Eiji Ino-Oka

Mechanical interaction between the ventricles

SummaryWe investigated ventricular interaction by the use of six excised, perfused, canine hearts. In this preparation, we could change the filling pressure of the right and left ventricles independently, thereby breaking the normal series-pump arrangement. We found that mechanical ventricular interaction exists in diastole and in systole. Namely, not only decreased diastolic ventricular compliance, but also the reduced performance in either ventricle was found, when the opposite ventricular pressure was increased. Thus, when the opposite ventricular filling pressure increases, we suspect that systolic ventricular function of either ventricle will be depressed significantly by these two factors; i.e., the Frank-Starling effect due to decreased ventricular diastolic volume following decreased diastolic ventricular compliance, and the depressed systolic ventricular function. Clinically, these findings may be important in considering the mechanism of the occurrence of simultaneous reduced performance of both ventricles in cases when only one side of the ventricle is affected hemodynamically and its filling pressure is greatly increased in various pathological states such as heart failure.

The Effects of Physical Activity and Autonomic Nerve Tone on the Daily Fluctuation of Blood Pressure

The effects of daily activity and autonomic nerve tone on the fluctuation of ambulatory blood pressure were studied in hypertensive patients. The autonomic nerve tone was measured by frequency domain analysis of the RR interval. Physical activity was evaluated by a walk count, converted to a walk rate (WR), recorded using a digital Holter ECG fitted with an accelerometer, with simultaneous monitoring of blood pressure (Bp). Average values of the WR, H and L/H components were calculated for the 15 min. period just prior to Bp monitoring. The relationship between the average WR, H and L/H values and the Bp was determined by a linear regression analysis. Hypertension was classified into three types, autonomic nerve dominant (AN), exercise dominant (EX), and irregular (IR), based on a high correlation coefficient between Bp and either H or L/H (AN type), between Bp and WR (EX type), or no significant correlation between Bp and any of the parameters (IR type). Of the thirty hypertensive patients studied 11 were classified as AN, 12 as EX, and 7 as IR. Patients of the EX type had significantly lower Bp than patients in the other two classes. Furthermore, all of the IR type patients showed non‐dipper type hypertension, suggesting that the Bp regulation mechanisms were impaired. The results suggest the significance of simultaneous monitoring of physical activity and autonomic nerve function at the time of Bp monitoring.

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.

Effects of OPC-8212, a new positive inotropic agent, and dobutamine on left ventricular global and ischemic regional functions and coronary hemodynamics under coronary artery stenosis

Summary: We have investigated the effects of OPC-8212, a new positive inotropic agent, and dobutamine, a known cardioselective inotropic agent, on global left ventricular (LV) and ischemic regional functions in 14 excised canine hearts with a flow-limiting stenosis of the left circumflex coronary artery (LCX) (i.e., 20–25% of control flow). OPC-8212 infusion (n = 7) under LCX stenosis improved cardiac depression [i.e., peak LV dP/dt increased from 1,295 ± 143 mm Hg/s to 2,669 ± 266 mm Hg/s (mean ± SEM) (p < 0.001)], while myocardial ischemic injury, assessed by myocardial CO2-tension and electrocardiogram (ECG)-ST changes, improved (i.e., ΔCO2-tension and ECG-ST deviation decreased from 21.1 ± 3.6 mm Hg and 3.8 ± 0.6 mV to 13.3 ± 2.8 mm Hg (p < 0.01) and 2.0 ± 0.7 mV (p < 0.05), respectively). On the other hand, dobutamine infusion (n = 7) further increased myocardial CO2-tension and ECG-ST deviation [i.e., ΔCO2-tension and ECG-ST deviation increased from 14.4 ± 4.2 mm Hg and 2.5 ± 1.2 mV to 29.0 ± 6.0 mm Hg (p < 0.01) and 4.9 ± 1.0 mV (p < 0.01), respectively]. At the same time, peak LV dP/dt clearly improved, but to a lesser degree; from 1,425 ± 153 mm Hg/s to 2,393 ± 245 mm Hg/s (p < 0.001). There was also an increase in percent systolic segment shortening of each corresponding area as with OPC-8212. As a result, the two inotropic drugs had different effects on ΔCO2-tension (p < 0.0001) and ECG-ST deviation (p < 0.0006) in the ischemic region. Thus, this new drug, OPC-8212, seems to be potentially useful in the management of heart failure induced or accompanied by ischemic heart disease.

Pressure-length loop in the ischemic segment during left circumflex coronary artery stenosis and its modification by afterload reducing in excised perfused canine hearts

SummaryBy using excised perfused heart preparations, we investigated the regional myocardial functions in the presence of a flow-limiting coronary stenosis of the left circumflex coronary artery (LCX) (approximately a 50% flow reduction of pre-ischemic control), as well as global cardiac functions during afterload reducing, while keeping left ventricular end-diastolic pressure (LVEDP) and heart rate constant. After inducing the LCX stenosis, cardiac output (CO), peak left ventricular pressure (peak LVP) and stroke work (SW) decreased from pre-ischemic control values, i.e., 81.1±3.2%, p<0.005, 88.1±3.8%, p<0.02 and 72.2±5.7%, p<0.005, respectively (n=7), whereas pressure-length (P-L) loop areas changed as follows; ischemic control values of the left anterior descending coronary artery (LAD) and LCX regions were 96.6±6.0%, n.s. and 72.6±9.0% of pre-ischemic control, p<0.02, respectively.Following afterload reducing with LCX stenosis, CO increased gradually, while the ischemic regional function started to further aggravate, and the initial point of further ischemic aggravation obtained in this experiment occurred at 63.5±6.9 mm Hg of mean aortic pressure (AoP). These results suggested that the increase of total cardiac function such as CO following afterload reducing was probably induced at the expense of aggravated regional ischemia. Therefore it was concluded that the treatment of ischemic myocardium by reducing afterload pressure should be done very carefully.

Evaluation of Carotid Atherosclerosis from the Perspective of Blood Flow Reflection

Detection and prevention of atherosclerosis at an early stage is important for its prevention. The aim of this study was to propose a valid and highly reliable index for the evaluation of carotid atherosclerosis or carotid function. Images of carotid Doppler wave profiles were processed using an image processing software, and the relative fluctuation in blood flow was calculated from the luminance in one cardiac cycle. Frequency analysis was performed and up to 10 time components of basic frequency (f1) were indicated. The evaluation functionαwas estimated by calculating the ratio of the sum of components f3–f10 against the f1 + f2 components. Blood pressure of the finger was continuously measured using Finapress during passive postural change from the supine to the standing position, the baroreceptor function was evaluated by the frequency method, and the plaque score was measured by ultrasound tomography. The influence of factors such as arterial compliance, blood vessel resistance, and heart rate on this index was studied using electric circuit model simulation. The subjects were 33 patients (18 men, 15 women) who had various types of atherosclerotic disease and hypertension. The average age was 67.3 + 12.2 years. The results showed that index α had a strong negative correlation with age and plaque score, and a weak positive correlation with baroreceptor function. Simulation results supported the clinical result. We proposed a new index to evaluate carotid atherosclerosis without blood pressure measurement using the carotid Doppler method. It is a potential index for detecting atherosclerosis of local arteries such as the carotid.

Circadian Variation of the Myocardial Ischemic Threshold in Patients with Ischemic Heart Disease

Purpose. Circadian variation of the heart rate (HR) at the myocardial ischemic threshold was compared with that of the HR at the sympathetic tone threshold in 16 cases of effort angina pectoris. Methods. The high (0.15–0.40 Hz, Hf) and low (0.03–0.15 Hz, Lf) frequency spectral components were extracted every twenty seconds, using frequency domain analysis of the RR interval recorded by a 24-hour Holter ECG with an accelerometer. HR-Hf data collected every five minutes were plotted as the X-Y coordinates, and a two-compartment analysis was performed. The HR at the autonomic tone threshold was then determined at the intersection point of the lines. A loop of the HR-ST segment was drawn during walking to determine the ischemic threshold at which heart rate ischemic ST segment depression began and circadian variation was observed. Results. The circadian rhythm at the sympathetic tone threshold and the HR at the ischemic threshold were high during the day and low at night. The HR at the ischemic threshold was 15–20% higher than that at the sympathetic tone threshold at night but only 9–13% higher during the day. Also, there was a period during which there was no significant difference between the HR at the two thresholds. Conclusion. In comparing circadian variation between HR at the sympathetic tone threshold and HR at the ischemic threshold, there was a period during which there was no significant difference between the HRs. This might suggest a period in which a high incidence of cardiac ischemic attack is likely. This information could provide a feasible indicator for appropriate exercise training for patients with ischemic heart disease.

Attempt of Quantitative Analysis of Visual Evaluation for 123I-BMIPP Myocardial Scintigraphy Images

Abstract We developed a new technique to quantitatively analyze visual evaluation single photon emission computed tomography (SPECT). Short axis tomograms and color scales were computer scanned. The scales were divided into 25 parts; numbers of each hue pixel were scored 0–100%. Short-axis images were divided into eight equal partitions, numbers of hue pixels distributed in each partition were scored, and total scores were obtained. Each partition’s radio-isotope (RI) accumulation index was calculated as partition score/highest score. For method validation, scintigrams from each left ventricular phantom part were divided into eight partitions and filled with 123I-BMPP (10–100%). The error between theoretical and calculated concentrations was within 20% in the concentration range of ≥50%, suggesting a good correlation and indicating the method’s validity.

Comparison of Clinical Efficacy of Disopyramide and Mexiletine in Treatment of Premature Ventricular Complexes

Summary19 patients with premature ventricular complexes (PVCs) were administered disopyramide and mexiletine at 300 mg/day in a cross-over comparison of efficacy. The mean daily count of PVCs significantly decreased after both treatments. There was no significant difference between the 2 groups in terms of overall improvement or usefulness. In the global comparison, the usefulness was evaluated as having been higher with disopyramide in 9 patients (47.4%), equal for the 2 drugs in 5 patients (26.3%) and higher with mexiletine in 5 (26.3%). This suggests that these drugs exerted their efficacy by different mechanisms.

The relationship between myocardial oxygen consumption and total work obtained by a new left ventricular model.

SummaryThe relationship between myocardial oxygen consumption (