Targeted delivery of clot-busters brings greater benefits than standard systemic treatment
NEW ORLEANS (March 28, 2026) — Patients who had low doses of clot-buster drugs delivered directly to the site of a pulmonary embolism (PE) via a catheter using ultrasound to enhance their effect had significantly better outcomes than those who received standard systemic anticoagulants, according to a study presented at the American College of Cardiology’s Annual Scientific Session (ACC.26). The targeted catheter-based approach reduced early PE-related death, circulatory collapse or PE recurrence by more than 60%.
PE, which occurs when a blood clot suddenly blocks a blood vessel in the lungs, causes damage to the heart and the lungs and can lead to death in severe cases. A substantial proportion (at least 20%-25%) of PE cases fall into a category of elevated clinical severity and threatening or beginning cardiopulmonary failure, a condition that may lead to death rates as high as 15% in the real world. Although clot-buster medications given through the vein can effectively dissolve the clots that cause PE, they can also cause dangerous bleeding in the brain and are typically used only in the most severe cases—when a patient is already in shock and at risk of imminent death.
Specialized catheter systems aided by ultrasound energy enable low doses of clot-buster drugs to be delivered directly into the blood clots blocking affected arteries of the lungs through a vein in the groin. The trial is the first to directly compare clinical outcomes from a catheter-based strategy versus systemic anticoagulation alone in patients with elevated-risk forms of PE.
“This trial shows that a catheter intervention can indeed be effective and improve the prognosis for patients with severe PE and elevated risk of early death or life-threatening complications,” said Stavros V. Konstantinides, MD, PhD, professor of medicine and clinical trials at University Medical Center of the Johannes Gutenberg University in Mainz, Germany, and the study’s lead author. “If the right patients are selected for this procedure, it can prevent patients from deteriorating and it can do so at an acceptably low risk of bleeding complications.”
The trial enrolled 544 patients at 59 sites in the United States and eight European countries (Austria, France, Germany, Ireland, Poland, Switzerland, The Netherlands and United Kingdom). Participants had intermediate-risk PE with two additional indicators of clinical severity, including: an abnormally high heart rate (tachycardia), low blood pressure (although not at a level indicating shock) and/or low oxygen saturation. Half of the patients were randomly assigned to ultrasound-facilitated catheter-directed thrombolysis, and the other half received standard systemic anticoagulation. Physicians used standardized protocols for administering the study medications in both treatment arms, and they also followed standard protocols for initiating rescue treatment if patients suffered cardiorespiratory decompensation or a repeat PE.
At 30 days, 4% of those in the catheter-based treatment group and 10.3% of those in the control group experienced the trial’s primary composite endpoint of PE-related death, cardiorespiratory decompensation or collapse, or symptomatic PE recurrence within seven days of randomization. The 61% between-group difference was significant in favor of the catheter-based treatment arm and was driven by a reduction in the rate of cardiorespiratory decompensation or collapse in this group. No brain bleeds occurred, and there were few deaths in either study arm; the results showed no significant difference in deaths of any cause or in major bleeding complications between groups.
Researchers said that the ultrasound-facilitated catheter-directed thrombolysis approach used in the study is feasible to perform for physicians experienced in cardiovascular interventions and in hospitals that are equipped with a catheterization lab and a team qualified to support the procedure around the clock.
“The results regarding effectiveness are very convincing,” Konstantinides said. “In addition, the study offers a precedent for how to evaluate the effects of catheter treatments for PE. There are many types of catheter treatment, and as more trials are conducted, we hope that we will have increasingly strong evidence to inform guidelines on what strategies to recommend.”
Researchers are currently tracking patient outcomes up to 12 months to assess potential differences in long-term survival, late complications, functional outcomes, quality of life and health care utilization. They said the results might differ in ethnologically more diverse populations, and that the study was not powered to exclude potential differences in bleeding risk between groups. They also said the study results should not be extrapolated to apply to all catheter-based PE treatment approaches, which include a wide range of devices and methods.
The ACC/AHA Guideline for the Evaluation and Management of Acute Pulmonary Embolism in Adults establishes a new clinical classification system to assess PE severity and guide treatment strategies.
The trial was an investigator-initiated study funded by Boston Scientific and conducted in partnership with the University Medical Center Mainz, Germany, and the PERT Consortium in the U.S.
This study was simultaneously published online in the New England Journal of Medicine at the time of presentation.
Konstantinides will present the study, “Ultrasound-facilitated Catheter-directed Thrombolysis Vs. Anticoagulation Alone for Acute Intermediate-high-risk Pulmonary Embolism: Primary Results of the HI-PEITHO 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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