Computed tomography-derived myocardial extracellular volume fraction - a redundant by-product or a novel promising marker?

Myocardial extracellular volume (ECV) expansion is associated with myocardial abnormalities such as interstitial fibrosis, inflammation or amyloid deposition. Our aim was to search for correlates of ECV fraction (ECVF) derived from routine cardiac computed tomography (CT) of real-world patients. We retrospectively derived ECVF from archived chest CT scans performed in 103 patients (51 women and 52 men; mean age: 66 ± 13 years) during a diagnostic work-up based on clinical indications. From recorded echocardiographic images, we calculated indices of left ventricular (LV) structure and function, including systolic (S') and diastolic (E' and A') mitral annular velocities. There were no significant relations between ECVF and clinical or echocardiographic parameters. LV function was comparable according to median ECVF (24.7%) (S': 10.4 ± 4.1 vs. 9.5 ± 8.0 cm/s; E': 9.2 ± 3.4 vs. 9.4 ± 3.1 cm/s; E'/A' ratio: 1.0 ± 0.6 vs. 1.2 ± 0.9; E/E' ratio: 9.0 ± 4.8 vs. 9.4 ± 5.8 for ECVF above and below the median, respectively). S' and E' were positively correlated in 52 subjects with an over-median ECVF (r = 0.46, p = 0.001), in contrast to their 51 counterparts with a below-median ECVF (r = 0.15, p = 0.3). In conclusion, ECV expansion might be associated with a marked interdependence of S' and E', corresponding to systolic and early diastolic LV performance, respectively. As E' is a rough surrogate index of LV active relaxation, these findings could reflect a contribution of LV fibrosis to early LV diastolic dysfunction, known to coincide with discrete LV long-axis systolic dysfunction. Further studies are warranted to investigate relations between CT-derived ECVF and LV mechanics.