Interaction between atrial-ventricular and ventricular-ventricular delay in CRT

FUNDING ACKNOWLEDGEMENTS: Type of funding sources: Foundation. Main funding source(s): United Hospital Medical Education and Research Committee, United Hospital Foundation. BACKGROUND: Appropriate programming of atrial-ventricular delay (AVD) and ventricular-ventricular delay (VVD) is critical for delivery of optimal cardiac resynchronization therapy (CRT). However, there is debate over how to determine optimal programming for a given patient. This is complicated by the use of 2 distinct methods of defining the activation timing at a given AVD and VVD used by different device manufacturers. PURPOSE: To describe how electrical dyssynchrony is affected by changes in AVD, VVD and the method used to program AVD and VVD. METHODS: We measured electrical synchrony at multiple combinations of AVD/VVD in 41 patients with underlying left bundle branch block (LBBB) using a novel methodology called electrical dyssynchrony mapping (EDM). Electrical dyssynchrony was quantified by cardiac resynchronization index (CRI), calculated as % change in area under the curve between combinations of 9 anterior and 9 posterior surface electrograms. RESULTS: EDM (Figure 1) shows CRI at multiple combinations of atrial-to-RV-paced, (A-RVp, y-axis) and atrial-to-LV-paced (A-LVp, x-axis) intervals. VVD changes to produce LV preactivation are shown at short and long AVDs using the methods of 2 different CRT device manufacturers: Method 1: fixing A-RVp and shortening A-LVp; and Method 2: fixing A-LVp and lengthening A-RVp. During simultaneous BiV pacing, CRI at short AVD (61.7±20.9) was significantly (p<0.001) greater than at long AVD (46.9±14.0). On average, CRI was significantly greater at short AVD than at long AVD during LV preactivation of 20 or 40 ms (Figure 2). At short AVD, Method 2 resulted in slightly but significantly better CRI at VVD 20 and 40 ms. At long AVD, Method 1 resulted in large and significantly better CRI at VVD 20 and 40 ms. CONCLUSIONS: The interaction between AVD and VVD is complex, and the electrical resynchronization achieved when programming depends on both the AVD at which VVD is programmed, and the programming algorithm used by the device manufacturer. At longer AVDs, Method 1 yields significantly better resynchronization than Method 2 when programming VVD. Studies assessing effects of AVD and VVD programming that involve patients with CRT devices from different manufacturers need to modify programming parameters appropriately in order to accurately interpret results. METHODS: For programming VVD and EDM [Figure: see text] [Figure: see text]