When is right‑heart catheterization indicated for diagnosing and managing pulmonary hypertension, and how does it guide hemodynamic classification, vasoreactivity testing, and therapy selection?

Role of Right Heart Catheterization in Pulmonary Hypertension

Right heart catheterization (RHC) is mandatory to confirm the diagnosis of pulmonary hypertension, establish hemodynamic classification, determine disease severity, and guide all treatment decisions—it must be performed before initiating any PAH-specific therapy. 1, 2, 3

When RHC is Required

Diagnostic Confirmation

• RHC is the gold standard and is required in every patient with suspected PH to confirm the diagnosis before treatment initiation, as echocardiography alone is insufficient and may be inaccurate in individual patients. 1, 3
• The procedure must be performed at expert centers due to technical complexity and potential for serious complications (morbidity 1.1%, mortality 0.055%). 1, 2, 3
• RHC is mandatory even when echocardiography shows high probability of PH, as Doppler-derived estimates can significantly underestimate or overestimate actual pressures. 3

Specific Clinical Scenarios Requiring RHC

• Group 1 PAH (pulmonary arterial hypertension): RHC is absolutely required before starting any PAH-specific medications to confirm precapillary hemodynamics. 2, 3
• Group 4 CTEPH (chronic thromboembolic PH): RHC is mandatory to assess surgical candidacy for pulmonary thromboendarterectomy and measure pulmonary vascular resistance. 2
• Congenital cardiac shunts: RHC is necessary to assess shunt hemodynamics and pulmonary vascular resistance before surgical correction decisions. 2
• Groups 2 and 3 PH (left heart disease or lung disease): RHC is required when organ transplantation is being considered. 2
• Heart failure with unclear hemodynamics: RHC is indicated when symptoms persist despite empiric therapy and clinical assessment cannot determine fluid status, perfusion adequacy, or vascular resistance. 2

Hemodynamic Classification Through RHC

Diagnostic Definitions

• Pulmonary hypertension is defined as mean PAP ≥25 mmHg at rest (though newer definitions use >20 mmHg). 3
• Pulmonary arterial hypertension requires all three criteria: mean PAP ≥25 mmHg, PAWP ≤15 mmHg, and PVR ≥3 Wood units. 2, 3

Classification by Hemodynamic Profile

• Precapillary PH (Groups 1,3,4,5): mean PAP ≥25 mmHg, PAWP ≤15 mmHg, PVR >3 Wood units—this distinguishes pulmonary vascular disease from left heart disease. 3
• Isolated postcapillary PH (Group 2): mean PAP ≥25 mmHg, PAWP >15 mmHg, transpulmonary gradient ≤12 mmHg—indicates left heart disease as primary cause. 3
• Combined pre- and postcapillary PH (Group 2): mean PAP ≥25 mmHg, PAWP >15 mmHg, transpulmonary gradient >12 mmHg—indicates "reactive" or out-of-proportion component. 3

Critical Measurements Obtained

• Mean pulmonary artery pressure confirms PH diagnosis and severity. 1, 3
• Pulmonary artery wedge pressure distinguishes precapillary from postcapillary PH and excludes left heart disease. 1, 3
• Cardiac output/cardiac index via thermodilution provides accurate flow measurements and allows PVR calculation. 1, 3
• Right atrial pressure assesses right heart dysfunction and predicts prognosis. 1
• Mixed venous oxygen saturation from multiple sites detects intracardiac shunts. 3

Vasoreactivity Testing During RHC

When to Perform Vasoreactivity Testing

• Vasoreactivity testing is indicated ONLY in patients with idiopathic PAH, heritable PAH, or drug-induced PAH—it should never be performed in other PH groups. 1, 2
• Testing must be performed only at expert centers by physicians experienced in pulmonary vascular disease management. 1, 2

Testing Protocol

• Nitric oxide is the recommended agent for vasoreactivity testing. 2
• Alternative agents include IV epoprostenol or adenosine. 1
• A positive response is defined as: reduction in mean PAP ≥10 mmHg to reach absolute value ≤40 mmHg with increased or unchanged cardiac output. 1, 2

Clinical Implications

• Only patients demonstrating positive acute vasoreactivity should be considered for high-dose calcium channel blocker therapy—this represents approximately 10% of idiopathic PAH patients. 1, 2
• Never use calcium channel blockers empirically without documented vasoreactivity, as this can be harmful in non-responders. 1, 4

How RHC Guides Therapy Selection

Treatment Initiation Decisions

• RHC hemodynamics determine eligibility for specific PAH therapies: endothelin receptor antagonists, prostacyclin analogs, or phosphodiesterase-5 inhibitors based on functional class and hemodynamic severity. 1
• Patients in functional class III who are not vasoreactive or who failed calcium channel blockers are candidates for advanced PAH therapies. 1

Surgical Candidacy Assessment

• Patients with suspected CTEPH should be referred to experienced centers for pulmonary thromboendarterectomy consideration based on RHC hemodynamics showing precapillary PH with organized thrombi. 1
• Patients with NYHA class III-IV symptoms should be referred for lung or heart-lung transplantation evaluation, with bilateral lung transplant being the procedure of choice. 1

Prognostic Risk Stratification

• Higher mean PAP, higher right atrial pressure, and lower cardiac index independently predict reduced survival in the NIH Registry cohort. 1, 3
• These hemodynamic parameters form the basis of survival prediction models that guide treatment intensity. 1

Technical Requirements and Pitfalls

Procedural Standards

• Zero the external pressure transducer at the mid-thoracic line (midway between anterior sternum and bed surface) in supine position to approximate left atrial level. 3
• Record pressures at end-expiration without breath-holding; average over several respiratory cycles. 3
• Verify PAWP position by confirming wedge-position blood sample oxygen saturation matches systemic arterial saturation. 3
• Use high-fidelity pressure tracings that can be printed for detailed waveform analysis to detect artifacts. 3

Common Pitfalls to Avoid

• Never perform RHC outside expert centers for PH evaluation—inexperienced operators have significantly higher complication rates. 2
• Do not rely on a single pressure measurement—spontaneous variability in PAP can reach ±20 mmHg even without intervention, with mean coefficient of variation 8%. 1, 3
• Avoid repeated balloon inflations in distal pulmonary arteries to reduce risk of vessel rupture. 3
• Do not misinterpret PAWP in patients with left heart disease risk factors—maintain low threshold for adding left heart catheterization to directly measure left ventricular end-diastolic pressure. 3

Measurement Limitations

• RHC measurements reflect only resting, supine conditions and may not represent hemodynamic responses during upright posture, activity, or sleep. 1
• Despite these limitations, RHC remains the necessary gold standard for diagnosis and treatment guidance. 1

Additional Diagnostic Value Beyond Hemodynamics

• RHC excludes alternative diagnoses such as intracardiac shunts, extracardiac shunts, and unsuspected left heart disease that may not be apparent on echocardiography. 1
• Shunt detection through sequential oxygen saturation measurements from superior vena cava, inferior vena cava, right atrium, right ventricle, and pulmonary artery identifies congenital heart disease. 3
• Assessment of right heart decompensation through elevated right atrial pressure combined with reduced cardiac output identifies patients requiring urgent intervention. 3