Cardiac performance is limited by oxygen delivery to the mitochondria in 1 the crystalloid-perfused working heart 2 Running Head : Ex vivo working heart oxygenation

*These authors contributed equally as first author to this article 7 These authors contributed equally as last author to this article 8 9 Department of Biomedical Engineering, The George Washington University, Washington, 10 District of Columbia 11 Laboratory of Cardiac Energetics, National Heart, Lung, and Blood Institute, National Institutes 12 of Health, Bethesda, Maryland 13 14 15 Author Contributions: 16 Conception and design of research: RSB, MWK 17 Performed experiments: SKG, RC, BG, AMW, KG, SAF 18 Analyzed data: SKG, BG, ANF, RJ, RSB 19 Interpreted results of experiments: SKG, BG, RSB, MWK 20 Prepared figures: SKG 21 Drafted manuscript: SKG 22 Edited and revised manuscript: SKG, BG, RJ, RSB, MWK 23 Approved final version of manuscript: SKG, RC, ANF, BG, RJ, AMW, KG, SAF, RSB, MWK 24 25 Corresponding Author: 26 Sarah Kuzmiak-Glancy 27 Department of Kinesiology 28 School of Public Health 29 University of Maryland 30 4200 Valley Dr 31 Suite 2351 32 College Park, MD 20742 33 Phone: 301.405.2450 34 Email: sglancy@umd.edu 35 36 Articles in PresS. Am J Physiol Heart Circ Physiol (November 10, 2017). doi:10.1152/ajpheart.00321.2017