UHF-ECG data acquisition and analysis
A VDI monitor (Ventricular Dyssynchrony Imaging monitor, ISI Brno,
Cardion, FNUSA, CZ, 2018) was used to record and analyze the 5 kHz
14-lead ECG signals with a 3 nV resolution and a frequency range of 1.5
kHz. UHF-ECG data were collected during 2–3 minutes of the RV apical,
cSp, mSp, anterior wall, and lateral wall pacing at 100–120 beats per
minute. Signal processing and UHF-ECG map construction are described in
detail elsewhere [6]. To describe the
time course of depolarization propagation in the ventricles, the centers
of mass (Mxc) under specific leads (i.e., Vx) were determined. Mxc was
calculated as the center of mass of UHF-QRS amplitudes above the 50
percent threshold of the baseline to peak magnitude. To quantify LV and
RV dyssynchrony, time delays from the earliest center of mass (first
activation) to M8c and M1c were measured (LVLWd and RVLWd,
respectively). To describe the duration of LV lateral wall
depolarization, the time delay between M5-8c (V5-8d) was measured –
Figure 3. The onset and the end of the QRS complex were marked manually
using custom-made software, providing high-resolution QRS signals.
Global QRS durations (QRSd) were measured from the earliest to the
latest deflection in any of the 12 leads (V7 and V8 were excluded from
QRSd calculations). During ventricular pacing, the beginning of the QRS
was measured from the highest amplitude of the pacing artifact.