Differences in left ventricular ejection fraction (LVEF) and geometry between study groups during the 12-week protocol. Progression of (A) LVEF, (B) LV end-diastolic volume (LVEDV), (C) LV end-systolic volume (LVESV), (D) relative wall thickness (RWT), and (E) LV mass index during 12 weeks of follow-up in sham, premature atrial contraction (PAC), and premature ventricular contraction (PVC) groups (mean ± standard error of the mean). Boxes next to individual values represent the median + interquartile range; P < .05 (∗) vs sham, (†) vs PAC, (‡) vs baseline, (§) vs week 4.