Background: The prevalence and impact of total coronary occlusion of an infarct-related artery (IRA) on outcomes in patients with non-ST-elevation myocardial infarction (NSTEMI) remain unclear.

Aim: We evaluated the clinical significance of total coronary occlusion in NSTEMI patients.

Methods: A total of 2767 patients with NSTEMI enrolled in the Polish Registry of Acute Coronary Syndromes, who underwent percutaneous coronary interventions, were analysed. The patients were divided into two groups according to preprocedural culprit vessel thrombolysis in myocardial infarction (TIMI) flows (TIMI flow 0 — total coronary occlusion [TO]: 728, 26.3% of the patients, and TIMI flow 1–3 — non-total occlusion [non-TO]: 2039, 73.7% of the patients).

Results: Patients with total occlusion were younger, were more often current smokers, and had lower incidence of hypertension and diabetes mellitus. The left circumflex artery (LCx) was the major IRA in the TO group (48.1%), whereas the left anterior descending artery (LAD) was more commonly the IRA in the non-TO group (38.8%). Multivariate analysis revealed that LCx as the culprit lesion (OR ± 95 CI 1.54 [1.26–1.89], p < 0.0001) was an independent predictor of TIMI flow 0 in IRA. In-hospital and one-month mortality occurred more frequently in the TO group (4.0% vs. 1.7%, p = 0.0005 and 5.5% vs. 3.5%, p = 0.0175, respectively), no differences in the 12-, 24-, or 36-month mortalities were observed between these groups.

Conclusions: Only LCx as a culprit lesion was an independent predictor of total occlusion in IRAs. The NSTEMI patients with TO had higher in-hospital and one-month mortalities, but their long-term outcomes were similar to those of non-TO patients.