Electrical dyssynchrony mapping and cardiac resynchronization therapy

There is no clinical methodology for quantification or display of electrical dyssynchrony over a wide range of atrial-ventricular delays (AVD) and ventricular-ventricular delays (VVD) in patients with cardiac resynchronization therapy (CRT). This study aimed to develop a new methodology, based on wavefront fusion, for mapping electrical synchrony. A cardiac resynchronization index (CRI) was measured at multiple device settings in 90 patients. Electrical dyssynchrony maps (EDM) were constructed for each patient to display CRI at any combination of AVD and VVD. An optimal synchrony line (OSL) depicted the AVD/VVD combinations producing the highest CRIs. Fusion of right ventricular paced (RVp), left ventricular paced (LVp), and native wavefront offsets were calculated. CRI significantly increased (p < 0.0001) from 58.0 ± 28.1% at baseline to 98.3 ± 1.7% at optimized settings. EDMs in patients with high-grade heart block (n = 20) had an OSL parallel to the simultaneous biventricular pacing (BiVPVV-SIM) line with leftward shift across all AVDs (RVp-LVpOFFSET = 50.5 ± 29.8 ms). EDMs in patients with intact AV node conduction (n = 64) had an OSL parallel to the BiVPVV-SIM line with leftward shift at short AVDs (RVp-LVpOFFSET = 33.4 ± 23.3 ms), curvilinear at intermediate AVDs (triple fusion), and vertical at long AVDs (native-LVpOFFSET = 85.2 ± 22.8 ms) in all patients except those with poor LV lead position (n = 6). A new methodology is described for quantifying and graphing electrical dyssynchrony over a physiologic range of AVDs/VVDs. This methodology offers a noninvasive, practical, clinical approach for measuring electrical synchrony that could be applied to optimization of CRT devices.