Evaluating multisite pacing strategies in cardiac resynchronization therapy in the preclinical setting

Figure 1. Schematic overview of paced locations on the porcine epicardium, showing the 2 multielectrode bands (2×30 and 2×22 electrodes) around the right ventricle (RV) and left ventricle (LV). Individual electrodes are illustrated by dots. Large red dots indicate electrodes that have been used in any pacing mode (single or dual). Green and purple stars indicate examples of dual LV paced configurations, resembling either multipoint pacing (MPP) (vertically aligned) or multizone pacing (MZP) (horizontally aligned). All nonpaced electrodes were used for electrical mapping.

Figure 2. Acute effects of different left ventricular (LV) pacing sites during biventricular pacing (BiVP). A: Typical examples of 3-dimensional epicardial activation maps in the same porcine heart during BiVP. Lateral LV pacing sites provide better resynchronization over anterior or posterior sites. Compared within the same segment, activation times and sequence are comparable between basal and mid-level pacing sites. The apical region is not depicted due to the absence of electrodes. B: Reduction in dyssynchrony parameters for LV anterior/posterior (A/P) vs lateral (Lat.) sites (top) and for basal vs mid-level sites (bottom) during conventional BiVP. ∗P <.05 vs lowest reducing segment or level. IVED = interventricular electrical dyssynchrony; LVAT = left ventricular total activation time; TAT = total activation time.

Figure 3. Hemodynamic response per experiment and correlation with activation time. A: Lowest and highest acute hemodynamic response (AHR) to biventricular pacing (BiVP) in the 8 individual experiments (numbers along the horizontal axis). White bars represent the lowest AHR. Gray bars represent the highest AHR. B: Correlation between normalized LVdP/dtmax and reduction in total activation time for the individual left ventricular (LV) sites during BiVP. Values were normalized to the maximum of the individual experiment.

Figure 4. Three-dimensional activations maps of the epicardium during left bundle branch block (LBBB), biventricular pacing (BiVP), multizone pacing (MZP), and multipoint pacing (MPP) in the same heart. Left: Activation patterns during LBBB (top) and BiVP (bottom), during which the LV is paced from the anterolateral wall. Center: MZP with small (top) and large (bottom) interelectrode distance. Right: Activation maps during MPP with small (top) and large (bottom) interelectrode distance. IVED = interventricular electrical dyssynchrony; LVAT = left ventricular activation time; TAT = total activation time.

Figure 5. Resynchronization during BiVP, MZP, and MPP. Reduction in TAT (A) and increase in LVdP/dtmax (B) during BiVP, MZP, and MPP, expressed as percent of left bundle branch block for all pacing combination (left) and for the first and fourth interelectrode distance quartiles (right). ∗P <.05 vs baseline. Abbreviations as in Figure 4.

Figure 6. Effect of left ventricular (LV) pacing locations on acute hemodynamic effect during multiple LV pacing. Representative 3-dimensional epicardial activation maps of the ventricles during BiVP (A, B) and multiple LV pacing (C, D) in the same heart. A, B: Configurations yielding the lowest and highest acute hemodynamic response (AHR), respectively. C: In an attempt to increase the initial AHR, a second pacing site was added in the delayed activated anterolateral area of A, resulting in the activation map shown. D: Effects of the simultaneously paced combination of A and B. RV = right ventricle; other abbreviations as in Figure 4.

Figure 7. Acute hemodynamic response during multiple left ventricular (LV) pacing based on initial acute hemodynamic and electrical response during biventricular pacing (BiVP). Relative increase in LVdP/dtmax compared to baseline during BiVP, multipoint pacing (MPP), and multizone pacing (MZP), distinguishing between single initial LV pacing sites with upper 25%, middle 50%, and lower 25% change in LVdP/dtmax (A) and total activation time (B). Values are given as mean and SD. ∗P < .05 vs BiVP.