The prevalence of critical ab extrinsic compression of left main coronary artery (LMCA) is very high in patients with pulmonary arterial hypertension (PAH) symptomatic for angina (up to 40% according to a recent study of 121 patients with PAH). The element that most of all correlates with the degree of coronary stenosis is the diameter of the pulmonary artery (PA). In particular, a diameter ≥ 40 mm has a sensitivity of 83% and a specificity of 70% in patients with angina. Critical stenosis of LMCA is a risk factor for sudden death and in these condition percutaneous coronary angioplasty with stent implantation has proven to be a safe and effective long-term procedure. Preliminary data from a retrospective analysis of the registry of patients with PAH in Bologna (ARCA registry, 109/2016/U/Oss) highlights that even in PAH patients asymptomatic for angina, compression of LMCA can occur in up to 13% of patients and the main predictive parameter of compression was found to be a diameter ≥ 42 mm (with a sensitivity of 87% and a specificity of 77%). Performing a screening test by coronary-CT scan in all subjects suffering of PAH with a PA diameter ≥ 40 mm even if asymptomatic for angina could therefore help to identify patients with PAH at increased risk for sudden death at an early stage.