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Figure 1 Method of Assessing Dyssynchrony With Wall Thickness Analysis by Cardiac CT
(A) Left ventricular (LV) model displaying short axis slices with endocardial (white) and epicardial (red dots) casts. (B) Endocardial (red) and epicardial (green) tracing of 1 short-axis image, segmented into 6 standardized segments. Left ventricular wall thickness is depicted as the radial distance between the endocardial and epicardial contours (yellow lines). (C) Serial short axis images depicted at 10% phase increments of the cardiac cycle at 1 slice level of the mid-ventricle. Representative graphs showed the time-to-maximal LV wall thickness at 1 ventricular slice in (D) a healthy "control" with EF 66%; (E) "HF-narrow QRS patient" with nonischemic cardiomyopathy and EF 31%; (F) "HF-wide QRS patient" with ischemic cardiomyopathy, EF 33%, and LBBB; and (G) "HF-wide QRS patient" with nonischemic cardiomyopathy, EF 19%, and LBBB. The graphs displayed the wall thickness of the 6 standardized segments of the LV myocardium over 1 cardiac cycle at a single ventricular slice level. The time-to-maximal wall thickness of the 6 segments is more variable in the HF-wide QRS patients than control and HF-narrow QRS, suggesting a greater degree of dyssynchrony. A = anterior; AL = anterolateral; AS = anteroseptal; CT = computed tomography; EF = ejection fraction; HF = heart failure; I = inferior; IL = inferolateral; IS = inferoseptal; LBBB = left bundle branch block.
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