Aim
to assess the relation of focal and diffuse left ventricular (LV) fibrosis to left bundle branch block (LBBB).
Materials and methods
60 patients with dilated cardiomyopathy and LBBB (DCM-LBBB), 50 DCM-nonLBBB patients, 15 patients with LBBB and structurally normal heart (idiopathic LBBB) and 10 healthy volunteers (HV) underwent cardiovascular magnetic resonance (CMR) with late gadolinium enhancement (LGE). LGE LV images were post-proceeded for core scar (CS) and gray zone (GZ) calculation. Diffuse LV fibrosis was estimated on LGE-CMR images with the diffuse intensity ratio (DIR). Endomyocardial biopsy (EMB) was performed in 15(24.6 %) DCM-LBBB and 16 (32 %) non-LBBB DCM patients and allowed the quantification of collagen volume fraction (CVF).
Results
The percentage of CVF correlated with the DIR value in the same segment (r = 0.66, p < 0.001). The value of CVF in EMB and frequency of LGE in both DCM groups was comparable (p = 0.8). In DCM-nonLBBB patients the percentage of CS was significantly higher (4.0[1.6; 11.7]% versus 1.4[0.1;8.5]% in DCM-LBBB patients, p = 0.047), whereas percentage of GZ and total fibrosis in both DCM groups was comparable. DIR value was higher in patients with idiopathic LBBB than in HV (0.54±0.09 versus 0.34±0.1, р<0,001).
Conclusion
Neither focal nor interstitial fibrosis is associated with LBBB in DCM patients. Diffuse inflammation in DCM-LBBB patients may contribute to the progression of systolic dysfunction but is not a cause of LBBB. The increased value of interstitial fibrosis in patients with idiopathic LBBB may reflect latent diffuse process in myocardium inexorably leading to DCM development.
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