Objectives The present study aimed to establish a risk score using a simple calculation with an enhanced predictive value for major adverse cardiac events (MACE) in patients with unprotected left main coronary artery (UPLMCA) disease after the implantation of a drug-eluting stent (DES). Background The anatomic-, clinical-, and procedure-based NERS (New Risk Stratification) score was superior to the SYNTAX (Synergy Between Percutaneous Coronary Intervention With TAXUS and Cardiac Surgery) score in predicting MACE after stenting UPLMCA. The complexity of the calculation was its major limitation. Methods The NERS score II was derived from our previous 2 studies and externally compared with the NERS and SYNTAX scores in 1,463 patients with UPLMCA disease who underwent implantation of a DES in a prospective, multicenter registry trial. The primary endpoint was MACE at 1 year after the index procedure, including myocardial infarction, cardiac death, and target vessel revascularization. Results The NERS score II system consisted of 16 (7 clinical and 9 angiographic) variables. A NERS score II >= 19 demonstrated enhanced MACE sensitivity and specificity of 84.0% and 76.0% (MACE as the state variable), respectively, which were similar to the NERS score but significantly higher compared with the SYNTAX score. A NERS score II > 19 was the only independent predictor of cumulative MACE (hazard ratio: 3.27; 95% confidence interval [CI]: 1.86 to 5.23; p <= 0.001) and stent thrombosis (odds ratio: 22.15; 95% CI: 12.47 to 57.92; p <= 0.001) at follow-up. Conclusions The NERS score II, similar to the conventional NERS score, is more predictive of MACE than the SYNTAX score in UPLMCA patients after implantation of a DES. (C) 2013 by the American College of Cardiology Foundation