Makindo Medical Notes

Related Subjects: |Pulmonary Stenosis |Pulmonary Regurgitation |Pulmonary Hypertension |Pulmonary Embolism

Secondary Pulmonary Hypertension - Cor Pulmonale

Shunts will always try to shift blood to the low-pressure pulmonary circulation, but this will cause pulmonary hypertension. Pulmonary hypertension may be primary or secondary depending on whether a secondary cause can be found and is based on the mean pulmonary artery pressure readings > 25 mmHg at rest and 30 mmHg during exercise.

About

• Pulmonary hypertension (PH)/cor pulmonale is defined as right heart failure due to lung disease, often associated with hypoxic conditions like COPD.
• Cor pulmonale is secondary pulmonary hypertension due to hypoxic vasoconstriction of pulmonary vessels and parenchymal and vascular changes, most commonly associated with emphysema.
• It involves chronic elevation of pulmonary artery pressure above 25 mmHg at rest or above 30 mmHg with exercise, though some definitions use a threshold of systolic pulmonary artery pressure > 40 mmHg.

Classification

• Pulmonary arterial hypertension
• Pulmonary venous hypertension
• PH associated with respiratory disease/hypoxia
• PH related to thrombosis or embolic disease
• PH due to disease of the pulmonary vasculature

Pathophysiology of Pulmonary Hypertension

• Increase in left ventricular (LV) filling pressure with normal pulmonary vascular resistance (PVR) (e.g., mitral stenosis).
• Pulmonary vascular disease with elevated PVR (e.g., pulmonary emboli).
• Parenchymal lung disease with elevated PVR (e.g., diffuse parenchymal lung disease - DPLD).
• A combination of these factors leading to increased pulmonary pressures.

Causes

• Chronic Obstructive Pulmonary Disease (COPD)
• Interstitial lung disease (e.g., idiopathic pulmonary fibrosis)
• Idiopathic - Primary Pulmonary Hypertension
• Multiple pulmonary emboli
• Congenital heart disease with Eisenmenger's syndrome
• Mitral stenosis
• Weakness of respiratory muscles (e.g., muscular dystrophies)
• Chest wall deformities (e.g., kyphoscoliosis)
• Sickle cell disease
• Use of certain drugs (e.g., dexfenfluramine)
• Left ventricular failure
• Left atrial myxoma
• Living at high altitude (chronic hypoxia)

Clinical

• Progressive breathlessness on exertion, particularly in patients with COPD.
• Signs of right heart strain: raised JVP, tricuspid regurgitation, loud P2 (accentuated pulmonary valve sound), and a right parasternal heave.
• Symptoms and signs of fluid overload: peripheral oedema, ankle swelling, and ascites in advanced stages.

Investigations

• FBC: Polycythaemia due to chronic hypoxia, raised WCC in secondary infections.
• U&E, LFTs, Bone profile, CRP: To assess baseline metabolic status and monitor for complications.
• ECG: Right ventricular hypertrophy (RVH), right bundle branch block (RBBB), and P pulmonale. RV strain pattern may also be present.
• Arterial blood gas (ABG): Hypoxia and hypercarbia in advanced stages.
• CXR: Enlarged pulmonary arteries and "pruning" of peripheral vessels, indicating advanced disease.
• Echo: Shows right ventricular dilatation and tricuspid regurgitation. It can estimate pulmonary pressures based on Doppler readings.
• CT-PA: To assess for chronic thromboembolic pulmonary hypertension (CTEPH) or other causes like pulmonary embolism.

Management

• Long-term oxygen therapy (LTOT): Essential for reducing hypoxaemia and pulmonary vasoconstriction, thereby reducing pulmonary hypertension and improving outcomes in COPD. Indicated for patients with a PaO₂ ≤ 7.3 kPa at rest. LTOT has been shown to reduce mortality and improve quality of life.
• Anticoagulation: Consider if pulmonary hypertension is due to recurrent pulmonary emboli. A low threshold should be maintained for investigating PE in these patients using CT-PA or ventilation-perfusion (V/Q) scanning. Anticoagulation may also be indicated in cases with atrial fibrillation.
• Diuretics: To manage fluid retention and reduce symptoms of peripheral oedema and ascites. Care must be taken not to over-diurese as this can impair right ventricular filling.
• Vasodilators and Calcium Channel Blockers: Limited use in secondary pulmonary hypertension; some patients with idiopathic forms may benefit, but this requires specialist evaluation.
• Management of underlying lung disease: Optimizing treatment for COPD, interstitial lung disease, or other underlying conditions is crucial.
• Heart-Lung Transplant: May be considered in advanced cases that are refractory to medical management and in younger patients with preserved function otherwise.
• Palliative care: Important in end-stage disease to manage symptoms and maintain quality of life, focusing on symptom relief like breathlessness and managing pain.