From the Guidelines
Right heart catheterization (RHC) in idiopathic pulmonary hypertension (IPH) typically reveals elevated pulmonary pressures with a mean pulmonary artery pressure (mPAP) >20 mmHg at rest, pulmonary vascular resistance (PVR) >3 Wood units, and pulmonary capillary wedge pressure (PCWP) ≤15 mmHg, as defined by the most recent guidelines 1. These findings confirm precapillary pulmonary hypertension while excluding left heart disease as the cause. Additional diagnostic findings include:
- Normal or reduced cardiac output
- Elevated right atrial pressure (>8-10 mmHg)
- Increased transpulmonary gradient (>12 mmHg) Vasoreactivity testing with agents like inhaled nitric oxide, intravenous epoprostenol, or adenosine is essential during RHC to identify the small subset of IPH patients who may respond to calcium channel blockers, as recommended by the guidelines 1. A positive vasoreactive response is defined as a decrease in mPAP by ≥10 mmHg to reach an absolute value ≤40 mmHg with increased or unchanged cardiac output. RHC is crucial not only for diagnosis but also for assessing disease severity, prognosis, and guiding therapeutic decisions in IPH management, as emphasized in the guidelines 1.
The diagnostic criteria for IPH have been updated to reflect a mean pulmonary artery pressure threshold of >20 mmHg, which is a recent reduction from >25 mmHg, as noted in the guidelines 1. However, the mean pulmonary artery pressure alone does not distinguish PAH from other forms of PH, and additional criteria such as pulmonary artery wedge pressure and pulmonary vascular resistance are necessary for diagnosis, as stated in the guidelines 1.
In clinical practice, RHC is a critical tool for diagnosing and managing IPH, and its findings should be interpreted in the context of the patient's overall clinical presentation and medical history, as recommended by the guidelines 1. By following the guidelines and using RHC to guide diagnosis and treatment, clinicians can improve outcomes and quality of life for patients with IPH.
From the Research
Diagnostic Findings on Right Heart Catheterization for Idiopathic Pulmonary Hypertension
The diagnostic findings on right heart catheterization (RHC) for idiopathic pulmonary hypertension (IPH) include:
- Mean pulmonary arterial pressure (mPAP) >20 mmHg 2
- Pulmonary arterial wedge pressure (PAWP) ≤15 mmHg 2, 3
- Pulmonary vascular resistance (PVR) >2 Wood Units (WU) 2 or >3 Wood units 3
- A reduction of 10 mmHg in mean pulmonary arterial pressure or achieving a mean pulmonary artery pressure of less than 40 mmHg, with no change or an increase in cardiac output, is considered a positive response to vasoreactivity testing 3
Hemodynamic Parameters
The following hemodynamic parameters are used to distinguish pre-capillary PH, isolated post-capillary PH, and combined post- and pre-capillary PH:
- Pre-capillary PH: PAWP ≤15 mmHg, PVR >2 WU 2
- Isolated post-capillary PH: PAWP >15 mmHg, PVR ≤2 WU 2
- Combined post- and pre-capillary PH: PAWP >15 mmHg, PVR >2 WU 2
Clinical Classification of PH
The clinical classification of PH includes five major groups, with IPH being a subgroup of pulmonary arterial hypertension (PAH) 2. The diagnosis of IPH is made through the exclusion of other disorders, including pulmonary, thromboembolic, left ventricular, and valvular heart disease 3.
Role of Pulmonary Capillary Wedge Pressure
Pulmonary capillary wedge pressure (PCWP) is a valuable tool for accurate diagnosis of PAH, with a PCWP ≤15 mmHg being a reliable indicator of normal left ventricular filling pressure in pre-capillary PH patients 4. However, PCWP measurements alone may not be sufficient to diagnose PAH, and simultaneous right- and left-side heart catheterizations may be necessary to accurately diagnose PH 4.