Overview of the REVEAL 2.0 Risk Score

The REVEAL Registry Risk Score 2.0 (Registry to EValuate Early And Long-term pulmonary arterial hypertension disease management, version 2.0) is a validated, multivariable prognostic calculator designed to predict 1-year all-cause mortality in patients with WHO Group 1 pulmonary arterial hypertension (PAH). It integrates 13 variables spanning patient demographics, PAH etiology, functional status, vital signs, biomarkers, echocardiographic findings, pulmonary function, and invasive hemodynamics into a single composite score that begins at a base of 6 points, with individual variables adding or subtracting points based on their independent contribution to mortality risk.

The score stratifies patients into three risk tiers: low risk (score 0-6, 1-year mortality ≤2-5%), intermediate risk (score 7-8, 1-year mortality 5-10%), and high risk (score ≥9, 1-year mortality >10%). These tiers align conceptually with the low/intermediate/high risk framework endorsed by the 2022 ESC/ERS Guidelines for pulmonary hypertension, providing a numerically grounded complement to guideline-based risk assessment strategies.

Published by Benza et al. in Chest (2019), REVEAL 2.0 updated the original REVEAL risk calculator with refined variable weights, an updated BNP/NT-proBNP stratification schema, and the addition of all-cause hospitalization within the preceding 6 months as a new predictor variable. These updates improved the score's discriminative ability compared to the original REVEAL tool and demonstrated comparable or superior performance to ESC/ERS-based risk stratification strategies in independent external validation cohorts.

Background: Pulmonary Arterial Hypertension and the Need for Risk Stratification

Pulmonary arterial hypertension is a progressive, life-threatening disease of the pulmonary vasculature characterized by sustained elevation in pulmonary artery pressure (mean PAP ≥20 mmHg with pulmonary vascular resistance ≥2 Wood units in the absence of left heart disease or lung disease), leading to progressive right ventricular dysfunction, exercise intolerance, and ultimately right heart failure and death. Despite advances in targeted therapy over the past three decades, PAH remains a disease of high morbidity and significant mortality, with median survival from diagnosis historically measured in years.

The pathophysiology of PAH involves concentric medial hypertrophy, intimal proliferation, adventitial remodeling, and in situ thrombosis within the distal pulmonary arterioles, driven by a complex interplay of vasoconstriction, inflammation, and abnormal cellular proliferation in genetically susceptible or disease-exposed individuals. Three major signaling pathways are disrupted in PAH and form the targets of current pharmacotherapy: the endothelin-1 axis, the nitric oxide/cGMP axis, and the prostacyclin/cAMP axis.

PAH encompasses a heterogeneous group of conditions under the WHO Group 1 classification: idiopathic PAH (IPAH), heritable PAH (with pathogenic variants in BMPR2, ACVRL1, ENG, and other genes), drug- and toxin-induced PAH, connective tissue disease-associated PAH (CTD-PAH), HIV-associated PAH, congenital heart disease-associated PAH, and portopulmonary hypertension (PoPH). These subtypes share similar hemodynamic definitions and often similar treatment targets but differ substantially in their natural history, prognosis, and response to therapy.

The fundamental objective of PAH risk stratification is to match treatment intensity to disease severity at diagnosis and at each follow-up assessment. The overarching treatment goal in contemporary PAH management is attainment and maintenance of low-risk status. Patients who present at or achieve low risk on initial or sequential therapy have substantially better long-term outcomes than those who remain in intermediate or high-risk categories. Conversely, patients who fail to achieve low-risk status on initial therapy warrant prompt treatment escalation, and those at high risk require urgent consideration of lung transplantation referral and maximal combination therapy.

Before the development of validated composite risk scores, clinicians relied on individual clinical parameters (functional class, 6MWD, hemodynamics) to estimate prognosis. While individually informative, these parameters do not account for the multidimensional nature of PAH risk, where a patient may have excellent functional capacity but severely elevated biomarkers, or preserved hemodynamics but markedly impaired exercise tolerance. Composite risk scores that mathematically integrate multiple domains overcome this limitation, providing a single numeric estimate that captures the aggregate mortality burden from all measured parameters simultaneously.

From REVEAL to REVEAL 2.0: The Evolution of the Score

The original REVEAL risk score, published by Benza et al. in 2010, was the first validated composite risk score for PAH derived from a large, prospective, multi-centre US registry. It was developed from 2,716 patients with WHO Group 1 PAH enrolled at 54 sites between March 2006 and September 2009 and demonstrated robust discrimination for 1-year survival. However, the original REVEAL score had several recognized limitations: some variable thresholds were imprecisely calibrated relative to observed survival curves, the BNP variable used a single dichotomous cutoff that did not fully capture the prognostic gradient across the biomarker range, and it predated the routine use of NT-proBNP as a registry variable in many centres.

REVEAL 2.0, published in 2019, addressed these limitations through a systematic re-derivation using updated data from 2,529 patients with baseline right heart catheterization data in the REVEAL registry, with follow-up extended to September 2012. Key refinements in REVEAL 2.0 included:

• Updated variable weights: Regression coefficients for existing variables were recalculated in the updated cohort, yielding revised integer point assignments that more accurately reflect their independent contributions to 1-year mortality.
• Four-tier BNP stratification: The original dichotomous BNP cutoff was replaced with four ordered BNP categories (<50, 50-199, 200-799, ≥800 pg/mL) with graded point values (-2, 0, +1, +2), capturing the dose-response relationship between BNP elevation and mortality.
• NT-proBNP as an alternative biomarker: REVEAL 2.0 formally incorporated NT-proBNP (<300, 300-1,099, ≥1,100 pg/mL; -2, 0, +2 points respectively) as an alternative to BNP, reflecting widespread adoption of NT-proBNP measurement in clinical practice.
• Addition of hospitalization variable: All-cause hospitalization within the preceding 6 months (+1 point) was identified as a new independent predictor and added to the score, capturing the clinical significance of decompensation events as markers of disease trajectory.
• Refined 6MWD tiers: The four-tier 6MWD stratification (≥440m, 320-440m, 165-319m, <165m; -2, -1, 0, +1) replaced the original scheme, providing finer gradation across the functional capacity spectrum.
• Retained protective variables: PVR <5 Wood units (-1 point) and 6MWD ≥440m (-2 points) were retained as negatively scoring variables, formally acknowledging that favorable values of these parameters are independently associated with better survival.

In head-to-head comparison within the REVEAL registry and in external validation cohorts, REVEAL 2.0 demonstrated improved c-statistics compared to the original REVEAL score (AUC approximately 0.73-0.76 vs. 0.71-0.73) and comparable performance to the ESC/ERS 2015 guideline-based risk stratification approach (which uses a simplified three-variable low-risk criteria assessment).

Score Variables: Components and Clinical Rationale

The REVEAL 2.0 score starts at a base of 6 points, with each variable adding or subtracting points. The final score is the algebraic sum of the base and all applicable variable points. The 13 variables span six clinical domains.

Domain 1: Etiology (WHO Group 1 Subgroup)

PAH etiology is a fundamental determinant of long-term prognosis, and REVEAL 2.0 assigns differential point values across the four major etiologic subgroups:

Subgroup	Points	Clinical Rationale
Idiopathic PAH and other (reference)	0	Reference category; intermediate prognosis across the PAH spectrum
CTD-PAH (connective tissue disease)	+1	Particularly SSc-PAH has worse outcomes due to comorbid interstitial lung disease, cardiac involvement, and vasculopathy
Heritable PAH	+2	BMPR2 and other pathogenic variants associate with younger age at onset but more aggressive pulmonary vascular disease and poor treatment response
Portopulmonary hypertension (PoPH)	+3	Hepatic comorbidity (portal hypertension, cirrhosis) creates compounding right ventricular and hepatic venous pressure interactions; transplant options constrained

CTD-PAH, particularly systemic sclerosis-associated PAH (SSc-PAH), warrants specific emphasis. SSc-PAH accounts for approximately 15-20% of incident PAH diagnoses in Western registries and has historically carried among the worst prognoses of any PAH subgroup. Factors contributing to its poor outcomes include the coexistence of interstitial lung disease, cardiac fibrosis, esophageal dysmotility impairing nutrition and medication absorption, renal crisis risk, and the limited vasodilatory response to PAH-targeted therapies compared to IPAH.

Heritable PAH, predominantly caused by loss-of-function mutations in BMPR2 (bone morphogenetic protein receptor type 2), is associated with an earlier age of onset, lower diffusing capacity, and often more aggressive progression, though younger age paradoxically confers some prognostic advantage. Approximately 70-80% of familial PAH and 10-25% of apparently idiopathic PAH harbor BMPR2 mutations.

Portopulmonary hypertension is the most severely penalized etiology in REVEAL 2.0 (+3 points). PoPH develops in 2-6% of patients with portal hypertension and creates a complex interaction between elevated portal pressure, increased pulmonary blood flow, and pulmonary vascular remodeling. Liver transplantation (which might otherwise treat the underlying portal hypertension) is typically contraindicated when mean PAP exceeds 45-50 mmHg or PVR exceeds 3 Wood units, creating a narrow therapeutic window. PAH-targeted therapy can sometimes lower PAH severity sufficiently to allow transplantation, but the dual-organ comorbidity substantially reduces overall prognosis.

Domain 2: Demographics

Male Sex, Age >60 Years (+2 points)

The composite demographic variable of male sex combined with age above 60 years carries +2 points, reflecting the consistent observation across multiple PAH registries that older male patients have substantially worse outcomes than younger patients and female patients of equivalent age. This sex-age interaction has been among the most reproducible findings in PAH epidemiology.

The sex-based prognosis paradox in PAH is well-recognized: while PAH preferentially affects women (female-to-male ratio approximately 2.3:1 in most registries), male patients with PAH have consistently worse survival. Proposed mechanisms include differences in estrogen-mediated pulmonary vascular protection, greater prevalence of comorbid coronary artery disease and diastolic dysfunction in older males, different right ventricular adaptive responses between sexes (females tend to maintain RV function longer through adaptive hypertrophy, while males are more prone to RV failure), and differences in BMPR2 penetrance and expression between sexes.

Above age 60, both sexes experience worsening prognosis due to accumulated cardiovascular comorbidities, reduced physiologic reserve, and increasing likelihood of non-PAH contributors to pulmonary hypertension that may be misclassified as Group 1. The REVEAL 2.0 composite variable intentionally combines sex and age because their interaction was stronger than their individual additive effects in the derivation analysis.

Domain 3: Renal Function

eGFR <60 mL/min/1.73 m² (+1 point)

Reduced estimated glomerular filtration rate below 60 mL/min/1.73 m² (corresponding to CKD Stage 3 or worse) adds 1 point to the REVEAL 2.0 score. Renal impairment in PAH patients signals multi-organ involvement and predicts worse outcomes through several mechanisms.

Cardiorenal interactions are prominent in advanced PAH: elevated right atrial pressure causes venous congestion and elevated renal venous pressure, impeding glomerular filtration through a hemodynamic mechanism distinct from left heart failure. Reduced cardiac output further contributes to renal hypoperfusion. Conversely, pre-existing CKD reduces the physiologic resilience needed to withstand the hemodynamic perturbations of PAH and limits the therapeutic options available (e.g., phosphodiesterase-5 inhibitor dosing requires adjustment in severe renal impairment, and some prostacyclin formulations have altered pharmacokinetics in renal failure).

The eGFR threshold of 60 mL/min/1.73 m² was selected based on the survival curve inflection point in the REVEAL derivation data and corresponds to the clinically recognized CKD Stage 3a threshold, above which excess cardiovascular mortality risk is consistently demonstrated in the general population.

Domain 4: Functional Status

NYHA/WHO Functional Class (FC I=-1, FC II=0, FC III=+1, FC IV=+2)

The WHO/NYHA functional classification of exercise limitation is one of the oldest and most consistently validated predictors of PAH outcomes. First adapted to pulmonary hypertension from the original NYHA heart failure classification, WHO FC describes the relationship between physical activity and symptoms:

Class	Description	REVEAL 2.0 Points
I	No limitation of physical activity; ordinary activity does not cause symptoms	-1 (protective)
II	Slight limitation; comfortable at rest, but ordinary physical activity causes symptoms	0 (reference)
III	Marked limitation; comfortable at rest, but less than ordinary activity causes symptoms	+1
IV	Unable to carry out any activity without symptoms; symptoms may be present at rest	+2

WHO FC I is intentionally assigned a negative score (-1 point) in REVEAL 2.0, reflecting the observation that WHO FC I patients have measurably better 1-year survival than FC II patients, not merely equivalent survival. This protective adjustment was formalized in REVEAL 2.0 based on observed survival differences in the registry that were larger than the original score captured.

WHO FC IV represents a medical urgency in PAH. Patients presenting in or progressing to FC IV have 1-year mortality rates exceeding 50% in most registry analyses and require urgent initiation of parenteral prostacyclin therapy, hospitalization for hemodynamic optimization, and early listing for lung transplantation if not already underway. The 2-point increment for FC IV reflects this dramatically elevated mortality risk.

WHO functional class has important limitations as a standalone measure: it is subjective, requires patient communication ability, and may be influenced by comorbid conditions (orthopedic limitations, obesity, anemia) that limit exercise capacity independently of pulmonary vascular disease. For this reason, REVEAL 2.0 complements it with the objective 6MWD measurement.

6-Minute Walk Distance (6MWD)

The 6-minute walk test is the most widely used exercise capacity assessment in PAH, providing an objective, reproducible, and clinically meaningful measure of functional performance. REVEAL 2.0 uses a four-tier stratification:

6MWD Range	Points	Clinical Significance
≥440 meters	-2 (protective)	Near-normal exercise capacity; associated with best survival in PAH cohorts
320-440 meters	-1 (mildly protective)	Mildly impaired capacity; associated with intermediate-good prognosis
165-319 meters	0 (reference)	Moderate impairment; reference range for functional limitation in PAH
<165 meters	+1	Severe functional impairment; associated with markedly elevated mortality

The 440-meter threshold for the protective tier corresponds to the approximate 6MWD associated with near-normal pulmonary hemodynamics and preserved right ventricular function in PAH cohorts. Patients with 6MWD ≥440 m are near the published treatment target endorsed by guideline recommendations for achieving low-risk status. In the COMPERA (Comparative, Prospective Registry of Newly Initiated Therapies for Pulmonary Hypertension) registry and French registry low-risk criteria, 6MWD ≥440 m is one of the three standard non-invasive low-risk criteria.

The 165-meter threshold represents the border of severely impaired exercise capacity and corresponds to a 6MWD below which patients are functionally limited to minimal indoor ambulation. In multiple PAH datasets, 6MWD below 165-200 meters is associated with greater than 20-30% 1-year mortality even on therapy.

Clinicians should interpret 6MWD in the context of patient height, age, and body composition using percent-predicted equations when available, since absolute distance may underestimate functional impairment in tall young patients or overestimate it in elderly or obese patients. However, REVEAL 2.0 uses absolute distance thresholds as derived from the registry data, in which patient demographics were distributed across a broad range.

Domain 5: Vital Signs

Systolic Blood Pressure <110 mmHg (+1 point)

Systemic hypotension in PAH reflects one of two concerning clinical states: either markedly reduced cardiac output with compensatory increase in systemic vascular resistance that fails to maintain adequate perfusion pressure, or a failure of systemic vasoconstriction that represents vasodilatory shock physiology. In either case, systolic BP below 110 mmHg independently predicts worse outcomes in the REVEAL registry and adds 1 point to the composite score.

The 110 mmHg threshold is lower than the traditional hypertension definition boundary (120 mmHg) but reflects the specific risk inflection point observed in the PAH registry population. Many PAH patients, particularly young women, have naturally low-normal blood pressure, so a threshold of 110 mmHg captures patients with truly pathologically low perfusion pressure rather than constitutional hypotension in otherwise well-compensated individuals.

PAH-targeted vasodilator therapies, particularly endothelin receptor antagonists and phosphodiesterase-5 inhibitors, can cause mild systemic blood pressure reduction as an off-target effect. Clinicians should assess whether systolic BP below 110 mmHg in a specific patient reflects drug side effects versus intrinsic hemodynamic compromise.

Heart Rate >96 Beats per Minute (+1 point)

Resting tachycardia above 96 bpm adds 1 point to the REVEAL 2.0 score. Elevated resting heart rate in PAH reflects multiple adverse physiologic states: heightened sympathetic activation as a compensatory response to reduced cardiac output, right ventricular diastolic dysfunction requiring faster heart rates to maintain output, anemia, anxiety, or decompensating right heart failure.

Resting heart rate above 96 bpm was established as the REVEAL 2.0 threshold based on survival curve analysis in the registry cohort. Unlike the traditional "normal" cutoff of 100 bpm, the 96 bpm threshold captures a slightly broader group of patients with meaningful prognostic implications in the PAH-specific context. Heart rate should be measured after at least 5 minutes of quiet seated rest to avoid confounding from exertional tachycardia or white-coat-related sympathetic activation.

Domain 6: Recent Clinical Events

All-Cause Hospitalization Within 6 Months (+1 point)

Any hospitalization within the 6 months preceding the risk assessment adds 1 point to the REVEAL 2.0 score. This variable was newly introduced in REVEAL 2.0 (absent from the original REVEAL calculator) based on the recognition that hospitalization events in PAH patients are independent markers of disease decompensation and deteriorating trajectory, beyond what is captured by a single point-in-time assessment of functional status and biomarkers.

Hospitalization in PAH most commonly occurs for right heart failure decompensation, fluid overload, arrhythmia, respiratory infection, or procedure-related admissions (right heart catheterization, line placement for prostacyclin initiation). Regardless of the immediate precipitating cause, any hospitalization signals that the patient's disease has progressed to a state requiring acute medical intervention, which in itself predicts ongoing risk of further decompensation and death.

Multiple registry analyses have confirmed that hospitalized PAH patients face substantially elevated post-discharge mortality in the weeks to months following admission, analogous to the well-described post-discharge mortality hazard in heart failure. The inclusion of this variable in REVEAL 2.0 directly captures this real-world clinical signal, which complements the more static physiologic variables in the score.

Domain 7: Biomarkers

B-Type Natriuretic Peptide (BNP)

BNP is secreted by ventricular cardiomyocytes in response to increased myocardial wall stress, making it a direct biomarker of right ventricular strain in PAH. REVEAL 2.0 uses a four-tier BNP stratification:

BNP (pg/mL)	Points	Interpretation
<50	-2 (protective)	Near-normal RV wall stress; well-compensated right heart function
50-199	0 (reference)	Mildly elevated; some RV strain but not severe
200-799	+1	Moderately elevated; significant RV dysfunction present
≥800	+2	Severely elevated; advanced RV failure and high mortality risk

The BNP threshold of 50 pg/mL for the protective tier (-2 points) corresponds to a value below which the 2022 ESC/ERS guidelines define low-risk biomarker status. This alignment with international guideline low-risk criteria is not coincidental: the REVEAL 2.0 derivation and guideline development processes both drew from contemporary registry datasets demonstrating that BNP below 50 pg/mL is associated with near-normal 1-year survival in PAH.

The four-tier grading in REVEAL 2.0 captures the dose-response relationship between BNP elevation and mortality, which was inadequately represented by the original REVEAL score's single dichotomous BNP cutoff. Patients with BNP of 800 pg/mL or above represent a population with severe RV decompensation analogous to acute decompensated heart failure and face substantially higher 1-year mortality than those in the 200-799 pg/mL range.

N-Terminal Pro-BNP (NT-proBNP) (Alternative to BNP)

NT-proBNP, the biologically inactive amino-terminal cleavage product of the pro-BNP precursor, is measured in preference to BNP in many clinical laboratories because of its longer half-life, greater stability in vitro, and higher absolute concentrations that facilitate measurement across a wider dynamic range. REVEAL 2.0 formally incorporates NT-proBNP as an alternative to BNP using a three-tier stratification:

NT-proBNP (pg/mL)	Points
<300	-2 (protective)
300-1,099	0 (reference)
≥1,100	+2

The NT-proBNP thresholds are approximately 6-fold higher than the corresponding BNP thresholds, reflecting the typical NT-proBNP:BNP ratio observed in clinical practice. The 300 pg/mL low-risk cutoff for NT-proBNP mirrors the ESC/ERS 2022 guideline low-risk criterion for this biomarker.

Only one biomarker should be entered per REVEAL 2.0 calculation. Using BNP from one institution and NT-proBNP from another in serial comparisons may introduce measurement inconsistency. Clinical programs should standardize biomarker measurement to a single assay type and, ideally, a single laboratory to ensure trend comparability over time.

Both BNP and NT-proBNP levels are influenced by factors beyond RV wall stress: renal clearance significantly affects NT-proBNP levels (which increase substantially with declining eGFR, independent of cardiac status), obesity modestly reduces BNP levels, and assay standardization varies across manufacturers. These confounders should be considered when interpreting biomarker-based risk tier assignment, particularly in elderly patients with CKD or obesity where standard thresholds may misclassify true cardiac status.

Domain 8: Echocardiographic Parameter

Pericardial Effusion (+1 point)

The presence of a pericardial effusion on echocardiography adds 1 point to the REVEAL 2.0 score. Pericardial effusion in PAH is a hallmark of advanced right ventricular failure, occurring through several mechanisms: elevated right atrial pressure impairs lymphatic drainage of the pericardial space, the dilated, hypertrophied right ventricle exudes transudative fluid as its wall stress increases, and tricuspid regurgitation can promote pericardial fluid accumulation.

Pericardial effusion in PAH is associated with worse hemodynamics (lower cardiac index, higher right atrial pressure, higher pulmonary vascular resistance), worse functional class, and substantially higher mortality in multiple registry analyses. Even small pericardial effusions in PAH patients are clinically meaningful, as they often represent a tipping point in the trajectory of RV decompensation rather than incidental findings.

The effusion should be assessed on a standard transthoracic echocardiogram obtained within a clinically relevant timeframe (typically within 6-12 months of the assessment date). Large effusions causing hemodynamic compromise (pericardial tamponade) require urgent intervention and represent a clinical emergency beyond the scope of risk scoring.

Domain 9: Pulmonary Function

DLCO <40% Predicted (+1 point)

Diffusing capacity of the lungs for carbon monoxide (DLCO) below 40% of predicted adds 1 point to the REVEAL 2.0 score. DLCO measures the efficiency of alveolar gas exchange and reflects the combined surface area, membrane thickness, and capillary blood volume available for gas transfer across the alveolar-capillary interface.

Reduced DLCO in PAH patients may reflect several disease processes: obliteration of the pulmonary capillary bed by progressive vascular remodeling reduces the capillary blood volume available for CO uptake; coexistent interstitial lung disease (particularly in CTD-PAH) reduces alveolar surface area; and low cardiac output reduces pulmonary transit time and capillary recruitment, further impairing gas exchange.

DLCO below 40% predicted is a particularly important risk signal in CTD-PAH patients, where it may indicate significant underlying interstitial lung disease that contributes independently to exercise limitation and mortality beyond the PAH component. In these patients, management decisions about PAH-targeted therapy must account for the possibility that exercise limitation and gas exchange impairment are driven partly or largely by the parenchymal lung disease, which does not respond to pulmonary vasodilators.

Domain 10: Invasive Hemodynamics

Mean Right Atrial Pressure (mRAP) >20 mmHg (+1 point)

A mean right atrial pressure above 20 mmHg within the preceding year adds 1 point to the REVEAL 2.0 score. The mRAP measured during right heart catheterization (RHC) is a direct hemodynamic marker of right ventricular filling pressure and right heart failure severity in PAH.

Elevated mRAP in PAH indicates that the right ventricle is unable to generate adequate stroke volume without relying on excessively elevated filling pressures, a pattern analogous to the elevated left ventricular end-diastolic pressure in left heart failure. As mRAP rises above 10-12 mmHg, venous pressure elevation progressively affects hepatic function (causing congestive hepatopathy), renal perfusion (contributing to cardiorenal syndrome), and gastrointestinal absorption (causing bowel wall edema and protein-losing enteropathy). The threshold of 20 mmHg represents severe right-sided venous hypertension associated with overt right heart failure.

In the ESC/ERS 2022 guideline risk stratification framework, mRAP above 14 mmHg places patients in the intermediate-to-high-risk category, and values above 20 mmHg indicate severe hemodynamic derangement. The REVEAL 2.0 threshold of 20 mmHg was derived empirically from the REVEAL registry survival analysis and selects for patients at particularly high risk.

Pulmonary Vascular Resistance (PVR) <5 Wood Units (-1 point, protective)

PVR below 5 Wood units (400 dynes·s·cm^-5) is the only hemodynamic variable in REVEAL 2.0 assigned a negative (protective) score. PVR is calculated from RHC data as (mean PAP - PAWP) / cardiac output and quantifies the resistance in the pulmonary vascular bed.

PVR below 5 Wood units reflects less severe pulmonary vascular remodeling and greater preservation of pulmonary vascular reserve. Patients with lower PVR at diagnosis or at follow-up assessments have consistently better prognosis in registry analyses, a finding that aligns with the biological principle that degree of structural vascular remodeling (and hence PVR) directly determines the severity of RV pressure overload and the trajectory toward right heart failure.

The PVR threshold of 5 Wood units in REVEAL 2.0 is slightly more stringent than the PAH diagnostic threshold of ≥2 Wood units, capturing a subset of PAH patients with relatively preserved vascular resistance. In contemporary combination therapy trials, reduction in PVR to below 5-7 Wood units is often used as a secondary endpoint reflecting meaningful therapeutic response.

Because PVR requires formal RHC for measurement, this variable may not be available at every routine clinic visit. REVEAL Lite 2 (the abridged version described below) omits invasive hemodynamic variables, making it suitable for assessments when RHC data are not current.

Risk Stratification: Interpreting the Score

The composite REVEAL 2.0 score (base 6 + sum of variable points) maps to three risk tiers with defined 1-year mortality probabilities:

Total Score	Risk Category	Approximate 1-Year Mortality	Treatment Implication
0-6	Low Risk	≤2-5%	Continue current therapy; optimize adherence; monitor every 3-6 months; consider step-down if stable and on maximal therapy
7-8	Intermediate Risk	5-10%	Re-evaluate therapy; consider addition of a second or third PAH agent if not already on combination; assess reversible drivers; reassess in 3 months
≥9	High Risk	>10%	Urgent treatment intensification; parenteral prostacyclin if not already initiated; lung transplant evaluation; palliative care discussion; consider hospitalization

The treatment implications listed above reflect consensus guidance from the 2022 ESC/ERS pulmonary hypertension guidelines and current PAH expert consensus statements. The REVEAL 2.0 score provides the numeric risk estimate; the specific therapeutic response should integrate the score with the full clinical picture including etiology, comorbidities, drug tolerability, and patient preferences.

The Treatment Goal: Achieving Low-Risk Status

A central principle of contemporary PAH management, formalized in the 2022 ESC/ERS guidelines, is that the treatment goal is to achieve and maintain low-risk status. This goal-oriented management strategy represents a paradigm shift from the earlier approach of initiating therapy and assessing symptoms, toward a systematic, serial risk-assessment-driven escalation strategy.

Data from multiple registries support this goal: patients who achieve low-risk status (by REVEAL 2.0, ESC/ERS criteria, or French non-invasive criteria) at any point during their disease course have markedly better survival than those who remain in intermediate or high-risk categories, regardless of when during their disease course low-risk status is achieved. This implies that achieving low risk through treatment intensification can alter the natural history of PAH, not merely delay it.

The practical consequence is that REVEAL 2.0 should be calculated not only at diagnosis but serially at each major clinic visit (typically every 3-6 months, or after treatment changes). The trajectory of the score (improving, stable, or worsening) provides additional prognostic information beyond any single time-point calculation. A patient whose score improves from 10 to 6 following initiation of combination therapy has achieved a clinically meaningful milestone that justifies continued monitoring on the current regimen. A patient whose score remains at 9 or above despite optimization signals the need for escalation or transplant evaluation.

Clinical Applications of REVEAL 2.0

Diagnosis and Initial Risk Stratification

At the time of PAH diagnosis (confirmed by right heart catheterization), REVEAL 2.0 provides a baseline mortality estimate that guides initial treatment intensity. Newly diagnosed patients with a score of 9 or above (high risk) should generally be considered for immediate initiation of dual or triple combination therapy, including parenteral prostacyclin, without waiting for monotherapy failure. Patients presenting at low risk (score ≤6) may be appropriately initiated on oral combination therapy with a goal of maintaining or improving their low-risk status. Intermediate-risk patients (score 7-8) are the group where therapeutic judgment is most nuanced, often requiring careful selection of initial combination therapy with early reassessment.

Sequential Monitoring and Treatment Escalation

REVEAL 2.0 is designed for serial application every 3-6 months or whenever a clinically significant event occurs (hospitalization, functional class worsening, new biomarker elevation). Serial comparisons allow identification of patients who are:

• Stable at low risk: Continue current therapy; consider whether further optimization is possible
• Improving toward low risk: Evidence of treatment response; encourage adherence; targeted reassessment at next visit
• Stable at intermediate risk: Insufficient treatment response; evaluate barriers to combination therapy (tolerability, cost, access); consider adding a second agent if on monotherapy
• Worsening or at high risk: Immediate clinical reassessment; urgent therapy intensification; hospitalization if hemodynamically compromised; transplant referral if not already active

Lung Transplant Referral Timing

Lung transplantation remains the only curative option for patients with PAH refractory to maximal medical therapy. The optimal timing of transplant referral and listing is one of the most challenging decisions in PAH management: referral too early wastes scarce organ resources, while referral too late may result in deterioration beyond the threshold of transplant candidacy.

A sustained high REVEAL 2.0 score (≥9) despite optimal combination therapy, particularly with mRAP >20 mmHg and 6MWD <165m, represents a strong indicator for transplant listing evaluation. The ESC/ERS 2022 guidelines recommend transplant referral when patients fail to reach an intermediate or low-risk profile after 3-6 months of combination therapy, and REVEAL 2.0 provides a numeric framework for applying this recommendation.

Clinical Trials and Research Endpoints

REVEAL 2.0 has been incorporated as a risk stratification variable in multiple PAH clinical trials, enabling risk-adjusted analysis of treatment effects across patient subgroups. Because the score is derived from a large registry and has been externally validated in independent cohorts, it provides a standardized comparator for assessing whether new therapies achieve meaningful improvements in PAH risk tier distribution. Some investigators have proposed REVEAL 2.0 score change as a clinical trial endpoint, analogous to the use of risk score change in other cardiovascular diseases.

REVEAL Lite 2: The Abridged Non-Invasive Score

Recognizing that right heart catheterization data (mRAP, PVR) are not routinely available at every follow-up clinic visit, and that pericardial effusion on echocardiography requires recent imaging, Benza et al. developed REVEAL Lite 2 (published in Chest, 2021) as a six-variable, non-invasive abridged version of REVEAL 2.0.

REVEAL Lite 2 uses: WHO/NYHA functional class, systolic blood pressure, heart rate, 6MWD, BNP or NT-proBNP, and eGFR. These are all variables obtainable at a routine outpatient clinic visit without invasive procedures or specialized imaging. The point assignments and base score differ from REVEAL 2.0 to optimize the abbreviated model's calibration without the hemodynamic and echocardiographic variables.

In validation studies, REVEAL Lite 2 demonstrated similar risk tier discrimination to REVEAL 2.0 for most patients, making it practical for routine outpatient follow-up visits between formal hemodynamic assessments. The full REVEAL 2.0 should be used when right heart catheterization data are current (typically at diagnosis, after major treatment changes, and in patients being evaluated for transplant listing), while REVEAL Lite 2 serves as the monitoring tool at interim visits.

REVEAL Lite 2 is intentionally not a replacement for REVEAL 2.0 but rather a complementary tool optimized for the practical reality of PAH outpatient care, where invasive data are available at finite intervals but non-invasive assessments occur more frequently.

Comparison with ESC/ERS Risk Stratification

The 2015 and 2022 ESC/ERS pulmonary hypertension guidelines recommend a simplified risk stratification approach using a defined set of non-invasive and invasive low-risk criteria, including WHO FC I-II, 6MWD >440m, BNP <50 pg/mL (NT-proBNP <300 pg/mL), absence of pericardial effusion, mRAP <8 mmHg, cardiac index ≥2.5 L/min/m², and mixed venous oxygen saturation >65%. Risk tier is determined by counting how many of these criteria are met (most criteria met = low risk; none or few met = high risk).

The REVEAL 2.0 and ESC/ERS approaches are complementary rather than competing. Key differences include:

Feature	REVEAL 2.0	ESC/ERS Criteria
Output	Continuous numeric score mapped to mortality probability	Semi-quantitative low/intermediate/high based on criteria count
Etiology	Explicitly incorporated (PAH subgroup points)	Not incorporated in risk calculation
Demographics	Male >60 years explicitly scored	Not incorporated
Renal function	eGFR <60 scored	Not incorporated
Hospitalization	Within 6 months scored (+1)	Rapidly progressive deterioration noted but not formally scored
DLCO	Incorporated (<40% adds +1)	Not incorporated
Invasive variables	mRAP >20 mmHg, PVR <5 WU	mRAP, cardiac index, SvO2 (more variables)
Validation setting	REVEAL (US), COMPERA (European), French registry	European registries primarily

Head-to-head comparisons in COMPERA and the French registry have shown that REVEAL 2.0 and the ESC/ERS non-invasive criteria have comparable discriminative ability (c-statistics within the range of 0.70-0.78). Current expert opinion supports using multiple complementary risk stratification approaches rather than relying exclusively on any single tool, as each captures somewhat different aspects of disease severity and trajectory.

Special Populations and Applicability Considerations

CTD-PAH: Systemic Sclerosis and Other Connective Tissue Diseases

REVEAL 2.0 was derived from a registry that included approximately 15-20% CTD-PAH patients, the majority with systemic sclerosis (SSc). The +1 point for CTD-PAH reflects the established worse prognosis of this subgroup but may underestimate the risk heterogeneity within CTD-PAH (SSc-PAH has substantially worse outcomes than lupus-associated PAH or undifferentiated connective tissue disease-PAH). Clinicians managing SSc-PAH patients should apply REVEAL 2.0 with awareness that this subgroup's true prognosis may be worse than the CTD-PAH category average, particularly in patients with significant concurrent interstitial lung disease or Raynaud's phenomenon with digital ischemia.

Congenital Heart Disease-Associated PAH (CHD-PAH)

CHD-PAH has a highly variable prognosis depending on the underlying anatomy (simple vs. complex defects), history of surgical repair, and the presence of Eisenmenger physiology. The REVEAL registry included CHD-PAH patients, and this subgroup receives 0 points for etiology (categorized as "other"), which may underestimate the prognostic diversity within this group. Eisenmenger syndrome, in particular, has a distinctive prognosis and natural history compared to repaired or simple CHD-PAH and may require specific prognostic tools beyond REVEAL 2.0.

Drug- and Toxin-Induced PAH

PAH associated with anorexigens (fenfluramine derivatives), methamphetamine, or other toxins is categorized as "other" (0 points for etiology). Outcomes in this subgroup depend on the extent of vascular remodeling at diagnosis and whether the causative agent has been discontinued. Recent methamphetamine-associated PAH has been increasingly recognized and may have a distinct, often severe, presentation requiring aggressive initial therapy.

Elderly Patients

REVEAL 2.0 explicitly incorporates age through the male >60 year demographic variable and the eGFR component. However, in elderly patients (above 70-75 years), additional considerations arise that the score does not directly capture: frailty, polypharmacy interactions with PAH therapies, reduced tolerance for side effects of vasodilator therapy, and comorbid left heart disease that may coexist with or mimic Group 1 PAH. Right heart catheterization with careful attention to pulmonary artery wedge pressure and vasodilator challenge is particularly important in elderly patients to ensure accurate Group 1 classification before applying REVEAL 2.0.

Practical Score Calculation: Examples

Example 1: Low-Risk Profile at Diagnosis

A 38-year-old woman diagnosed with idiopathic PAH presents with WHO FC II symptoms, systolic BP 118 mmHg, heart rate 82 bpm, 6MWD 460m, BNP 32 pg/mL, no pericardial effusion, DLCO 68% predicted, mRAP 9 mmHg, PVR 4.2 Wood units, eGFR 88, no recent hospitalization.

Score: 6 (base) + 0 (IPAH) + 0 (not male >60) + 0 (eGFR ≥60) + 0 (FC II) + 0 (SBP ≥110) + 0 (HR ≤96) + 0 (no hospitalization) + (-2) (6MWD ≥440m) + (-2) (BNP <50) + 0 (no effusion) + 0 (DLCO ≥40%) + 0 (mRAP ≤20) + (-1) (PVR <5) = 1 point: Low Risk, estimated 1-year mortality ≤5%.

This patient has excellent objective markers at diagnosis. Current guidelines support initiating combination oral therapy (ERA + PDE-5i) with a goal of maintaining low-risk status.

Example 2: High-Risk Profile Requiring Urgent Action

A 67-year-old man with systemic sclerosis-associated PAH presents with WHO FC IV, hospitalized twice in the past 4 months, SBP 98 mmHg, HR 108 bpm, 6MWD 90m, NT-proBNP 2,400 pg/mL, pericardial effusion present, DLCO 28% predicted, mRAP 24 mmHg, PVR 11 Wood units, eGFR 48.

Score: 6 (base) + 1 (CTD-PAH) + 2 (male >60) + 1 (eGFR <60) + 2 (FC IV) + 1 (SBP <110) + 1 (HR >96) + 1 (recent hospitalization) + 1 (6MWD <165m) + 2 (NT-proBNP ≥1,100) + 1 (effusion) + 1 (DLCO <40%) + 1 (mRAP >20) + 0 (PVR ≥5) = 21 points: High Risk, estimated 1-year mortality >10% (likely substantially higher at this score level).

This patient requires urgent hospitalization, initiation or dose escalation of parenteral prostacyclin therapy, right heart failure management with diuresis and hemodynamic optimization, and immediate lung transplant evaluation.

Example 3: Intermediate Risk with Treatment Decision Point

A 52-year-old woman with heritable PAH (BMPR2 mutation confirmed) on ERA monotherapy, WHO FC III, SBP 112 mmHg, HR 88 bpm, 6MWD 310m, BNP 380 pg/mL, no pericardial effusion, DLCO 55% predicted, mRAP 14 mmHg, PVR 6.8 Wood units, eGFR 74, no hospitalization in past 6 months.

Score: 6 (base) + 2 (heritable) + 0 (female) + 0 (eGFR ≥60) + 1 (FC III) + 0 (SBP ≥110) + 0 (HR ≤96) + 0 (no hospitalization) + 0 (6MWD 165-319m) + 1 (BNP 200-799) + 0 (no effusion) + 0 (DLCO ≥40%) + 0 (mRAP ≤20) + 0 (PVR ≥5) = 10 points: High Risk.

Despite the clinical appearance of a moderately symptomatic patient, the heritable etiology penalty (+2) and the BNP elevation shift this patient into high-risk territory. Current guidelines support adding a second agent (PDE-5 inhibitor or soluble guanylate cyclase stimulator) and reassessing within 3 months, with consideration of parenteral prostacyclin if the next assessment shows failure to achieve significant score improvement.

Limitations and Important Caveats

• WHO Group 1 PAH only: REVEAL 2.0 was derived and validated exclusively in WHO Group 1 PAH. Application to Group 2 (pulmonary hypertension due to left heart disease), Group 3 (lung disease/hypoxia), Group 4 (CTEPH), or Group 5 (miscellaneous mechanisms) PAH is not validated and may generate profoundly inaccurate risk estimates. Correct classification of patients as WHO Group 1 before applying the score requires careful hemodynamic evaluation.
• US-predominant registry population: The REVEAL registry enrolled patients at 54 US sites with the demographic and etiologic distribution characteristic of North American PAH practice. Patient populations in Europe, Asia, and other regions may have different etiologic distributions (lower rates of IPAH, higher rates of specific CTD-PAH or CHD-PAH subtypes), different comorbidity profiles, and different healthcare access patterns that may affect the score's calibration in those settings.
• Historical treatment era: The REVEAL registry enrolled patients between 2006 and 2012. Since that period, the PAH therapeutic landscape has expanded substantially: newer prostacyclin receptor agonists (selexipag), soluble guanylate cyclase stimulators (riociguat), and the AMBITION trial establishing upfront dual combination therapy as superior to sequential monotherapy have altered outcomes and may change the prognostic weight of individual score variables in contemporary practice.
• Static single time-point assessment: Each REVEAL 2.0 calculation reflects a specific moment in the patient's disease course. PAH is a dynamic disease, and a single score does not capture the trajectory of disease progression or regression. Serial scores provide substantially more information than any single assessment, and the rate of change between scores carries independent prognostic significance not captured by any individual calculation.
• Invasive variable dependency: The full REVEAL 2.0 requires mRAP and PVR from right heart catheterization, which may not be current at every clinic visit. Missing these variables necessitates either use of REVEAL Lite 2 (which excludes them) or assumptions that may introduce scoring inaccuracy.
• BNP/NT-proBNP confounders: Both natriuretic peptides are influenced by renal function, obesity, and assay variability. NT-proBNP is disproportionately elevated in patients with CKD, and BNP may be falsely reassuring in obese patients. These confounders can misclassify biomarker risk tier independent of true right ventricular function.
• Mortality vs. morbidity outcomes: REVEAL 2.0 predicts all-cause in-hospital mortality, not morbidity endpoints (hospitalization-free survival, transplant-free survival, functional class maintenance) that are increasingly recognized as equally important patient-centered outcomes in long-term PAH management. Clinical trial endpoints and quality-of-life measures provide complementary information that the mortality-focused REVEAL 2.0 score does not capture.
• Race and socioeconomic factors: The REVEAL registry's enrollment at US academic centres may over-represent specific racial and socioeconomic groups relative to the general PAH population. The score does not incorporate socioeconomic determinants of health (insurance status, geographic access to PAH specialty care, adherence barriers) that substantially affect real-world outcomes.

Frequently Asked Questions

At what frequency should REVEAL 2.0 be calculated?

Current ESC/ERS guidelines recommend comprehensive risk assessment at PAH diagnosis, at 3-6 months after treatment initiation or change, and every 6 months in stable patients. REVEAL 2.0 can be calculated at each assessment that includes current values for all required variables. REVEAL Lite 2 may be calculated more frequently (e.g., at every clinic visit) given its non-invasive variable requirement. After hospitalization or a significant clinical event, reassessment within 4-8 weeks of discharge is appropriate.

Can REVEAL 2.0 guide treatment decisions in patients already on combination therapy?

Yes. REVEAL 2.0 is applicable throughout the PAH treatment course, not only at diagnosis. A patient who has been on dual combination therapy for 12 months and achieves a score of 4 (low risk) has reached the treatment target and may continue current therapy with monitoring. A patient whose score rises from 6 to 9 despite combination therapy has failed to maintain low-risk status and warrants escalation to triple combination therapy or parenteral prostacyclin. The score's serial utility is as important as its initial diagnostic application.

What if a patient has both BNP and NT-proBNP measured? Which should be used?

Only one biomarker should be entered per REVEAL 2.0 calculation. In clinical practice, most institutions use one assay type consistently. If both are available, use whichever is more recently measured and most representative of the patient's current status. Avoid mixing biomarker types between serial assessments, as the absolute values are not interchangeable on a 1:1 basis despite both reflecting the same underlying biological process.

How should REVEAL 2.0 be interpreted in patients who cannot perform a 6MWT?

Some patients are unable to perform the 6MWT due to orthopedic limitations, severe dyspnea at rest (FC IV), or cognitive impairment. In these cases, clinical judgment is required: a patient with FC IV symptoms and severe dyspnea at rest should have 6MWD estimated as <165m (the worst tier), as this reflects their functional state even without formal testing. For patients with orthopedic or other non-cardiopulmonary 6MWT limitations, cardiopulmonary exercise testing (CPET) with peak VO₂ measurement may provide a more valid functional capacity estimate than estimated 6MWD.

Does achieving a low REVEAL 2.0 score mean PAH therapy can be reduced or discontinued?

No. Achieving low-risk status is a treatment goal that validates the current therapeutic strategy and supports its continuation, not discontinuation. PAH is a progressive disease without a pharmacologic cure. Reduction of PAH therapy in stable low-risk patients has not been studied in controlled trials and carries the risk of hemodynamic deterioration. Treatment de-escalation should never be undertaken without specialist consultation and careful discussion of risk, even in patients who appear clinically well-compensated by all risk measures.

Is REVEAL 2.0 applicable to patients with pulmonary hypertension who do not meet the PAH WHO Group 1 criteria?

No. REVEAL 2.0 should not be applied to patients with pulmonary hypertension due to left heart disease (Group 2), chronic lung disease (Group 3), chronic thromboembolic pulmonary hypertension (Group 4), or miscellaneous mechanisms (Group 5). Application of a score derived from Group 1 PAH patients to other PH groups would produce unreliable risk estimates, as the prognostic determinants differ substantially between groups. For CTEPH patients, dedicated CTEPH-specific risk models should be used after appropriate evaluation for surgical or interventional candidacy.