17.1 Pulmonary Hypertension, RAP/PASP Estimation, and RV Consequences
Key Takeaways
- Echo estimates PH probability and RV consequences, while invasive hemodynamics define PH and distinguish pre- from postcapillary physiology when clinically required.
- RVSP equals 4(TR velocity)² plus RAP only when the TR envelope is complete and aligned; it approximates PASP only without pulmonic or RVOT obstruction.
- IVC-based RAP categories require spontaneous breathing and are qualified by effort, ventilation, abdominal pressure, athletic adaptation, volume change, and supportive venous findings.
- Septal timing, RV remodeling and function, PA/RVOT patterns, PR, RA/venous congestion, left-heart disease, shunts, and loading must corroborate any pressure estimate.
Separate invasive diagnosis from echo probability
Pulmonary hypertension, or PH, is defined invasively by mean pulmonary artery pressure greater than 20 mm Hg at rest. Echocardiography estimates pressure, identifies consequences, and raises or lowers probability; it does not replace right-heart catheterization or independently assign a PH group. Review symptoms, oxygen or ventilator state, blood pressure, rhythm, lung disease, thromboembolic risk, congenital shunt, valve disease, and LV systolic and diastolic findings. The same PASP can have different causes and consequences, while a technically invalid low estimate cannot exclude disease.
Acquire a complete right-heart dataset: RV-focused apical size and function, RA-focused size, TR from multiple windows, pulmonic and RVOT anatomy, septal shape, PA size and flow, IVC, hepatic veins, and left-heart or shunt clues. Record respiration and loading. Acute pressure overload may produce RV dilation and dysfunction without hypertrophy; chronic load can add wall thickening, RA enlargement, secondary TR, and systemic venous congestion.
Calculate RAP and RVSP only from valid inputs
In a spontaneously breathing adult, measure IVC diameter at end-expiration approximately 0.5–3 cm from the RA junction, distal to the hepatic-vein entry. Observe quiet inspiration and a sniff when appropriate. Apply the standard categories as a starting point:
| IVC finding | Estimated RAP | Qualification |
|---|---|---|
| Diameter ≤2.1 cm and collapse ≥50% | 3 mm Hg | Normal range; use 0–5 mm Hg when a range is required |
| Diameter >2.1 cm and collapse <50% | 15 mm Hg | High range; supportive venous findings improve confidence |
| Diameter and collapse are discordant | 8 mm Hg | Intermediate default; integrate RA size, hepatic veins, and clinical context |
Positive-pressure ventilation disrupts the usual collapse relationship. Poor inspiratory effort, elevated intra-abdominal pressure, athletic adaptation, recent fluid change, and inability to visualize the true IVC also limit RAP. Do not select RAP merely to make the final pressure look plausible. Report when the estimate has low confidence.
Obtain CW Doppler through TR from apical, parasternal, RV inflow, and subcostal windows. Align parallel to the jet and save the highest reproducible complete envelope without angle correction. Then calculate:
RVSP = 4(TR peak velocity)² + RAP
A TR velocity of 3.2 m/s gives 4 × 3.2² = 41 mm Hg; adding RAP of 8 mm Hg gives RVSP about 49 mm Hg. Only when no pulmonic-valve or RVOT obstruction exists may RVSP approximate PASP. With obstruction, the value describes RV systolic load and must not be labeled PASP. Use an enhancing agent under laboratory protocol when it can complete a weak envelope, but trace the modal border rather than isolated bright noise.
An incomplete or misaligned TR envelope underestimates velocity, and velocity error is squared. Excessive gain, spectral artifact, or tracing a faint outer edge can overestimate. Severe free TR may cause early RV-RA pressure equalization and underestimate the gradient; RAP may also be less reliable. If no adequate TR signal exists, state that RVSP cannot be estimated rather than assigning a normal pressure. A resting TR velocity at least 2.9 m/s, or at least 2.8 m/s with two or more supportive echo signs, suggests PH, but signal quality and the integrated pattern remain essential.
Integrate adjunctive pressure signs
| Region | Pressure-load clue | Important alternative or limitation |
|---|---|---|
| Interventricular septum | Systolic flattening or LV eccentricity index >1 | Volume load predominates when flattening is mainly diastolic; conduction can alter motion |
| RV | Dilation, hypertrophy, reduced FAC, TAPSE, S′, strain, or 3-D RVEF | Acute versus chronic timing and load change the phenotype |
| PA/RVOT | Dilated PA, shortened acceleration time, midsystolic notching | Flow, heart rate, sample position, and lung disease affect patterns |
| PR Doppler | Elevated end-diastolic or mean PA pressure estimate when a complete signal is present | Alignment, RAP assumption, and poor PR envelope limit calculation |
| RA/systemic veins | RA enlargement, dilated IVC, abnormal hepatic-vein flow | TR, ventilation, AF, and volume state are confounders |
RV-PA coupling adds context. TAPSE/PASP relates a basal longitudinal contraction surrogate to estimated afterload; lower values suggest inadequate adaptation, but the ratio inherits every error in both inputs and is not a direct pressure-volume measurement. Assess FAC, S′, 3-D RVEF or strain when available, cardiac output, and TR rather than allowing one normal TAPSE to erase other dysfunction.
Describe consequences and possible cause
Pressure overload first increases RV wall stress and septal interaction. Progressive maladaptation produces RV dilation, reduced output, RA enlargement, functional TR, elevated RAP, pericardial effusion, and systemic congestion. A small hyperdynamic LV can reflect underfilling rather than primary LV disease. Compare serial studies under similar oxygenation, ventilation, rhythm, blood pressure, and therapy because afterload and preload can change rapidly.
Search for left-heart disease, valve lesions, intracardiac shunts, chronic thromboembolic clues, and congenital or RVOT obstruction. Echo can suggest postcapillary physiology through LA enlargement, LV hypertrophy, valve disease, or filling evidence, but cannot definitively distinguish pre- from postcapillary PH. Report peak TR velocity, RAP method and confidence, calculated RVSP, whether PASP equivalence is valid, supportive signs, RV adaptation, and limitations. Acute RV failure, a thrombus in transit, suspected acute pulmonary embolic physiology, or severe hemodynamic compromise requires immediate communication through laboratory policy.
Verify serial pressure change
Before declaring progression or improvement, compare the same TR window and envelope quality, RAP method, rhythm, oxygenation, ventilation, blood pressure, and loading state. A change created by a different Doppler border or IVC assumption is measurement disagreement, not proven pulmonary vascular change.
No complete TR envelope, no numeric RVSP
A partial or misaligned signal is not repaired by tracing its faint edge. Report that RVSP cannot be estimated and use the full right-heart pattern; absence of a measurable jet does not prove normal pulmonary pressure.
A complete, well-aligned TR envelope peaks at 3.2 m/s and the integrated IVC assessment supports RAP of 8 mm Hg. What RVSP is estimated?
Which findings strengthen an echocardiographic pattern of pulmonary pressure overload? Select three.
Select all that apply