AN INTRODUCTION TO PULMONARY ARTERIAL HYPERTENSION FOR PRIMARY CARE

Pulmonary arterial hypertension (PAH) is a specific type of pulmonary hypertension (PH); an umbrella term for a group of diseases characterised by elevated blood pressure in the pulmonary arteries, which share the same general signs and symptoms but differ in their pathological findings, haemodynamic characteristics, and treatment strategies.1,2

Whereas PH is common and can be found in multiple diseases, PAH is a rare, progressive, and life-limiting condition with a poor prognosis.1–3 Without treatment, the median survival of patients with idiopathic PAH is 2.8 years.4 There is a general lack of awareness of the condition and therefore PAH is frequently associated with delayed presentation, diagnosis, referral, and treatment.1,3,5

The aim of this article is to give an overview of PAH for general practitioners (GPs). The GP will usually be the first doctor that the patient will present to and evidence suggests that early recognition of PAH can improve patient outcomes.6–10

DEFINITION OF PAH

PAH is a devastating and progressive disease caused by the narrowing of the pulmonary arteries which if left untreated leads to right heart failure and death.11,12

As it develops, restricted blood flow causes increasing strain and enlargement in the right side of the heart; this in turn decreases blood flow to the left heart and the systemic circulation to the lungs and the rest of the body leading to the typical symptoms of PAH.1,13 Click here to read more about the pathophysiology of PAH.

PAH is characterised by elevated pulmonary arterial pressure (≥25 mmHg at rest) as well as the presence of pre-capillary PH, defined by a pulmonary capillary wedge pressure ≤15 mmHg, and pulmonary vascular resistance >3 Wood units, in the absence of other causes of pre-capillary PH.1

 

EPIDEMIOLOGY

PAH is a rare condition, with an estimated prevalence of 10–50 cases per million population in Europe.11

PAH is more common in middle and older aged patients, women, and in certain at-risk patient groups; e.g. systemic sclerosis.1

It is considered that PAH may be severely under-recognised and under-diagnosed.3 This lack of awareness means patients are often only identified late in the course of the disease.14 Sadly, patients with severe disease at diagnosis have a significantly worse survival.15,16

CLASSIFICATION OF PAH

PH disorders are classified into 5 groups based on their underlying mechanisms, clinical context, and histopathology: PAH (Group 1), PH due to left heart disease (Group 2), PH due to lung diseases and/or hypoxaemia (Group 3), PH due to chronic thrombotic and/or embolic disease (Group 4), and PH with unclear and/or multifactorial mechanisms (Group 5).1

PAH is characterised by progressive vascular remodelling and can be:1

  • Idiopathic
  • Heritable
  • Drug- or toxin-induced
  • Associated with a condition, such as:
    • Connective tissue diseases (CTD)
    • Human immunodeficiency virus (HIV) infection
    • Portal hypertension
    • Congenital heart disease (CHD)
    • Schistosomiasis

According to a registry of patients in the US, the most common types of PAH are idiopathic (46.2%), PAH associated with CTD (25.3%) and PAH associated with CHD (9.9%).17

Click here to read more about the different types of PH and PAH.

 

CLINICAL CHARACTERISTICS

The clinical characteristics of PAH are non-specific and patients often present with a spectrum of symptoms.1

Common complaints at presentation include shortness of breath, dizziness, fatigue, weakness, and general exertion intolerance.1,3 These symptoms are mainly related to progressive right ventricular dysfunction and are typically induced by exertion. Only in the most advanced cases are symptoms evident at rest.1

The advice is to suspect PAH in cases of unexplained breathlessness, particularly in young patients and in the presence of predisposing conditions.2

Click here to read more about the signs and symptoms of PAH.

 

DIAGNOSIS

PAH is a challenging disease to identify.3 In recent years there has been increased emphasis on the correct and early diagnosis of PAH owing to the development of new and effective treatments that can delay progression and improve patient outcomes.12

Common misdiagnoses of PAH in primary care:3,6
  • Dyspnoea is easily mistaken for more common conditions, such as asthma
  • Lethargy and exercise intolerance are often attributed to a degree of unfitness
  • Symptoms may appear similar to anxiety and panic attacks

Assessment of PAH is based on a rigorous diagnostic algorithm from the European Society of Cardiology and the European Respiratory Society (ESC/ERS), which uses logical sequencing to determine risk of PAH, whether PAH is likely to be present based on initial non-invasive evaluations, and clarifying the underlying aetiology in an individual patient.1 Click here to read more about diagnosing PAH.

 

Figure 1: ESC/ERS condensed diagnostic algorithm. Adapted from Galiè et al 20161

 

The patient’s journey to diagnosis is often long and fraught, and characterised by limited awareness of PAH outside specialist centres, which can lead to prolonged periods of misdiagnosis, treatment delays, and an increasing sense of frustration and anger for patients.3

A survey of patients with PH in the UK found that 40% saw 4 or more doctors before receiving a diagnosis and almost half (48%) suffered delays of over a year between first experiencing symptoms and diagnosis.18 Click here to learn more about the study results.

 

Figure 2: Picture representation of a patient’s journey to diagnosis (Armstrong et al 20123)

REFERRALS

Interpretation of the tests described in the algorithm above is complex and requires specialist experience. Therefore, it is essential that patients are referred to a designated specialist centre with experience of identifying and managing PAH.1 There are currently 9 specialist PH centres in the UK and Ireland.

Such centres will be able to support patients and their families by offering detailed assessment of the patient, clinical management of patients with PAH-targeted drug therapies, and by working closely with other healthcare professionals in a multidisciplinary team.1,2

If you suspect PAH, please contact your closest centre for further information and details on how to refer. Click here for further details on the specialist centres.

TREATMENT

Although there is no cure, currently available PAH therapies can improve symptoms and slow progression with the aim of achieving and maintaining a low-risk status.1,12

In the last decade the treatment landscape for PAH has evolved and now includes 3 main steps:1,5

1. General measures (includes physical activity and rehabilitation, birth control advice, infection prevention, and psychosocial support) and supportive therapy (includes oral anticoagulants, diuretics, oxygen therapy, and digoxin)

2. High-dose calcium channel blockers in vasoreactive patients or drugs approved for PAH (includes endothelin receptor antagonists; phosphodiesterase type 5 inhibitors and soluble guanylate cyclase stimulators; and prostacyclin receptor agonist and prostacyclin analogues) in non-vasoreactive patients according to the risk

3. Combination therapy of PAH-targeted drugs or surgical intervention (balloon atrial septostomy, lung transplantation) in patients who do not respond to advanced therapies

Click here to read more about the treatment and prognosis of PAH.

 

General measures for GPs to consider 2,5,6

  • Educate yourselves; with a focus on the differences between PH and PAH
  • Help increase awareness of PAH in your clinical practice
  • Suspect PAH in cases of unexplained breathlessness, particularly in younger patients and those with predisposing conditions
  • Be aware that symptoms may not be obvious and can be similar to common conditions such as asthma, dyspnoea, chronic obstructive pulmonary disease, heart failure
  • For a patient with suspected PH, the initial referral is usually to the local cardiology or respiratory team who will then refer the patient on to a specialist PH centre if necessary
  • GPs also have a role in the ongoing care of patients with PAH, for example:
    • Discussion and collaboration with the specialist PH centre about a patient’s condition and particular needs
    • Safety monitoring of patients taking PAH-targeted drugs, including any tests required; e.g. liver function and haemoglobin tests if taking endothelin-receptor antagonists
    • Collaboration with social, community, and palliative care services as required; e.g. for oxygen needs or home aids such as stair lifts

CONCLUSION

PAH is a rare but serious condition that is affected by limited awareness among healthcare professionals outside specialist treatment centres. GPs can work to familiarise themselves with guidelines and diagnostic pathways to expedite diagnosis and referral of patients for specialist management and improved outcomes.

References

  1. Galiè N, et al. Eur Hear J 2016;37(1):67–119.
  2. Galiè N, et al. Breathe 2015;11(3):233–6.
  3. Armstrong I, et al. BMJ Open 2012;2(2):e000806.
  4. D'Alonzo G, et al. Ann Intern Med 1991;115:343–9
  5. Connolly MJ and Kovacs G. Br J Gen Pract 2012;62(604):e795–7.
  6. Ricketts C and Church C. Prescriber 2017;28(3):27–33.
  7. Humbert M, et al. Circulation 2010;122(2):156–63.
  8. Humbert M, et al. Eur Respir J 2010;36(3):549–55.
  9. Condliffe R, et al. Am J Respir Crit Care Med 2009;179(2):151–7.
  10. Dimopoulos K, et al. Circulation 2010;121(1):20–5.
  11. Hoeper MM and Gibbs SR. Eur Respir Rev 2014;23(134):450–7.
  12. Montani D, et al. Orphanet J Rare Dis 2013;8:97.
  13. Galiè N, et al. Eur Heart J 2009;30:2493–537.
  14. Humbert M, et al. Am J Respir Crit Care Med 2006;173(9):1023–30.
  15. Boucly A, et al. Eur Respir J 2017;50:1700889
  16. Farber H, et al. Chest 2015;148:1043–54
  17. Badesch DB, et al. Chest 2010;137:376–87
  18. Pulmonary Hypertension Association UK. What it means to live with PH today. 2017. Available from: www.phauk.org. Accessed July 2019.

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