Radiological indicators of chronicity in patients with acute symptomatic pulmonary embolism treated with ultrasound-assisted catheter-directed thrombolysis: a study of 180 consecutive cases

Abstract Background Radiological signs of chronic thrombi are present in up to 20% of patients that present acutely with pulmonary embolism (PE). Ultrasound-Assisted Catheter-Directed Thrombolysis (USAT) can swiftly reverse right ventricular dysfunction in patients with acute PE. Purpose To investigate the frequency of radiological signs of chronic PE and pre-existing chronic thromboembolic pulmonary hypertension in patients treated with USAT and their impact on early and long-term hemodynamic and clinical outcomes. Methods The index CT scans of patients receiving USAT for acute intermediate-high and high-risk PE at a tertiary academic institution (2017-2022) were adjudicated by three expert radiologists blinded for treatment scheme and outcomes. Changes in invasively-measured mean pulmonary artery pressure (mPAP) at 24 hours post USAT, presence of post-PE impairment (PPEI), and CTEPH diagnoses after at least 3 months were studied. A total of 15 radiological signs of chronicity were assessed, including 6 major criteria that have been previously validated to raise the suspicion of pre-existing CTEPH. In this study, acute-on-chronic PE was defined when at least 3 of the 6 validated radiological criteria for chronicity were present together with acute findings. 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 residual respiratory symptoms and right ventricular dysfunction during follow-up. Results 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. The median modified Miller Score was 24 points and baseline mPAP was 35 mmHg in both groups. The absolute mPAP reduction after USAT was 11 (Q1-Q3: 5-17) mmHg in patients with <3 and 10 (Q1-Q3: 5, 17) mmHg in those with ≥3 criteria; Table 2. Three (1.7%) patients were diagnosed with CTEPH after a median of 3 months and underwent pulmonary endarterectomy: in all 3 patients, CTEPH was pre-existing. At least 3 of the 6 previously validated criteria were present in all CTEPH patients at index CT. In the 3 patients with acute PE on pre-existing CTEPH, the median baseline mPAP was much higher (median 53 mmHg) than in the remaining patient group and the absolute reduction after USAT was 9 mmHg, corresponding to a relative reduction of 19%. During follow-up, PPEI was more frequent in patients with <3 signs (n=4, 2.7%) than in those with ≥3 signs (n=4, 12.9%). Conclusion(s) The evaluation of six radiological parameters in initial CT scans 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 USAT in terms of mPAP reduction.Baseline characteristicsHemodynamic and clinical outcomes