AIMS:It has been shown that optimizing atrioventricular (AV) and interventricular (VV) delay improves cardiac performance in patients with biventricular pacemakers. However, there is no standard method for optimization available yet. The aim of this study was to compare echocardiographic parameters-displacement imaging, A wave duration, and aortic velocity time integral (VTI)-and acoustic cardiography derived electromechanical activation time (EMAT) using different approaches of AV and VV delay optimization. We tested whether the initial optimization of the AV interval followed by VV optimization at that optimal AV interval or initial optimization of the VV interval followed by AV optimization at the determined optimal VV interval was accurate and consistent, and how this compared to testing every conceivable combination of AV and VV intervals available. METHODS AND RESULTS:A group of 20 patients with biventricular pacemakers was included. Displacement imaging, A wave duration, and aortic VTI were determined at different combinations of AV (100, 150, 200, 250 ms) and VV (RV40, 0, LV40 ms) intervals. If AV duration was determined first, displacement imaging identified the best setting in 8/20, aortic VTI in 10/20, A duration in 13/20, and EMAT in 18/20 patients. With VV duration determined first, the best setting was more difficult to identify regardless of the method used. There was a poor agreement in optimal AV and VV delays of the different methods, and there was no single patient in whom all four methods yielded the same delay combination. CONCLUSION:It is advisable to measure a full grid of AV and VV delays to identify optimal settings rather than optimizing one of the two delays first. Different techniques for delay optimization resulted in different optimal delay combinations.