Figure 6.

Preliminary data from Rademakers et al. demonstrating the UHF-ECG activation map and averaged ECG of a CRT recipient before implantation and during various VV interval settings. Red indicates the time (horizontal axis) and location (vertical axis) when most myocardial cells are activated simultaneously. It is noteworthy that QRS duration is relatively short during an LV-RV of 20 ms, whereas the UHF-ECG reveals dyssynchronous activation. In contrast, an RV-LV of 5 ms results in more synchronous activation (ventricular electrical delay, 22 ms). Abbreviations: QRSd = QRS duration, VED = ventricular electrical delay.