Identification of chronic thromboembolic pulmonary hypertension on standard computed tomography pulmonary angiography for suspected acute pulmonary embolism

Background: Chronic thromboembolic pulmonary hypertension (CTEPH) is often diagnosed after a long delay, even though signs of CTEPH may already be present on the computed tomography pulmonary angiogram (CTPA) used to diagnose a preceding acute pulmonary embolism (PE). Diagnostic delay may be associated with worse prognosis. In this study we evaluated the diagnostic accuracy of extensive CTPA reading for predicting a future CTEPH diagnosis after acute PE. Method(s): Three expert radiologists scored radiological signs of CTEPH on CTPA performed for suspected acute PE in 50 PE patients who were subsequently diagnosed with CTEPH during follow-up with right heart catheterisation ("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"). Cases and controls were matched on RV-to-LV ratio on baseline CTPA. Sensitivity and specificity of expert CTPA reading for predicting future CTEPH was calculated, and best predicting radiological parameters were identified by conditional backward multivariate analysis. Result(s): 75% of cases had signs of acute PE and 94% signs of chronic PE and/or PH. The overall expert adjudication yielded a sensitivity of 72% (95% CI 58-84%) and a specificity of 94% (95% CI 83-99%) for a future CTEPH diagnosis. We identified six objective, independent radiological predictors of CTEPH: intravascular webs, pulmonary artery retraction or dilatation, bronchial artery dilatation, right ventricle hypertrophy and interventricular septum flattening (Figure 1). The presence of >=3 of 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. Conclusion(s): In our cohort, expert radiologists identified 36 out of 50 PE patients with a future CTEPH diagnosis. The most probable explanation is that most of them already had CTEPH at the moment of the PE diagnosis. Our findings support the hypothesis that dedicated CTPA reading in patients with confirmed PE may lead to faster CTEPH diagnosis.