TABLE 1.

Summary of different pacing options for CRT non-responders.

Pacing option	Evidence summary for CRT non-responders
AV/VV delay optimisation	Small observational studies—conflicting data Jansen et al., 2006; Ellenbogen et al., 2010; Brabham and Gold, (2013); AlTurki et al., 2019
Multi-point pacing (MPP)	MORE-CRT RCT—no benefit in MPP Leclercq et al., 2019
Multi-site pacing (MSP)	Mechanistic studies—Acute haemodynamic benefit in of MSP in acute haemodynamic non-responders to conventional CRT. Ploux et al., 2014; Sohal et al., 2015; Heckman et al., 2020 No larger studies as yet.
LV endocardial pacing	Small observational studies—Lead-based and leadless endocardial pacing may achieve echocardiographic and clinical response in a significant proportion of non-responders. (van Gelder et al., 2016; Sidhu et al., 2020 SOLVE-CRT study ongoing
Conduction system pacing	Observational studies—HBP, LBP, HOT-CRT and LOT-CRT may give potential improvements in electrical resynchronisation obtained by preserving intrinsic RV activation, yet to be demonstrated in a non-responder population. Vijayaraman et al., 2019; Vijayaraman et al., 2022b; Jastrzębski et al., 2022; Toding Labi et al., 2022