Dr Ramey Bajwa ( left ) Respiratory advanced trainee , Princess Alexandra Hospital , Brisbane , Queensland .

Dr Cerys Jones ( centre ) GP , Eastbound Medical Clinic , Melbourne , Victoria .

Dr Claire M Ellender ( right ) Consultant respiratory and sleep physician , Princess Alexandra Hospital , Brisbane , Queensland .

First published online on 12 April 2024

BACKGROUND

DYSPNOEA is a very common symptom

, with one in 10 Australian adults reporting clinically important dyspnoea . 1 In clinical practice , common causes include respiratory , cardiovascular and neuromuscular disease , and obesity .

GPs in Australia see about 900,000 patients per year with breathlessness , usually related to asthma , COPD or heart failure . However , about 8.5 % of patients presenting to their GP with dyspnoea do not have a cause identified , and this is more likely to occur in adults compared with children . 2

While pulmonary arterial hypertension ( PAH ) is a rare cause of dyspnoea , it is an important differential diagnosis to consider , as effective therapies are now available — and without treatment the average survival is only 2.8 years . 3 Early identification and treatment can prevent irreversible damage to the pulmonary vascular bed and dramatically improve prognosis .

Pulmonary hypertension ( PH ) is an umbrella term to describe all patients with an elevated mean pulmonary artery pressure . If left untreated , death can occur because

of progressive right ventricular ( RV ) failure ( see figure 1 ). Universally , the presence of PH confers a worse prognosis compared with patients without PH . 4 However , it is critical to identify the aetiology of the PH , as this has significant implications for prognosis and treatment decisions . The World Symposium on Pulmonary Hypertension Association has classified PH into five aetiological groups , based on haemodynamic results and relevant underlying disease ( s ), see box 1 . 3

It is important to note that PH and PAH should not be used synonymously . Treatments for PAH may include pulmonary vasodilator drugs , whereas patients with PH as a complication of left-sided heart disease , for example , may experience harm following prescription of pulmonary vasodilators .

The importance of early recognition and referral to a specialist centre for PAH is increasingly recognised . In Australia and New Zealand , the median time between symptom onset and diagnosis is 1.2 years ( interquartile range 0.6-2.7 years ) and a longer delay is associated with decreased five-year survival . 5 The COVID-19 pandemic has exacerbated this issue further , leading

to reduced referrals to specialist centres , difficulty obtaining relevant tests and disruptions to renewal of PAH medications . 6

The goal of PAH services is to provide early diagnosis and to quickly initiate therapy to normalise a patient ’ s functional state and reduce pulmonary artery pressure , in order to minimise the risk of long-term RV dysfunction .

The latest European Society of Cardiology / European Respiratory Society ( ESC / ERS ) guidelines have proposed a new , simplified diagnostic algorithm with a three-step approach ( see box 2 ).

GPs have an indispensable role in steps 1 and 2 . GPs are key members of the multidisciplinary team that will optimise care for those with an established diagnosis of PH , often a complex and heterogeneous group .

This How To Treat reviews the clinical presentation of adults with PH , offers information about when to suspect the condition , and the initial tests that can be helpful in the community setting . It aims to offer an overview of PH that assists with delivering holistic care for patients in the community .

Next time a patient presents with breathlessness , ask yourself “ Could this be PH ?”

EPIDEMIOLOGY

THE global prevalence of PH overall is 1 % and rises to approximately 10 % in patients over 65 . 7 To provide some context , the equivalent global prevalence for type 2 diabetes is 6.3 % and 15 % respectively . 8 The PH prevalence in the UK has doubled in the past 10 years to 125 cases per million inhabitants , likely because of increased awareness of the condition . 9

Prevalence varies depending on the aetiology ( see box 3 ). Note this list is not exhaustive .

AETIOLOGY AND PATHOGENESIS

THE pulmonary circulation in normal

adult subjects is a low-resistance

, high-flow circuit . PVR is 10-20 times lower than systemic vascular resistance . 10

There are three important molecules released by endothelial cells that are involved in controlling vasomotor tone of the pulmonary circulation — nitric oxide , prostaglandin I2 / prostacyclin and endothelin-1 ( ET-1 ).

In PAH , the microstructure of pulmonary vessels becomes damaged ( see figure 2 ), forming ‘ plexiform ’