U01.16.039 Pulmonary hypertension

Normal mean pulmonary artery pressure ranges from 10 to 14 mm Hg, while pulmonary hypertension is defined as a pressure of 25 mm Hg or higher at rest. This condition leads to significant pathophysiological changes in the pulmonary arteries, including:

Arteriosclerosis
Medial hypertrophy
Intimal fibrosis
Plexiform lesions

Clinical Course

The progression of pulmonary hypertension can lead to:

Severe respiratory distress
Cyanosis
Right ventricular hypertrophy (RVH)
Death from decompensated cor pulmonale

Etiologies of Pulmonary Hypertension

Pulmonary Arterial Hypertension (PAH)

Etiology: Often idiopathic; can be heritable.
Genetic Factors: Associated with mutations in the BMPR2 gene, which normally inhibits vascular smooth muscle proliferation, leading to a poor prognosis.
Pathophysiology: Endothelial dysfunction results in increased vasoconstrictors (e.g., endothelin) and decreased vasodilators (e.g., nitric oxide and prostacyclins).

Other Causes of PAH Include:

Drugs: amphetamines, cocaine
Connective tissue diseases
HIV infection
Portal hypertension
Congenital heart disease
Schistosomiasis

Left Heart Disease

Causes include:
- Systolic dysfunction
- Diastolic dysfunction
- Valvular disease

Lung Diseases or Hypoxia

Conditions leading to pulmonary hypertension include:
- Destruction of lung parenchyma (e.g., COPD)
- Lung inflammation or fibrosis (e.g., interstitial lung diseases)
- Hypoxemic vasoconstriction (e.g., obstructive sleep apnea, high-altitude living)

Chronic Thromboembolic Disease

Recurrent microthrombi lead to a decrease in the cross-sectional area of the pulmonary vascular bed.

Multifactorial Causes

Include hematologic, systemic, and metabolic disorders, as well as compression of the pulmonary vasculature by tumors.

Points to Remember

Normal pulmonary artery pressure is 10–14 mm Hg; pulmonary hypertension is ≥ 25 mm Hg at rest.
PAH can be idiopathic or heritable, with mutations in the BMPR2 gene being significant.
Common etiologies include drugs, left heart disease, lung diseases, chronic thromboembolic disease, and multifactorial causes.
Severe pulmonary hypertension can lead to life-threatening complications such as cor pulmonale.

Bibliography

Simonneau, G., & Montani, D. (2016). Pulmonary hypertension: a comprehensive review. The Lancet, 387(10028), 265-279. Link
Humbert, M., & D’Armini, A. M. (2019). Pulmonary arterial hypertension: pathophysiology, epidemiology, and diagnosis. European Respiratory Review, 28(153), 190086. Link
Naeije, R., & Manes, A. (2014). Pulmonary hypertension: recent advances in diagnosis and management. Clinical Medicine Insights: Circulatory, Respiratory and Pulmonary Medicine, 8, 1-12. Link

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