Pulmonary hypertension

Pulmonary hypertension (PH) is defined as elevated blood pressure beyond 20 mmHg MAP in the pulmonary artery (physiological MAP is 10-20). It most commonly occurs as a consequence of heart disease or lung disease. Pulmonary arterial hypertension (PAH) is one form of pulmonary hypertension which is not secondary to heart or lung disease.

Pulmonary hypertension is relatively common, the prevalence being approximately 1%, mostly due to the high prevalence of COPD and heart disease. PH itself can lead to right-sided heart failure.

Etiology and types

We distinguish multiple different types according to the etiology and pathomechanism:

Group	Name	Frequency	Common causes	Pathomechanism
Group 1	Pulmonary arterial hypertension	Rare	Idiopathic Drugs Connective tissue disorder Persistent pulmonary hypertension of the newborn Eisenmenger syndrome	Elevated pulmonary vascular resistance
Group 2	Pulmonary hypertension secondary to left-sided heart disease	Very common (70% of PH)	Heart failure Valvular disease
Group 3	Pulmonary hypertension secondary to lung disease or hypoxaemia	Common	COPD Interstitial lung disease	Chronic hypoxia causes pulmonary vasoconstriction and remodelling of the pulmonary vascular bed
Group 4	Pulmonary hypertension secondary to pulmonary artery obstruction	Rare	Chronic pulmonary embolism	Pulmonary embolism increase pulmonary vascular resistance
Group 5	Pulmonary hypertension secondary to unknown or multifactorial causes	Rare	Chronic kidney disease Sarcoidosis Haematological disorder

Clinical features

Exertional dyspnoea is the main symptom. As the hypertension worsens, less and less exertion is required to elicit dyspnoea. Chest pain, cough, and haemoptysis are rare symptoms.

Cyanosis is often present.

Diagnosis and evaluation

Examination for underlying causes may include natriuretic peptide, spirometry, etc.

ECG may show certain unspecific signs, including sinus tachycardia, right axis deviation, P pulmonale, signs of right ventricular hypertrophy, or RBBB.

Neither chest radiography or CT are required in the evaluation, except for evaluation of underlying disorders. On x-ray, the central vessels may be more prominent than normal. On CT, one can see that the pulmonary artery is larger than the ascending aorta, and that there is a so-called centroperipheral caliber discrepancy  or “pruning” of the peripheral vessels, which means that the central pulmonary vessels are larger than normal while the peripheral vessels aren't.

Echocardiography is the main modality for the evaluation, as it can estimate the pulmonary artery pressure. Typical findings include tricuspid regurgitation, pulmonary regurgitation, dilated right atrium and ventricle, and right ventricular hypertrophy. However, right heart catheterisation is obligatory for the final diagnosis, as it can directly measure the pressure.

Management

Regardless of type and cause, hypoxaemia will worsen the condition and should be avoided.

Lung-protective lifestyle changes, including weight loss, smoking cessation, and avoidance of pollutants and microbes, is always indicated. If due to an underlying disease, this should be treated.

For pulmonary arterial hypertension, a calcium channel blocker, phosphodiesterase 5-inhibitor, prostanoid, endothelin receptor antagonist, or guanylate cyclate simulator may be used. For type 4, thrombendarterectomy with or without balloon dilatation of the pulmonary arteries may cure the condition. For all other types of PH, there is no specific treatment.