Abstract 17191: Bolus Administration T1 Mapping as a Marker of Interstitial Myocardial Fibrosis in Severe Aortic Stenosis

Abstract

Introduction: Aortic stenosis (AS) is associated with increased interstitial myocardial fibrosis (IMF). This is detectable by cardiovascular magnetic resonance (CMR) after gadolinium infusion. T1-mapping-derived partition coefficients (λ) and extracellular volume fractions (Ve) have also been shown to correlate with IMF after a simple bolus administration of gadolinium. We hypothesized that the λ and Ve would also detect interstitial expansion in severe AS patients compared to healthy controls and that these measures would correlate with abnormal myocardial strain using a high temporal-resolution tagging sequence. Methods: A Modified Look-Locker Inversion Recovery (MOLLI) sequence was used to generate eleven T1-weighted images. Myocardial and blood pool T1 values were derived by fitting a signal intensity-time curve using CMR42®. The λ was determined by plotting (1/T1 myo vs. 1/T1 blood pool ) at various time points once contrast equilibrium was reached. Ve was derived accounting for the hematocrit. Short-axis T1 maps were acquired using a 1.5T scanner (Siemens) before and 1,2,5,8,15,20,25 and 30 minutes after contrast. Myocardial tagging images were acquired using single- and multiple-breath-hold CSPAMM sequences in multiple planes and analysed with inTag® (Lyon, France). Results: Twenty-three subjects (age 57 (16), mean (SD); male n=13; severe AS n= 8, healthy control n=15) were recruited. Subjects with severe AS displayed higher λ (0.35 (0.11) vs 0.27 (0.04); P=0.02) and Ve (0.19 (0.08) vs 0.13 (0.03)).The λ and Ve correlated with indices of reduced myocardial function including reduced circumferential δ strain (r=-0.69, p=0.001), angle peak strain (r=-0.48, p=0.04) and radial δ strain (r=-0.59, p=0.03); and increased left atrial dilatation (r=0.64, p=0.001). Conclusions: T1-mapping-derived λ and Ve are significantly elevated in patients with AS compared to healthy controls and correlate well with indices of reduced myocardial performance. This difference was quantifiable after a simple bolus administration of gadolinium. Further histological validation is required; however, T1-mapping λ and Ve derivation after bolus gadolinium administration is clinically practical and holds promise for the detection of IMF in severe AS.