Results
Baseline Characteristics
One-hundred and eighty-two (182) patients were enrolled in 13 centers
across 7 Middle Eastern countries. LV lead implantation was unsuccessful
in 8 (4.4%) patients, 4 (2.2%) withdrew from the study post-implant,
lead dislodgement or system explant occurred in 3 (1.7%), 3 (1.7%)
experienced non-cardiac related death, echocardiography was incomplete
in 2 (1.1%), and 20 (18.4%) were lost to follow-up. Ultimately, 142
patients contributed complete datasets, with 69 and 73 patients
randomized to the BiV and MPP groups, respectively. Baseline patient
characteristics were similar for across both groups and are provided in
Table 1.
The distributions of RA, RV, and LV lead locations are provided in
Figure 1. RA and RV leads were predominantly placed in the RA appendage
(97.8%) and RV apex (85.7%), respectively. From base-to-apex, LV leads
were predominantly placed medially (76.1%), and from
anterior-posterior, LV leads were predominantly placed postero-laterally
(58.5%) or laterally (39.4%).
The distribution of programmed LV cathodes in the BiV group and
programmed LV1 and LV2 cathodes in the MPP group are shown in Figure 2.
The most common LV cathode programmed for BiV patients was D1 (49% of
patients). The most common LV1 and LV2 cathodes programmed for MPP
patients were D1 (65%) and M3 (32%), respectively. Correspondingly,
the most common LV1/LV2 cathode pairs in MPP patients were D1/M3 (24%),
D1/M2 (22%), and D1/P4 (19%). The LV1/LV2 cathode pairs were
associated with an anatomical separation >30 mm in 61% of
MPP patients.
CRT Response Rate
The MPP group demonstrated higher 6-month CRT responder rates than the
BiV group, as shown in Figure 3. The proportion of patients
demonstrating an ESV reduction of 15% or greater was significantly
higher in the MPP group (68.5%, 50/73) than in the BiV group (50.7%,
35/69, P=0.04). The proportion of patients demonstrating an ESV
reduction of 30% or greater (i.e., “super-responders”) was also
higher in the MPP group (39.7%, 29/73) than in the BiV group (27.5%,
19/69, P=0.16). In terms of the combined ESV and EF response criteria,
the proportion of patients demonstrating an ESV reduction of at least
10% in conjunction with an EF elevation of at least 5% was
significantly higher in the MPP group (65.8%, 48/73) than in the BiV
group (44.9%, 31/69, P=0.02).
Reverse Remodeling
The LV reverse remodeling effects of CRT are shown in Figure 4. Patients
in the MPP group experienced a greater reduction in ESV (median
[IQR] = 25.0% [11.5%, 37.2%]) than patients in the BiV group
(15.3% [3.3%, 31.3%], P=0.08). Likewise, patients in the MPP
group experienced greater EF elevations (11.9% [5.5%, 19.7%])
than patients in the BiV group (8.6% [3.7%, 16.9%], P=0.36).
Electrical Synchrony
The impact of CRT on alleviating electrical dyssynchrony can be
quantified by changes in QRS duration, also shown in Figure 4. At 6
months post-implant, patients in the MPP group experienced greater QRS
duration narrowing than patients in the BiV group (15.1% [4.1,
26.0] vs. 13.3% [2.5, 20.9], P=0.17).
NYHA Functional Class
At 6 months post-implant, significantly more patients in the MPP group
experienced an improvement in NYHA functional class (80.8%, 59/73) than
those in the BiV group (60.3%, 41/68, P=0.01), as shown in Figure 5.
Furthermore, more patients in the MPP group improved by at least 2 NYHA
functional class levels (28.8%, 21/73) than those in the BiV group
(16.2%, 11/68, P=0.11).
Impact of Baseline Characteristics on
Response
The potential use of baseline characteristics as predictors of ESV
response was quantified using binomial regression, with results provided
in Figure 6. For patients with BiV therapy, ischemic cardiomyopathy
significantly reduced the odds of ESV response (P=0.02), while age
(P=0.06) and poor NYHA class (P=0.05) both approached significance. In
contrast, those factors were not predictive of response to MPP. For MPP
patients, only gender was a significant predictor (P=0.01). In the MPP
group, male patients made up 54.0% of responders, but 91.3% of
non-responders.