- Clinical science
Pulmonary hypertension (PH) is elevated pressure in the pulmonary arteries ≥ 25 mm Hg at rest. It can be idiopathic or due to chronic pulmonary (e.g., COPD, chronic sleep apnea) and/or cardiac disease (e.g., mitral valve disease). Over time, the rise in pressure may result in structural changes (e.g., dilation or hypertrophy) or impaired function of the right ventricle. If these changes are secondary to diseases of the lungs or the pulmonary artery system, the condition is referred to as cor pulmonale. While PH and cor pulmonale are often asymptomatic in early stages, symptoms like dyspnea on exertion, fatigue, cyanosis, and syncope appear in later stages. In decompensated cor pulmonale, the risk of arrhythmias and death is high. Echocardiograms are used as an initial non-invasive test to estimate the pulmonary artery pressure and to demonstrate an altered structure of the right ventricle. Right heart catheterization provides the definite diagnosis and the exact mean pulmonary arterial pressure (mPAP). Treatment mainly consists of management of the underlying causes of PH and cor pulmonale. Supplemental oxygen, pulmonary vasodilators, and diuretics may be given to reduce pulmonary artery hypertension and improve blood oxygenation. Lung transplantation is the treatment of last resort in refractory cases.
- Pulmonary hypertension: chronically elevated mean pulmonary arterial pressure (mPAP) at rest ≥ 25 mm Hg (normal: 10–14 mm Hg); or ≥ 30 mm Hg during exercise due to chronic pulmonary and/or cardiac disease or unknown reasons (idiopathic form)
- Cor pulmonale: altered structure (hypertrophy, dilation) or impaired function of the right ventricle caused by pulmonary hypertension resulting from a primary disorder of the respiratory or pulmonary artery system
Classification of pulmonary hypertension (WHO) by cause
- Group 1: Pulmonary arterial hypertension (PAH)
- Group 2: Left heart disease (e.g. ,
Group 3: Chronic lung diseases and/or hypoxemia
- Group 4: Chronic thromboembolic occlusion of the pulmonary vessels ; patients at high-risk for
- Group 5: Unclear multifactorial mechanisms
Chronic pulmonary and cardiac diseases can lead to pulmonary hypertension!
Chronic form: diseases of the airway, pulmonary vasculature, and chest wall
- Idiopathic pulmonary arterial hypertension
- Life-threatening acute form is almost always due to acute massive .
Increased pulmonary vascular resistance
- Occlusive vasculopathy; (idiopathic pulmonary arterial hypertension (IPAH) , )
- Perivascular parenchymal changes (e.g., , )
- Hypoxic pulmonary vasoconstriction (e.g., , )
- Inflammation (e.g., ) → increased inflammatory cell infiltration of intima → thickened endothelial wall
- PAH associated with endothelial dysfunction: ↑ endothelin → vasoconstriction 
Increased pulmonary venous pressure
- Volume or pressure overload from left-sided heart disease (e.g. )
- Increased pulmonary blood flow
- Often asymptomatic in early stages
- Dyspnea and/or syncope on exertion (due to an inadequate increase in cardiac output during exercise because of increased pulmonary vascular resistance)
- Chest pain
- Clinical features of underlying etiology
- Less common
- Physical examination
Clinical symptoms may be inconspicuous, especially, in early stages (the symptoms of underlying diseases such as COPD may eclipse those of PH)!
General diagnostic algorithm
- If clinical suspicion is high but echocardiography is not suggestive of PH with or without cor pulmonale → right heart catheterization
- If echocardiography is suggestive of pulmonary hypertension with or without cor pulmonale → further testing to find cause (classify the patient into a WHO PH category (group 1–5, see “Etiology”) → right heart catheterization to confirm diagnosis
- For the diagnosis of idiopathic pulmonary arterial hypertension (PAH) all other causes must be ruled out (e.g., heart or lung disease).
- Doppler echocardiography (best initial test)
- (confirmatory test)
- Electrocardiography: right axis deviation due to right ventricular hypertrophy
- Pronounced central pulmonary arteries
- Right heart hypertrophy; (prominent right heart border and loss of retrosternal space due to right ventricular enlargement in lateral view)
- Sudden change in diameter between central and peripheral pulmonary arteries
- Vascular rarefaction in the peripheral lungs
- Signs of underlying cause (e.g., nodular opacities in , in )
- Additional tests to screen for underlying cause
Initial therapy should be directed at the underlying cause of PH or cor pulmonale. Patients with persistent pulmonary hypertension and cor pulmonale despite treatment of the underlying cause should be evaluated for pulmonary vasodilator therapy in a specialized center.
Treatment of the underlying cause
- Group 1 PH (idiopathic; or hereditary PH): pulmonary vasodilator therapy (see below )
- Group 2 PH (left heart disease): ; treatment of
- Group 3 PH (chronic lung disease and/or hypoxemia): Treatment of the underlying cause and supplemental oxygen
- Group 4 PH (chronic thromboembolic disease): anticoagulation and/or surgical thromboendarterectomy
- Group 5 PH: treatment of metabolic and systemic disease
- Additional treatment
- Patients who are refractory to medical treatment
- Patients with cardiogenic shock due to cor pulmonale: IV inotropic agents (e.g., ) and diuretics
In acute cor pulmonale: see treatment of “ ”
- Maintain adequate blood pressure (e.g., IV fluids, vasoconstrictors)
- Correct primary problem (e.g., anticoagulation, thrombolytic or surgical embolectomy in )
Therapy should be initiated early before irreversible changes in the pulmonary vessels occur!