Mean ± standard error of (A) ventricular effective refractory period, (B) QT interval, and (C) QT interval at the functional refractory period, pacing from the RV (left panel) and LV (right panel) at cycle lengths of 260 ms, 240 ms, 220 ms, 200 ms, 180 ms, 160 ms, and 140 ms, in both the RV (black) and BIV (gray) groups, after 4 weeks of pacing.