Quantitative Analysis of Intraventricular Dyssynchrony Using Wall Thickness by Multidetector Computed Tomography
Quynh A. Truong, MD*,*,
Jagmeet P. Singh, MD, DPhil ,
Christopher P. Cannon, MD ,
Ammar Sarwar, MD*,
Khurram Nasir, MD, MPH*,
Angelo Auricchio, MD, PhD ,
Francesco F. Faletra, MD,
Antonio Sorgente, MD,
Cristina Conca, MD,
Tiziano Moccetti, MD,
Mark Handschumacher, BS,
Thomas J. Brady, MD*,
Udo Hoffmann, MD, MPH*
* Cardiac MR PET CT Program, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts
Division of Cardiology, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts
Cardiovascular Division, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts
Cardiocentro Ticino, Lugano, Switzerland
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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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Figure 2 Interobserver Correlation and Bland-Altman Graphs of DI
(A) Interobserver correlation scatterplot of the individual DI measurements by Observer 1 and 2. The solid line is the linear regression line. (B) Bland-Altman graph plotted to assess for bias and limits of agreement between the measurements by Observer 1 and 2. The solid line is the bias (mean of the differences) between the measurements by Observer 1 and 2. The dashed lines are the upper and lower limits of agreement (bias ± 2 SD of bias). DI = dyssynchrony index.
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Figure 3 Box and Whisker Plot of DI Using Changes in LV Wall Thickness of the 3 Groups
Mean DI was significantly different between the 3 groups and was greatest in the HF-wide QRS group, followed by the HF-narrow QRS, and then the control group (152 ± 44 ms vs. 121 ± 58 ms vs. 65 ± 12 ms, respectively; p < 0.0001). HF = heart failure; LV = left ventricular; other abbreviations, as in Figure 2.
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