Prognostic Value of Main Pulmonary Artery Diameter in Pulmonary Arterial Hypertension.

Background: Accurate risk stratification is critical aspect of pulmonary arterial hypertension (PAH) management. It is unclear whether main pulmonary artery (MPA) enlargement offers additional prognostic value to validated risk scores.

Research question: Is MPA diameter prognostic in PAH, independent of the existing risk scores?

Study design and methods: A retrospective review of patients with PAH from 2 large referral centers was conducted. Baseline Registry to Evaluate Early and Long-Term PAH Disease Management (REVEAL) 2.0, REVEAL Lite 2, and European Society of Cardiology and European Respiratory Society scores were calculated. The primary end points were composite death, lung transplantation, and right heart failure hospitalization. Cox proportional hazards models were used for time-to-event analyses. Receiver operator characteristic and net reclassification improvement analyses additionally assessed the prognostic value of MPA diameter.

Results: Three hundred fifty-one patients were included. Baseline mean (SD) MPA diameter was 35.3 (7.1) mm. MPA grew by a mean (SD) of 0.4 (1.1) mm/y (1.1% baseline diameter). Over a mean (SD) of 4.0 (3.4) years of follow-up, 190 primary events occurred, and MPA diameter was a predictor (hazard ratio [HR], 1.06/mm; 95% CI, 1.04-1.07/mm; P < .001). MPA diameter remained an independent predictor after multivariable adjustments for the 3 risk scores and their individual components. MPA growth rate also predicted the outcome (HR, 1.79/mm/y; 95% CI, 1.52-2.11/mm/y; P < .001), independent of baseline MPA diameter. Area under the receiver operating characteristic curve for the risk of the primary end point at 1 year was similar for MPA alone (0.72) compared with the 3 risk scores (0.72-0.75). Furthermore, using MPA in addition to REVEAL 2.0 score resulted in risk reclassification in 23% of patients, mostly because of appropriate risk downgrading.

Interpretation: MPA diameter is a significant independent predictor of adverse clinical events in patients with PAH without congenital heart disease. It may be a novel prognostic marker in addition to the existing risk scores.