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Recent developments in CMR imaging techniques are enabling rapid parametric mapping of magnetic relaxation properties (T1 and T2 relaxation times). Quantified myocardial T1 values, T2 values could demonstrate the underlying composition of the myocardium. It is still not completely clear how these relaxation times compare in patients with right sided afterload increase such as pulmonary arterial hypertension (PAH) and left sided afterload increase such as severe aortic stenosis (AS). The aims of this study were to observe whether cardiovascular magnetic resonance could characterize native myocardial T1 values, T2 values in patients with pulmonary arterial hypertension (PAH) and severe aortic stenosis (AS) in comparison to healthy volunteers and to evaluate the association of T1 values, T2 values with ventricle function and remodeling.
CMR was performed for in 16 patients with PAH (62±10 years, 9 female), 17 patients with AS (85±5 years, 7 female) and 5 volunteers (38±17 years, 2 female) on a 1.5T MRI scanner. T1 and T2 mapping in addition to ventricular volumes and function of the left and right ventricle (LV and RV) were performed and the values were compared using Student t tests and Pearson's correlation.
Compared with healthy volunteers, patients with PAH had significantly elevated T1 at the septum (1072.4±64.3 ms vs 1023.2±15.3 ms, p=0.017) and RV insertion points (1137.8±81.8 ms vs 1037.6±8.4 ms, p=0.00). They also have higher T2 values at RV insertion points (54.1±5.4 ms vs 42.6±1.5 ms, p=0.001) and RV free wall (46.6±3.3 ms vs 40.5±1.4 ms, p=0.021). Patients with AS had significantly elevated T1 values at the LV free wall (1026.8±53.0 ms vs 966.9±18.8 ms, p=0.006). At the septum, T1 showed a trend of increase in patients with AS (p=0.053) and T2 showed the same trends at RV insertion in patients with AS (p=0.068). No correlation was found between RV insertion point T2 or septal T1 and RV volume, or ejection fraction. A correlation trend was found between RV insertion point T1 and RV mass Index (p=0.06). No correlation was found between LV free wall T1 and LV volume, ejection fraction, or LV mass index.
T1 and T2 values are both elevated in the RV insertion points and the RV free wall of patients with PAH, but only T1 values were elevated in in the free LV wall in patients with severe aortic stenosis. This combination of T1 and T2 values demonstrate potentially different remodeling process in the right compared to the left ventricle with increased afterload.