Estimation of Myocardial Extracellular Volume Fraction with Cardiac CT in Patients Undergoing Transcatheter Aortic Valve Implantation - The 64th Annual Conference of the Israel Heart Society & The Israel Society of Cardiothoracic Surgery, 25-26 April 2017

Yoav Hammer ^1,2 Yeela Talmor-Barkan ^1,2 Ariel Gutstein ^1,2 Abid Assali ^1,2 Gideon Shafir ^2,3 Katia Orvin ^1,2 Uri Landes ^1,2 Amos Levi ^1,2 Ziad Arow ^1,2 Hana Vaknin-Assa ^1,2 Ran Kornowski ^1,2 Ashraf Hamdan ^1,2

¹Cardiology department, Rabin Medical Center, Beilinson/Hasharon Hospital
²"Sackler" Faculty of Medicine, Tel Aviv University
³Radiology department, Rabin medical center, Beilinson/Hasharon hospital

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 before transcatheter aortic valve implantation (TAVI).

Background:
The use of CT for estimation of ECV is a new approach toward the evaluation of left ventricular (LV) myocardial fibrosis; however its feasibility was not 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 and 7-minutes post-contrast ECG-gated 256-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 a 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. Good intra-observer CT measurement of ECV was observed [Intra-observer difference and 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 demonstrated the feasibility of CT for the evaluation of LV myocardial fibrosis, which might be part of a comprehensive cardiac CT examination for additional information in the pre-TAVI evaluation of risk in patients with severe AS.