A new catheter-based procedure that delivers clot-dissolving medication directly to blood clots in the lungs has dramatically improved survival rates for patients with severe pulmonary embolism (PE), reducing the risk of death, circulatory collapse, or clot recurrence by more than 60% compared to standard anticoagulant therapy. This breakthrough, presented at the American College of Cardiology's 2026 Annual Scientific Session, could transform how doctors treat one of the most dangerous cardiovascular emergencies .

Pulmonary embolism occurs when a blood clot suddenly blocks a blood vessel in the lungs, starving the heart and lungs of oxygen and potentially causing death within hours. Between 20% and 25% of PE cases are classified as elevated severity, with mortality rates reaching as high as 15% in real-world settings. Currently, doctors rely on systemic anticoagulants (blood thinners given through the vein) to dissolve clots, but these medications carry a serious risk of dangerous brain bleeding and are typically reserved only for patients already in shock and facing imminent death .

How Does This New Procedure Work?

The catheter-based approach uses specialized ultrasound-enhanced systems to deliver low doses of clot-busting drugs directly into the blood clots blocking the lungs' arteries. A thin tube (catheter) is inserted through a vein in the groin and guided to the site of the clot, where ultrasound energy helps the medication penetrate and dissolve the blockage more effectively than systemic treatment alone. This targeted delivery means doctors can use much smaller doses of the medication, significantly reducing the risk of brain bleeding while improving outcomes .

What Did the Clinical Trial Show?

Researchers conducted a multinational trial involving 544 patients across 59 sites in the United States and eight European countries (Austria, France, Germany, Ireland, Poland, Switzerland, The Netherlands, and the United Kingdom). Half of the participants received the ultrasound-facilitated catheter-directed thrombolysis procedure, while the other half received standard systemic anticoagulation .

At 30 days, the results were striking. Only 4% of patients in the catheter-based treatment group experienced the trial's primary endpoint (PE-related death, circulatory collapse, or recurrent clots within seven days), compared to 10.3% in the standard treatment group. This 61% relative reduction in adverse events was driven primarily by a dramatic decrease in cardiorespiratory decompensation or collapse in the catheter group. Importantly, no brain bleeds occurred in either group, and there were no significant differences in deaths of any cause or major bleeding complications between the two approaches .

• Study Size: 544 patients enrolled across 59 U.S. and European sites, making this the first trial to directly compare catheter-based intervention to standard anticoagulation in elevated-risk PE cases
• Key Safety Finding: No brain bleeds occurred in either treatment group, addressing the primary safety concern that has historically limited the use of clot-busting drugs in PE patients
• Complication Reduction: The catheter procedure reduced the combined rate of PE-related death, circulatory collapse, or clot recurrence by 61% compared to standard treatment alone

"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. 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," 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.

Stavros V. Konstantinides, MD, PhD, Professor of Medicine and Clinical Trials at University Medical Center of the Johannes Gutenberg University in Mainz, Germany

Who Could Benefit From This Procedure?

The trial enrolled patients with intermediate-risk PE who had additional warning signs of severity, including abnormally high heart rate (tachycardia), low blood pressure (though not at shock levels), or low oxygen saturation. These patients represent a critical middle ground: too sick to treat with standard anticoagulation alone, but not yet in the immediate shock state that currently qualifies them for clot-busting drugs. The new procedure offers a safer, more effective option for this high-risk population .

Researchers emphasize that the ultrasound-facilitated catheter-directed thrombolysis approach is feasible for physicians experienced in cardiovascular interventions and in hospitals equipped with a catheterization lab and a team qualified to support the procedure around the clock. This means the procedure is not yet universally available, but centers with the right expertise and infrastructure can offer it now .

What Happens Next?

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 healthcare utilization. The team also noted that results might differ in more ethnically diverse populations, since the trial was predominantly White (85% of participants). Additionally, the study was not powered to detect potential differences in bleeding risk between groups, so longer-term follow-up will be important .

"The results regarding effectiveness are very convincing. 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," Konstantinides noted.

Stavros V. Konstantinides, MD, PhD, Professor of Medicine and Clinical Trials at University Medical Center of the Johannes Gutenberg University in Mainz, Germany

This research was simultaneously published in the New England Journal of Medicine and was funded by Boston Scientific, the manufacturer of the catheter system used in the trial. The findings represent a significant step forward in treating one of cardiology's most urgent emergencies, offering hope to patients with severe pulmonary embolism who previously had limited safe treatment options .

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