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Investigations


valvular disease (Group 2 PH) and congenital heart disease (group 1 PH). Intracardiac shunts may be determined via colour Doppler across sites of potential shunts, or through intravenous echo contrast injection. The position of the interventricular septum in Right ventricular function may be assessed non-invasively. Presence of pericardial effusions at diagnosis or during follow- up indicate a poor prognosis.16


EC is an


Figure 1: Example of lung perfusion scan, antero-posterior view. A large perfusion defect is seen in the apical segment of the left lower lobe and the lateral segment of the right middle lobe


obesity) should be referred for polysomnography.1


Obstructive sleep


apnoea is frequently associated with left heart disease and PH in this group is often multifactorial.


Lung imaging


Right ventricular enlargement and pericardial effusion may be present. Group 2 patients may have changes consistent with pulmonary congestion: ground glass opacities, septal thickening and pleural effusions and enlarged left heart. It is important to always consider pulmonary veno-occlusive disease, which has some radiological similarities to pulmonary congestion, with prominent interlobular septal thickening and mediastinal lymphadenopathy.9 Multislice CT pulmonary angiography has significantly improved the diagnosis of acute pulmonary embolism but has not yet superseded formal pulmonary angiography for the diagnosis of CTEPH, although a recent study with a 320-slice CT scanner suggests up to 97% sensitivity/specificity for central lesions.10,11


Computed tomography High-resolution lung computed tomography (CT) scan is mandatory for all PH patients. Patients with significant parenchymal disease (group 3) will be diagnosed by CT and lung-function testing and further invasive testing may be avoided. PAH and CTEPH patients may have normal CT scans or may have mosaic perfusion and enlarged pulmonary arteries (PA:aorta diameter >1).8


Ventilation-perfusion scan 6


The lung ventilation-perfusion (VQ) scan is a central and mandatory investigation


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in all patients with suspected PH (Figure 1).12


The presence of segmental or lobar perfusion defects on VQ scan without matched ventilation defects strongly suggests the diagnosis of CTEPH (group 4 PH) and mandates formal pulmonary angiography to confirm the diagnosis. A normal VQ scan effectively rules out significant CTEPH. Routine repeat of VQ scan is not required.


Patients with PAH may have heterogeneous perfusion of both lungs rather than segmental defects.


Pulmonary angiogram


Formal pulmonary angiography is indicated for all patients with suspected CTEPH.12


It is performed by inserting a


catheter into the main pulmonary arteries in a manner similar to that described below for RHC and injecting intravenous contrast into each artery in turn. Findings such as intravascular bands or webs, luminal narrowing or irregularities, pouches, abrupt termination of an arterial branch, complete lack of perfusion to a lobe indicate CTEPH and should trigger referral to an expert center for consideration of endarterectomy.


Echocardiography


Echocardiography (EC) has become an indispensable tool for PH management.13 Transthoracic EC is non-invasive and inexpensive. Pulmonary artery pressure (PAP) can be estimated by measuring tricuspid regurgitant jet velocity, and this makes EC an ideal modality for screening high-risk groups for presence of PH (for example, scleroderma, BMPR2 mutation carriers).14,15


EC


provides valuable diagnostic information concerning left ventricular function,


invaluable tool for follow-up of patients, although there is no consensus of which EC parameter gives the most information. The main limitations to EC is that many measurements are somewhat operator dependent.14


In


addition, transthoracic EC may underestimate mitral regurgitation and congenital heart lesions and expert opinion should always be sought if to proceed to transoesophageal EC. A discussion of the full potential of EC in PH is beyond the scope of this article, and the reader is referred elsewhere.13


Right heart catheterisation Right heart catheterisation (RHC) is the central diagnostic procedure in patients with PH.17


Despite significant advances


in cardiac/lung imaging, invasive measurement of pulmonary pressures remains mandatory. The RHC procedure is typically performed in the cardiac catheterisation suite or intensive care unit, with the patient supine and relaxed (minimal sedation and local anaesthesia is given). A balloon-tipped and fluid- filled catheter is introduced into a large vein and carefully navigated through the right atrium (RA), right ventricle (RV) and into the PA. At each anatomical site, the pressure-time tracing is recorded over several respiratory cycles and pressures are measured at end expiration. As the catheter is advanced inside the PA, the inflated balloon will eventually ‘wedge’ itself in a small PA. At this moment, the ‘pulmonary arterial wedge pressure’ (PAWP) wave recorded at the catheter tip will be isolated from the PA pressure wave and the wave will reflect left atrial pressure. Presence of high V waves in the PAWP indicates mitral regurgitation and may help to diagnose PH due to left heart disease. Cardiac output/index is determined by thermodilution or by the Fick technique. Blood samples may be obtained at different anatomical sites to determine oxygen saturation – a significant step-up in oxygen saturation from site to site


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