From the Departments of Pediatrics, Cardiothoracic Surgery, and the Abboud Cardiovascular Research Center, Carver College of Medicine, University of Iowa, Iowa City, Iowa. Disclosures: Authors have nothing to disclose with regard to commercial support. Received for publication Feb 1, 2016; accepted for publication Feb 2, 2016. Address for reprints: Peter J. Gruber, MD, PhD, Cardiothoracic Surgery, University of Iowa, Carver College of Medicine, 200 Hawkins Dr, SE540GH, Iowa City, IA 52242 (E-mail: peter-gruber@uiowa.edu). J Thorac Cardiovasc Surg 2016;151:1527-8 0022-5223/$36.00 Copyright 2016 by The American Association for Thoracic Surgery http://dx.doi.org/10.1016/j.jtcvs.2016.02.002 The amino-terminal peptide domain of procollagen is cleaved and released into plasma.