Do radiologists detect chronic thromboembolic disease on computed tomography?

Abstract

Background: Acute pulmonary embolism (APE) is a potentially severe medical condition with blood clots obstructing the pulmonary arterial vasculature. In most cases the APE resolves without any sequelae after anticoagulation therapy. In some patients, however, the emboli do not resolve upon treatment and the remnants cause increased vascular resistance, a condition known as chronic thromboembolic pulmonary hypertension (CTEPH). Both APE and CTEPH have a non-specific clinical presentation and imaging is an important part of the diagnosis. In APE computed tomography pulmonary angiography (CTPA) is the diagnostic gold standard, although the method is not suitable for all patients. CTPA has a high specificity for CTEPH, but the sensitivity remains under debate. At present CTPA is not recommended as a first line test among patients with a clinical suspicion of CTEPH. Purpose: To investigate unestablished imaging modalities in the diagnosis of APE (Study I) and CTEPH (Study III) including learning aspects (Study II) and knowledge (Study IV) of theses among radiologists. Regarding APE we studied magnetic resonance imaging (MRI) and in CTEPH we studied CTPA. Material and methods: Studies I-II were based on a prospective collection of 70 unenhanced MRI exams with CTPA as the gold standard. In Studies III-IV we used a retrospective material based on 43 CTPA exams from patients with confirmed CTEPH referred for presurgical assessment at a specialist centre, with a matched control with suspected APE. Results: All MRI exams were of diagnostic quality. Specificity was 100% for both readers and sensitivity 90% and 93% respectively with a nearly perfect inter-reader agreement (kappa 0.97) (Study I). Residents interpreting the MRI exams within the training program reached a clinically acceptable level after approximately 50 examinations and review time was halved during the training program (Study II). The sensitivity for CTEPH on CTPA reviewed by two experts was 100% and the specificity 100% (Study III), while the sensitivity based on the original reports from the same cases was 26% (Study IV). Conclusions: Unenhanced MRI has a high sensitivity and specificity for APE (Study I) and residents can learn to interpret such exams by using a self-directed training program (Study II). Enhanced CTPA has a high sensitivity when reviewed by experienced radiologists (Study III), but among radiologists in general the sensitivity is low (Study IV). LIST OF SCIENTIFIC PAPERS I. Detection of pulmonary embolism using repeated MRI acquisitions without respiratory gating: A preliminary study.

Optimizing the diagnosis and assessment of chronic thromboembolic pulmonary hypertension with advancing imaging modalities

“…Also, radiologists need to be trained and experienced in assessing imaging findings of CTEPH, as demonstrated in a study assessing original CT reports from patients with confirmed CTEPH diagnosis referred to an expert PEA center (n = 35). 32 Although most cases were visible with CT in this study, only 26% of reports identified CTEPH or signs of CTEPH, leading to a falsely low sensitivity for CT. In patients with CTEPH, the use of electrocardiogram (ECG)-synchronized techniques in ECG-gated CT can provide detailed visualization of segmental and subsegmental vessels, lung parenchyma, and RV myocardial size and morphology, especially in the left lower lobe.…”

Importance of computed tomography in defining segmental disease in chronic thromboembolic pulmonary hypertension

“…Although a ventilation/perfusion scan remains the recommended imaging modality for screening for CTEPH, CTPA is routinely used to confirm the presence of chronic pulmonary emboli in patients with an abnormal ventilation/perfusion scan [2]. In addition, although its role is underreported, CTPA may also identify patients with CTEPH at the time of acute pulmonary embolism where CTEPH was unsuspected [13,14]. Compared with conventional angiography, CTPA is noninvasive, faster to perform, generates lower radiation and is less operator dependent.…”

Identification of chronic thromboembolic pulmonary hypertension on CTPAs performed for diagnosing acute pulmonary embolism depending on level of expertise

“…Similar results to ours were found in a previous study retrospectively evaluating CTPA reports in which (signs of] CTEPH were mentioned in only 9 of 35 (26%] reports. [7] Of note, in daily practice, CTPAs are frequently assessed by Abbreviations: PE, pulmonary embolism; CTEPH, chronic thromboembolic pulmonary hypertension; VTE, venous thromboembolism; COPD, chronic obstructive pulmonary disease. radiologists without specific expertise in thoracic radiology since patients with suspected acute PE often present out of office hours.…”

“…[4] Confirmation of prevalent findings suggestive of CTEPH have been confirmed by recent studies, although it has also been suggested that radiologists rarely report these signs. [1,[5][6][7][8] More detailed assessment of index CTPAs may therefore lead to earlier identification of patients with (high risk of developing) CTEPH, which is associated with better prognosis. [9) In the InShape III study, three expert chest radiologists scored signs of chronic thrombi and pulmonary hypertension on CTPA scans performed for suspected acute PE in 50 PE patients who were subsequently diagnosed with CTEPH during follow-up ('cases'), and in 50 PE patients in whom sequential echocardiograms performed >2 years after the acute PE diagnosis had not shown any signs of pulmonary hypertension ('controls').…”