Myocardial T1 and T2 mapping in severe aortic stenosis: Potential novel insights into the pathophysiology of myocardial remodelling

Purpose: Severe aortic stenosis (AS) is known to be associated with substantial myocardial remodelling, leading to diffuse myocardial fibrosis (DMF). Native myocardial T1 is emerging as a novel imaging biomarker for the non-invasive assessment of DMF. In contrast, no studies exist elucidating changes of myocardial T2 reflecting myocardial oedema in the presence of AS. The purpose of the present study was to combine native T1 and T2 mapping in order to characterize myocardial tissue changes in the setting of severe AS. Methods: After obtaining ethical approval and informed consent, a total of 26 prospectively selected patients with severe AS (13 women, mean age 81 +/- 7 years) and 17 healthy controls (12 women, mean age 63 +/- 6 years) underwent cardiac magnetic resonance (CMR) imaging on a clinical 3 T scanner. The CMR protocol included a native Modified Look-Locker (MOLLI) T1 mapping and a Gradient Spin Echo (GraSE) T2-mapping sequence in three short-axis slices and one long-axis view. After segmentation, myocardial T1 and T2 values were averaged over the entire myocardium. Statistical analysis was performed using Wilcoxon sum-rank test, Welch's independent t-test and Pearson's correlation coefficient. Results: Global native myocardial T1 was significantly increased in AS patients when compared to controls (1305 +/- 39 vs. 1272 +/- 21 ms, p = .005). Similarly, mean myocardial T2 was significantly elevated in AS patients (51 +/- 4 vs. 46 +/- 2 ms, p < .001) and showed a strong correlation with native T1 (r = .60, p < .001). An overlap was observed between T1 of both groups, whereas T2 discriminated nearly perfectly between the two groups (area under the curve in ROC analyses: 0.76 for T1, 0.87 for T2). Conclusions: Patients with severe AS exhibit significantly elevated native myocardial T1, which has previously been shown to correlate with the amount of myocardial collagen. Adding to this evidence, the present study is the first to show that native T1 and T2 are both significantly elevated and correlated in AS patients, pointing towards a potential role of oedematous/inflammatory processes in the pathophysiology of myocardial remodelling associated with AS.