Assessment of Dyssynchronous Wall Motion During Acute Myocardial Ischemia Using Velocity Vector Imaging
Kasumi Masuda, MSc,
Toshihiko Asanuma, MD,
Asuka Taniguchi, MSc,
Ayumi Uranishi, MSc,
Fuminobu Ishikura, MD, FACC,
Shintaro Beppu, MD, FACC*
Division of Functional Diagnostic Science, Graduate School of Medicine, Osaka University, Suita, Osaka, Japan.
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Figure 1 End-Diastolic and End-Systolic Short-Axis Images in a Representative Dog
The short-axis images at baseline and during stenosis and occlusion of the left circumflex artery (LCx). In this dog model, the center of the LCx region is located at the 2 to 3 o’clock position of the short-axis view (wall thickness in the center of the risk area is indicated by arrows). Note that end-systolic wall thickness seemed to be preserved during stenosis.
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Figure 2 VVIs at Mid-Systole and MVO at Baseline and During Stenosis and Occlusion
The velocity vector images (VVIs) in the same dog as that shown in Figure 1. At mid-systole, inward velocity vectors became smaller in the risk area during occlusion but were not reduced during stenosis. At mitral valve opening (MVO), inward velocity vectors were revealed in the risk area during occlusion. Even during stenosis, outward velocity vectors were clearly reduced in the risk area. The transducer icon represents a reference point for calculation of radial velocity.
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Figure 3 Profiles of Radial Myocardial Velocity
Profiles of radial velocity from peak R on the electrocardiogram throughout 1 cardiac cycle in the same dog as shown in Figures 1 and 2. Positive values represent inward wall motion and negative values represent outward wall motion. Yellow and orange velocity profiles are derived from the risk area and the normal perfused area, respectively. Although peak systolic radial velocity (VSYS) in the risk area decreased during occlusion, it did not change during stenosis. In contrast, radial velocity at mitral valve opening (VMVO) gradually increased in proportion to the severity of ischemia. AVC = aortic valve closure; MVO = mitral valve opening.
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Figure 4 Receiver-Operating Characteristic Curve Analysis
Receiver operating characteristic curves of the percent change in wall thickening (%WT), peak systolic radial strain, VSYS, and VMVO for the detection of occlusion and stenosis from values in the risk area only and the ratio between values in the normal and risk areas. The VMVO parameter could detect myocardial ischemia with better sensitivity and specificity than %WT, peak systolic radial strain, and VSYS. Abbreviations as in Figure 3.
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Figure 5 Comparison of MCE and VVI
Images at MVO derived from myocardial contrast echocardiography (MCE) and VVI during occlusion of the left circumflex artery in a representative dog. The area indicating inward velocity vectors at MVO corresponded closely with the contrast defect area derived from MCE. Abbreviations as in Figure 2.
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Figure 6 Spatial Extent of Post-Systolic Inward Motion Detected by VVI
Relationship between the spatial extents of the risk area derived from MCE and the post-systolic inward motion detected by VVI during coronary occlusion. The spatial extent of post-systolic inward motion detected by VVI significantly correlated with that of the risk area with a linear regression. Abbreviations as in Figures 2 and 5.
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