Background: Studies on the treatment of patients with an acute ST-segment elevation myocardial infarction (STEMI) with primary percutaneous coronary intervention (PCI) have shown a high rate of aborted MI despite a relatively long delay from the onset of symptoms to reperfusion.

Aim: To assess predictors of aborted MI in patients undergoing primary PCI.

Methods: 310 STEMI patients referred for primary PCI within 12 h of symptom onset were included into a prospective study. Relationships between incidence of aborted MI, clinical, electrocardiographic and angiographic factors were analysed.

Results: Aborted MI was diagnosed in 29 (9.8%) patients. Patients with aborted MI did not differ with respect to age(59.4 ± 10.1 vs. 60.5 ± 11.2 years; p = 0.88), male sex (75.9% vs. 76.0%; p = 0.83), hypertension (51.7% vs. 48.3%;p = 0.87) or total ischaemic time (215.9 ± 104.6 vs. 241.9 ± 134.3 min; p = 0.44) except for the frequency of diabetes mellitus (34.5% vs. 16.1%; p = 0.02) when compared to a group with true MI. TIMI flow ≥ 2 prior to PCI (86.2% vs. 27.7%; p < 0.001), total ST-segment resolution (STSR), both pre-angiography (65.5% vs. 19.5%; p < 0.001) and post-PCI (89.7%vs. 69.2%; p = 0.018) and myocardial blush grade 3 (89.7% vs. 60.0%; p = 0.001) were significantly more frequent in patients with aborted MI. A logistic regression model confirmed TIMI flow ≥ 2 prior to PCI (OR 10.7; CI 3.1–37.8; p = 0.0002), pre-angiography total STSR (OR 3.6; CI 1.2–10.5; p = 0.02) and a history of previous diabetes mellitus (OR 8.6; CI 2.6–27.6; p = 0.0003) as predictors of aborted MI.

Conclusions: 1. Aborted MI was observed in 9.8% of STEMI patients undergoing PCI. 2. TIMI flow ≥ 2 and total STSR priorto PCI were identified as major angiographic and electrocardiographic predictors of aborted MI.