Response to Letters Regarding Article, "Frequency and Predictors of Internal Mammary Artery Graft Failure and Subsequent Clinical Outcomes: Insights From the Project of Ex-Vivo Vein Graft Engineering via Transfection (PREVENT) IV Trial". Issue 21 (24th May 2016) - Harskamp, Ralf E.; Alexander, John H.; Ferguson, T. Bruce; Hager, Rebecca; Mack, Michael J.; Englum, Brian; Wojdyla, Daniel; Schulte, Phillip J.; Kouchoukos, Nicholas T.; de Winter, Robbert J.; Gibson, C. Michael; Peterson, Eric D.; et al.