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Intra-ventricular resynchronization for optimal left ventricular function during pacing in experimental left bundle branch block

^* Department of Physiology, Cardiovascular Research Institute, Maastricht University, Maastricht, The Netherlands

View larger version (29K): [in a new window]   Figure 1 Examples of (A) left ventricular (LV) endocardial activation maps with the activation delay vector indicated by arrows, (B) electrocardiographic tracings, (C) right ventricular (RV) and LV pressure signals, and (D) pressure–volume loops, before and after creation of left bundle branch block. In (B), the earliest and latest LV endocardial activation are indicated by dotted lines. In (C), right ventricular (RV) and LV pressures are normalized to reveal timing differences. The LV endocardial activation maps are presented as bull's-eye plots, with the inner disc representing the LV apex and the outer circle disc representing the LV base (S, A, L, and P indicate the septum and anterior, lateral, and posterior walls, respectively).

View larger version (23K): [in a new window]   Figure 2 Inter-ventricular asynchrony as a function of (A) the paced atrioventricular (AV) delay and (B) the left ventricular–right ventricular (LV–RV) excitation time difference (TVV) during LV apex, biventricular (BiV), and LV lateral wall pacing. The results for anterior and posterior wall pacing were comparable to those for lateral wall pacing.

View larger version (65K): [in a new window]   Figure 3 Examples of left ventricular (LV) endocardial activation maps during left bundle branch block (LBBB) and pacing at various LV sites and excitation time difference between LV and RV (TVVs) smaller than, equal to, and larger than zero. Also presented is an example of LV endocardial activation during right ventricular (RV) pacing at a short AV delay. The black arrows denote the activation delay vectors, the amplitude of which reflects the degree of intra-ventricular asynchrony.

View larger version (21K): [in a new window]   Figure 4 Pressure–volume loops measured with the conductance catheter, showing the short-term effect of pacing during left bundle branch block (LBBB) for left ventricular (LV) apex (left panel) and LV lateral pacing (right panel) at paced atrioventricular delays of 40 and 90 ms. The results for anterior and posterior wall pacing were comparable to those for lateral wall pacing.

View larger version (38K): [in a new window]   Figure 5 Changes in left ventricular (LV) maximum rate of increase in pressure (dP/dtmax) relative to baseline left bundle branch block (LBBB) as a function of the (A and C) paced atrioventricular (AV) delay and (B and D) excitation time difference between LV and right ventricular (TVV) for two experiments during LV apex and LV lateral wall pacing. The results for anterior and posterior wall pacing were comparable to those for lateral wall pacing.

View larger version (26K): [in a new window]   Figure 6 Typical example of the relationship between changes in left ventricular (LV) maximum rate of increase in pressure (dP/dtmax) and inter-ventricular asynchrony (interVA) (A) and intra-ventricular asynchrony (intraVA) (B) during LV apex, LV lateral wall, and biventricular (BiV) pacing with atrioventricular (AV) delays ranging from 20 to 200 ms. The dotted arrows indicate shortening of the AV delay. Data points most remote from baseline left bundle branch block (LBBB) denote the shortest AV delay (20 ms); subsequent points were obtained at a 10-ms increase, except for intraVA. The sign given to intraVA values indicates the direction of the wave front, as indicated above the graphs. The results for anterior and posterior wall pacing were comparable to those for lateral wall pacing.

View larger version (53K): [in a new window]   Figure 7 Values of intra-ventricular asynchrony (intraVA) (n = 5), inter-ventricular asynchrony (interVA) (n = 12), and QRS duration (n = 12) at a maximum increase of left ventricular (LV) maximum rate of increase in pressure (dP/dtmax) (left column) and stroke work (SW) (right column). The mean ± SD of pre-left bundle branch block (LBBB) (C) and post-LBBB (LBBB) values are indicated by the patterned bars (one-way analysis of variance followed by Tukey post hoc testing for C vs. LBBB; *p < 0.05 vs. LBBB and C, respectively). The results for anterior and posterior wall pacing were comparable to those for lateral wall pacing.