(A and B) Conduction velocity was decreased at 400 ms and 300 ms cycle length in PLA after 3 weeks of ventricular tachypacing, but not in LAA. (C and D) Conduction inhomogeneity was increased at NSR, 400 ms, and 300 ms cycle length in PLA after 3 weeks of ventricular tachypacing, but not in LAA. (E and F) Representative examples of activation maps in the PLA and LAA, respectively. Data are represented as mean ± SEM. *P < 0.05, **P < 0.01, ***P < 0.001. Repeated measures 2-way ANOVA with Bonferroni adjusted within cycle comparisons. HF, heart failure; PLA, posterior left atrium; LAA, left atrial appendage.