Usefulness of standard computed tomography pulmonary angiography performed for acute pulmonary embolism for identification of chronic thromboembolic pulmonary hypertension: results of the InShape III study.

BACKGROUND: Chronic thromboembolic pulmonary hypertension (CTEPH) is often diagnosed after a long delay, even though signs may already be present on the computed tomography pulmonary angiogram (CTPA) used to diagnose a preceding acute pulmonary embolism (PE). In this setting of suspected acute PE, we evaluated the diagnostic accuracy of dedicated CTPA reading for the diagnosis of already existing CTEPH.
METHODS: Three blinded expert radiologists scored radiologic signs of CTEPH on initial CTPA scans with confirmed acute PE in 50 patients who were subsequently diagnosed with CTEPH during follow-up (cases), and in 50 patients in whom sequential echocardiograms performed >2 years after the acute PE diagnosis did not show any signs of pulmonary hypertension (controls). All 50 control index CTPA scans had signs of right ventricular (RV) overload. Sensitivity and specificity of expert CTPA reading was calculated, and best-predicting radiologic parameters were identified.
RESULTS: The overall expert reading yielded a sensitivity of 72% (95% confidence interval [CI] 58%-84%) and a specificity of 94% (95% CI 83%-99%) for CTEPH diagnosis. Multivariate analysis identified 6 radiologic parameters as independent predictors: intravascular webs; pulmonary artery retraction or dilatation; bronchial artery dilatation; right ventricular (RV) hypertrophy; and interventricular septum flattening. The presence of 3 or more these parameters was associated with a sensitivity of 70% (95% CI 55%-82%), a specificity of 96% (95% CI 86%-100%), and a c-statistic of 0.92.
CONCLUSIONS: Standardized reading of CTPA scans performed for acute PE can be useful for the diagnosis of CTEPH when structured identification of 6 characteristics is employed during interpretation. The use of this strategy may help reduce diagnostic delay of CTEPH.