Electrocardiographic imaging
Noninvasive cardiac mapping was obtained from 14 patients in whom recent (<3 months) cardiac computed tomography or magnetic resonance images were available. Two patients were excluded (one due to atrial fibrillation during mapping and one because of insufficient image quality). As expected, LV activation was delayed in comparison to RV activation at intrinsic rhythm, while CRT activation led to a more synchronous activation pattern in the LV (Figure 4 ). At intrinsic rhythm, the biventricular activation time was 90±17 ms. Both FOI configurations achieved the shortest biventricular activation times (72±14 ms and 77±18 ms for SPP-FOI and MPP-FOI, respectively), and they were significantly shorter than the activation times during intrinsic rhythm (P=0.005 and P=0.04, respectively). No differences were observed between the activation times during intrinsic rhythm and the MPP strategy alone (83±19 ms, P=0.30) (Figure 5 ). The biventricular activation times according to ECGI showed a good correlation with the QRS durations determined via ECG (r = 0.58; Figure 6 ).