Larger spatial ventricular gradient magnitude is associated with higher rates of response to cardiac resynchronization therapy

Figures

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  Figure 1. Illustration of the SVG and QRS area vectors. The SVG (green) is defined as the vector sum of the QRS area (blue) and T-area (red) vectors from the VCG, which is created from projection of the 12-lead ECG into the orthogonal X, Y, and Z directions. On the left is an example of calculating the X component of the SVG (SVGx) by measuring the area under the X VCG lead QRST complex. The Y and Z SVG components are similarly obtained by measuring areas under the Y and Z QRST complexes. SVG magnitude is calculated as the length of the SVG vector, = SVGX2+SVGY2+SVGZ2. QRS area is defined as the magnitude of the QRS area (blue) vector. See Supplemental Methods for further details. Adapted with permission from Isaza et al.17 ECG = electrocardiogram; SVG = spatial ventricular gradient; VCG = vectorcardiogram.

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  Figure 2. Histograms of SVG magnitude (A) and QRS area (B) stratified by CRT response. White bars represent CRT responders and black bars represent CRT non-responders. Gray bars are overlap between black and white bars. CRT = cardiac resynchronization therapy; SVG = spatial ventricular gradient.

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  Figure 3. Adjusted predicted probability of CRT response across the range of SVGmag values in 10 mV∗ms increments calculated using marginal standardization. The line represents the point estimate for the predicted probability of CRT response at a specific value of SVGmag, and the gray shaded area is the 95% confidence interval. Each 10 mV∗ms increment was associated with a significant increase in probability of CRT response (P < .012 for all increments). CI = confidence interval; CRT = cardiac resynchronization therapy; SVG = spatial ventricular gradient; SVGmag = SVG magnitude.

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  Figure 4. CRT response by SVGmag tertiles (A) and QRS area tertiles (B). For SVGmag (A), there was a significant linear trend across increasing tertiles (P = .003), but this was not present for QRS area (B; P = .10). CRT = cardiac resynchronization therapy; ORadj = adjusted odds ratio; SVG = spatial ventricular gradient; SVGmag = SVG magnitude.

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  Figure 5. Scatterplot relationship of SVG magnitude and QRS area. Blue dots indicate individual data points. The red line and gray area represent the best-fit line and 95% CI. CI = confidence interval; SVG = spatial ventricular gradient.