Changes in ejection fraction and pulmonary artery pressure can be influenced by coronary sinus lead position

Abstract

Nowadays cardiac resynchronization therapy can be applied using simultaneous (BiV0) and sequential biventricular pacing (BiVS). This enables pacing with a large number of combinations between atrioventricular (AVD) and interventricular delays (VVD). We hypothesized that determination of the AVD and VVD that result in maximal improvement of pump function, is facilitated by calculating an effective VV-delay (VVeff) characterizing the contribution to resynchronization of paced and intrinsic activation under all conditions. Methods: In 8 canine hearts with chronic LBBB, leading to 17 16% LV hypertrophy and 25 19% LV dilation, BiV0, BiVS and LV pacing were performed with a large number of combinations of AVDs and VVDs. Mechanical interventricular asynchrony (VVmech) was calculated from the timing difference between the upslopes of LV and RV pressure. LVdPdtmax was used as measure of LV pump function. VVeff was calculated as the difference between LV stimulation time and (a) RV stimulation time or (b) time of intrinsic RV activation (RAVDintr), whichever occurred earlier. RAVDintr was determined during BiV0 pacing with incremental AVD, and defined as the AVD at which the shape of the QRS duration changed as a result of loss of full capture. Results: RAVDintr correlated linearly with PQ-time (r 0.84) and was 35 4 ms shorter than PQ-time. Improvement of LVdPdtmax and VVmech at an applied VVD differed depending on the applied AVD and vice versa. However, for all conditions both LVdPdtmax and VVmech related uniquely to VVeff (figure). Maximal improvement in LVdPdtmax was similar between LV, BiV0, BiVS pacing (12.2 5.9%) and occurred at VVeff -7 16ms (NS vs. 0). Conclusion: AVD and VVD have a complementary effect on pump function. Choice of the optimal combination of AVD and VVD can be facilitated by calculation of VVeff using simple surface ECG measurements.