Purpose: To determine the association between diffuse fibrosis by T1 mapping and mid-wall fibrosis (MwF) by delayed enhancement in patients with aortic stenosis (AS).
Methods: In a prospective study, patients with AS and no myocardial infarction underwent cardiovascular magnetic resonance (CMR) at 3T. Using modified look-locker inversion sequences, T1 maps were generated pre- and 20 min post-contrast (gadobutrol, 0.1 mmol/kg). Contrast volume of distribution (Vd; ΔRmyocardium/ΔRbloodx[1-hematocrit], where ΔR=1/post-contrast T1–1/pre-contrast T1) was measured at the short-axis, mid-cavity level in patients without MwF. In patients with MwF, Vd was measured at the short-axis level of MwF, excluding regions of enhancement. AS severity was assessed with echocardiography [aortic valve area, mean pressure gradient, trans-aortic velocity (Vm)]. Indices of left ventricular hypertrophy were evaluated with CMR [indexed left ventricular mass (LVMi) and mass/volume ratio (M/V; LVM/end-diastolic volume)]. Logistic regression was used to determine the association between Vd and MwF, adjusting for potential confounders.
Results: Sixty patients were studied (70% males; 71±9 years, Vm 3.6±0.9m/s). MwF was identified in 33%. Patients with MwF had higher LVMi (91±22 vs. 79±16g/m2, p=0.03), M/V (1.21±0.22 vs. 1.08±0.19, p=0.02), Vm (3.9±0.7 vs. 3.5±0.9m/s, p=0.04) and Vd (28.7±2.5 vs. 26.7±2.0%, p<0.01). After adjusting for age, gender, AS severity and left ventricular remodeling indices, Vd was independently associated with MwF (odds ratio 1.55, 95% confidence interval 1.04-2.32).
Conclusions: MwF is independently associated with an increased level of diffuse fibrosis. Diffuse fibrosis by T1 mapping is an early marker of myocardial response to ventricular hypertrophy.
