The percent modulation (medians ± SE) at TVs of 0, 250, 500, and 750 ml, computed across all animals (n = 10), for body surface leads (A), unipolar leads (B), near-field bipolar leads (C), far-field bipolar leads (D), and RV-CS leads (E). For every lead configuration, as the TV increases, the percent modulation also increases. The data present significant variability among the different lead configurations.