| Background and objective: With the rising incidence of coronary heart disease , pursuing a new method to detect myocardial ischemia become more and more imperative. Abnormal wall motion is a characteristic manifestation of myocardial ischemia. Doppler tissue imaging (DTI) and anatomic M-mode imaging were two new echocardiography techniques developed in the 1990s. Recently, people placed the sample volume in the conventional DTI velocity imaging and got the space average velocity value of the myocardial tissue in corresponding sample volume. Link the points denoted the mean velocity by computer and get the tissue velocity curve. Then people made integral postprocessing of the myocardial longitudinal motion velocity and derived displacement index of myocardium during a period of time. When it is showed in curve mode, it is called tissue tracking curve. When the value of longitudinal displacement is color coded and then displayed in a series of cross sectional apex longitudinal views, it is called tissue tracking imaging. With the tissue6tracking imaging, abnormal wall motion could be observed directly and quickly. Anatomic M-mode is a technique through which one or multiple independent cursors can be placed and rotated freely in the two dimentional images and the motion of the corresponding ventricular wall can be revealed in M-mode curve. The motion of left ventricular wall after the flow of left circumflex coronary artery gradually quantitively decreased was observed with dypyridamole stressed DTI and anatomic M-mode techniques in the research in order to evaluate the new techniques in detecting the myocardial ischemia and give reference gists to the clinical diagnosis of myocardial ischemia. METHOD: 13 healthy hybrid canine were anesthetized. After routine preparation and operation, exposed the canine's heart and separated the LCX. The electromagnetic flow-meter and the coronary artery constriction implement were installed 5mm far away from the beginning of the LCX in turn and the electrocardiogram was connected. Various degree myocardial ischemia models were made by regulating the coronary artery constriction implement according to the LCX flow. In each target confined condition, dypyridamole was added in two steps, first 0.56mg/kg(small dosage), then 0.28mg/kg(large dosage) after four minutes. After small dosage was added, image collecting must be finished within 4 minutes while after the large dosage was added there must be 15 minutes interval before the beginning of next confined condition. All the images were stored in magnetic compact disc. The images were collected by VIVID 7 echocardiographic apparatus manufactured by GE company. The frequency of transducer is 1.5-5MHz. The workstation accompanied with VIVID7 was adopted to analyze the images. The index to be analyzed: DTI (systolic longitudinal displacement and peak velocity), Anatomic M-mode (short axisdirection displacement) . All the results were showed in the form of mean 眘tandard variation. Statistic analysis was performed by SPSS software. Results: The result of DTI (1) In the basal condition, each myocardium segment along the longitudinal direction had various systolic motion displacement and peak velocity. Not only displacement but also velocity showed that the degression tendency from mitral valve annulus to apex. (2)In the ischemia conditions, the longitudinal direction systolic displacement and peak velocity decreased. With the sharpening of the ischemia degree, the motion amplitude and velocity of the regions supplied by LCX decreased gradually while the motion of healthy regions were not affected evidently. Use of dypyridamole made the fall of displacement and systolic peak velocity of the ischemia region more obvious while made those of healthy region augment slightly. When the flow of LCX cut down to 75% combined with large dosage dypyridamole stress, the remarkable difference of longitudinal direction systolic displacement and peak velocity was showed between the ischemia state and basal state (P<0.05) .It wa...
|
PDF Full Text Request