Estimating right atrial pressure
RAP is estimated from the IVC diameter and its respiratory variation, then reconciled with secondary signs when the IVC pattern is discordant or unreliable.
Clinically reviewed 22 May 2026 · EchoRapp clinical content
Simple approach
For most spontaneously breathing patients, estimate RAP from IVC size and sniff collapse.
| IVC end-expiratory diameter | Sniff collapse | RAP to enter |
|---|---|---|
| ≤ 2.1 cm | ≥ 50% | 3 mm Hg |
| > 2.1 cm | < 50% | 15 mm Hg |
| Size and collapse discordant | Either pattern | 8 mm Hg, then check secondary signs |
Use the intermediate value when only one IVC criterion is abnormal. If secondary signs are clearly absent, a discordant case can be downgraded to 3 mm Hg; if secondary signs are present, upgrade to 15 mm Hg. When the patient cannot sniff, use quiet-respiration variation instead and read the detailed tutorial.
Detailed tutorial
What this estimate is for
Right atrial pressure (RAP) is reported as a discrete value because it is added directly to Doppler pressure estimates such as RVSP. A wrong RAP category shifts the final pulmonary pressure number by the same number of mm Hg.
Start with the IVC
Use the subcostal view. Measure the IVC at end-expiration, 0.5 to 3.0 cm proximal to the right atrial ostium and distal to the hepatic vein inflow. Keep the same long-axis plane through inspiration; apparent collapse from the IVC moving out of plane should not be counted. Use 2D and, when possible, M-mode to capture the respiratory change.
Ask for a brief sniff when the patient can cooperate. If the patient cannot sniff, use quiet respiration and the lower 20% variation threshold shown below.
Assign the core RAP value
| IVC end-expiratory diameter | Respiratory variation | Interpretation | RAP to enter |
|---|---|---|---|
| ≤ 2.1 cm | ≥ 50% with sniff | Concordant normal | 3 mm Hg |
| > 2.1 cm | < 50% with sniff | Concordant elevated | 15 mm Hg |
| ≤ 2.1 cm | < 50% with sniff | Discordant | Start at 8 mm Hg, then use secondary signs |
| > 2.1 cm | ≥ 50% with sniff | Discordant | Start at 8 mm Hg, then use secondary signs |
If the patient cannot sniff
| IVC diameter | Quiet-respiration variation | RAP to enter | Comment |
|---|---|---|---|
| ≤ 2.1 cm | ≥ 20% | 3 mm Hg | Normal or low RAP pattern |
| ≤ 2.1 cm | < 20% | 8 mm Hg | Indeterminate pattern |
| > 2.1 cm | ≥ 20% | 8 mm Hg | Indeterminate pattern |
| > 2.1 cm | < 20% | 15 mm Hg | Elevated RAP pattern |
| Small and collapsed | Any | <3 mm Hg | Consider hypovolemia |
| > 2.5 cm | < 20% plus venous congestion signs | 20 mm Hg | Markedly elevated RAP can be considered |
Venous congestion signs for the 20 mm Hg pathway include dilated hepatic veins, abnormal hepatic vein systolic/diastolic pattern, stagnant IVC flow, spontaneous echo contrast, or color-flow reflux into the IVC.
Resolve indeterminate cases
Look for secondary signs of elevated RAP before accepting the intermediate value.
- Right atrial enlargement.
- Interatrial septum bowing into the left atrium throughout the cardiac cycle.
- Restrictive right-sided diastolic filling pattern.
- Tricuspid E/e’ > 6.
- Hepatic vein diastolic predominance: HVs/HVd < 1 or HVs filling fraction < 55%.
If secondary signs are absent, downgrade the estimate to 3 mm Hg. If they are present, upgrade to 15 mm Hg. If the secondary signs are incomplete or conflicting, keep 8 mm Hg.
For hepatic vein Doppler in ventilated patients, average at least five beats over at least one respiratory cycle.
Mechanical ventilation and special cases
Warning
Positive-pressure ventilation makes IVC collapse unreliable. Use secondary signs, document the limitation, and keep 8 mm Hg when the estimate remains uncertain; invasive pressure measurement is the reference when the value is clinically decisive.
An IVC diameter ≤ 2.1 cm in an intubated patient supports RAP below 10 mm Hg, but a dilated IVC alone is not enough. Healthy young adults, endurance athletes, and pregnancy can also enlarge the IVC without elevated RAP, so the estimate should be reconciled with the rest of the exam.
What to document
- IVC diameter at end-expiration.
- Collapse or quiet-respiration variation and whether the patient sniffed.
- RAP value entered into the report.
- Any secondary signs that changed an indeterminate estimate.
References
- Monica Mukherjee et al. Guidelines for the Echocardiographic Assessment of the Right Heart in Adults and Special Considerations in Pulmonary Hypertension: Recommendations from the American Society of Echocardiography. J Am Soc Echocardiogr 2025;38(2):141–186. View guideline