This prospective observational study aims to evaluate the relationship between the Venous Excess Ultrasound Score (VEXUS) and the ESC/ERS 2022 simplified four-strata risk assessment model in adult patients with World Health Organization (WHO) Group 1 pulmonary arterial hypertension (PAH). The study investigates whether VEXUS can enhance risk stratification and predict haemodynamic congestion by correlating VEXUS with functional, biochemical, and invasive haemodynamic parameters.

Pulmonary arterial hypertension (PAH) is a progressive disorder characterised by increased pulmonary vascular resistance, right ventricular overload, systemic venous congestion, and high mortality. The ESC/ERS 2022 simplified four-strata model (low, intermediate-low, intermediate-high, high risk) guides treatment decisions using WHO functional class, 6-minute walk distance, and BNP/NT-proBNP levels.

However, biochemical markers may be costly or insufficiently sensitive to early haemodynamic deterioration.

VEXUS (Venous Excess Ultrasound Score), a point-of-care ultrasonographic method assessing hepatic, portal, and renal venous Doppler patterns, has shown promise in representing venous congestion.

This study evaluates whether VEXUS correlates with ESC/ERS risk categories and invasive haemodynamic parameters including right atrial pressure, mean pulmonary arterial pressure, pulmonary vascular resistance, cardiac output, and pulmonary output. The study further aims to explore whether integrating VEXUS into PAH follow-up may strengthen risk assessment.

Inclusion Criteria

• Adults aged ≥18 years
• Established diagnosis of WHO Group 1 pulmonary arterial hypertension (PAH)
• Stable outpatient clinical status at the time of VExUS ultrasonography
• Venous Excess Ultrasound Score (VExUS) evaluation performed with adequate ultrasonographic acoustic windows
• Clinically indicated right heart catheterisation (RHC) performed within ±60 days of VExUS assessment
• Availability of ESC/ERS 2022 simplified risk assessment variables (WHO functional class, BNP/NT-proBNP, and 6-minute walk distance)
• Ability to provide written informed consent

Exclusion Criteria

• Pulmonary hypertension other than WHO Group 1, including:

  • PH due to left heart disease (WHO Group 2)
  • PH due to chronic lung disease or hypoxaemia (WHO Group 3)
  • Chronic thromboembolic pulmonary hypertension (CTEPH; WHO Group 4)
  • Multifactorial PH (WHO Group 5)
  • Eisenmenger syndrome
  • Complex or unrepaired congenital heart disease

• Suspected pulmonary veno-occlusive disease (PVOD)

• Pulmonary capillary haemangiomatosis (PCH)

• Acute decompensated right heart failure

• Severe renal dysfunction (eGFR <30 mL/min/1.73 m²)

• Severe hepatic impairment (Child-Pugh Class C)

• Congestive hepatopathy

• Active infection

• Pregnancy

• Inability or unwillingness to provide informed consent

• Poor ultrasonographic acoustic window preventing adequate VExUS scoring

The study population consists of adult patients diagnosed with World Health Organization (WHO) Group 1 pulmonary arterial hypertension (PAH) who are being followed at a tertiary pulmonary hypertension centre. Participants represent a real-world cohort of clinically stable PAH patients attending routine outpatient follow-up visits. All participants undergo non-invasive assessment including VEXUS ultrasonography, 6-minute walk test (6MWT), WHO functional class evaluation, and BNP measurement at the study visit. Recent right and/or left heart catheterisation data (performed within ±2 months for standard clinical indications) are collected from medical records. Patients with other forms of pulmonary hypertension, Eisenmenger syndrome, pulmonary veno-occlusive disease, or pulmonary capillary haemangiomatosis are excluded.

Only de-identified individual participant data (IPD) related to primary and secondary outcome measures may be shared with qualified researchers upon reasonable request. No direct identifiers or protected health information will be released.

Beginning 12 months after publication of the primary manuscript and for up to 3 years thereafter.

Requests must be submitted in writing to the principal investigator. Data will be provided only for methodologically sound proposals and after review by the institutional data governance committee. A data use agreement (DUA) will be required.