Christopher Cao1, René H Petersen2, Tristan D Yan3. 1. The Systematic Review Unit, The Collaborative Research (CORE) Group, Macquarie University, Sydney, Australia. 2. Department of Cardiothoracic Surgery, Rigshospitalet, Copenhagen University Hospital, Copenhagen, Denmark. 3. The Systematic Review Unit, The Collaborative Research (CORE) Group, Macquarie University, Sydney, Australia; Department of Cardiothoracic Surgery, The Royal Prince Alfred Hospital, Sydney, Australia.