Radiological signs of chronic thrombi are present in 20% of patients with acute pulmonary embolism (PE). Catheter-Directed Thrombolysis (CDT) can swiftly reverse right ventricular dysfunction in patients with acute PE. We investigated the frequency of radiological signs of chronic PE and chronic thromboembolic pulmonary hypertension (CTEPH) in patients treated with CDT and their impact on hemodynamic and clinical outcomes.

Index CT scans of patients receiving CDT for acute intermediate-high and high-risk PE at an academic institution (2017-2022) were adjudicated by 3 radiologists blinded for outcomes. Changes in mean pulmonary artery pressure (mPAP) at 24 hours post CDT, presence of post-PE impairment (PPEI) and CTEPH after 3 months were studied. A total of 15 radiological signs of chronicity were assessed, including 6 criteria validated to raise the suspicion of pre-existing CTEPH. Acute-on-chronic PE (AoC-PE) was defined when at least 3 of those 6 validated criteria were present. Pre-existing CTEPH was defined based on the results of follow-up (vs. index) CT scan and on the anatomical consistency of pathology specimens after pulmonary endarterectomy. PPEI was defined by the presence of respiratory symptoms and right ventricular dysfunction during follow-up

Of 180 consecutive patients (median age 65 years, 61% men, 17% high-risk PE), 31 had at least 3 of 6 radiological criteria at the time of acute presentation (Table 1). Baseline mPAP was 35 mmHg in both groups and no difference in absolute and relative mPAP reduction was observed among the groups after CDT (11 [Q1-Q3: 5-17] mmHg in AoC-PE vs 10 [Q1-Q3: 5, 17] mmHg in acute PE) (Table 2). Three (1.7%) patients were diagnosed with CTEPH after a median of 3 months: in all 3, CTEPH was pre-existing and all of them were in the AoC PE group. Their median baseline mPAP was much higher (53 mmHg) than in the remaining patient group and the relative reduction after CDT was lower. During follow-up, PPEI was more frequent in the AoC PE group (12.9% vs. 2.7%).

The evaluation of six radiological parameters in index CT successfully identified all cases of pre-existing CTEPH in patients presenting with acute PE. However, these parameters did not prove effective in determining which patients would benefit from CDT in terms of mPAP reduction.