Resp - Pulmonary HTN

Question 1

What are the causes of pulmonary hypertension?

Answer 1

1. Primary arterial hypertension- HIV associated- Idiopathic/inherited- Veno-occlusive disease
2. PH secondary to left heart disease- Systolic dysfunction- Diastolic dysfunction- valvular disease
3. PH secondary to lung disease- COPD- ILD- OSA
4. CTEPH
5. Multifactorial/unclear aetiology- Sarcoid- Myeloproliferative disorders

Question 2

What is pulmonary hypertension?

Answer 2

Pulmonary arterial hypertension is defined as a mean pulmonary artery pressure
(MPAP) of ≥25 mmHg at rest, or ≥30 mmHg with exercise. Pulmonary venous
hypertension is defined as an elevated PCWP ≥18 mmHg.

Question 3

How would you manage a patient with acute pulmonary hypertension?

Answer 3

Resuscitate in ABCDE approach.Treat underlying cause.
1. Treat underlying cause
2. Optimise RV preload- Cautious fluids- Diuretics/RRT
3. Reduce RV afterload
- Avoid: hypoxia, hypercapnia, atelectasis
- Low ventilatory pressures, low PEEP
- Pulmonary artery dilatation: Inhaled nitric oxide, Sildenafil (Prostacyclin)
4. Improve RV contractility- inotropes- Vaso over NA
5. Liase with specialist centres:- Pulmonary hypertension- ECMO

Question 4

Describe the pathophysiology of pulmonary hypertension

Answer 4

1 Increased flow
i Left-to-right shunting in congenital heart disease
ii Back-up of flow due to LV dysfunction or valvular heart disease leading to
raised venous pressure and eventually raised arterial pressure
This results in vascular smooth muscle remodelling, capillary congestion
causing lymphatic distension, and subsequent compensatory pulmonary
arterial hypertension to drive flow forward.

2 Pulmonary arterial vasoconstriction
i Endothelial dysfunction
– In idiopathic PAH, endothelial dysfunction leads to reduced production
of endothelium-derived vasodilators, e.g. nitric oxide
– There is intimal proliferation and medial hypertrophy leading to fibrosis,
which then promotes platelet aggregation and thrombosis
ii Hypoxic pulmonary vasoconstriction (HPVC)
– This is a physiological response and occurs chronically in lung disease
– Mechanically induced stress due to lung hyperinflation can cause further
capillary destruction

3 Small pulmonary vessel structural change or destruction
i Pulmonary veno-occlusive disease involves widespread vascular obstruction,
commonly in the post-capillary venules
ii Pulmonary capillary haemangiomatosis involves obstruction of the alveolar
capillary bed
iii Chronic thromboembolic disease causes mechanical obstruction and
increased arterial resistance to flow

Question 5

What might the ECG show in a patient with pulmonary
hypertension?

Answer 5

The ECG is likely to show signs of RVH
1 P pulmonale, particularly in leads II and V1 (represents right atrial
enlargement)
– P wave amplitude >2.5 mm in inferior leads and >1.5 mm in V1 and V2
2 Right axis deviation
3 Tall R wave in V1 and V2
4 RBBB
5 RV strain pattern: ST depression and T wave inversion in V1-V3 and the
inferior leads

Question 6

What is cor pulmonale?

Answer 6

Cor pulmonale is defined as acute or chronic pressure overload of the right
ventricle in response to pulmonary hypertension. The pathophysiology is
- Inc PVR, inc RV afterload
- RV pressure overload
- Myocardial remodelling and RV hypertrophy
- RV dilatation
- Inc RVEDV
- Dec LVEDV, poorer RV Contractility, inc RV wall stress
- all contributing to RV failure/cor pulmonale

Question 7

How would you manage chronic pulmonary HTN>

Answer 7

1 LTOT for advanced COPD
– Improves survival in patients with hypoxaemia
– Oxygen reduces HPVC, improving RV stroke volume and CO
2 NIV may be beneficial in exacerbations of COPD or in obstructive sleep apnoea
(OSA)
– No data exist on outcome benefit in acute cor pulmonale
– Corrects hypoxaemia and acidosis, thus offloads the RV by reducing PA
pressure
3 Pulmonary endarterectomy for pulmonary veno-occlusive disease
– 5–10% operative mortality compared to <10% five-year survival in
untreated disease
4 Anticoagulation in chronic thromboembolic pulmonary hypertension

Question 8

What medical therapies can be used in Pulmonary hypertension?

Answer 8

1 Diuretics to manage RV failure and volume overload
2 Vasodilators improve CO by decreasing RV afterload
i Prostacyclins, e.g. IV epoprostenol (administered centrally), inhaled iloprost
(prostacyclin analogue)
– Improves haemodynamics, symptomatology and outcome in pulmonary
hypertension
ii Endothelin-receptor antagonists, e.g. oral bosentan
– Significant improvement in symptoms and short-term outcomes
– Side effects may limit use
iii Phosphodiesterase inhibitors, e.g. IV or oral sildenafil (a PDE5 inhibitor)
– Improve exercise capacity but no improvement in long-term outcomes