CT-based pulmonary artery measurements for the assessment of pulmonary hypertension

Abstract

Rationale and objectives: Pulmonary hypertension (PH) is a complex and fatal disease that is difficult to diagnose noninvasively. This study evaluated previously published computed tomography-based vessel measurement criteria and investigated the predictive power and diagnostic ability of the main pulmonary artery diameter (MPAD) and the ratio of MPAD to aorta diameter (rPA).

Materials and methods: The database for this study consisted of 175 PH patients (for whom mean pulmonary artery pressure [mPAP] was known), 16 patients without PH but with known mPAP (non-PH patients), and 114 "normal" patients without known mPAP. The performance of previously published criteria, MPAD > 29 mm and rPA > 1, was determined. The relationship between vessel measurements and mPAP was evaluated through correlation and linear regression analysis. The ability of these measurements to discriminate between patients with and without PH was determined by receiver operating characteristic analysis.

Results: For discriminating between PH and "normal" patients, the sensitivity and specificity of the criterion MPAD > 29 mm were 0.89 (0.84-0.93) and 0.83 (0.76-0.90), respectively, and the sensitivity and specificity of the criterion rPA > 1 were 0.89 (0.85-0.94) and 0.82 (0.74-0.89), respectively. At a specificity of 0.95 in the task of separating PH and "normal" patients, the sensitivity of MPAD was 0.81 (0.72-0.90) and the sensitivity of rPA was 0.76 (0.66-0.85), but the specificity for both decreased when non-PH patients were included. For the combined PH and non-PH patient groups, the correlation between the vessel measurements and mPAP was significant but low, and the ability of the vessel measurements to predict mPAP was limited.

Conclusion: This study found that the sensitivity of previously published vessel criteria for identifying PH patients is high, but the specificity may not be high enough for routine use in a clinical patient population.

Keywords: Pulmonary hypertension; pulmonary arterial hypertension; pulmonary arterial pressure; pulmonary artery diameter; vessel measurement.

Figure 1

Vessel measurements obtained from CT scans. (a) The diameter of an enlarged pulmonary artery (PA) from an IPAH patient (compare with the aorta (A) diameter). (b) An aorta and pulmonary artery diameter from a “normal” patient.

Figure 2

Scatter plot of mPAP versus MPAD for the combined PH and non-PH patient groups. Superimposed on the scatter plot is the line of regression from the linear model (MPAD) (straight solid line) with 95% prediction bands (straight dashed lines) and the line of regression from the linear-quadratic model (MPAD + MPAD²) (curved solid line) with 95% prediction bands (curved dashed lines).

Figure 3

Scatter plot of mPAP versus rPA for the combined PH and non-PH patient groups. Superimposed on the scatter plot is the line of regression for the linear model (rPA) (solid line) with 95% prediction bands (dashed lines).

Figure 4

Distributions of (a) measured MPAD values and (b) measured rPA values for the PH patients and the “normal” patients.

Figure 4

Distributions of (a) measured MPAD values and (b) measured rPA values for the PH patients and the “normal” patients.

Figure 5

Emprical and proper binormal model (PBM) ROC curves for the ability of MPAD (top left: PH vs “normal ”, top right: PH vs “normal ” + non-PH) and rPA (bottom left: PH vs “normal ”, bottom right: PH vs “normal ” + non-PH) to individually classify patients into two groups (those with PH and those without PH).