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Figure 3 Differences in Electrical Remodeling and Frequency Dependence Between HSP and CAVB Dogs

In panel A, recordings of ECG leads II and AVR, and left and right ventricular monophasic action potential (LV and RV MAP, respectively) are shown during high-septal pacing (HSP) with a cycle length of 1,000 ms at 0 weeks (left side) and 4 weeks (right side). From top to bottom, RT, QRS, RR, duration of LV and RV MAP, and activation time (all ms) are indicated. Horizontal and vertical calibrations represent 1 s (paper speed 25 mm/s) and 1 mV for ECG recordings and 20 mV for monophasic action potential signals. Graphs in panel B show RT time in CAVB (left side) and HSP dogs (right side) during pacing at cycle lengths between 600 and 1,000 ms. Note that controlling activation with HSP reduces electrical remodeling after AVB. Dashed lines = 0 weeks; solid lines = 4 weeks. For differences in RT between 0 and 4 weeks at the same pacing cycle length within the CAVB and HSP groups, paired Student t tests were used. *p < 0.05 versus 0 weeks. For differences between CAVB and HSP at 600 and 1,000 ms pacing cycle length, 2-way analysis of variance followed by Bonferroni post-hoc test was used. p < 0.05 versus CAVB. Panel C shows values of RT interval (left side) and LV MAPD (right side) in 5 CAVB dogs with consecutive RV apex pacing (solid lines) or HSP (dashed lines). Paired Student t tests were used to analyze differences between RV pacing and HSP at the same pacing cycle length (all p > 0.7). Abbreviations as in Figures 1 and 2.