Results
A total of 300 different ventricular activations (51 spontaneous
rhythms, 46 c-Sp, 61 m-Sp, 48 RV anterior wall, 48 RV lateral wall, and
46 RV apical captures) were recorded in 51 patients – their
characteristics are shown in Table 1. The average procedural time was 98
± 23 min., and one procedural complication was observed (a pericardial
effusion that resolved spontaneously). Other procedural characteristics
are shown in Table 1. Of 48 RV anterior wall positions, 9 were found to
be septal since they exceeded the 25° angle to the horizontal plane in
the LAO (all of them were classified as RVOT). Of the 60 mSp positions,
30 were classified as RVIT and 30 as RVOT. Two records (one marked as
mSp and one as the lateral wall) were not analyzed since the X-ray
images were not stored. As a result, definitive analyses were performed
on 32 spontaneous rhythms without a bundle branch block (narrow QRS
group), 46 cSp, 69 mSp (30 RVIT, 39 RVOT), 39 RV anterior wall, 47 RV
lateral wall, and 46 RV apical wall captures.
The average height of the position with cSp capture was 40 ± 5% of the
heart silhouette in the RAO. The mean A/V ratio was 4 ± 4%, and in 29
of 46 patients with cSp, the atrial signal amplitude was lower than 0.05
mV on the EGM in the cSp location. A wide range of HV/RBBpoV intervals
was observed (30–83 ms), with an average value of 50 ± 13 ms. There
were seven patients with HV intervals shorter than 35 ms. Their LVLWd
and RVLWd were similar compared to those with HV > 35 ms;
19 ms (10;27) vs 10 ms (7;14), p = 0.14 for LVLWd and 3 ms (−6;12) vs 1
ms (−3;5), p = 0.70 for RVLWd), but QRSd was significantly shorter (126
ms (112;139) vs 141 ms (135;146); p = 0.02). Their UHF-ECG maps with
measured parameters are shown in Supplementary Figure 2.
Conductive system septal pacing showed superior depolarization patterns
compared to all other pacing locations - Figure 4 and Supplementary
Figure 3. QRSd and LVLWd were significantly shorter during cSp
than during RVIT (p <
0.01 for both) and RVOT pacing (p < 0.001 for both). Although
both RVIT and RVOT had virtually the same QRSd (p = 0.99), the LVLWd and
V5-8d were significantly longer for RVOT capture (p < 0.001
for LVLWd and p < 0.05 for V5-8d). cSp capture resulted in
wider QRS complexes compared to the ‘narrow QRS’ group, but RVLWd and
LVLWd were similar (p = 0.2 and p = 0.6 respectively). cSp and RVIT
capture caused the same V5-8d as the spontaneous narrow group (p
> 0.99) – Figure 5 and table 2.
Regarding RV pacing locations without direct conductive tissue
engagement, the shortest LVLWd was observed during mSp, followed by RV
apical (p = 0.02 between them), lateral and anterior wall capture being
the longest. Compared to each of the others, the longest RVLWd was
observed during RV apical capture (p < 0.001). The V5-8d was
significantly shorter in mSp compared to other RV myocardial captures (p
< 0.001 to each of them) – Figure 6 and table 3.