Threading a catheter into a lung clot and dripping a clot-dissolving drug directly onto it beat blood thinners alone in a trial of 558 patients, without causing more bleeding. The PRAGUE-26 results were published on August 31, 2026 in the New England Journal of Medicine. Patients had intermediate-high risk pulmonary embolism, a clot in the lungs that has not yet dropped the blood pressure but is already straining the right side of the heart.
Key takeaways
- Death, a repeat clot, or cardiorespiratory collapse within 7 days happened in 0.7% of the catheter group versus 6.8% of those on blood thinners alone.
- Bleeding rates were close to identical in the two groups, which is the part that separates this trial from earlier ones.
- The trial was open-label, ran only in Czechia, and reported outcomes at 7 days.
What the study found
The trial, led by Professor Viktor Kočka and Doctor Josef Kroupa of Charles University in Prague, randomly assigned 558 patients at 11 Czech hospitals to catheter-directed thrombolysis with the clot-busting drug alteplase on top of standard blood thinners, or to standard blood thinners alone. Median age was 64 and 40.9% were women.
The main outcome, a combination of death from any cause, another pulmonary embolism, or cardiorespiratory decompensation or collapse within 7 days, happened in 2 of 280 catheter patients (0.7%) and 19 of 278 standard-care patients (6.8%). In absolute terms that is roughly 6 fewer events per 100 patients treated, or about 1 event prevented for every 16 patients given the catheter. The relative figure is about a 90% lower risk (relative risk 0.10), very likely between 56% and 98% lower (95% confidence interval 0.02 to 0.44), with less than a 1 in 1,000 chance a gap that large is coincidence.
The researchers state the difference was driven mainly by fewer cases of cardiorespiratory decompensation or collapse, not by fewer deaths.
On safety, clinically relevant bleeding within 7 days hit 13 catheter patients (4.6%) and 14 standard-care patients (5.0%). Major bleeding was 1.4% versus 2.2%. Bleeding into the brain occurred in 2 catheter patients and none on blood thinners alone. One catheter patient died within 30 days; four standard-care patients died within 7 days.
Dr. Kumar’s take
The 90% lower risk is only half of this result. The other half is the flat bleeding rate.
Clot-busting drugs have always worked in this setting. The problem was what they cost. Given through a vein at full dose, they flood the whole circulation, and the bleeding risk that comes with that has kept them out of routine use in patients whose blood pressure is still holding. Trading a collapse you might survive for a brain bleed you might not is a bad trade, which is why most of these patients have been left on anticoagulation alone ever since.
PRAGUE-26 changes the arithmetic by changing the delivery. A much smaller dose of lytic drug, given through a catheter sitting in the pulmonary artery, dissolves the clot locally without flooding the whole circulation. The safety numbers here look like blood thinners alone.
Three caveats deserve equal billing. The trial was open-label, so everyone knew who got the catheter, and the outcome that carried the result was “decompensation or collapse”, a call a clinician makes at the bedside. That is the kind of endpoint that softens when nobody is blinded. Second, the trial ran entirely in one country, so how these results travel to other health systems is untested. Third, 7 days is a short window, with no long-term data yet on breathlessness, exercise capacity, or chronic pulmonary hypertension, which is where the argument for opening these clots has always been.
The two brain bleeds in the catheter group, against none in the other, also stay in view even though overall bleeding rates matched.
What it means for you
If you or a family member is admitted with a pulmonary embolism, it is reasonable to ask which risk category it falls into. This trial applies only to the intermediate-high group with heart strain, not to smaller clots that do fine on blood thinners. Asking whether the hospital has a pulmonary embolism response team is fair too, since the procedure needs a catheterisation lab and people who do it often.
Nothing here changes prevention, still the higher-leverage side. Clots follow immobility, surgery, cancer, pregnancy, and estrogen-containing medication, and the ordinary work of protecting the cardiovascular system, including how beans and soy foods lower your risk of high blood pressure, matters more day to day than any procedure.
New ESC guidelines on pulmonary embolism are due next year, and the investigators say they hope these results inform them. Until then, this is one strong trial, not a settled standard.