11.2 Pulmonic-Valve Anatomy, Structure, and Function
Key Takeaways
- The pulmonic valve usually has anterior, right, and left cusps at the junction of the distal RVOT and MPA, but its anterior position limits single-view visualization.
- Parasternal, PA-focused, subcostal, modified apical, and high windows provide complementary cusp, RVOT, MPA, branch, and Doppler information.
- Sequential PW sampling localizes subvalvular, valvular, supravalvular, or branch acceleration; CW obtains maximum velocity but cannot localize depth.
- Structure, respiration and flow state, PR, RV remodeling, and congenital or postoperative anatomy complete pulmonic-valve functional assessment.
Place the pulmonic valve in the outflow tract
The pulmonic valve is the most superior cardiac valve and lies anterior and slightly left of the aortic valve. It forms the junction between the distal muscular RV outflow tract, or RVOT, and the main pulmonary artery, or MPA. The normal valve usually has thin anterior, right, and left semilunar cusps without chordae or papillary muscles. The left cusp is nearest the aortic root and basal LV septum; the anterior and right cusps overlie the anterolateral RV free wall. Bicuspid, quadricuspid, dysplastic, or absent valves occur, but limited visualization of three cusps does not by itself establish an abnormal cusp number.
The annulus, cusps, sinuses, MPA, and proximal right and left pulmonary arteries form a functional unit. In systole, the cusps open into the sinuses and permit low-resistance ejection; in diastole, they coapt centrally. Thin normal cusps may be difficult to see throughout motion. Trivial or mild physiologic pulmonic regurgitation is common, so detection of a small diastolic color signal does not establish structural disease. Evaluate leaflet tissue, opening, coaptation, flow, and right-heart response together.
Use several windows because the valve is anterior
| Window | How to obtain it | Main information |
|---|---|---|
| Parasternal short axis at aortic level | Angle superiorly toward the left shoulder | RVOT, annulus, cusps, MPA, proximal branches; primary color and CW alignment |
| PA-focused parasternal view | Rotate and tilt from short axis to lengthen MPA and bifurcation | Main and branch PA caliber, supravalvular or branch acceleration |
| Subcostal RVOT | Rotate from subcostal short axis and direct anteriorly | Alternative cusp and RVOT anatomy, useful when parasternal windows are poor |
| Modified apical/RV inflow-outflow | Tilt anteriorly to include RVOT and valve | Additional Doppler alignment and relationship to RV inlet |
| High parasternal or suprasternal | Direct toward MPA and branch arteries when obtainable | Distal MPA or branch stenosis that is outside the standard valve view |
Begin with a narrow, shallow 2-D sector; optimize focus and frequency for the near-field RVOT. Sweep rather than freezing on the first apparent cusp. Color-map from proximal RVOT through the valve, MPA, and visible branches. A low Nyquist setting helps localize subtle acceleration but exaggerates the displayed jet, so reset the scale for documentation. Place PW gates sequentially from RVOT to annulus, distal MPA, and branches. PW identifies where velocity first rises; CW then captures the highest velocity but cannot determine its depth. Biplane and 3-D imaging can show en-face cusp anatomy when image quality permits. TEE, CT, or CMR may be needed when transthoracic windows cannot answer the anatomic question.
Separate the levels of obstruction
| Level | Morphologic or Doppler clue | Common setting |
|---|---|---|
| Subvalvular RVOT | Acceleration begins below a normally opening valve; muscular narrowing may be dynamic | Double-chambered RV, hypertrophic muscle bundles, postoperative anatomy |
| Valvular | Thickened, doming, fused, or dysplastic cusps; color narrows at annulus | Congenital valvular PS, rare rheumatic or carcinoid restriction |
| Supravalvular MPA | Valve opens normally; aliasing and PW step-up begin above annulus | Congenital narrowing, postsurgical or catheter-related change |
| Branch pulmonary artery | MPA may be normal; focal branch acceleration or asymmetric PA size | Congenital branch stenosis, prior repair or intervention |
| High-flow mimic | No discrete narrowing; broadly increased velocity | Anemia, fever, pregnancy, left-to-right shunt, substantial pulmonic flow |
The pulmonary arteries are not fully seen in every adult study. Do not call valvular stenosis merely because CW velocity is high: a continuous-wave beam records every velocity along its path and may include subvalvular, supravalvular, or branch obstruction. Conversely, an apparently normal cusp frame cannot exclude disease when the valve is poorly resolved. State which levels were visualized and which remain uncertain.
Recognize structural patterns and consequences
Congenital valvular PS most often shows systolic doming from commissural fusion with a narrow central opening and poststenotic MPA dilation. A dysplastic valve may be thick, nodular, and poorly mobile without classic doming; the annulus may be small. Rheumatic involvement is uncommon and usually accompanies other valve disease. Carcinoid may thicken and retract right-sided leaflets, causing mixed stenosis and regurgitation. Endocarditis can produce vegetation or destruction, while prior balloon valvuloplasty can leave residual stenosis and increased regurgitation. Repaired congenital disease may include a patch, conduit, prosthesis, or altered branch anatomy; identify what structure is actually being interrogated.
Pressure obstruction produces RV hypertrophy before dilation; advanced disease may lead to RV systolic or diastolic dysfunction, RA enlargement, secondary TR, and systemic venous congestion. Volume overload from significant PR instead favors RV dilation and will be graded in the next chapter. Measure RV wall thickness, size, and function from recommended right-heart views, inspect septal shape, assess RA and IVC, and record TR for RV pressure estimation. A poststenotic MPA may enlarge despite a normal distal PA pressure.
Pulmonary flow varies with respiration and preload. Record several cycles during quiet breathing, note mechanical ventilation, and choose representative, well-aligned beats. In AF or ectopy, average protocol-defined beats and avoid postectopic augmentation. Compare morphology and consequences, not only peak velocity, across serial examinations. A change in oxygenation, cardiac output, pregnancy, anemia, or shunt flow can change Doppler without a change in cusp opening.
Complete a structure-function audit
Before leaving the window, confirm cusp morphology and mobility, annular and MPA dimensions when indicated, the first site of color aliasing and PW acceleration, the best CW envelope, PR presence, RV pressure and remodeling, and associated congenital or postoperative findings. If the anatomy and Doppler disagree, reacquire from another window. Report limited cusp visualization explicitly and recommend advanced imaging through the interpreting clinician when localization affects management. A defensible pulmonic-valve study explains what opens, where flow accelerates, and how the right heart has responded.
PW localizes; CW maximizes
Step a PW sample from the RVOT through the valve into the MPA and branches to find where velocity increases. Use CW afterward for the highest velocity, remembering that CW alone cannot identify the obstruction level.
The pulmonic cusps open normally, RVOT PW velocity is normal, and color aliasing with a PW velocity step-up begins only in the distal main pulmonary artery. What is the best conclusion?
Match each pulmonic outflow structure with its defining relationship or imaging role.
Match each item on the left with the correct item on the right