Effect of shortening AVD on SV and dPdtmax, representing the acute response, and mLAP representing the chronic response, starting from LBBB baseline at an AVD of 220 ms and applying BiVP (pink squared line) and nsLBBP (blue triangle line). The left panel shows the results in the presence of LBBB with dilatation and mantained contractility, while the right panel presents the results in the presence of LBBB with dilatation and decreased contractility. The green arrow and green square indicate the increase (for SV and dPdtmax) and decrease (for mLAP) due to pacing, while the orange arrow and orange square represent the increase (for SV and dPdtmax) and decrease (for mLAP) due to AVD optimization. AVD, atrio-ventricular delay; BiVP, biventricular pacing; dPdtmax, maximum rate of pressure change; LBBB, left bundle branch block; LV, left ventricle; mLAP, mean left atrial pressure; nsLBBP, non-selective left bundle branch pacing; SV, stroke volume.