ACC 2026 | STEMI-Door To Unload: Unloading with Impella before PCI did not reduce infarct size in anterior STEMI

Anterior ST-segment elevation myocardial infarction (STEMI) remains associated with a high incidence of heart failure and mortality, even in the era of early reperfusion. The “door-to-unload” concept emerged as a physiologically appealing strategy, supported by preclinical data and a pilot study suggesting that left ventricular unloading prior to reperfusion could reduce infarct size.

The objective of the STEMI-DTU study was to evaluate whether a strategy using Impella CP, with a protocolized delay of at least 30 minutes before PCI, could reduce infarct size compared with a standard strategy of coronary angiography and immediate angioplasty in patients with acute anterior STEMI without cardiogenic shock.

This was a randomized study that included patients aged 18 to 85 years, with a first myocardial infarction, presenting between 1 and 6 hours from symptom onset, with anterior STEMI and anatomy suitable for Impella use. Patients were randomized to a strategy of Impella CP + ≥30-minute delay before PCI, with support for 4 to 24 hours, or to immediate PCI. The primary efficacy endpoint was infarct size measured by cardiac MRI between days 3 and 5, expressed as a percentage of left ventricular mass. A total of 527 patients were randomized across 55 centers.

The results showed that, in the intention-to-treat population, there were no differences in the primary endpoint: infarct size was 30.8±16.2% in the treatment group and 31.9±16.9% in the control group (95% CI -4.2 to 2.0; p=0.50). In the per-protocol analysis, no significant differences were observed either: absolute difference of -1.9% (95% CI -5.5 to 1.6; p=0.28). The hierarchical secondary endpoint also showed no benefit, with a win ratio of 1.04 (95% CI 0.84–1.28; p=0.73).

Read also: ACVC 2026 | CELEBRATE Trial: Prehospital Zalunfiban Use in STEMI.

As expected, the unloading strategy prolonged reperfusion times: there was an average increase of 47 minutes in total ischemic time and 42 minutes in door-to-balloon time, with no bailout PCI required. At 12 months, no significant differences were observed in all-cause mortality (4.0% vs 5.1%; HR 0.76; p=0.51).

Regarding safety, in the post hoc analysis of the ITT population, the composite of major bleeding or vascular complications was more frequent in the treatment group (34.0% vs 6.0%), mainly driven by access-site-related events (31.7% vs 2.3%).

Conclusions: STEMI-DTU Study Design: Impella CP with pre-PCI delay vs immediate angioplasty in anterior STEMI

The combination of Impella CP with a 30-minute delay before PCI did not reduce infarct size compared with immediate PCI in patients with anterior STEMI without shock. Major bleeding and vascular complications were more frequent in the Impella group.

Presented by Gregg W. Stone at the Late-Breaking Clinical Trials, ACC.26, March 28–30, New Orleans, USA.