flow velocity patterns were characterized by the decrease in the rise of early diastolic inflow velocity. Prolongation in the time from the onset of diastole to peak velocity (TDPV) correlated with the degree of left ventricular hypertrophy. TDPV was prolonged in proportion to the increase in the peak left ventricular systolic pressure and left ventricular ejection fraction. The flow reserve calculated from the ratio of the diastolic mean velocity after the intracoronary injection of papaverine to the resting flow showed a trend toward the decrease proportional to the prolongation in TDPV due to an increase of wall thickness. In conclusion, preceding systolic vascular compression and systolic vascular strain can be factors causing early diastolic inflow disturbance in left ventricular hypertrophy secondary to hypertension. The decrease of coronary reserve may partially be attributable to the decrease in the rise of early diastolic inflow velocity.

Adult↗

PubMed1991

[Treadmill exercise test in patients with hypertrophic cardiomyopathy with and without coronary artery disease].

We studied whether the treadmill exercise test can discriminate between normal and significant narrowing of coronary arteries in patients with hypertrophic cardiomyopathy (HCM) accompanied with chest pain, and we compared the extent of myocardial ischemia during exercise. Thirty one patients with HCM were divided into two groups; 21 with normal coronary arteries and 11 with significant narrowing of coronary arteries. The treadmill exercise test was carried out in both groups. The following parameters were more frequently seen in the group with coronary stenosis. (1) short treadmill time (338, sec vs 542, p less than 0.05). (2) delta SBP less than or equal to 60 mmHg (delta: end point minus rest, 10 cases vs 12, 0.05 less than p less than 0.1). (3) significant delta ST depression (0.17 mV vs 0.05, p less than 0.05). (4) large delta ST/delta HR (3.3 microV.min/beats vs 0.7). delta ST/delta HR greater than or equal to 2.0 was the most useful for differentiating the two groups, and it was 90% in index both sensitivity and specificity for diagnosis of HCM with significant narrowing of the coronary arteries. It was concluded that treadmill exercise induced more severe myocardial ischemia in patients with HCM who had significant narrowing of the coronary arteries than in patients with HCM who had angiographically normal coronary arteries. The delta ST/delta HR was the most useful index for diagnosis of HCM with significant narrowing of the coronary arteries.

Blood Pressure↗

PubMed1990

Accuracy of 20-MHz Doppler catheter coronary artery velocimetry for measurement of coronary blood flow velocity.

The accuracy of 20-MHz Doppler catheter coronary artery velocimetry (Millar Instruments) was evaluated by model experiments using a turntable and a flow tube. In the turntable experiments, the flow away from the catheter tip (away flow) was significantly lower than that toward the catheter (toward flow), but the measured velocities for both away and toward flows were always lower than the known velocities. Nevertheless, the blood velocities measured at a sampling point 4 mm from the catheter tip showed excellent correlation with the known velocities irrespective of flow direction. The shape of the FFT spectra of the Doppler shift frequency from blood was broadened, and the frequency corresponding to the known velocity was always close to the maximum Doppler shift frequency. We concluded that zero-cross detection of blood velocity by the 20-MHz pulsed Doppler catheter provides a reliable measure for evaluating relative velocity changes, although it underestimates the blood velocity.

Blood Flow Velocity↗

PubMed1990

Effect of blood filling in intramyocardial vessels on coronary arterial inflow.

The influence of the filling condition of the unstressed volume (UV) of intramyocardial vessels on the diastolic coronary arterial pressure-flow relationship was analyzed. UV is defined as the blood volume at zero transmural pressure. In seven anesthetized, paced dogs with induced heart block, coronary artery inflow was occluded so that blood in the UV was displaced into the coronary vein by myocardial contraction. After pacing was turned off, coronary perfusion pressure was increased stepwise to seven target pressures (20-90 mmHg). After reperfusion, left anterior descending coronary arterial (LAD) flow reached an initial quasi-steady level, but great cardiac venous (GCV) flow was absent (UV-unfilled phase). With reappearance of the GCV flow (UV-filled phase), LAD flow decreased to a final steady level. Pressure-flow relationships during both phases were linear (r = 0.97-0.99). The inverse of the slope of the pressure-flow relationship during the UV-filled phase, 0.69 +/- 0.08 mmHg.min.ml-1, was significantly higher than that during the UV-unfilled phase, 0.55 +/- 0.06 mmHg.min.ml-1 (P less than 0.01), although the zero-flow pressure intercepts were similar (18.9 +/- 1.8 mmHg for UV filled vs. 19.9 +/- 2.2 for UV unfilled). These results indicate that diastolic coronary arterial inflow is impeded by a blood volume within intramyocardial vessels that exceeds the UV.

Animals↗

PubMed1990

[Significance of negative U-waves during anginal attacks: correlation with severity, location and prognosis of coronary stenosis].

Negative U-waves (NU) are not infrequently observed during anginal attacks. Correlations of prevalence of NU and coronary arteriographic findings were observed in 84 patients whose 12-lead electrocardiograms were obtained during anginal attacks. The left anterior descending coronary artery (LAD) was involved in 27 patients, the left circumflex artery (LCX) in 23 and the right coronary artery (RCA) in 34. NU were observed in 44 (52%) of 84 patients with angina; 17 (63%) with LAD, 13 (57%) with LCX, and 14 (41%) with RCA stenosis. The majority (91%) of patients with angina-induced NU had severe (greater than or equal to 90%) coronary stenosis. In the patient group with LAD stenosis, NU were most frequently observed in V4 (59%) greater than V5 (56%) greater than V6 (37%) greater than V3 (33%), while more frequent in V6 (52%) greater than V5 (48%) in the group with LCX stenosis, and in III (29%) greater than a VF (24%) greater than V6 (21%) in the group with RCA stenosis. Thus, the location of the stenosed vessel could be predicted electrocardiographically from the sites of the NU. Coronary revascularization was performed in 10 patients (59%) with LAD stenosis, in nine (69%) with LCX stenosis and in eight (57%) with RCA stenosis. Both anginal attacks and NU resolved after successful coronary revascularization. We concluded that NU proves a highly predictive parameter for detecting and locating significant coronary artery stenosis.

Adult↗

PubMed1990

[A case of acute pericarditis secondary to mediastinitis].

A 45-year-old man who complained of swallowing disturbance and chest pain in inspiration phase was admitted for evaluation of "pericarditis". A chest X-ray film on admission disclosed a wide mediastinal shadow and pleural effusion on the right side. Bilateral tonsils were swollen, and covered with pus. A Computed tomogram of the chest showed a shadow of exudate contained with air in the mediastinum. Mediastinal drainage, tonsillectomy and drainage of fistula from pre-tracheal space to upper mediastinum were immediately performed. Staphylococcus aureus was confirmed from the sputum and mediastinal effusion. Thus, acute mediastinitis was confirmed as an etiological diagnosis of "pericarditis" in this patient.

Acute Disease↗

PubMed1990

[Right pulmonary artery obstruction and pulmonary hypertension secondary to aortitis syndrome].

A 56-year-old woman with aortic arch syndrome and finally right pulmonary artery obstruction secondary to Takayasu's aortitis was presented. She had had a history of visual disturbance and dizziness when she looked upward since 1983. On admission in July, 1984, aortography showed obstruction of the right innominate artery and of the left subclavian artery. Pulmonary arterial pressure, pulmonary perfusion and ventilation images seemed to be normal at that time. After discharge from our hospital, she began in 1987, to be aware of dyspnea on effort. Because of this symptom, she was admitted again in March, 1988. The pulmonary perfusion images showed complete lack of perfusion in the right lung, and arterial blood gas showed hypoxia with 62 mmHg in PaO2, 39 mmHg in PaCO2. Cardiac catheterization confirmed pulmonary hypertension with pulmonary artery pressure of 56/18 mmHg. In conclusion, pulmonary perfusion and ventilation scintigraphy proved to be the best way to clarify the nature of a lesion of the pulmonary artery in aortitis syndrome.

Adult↗

PubMed1990

[Usefulness for evaluation of the left ventricular disorders by apexcardiographic A-wave ratio in patients with hypertrophic cardiomyopathy].

Usefulness for evaluation of left ventricular disorders by apexcardiographic A-wave ratio was studied in 48 patients with hypertrophic cardiomyopathy. These subjects were divided into 3 groups: A-wave ratio less than or equal to 15% (group 1), 16% less than or equal to A-wave ratio less than or equal to 29% (group 2), and A-wave ratio greater than or equal to 30% (group 3). A-wave ratio was found to have a positive correlation with Time constant T (r = + 0.71), left ventricular end-diastolic pressure (r = +0.46), and left ventricular atrial kick (r = +0.55). During exercise, ejection fraction decreased significantly (p less than 0.05) in group 3 as compared to group 1. During treadmill exercise test, rise of systolic blood pressure was significantly (p less than 0.05) poor, and there was a large number of ST depression (p less than 0.05) in group 3. It was recognized by exercise thallium-201 myocardial scintigraphy, that the frequency of perfusion defect was 30% in group 3. In conclusion, high A-wave ratio may strongly suggest impaired left ventricular diastolic function, and, there was correlated to abnormal hemodynamic state during exercise. Apexcardiographic A-wave ratio proved to be useful in patients with hypertrophic cardiomyopathy. It is useful for evaluation of left ventricular disorders.

Adolescent↗

PubMed1990

[A case of silent posterior myocardial ischemia/left circumflex artery obstruction detected by prominent U-wave in right precordial leads].

A 64-year-old woman with a history of hypertension for ten years and of syncope 18 month previously visited our Division of Cardiology on 12 June, 1989. The S4 and mitral regurgitation were audible at the apex, and her electrocardiogram showed ST-depression in leads II, aVF, V5-6 and prominent U-wave (PU) in V1-3 when first seen. Then, she was thought to have a posterior myocardial ischemia. PU in V1-3 diminished whereas T-wave increased after nitrate and Ca++ blocker. Ergometer exercise ECG showed ST-depression in II, III, aVF, V4-6 and PU with decreased T-wave in V2-3 with no apparent symptoms. Simultaneously, Tl-201 myocardial imaging demonstrated a transient posterior defect. A silent posterior myocardial ischemia was, therefore, confirmed. Coronary arteriograms demonstrated subtotal obstruction of the proximal left circumflex artery, and the peripheral site was filled by collaterals from the right coronary artery. Angina-induced PU in the right precordial leads proved to be useful in detection of posterior myocardial ischemia, and this marker may also improve the possibility of detection of silent posterior ischemia.

Coronary Disease↗

PubMed1990

[Two cases of primary artery dissection].

We experienced two cases of primary coronary artery dissection. (Case 1) 55-year-old man had frequent episodes of chest oppression at early morning and midnight. During chest oppression, electrocardiogram showed transient ST-segment elevation in leads II, III, and a VF. Then, he was diagnosed as having angina pectoris. This diagnosis was based on the fact that he presented coronary spastic syndrome. Right coronary angiogram demonstrated an intimal flap and false lumen at segment 3, and primary coronary dissection was confirmed. (Case 2) A 27-year-old woman complained of back pain while taking a bath. Electrocardiogram showed ST-segment elevation and abnormal Q in leads V2, V3 and V4. She was diagnosed as having acute anterior wall myocardial infarction. Presence of coronary artery dissection at segment 6 was identified by left coronary angiogram. Primary coronary artery dissection is clinically diagnosed by coronary angiogram very rarely. Only 27 such cases have been reported. It was speculated that, in case 1, vasospastic angina may be associated with primary coronary artery dissection. Case 2 had primary coronary artery dissection at segment 6 of the left anterior descending artery. Thus, her clinical picture was similar to those of previously reported cases.

Adult↗

PubMed1989

[Acute and chronic effects of bunazosin in patients with congestive heart failure].

The acute hemodynamic effect (right atrial pressure, mean pulmonary artery pressure, pulmonary capillary wedge pressure, cardiac index, heart rate, blood pressure) and neurohumoral response (alpha-ANP, plasma renin activity, aldosterone, angiotensin II) of Bunazosin, oral alpha 1 blocker, was investigated in 28 patients with congestive heart failure at rest and immediately after exercise. Bunazosin reduced alpha-ANP, but, other neurohumoral factors did not change. Bunazosin produced significant hemodynamic improvements both at rest and after exercise. Its chronic effect was also investigated in 11 patients in 28 days after taking oral Bunazosin. Improvement of hemodynamics at acute phase was also preserved at chronic phase without deterioration of neurohumoral factors. It is concluded that Bunazosin may be an effective Balanced vasodilator both at acute and chronic phases in patients with congestive heart failure.

Adrenergic alpha-Antagonists↗