From the Guidelines
Pulmonary hypertension is caused by multiple factors, including left heart disease, lung diseases, chronic blood clots, congenital heart defects, sleep apnea, and autoimmune disorders, as well as idiopathic or hereditary causes, with the most recent classification simplifying into five groups: PAH, PH due to left heart disease, PH due to lung diseases and/or hypoxia, PH due to PA obstructions, and PH with unclear and/or multifactorial mechanisms 1. The main causes of pulmonary hypertension can be broken down into several categories, including:
- Left heart disease, such as mitral valve disease or left heart failure
- Lung diseases, like COPD or pulmonary fibrosis
- Chronic blood clots in the lungs
- Congenital heart defects
- Sleep apnea
- Certain autoimmune disorders, such as scleroderma
- Idiopathic or hereditary causes, including genetic mutations The underlying mechanism involves narrowing of pulmonary blood vessels through various pathways, including:
- Vasoconstriction
- Vascular remodeling with smooth muscle proliferation
- Inflammation
- Thrombosis This narrowing increases resistance to blood flow, forcing the right ventricle to work harder to pump blood through the lungs, eventually leading to right heart failure if left untreated. Risk factors for pulmonary hypertension include:
- Family history
- Other medical conditions, such as liver disease or HIV infection
- Living at high altitudes
- Female gender, as women are more commonly affected than men According to the most recent clinical classification, pulmonary hypertension can be divided into five groups:
- PAH
- PH due to left heart disease
- PH due to lung diseases and/or hypoxia
- PH due to PA obstructions
- PH with unclear and/or multifactorial mechanisms 1. It is essential to note that the diagnosis of pulmonary hypertension remains challenging due to its nonspecific symptoms and the diverse group of diseases that can cause it, emphasizing the importance of a careful history evaluation and risk factor assessment 1.
From the Research
Causes of Pulmonary Hypertension
The causes of pulmonary hypertension (PH) can be complex and varied. Some of the main causes include:
- Left heart disease 2, 3, 4
- Lung disease 2, 3, 4
- Chronic pulmonary thromboembolism 2, 3, 4
- Genetic factors, particularly in rare forms of pulmonary arterial hypertension (PAH) and PAH associated with congenital heart defects 5
- Unclear and/or multifactorial mechanisms 3, 4
Classification of Pulmonary Hypertension
Pulmonary hypertension can be classified into five main groups:
- Group 1: Pulmonary arterial hypertension (rare) 3, 4
- Group 2: Pulmonary hypertension associated with left-sided heart disease (very common) 3, 4
- Group 3: Pulmonary hypertension associated with lung disease (common) 3, 4
- Group 4: Pulmonary hypertension associated with pulmonary artery obstructions, usually related to thromboembolic disease (rare) 3, 4
- Group 5: Pulmonary hypertension with unclear and/or multifactorial mechanisms (rare) 3, 4
Underlying Mechanisms
The underlying mechanisms of pulmonary hypertension involve adverse vascular remodelling with obstruction, stiffening, and vasoconstriction of the pulmonary vasculature 3. This can lead to hypertrophy and ultimately failure of the right ventricle, which is the main cause of death in patients with pulmonary hypertension 3.