No significant between-groups difference in the extent of heart-muscle damage

NEW ORLEANS (March 28, 2026) — The first randomized trial to test whether adding a small, temporary pump to allow the heart to rest and intentionally delaying percutaneous coronary intervention (PCI), also known as coronary angioplasty, for 30 minutes to reduce heart damage compared with standard immediate PCI in patients with heart attacks at risk for a large amount of heart damage found no significant difference between the two groups, the study’s primary endpoint. The research was presented at the American College of Cardiology’s Annual Scientific Session (ACC.26).

“Our findings do not support the routine use of a left-ventricular (LV) transaxial flow pump followed by a 30-minute waiting period before performing PCI, as opposed to performing immediate PCI without the heart pump,” said Gregg W. Stone, MD, professor of cardiology and professor of population health sciences at Icahn School of Medicine at Mount Sinai in New York and co-author of the trial.

A STEMI is a severe, life-threatening heart attack caused by a complete blockage of a major coronary artery. When patients are experiencing a STEMI, any delay in restoring blood flow to the heart increases damage to the heart muscle and the patient’s risk of dying of heart failure, Stone said.

“In general, the sooner we can get the blocked artery open, the less heart damage the patient will experience,” he said. “However, despite rapid angioplasty, heart attacks are often large in patients with a STEMI leading to death and heart failure.”

PCI is a minimally invasive procedure that involves placing a tiny balloon inside a blocked coronary artery and inserting a small, wire-mesh tube called a stent to keep the artery from becoming blocked again. Guidelines recommend performing PCI within 90 minutes of a patient’s arrival in the emergency room (ER). In practice, however, there is on average a two- to three-hour delay between the onset of symptoms and the patient arriving at the ER, Stone said. Often, patients don’t immediately recognize that they are having a heart attack and by the time they arrive at the ER considerable heart-muscle damage has already occurred.

“We clearly need new strategies to continue to improve outcomes in patients with STEMI,” he said.

Left-ventricular unloading is a technique that involves using a catheter to insert a tiny mechanical pump into the left ventricle, the heart’s main pumping chamber. This temporarily reduces the ventricle’s workload by allowing the mechanical pump to directly send blood and oxygen to the aorta and from there to the body’s organs. Findings from both lab studies and a pilot study in humans have suggested that, in patients with a STEMI, LV unloading followed 30 minutes later by PCI could reduce heart-muscle damage. The large, randomized STEMI-DTU trial was designed to determine whether this approach would indeed lessen heart-muscle damage and improve outcomes for patients experiencing a STEMI.

The trial enrolled 527 patients (average age 61 years, 79% men) at 55 hospitals in six countries (the United States, Canada, the United Kingdom, Germany, Italy and Switzerland). Almost all of the patients (98%) had complete blockage of the left anterior descending artery, the largest coronary artery, which supplies blood to the left side of the heart. Patients were assigned at random to receive either a LV transaxial flow pump plus a 30-minute waiting period before PCI (the intervention group) or conventional immediate PCI without a LV support pump (the control group).

The trial’s primary endpoint was the extent of patients’ heart-muscle damage, evaluated by magnetic resonance imaging of the heart three to five days after their procedure. The key secondary efficacy endpoint was a composite of death within one year, cardiogenic shock, heart failure, need for a heart transplant or other treatment to support the heart, and the extent of heart muscle damage. The key secondary safety endpoint was major bleeding or blood vessel complications within 30 days.

Results showed that the extent of heart-muscle damage was not significantly different in the two groups of patients (30.8% in the intervention group versus 31.9% in the control group). The 30-day rate of device-related major bleeding or blood vessel complications was 30.8% in the intervention group, which exceeded the 26.5% pre-defined performance goal. The rate of any major bleeding or vascular complications was 34% in the intervention group and 6% in the control group. At one year, 3.6% of patients in the intervention group had died compared with 5.1% in the control group, a non-statistically significant difference. The study will continue to follow patients for up to five years.

Although the study did not meet its primary endpoint, the findings suggest several avenues for further research, Stone said.

“Of note, in the group that received the heart pump, there was a 47-minute delay before PCI was performed,” he said. “We would have expected this to increase the extent of heart damage. But we did not see that—if anything, there was slightly less heart damage in the treatment group, although this did not reach statistical significance. We noted the same effect in an earlier pilot study. This is interesting because we know that ‘time is muscle,’ and any delay in performing PCI is likely to increase heart-muscle damage. So, it would appear that supporting the heart with the temporary pump before PCI in patients with STEMI is doing something to offset this effect.”

Additionally, the findings apply only to patients with STEMIs who are not experiencing cardiogenic shock, a life-threatening medical emergency characterized by low blood pressure, low blood oxygen and inability of the heart to meet the body’s need for blood. In a previous randomized trial, use of the same temporary heart pump as in the current study significantly reduced the risk of death from any cause within 180 days in patients with both a STEMI and cardiogenic shock, compared with similar patients who were not treated with the heart pump.

In contrast to cardiogenic shock, Stone said that most patients enrolled in the study had elevated blood pressure, and the type of temporary heart pump used works most efficiently in patients with normal or low blood pressure, pointing to open areas of inquiry.

“Pre-treating patients with intravenous medications to lower blood pressure before or shortly after inserting the temporary heart pump could improve the pump’s effectiveness and lead to a greater reduction in heart damage,” he said. “In addition, removing the pump sooner would likely reduce bleeding complications. These changes represent potential avenues for future studies.”

The study was funded by J&J MedTech Heart Recovery, the parent company of Abiomed, Inc., which manufactures the temporary heart pump used in the study.

This study was simultaneously published online in JACC at the time of presentation.

Stone will present the study, “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” on Saturday, March 28, at 9:30 a.m. CT / 14:30 UTC in the Main Tent, Great Hall.   

ACC.26 will take place March 28-30, 2026, in New Orleans, bringing together cardiologists and cardiovascular specialists from around the world to share the newest discoveries in treatment and prevention. Follow @ACCinTouch, @ACCMediaCenter and #ACC26 for the latest news from the meeting.

The American College of Cardiology (ACC) is the global leader in transforming cardiovascular care and improving heart health for all. As the preeminent source of professional medical education for the entire cardiovascular care team since 1949, ACC credentials cardiovascular professionals in over 140 countries who meet stringent qualifications and leads in the formation of health policy, standards and guidelines. Through its world-renowned family of JACC Journals, NCDR registries, ACC Accreditation Services, global network of Member Sections, CardioSmart.org patient resources and more, the College is committed to ensuring a world where science, knowledge and innovation optimize patient care and outcomes. Learn more at ACC.org.

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