Pulmonary artery dilation in pulmonary arterial hypertension: haemodynamic determinants and association with sudden death

Background: Pulmonary artery (PA) dilation is common in pulmonary arterial hypertension (PAH), yet its prognostic role and haemodynamic determinants remain poorly defined. We aimed to assess the prognostic significance of PA dimension for all-cause mortality and sudden death (SD), and to identify haemodynamic determinants of PA size and its longitudinal changes. Methods and results: In this retrospective observational study, we included consecutive PAH patients who underwent baseline (n = 754) and follow-up (n = 333) computed tomography pulmonary angiography and right heart catheterisation. PA diameter, haemodynamic, and clinical data were collected. The primary outcome was all-cause mortality; the secondary outcome was the risk of SD. PA diameter was not an independent predictor of all-cause mortality; however, a value ≥40 mm independently predicted SD [sHR 3.93 (1.86-8.30), p < 0.001]. Mean pulmonary arterial pressure (mPAP) was independently associated with PA size and its progression over time. Specifically, a reduction in mPAP ≥12 mmHg or achieving mPAP ≤35 mmHg was associated with attenuated PA enlargement. The incidence of SD declined over the study period; this temporal trend coincided with increased recognition and screening for left main coronary artery (LMCA) compression, although a definite causal relationship cannot be inferred. Conclusion: In PAH, PA dilation ≥40 mm predicts SD but not all-cause mortality. mPAP is associated with both baseline PA size and its progression. Whether aggressive haemodynamic optimisation and early identification of LMCA compression can prevent SD requires prospective validation.