From the Guidelines
Pulmonary hypertension (PH) can be broadly classified into two categories: precapillary (pulmonary arterial hypertension) and postcapillary (pulmonary venous hypertension) PH, with distinct hemodynamic characteristics and clinical implications.
Key Differences
- Precapillary PH is characterized by a mean pulmonary arterial pressure (mPAP) >20 mmHg, pulmonary arterial wedge pressure (PAWP) ≤15 mmHg, and pulmonary vascular resistance (PVR) >3 Wood units, typically seen in pulmonary arterial hypertension (PAH) 1.
- Postcapillary PH is characterized by an mPAP >20 mmHg, PAWP >15 mmHg, and PVR <3 Wood units, often associated with left heart disease 1.
Clinical Classification
The clinical classification of PH has been updated to include five groups:
- Group 1: PAH
- Group 2: PH due to left heart disease
- Group 3: PH due to lung diseases and/or hypoxia
- Group 4: Chronic thromboembolic PH
- Group 5: PH with unclear and/or multifactorial mechanisms 1
Diagnostic Criteria
The diagnosis of PH is based on hemodynamic measurements, including mPAP, PAWP, and PVR, which can be assessed through right heart catheterization 1.
Clinical Implications
Understanding the differences between precapillary and postcapillary PH is crucial for accurate diagnosis, treatment, and management of patients with PH, as it can significantly impact their prognosis and quality of life 1.
From the Research
Difference between Precapillary and Postcapillary Pulmonary Hypertension
The main difference between precapillary (pulmonary arterial hypertension) and postcapillary (pulmonary venous hypertension) pulmonary hypertension lies in their underlying causes and hemodynamic characteristics.
- Precapillary pulmonary hypertension is characterized by elevated pulmonary artery pressure with a normal pulmonary capillary wedge pressure, typically seen in idiopathic pulmonary arterial hypertension (IPAH) 2.
- Postcapillary pulmonary hypertension, on the other hand, is associated with elevated pulmonary capillary wedge pressure, often resulting from left heart disease, such as heart failure with preserved ejection fraction (HFpEF) 3.
Hemodynamic Characteristics
Key hemodynamic differences between precapillary and postcapillary pulmonary hypertension include:
- Mean pulmonary artery pressure: similar in both conditions, but with distinct underlying pathophysiology 2.
- Pulmonary capillary wedge pressure: elevated in postcapillary pulmonary hypertension, indicating left heart disease 4.
- Cardiac index: comparable among groups, but with varying responses to targeted therapies 2.
Diagnostic Approaches
Diagnosing and differentiating between precapillary and postcapillary pulmonary hypertension require a combination of:
- Echocardiography: to assess left heart conditions and pulmonary artery pressure 5.
- Right heart catheterization: to directly measure pulmonary artery pressure and pulmonary capillary wedge pressure, providing a definitive diagnosis 4.
- Clinical assessment: to identify risk factors and comorbidities associated with left heart disease or pulmonary arterial hypertension 2, 6.
Treatment Implications
Understanding the difference between precapillary and postcapillary pulmonary hypertension has significant implications for treatment:
- Targeted therapies, such as phosphodiesterase type 5 inhibitors, may be effective in patients with a predominant pre-capillary component 6.
- Patients with postcapillary pulmonary hypertension may require treatment focused on underlying left heart disease, with careful consideration of the potential for combined pre- and post-capillary pulmonary hypertension 3, 6.