Navin Kapur, MD, is the director of the Acute Circulatory Support Program and associate director of the Cardiac Catheterization Laboratory at Tufts Medical Center.

Navin Kapur, MD

LV Unloading Before Delayed PCI Reduces Infarct Size by 1%, With Gregg Stone, MD, and Navin Kapur, MD

Left ventricular unloading and a 30 minute delay prior to percutaneous coronary intervention (PCI) seems to reduce infarct size by 1% in patients with 

ST-segment elevation myocardial infarction (STEMI)

, according to data from the STEMI-Door to Unload (DTU) study.

American College of Cardiology (ACC) Scientific Sessions 2026

 by Gregg Stone, MD, FACC, director of academic affairs for the Mount Sinai Heart Health System and professor of medicine (cardiology) and of population health sciences and policy at the Icahn School of Medicine at Mount Sinai, and Navin Kapur, MD, director of the Acute Circulatory Support Program and associate director of the Cardiac Catheterization Laboratory at Tufts Medical Center.

“What we found was that there was no significant difference in infarct size between the 2 groups, although the infarct size was about 1% smaller as measured as the percent of total left ventricular mass in the group that got unloaded with the Impella device compared to the control group,” Stone told 

 in an exclusive interview. “I would have expected about a 2 to 3% increase in infarct size, because there was a 47-minute delay in the group that got the Impella. So, the device is doing something to reduce infarct size, but it wasn’t quite significant within this trial.”

STEMI-DTU was an open-label, randomized controlled trial conducted across 55 hospitals worldwide. Patients aged 18 to 85 years were eligible for inclusion if they had no prior myocardial infarction and presented with acute anterior STEMI within 1 to 6 hours of symptom onset before hospital arrival. Patients who had been transferred from an outside hospital at which an invasive coronary procedure had been attempted were excluded, in addition to those with cardiogenic shock, unwitnessed cardiac arrest, drug-eluting stents, and other conditions.

The study’s primary endpoint was ischemic stroke normalized to left ventricular mass (IS/LVM) as evaluated by cardiac magnetic resonance (CMR) at 3-5 days following index. The secondary powered effectiveness endpoint was the hierarchical composite of cardiovascular mortality, cardiogenic shock within ≥24 hours of enrollment, left ventricular assist device or heart transplant, heart failure, implantable cardioverter defibrillator, or cardiac resynchronization therapy, and IS/LVM as evaluated by CMR at 3 to 5 days post-procedure.

A total of 527 patients with anterior STEMI without cardiogenic shock were enrolled in the trial and randomly assigned in a 1:1 ratio to either the treatment – trans-valvular micro-axial flow pump (TV-mAFP) plus delayed PCI (n = 262) – or the control group (n = 265). Time to PCI was longer in the treatment group by a median of 40 minutes (96 [78, 122] vs. 56 [40, 72] minutes; 

 <.0001). Total ischemic time was longer in the treatment group as well, by a median of 47 minutes (212 [174, 272] vs. 165 [134, 220] minutes; 

IS/LVM was 30.8 +/- 16.2% in the treatment arm and 31 +/- 16.9% in control, with a mean difference of -1.1% (95% CI, -4.2% to 2%; 

 = .5). Major bleeding and vascular complications at a 30-day follow-up also occurred more frequently in the treatment arm when compared with a prespecified performance goal, as well as with the control group.

These results were ultimately not statistically significant, leading STEMI-DTU to report that TV-mAFP and delayed PCI did not reduce infarct size compared to PCI alone in this population. However, the roughly 1% reduction, Kapur and Stone believe, reflects a significant opportunity for therapy moving forward – and fertile ground for future studies.

“We’re excited because this opens up a new chapter of investigation,” Kapur told 

. “There’s much more work to do, but you can see a number of different study designs coming out – for the first time, we can say that putting in an LV support device, even if you had to delay up to 30 minutes, is not going to increase the infarct size. That’s where the investigative opportunities open up.”

Editors’ Note: Stone reports disclosures with Bioventrix, Abbott, Mount Sinai Hospital, Occlutech, Alleviant, Boehringer Ingelheim, and others. Kapur reports employment with Abiomed/J&J Medtech Heart Recovery.

Kapur N, Mangner N, Aghili N, et al. Primary Left Ventricular Unloading in Anterior ST-Segment Elevation Myocardial Infarction (STEMI) Without Cardiogenic Shock: Results from the STEMI-Door to Unload Randomized Clinical Trial. Abstract presented at the American College of Cardiology Annual Scientific Sessions (ACC.26) in New Orleans, LA, March 28-30, 2026.

Kapur, N, Mangner, N, Aghili, N. et al. Left Ventricular Unloading in Anterior STEMI without Shock: The STEMI Door to Unload (DTU) Randomized Controlled Trial. 

https://doi.org/10.1016/j.jacc.2026.03.071

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Although not statistically significant, the reduction represents a potential new pathway for treating patients with STEMI.

Navin Kapur, MD

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