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Assessment of Dyssynchronous Wall Motion During Acute Myocardial Ischemia Using Velocity Vector Imaging

Division of Functional Diagnostic Science, Graduate School of Medicine, Osaka University, Suita, Osaka, Japan.

^_* Reprint requests and correspondence: Dr. Shintaro Beppu, Division of Functional Diagnostic Science, Graduate School of Medicine, Osaka University, 1–7 Yamadaoka, Suita, Osaka 565–0871, Japan. (Email: beppu{at}sahs.med.osaka-u.ac.jp).

Objectives: The purpose of this study was to investigate the diagnostic value of velocity vector imaging (VVI) for detecting acute myocardial ischemia and whether VVI can accurately demonstrate the spatial extent of ischemic risk area.

Background: Using a tracking algorithm, VVI can display velocity vectors of regional wall motion overlaid onto the B-mode image and allows the quantitative assessment of myocardial mechanics. However, its efficacy for diagnosing myocardial ischemia has not been evaluated.

Methods: In 18 dogs with flow-limiting stenosis and/or total occlusion of the coronary artery, peak systolic radial velocity (V_SYS), radial velocity at mitral valve opening (V_MVO), peak systolic radial strain, and the percent change in wall thickening (%WT) were measured in the normal and risk areas and compared to those at baseline. Sensitivity and specificity for detecting the stenosis and occlusion were analyzed in each parameter. The area of inward velocity vectors at mitral valve opening (MVO) detected by VVI was compared to the risk area derived from real-time myocardial contrast echocardiography (MCE). Twelve image clips were randomly selected from the baseline, stenosis, and occlusions to determine the intra- and inter-observer agreement for the VVI parameters.

Results: The left circumflex coronary flow was reduced by 44.3 ± 9.0% during stenosis and completely interrupted during occlusion. During coronary artery occlusion, inward motion at MVO was observed in the risk area. Percent WT, peak systolic radial strain, V_SYS, and V_MVO changed significantly from values at baseline. During stenosis, %WT, peak systolic radial strain, and V_SYS did not differ from those at baseline; however, V_MVO was significantly increased (–0.12 ± 0.60 cm/s vs. –0.96 ± 0.55 cm/s, p = 0.015). Sensitivity and specificity of V_MVO for detecting ischemia were superior to those of other parameters. The spatial extent of inward velocity vectors at MVO correlated well with that of the risk area derived from MCE (r = 0.74, p < 0.001 with a linear regression).

Conclusions: The assessment of VVI at MVO permits easy detection of dyssynchronous wall motion during acute myocardial ischemia that cannot be diagnosed by conventional measurement of systolic wall thickness. The spatial extent of inward motion at MVO suggests the size of the risk area.

Abbreviations and Acronyms   AVC = aortic valve closure   CI = confidence interval   LAD = left anterior descending artery   LCx = left circumflex artery   LV = left ventricule/ventricular   MBF = myocardial blood flow   MCE = myocardial contrast echocardiography   MVO = mitral valve opening   ROC = receiver operating characteristic   VMVO = radial velocity at mitral valve opening   VSYS = peak systolic radial velocity   VVI = velocity vector imaging   WT = wall thickening