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.