Mechanical Circulatory Support Doesn’t Reduce Infarct Size in STEMI without shock

In the STEMI Door-to-Unload trial, use of Impella CP failed to reduce infarct size in patients with anterior STEMI without cardiogenic shock, and it increased the risk of major bleeding and vascular complications compared with PCI alone. The findings were presented at ACC.26 and published simultaneously in JACC.

Trial results

The randomized study included 527 patients with anterior STEMI and no shock, comparing 30 minutes of LV unloading before PCI with PCI alone. The primary endpoint—infarct size normalized to LV mass on cardiac MRI—was not significantly different between groups. There was also no meaningful improvement in secondary clinical outcomes.

Safety signal

The main downside was safety: major bleeding and major vascular complications were higher with Impella than with PCI alone. Device-related access-site bleeding accounted for much of the excess risk. Investigators said the results did not meet an acceptable performance threshold for safety.

Clinical takeaway

Experts emphasized that these findings apply to patients without shock, not to patients with cardiogenic shock, where Impella remains a different clinical tool. In this STEMI population, the risk-benefit balance does not support routine use of Impella to reduce infarct size. The study adds to a long list of therapies that looked promising mechanistically but did not translate into clinical benefit.