Keiko Nitta

DEVELOPMENT OF INTRACORONARY LOCAL ADHESIVE DELIVERY TECHNIQUE

Acute coronary occlusion may occur in weak coronary atherosclerotic lesions, including dissection, ulceration or thrombus. In some cases of occlusion “bail-out” is performed by using recently developed New Devices. However, these have not yet completely solved the problem to this end, we designed a new method of coronary revascularization, the Intracoronary Local Adhesive Delivery Technique, utilizing antithrombotic and absorbable adhesive injected locally into the fragile and morbid arterial wall using a drug delivery PTCA catheter more flexible than the existing New Devices. This adhesive strengthened and hardened the lesions. In this study, we examined the efficacy of making an adhesive cylinder in arteries of similar size to the coronary, through acute animal experiments using the existing clinical adhesives and drug delivery PTCA catheters and 12 femoral arteries of adult goats. We were successful in forming firm tunnels along the inside of six arteries, infused with approximately 0.04 ml Cyanoacrylate. These tunnels were observed with intravascular ultrasound (IVUS) imaging and evaluated microscopically. These results suggest the feasibility of this method as a new approach for making synthetic resinous stents.

Simultaneous measurement of vibrations on arterial wall upstream and downstream of arteriostenosis lesion and their analysis

Acute myocardial infarction and cerebral infarction are generally known to be caused primarily by the rupture of atherosclerotic plaques. It is thus necessary for clinical treatment to predict the rupture of these plaques. Blood-flow velocity around atherosclerotic plaques increases as the arteriostenosis lesion progresses, resulting in turbulence downstream of the lesion. The resulting change in blood pressure produces shear stress, and change in this stress affects the rupture of the atherosclerotic plaques. Cerebral ischemic paroxysm and cerebral infarction have been reported to occur in a high percentage of cases in which inner vessel diameter has decreased to less than 70% of its original diameter as a result of stenosis. This explains the use of standard ultrasonic diagnostic equipment to measure blood flow in the screening of the carotid arteries. On the other hand, the noise signal radiated from an aneurysm as a result of blood flow has been measured using the bruit sensor used to diagnose cerebrovascular diseases. Many unsolved problems with regard to the relationship between noise and turbulence in blood flow remain, however. Here, small vibrations on the arterial wall were measured transcutaneously and analyzed both upstream and downstream of the atherosclerotic plaque of a human carotid artery. Characteristics of the resultant vibrations upstream of the stenosis clearly differed from those downstream of it. These results should prove useful in predicting the rupture of atherosclerotic plaques.

Simultaneous measurement of vibrations on the arterial wall downstream and upstream from an atherosclerotic lesions

In the literature, it has been reported that cerebral ischemia paroxysm and cerebral infarctions occurs with high percentages when the inner diameter is decreased less than 70% due to a stenosis. The most primary reason of these events is rupture of atherosclerotic plaques of the carotid artery. However, it is difficult to noninvasively predict the rupture. For solving this problem, the authors have investigated the influence of blood flow on the atherosclerotic plaque by transcutaneously measuring small vibrations caused by the pulsatile flow on the arterial wall. In this paper, small vibrations on the carotid arterial wall are measured and analyzed for patients with atherosclerosis and for healthy subjects. From in vivo experimental results, high frequency components were present in the resultant small vibrations on the wall of downstream from the atherosclerotic plaque. Moreover, from experiments using a silicone tube with small pressure sensors, it is found that there is close relationship between the vibrations and inner pressure for both cases with and without an artificial stenosis. These results might open the possibility to predict rupture of atherosclerotic plaques in future by measuring the small vibrations of the arterial wall.

Evaluation of Wall Motion Abnormality by Comparing Values of Cardiac Output Obtained by M-Mode and Doppler Echocardiography : Parameter Revealing Wall Motion Abnormality in Stress Echocardiography

Dobutamine and dipyridamole stress echocardiographies are both well able to detect myocardial ischemia resulting from coronary diseases by recognizing the regional wall motion abnormality (WMA). Here we report a method for describing WMA in detail. In pharmacological stress echocardiography, because of difficulties in recognizing the two-dimensional pattern, accuracy sometimes depends upon the skill of the operator. Two stroke volumes obtained using the M-mode and Doppler methods were examined to detect abnormal regional cardiac function by the dipyridamole stress test. Stroke volume obtained by the M-modereflects regional cardiac function and that estimated from the outflow using the Doppler methodreflects total cardiac function. These two stroke volumes were compared in normal subjects and patients with coronary-diseases. The results indicated consistent discrepancies between these two stroke volume in the ischemic hearts as a results of coronary stenosis, whereas changes in stroke volumes in the normal subjects showed the same tendency. This method of combining information about the regional and total functions is thus useful in examining the WMA and regional cardiac function, although it can not be applied to subjects whose stroke volume does not increase under stress.

Sign of wall motion abnormality observed in wall thickness change, excursion, and stroke volume obtained by M-mode: The parameter revealing wall motion abnormality in stress echocardiography (2)

To improve the evaluation of regional wall motion abnormalities (WMA) during stress echocardiography, the parameters of the wall thickness change, excursion and stroke volume, with time-dependent changes in two regional portions of the interventricular septum and the posterior wall evaluated with M-mode ultrasonography are proposed. Response to the dipyridamole stress test was studied in two normal subjects and eight subjects with coronary disease. Regional wall motion and stroke volume were measured, and the results were compared with results obtained with coronary angiography, 2-D echography, and radioisotope scintigraphy. In normal subjects, these parameters showed only monotonous change with the passage of time. In patients with coronary artery disease, however, discrepancy in wall thickness and excursion between the interventricular septum and the posterior wall appeared within 1 to 3 minutes after the start of the test. Thus, despite the limitation of the examined area imposed by use of M-mode, the motion of the interventricular septum and the posterior wall described the details of WMA and an ischemic state.

Analysis of blood flow in the heart chambers by the stream‐function method based on the ultrasonic Doppler technique

For visualizing blood flow in the human heart noninvasively, the stream‐function method based on the ultrasonic Doppler technique was introduced. In this method intracardiac blood flow is displayed as a two‐dimensional streamline distribution pattern. In normal hearts, blood flow in the left ventricle during systole is displayed as a fan‐shaped streamline pattern converging from the whole ventricular wall toward the outflow tract, and in diastole the streamline distribution shows fan‐shaped divergence from the left atrium toward the whole ventricular wall. The fan‐shaped streamline distribution is considered to reflect the uniform contractability and extensibility in the whole ventricular wall. On the other hand, in infarcted hearts with regional asynergy in the left ventricle, the streamline pattern is remarkably different. In systole, the streamline pattern at the normokinetic portion is the same as that in normals, but in the infarcted portion, the streamlines show a crooked pattern caused by the inflo...

Differentiation of transiently ischemic from infarcted myocardium by Thallium-201 exercises scintigram after active ergometer rehabilitation

It has been frequently reported that while myocardial viability is neglected in conventional methods of diagnosis such as left ventriculography, ECG, and exercise thallium-201 myocardial scintigraphy (Ex-Tl), revascularization often results in improving left ventricular wall motility. In the present study, the authors contrived a method to accurately evaluate the viability ot the myocardium by means of exercise rehabilitation, and tested the method in clinical cases. Among patients with myocardial infarction, we selected a patient with negative viability in the diseased area as determined by chronic ECG, left ventriculography (LVG), coronary angiography and Ex-Tl. This patient went through two weeks of active exercise rehabilitation gauged with an ergometer, and was then re-examined by Ex-Tl. After the evaluation, revascularization was performed for the patient who demonstrated viability of the infarcted myocardium in EX-T1 after rehabilitation, and significant improvement in contractility was shown in the chronic LVG. These findings indicate that our method of detecting potential viability of the infarcted myocardium is of clinical significance.