Objectives: To evaluate the feasibility of computed tomography (CT) measurement of extracellular volume (ECV) fraction of the myocardium and to investigate the association between ECV and age, gender, and myocardial mass in patients undergoing CT prior to transcatheter aortic valve implantation (TAVI).
Background: The use of CT for estimation of ECV is a new technique for the evaluation of left ventricular (LV) myocardial fibrosis; however its feasibility has not been studied in patients with severe aortic stenosis (AS).
Methods: Eighteen consecutive patients (79.1 ± 7.2 years, 12 male) with severe AS underwent pre-contrast und 7-minutes post-contrast ECG-gated 256 slice -CT scan for estimation of ECV fraction within the myocardial septum. CT scans were reconstructed using iterative model reconstruction and ECV fraction was calculated as the ratio of the change in Hounsfield unit of the myocardium and the descending aorta blood in the pre- and post-contrast CT scan, multiplied by (1 - hematocrit).
Results: Mean ECV was 42.2 ± 7.6% (range 30.3 - 50.8%), and was not related to age (r = 0.32, P = 0.19) or LV mass (r = 0.33, P = 0.19). Mean ECV was similar in men and women, 42.5 ± 6.9% vs. 41.7 ± 7.6%, retrospectively; P = 0.8. The intra-observer CT measurement of ECV was good [Intra-observer difference with 95% limits was 1.1 ± 17.6 (-16.5, 18.7) and interclass correlation coefficient was 0.78].
Conclusion: CT estimation of ECV fraction, which was not related to age or gender, showed high intra-observer reproducibility. This ongoing study demonstrates the feasibility of CT for the evaluation of LV myocardial fibrosis, which may be part of a comprehensive cardiac CT examination for additional information in the pre-TAVI evaluation of risk in patients with severe AS.
