The HI-PEITHO trial represents an important milestone in the evolving treatment landscape of acute pulmonary embolism (PE). Until now, catheter-directed therapies have been supported predominantly by single-arm studies demonstrating rapid improvements in right ventricular (RV) function and pulmonary haemodynamics, while evidence for clinically meaningful outcomes remained limited. HI-PEITHO is the first large randomized trial to demonstrate a clinical benefit of catheter-directed reperfusion compared with anticoagulation alone in selected patients with intermediate-risk PE. The multinational trial randomized 544 patients with acute PE, RV dysfunction (RV/LV ratio ≥1.0), elevated cardiac troponin, and at least two additional indicators of cardiorespiratory distress to ultrasound-facilitated catheter-directed fibrinolysis (USCDT) plus anticoagulation or anticoagulation alone. Importantly, the population therefore represents a selected subgroup at the higher end of the intermediate-risk spectrum rather than the entire heterogeneous population currently classified as intermediate-high risk. The primary composite endpoint of PE-related death, cardiorespiratory decompensation or collapse, or symptomatic recurrent PE within seven days occurred in 4.0% of patients receiving USCDT compared with 10.3% receiving anticoagulation alone (relative risk 0.39; 95% CI 0.20–0.77; P=0.005). The benefit was predominantly driven by prevention of cardiorespiratory decompensation or collapse. Major bleeding at seven days occurred in 4.1% versus 2.2%, respectively, without a statistically significant difference, and importantly, no intracranial haemorrhage occurred.
These findings have several implications. First, HI-PEITHO challenges the traditional concept that anticoagulation followed by rescue reperfusion is necessarily the optimal strategy for all haemodynamically stable patients with PE. Early identification of patients approaching haemodynamic deterioration may allow preventive reperfusion before overt shock develops. At the same time, the results require careful interpretation. Mortality was low and HI-PEITHO was neither designed nor powered to demonstrate a mortality benefit. Moreover, the primary endpoint was driven largely by cardiorespiratory deterioration, including patients fulfilling the prespecified NEWS criterion. Thus, the trial should not be interpreted as justification for routine catheter intervention in intermediate-risk PE.
Rather, HI-PEITHO reinforces the importance of patient selection. Clinical parameters such as borderline blood pressure, tachycardia and tachypnoea, when combined with RV dysfunction and myocardial injury, can identify a subgroup whose risk extends beyond conventional intermediate-high-risk classification. The challenge now shifts from demonstrating that catheter-directed treatment can improve outcomes to determining which patients benefit most.
