Relationship of myocardial substrate characteristics as assessed by myocardial perfusion imaging and cardiac reverse remodeling levels after cardiac resynchronization therapy

Background Cardiac resynchronization therapy (CRT) can provide cardiac reverse remodeling (RR), which may include mechanical reverse remodeling (MRR) and/or electrical reverse remodeling (ERR). However, uncoupling of MRR and ERR is not uncommon, and the underlying mechanisms are not clear. This study aimed to evaluate the relationship of myocardial substrate characteristics as assessed by myocardial perfusion imaging (MPI) and cardiac RR post-CRT. Materials and methods Forty-one patients (26 men, mean age 66 ± 10 years) with heart failure received CRT for at least 12 months were assigned to three groups according to their levels of RR: I, MRR + ERR (ESV reduced ≥15 % and intrinsic QRS duration reduced ≥10 ms); II, MRR only (ESV reduced ≥15 %); and III, non-responder (the others). All the patients also underwent MPI under transient CRT-off to evaluate the intrinsic myocardial substrates, including myocardial scar, LV volumes and function, systolic dyssynchrony, and activation sequences. In addition, ventricular tachycardia (VT) and ventricular fibrillation (VF) detected by the CRT devices during follow-up periods were also recorded. Results Quantitative analysis of MPI showed that there were significant differences for scar burden [15.9 ± 9.5, 26.8 ± 16.1, and 45.6 ± 15.1 % for group I ( n = 15), II ( n = 16), and III ( n = 10), respectively, p