Definition, classification and diagnosis of pulmonary hypertension

Abstract

Pulmonary hypertension (PH) is a haemodynamic condition characterised by elevation of mean pulmonary arterial pressure (mPAP) >20 mmHg, assessed by right heart catheterisation. Pulmonary arterial wedge pressure (PAWP) and pulmonary vascular resistance (PVR) distinguish pre-capillary PH (PAWP ≤15 mmHg, PVR >2 Wood Units (WU)), isolated post-capillary PH (PAWP >15 mmHg, PVR ≤2 WU) and combined post- and pre-capillary PH (PAWP >15 mmHg, PVR >2 WU). Exercise PH is a haemodynamic condition describing a normal mPAP at rest with an abnormal increase of mPAP during exercise, defined as a mPAP/cardiac output slope >3 mmHg/L/min between rest and exercise. The core structure of the clinical classification of PH has been retained, including the five major groups. However, some changes are presented herewith, such as the re-introduction of "long-term responders to calcium channel blockers" as a subgroup of idiopathic pulmonary arterial hypertension, the addition of subgroups in group 2 PH and the differentiation of group 3 PH subgroups based on pulmonary diseases instead of functional abnormalities. Mitomycin-C and carfilzomib have been added to the list of drugs with "definite association" with PAH. For diagnosis of PH, we propose a stepwise approach with the main aim of discerning those patients who need to be referred to a PH centre and who should undergo invasive haemodynamic assessment. In case of high probability of severe pulmonary vascular disease, especially if there are signs of right heart failure, a fast-track referral to a PH centre is recommended at any point during the clinical workup.

FIGURE 1

Suggested diagnostic approach to pulmonary hypertension (PH). Steps 1–5 represent the most important diagnostic steps of PH from the first presentation of the patient with symptoms or an existing risk condition towards final diagnosis with invasive assessment. WHO-FC: World Health Organization functional class; BNP: brain natriuretic peptide; NT-proBNP: N-terminal pro-BNP; TRV: tricuspid regurgitation velocity; 2D: two-dimensional; ABG: arterial blood gases; PFT: pulmonary function testing; D_LCO: diffusion capacity of the lung for carbon monoxide; CT: computed tomography; PG: polygraphy; ONO: overnight oximetry; V′/Q′ scan: ventilation/perfusion scan of the lung; 6MWT: 6-min walk test; CPET: cardiopulmonary exercise testing; MRI: magnetic resonance imaging; RHC: right heart catheterisation; PH-ILD: pulmonary hypertension associated with interstitial lung disease; PAH: pulmonary arterial hypertension; CTEPH: chronic thromboembolic pulmonary hypertension; cpcPH: combined post- and pre-capillary PH. ^#: refer to figure 2.

FIGURE 2

Most important two-dimensional and Doppler indices of pulmonary hypertension (PH) in transthoracic echocardiography. RV: right ventricle; RA: right atrium; RVOT: right ventricular outflow tract; PA: pulmonary artery; PV: pulmonary valve; LV: left ventricle; LVEI: left ventricle eccentricity index; RVEDa: right ventricular end-diastolic area; RVESa: right ventricular end-systolic area; RVEDV: right ventricular end-diastolic volume; TAPSE: tricuspid annular plane systolic excursion; IVC: inferior vena cava. Images courtesy of E. Ashley Hardin (University of Texas Southwestern Medical Center, Dallas, TX, USA).