Outcome measures and definitions
The selected composite end-point included: in-hospital mortality, acute kidney injury (AKI), cerebrovascular accidents and severe low cardiac output (LCO), requiring intraoperative or postoperative intra-aortic balloon pump (IABP). Reopening for bleeding and length of hospital stay were also recorded. We also assessed 1-, 5- and 10-year survival. In-hospital mortality was defined as death by any cause occurred at any time before discharge from index hospitalization, regardless the length of hospital stay. The 30-day mortality was defined as death within 30 days from surgery even if occurring after discharge. Cerebrovascular was defined as any new postoperative stroke confirmed by computed tomography scan. AKI was defined according to the Risk, Injury, Failure, Loss, and End stage (RIFLE) criteria [14]. The highest postoperative creatinine value recorded was used to compare with baseline value, bearing in mind that RIFLE criteria require SCrea to increase by at least 50% from baseline value to be classified as AKI [14]. Severe LCO was defined as any intraoperative or postoperative LCO requiring the use of IABP. Late survival data were obtained from the UK National Health Service (NHS) tracing service to identify non-survivors and date of late any-cause death, with the latest data obtained in February 2015.