Rick Schreurs

65 Effective mechanical atrioventricular delay arterial pressure was calculated from the aortic pressure curve. Cardiac output was calculated from the aortic flow probe signal. Optimal AV-delay (AV opt ) was calculated as the AV-delay with the largest relative increase in cardiac output compared to the baseline value. Stroke work was quantified from pressure-volume loops. The A-waves of the LA and RA pressure curves were selected manually and subsequently maximal pressures (LAP max and RAP max ) were calculated. LA and RA dP/dt max were defined as the maximal rate of rise of the A-wave of the atrial pressure curve. Active and passive diastolic filling and diastolic mitral regurgitation (MR) were assessed using the first derivative of the LV volume signal of the conductance catheter. The diastolic phase was defined as the time between the moment of minimal LV volume and the time of LV dP/dt max . Active filling was defined as positive flow that occurred during the A-wave of the LA pressure curve. Passive filling was defined as all positive flow prior to the A-wave. Forward flow was calculated by combining passive and active filling. Diastolic MR volume was quantified as negative flow occurring after the end of active filling. See figure 1 for an overview of all hemodynamic parameters. Figure 1. Experiment animal model setup and hemodynamic parameters. The left figure shows an overview of the measurement in the porcine model. Pacemaker leads were transvenously inserted in the right atrial (RA) appendage and right ventricle and epicardially on the lateral left ventricular (LV) wall. Total AV-block (indicated by the yellow cross) was induced using radiofrequency ablation of the AV-node. Aortic, LV, right ventricular (RV), left atrial (LA) and RA pressures were measured as well as LV volumes. The analysis of signals is shown on the right. The first derivative of the LV volume curve was used to define forward flow over the mitral valve (grey area) and diastolic mitral regurgitation (MR, yellow area). The integral of the aortic flow, measured by a flow probe, was used to quantify forward stroke volume and cardiac output (red area). The vertical grey beam represents the diastolic phase. Interatrial dyssynchrony was defined as the time between RA dP/dt max and LA dP/dt max . Interventricular dyssynchrony was quantified as the interval between the moments of RV and LV dP/dt max , negative values indicating RV pre-excitation. Right (right-eAVD) and 4