Experimental Study Of Optimizing Mechanical Index For Three Ultrasonic Contrast Agents And Quantifying Myocardial Perfusion With Contrast Echocardiography

Objective: To optimize the optimal mechanical index (MI) for three fluorocarbon-contained ultrasonic contrast agents (UCA), and to assess the feasibility and accuracy of myocardial contrast echocardiography (MCE) in measurement left ventricular mass(LVM) and systolic function and to quantify serial changes in myocardial perfusion of left ventricular hypertrophy (LVH) and acute myocardial infarction (AMI) with MCE.Methods: Anesthetized mice were divided into different groups. Optimal condition group devised according to the scheme 3 (UCA) × 3 (mechanic index) of factorial analysis were assessed by MCE quantitatively with parameter PI (peak intensity)and HT(half time). Mice got LVH by abdominal aortic constriction(AC4W group, AC8W group). Ligation of the left anterior descending coronary artery (LAD) was performed in AMI models. 2D and M-mode echocardiography was performed to measure systolic function, in groups before and after intravenous infusion of UCA in part two. The subjective scores graded of contrast effect qualitatively at 0-3 levels were estimated by two independent radiologists. Measuring LVM, assessing systolic function and quantifying myocardial perfusion after intravenous injection with UCA. The values of A (the density of local microvessels), β (local blood flow velocity), A· β (local myocardial blood flow) and PI, TTP(time to peak) were measured with MCE. The corresponding transmural gradients, defined as endocardial-epicardial ratios of A(A-EER), β (β-EER) and A· β (A · β-EER)were also calculated.Results: Two factors both affect the MCE imaging effect, and they have interaction. Improving endocardial and myocardial visualization was detected by MCE. A significant correlation was observed by MCE estimates of LVM and the corresponding anatomic measurements (r =0. 90). There were good correlations between MCE and cardiac catheterization findings for SV(r =0. 86). Area of AMI myocardial by MCE had an excellent correlation with that by pathologic stain (r=0. 87). The parameters of TTP and P -EER were declined in group AC4W. The values of A, P , A ? P , were significantly lowered in group AC8W (P <0. 05). P and A ? P from endocardial layer decreased (P<0. 05), and P - EER, A ? P -EER decreased accordingly(P<0. 05). Perfusion defect were visible and confirmed by flat video intensity-time curves in the infarcted areas. The nonperfused myocardial area, as measured by the contrast perfusion defect, closely approximated the postmortem exclusion of dye. The values of A, P , A ? P , were significantly decreased in the nonperfused myocardial. (P <0.05).Conculusions: Three UCAs had different suitable MI to get optimal application in MCE. MCE can improve the ability to accurately and objectively evaluate LV mass and function. MCE can evaluate the myocardial microvascular perfusion qualitatively and quantitatively. Real-time MCE with low energy has a potential in assessing the transmural distribution of myocardial perfusion and can identify the severity of LVH. Analysis of myocardial perfusion by contrast echocardiography provides quantitative parameters for the assessment of ischemic diseases.