Assessment Of Coronary Microvascular Endothelial Function With Intravenous Myocardial Contrast Echocardiography

Assessment of Coronary Microvascular Endothelial Function with Intravenous Myocardial Contrast Echocardiography An Experimental Study Abstract Objectives To investigate that if coronary microvascular endothelial function could be evaluated with intravenous myocardial contrast echocardiography(MCE) ,coronary microvascular endothelial dysfunction of canine models with diabetics and hyperglycemia without atherosclerosis in coronary arteries were used and the reaction to Ach and NTG on myocardial perfusion changes in time-intensity plots with MCE were observed. Materials and Methods Thirty adult mongrel dogs served as the study animals, and were randomly assigned to three groups. (1) control group (n=1O), (2)hyperglycemia group (n:=lO), (3) diabetes group (n10). Dogs were anesthetized, incubated, and left lateral thoracotomy were performed. After ideal images were acquired at the short-axis mid-papillary muscle level with 2D echocardiography, three different conditions were separately performed with intravenous MCE. (1) baseline (no drug) (2) Ach (administration of Ach) (3)NTG (administration of NTG), and blood samples were taken from coronary sinus for examinations of nitricoxide(NO)~ Endothelin(ET), and radiolabeled microsphere-derived MBF was measured. Hemodynamics were monitored by catheterization throughout the experiment period,While blood sugar and blood-gas analysis were measured every thirty minutes. At the end of the experiment, the dogs were killed by electric shock ,and ~he myocardial -5- specimens were collected for light and electron microscopy examination,and for myocardial blood flow (MBF) measured by radiolabled microspheres The additional myocardial tissues were used to establish on in vitro coronary arteriolar model based on Yo Yuan method, Microscopic observations were performed with the use of a video photometer ,and fluorescent intensity was measured and digitized on-line by IBM PC, The reaction on single arteriole to Ach (100 ~?mol) and NTG (100 i~ mol) ,and perfusion velocity of Fluorescein-labeled perfluorocarbon-fihled microbubbles in myocardial arteriolar and interactions between microbubbles and vascular endothelial cells were observed directly. The indexes derived from time-intensity plots with MCE includeding: Peak intensity (P1), Peak intensity ratio (PIR); time to reach the P1 (Tp), Tp ratio(TpR); halftime to P1(T112) and T112 ratio(T112R) Results 1. Heart rate, blood pressure, blood sugar, and blood-gas changes: There were no changes in heart rate , blood pressure, blood sugar, and blood-gas after administration of microbubble; heart rate and blood pressure reduced after administration of Ach and NTG respectively, blood suga; elevated markedly in diabetes and hyperglycemia groups compared with control group. 2. Parameter changes in Time-Intensity plots: In control group, P1 and PIR sinificantly increased, Tp~ TpR and Tj~~ T112R significantly reduced after administration of Ach and NTG; in hyperglycemia group, P1 and PIR enhanced sinificantly, Tp ~. TpR and T112-~ T1t2R decreased markedly after NTG, but no cha...