Rick Schreurs

31 Exploring CRT this has rarely been done may explain the variable results on the best way and clinical effect of AV- and VV-optimization. A possible solution to this problem is the use of ECG or vectorcardiogram variables for optimization, which are both easy to acquire and have considerably lower variability [50]. Intrinsic PQ duration 130ms Intrinsic PQ duration 210ms 230 230 230 50 50 50 50 230 230 50 A-LV (ms) A-RV (ms) A-RV (ms) A-LV (ms) A-RV (ms) Change in LV dP/dt max (%) 0 5 10 0 5 -5 -10 10 0 Change in SW (%) Electrical resychronization (%) Short Long Intrinsic AV RV first LV first Simultaneous AV interval VV interval Septum Free wall RBB + RV pacing electrode LV RV RBB LV pacing electrode RV pacing electrode Activation wave from: A B Figure 6. Changes in resynchronization and pump function after biventricular CRT. A) Schematic representation of interactions between activation wavefronts originating from the RV and LV pacing electrodes and from the right bundle branch (RBB). B) Contour plots of percentage change in LV dP/ dt max (maximal rate of rise of left ventricular pressure; top), stroke work (SW, middle), and electric resynchronization (bottom) in 100 different combinations of atrio-left ventricular (A-LV) and atrio- right ventricular (A-RV) intervals in two different experiments with an intrinsic PQ duration of 130 (left) and 210 ms (right). AV: atrioventricular, VV: interventricular. Panel B reproduced with permission from American Heart Association [46]. CONCLUSIONS CRT successfully improves cardiac function in heart failure patients with LBBB, by resynchronizing the dyssynchronous contraction of the LV. Studies in patients and animals have indicated that the best electromechanical improvement is achieved by selecting the proper site for LV lead placement and by avoiding areas with transmural scarring. The acute effects of multiple pacing locations, endocardial pacing and optimized timing of pacing are superior to conventional CRT, but further research on the long-term effects of these promising approaches is still needed. 2