Two separate randomized trials of Johnson & Johnson’s miniaturized Impella heart pumps failed to illustrate the devices’ benefits, spanning specific cases in patients with blockages in their coronary arteries—including interventions both ahead of and after they’ve suffered a severe heart attack.
Presented as late-breaking studies at the annual meeting of the American College of Cardiology, held this weekend in New Orleans, the news comes as J&J reports expanded usage of Impella across a variety of procedures, with annual sales growing more than 17% in the 2025 calendar year.
The company acquired the catheter-based pumps through its $16.6 billion purchase of Abiomed in late 2022, based on a relatively simple premise—by being threaded into the heart’s chambers, they could help push blood out to the body and take some of the workload off of a damaged cardiac muscle, giving it time to rest and heal.
Abiomed’s early Impella systems claimed FDA green lights for temporarily supporting patients undergoing high-risk procedures, such as percutaneous coronary interventions to place stents or balloons, known as PCI. The platforms, with different sizes and uses in the right and left ventricles, have also been approved for people with acute heart failure and cardiogenic shock.
At the ACC meeting, researchers said their randomized trial was the first to explore the addition of Impella pumps to standard PCI and elective coronary angioplasty in patients with severe coronary heart disease and moderate to severe heart failure. They found the approach brought no benefit and could potentially harm patients in the long run.
About two years after undergoing the procedure, patients who received the heart pump had a higher risk of dying due to a cardiovascular event, according to the study, which was simultaneously published in the New England Journal of Medicine.
The CHIP-BCIS3 trial, which enrolled 300 participants in the U.K., included patients who had previously had a heart attack or were admitted to a hospital with severe chest pain and had severe coronary blockages, as well as significantly reduced ejection fraction, in which the heart struggles to pump blood with each beat.
By evenly pairing patients between the Impella CP and control arms, researchers found that not using the pump led to better outcomes 43% of the time, compared with 36% with the pump, failing to demonstrate a statistically significant difference. In addition, about 20% of the pairings showed no difference.
“We found no evidence that use of the temporary pump protected the heart during the angioplasty procedure,” said the study’s first author, Divaka Perera, M.D., a professor of cardiology at King’s College London. “Our findings strongly suggest that we shouldn’t be using this device routinely without more evidence of benefit.”
At the same time, patients who received left ventricular assistance saw their risk of death from any cause increase by about 50%, with rates of 32.6% versus 23.4% in the control arm.
“This was surprising because the whole premise of LV unloading was that it protects the heart,” Perera said in a statement. “But we found that patients assigned to LV unloading had more damage to the left ventricle than those assigned to standard care.”
Researchers have hypothesized that the force of the pump could injure blood vessels, causing them to bleed or tear, but Perera said rates of vascular injuries were low in both study groups. There were also no differences recorded among secondary endpoints such as rates of heart attacks, disabling strokes or hospitalizations for heart failure.
In an accompanying NEJM editorial, Brahmajee Nallamothu, M.D. and Brett Wanamaker, M.D., interventional cardiologists at the University of Michigan’s Frankel Cardiovascular Center, wrote that the use of Impella pumps for high-risk PCI “has grown considerably despite a lack of randomized evidence showing benefit,” especially in the U.S., and noted that an earlier trial supporting the system’s FDA approval “was stopped early for futility after showing no difference in 30-day clinical outcomes” compared to intra-aortic balloon pumps.
“This approval and the commercial framing of these devices under the ‘Protected PCI’ designation has reinforced a perception of procedural safety for the operator,” they wrote. “We think that hemodynamic support with the microaxial flow pump is useful in patients who are in a decompensated state. However, an understanding of when and in whom pump use is beneficial remains limited.”
Nallamothu and Wanamaker also pointed to an upcoming trial, the J&J-sponsored PROTECT IV, which is slated to enroll 1,200 patients and run through late 2027.
“Until those data are available, this trial reminds us that the price of protection is not borne by those who prescribe it but by the patients who receive it. Whether the protection being offered is theirs, or ours, remains the central question yet to be answered,” they wrote.
The second late-breaking ACC study explored the timing of Impella’s use in patients immediately following a large, life-threatening heart attack known as a STEMI.
Researchers examined whether running the patient’s heart on the pump for about 30 minutes before reopening the impacted coronary artery would limit the total damage caused by the infarction to the cardiac muscle.
“Our findings do not support the routine use of a left-ventricular 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 Stone, M.D., co-author of the STEMI-DTU study and professor of cardiology at Mount Sinai’s Icahn School of Medicine.
“In general, the sooner we can get the blocked artery open, the less heart damage the patient will experience,” Stone said in a statement. “However, despite rapid angioplasty, heart attacks are often large in patients with a STEMI, leading to death and heart failure.”
The J&J-sponsored trial, which was simultaneously published online in JACC, enrolled 527 international patients, with 98% suffering from a complete blockage of their largest coronary artery.
Previous preclinical work and a human pilot study showed that about 30 minutes of Impella time before PCI could reduce myocardium damage, and potentially help avoid additional injury by reducing the strain while preconditioning the heart ahead of reopening the flow of oxygenated blood, as greater infarct sizes are linked with subsequent risks of dying or developing heart failure.
But time is still muscle. In the study’s control group, symptom onset to coronary intervention lasted about 165 minutes, including about an hour spent after arriving at the hospital. The experimental arm added a median of 47 minutes of blocked artery time, while the pump stayed in for more than 10 hours after PCI to reduce ventricular workload. In addition, the Impella group saw higher rates of bleeding complications.
According to J&J, while the study showed the approach did not decrease infarct sizes—with heart muscle damage measured by MRI as 30.8% in the Impella group, compared 31.9% in the control—it didn’t increase them either, and the findings may spur further research.
“STEMI-DTU is the first clinical trial to test this novel and disruptive hypothesis and demonstrate the ability to stop the ischemic clock during infarct,” said co-principal investigator William O’Neill, M.D., emeritus director of the Center for Structural Heart Disease at Henry Ford Health System. “More research is needed in older age, abnormal lactate subsets and the impact of concomitant beta blockade. We will continue to explore LV unloading impact without PCI in STEMI patients in future studies.”
J&J said elevated lactate levels were linked to larger infarct sizes across the total study population, and that pre-PCI testing could identify patients at higher risk despite appearing to be clinically stable. In addition, researchers said that pre-treatment with blood pressure-lowering medications could potentially improve the effectiveness of the pumps, as most study participants presented with high blood pressure.
The STEMI-DTU trial also follows J&J’s DanGer Shock clinical program, which showed Impella pumps could improve survival after a STEMI heart attack and cardiogenic shock, and that those benefits could last for as long as a decade.
