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Investigations


Investigating the patient with pulmonary hypertension


The aims of investigation of pulmonary hypertension are twofold: first to make the correct diagnosis; second, to obtain functional/prognostic information. Invasive haemodynamic assessment is almost always required


Benjamin D Fox MBBS MRCP Director of Pulmonary Hypertension Service Rabin Medical Center, Israel


Once the clinical assessment of the pulmonary hypertension (PH) patient has been completed, thorough investigations are required. The aims of investigation are twofold: first to make the correct diagnosis; and second, to obtain functional/prognostic information. The exact combination of investigations required should ideally be determined by a PH specialist.1


In all cases where PH is


strongly suspected, right heart catheterisation (RHC) must be performed. Investigations with relatively low diagnostic yield (chest radiography, electrocardiogram) and novel research- based techniques (for example, magnetic resonance imaging) are not discussed in the interests of brevity.


Blood tests


For diagnosis of group 1 PH, it is required to send blood for collagen, vascular diseases, HIV and liver function tests.1 Thyroid dysfunction is also common in patients with pulmonary arterial hypertension (PAH), and should be screened for and treated.2


Arterial blood


gases may be requested, typically showing hypoxaemia, although this is a non- specific finding common to all PH groups. Presence of hypercapnia on arterial blood gases almost invariably represents chronic lung disease (group 3)-related PH. Screening for thrombophilia is not required in patients with chronic thromboembolic pulmonary hypertension (CTEPH), although the disease may be associated with anti-phospholipid


antibodies in some cases.3


Genetic testing


for bone morphogenetic protein receptor type 2 (BMPR2) and other mutations associated with PH is available but not routine in most centres.


For staging and prognostication, there has been significant interest in brain natriuretic peptide (BNP) and its pro-enzyme, N-terminal of the prohormone brain natriuretic peptide (NT-proBNP). Levels of these enzymes are increased by any disease causing atrial stretching, including PH. High levels of BNP/NT-proBNP are associated with poor prognosis and a decrease in NT-proBNP is associated with clinical improvement.4


Hyponatraemia and


hyperuricaemia have also been suggested as prognostic markers for PAH patients.5,6


Lung function tests


Full lung function testing (spirometry, lung volume determination, diffusion capacity for carbon monoxide (DLCO)) are mandatory for all patients referred for


investigation of PH.1


Patients with


parenchymal lung diseases causing PH will have severe obstructive or restrictive deficits (forced vital capacity (FVC) or forced expiratory volume in 1 second (FEV1) <60%). Patients with PAH may have mild restrictive deficits on lung mechanics with a moderate reduction in DLCO. Severe reduction in DLCO is seen in parenchymal lung diseases (fibrosis/ emphysema), scleroderma-associated PAH and pulmonary veno-occlusive disease. Recently, a syndrome of combined emphysema and fibrosis with severe PH has been reported.7


These


patients are classified as group 3 PH although their lung function may appear fairly normal, presumably because the hyper-expanded emphysematous upper lobes ‘balance’ the contracted fibrotic lower lobes, DLCO is severely decreased.


Polysomnography


Patients with risk factors for, and/or a clinical history compatible with sleep-


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