PVR Index

Critical Unit Alert

Correct units: PVRI is expressed in WU·m² (Wood Units × meters squared). A systematic review (Kwan et al., 2019) found over 50% of literature uses incorrect units (like WU/m²), which can lead to clinical misinterpretation and dosing errors.

Hemodynamic Inputs

Mean PAP (mmHg)

PAWP (mmHg)

Cardiac Index (L/min/m²)

Normal Range (WU·m²)

Normal< 3.0
Elevated3.0 – 6.0
Severe> 6.0

Clinical Precision

Standardization to Body Surface Area (BSA) is critical in assessing pulmonary vascular remodeling. PVRI values are less sensitive to body habitus changes than absolute PVR, making it the preferred metric for transplant listing and complex PAH management.

Evidence-Based Hematology Protocol

Reference: Benza RL, et al. Predicting Survival in PAH: REVEAL Risk Score 2.0. Chest. 2019.

Normal thresholds per 2026 ESC/ERS Guidelines for Pulmonary Hypertension.

Guidelines & Evidence

Verified

Last Review: 2026-07-17

When to Use

Primary Clinical Uses

Assessment of pulmonary vascular disease severity in pulmonary arterial hypertension (PAH)

Determining candidacy for ASD/VSD closure (PVRI >3 WU·m² is a relative contraindication)

Cardiac transplantation evaluation (PVRI >6 WU·m² is a relative contraindication per ISHLT)

Liver transplantation risk stratification (portopulmonary hypertension)

Perioperative hemodynamic monitoring in cardiac surgery

Guiding vasodilator therapy in critically ill patients

Why Indexing Matters

PVRI normalizes absolute PVR to body surface area (BSA). This accounts for varying body size, especially important in pediatric patients and adults with extremes of BSA. A systematic review by Kwan et al. (2019) found that 54.6% of published literature uses incorrect units (e.g., WU/m² instead of WU·m²), leading to potential clinical errors.

How it Works

Formula

PVRI = (mPAP − PAWP) / CI Where: • mPAP = mean pulmonary artery pressure (mmHg) • PAWP = pulmonary artery wedge pressure (mmHg) • CI = cardiac index (L/min/m²) Units: PVRI is expressed in Wood Units · m² (WU·m²) Alternative unit conversion: 1 WU·m² = 80 dynes·sec·cm⁻⁵·m²

Derivation (Ohm’s Law Analog)

PVR = (mPAP − PAWP) / Qp, where Qp = cardiac output (L/min). Indexing divides by BSA: CI = Qp / BSA. Therefore PVRI = (ΔP) / CI. Because CI is in denominator, BSA moves to numerator, giving final units of pressure × time × BSA → WU·m².

Critical Unit Alert

⚠️ INCORRECT: WU/m², WU·m⁻², or dynes·sec·cm⁻⁵·m⁻². These units mathematically invert the BSA correction and will misclassify patients. CORRECT: WU·m² (Wood Units × meters squared).

Reference Values & Thresholds

Category	PVRI (WU·m²)	Clinical Implication
Normal	< 3	Normal pulmonary vascular resistance. Low risk for adverse outcomes.
Elevated (Mild-Moderate)	3 – 6	Pulmonary hypertension. Consider vasodilator testing.
Severe Elevation	> 6	High risk for right heart failure. Relative contraindication for cardiac transplantation (ISHLT).
Prohibitive (ASD/VSD closure)	> 3	AHA/ATS 2015 guidelines advise against defect closure if PVRI >3 WU·m² and PVR index >6 WU·m² post-vasodilator.

Last Comprehensive Review: 2026-07-17

Guidelines & Evidence

Verified

Last Review: 2026-07-17

When to Use

Primary Clinical Uses

Assessment of pulmonary vascular disease severity in pulmonary arterial hypertension (PAH)

Determining candidacy for ASD/VSD closure (PVRI >3 WU·m² is a relative contraindication)

Cardiac transplantation evaluation (PVRI >6 WU·m² is a relative contraindication per ISHLT)

Liver transplantation risk stratification (portopulmonary hypertension)

Perioperative hemodynamic monitoring in cardiac surgery

Guiding vasodilator therapy in critically ill patients

Why Indexing Matters

How it Works

Formula

Derivation (Ohm’s Law Analog)

Critical Unit Alert

Reference Values & Thresholds

Category	PVRI (WU·m²)	Clinical Implication
Normal	< 3	Normal pulmonary vascular resistance. Low risk for adverse outcomes.
Elevated (Mild-Moderate)	3 – 6	Pulmonary hypertension. Consider vasodilator testing.
Severe Elevation	> 6	High risk for right heart failure. Relative contraindication for cardiac transplantation (ISHLT).
Prohibitive (ASD/VSD closure)	> 3	AHA/ATS 2015 guidelines advise against defect closure if PVRI >3 WU·m² and PVR index >6 WU·m² post-vasodilator.

Last Comprehensive Review: 2026-07-17

Recent Journal Updates

JAMAJul 21, 2026

Correction to Primary Composite Outcome in a Trial of Transfusion Strategy

Clinical Context

We think this might be relevant to the clinical guidance for Pulmonary Vascular Resistance Index (PVRI).

FDA MedWatchJul 20, 2026

Early Alert: Intravascular Administration Set Issue from Baxter

Clinical Context

We think this might be relevant to the clinical guidance for Pulmonary Vascular Resistance Index (PVRI).

FDA MedWatchJul 13, 2026

Pulmonary Valve Catheter Delivery System Recall: Medtronic Removes Harmony Delivery Catheter System (DCS)

Clinical Context

We think this might be relevant to the clinical guidance for Pulmonary Vascular Resistance Index (PVRI).

PVR Index

Normal Range (WU·m²)

Clinical Precision

When to Use

Primary Clinical Uses

Why Indexing Matters

How it Works

Formula

Derivation (Ohm’s Law Analog)

Critical Unit Alert

Reference Values & Thresholds

Clinical Pearls

Measurement Pitfalls

Key Evidence from Kwan et al. 2019

Clinical Example of Unit Error

Next Steps

Clinical Actions by PVRI Range

Transplant Listing Criteria (ISHLT 2006)

The Evidence

Primary Reference – Unit Standardization (Clickable)

Pulmonary vascular resistance index: Getting the units right and why it matters

Guideline References (Clickable)

2015 ESC/ERS Guidelines for the diagnosis and treatment of pulmonary hypertension

2015 AHA/ATS Guidelines for Pediatric Pulmonary Hypertension

Listing Criteria for Heart Transplantation: ISHLT Guidelines

Origins & History

Historical Derivation

When to Use

Primary Clinical Uses

Why Indexing Matters

How it Works

Formula

Derivation (Ohm’s Law Analog)

Critical Unit Alert

Reference Values & Thresholds

Clinical Pearls

Measurement Pitfalls

Key Evidence from Kwan et al. 2019

Clinical Example of Unit Error

Next Steps

Clinical Actions by PVRI Range

Transplant Listing Criteria (ISHLT 2006)

The Evidence

Primary Reference – Unit Standardization (Clickable)

Pulmonary vascular resistance index: Getting the units right and why it matters

Guideline References (Clickable)

2015 ESC/ERS Guidelines for the diagnosis and treatment of pulmonary hypertension

2015 AHA/ATS Guidelines for Pediatric Pulmonary Hypertension

Listing Criteria for Heart Transplantation: ISHLT Guidelines

Origins & History

Historical Derivation

Recent Journal Updates

PVR Index

Normal Range (WU·m²)

Clinical Precision

When to Use

Primary Clinical Uses

Why Indexing Matters

How it Works

Formula

Derivation (Ohm’s Law Analog)

Critical Unit Alert

Reference Values & Thresholds

Clinical Pearls

Measurement Pitfalls

Key Evidence from Kwan et al. 2019

Clinical Example of Unit Error

Next Steps

Clinical Actions by PVRI Range

Transplant Listing Criteria (ISHLT 2006)

The Evidence

Primary Reference – Unit Standardization (Clickable)

Pulmonary vascular resistance index: Getting the units right and why it matters

Guideline References (Clickable)

2015 ESC/ERS Guidelines for the diagnosis and treatment of pulmonary hypertension

2015 AHA/ATS Guidelines for Pediatric Pulmonary Hypertension

Listing Criteria for Heart Transplantation: ISHLT Guidelines

Origins & History

Historical Derivation

When to Use