Abstract Body (Do not enter title and authors here): Background. Left ventricular (LV) myocardial fibrosis can be crucial for the electrical wave propagation and thus contribute to left bundle branch block (LBBB) formation. Using a novel specially developed technology we aimed to establish the role of fibrosis in activation parameters in patients with LBBB and indications to cardiac resynchronization therapy (CRT).
Materials and methods. 15 patients (7 male, mean age 59.1±9.8 years) with LBBB underwent late gadolinium enhancement magnetic resonance imaging (LGE-MRI) and novel AI-based 12-lead ECG non-invasive electrical activation mapping (NIAM) prior to CRT onset. LGE-MRI was performed for the reconstruction of fibrosis 3D geometry and calculation of total fibrosis volume (totLVfvol), and LV transmural index (volFibInLV). In NIAM maps total activation time (totalAT), LV (totalLVAT), total LVAT on epicardial and endocardial surfaces (totLVATepi, totLVATendo) were estimated. LV 3D LGE-MRI and NIAM models were merged for semi-automatic segmentation in each patient followed by calculation in each of 17 segments epicardial segment total AT (ΔSegLVepi), endocardial segment total AT (ΔSegLVendo), total segment fibrosis (SegLVfvol) and transmural index (SegLVtransmInd). Latest activated zone segment (LAZ) location was determined.
Results. Mean totLVfvol was 17.4[7.3;53,7] ml and it was not related to totalAT, totalLVAT, totLVATepi and totLVATendo (r=0.18, 0.02, 0.02, 0.52, p>0.05). In segment-by segment analysis fibrosis was variously distributed in LV but its most prominent amount was located in segments 2,3,8,9, 7,and 12. LAZ was typically located in 5^th and 6^th segment in 12 (80%) cases. Its displacement did not depend on the fibrosis in the target segment. Mean SegLVfvol was 3.27[0.53;8.06]ml, SegLVtransmInd was 0.18[0.04;0.42] whereas ΔSegLVepi was 55[42;66], ΔSegLVendo was 44[33;58]. Moderate positive association was revealed between ΔSegLVepi and SegLVfvol (r=0.37, p<0.001), and between SegLVfvol and ΔSegLVendo (r=0.31, p<0.001). Weak positive association between SegLVtransmInd and ΔSeg LVepi (r=0.27, p<0.001), and between SegLVtransmInd and ΔSegLVendo (r=0.211, p<0.001) was detected.
Conclusion. Our results based on novel developed technology of simultaneous evaluation of LGE-MRI and NIAM 3D models have showed that in LBBB patients fibrosis being unevenly distributed in myocardium does not determine the totalAT and LVAT but its value can influence of local AT in segment-by-segment analysis