Right Heart Catheterization — Haemodynamic Interpretation
Definition
Interpretation is the assignment of measured pressures and flows to a diagnostic category, and it turns on two boundaries: the wedge pressure that separates pre- from post-capillary physiology, and the output that separates compensation from shock. Both boundaries move with posture, volume state and exertion, which is why a resting measurement at the margin is often the least informative number the laboratory produces.
Key Concepts
PAWP Thresholds and the Grey Zone
- The physiological upper limit of normal is 13 mmHg. A meta-analysis of 940 healthy subjects put it there, with no dependence on body mass index or age and a slightly higher value in women. (sources/rhc-hf-ehj-2025, rating: high)
- The threshold has drifted historically: 10–11 mmHg in the 1973 WHO definition, raised to 15 mmHg with the pulmonary arterial hypertension trials of the 1990s, and 15 mmHg is the current threshold for post-capillary physiology. (sources/rhc-hf-ehj-2025)
- That leaves a 13–15 mmHg grey zone in which a raised but not yet diagnostic wedge pressure is the commonest way early left heart disease is missed. (sources/rhc-hf-ehj-2025)
- The classification follows from this grid, once the entry criterion is met. Pulmonary hypertension itself is a mean pulmonary artery pressure above 20 mmHg at rest; only then do the wedge and resistance values separate the categories. Pre-capillary is wedge ≤15 mmHg with resistance >2 WU; isolated post-capillary is wedge >15 with resistance ≤2 WU; combined pre- and post-capillary is wedge >15 with resistance >2 WU. A fourth pattern — raised pressure with a wedge of 15 or less and a resistance of 2 WU or less — is unclassified, and usually reflects high pulmonary blood flow, as in congenital heart disease, liver disease or hyperthyroidism. The clinical groups built on this grid are on concepts/Pulmonary-Hypertension. (sources/rhc-hf-ehj-2025; sources/PHT-ESC-2022, rating: very high)
The 12–18 mmHg Zone of Uncertainty
- A wedge pressure between roughly 12 and 18 mmHg should be contextualised against the individual probability of left heart disease rather than treated as decisive. (sources/rhc-hf-ehj-2025, rating: high)
- Provocative testing is the answer in this zone, because latent heart failure with preserved ejection fraction is exactly the diagnosis that hides there. (sources/rhc-hf-ehj-2025)
Volume Challenge and Passive Leg Raise
- Protocol: 7–10 mL/kg of 0.9% saline — about 500 mL — at ≥100 mL/min, or a passive leg raise to about 45° or feet on pedals. Measure 20 seconds to 3 minutes after completing the manoeuvre. (sources/hemodynamic-hf-pht-aha-2026, rating: very high)
- Expected normal response: right atrial pressure rises by 5 mmHg, wedge pressure by 6, mean pulmonary artery pressure by 7–8, and output by 1.5–2 L/min through stroke volume rather than heart rate. Elderly patients, particularly older women, respond more steeply. (sources/hemodynamic-hf-pht-aha-2026)
- A wedge pressure ≥19 mmHg after fluid bolus or leg raise identifies occult post-capillary physiology with a high positive predictive value — single-centre data awaiting multicentre validation, and updated from the earlier ≥18 mmHg threshold. A leg-raise wedge of ≤11 mmHg rules post-capillary physiology out. (sources/hemodynamic-hf-pht-aha-2026)
- Intermediate results dominate. A large proportion of patients land back in the 12–18 mmHg range, which limits the test's usefulness in exactly the population it was designed for; the result has to be read against phenotype and imaging. (sources/hemodynamic-hf-pht-aha-2026)
Exercise Testing and the HFpEF Criteria
Exercise catheterisation provides four criteria, at least one of which must be met: a resting wedge pressure ≥15 mmHg; a wedge ≥20 mmHg after fluid bolus or passive leg raise; a peak exercise wedge ≥25 mmHg supine or ≥20 mmHg upright; or a wedge-to-output slope above 2 mmHg·L·min regardless of position. (sources/hemodynamic-hf-pht-aha-2026, rating: very high)
- Exercise-induced pulmonary hypertension is a mean pulmonary artery pressure to output slope above 3 mmHg·L·min. It predicts outcome independently of resting haemodynamics, and can unmask a post-capillary component in a patient presumed to have pre-capillary disease. (sources/hemodynamic-hf-pht-aha-2026)
- Supine and upright testing answer different questions. Supine gives higher venous return and stable, reproducible measurements and is the posture used in the dapagliflozin work; upright reproduces daily activity, reaches higher workloads and allows more repeated measurements. The wedge-to-output slope, rather than the absolute wedge pressure, discriminates in both. (sources/hemodynamic-hf-pht-aha-2026)
Exercise Phenotypes
- Chronotropic incompetence: heart rate reserve below 0.80, or below 0.62 on beta-blockers, where reserve is the achieved rise in heart rate divided by the predicted rise, and predicted peak rate is 220 minus age. (sources/hemodynamic-hf-pht-aha-2026, rating: very high)
- Preload insufficiency: peak oxygen consumption below 80% of predicted, peak output below 80% of predicted, and a rise in wedge pressure below 7 mmHg during exercise — the patient cannot deliver volume, rather than failing to handle it. (sources/hemodynamic-hf-pht-aha-2026)
- Wedge pressure indexed to workload above roughly 25–35 mmHg·W·kg marks higher mortality in both reduced and preserved ejection fraction. (sources/hemodynamic-hf-pht-aha-2026)
- Right ventricular–pulmonary artery coupling can be measured directly with a conductance catheter at rest, where a raised pressure-to-output slope identifies early pre-capillary disease, and estimated non-invasively from the tricuspid annular plane excursion to systolic pressure ratio. See concepts/RV-PA-Coupling. (sources/rhc-hf-ehj-2025, rating: high)
Advanced Metrics
- Cardiac power output reflects ventricular function, and reincorporating right atrial pressure into the calculation improves its prognostic value in decompensated heart failure and cardiogenic shock relative to the older formula. (sources/hemodynamic-hf-pht-aha-2026, rating: very high)
- The aortic pulsatility index captures left ventricular ejection efficiency and ventriculoarterial coupling, and predicts myocardial recovery and the ability to wean mechanical support; its principal components are pulse pressure and wedge pressure. (sources/hemodynamic-hf-pht-aha-2026)
- The pulmonary artery pulsatility index identifies severe right ventricular dysfunction in acute infarction and predicts right ventricular failure after LVAD implantation. Its values are population-specific and not interchangeable — see concepts/Pulmonary-Artery-Pulsatility-Index. (sources/hemodynamic-hf-pht-aha-2026)
- Right ventricular stroke work index measures beat-to-beat right ventricular workload and is prognostic in heart-failure cardiogenic shock and after LVAD implantation. (sources/hemodynamic-hf-pht-aha-2026)
- The myocardial performance score combines the aortic pulsatility index and cardiac power output to reflect ventricular power efficiency, and correlates with ventriculoarterial coupling and energetic state. (sources/hemodynamic-hf-pht-aha-2026)
- Pulmonary arterial capacitance — stroke volume divided by pulmonary pulse pressure — carries prognostic value in idiopathic pulmonary arterial hypertension and should be measured at the index catheterisation. It falls early in pulmonary vascular disease and may identify risk before resistance rises; values at or above 3.0 mL/mmHg are associated with better survival. (sources/hemodynamics-circ-2012, rating: high; sources/rhc-hf-ehj-2025)
Vasodilator Challenge and Vasoreactivity Testing
Two tests use the same drugs for opposite purposes, and they are routinely conflated.
| Vasodilator challenge before transplantation | Acute vasoreactivity testing in PAH | |
|---|---|---|
| Indication | sPAP ≥50 mmHg with TPG ≥15 mmHg or PVR ≥3 WU; also when TPG or PVR is elevated with a low output even if sPAP is <50 | Idiopathic, heritable or drug-induced PAH with mPAP >20 and wedge <15 mmHg |
| Positive response | TPG ≤12–15 mmHg, PVR ≤2.5–3 WU and systolic pressure >85 mmHg | mPAP fall ≥10 mmHg to an absolute value ≤40 mmHg with maintained or increased output |
| Consequence | Listing permitted; failure leads to diuresis, temporary support and LVAD assessment | About 10% respond; responders enter the calcium channel blocker pathway |
(Vasodilator challenge: sources/rhc-hf-ehj-2025, rating: high; vasoreactivity: sources/hemodynamic-hf-pht-aha-2026, rating: very high)
- Sodium nitroprusside starts at 0.25–0.5 μg/kg/min, titrated by 0.5 μg/kg/min every 3–5 minutes to a maximum of 10 μg/kg/min, by pump through a light-protected bag. It lowers systemic resistance, which lowers left ventricular afterload and raises output — the pulmonary pressure then falls secondarily. Stop below a wedge of 12 mmHg; avoid if systolic pressure is under 85 mmHg. (sources/hemodynamic-hf-pht-aha-2026)
- Milrinone is given as a 25–50 μg/kg bolus over 5–10 minutes with reassessment at 5 minutes and no uptitration. It is preferred to nitroprusside when there is hypotension, low systemic resistance or a raised resistance driven by low output. It is the riskier drug in unstable tachyarrhythmia and in renal impairment below an eGFR of 30 mL/min. (sources/hemodynamic-hf-pht-aha-2026)
- Failure of the challenge is not the end of the pathway. If resistance is reversible but systolic pressure stays under 85 mmHg the risk of right ventricular failure after transplantation remains high; a failed challenge leads to hospitalisation, diuresis, temporary mechanical support and then durable LVAD. An LVAD can reverse pulmonary hypertension, and resistance that persists after 3–6 months of effective unloading is treated as irreversible and precludes transplantation. (sources/rhc-hf-ehj-2025)
- The vasoreactivity agents differ in route, dose and safety. Inhaled nitric oxide and inhaled iloprost and intravenous epoprostenol are Class I; adenosine is no longer recommended because of frequent side effects. (sources/hemodynamic-hf-pht-aha-2026)
| Agent | Starting dose | Maximum | Notes |
|---|---|---|---|
| Inhaled nitric oxide | 10–20 ppm | 40–80 ppm | Taper before stopping; avoid if the wedge pressure is elevated; Class I |
| Inhaled iloprost | 5–17 μg nebulised over 15 min | — | No contraindication to short-term testing; Class I |
| Intravenous epoprostenol | 2 ng/kg/min | 12 ng/kg/min | Contraindicated in pulmonary oedema; Class I |
| Adenosine | 50 μg/kg/min | ~350–500 μg/kg/min | No longer recommended (ESC 2022); contraindicated in AV block, asthma and pre-excited atrial fibrillation |
(sources/hemodynamic-hf-pht-aha-2026, rating: very high)
- Never give a vasodilator for testing when the wedge pressure is elevated. Nitric oxide dilates the post-capillary bed, raises left atrial filling pressure and can precipitate pulmonary oedema. (sources/hemodynamics-circ-2012, rating: high)
Contradictions / Open Questions
- The normal wedge pressure and the diagnostic threshold are different numbers. Physiology sets the upper limit of normal at 13 mmHg; guidelines set post-capillary physiology at above 15. Everything between them is a deliberate grey zone, and patients in it are under-recognised rather than misclassified. (sources/rhc-hf-ehj-2025, rating: high)
- The volume challenge threshold moved from 18 to 19 mmHg on one study. The earlier figure lacked long-term validation; the newer one has an excellent positive predictive value from a single centre and still awaits multicentre confirmation. Neither is established. (sources/hemodynamic-hf-pht-aha-2026, rating: very high; sources/rhc-hf-ehj-2025)
- Absolute wedge pressure and the wedge-to-output slope disagree in about a fifth of patients. Peak wedge ≥25 mmHg supine and a slope above 2 mmHg·L·min select different subgroups with different output profiles. The slope discriminates more consistently across studies and postures, but its threshold is not standardised. (sources/hemodynamic-hf-pht-aha-2026)
- Exercise phenotypes have not translated into effective therapy. Beta-blocker withdrawal improved peak oxygen consumption in chronotropic-incompetent HFpEF, atrial pacing did not, and ivabradine results are mixed — precise haemodynamic phenotyping has not yet produced treatments that work. (sources/hemodynamic-hf-pht-aha-2026)
- Advanced metrics are prognostic but not adopted. The pulmonary artery pulsatility index, cardiac power output and right ventricular stroke work index all predict outcome, yet none is integrated into European guidelines for cardiogenic shock staging. (sources/rhc-hf-ehj-2025, rating: high)
Connections
- Part of concepts/Right-Heart-Catheterization — the parent overview
- concepts/RHC-Technique-and-Measurement — how the numbers are obtained
- concepts/RHC-Clinical-Applications — the disease contexts
- concepts/Pulmonary-Hypertension — haemodynamic definitions and the PH classification
- entities/HFpEF — the diagnosis the exercise criteria were written for
- concepts/Pulmonary-Artery-Pulsatility-Index — the index in full
- concepts/RV-PA-Coupling — coupling measured and estimated
- concepts/PAH-Treatment — what a positive vasoreactivity test leads to
- concepts/Cardiac-Output-Measurement — the output that normalises every slope