Background: Aortic Coarctation (CoA) requires a long-term follow-up in order to detect late sequelae such as re-stenosis, aneurysms or arterial hypertension. However, there is a gap of knowledge about adverse tissue remodeling of the LV.

Objectives: The aim of this CMR study was to measure the myocardial extracellular volume fraction (ECV) as a surrogate marker of diffuse myocardial fibrosis in young patients with different grades of CoA.

Methods: As a part of comprehensive CMR examination myocardial extracellular volume fraction (ECV) was calculated from pre-and post- gadolinium contrast T1 measurements of blood and myocardium in 51 patients (age: 19.9 years (range: 14.5-25.6)) with CoA (age at operation: 0.5 years (range: 0.05-4.1)) and 10 age-matched controls. Normalized parameters of left ventricular volumes, mass and ejection fraction were obtained from cine CMR. Patients’ CoA were classified as I (N=17, “low grade” = Vmax≤2,3m/s (delta p <15 mm Hg) and no re-stenosis nor ventricular hypertrophy), II (N=9, “high grade” = Vmax >2,3m/s or re-operation or ventricular hypertrophy), III (N=14, “CoA with bicuspid aortic valve (BAV)”) and no significant re-stenosis, IV (N=8, “CoA with concomitant congenital heart defects, e.g. VSD”). The variation of CMR measures between patient groups was analyzed with the non-parametric Kruskal-Wallis test (H test) and post-hoc pairwise Wilcox testing between groups, with adjustment of p-values by Holm’s method.

Results: Patients with CoA had an increased ECV compared to the control subjects 0.3 ±0.04 (range 0.24 - 0.39) vs. 0.26 ±0.15 (range 0.28 - 0.23), p< 0.05.  LV ejection fraction was 62 ±12.8% vs. 60 ±4.2% (p=ns); indexed left ventricle end-diastolic volume was 86.6 ±22.3 ml/m² vs 78.7 ±11.8 ml/m² (p=ns); indexed left ventricle end-systolic volume was 31.1 ±9.5 ml/m² vs. 31.2 ±5.5 ml/m² (p=ns); LV mass/BSA was 57.71 ±15.56 g/m² vs 51.8 ±11.6 g/m² (p=ns). LV mass/volume was 0.69 ±0.2 g/ml vs 0.67 ±0.2 g/ml (p=ns). ECV in group I (“low grade”) 0.27 ±0.02 was lower than in group II (“high grade”) 0.33 ±0.04, p≤0,011 and III 0.32 ±0.047 p ≤ 0,027. Analogously, this applies to native T1 values in groups I vs. II (p ≤ 0,042) and I vs. III (p ≤ 0,02). Patients with BAV showed a lower ejection fraction compared to group I, p < 0.0001. There was no significant difference in LV mass/BSA between the groups, p > 0,08. Seven Patients developed arterial hypertension which was controlled medically. 7 patients had no surgical repair yet I N=2, II N=4, IV N=1. Five patients had to undergo a reoperation in the past (part of group II). Mean Vmax was in I 1,82m/s, II 2,7m/s, III 1,89m/s, IV 2,5m/s.

Conclusions: Patients with CoA showed higher myocardial extracellular volume (ECV) compared to healthy controls indicative of adverse tissue remodeling. The burden of diffuse fibrosis by ECV depended on the severity of the CoA. Surprisingly, patients with BAV and no re-stenosis showed significantly more diffuse myocardial fibrosis compared to group I and healthy controls. These results suggest that CoA patients may have a higher lifetime risk for outcomes with a putative link to diffuse myocardial fibrosis like diastolic dysfunction and arrhythmias.