Background: Extracellular volume (ECV) determined by magnetic resonance imaging (MRI) is considered a marker of diffuse myocardial fibrosis and a predictor of mortality. In aortic stenosis (AS), patient ECV increases after aortic valve replacement (AVR). The underlying cause of the ECV increase remains unclear. This study investigates the correlation of ECV with conduction velocity (CV), cell radius (R) and extracellular conductivity in AS patients.
Methods: MRI was performed on 12 AS patients (6 females, 6 males) before, and 3 months after AVR. All patients had a QRS≤110 ms and no scar on late gadolinium enhanced MRI. Computational biventricular models were developed from the MRI data and were paced from 5 activation sites to resemble physiological pattern of ventricular depolarization. Simulations were performed to determine the parameters R and F (extracellular conductivity scaling factor) that matched the model to patient QRS and ECV. Right ventricular (RV) apex pacing was simulated, and CV was calculated from two points on the RV septum. Spearman’s correlation coefficients were calculated to quantify the association between ECV, F, R, and CV. Differences between the time points were assessed by a Wilcoxon’s test.
Results: Higher ECV was found in AS patients post-AVR than pre-AVR (Figure A). No significant changes in QRS and CV were found between the time points (Figure B, C), suggesting there was no substantial increase in diffuse fibrosis. ECV was negatively correlated with R, and not correlated with CV and F (Table). In contrast, CV was positively correlated with R and negatively correlated with F (Table).
Conclusion: Increased ECV after AVR is not associated with a change in CV, suggesting no considerable increase in diffuse fibrosis. Histological studies should be performed to explain the underlying cause of increased ECV in AS patients.