Segmental pulmonary arterial hypertension occurs when the right and left pulmonary arteries are nonconfluent and receive blood supply from different sources. High blood pressure confined to limited lung segments may accelerate progression of pulmonary vascular resistance. Calculation of segmental vascular resistance and assessment of operability in such situations are done after integrating catheter hemodynamics, magnetic resonance imaging techniques, or perfusion scintigraphy. When an isolated pulmonary artery perfused by a restrictive ipsilateral arterial duct is associated with a large nonrestrictive contralateral arterial duct connected to the other pulmonary artery, leading to unilateral pulmonary arterial hypertension and features of high vascular resistance, it offers unique challenges to decision-making.