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The term pulmonary hypertension refers to a serious condition characterised by high pulmonary vascular pressure, mainly as a consequence of various cardiac and respiratory diseases. Current clinical classification of pulmonary hypertension considers five distinct groups. Transthoracic echocardiography represents the first and most important noninvasive screening tool for estimating the probability of pulmonary hypertension. The diagnostic approach to pulmonary hypertension is supported by a proposed algorithm, which identifies the underlying cause. The definitive diagnosis and classification of pulmonary hypertension requires invasive confirmation of an elevated pulmonary artery mean pressure during a right heart catheterisation at rest. Pulmonary artery wedge pressure assessment has a pivotal role in differentiating precapillary from postcapillary pulmonary hypertension. The correct acquisition and interpretation of invasive pulmonary haemodynamic variables play a central role, not only in confirming the diagnosis but also in prognostication and treatment decision-making. During right heart catheterisation correct zero levelling of the external pressure transducer and pressure tracing readings at end-expiration should be assured. Obese patients and patients with obstructive lung diseases require special attention, given that spontaneous positive end-expiratory intrathoracic pressures are frequently observed. Because pressure and flow determinations with a fluid-filled flow-directed thermodilution catheter are potentially insufficiently precise, it is recommended to average at least three measurements. Acute vasoreactivity testing is indicated only in selected patients. Recent data suggest that invasive pulmonary haemodynamic measurement during exercise may be more sensitive than resting haemodynamics for early diagnosis, for treatment response assessment and for prognostic purposes.

Dual-energy computed tomography (DECT) angiography of the chest provides a combined morphological and functional analysis of the lung, usually obtained in a single acquisition without extra radiation or injection of extra intravenous iodine contrast. The parenchymal iodine maps generated by DECT are well correlated with scintigraphy, and are becoming an essential tool for evaluating patients with pulmonary vascular diseases. With a single DECT acquisition, complete imaging of pulmonary hypertension is now available, displaying vascular anatomy, parenchymal morphology and functional assessment. Triangular pulmonary perfusion defects in chronic thromboembolic pulmonary hypertension may be clearly analysed even in the presence of distal arterial occlusion. Perfusion heterogeneities seen in patients with pulmonary arterial hypertension reflect mosaic perfusion and may be helpful for the diagnosis, severity assessment and prognosis of the disease. Vascular or parenchymal abnormalities can also be analysed with perfusion defects to determine their aetiology. Pulmonary arterial hypertension due to congenital heart disease can be assessed with a single DECT, even in the neonatal population. Furthermore, new applications are emerging with ventilation imaging or myocardial perfusion imaging obtained by DECT and should be considered. In conclusion, DECT of the thorax enables the simultaneous and noninvasive assessment of vascular anatomy, parenchymal morphology and functional pulmonary imaging in various groups of PH.