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Biomedical subjects

E Ino-Oka

Publications and source records attributed to E Ino-Oka.

At least 19 recordsLinked to original sources
PubMed2001

Evaluation of the severity of chronic heart failure by the reactivity of peripheral vessels.

We developed a method to evaluate the severity of chronic cardiac failure by Doppler image analysis. Doppler images of the whole arterial lumen were consecutively recorded on video tape and the power spectrum (sum of intensity multiplied by frequency) of each frame was considered as an index of the blood flow volume (VI). The right brachial artery was occluded for 15-60 seconds by a occluding cuff, and was released quickly. The VI was determined until the VI returned to the level at rest and total VI was calculated as an O2 repayment. The O2 repayment rate (R-Rate) was calculated as a ratio of the O2 repayment divided by total VI during interruption. The cardiac function was evaluated by sub-maximal exercise using bicycle ergometer and was compared with the R-Rate. The subjects were 22 patients (18 males and 4 females) with chronic cardiac failure of NYHA class I (9), class II (6), class III (4), class IV (3) and 12 healthy controls. R-Rate was almost unchanged by the duration of occlusion and showed positive correlation with exercise capacity. R-Rate decreased as the class of NYHA advanced. In conclusion, determination of reactive hyperemia can be used for objectively evaluating the severity of cardiac failure. Doppler sonography; cardiac failure; reactive hyperemia; peripheral circulation

Aged↗
PubMed2000

Efficacy of anti-anginal drugs in the treatment of angina pectoris associated with silent myocardial ischemia: importance of quantitative Holter ECG data for patient activity.

METHODS: We evaluated the clinical efficacy of transdermal nitroglycerin (NTG-TTS), a patch application of a nitrate, in the treatment of 27 patients with angina pectoris who had asymptomatic myocardial ischemic (SMI) attacks, using a double-blind cross-over method. Evaluation was made using Holter ECG and patient activity data. RESULTS: In frequency and duration of continuation of SMI episodes, no significant differences were noted between the observation and placebo treatment periods, while the values of both these parameters were decreased significantly in the active drug treatment period compared with those in the observation and placebo treatment periods. Critical heart rate, the heart rate at the initiation of ST-segment depression, was significantly higher during the period of active drug treatment than during the placebo treatment and observation periods. In SMI frequency index, which was determined by adjusting the SMI frequency for the number of steps taken, there were no significant differences between the 3 periods. The SMI time index was significantly lower in the active drug treatment period than in the observation period. CONCLUSIONS: These results indicated that the clinical evaluation of the efficacy of anti-anginal drugs against SMI should take into consideration individual patient activity data.

Administration, Cutaneous↗
PubMed1996

Diagnosis of silent myocardial ischemia using ambulatory electrocardiographic monitoring with pedometer, analysis of heart rate, and ST loop in ambulatory electrocardiogram.

BACKGROUND: It has been suggested that episodes of silent myocardial ischemia (SMI) might influence the prognosis of patients with ischemic heart disease, as its consequences are similar to those of myocardial ischemia accompanied by pain. Ambulatory electrocardiogram (ECG) is generally employed in diagnosis as well as in evaluation of clinical efficacy in patients with SMI, but problems related to its application remain because of the difficulty in differentiating between nonischemic and ischemic ST-segment depressions and because of the absence of data concerning body movement. METHODS AND RESULTS: We developed a method for simultaneously recording onto magnetic tape both the ECG chart and pedometer count, as well as a program which enables semi-automatic analysis of the heart rate (HR)-ST relationship. This new method was employed to record ambulatory ECG along with pedometer count for a total of 70 patients, consisting of 53 with coronary heart disease who were shown to have ischemic heart disease, and 17 with various heart diseases in whom coronary angiography revealed no coronary stenosis. The HR-ST relationship was assessed for periods during which steps were recorded by the pedometer, that is, when patients were confirmed to have been under exertion effort. Patients demonstrating the following findings were diagnosed as true positive for SMI: the ST segment level did not decline until HR increased to a certain threshold, and the rate of change in the ST-segment level noted thereafter was -0.025 mm/beats/min or lower; or the ST-segment depression induced by effort continued even after discontinuation of exercise, after which time HR began to decrease, and the HR-ST loop consequently described a counterclockwise rotation. Evaluation of the HR-ST relationship based on these criteria revealed excellent results, as demonstrated by values of 79.2% for sensitivity and 94% for specificity. CONCLUSION: Our newly developed method of assessment of the HR-ST relationship via analysis of simultaneous data from an ambulatory ECG and a pedometer appears to be time saving, highly objective, and useful with regard to the diagnosis of SMI and evaluation of the therapeutic effect of drugs in patients with ischemic heart disease.

Aged↗
PubMed1987

Effects of changes in afterload impedance on left ventricular ejection in isolated canine hearts: dissociation of end ejection from end systole.

To examine how end systole differs from end ejection and also whether the slope of the end systolic pressure-volume relation can be approximated to that of the end ejection pressure-volume relation, nine isolated, perfused, paced canine hearts ejecting into a hydraulic loading system that simulated the aortic input impedance of a dog's arterial tree were studied. To measure left ventricular volume changes the heart was placed in a plethysmograph. Peripheral resistance (Rp) and arterial compliance (C) were independently varied from 1.9 (Rp = 1.9) to 3.3, 6.4, and 9.6 X 10(8) Pa.m-3.s (Rp run) with a constant value of compliance 1.3 X 10(-9) Pa-1.m3 (C = 1.3), and from C = 0.4 to C = 0.8, C = 1.3 and C = 2.3 (C run) with a constant value of resistance (Rp = 6.4). Five pressure-volume loops were obtained by changing the end diastolic volume at each value of compliance and peripheral resistance. It was clearly shown that ventricular ejection continued after end systole and the time duration between end systole and end ejection became longer with increasing arterial compliance (24(4) at C = 0.4 vs 49(4) ms at C = 2.3, p less than 0.001), while the time duration between end diastole and end systole was constant regardless of afterload impedance change. Regarding the left ventricular pressure-volume relation the end systolic relation was almost linear (r greater than or equal to 0.98) and the slope was not significantly affected by change in any afterload impedance tested. End ejection pressure-volume relation was also linear (r greater than or equal to 0.97) and the slopes in the peripheral resistance and compliance runs were lower than those of the end systolic pressure-volume relation in each corresponding run. The former slopes decreased at smaller values of Rp or larger values of C--namely, 4.4(0.6) at Rp = 9.6 vs 3.6(0.6) at Rp = 1.9, p less than 0.05; 4.8(0.6) at C = 0.4 vs 3.1(0.5) mmHg.ml-1 at C = 2.3, p less than 0.001. Thus it is concluded that end ejection is usually different from end systole and the time difference between them is affected by changes in arterial compliance. In addition, the slope of end ejection pressure-volume relation was dependent on the changes in afterload impedance and cannot be approximated to that of the end systolic pressure-volume relation.

Animals↗
PubMed1986

A comparison of ST segment deviation and calculated solid angle during acute regional ischemia in the isolated canine heart at precordial, epicardial and intramyocardial lead surfaces.

Although solid angle analysis has been considered to be reasonable for explaining the distribution of ST segment deviation following ischemia, it has not been tested fully, especially for ST segment changes in various sites at different lead surfaces. Thus, we investigated the applicability of solid angle theory to the mechanism of ischemic ST segment deviation at intramyocardial, epicardial and precordial leads. We used seven isolated, coronary perfused, isovolumic contracting canine hearts in a homogeneous cylindrical volume conductor. ST segment potentials from 246 electrodes were continuously measured during left circumflex coronary artery occlusion for five minutes. The ischemic boundary was obtained from a postmortem angiography, and the solid angle subtended by the ischemic boundary was calculated at every electrode site. Despite the difference between epicardial and precordial ST segment potential distributions, there was a high correlation between measured ST segment potential and calculated solid angle at epicardial (r = 0.86 +/- 0.05, 0.77-0.93), precordial (r = 0.93 +/- 0.05, 0.84-0.99), and intramyocardial leads (r = 0.95 +/- 0.03, 0.91-0.99). We conclude that solid angle analysis can be used to approximate the distribution of ischemic ST segment deviation at different lead surfaces in acute ischemia.

Animals↗
PubMed1986

Effects of preload alteration on the degree of ischemia and function of ischemic myocardium under constant mean aortic pressure, coronary perfusion pressure and heart rate in isolated perfused canine heart.

We examined the effects of preload alteration on global and regional (i.e., non-ischemic and ischemic areas) function in the presence of regional myocardial ischemia and on the degree of ischemia using 18 isolated, metabolically supported canine left ventricles. For this purpose, cardiac output (CO), systolic segment length change (SL), myocardial CO2 tension (PmCO2) and ST level of epicardial ECG were measured at 3 levels of left ventricular end-diastolic pressure (LVEDP), i.e., approximately 7 (low LVEDP), 11 (middle LVEDP), and 16 mmHg (high LVEDP) without and with left circumflex artery (LCx) stenosis under a constant mean aortic pressure (90 mmHg), mean coronary perfusion pressure (90 mmHg) and heart rate. In the Pre-ischemic stage, CO and SL increased significantly when LVEDP was elevated in a stepwise fashion by changing the height of the reservoir connected to the left atrium. There were no significant changes in PmCO2 or ST level. On the other hand, with LCx stenosis, CO did not show a subsequent increase at higher LVEDPs (i.e., from 796 +/- 103 ml/min at middle LVEDP to 931 +/- 153 ml/min at high LVEDP). Furthermore, there was no significant SL response in the LCx area following alterations of LVEDP, although there was considerable lengthening of end-diastolic length. Both increased PmCO2 and ST level of the LCx area, following LCx stenosis, further increased significantly with elevation of LVEDP. These results suggest the possibility that considerable elevation of LVEDP worsens the degree of ischemia and does not significantly augment ischemic regional myocardial function or global function, while mild elevation of preload improves or tends to improve simultaneously regional ischemic and global functions without aggravating the ischemic injury significantly. Therefore, we conclude that the preload level is quite important in managing ischemia induced myocardial dysfunction.

Animals↗
PubMed1986

The influence of changes in the size of ischemic region on ST-segment potential distribution in isolated canine hearts.

In order to investigate how a change in the size of a ischemic region is reflected in ST-segment mapping studies, we produced two different sizes of ischemic regions by occluding proximal or distal portions of the left circumflex artery for five minutes, using ten isolated canine heart preparations. We examined the relationship between the geometry of the ischemic region and ST-segment potential distribution on the epicardial surface and that in the "precordium", in which the heart was suspended. The extent of the ischemic region was reflected differently on epicardial and "precordial" sites, in that the magnitude of epicardial ST-segment elevation decreased (p less than 0.001) while the "precordial" one increased (p less than 0.01). In the epicardium the degree of ST-segment elevation was almost uniform over the ischemic region, whereas in the "precordium" it was maximal at sites overlying the center of the ischemic region and progressively decreased approaching the periphery. However, frequent occurrence of intraventricular conduction disturbance was observed near the center of the ischemic region. As a result, the magnitude of epicardial ST-segment elevation near the center became larger than in the periphery. These results suggest that the classical solid angle theory provides a useful approximation of the ST-segment deflection in very acute ischemic phase, until development of the intraventricular conduction delay.

Animals↗
PubMed1986

Effects of major coronary artery stenosis on the pressure-flow relationship of an adjacent intact coronary artery branch in isolated supported canine left ventricle.

We investigated whether the relationship between the mean left anterior descending and septal coronary blood flow and the mean perfusion pressure varies with left circumflex coronary stenosis. We used excised, perfused canine heart preparations (n = 10), in which variables to influence the myocardial oxygen demand and supply relation can be fairly well controlled. The results showed that coronary blood flow in the adjacent, non-stenosed coronary artery increased significantly following LCX stenosis; this increased flow was found at the same values of heart rate, left ventricular end-diastolic pressure and perfusion pressure, as those in the preischemic state. Moreover, this increased flow was also observed when the values of peak left ventricular pressure and pressure-length loop area were similar between the pre-ischemic and ischemic states. Thus, contributions of neurohumoral factors or alterations in mechanical factors determining the myocardial oxygen demand and supply relation are negligible. This increased flow may be important in maintaining overall cardiac function in cases of acute coronary stenosis or coronary occlusion.

Animals↗
PubMed1985

A new indirect method for measurement of sinoatrial conduction time and sinus node return cycle.

We developed a new indirect method for the measurement of sinoatrial conduction time (SACT) and the sinus node return cycle (SRC) with a transvenous catheter technique. Two early premature stimuli, at intervals 50 msec longer than the effective refractory period (ERP), were given to the right atrium. These early stimuli were followed by eight constant stimuli. The interval of the constant stimuli was a little shorter than the basic cycle length (BCL). The return cycle A1Ar was measured and plotted on the abscissa; the next interval ArA3, was measured and plotted on the ordinate. This was called the "base point". A new stimulus, A2, was then added to the train of stimulations, first at a point simultaneous with Ar. It was then shifted toward the last constant stimulus at 10-20 msec intervals until A2 met the ERP. The relationship between A1A2 and A2A3 was obtained by the repetition of the procedures with various A1A2 intervals. It had two zones, compensatory and non-compensatory. We postulate that the atriosinus conduction time of the last of the eight stimuli was equal to that of A2 when the stimulus A2 first captured and reset the sinus nodal pacemaker cells, as indicated by the transition point of the two zones. Based on this supposition, SACT and SRC could be measured as the intervals from the base point to the transition point and from the transition point to the eighth stimulus, respectively.

Aged↗
PubMed1985

Effects of coronary artery stenosis on left ventricular end-ejection pressure-ejected volume relationships in isolated perfused canine hearts.

We investigated the behavior of the left ventricular end-ejection pressure-ejected volume relation with and without left circumflex coronary stenosis in isolated perfused canine hearts. To change ventricular afterload pressure, the peripheral resistance of the hydraulic model attached to the aortic root of the excised hearts was changed in a stepwise fashion to five different levels. The end-ejection pressure-ejected volume relationship was nearly linear in both pre-ischemic and ischemic states. The slope changes following left circumflex coronary stenosis differed among the hearts used in the present study, and there was no significant difference in average slope (n = 10) between the pre-ischemic and ischemic states (i.e., -7.4 +/- 1.0 and -8.4 +/- 1.2 mmHg/ml, respectively). Therefore, the, slope of the relation was not useful in judging the presence of depressed ventricular function induced by coronary stenosis. In contrast, the ejected volume axis intercept decreased significantly from 16.5 +/- 1.1 ml to 13.6 +/- 1.1 ml (p less than 0.05) with regional ischemia.

Animals↗
PubMed1984

A high-pass phaseless filter for eliminating low-frequency ECG noise during exercise and its clinical application to automatic analysis of the heart rate and ST segment level.

We developed a new technique to eliminate low-frequency ECG noise by the use of a specially designed high-pass phaseless filter. The phaseless filter was tested by computer-simulated ECG signals and it proved to be highly effective in eliminating ECG noise without any significant deformation of the ST segment level. The maximum distortion of ST segment level at 0.8 Hz cut off frequency of this filter is equivalent to the distortion of the usual ECG Amp having 0.1 Hz cut off frequency (JIS). Furthermore, studies of the stabilized ECG recordings during exercise, which became possible by using the phaseless filter, enabled us to develop a method of automatic analysis of the heart rate-ST segment level relationship during and after exercise. The submaximal exercise ECG test was done on 78 ostensibly healthy men. The heart rate (X axis) and three points on the ST segment levels (Y axis) were plotted automatically on an X-Y recorder. Although a great variety of patterns were drawn, we could discern clearly different patterns for normal subject and those with typical ischemic heart disease. Further analysis of this relationship will undoubtedly contribute to the detection of ischemic heart disease.

Autoanalysis↗
PubMed1984

The effect of heart rate and left ventricular end-diastolic pressure on the direction of ST segment displacement in acute ischemia.

The correlation between the ST segment displacement and coronary blood flow in various hemodynamic conditions was studied. Five isolated, isovolumic contracting canine hearts were used. The left main and the right and left circumflex (LCx) coronary arteries were cannulated and perfused with support dog's arterial blood. Four pairs of Ag-AgCl ECG electrodes were attached to the epicardium and subendocardium in the LCx perfused area. Heart rate and left ventricular end-diastolic pressure (LVEDP) were controlled by means of right atrial electrical pacing and infusion or withdrawal of arterial blood into the left ventricle, respectively. LCx flow was reduced by 75, 50, 25% of the control level under the condition of 200 beats/min of heart rate and 20 mmHg or 5 mmHg of LVEDP, and ECGs were recorded. The ST segment elevation was observed in epi- and subendocardial lead ECGs when LCx flow was reduced from 110 +/- 27.5 ml/min/100 g to 72 +/- 3 ml/min/100 g under the condition of normal LVEDP (5 mmHg) and a high heart rate (200 beats/min), whereas the same degree of reduction in LCx flow under the condition of high LVEDP (20 mmHg) and high heart rate (200 beats/min) resulted in an epicardial ST segment depression associated with marked subendocardial ST segment elevation. The results suggest that the coronary flow reduction with a higher LVEDP will induce subendocardial ischemia, whereas the same degree flow reduction with a normal LVEDP induce transmural ischemia.

Animals↗
PubMed1983

Effects of afterload reduction on global left ventricular and regional myocardial functions in the isolated canine heart with stenosis of a coronary arterial branch.

We examined the effects of graded reduction of afterload on the global left ventricular and regional myocardial functions as well as coronary hemodynamics in hearts with regional ischemia. We used isolated, paced canine hearts that were loaded with a hydraulic system that simulated the aortic input impedance of the dog's arterial tree. The loading conditions could be quantitatively and sequentially changed by the reduction of the systemic vascular resistance of the hydraulic system, while the preload was kept constant using a variable-height reservoir connected to the left atrium. The heart was perfused with arterial blood from a support dog. Mean coronary perfusion pressure was maintained equal to mean aortic pressure (AoP) by a servo-controlled pump. Then, the left circumflex branch was constricted to an approximate 50% flow reduction of the preischemic control condition. The myocardial lengths at ischemic and nonischemic regions were measured with two pairs of ultrasonic crystals. In the hearts without ischemia, cardiac output continued to increase, from 535 +/- 14 to 1181 +/- 74 ml/min (p less than 0.01), as mean AoP decreased fom 111 +/- 4 to 52 +/- 3 mm Hg (p less than 0.01), although mean coronary blood flow decreased by approximately 50%. During regional ischemia, at control pressures, performance of the ischemic region diminished from 0.94 +/- 0.15 to 0.77 +/- 0.15 mm (p less than 0.05). With a small decrease in afterload, from 98 +/- 6 to 86 +/- 3 mm Hg, performance improved slightly as in the normal region. With a larger reduction in afterload, from 86 +/- 3 to 55 +/- 6 mm Hg, performance of the ischemic region decreased from 0.77 +/- 0.15 to 0.61 +/- 0.15 mm (p less than 0.05) while cardiac output increased. Thus, there appears to be a bimodal change in performance: a baseline performance, perfusion pressure-mediated decrease and a second, afterload-modulated change.

Animals↗
PubMed1982

Mechanical interactions between four heart chambers with and without the pericardium in canine hearts.

By using excised postmortem hearts obtained from 15 mongrel dogs with the pericardium intact, we investigated mechanical interactions between the four heart chambers from the standpoint of ventricular pressure-volume relationships. The interactions investigated were those between (1) the atrium and the ventricle, (2) the right ventricle and left ventricles, (3) the atrium and one ventricle vs. the other ventricle, and finally (4) the left and right atrium and the right ventricle vs. the left ventricle. For these purposes, we inserted compliant balloons into the four heart chambers without injuring the pericardium, i.e., we incised the base of the atria which was not covered with the pericardium. We obtained the right and/or left ventricular pressure-volume relationships under a constant pressure in three other heart chambers by changing the height of the reservoir connected to each balloon. As a result, both ventricular pressure-volume relationships were hardly affected by an increase in the atrial pressure ranging from 5 to 30 cm H2O with the pericardium removed, although the ventricle became less compliant due to an increase of the same magnitude of the opposite ventricular pressure. On the other hand, the effect of an increase in atrial pressure was distinct with the pericardium intact. Also, all mechanical interactions were enhanced dramatically with the intact pericardium. Thus, the pericardium plays an important role in these mechanical interactions, especially when the filling pressures of all heart chambers increase simultaneously. Clinically, these findings may be important to understanding ventricular functions as related to various heart disease-especially acute heart failure.

Animals↗
PubMed1982

A comparison of left ventricular volume-pressure relations of excised perfused canine hearts in isovolumic contraction, arrest and fibrillation.

The purpose of the present investigation was to study the effects of various conditions such as beating, arrest and fibrillation on left ventricular (LV) diastolic compliance. In coronary-arterially perfused canine isolated hearts, LV volume-pressure (v-p) relations for both inflation and deflation were obtained by infusing and withdrawing a saline. The v-p curves of inflation and deflation were both sigmoidal, but the resultant v-p relations for deflation produced a shift to the left inflation curves, showing hysteresis between inflation and deflation in three ventricular states. The effect of arrest or fibrillation, especially of fibrillation, on LV distensibility was discernible, and the resultant v-p relations produced a marked shift to the right, showing an apparent decrease in LV volume (LVv) at a given filling pressure. It was concluded that it is very questionable to identify the stiffness of the beating heart with the non-beating heart.

Animals↗
PubMed1982

A continuous and quantitative analysis of the uneven distribution of myocardial blood flow in dogs using a distribution function of the clearance time constant.

A continuous and quantitative analysis of the uneven distribution of coronary blood flow was accomplished in anesthetized open-chest dogs using the distribution function of the hydrogen (H2) clearance time constant. The distribution function was derived by analysing the H2 washout curves in the coronary sinus which were obtained by the H2 clearance method, using platinum electrodes placed in the coronary sinus. Twelve to seventeen platinum electrodes were employed to obtain simultaneous measurements of the regional myocardial flow before and after stenosis of the left anterior descending coronary artery. Theoretically, the H2 washout curves in the coronary sinus could be interpreted as a function with multi-exponential characteristics, represented by an equation similar to the Laplace transform of the distribution function of the H2 clearance time constant. Therefore, we assumed that such an equation would represent the uneven distribution of coronary blood. We obtained the distribution function by using an approximation method to solve the integral equation and we employed digital computation to increase the resolution. Before stenosis of the left anterior descending coronary artery, the log distribution function curves with respect to the H2 clearance time constant were roughly symmetrical in terms of the maximum peak in the time constant. After stenosis of the left anterior descending coronary artery, the log distribution function had two peaks and the range of distribution was much larger than that before coronary stenosis. Our findings may prove to be valuable as a technique to estimate continuously and quantitatively the heterogeneous distribution of myocardial blood flow.

Animals↗