Progress of QRS complex width
In the 77 successful cases (29 with narrow baseline QRS and 48 with wide
baseline QRS), the mean QRS width was significantly reducedversus baseline (141.3 ± 41 vs. 112.7 ± 15.3 ms;P < .001). In the successful cases with a baseline QRS
of <120 ms (14 in HBP and 15 in LBBAP), the paced QRS was
significantly increased (97.3 ± 7.1 vs. 105.5 ± 10.3 ms;P < .001) and the mean QCI was 8.7 ± 10.5% (range,
0-43.4%), with a slightly lower increase in the HBP group (5.2 ± 10.2%
vs. 12 ± 10%; P = .08). Paced QRS width was prolonged in 19
patients, 15 in the LBBAP group and 4 in the HBP group; a QCI of 0 was
obtained in the other 10 patients in the HBP group (7 cases of selective
and 3 of non-selective HBP). Paced QRS remained at ≥ 120 ms and
<130 m in only three patients (1 LBBAP and 2 HBP). Selective
HBP obtained better results than non-selective HBP or LBBAP (Figure 4).
In the 48 successful cases with baseline QRS of ≥ 130 ms (25 in LBBAP
and 23 in HBP), 23 had right bundle branch block (RBBB), 19 had left
bundle branch block (LBBB), and 6 had QRS paced by a previously
implanted device. The QCI was related to age, baseline QRS width,
baseline LVEF, presence of LBBB or RBBB, and the technique (HBP or
LBBAP). In the multiple linear regression, only baseline QRS width (OR
–3.4, 95% CI –0.32 to –0.08; P = .001) and LBBAP technique
(OR 3.8, 95% CI 4.4 to 14.5; P < .001) were retained
as independent predictors. The reduction in QCI was greater with LBBAP
than with HBP and even greater than with conventional CRT in failed
cases (Figure 5).