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Pulmonary Hypertension Classes 1–5 | MRCP Part 1|

TL;DR

Pulmonary hypertension is a frequently tested topic in MRCP Part 1, requiring clear understanding of classification, haemodynamics, and investigations. The Resp: Pulmonary Hypertension Classes 1-5 framework helps differentiate causes and guides diagnosis. Focus especially on Group 1 (PAH), Group 2 (left heart disease), and Group 4 (CTEPH), as these are commonly examined. Mastering these distinctions can quickly improve your score.


Why this matters

Pulmonary hypertension (PH) is a high-yield topic in MRCP Part 1, often appearing in cardiology and respiratory questions. Candidates are expected to classify PH accurately, interpret investigations, and identify key causes based on clinical clues.

The classification into five groups is not just theoretical—it directly informs management and is frequently tested in single-best-answer questions. For structured revision, start with the MRCP Part 1 overview and consolidate learning using Free MRCP MCQs.


Core sections

1. Definition and haemodynamics

Pulmonary hypertension is defined as:

  • Mean pulmonary arterial pressure (mPAP) ≥20 mmHg at rest (current definition)

Key haemodynamic classification:

  • Pre-capillary PH → PCWP ≤15 mmHg

  • Post-capillary PH → PCWP >15 mmHg

👉 Exam tip: Distinguishing these two is critical in MRCP stems.

2. WHO Classification of Pulmonary Hypertension (Classes 1–5)

Class

Name

Causes

Key Clue

1

Pulmonary arterial hypertension (PAH)

Idiopathic, BMPR2 mutation, CTD, HIV, drugs

Normal left heart

2

PH due to left heart disease

LV failure, mitral valve disease

Raised PCWP

3

PH due to lung disease/hypoxia

COPD, ILD, OSA

Chronic hypoxia

4

Chronic thromboembolic PH (CTEPH)

Recurrent PE

V/Q mismatch

5

Multifactorial

Sarcoidosis, haematological disorders

Mixed causes

👉 This table is a must-memorise for MRCP Part 1.

3. Five most tested subtopics

a) Group 1: Pulmonary arterial hypertension (PAH)

  • Causes: idiopathic, connective tissue disease (especially systemic sclerosis), HIV

  • Pathophysiology: endothelial dysfunction → vasoconstriction + vascular remodelling

  • Treatment: endothelin receptor antagonists, PDE-5 inhibitors

👉 MRCP clue: Young patient + dyspnoea + normal LV → think PAH

b) Group 2: Left heart disease

  • Most common cause of PH

  • Includes LV systolic/diastolic dysfunction and valvular disease

  • Elevated wedge pressure

👉 Key differentiator: raised PCWP distinguishes it from PAH

c) Group 3: Lung disease and hypoxia

  • COPD, ILD, obstructive sleep apnoea

  • Mechanism: hypoxic vasoconstriction

👉 Exam trap: Severe PH in COPD suggests another diagnosis

d) Group 4: Chronic thromboembolic PH (CTEPH)

  • Due to unresolved pulmonary emboli

  • Potentially curable

👉 Investigation of choice: V/Q scan

e) Group 5: Multifactorial

  • Sarcoidosis, chronic kidney disease, haematological disorders

  • Diagnosis of exclusion

4. Investigations

  • Echocardiography → screening tool

  • Right heart catheterisation → gold standard

  • V/Q scan → best screening for CTEPH

  • Pulmonary function tests → assess lung disease

  • BNP → severity/prognosis

👉 Key exam point: Diagnosis requires right heart catheterisation.

5. 10 high-yield points

  1. mPAP ≥20 mmHg defines PH

  2. Group 2 is most common

  3. PAH linked with connective tissue disease

  4. BMPR2 mutation → familial PAH

  5. PCWP differentiates PH types

  6. V/Q scan > CTPA for CTEPH

  7. COPD usually causes mild PH

  8. Right heart catheterisation confirms diagnosis

  9. PAH drugs not used in Group 2

  10. CTEPH is surgically treatable


Practical examples / mini-cases

MCQ:A 38-year-old woman presents with progressive dyspnoea. Echocardiography shows elevated pulmonary artery pressure but normal left ventricular function. Right heart catheterisation shows normal wedge pressure. She has systemic sclerosis.

What is the diagnosis? A. Group 2 PHB. Group 3 PHC. Group 1 PHD. Group 4 PH

Answer: C. Group 1 PH (PAH)

Explanation:

  • Normal wedge pressure → pre-capillary PH

  • Systemic sclerosis strongly associated with PAH

  • No evidence of lung disease or embolism


Common pitfalls (5 bullets)

  • Confusing PAH with left heart disease PH

  • Forgetting V/Q scan as first-line for CTEPH

  • Assuming COPD causes severe PH

  • Missing the need for right heart catheterisation

  • Using PAH drugs in Group 2 PH

MRCP Part 1 study setup with notes on pulmonary hypertension classification

FAQs

1. What is the most common cause of pulmonary hypertension?

PH due to left heart disease (Group 2) is the most common. Always consider cardiac causes first.

2. Which test confirms pulmonary hypertension?

Right heart catheterisation is the gold standard for diagnosis.

3. Why is V/Q scan preferred in CTEPH?

It is more sensitive than CTPA for detecting chronic thromboembolic disease.

4. Can pulmonary hypertension be cured?

Most types are managed medically, but CTEPH can be surgically cured.

5. What is the key exam differentiator between PH types?

Pulmonary capillary wedge pressure distinguishes pre- vs post-capillary PH.


Ready to start?

Strengthen your preparation with the MRCP Part 1 overview and practise using Free MRCP MCQs.

Test your readiness under exam conditions with a Start a mock test.


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