Diagnostic accuracy of CT pulmonary angiography in suspected pulmonary hypertension

Abstract

Objectives: Computed tomography (CT) pulmonary angiography is widely used in patients with suspected pulmonary hypertension (PH). However, the diagnostic and prognostic significance remains unclear. The aim of this study was to (a) build a diagnostic CT model and (b) test its prognostic significance.

Methods: Consecutive patients with suspected PH undergoing routine CT pulmonary angiography and right heart catheterisation (RHC) were identified. Axial and reconstructed images were used to derive CT metrics. Multivariate regression analysis was performed in the derivation cohort to identify a diagnostic CT model to predict mPAP ≥ 25 mmHg (the existing ESC guideline definition of PH) and > 20 mmHg (the new threshold proposed at the 6th World Symposium on PH). In the validation cohort, sensitivity, specificity and compromise CT thresholds were identified with receiver operating characteristic (ROC) analysis. The prognostic value of the CT model was assessed using Kaplan-Meier analysis.

Results: Between 2012 and 2016, 491 patients were identified. In the derivation cohort (n = 247), a CT model was identified including pulmonary artery diameter, right ventricular outflow tract thickness, septal angle and left ventricular area. In the validation cohort (n = 244), the model was diagnostic, with an area under the ROC curve of 0.94/0.91 for mPAP ≥ 25/> 20 mmHg respectively. In the validation cohort, 93 patients died; mean follow-up was 42 months. The diagnostic thresholds for the CT model were prognostic, log rank, all p < 0.01.

Discussion: In suspected PH, a diagnostic CT model had diagnostic and prognostic utility.

Key points: • Diagnostic CT models have high diagnostic accuracy in a tertiary referral population of with suspected PH. • Diagnostic CT models stratify patients by mortality in suspected PH.

Keywords: Diagnostic imaging; Heart ventricles; Hypertension, pulmonary; Pulmonary artery.

Fig. 1

Multi-figure CT images illustrating the CT measurements in a patient with PH with severe elevation of pulmonary artery pressure. Illustrations show the measurement of pulmonary artery and aortic diameter (a), right ventricular outflow tract thickness (b), interventricular septal angle (c) (reconstructed short-axis images) and left ventricular area (d). Images e and f illustrate the measurements required to calculate the RV/LV diameter ratio maximal RV diameter (e) and maximal LV diameter (f)

Fig. 2

Correlations of mean pulmonary arterial pressure with main pulmonary artery diameter (a), right ventricular outflow tract thickness (RVOT) (b), interventricular septal angle (c), left ventricular (LV) area (d) and RV/LV diameter ratio (e). f Correlation between septal angle and RV/LV diameter ratio

Fig. 3

Receiver operating characteristic analysis in a derivation cohort and validation cohort for diagnostic model A for prediction of mPAP ≥ 25 mmHg

Fig. 4

Prognostic significance of CT model A showing CT thresholds ((a) sensitive threshold and (b) compromise threshold) and mPAP thresholds ((c) mPAP ≥ 25 mmHg and (d) mPAP > 20 mmHg)