Background:Because approximately 10% of patients with no-ST-segment elevation acute coronary syndrome (NSTE-ACS) show no obstructive coronary artery disease (NOCAD) on angiography, we assessed the spectrum of diagnoses and the predictors of outcome of these patients.Methods and Results:We studied 178 patients admitted to a coronary care unit with an initial diagnosis of NSTE-ACS, based on clinical, ECG and laboratory data, but found to have NOCAD. The final diagnosis in these patients was heterogeneous; true NSTE-ACS (ie, coronary thrombosis on an unstable plaque) was ascertained in 1 patient (0.6%), whereas diagnosis at discharge was microvascular NSTE-ACS in 56.2% of patients, variant angina in 10.1%, myocarditis in 8.9%, takotsubo disease in 7.9%, tachyarrhythmia-related chest pain in 6.7%, and non-cardiac pain in 9.6%. At 24.5-month follow-up, 21 deaths (11.8%) had occurred, 9 (5.1%) from cardiovascular causes, including 2 (1.12%) coronary deaths. By multivariable Cox analysis, age only predicted global (hazard ratio [HR] 1.07 [1.02–1.12]; P=0.006) and cardiovascular (HR 1.08 [1.01–1.16]; P=0.04) mortality; non-coronary vascular disease was the main predictor of cardiovascular death or readmission for cardiovascular disease (HR 3.28 [1.75–6.14]; P<0.001) and coronary death or readmission for angina (HR 3.20 [1.26–8.14]; P=0.014).Conclusions:Patients with an initial diagnosis of NSTE-ACS constitute a heterogeneous population with different final diagnoses. Patients have a rather high rate of fatal events, most of which, however, are not related to coronary causes. (Circ J 2016; 80: 1600–1606)