Using a microaxial flow pump prior to and during cardiac stenting procedures for patients with severe heart attacks who don’t have cardiogenic shock does not significantly reduce heart damage. That is the major finding from the first clinical trial of its kind to analyze the effect of resting the heart in high-risk heart attack patients to see if it reduces the size of the heart attack.
Gregg W. Stone, Professor of Medicine (Cardiology) at the Icahn School of Medicine at Mount Sinai, presented these results from “The STEMI-Door to Unload (DTU)” trial on Saturday, March 28, during a late-breaking clinical trial session at the American College of Cardiology Scientific Sessions. This work was simultaneously published in the Journal of the American College of Cardiology.
“In medical school we learned that ‘time is muscle’—and during a heart attack, every minute that the artery is not open matters,” says Dr. Stone, the study’s co-Principal Investigator. “Interventional cardiologists are great at unblocking arteries with stents during this medical emergency, a procedure that saves lives, but we are far less effective at reducing the size of infarct for a variety of reasons. Because of this, many patients have large heart attacks and either don’t survive or develop heart failure.”
A STEMI (ST-segment elevation myocardial infarction) is the most severe, life-threatening heart attack and is caused by a sudden blockage of a major coronary artery, stopping blood flow to a large part of the heart muscle. These patients require urgent percutaneous coronary intervention (PCI), a non-surgical procedure in which interventional cardiologists use a catheter to place stents in the blocked coronary arteries to restore blood flow. It is critical to treat these patients as quickly as possible to prevent or limit heart muscle damage, or infarct, especially since STEMI heart attacks can cause cardiogenic shock—a life-threatening complication in which the heart can’t pump enough blood to the body’s organs.
Many strategies have been developed to try to reduce muscle damage during a cardiac stenting procedure, but almost all of them have failed, Dr. Stone says. Only one therapy—supersaturated oxygen—has been shown to reduce infarct size
For decades, experimental studies on STEMI patients both with and without cardiogenic shock have shown that use of a flow pump that ejects blood from the pumping chamber of the heart to the body can rest the heart, improve blood flow to the heart muscle, and, through other complex mechanisms, reduce heart damage.
“The DTU trial is the first pivotal trial in 30 years that has tested this hypothesis,” Dr. Stone says. “Unfortunately, infarct size, the primary endpoint of the study, was not reduced, and as expected, there were bleeding complications from the device. Thus, while the microaxial flow pump is life-saving in patients with cardiogenic shock, at the present time we do not recommend its routine use in patients with evolving heart attack without shock. However, this approach coupled with pharmacologic or other therapies may be synergistic and improve outcomes in high-risk non-shock patients with heart attacks. That is the future direction for new studies.”
The trial focused on the Impella CP device, a Food and Drug Administration (FDA)-approved catheter-based percutaneous microaxial heart pump manufactured by Abiomed. The researchers investigated the device in patients who had a blocked artery involving the front (anterior) wall of the heart, the location that typically causes large heart attacks, but who were not in shock.
In experimental studies, for infarct size to be reduced, the heart pump has to be inserted 30 minutes before PCI. This delays the stenting procedure, which might paradoxically increase the size of the heart attack.
This new trial is the first to test whether the combination of left ventricle unloading plus delayed PCI reduces the size of heart damage compared with immediate PCI alone in patients with anterior STEMI without cardiogenic shock. Researchers analyzed 527 patients with confirmed anterior STEMI. All arrived within five hours of their heart attack onset at 55 emergency rooms in five countries between December 2019 and September 2024. Patients were randomized to a treatment group with the Impella CP and delayed PCI or to a control group that received immediate PCI without Impella.
The primary effectiveness endpoint was a reduction in infarct size on a cardiac MRI three to five days after the procedure. The primary safety endpoint was to see if the rate of major bleeding—either device- or procedure-related—or major vascular complications was acceptable if there was a reduction of infarct size.
Infarct size expressed as a percent of the total left ventricular mass was slightly less in the Impella group compared to the immediate PCI group (mean 30.8 percent ± 16.2 percent vs. 31.9 percent ± 16.9 percent), but this difference did not reach statistical significance. Notably, however, infarct size among Impella patients did not increase despite the delay. Bleeding and vascular complications were more frequent in the Impella CP group (30.8 percent), a rate that exceeded the performance goal of 26.5 percent. Differences in cardiovascular mortality between the treatment and control groups were not statistically significant.
“While infarct size with the Impella was not significantly decreased, it is important to note that neither was it increased, despite an increase in total ischemic time of approximately 47 minutes. This suggests that the device did have beneficial effects on myocardial recovery. The use of intravenous medications such as nitroglycerine or beta blockers may decease blood pressure while the Impella heart pump is in place, further improving its efficiency,” adds Dr. Stone. “These insights will lead to modifications for future studies in high-risk heart attack patients that could pave the way for improved outcomes.”
Abiomed funded this study.
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Journal of the American College of Cardiology
Randomized controlled/clinical trial
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Left Ventricular Unloading in Anterior STEMI without Shock: The STEMI Door to Unload (DTU) Randomized Trial
28-Mar-2026