NEW ORLEANS — A fibrinolysis-based intervention in acute intermediate-risk pulmonary embolism (PE) was shown to reduce major events, particularly cardiopulmonary decompensation, with an acceptably low rate of bleeding in a multinational phase 3 trial.
When compared to anticoagulation alone, the current guideline-recommended standard, a catheter-administered 9-mg dose of the tissue plasminogen activator (tPA) alteplase and concomitant ultrasound reduced events by half at no significant cost in adverse events, according to Stavros V. Konstantinides, MD, professor of medicine and clinical trials at the University Medical Center of Johannes Gutenberg University in Mainz, Germany.
The results of this trial, called HI-PEITHO, were presented as a late-breaking session at the 2026 American College of Cardiology (ACC) Meeting. The results were simultaneously published in The New England Journal of Medicine.
Study Leads to 'New Era of Change'
In past studies of fibrinolysis for intermediate-risk PE, bleeding and other risks were not enough to compensate for PE-related benefit. The new strategy, using an ultrasound-facilitated catheter device, is a breakthrough that “leads the way into an era of change,” according to Joshua Beckman, MD, chief of vascular medicine, University of Texas Southwestern Medical School in Dallas.
The clear advantage of fibrinolysis at 7 days confirms clinical utility, but Beckman, who was the ACC-invited discussant on this late breaker, said that if the results continue to be positive with follow-up at 6 and 12 months, they “will be even more important.”
In this trial, 544 PE patients meeting eligibility criteria, including cardiopulmonary distress, an elevated troponin level, and a ratio of right to left ventricular diameter of ≥ 1.0, were randomly assigned to fibrinolysis-based therapy plus anticoagulation or anticoagulation alone. The tPA was delivered by the minimally invasive EKOS endovascular system (Boston Scientific), a device that also delivers clot-dissolving ultrasonic waves.
The primary efficacy outcome was a composite of PE-related death, cardiopulmonary resuscitation (or collapse), or symptomatic PE recurrence.
For those treated with the device, the event rate at 7 days was 4.0% vs 10.3% in the arm receiving anticoagulation alone. The relative risk reduction for the device vs standard therapy exceeded 60% (RR, 0.39; P = .005).
The incidence of major bleeding was numerically higher in the experimental arm across several scales but not statistically significant different. For example, major bleeding rates, as defined by the International Society on Thrombosis and Haemostasis (ISTH), were 4.1% and 2.2% (P = .32), respectively. There was no intracranial hemorrhage seen in either arm.
There were also no substantial between-group differences in other serious adverse events. At 30 days, the mortality rate remained low in both arms if higher in the experimental arm (1.8% vs 1.1%). There was a numerically lower rate of serious adverse events (14.8% vs 16.2%; P = .62) and symptomatic PE recurrence (0.4% vs 0.7%) in the experimental arm at 30 days.
Preserved Cardiorespiratory Function Is Main Benefit
The advantage of the device vs anticoagulation alone was driven entirely by the lower rate of cardiorespiratory decompensation or collapse (3.7% vs 10.3%). There was one PE recurrence in both arms. PE-related deaths occurred in 3 vs 1 patient in the experimental and control arms, respectively, which did not approach significance.
The protection against cardiorespiratory decompensation or collapse was supported by the lower rate of rescue therapy that was provided to patients in the experimental arm (2.9% vs 9.2%).
Fibrinolysis has been pursued as a treatment for intermediate-risk PE in multiple trials, including the 2014 PEITHO trial, which included many of the investigators involved in HI-PEITHO, including Konstantinides. In that trial, the combination of tenecteplase (ranging in dose from 30 to 50 mg) plus heparin was compared to heparin plus placebo.
For the primary outcome of death or hemodynamic decompensation or collapse at 7 days, the tPA therapy was more efficacious (2.6% vs 5.6%; RR, 0.42; P = .02), but more patients had stroke in the tPA arm (2.4% vs 0.2%) and there was more major bleeding (11.5% vs 2.4%).
This trial, using a tPA at a far lower dose and combining it with ultrasound, has provided the first effective therapy for a group of patients that has remained at considerable risk for adverse events on the standard of anticoagulant therapy alone, Beckman reported.
“There really was no understanding before this trial as to how to manage PE patients in the high intermediate-risk zone,” he said, explaining that the gap in knowledge was between higher-risk patients, for which thrombolysis or thrombectomy is indicated, and low-risk patients, where risks of aggressive therapy are not typically warranted.
Although HI-PEITHO did not show a mortality benefit from intervention, Beckman noted that short-term death rates from PE are very low, so such as a benefit would be unlikely. But he thinks that the benefit that was seen on preserving cardiorespiratory function is clinically meaningful.
However, he thinks the field might move even further forward when the long-term results are made available. Given prior studies showing that “nearly 50% of PE patients still are significantly impaired 1 year after PE,” the impact of the study might be even greater.
“The field of pulmonary embolism has moved from out-front reduction in mortality and major events to making patients feel better for the rest of their lives,” he said. “I will be really interested to see the physiologic outcomes as they become available in the next several months.”
Konstantinides reported financial relationships with Bayer, Bristol Myers Squibb, Daiichi Sankyo, Merck Sharp & Dohme, Novartis, Penumbra, Stryker, and Boston Scientific, which provided funding for the HI-PEITHIO trial. Beckman reported no conflicts of interest.
Facts Only
The HI-PEITHO trial was a multinational phase 3 study presented at the 2026 American College of Cardiology Meeting and published in *The New England Journal of Medicine*.
The trial compared a fibrinolysis-based intervention (9-mg alteplase via ultrasound-facilitated catheter) plus anticoagulation to anticoagulation alone in 544 intermediate-risk pulmonary embolism (PE) patients.
Eligibility criteria included cardiopulmonary distress, elevated troponin levels, and a right-to-left ventricular diameter ratio ≥ 1.0.
The primary efficacy outcome was a composite of PE-related death, cardiopulmonary decompensation, or symptomatic PE recurrence at 7 days.
The intervention group had a 4.0% event rate vs. 10.3% in the control group, a relative risk reduction of 61% (RR 0.39, P = .005).
Major bleeding rates (ISTH definition) were 4.1% in the intervention group vs. 2.2% in the control group (P = .32).
No intracranial hemorrhage occurred in either group.
At 30 days, mortality was 1.8% in the intervention group vs. 1.1% in the control group.
The benefit was driven by reduced cardiorespiratory decompensation (3.7% vs. 10.3%).
The EKOS endovascular system (Boston Scientific) was used to deliver alteplase and ultrasonic waves.
The trial was led by Stavros V. Konstantinides, MD, of Johannes Gutenberg University in Mainz, Germany.
Joshua Beckman, MD, of University of Texas Southwestern Medical School, served as the ACC-invited discussant.
Executive Summary
The HI-PEITHO trial, presented at the 2026 American College of Cardiology Meeting and published in *The New England Journal of Medicine*, demonstrated that a fibrinolysis-based intervention using a 9-mg dose of alteplase (tPA) delivered via an ultrasound-facilitated catheter reduced major events in intermediate-risk pulmonary embolism (PE) patients compared to anticoagulation alone. The primary composite outcome—PE-related death, cardiopulmonary decompensation, or symptomatic recurrence—was halved in the intervention group (4.0% vs. 10.3%) at 7 days, with no significant increase in major bleeding. The benefit was driven by reduced cardiorespiratory decompensation, though mortality rates remained low in both groups. Experts highlight this as a breakthrough for intermediate-risk PE patients, who previously lacked effective therapies beyond anticoagulation. Long-term follow-up data, particularly on quality of life, may further clarify the intervention’s value, as prior studies suggest many PE patients experience lasting impairment.
The trial builds on earlier research, such as the 2014 PEITHO trial, which showed efficacy for systemic fibrinolysis but with higher bleeding risks. The HI-PEITHO approach mitigates these risks by using a lower tPA dose combined with ultrasound, delivered via the EKOS endovascular system. While the results are promising, questions remain about long-term outcomes and broader applicability. The study’s findings could reshape clinical guidelines for intermediate-risk PE, offering a new standard of care that balances efficacy and safety.
Full Take
**Steelman:** The HI-PEITHO trial presents a compelling case for a paradigm shift in intermediate-risk PE treatment. By combining low-dose fibrinolysis with ultrasound-facilitated catheter delivery, the study achieves a significant reduction in cardiopulmonary decompensation without the prohibitive bleeding risks seen in prior trials. The use of the EKOS system represents a technological refinement that addresses long-standing concerns about systemic thrombolysis. The trial’s design—randomized, multinational, with clear eligibility criteria—strengthens its credibility. The discussant’s emphasis on long-term follow-up as a potential game-changer is reasonable, given that prior research suggests many PE survivors face chronic impairment. This narrative aligns with a broader trend in medicine toward precision interventions that minimize harm while maximizing functional outcomes.
**Pattern Scan:** The article avoids overt manipulation, but subtle framing choices merit attention. The emphasis on "a new era of change" and "breakthrough" language could be seen as a form of **ARC-0024 Ambiguity**, where the long-term implications are presented as transformative without definitive evidence yet. The comparison to the 2014 PEITHO trial serves as a **ARC-0012 Strawman** of sorts, positioning the new approach as superior by highlighting the older trial’s bleeding risks without equally stressing its mortality benefits. The lack of critical voices beyond the discussant’s cautious optimism might reflect **ARC-0030 Authority Games**, where institutional credibility (ACC, *NEJM*) lends unquestioned weight to the findings. That said, the article does acknowledge uncertainties, such as the need for long-term data, which mitigates overreach.
**Root Cause:** The narrative reflects a tension in modern medicine between aggressive intervention and risk aversion. Intermediate-risk PE has long been a therapeutic gray zone, where the risks of systemic thrombolysis were deemed too high for patients who weren’t critically ill but still faced significant morbidity. The HI-PEITHO trial exploits a technological niche—localized, low-dose fibrinolysis—to thread this needle. The underlying assumption is that preserving cardiorespiratory function, even without a mortality benefit, justifies the intervention. This echoes a broader shift in healthcare toward patient-reported outcomes and quality of life as primary endpoints.
**Implications:** If adopted widely, this approach could improve outcomes for a large subset of PE patients, reducing hospitalizations and long-term disability. However, the cost of the EKOS system and the need for specialized centers may limit accessibility, creating disparities. The focus on functional preservation also raises questions about how we define "success" in PE treatment—is avoiding decompensation enough, or should we aim for complete clot resolution? The trial’s funding by Boston Scientific, the device manufacturer, warrants scrutiny, though the data appear robust.
**Bridge Questions:** How might the cost and availability of the EKOS system influence real-world adoption, particularly in lower-resource settings? Would the benefits hold in patients with comorbidities excluded from the trial? If long-term data show no sustained advantage, does the short-term reduction in decompensation still justify the intervention?
**Counterstrike Scan:** A coordinated influence campaign would likely amplify the "breakthrough" framing, downplay the numerical (non-significant) increase in bleeding, and leverage institutional endorsements (ACC, *NEJM*) to preempt criticism. The actual article includes caveats and acknowledges limitations, which suggests it does not align with a manipulative playbook. The discussion of long-term follow-up as a pending validation point further demonstrates balance.