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Figure 4 Linear regression analysis depicting the negative inverse relationship between left ventricular (LV) parasternal short-axis fractional area of change (FAC) (%) and paced QRS duration (ms) in 24 young patients who had long-term right ventricle apical pacing, including the mean regression line and regression coefficient (with 95% confidence interval [CI]) of the QRS interval. The slope of the regression line was –0.2 (95% CI of –0.34 to –0.04), p < 0.05, r2 = 0.24, Y = –0.2X + 78.4. Therefore, for every 1-ms increase in QRS duration, the LV FAC decreases by 0.2%.