How to trace pulmonary insufficiency (PI) on an echocardiogram (echo)?

How to Trace Pulmonary Insufficiency on Echocardiography

Pulmonary insufficiency (PI) is traced using continuous wave (CW) Doppler by placing the cursor parallel to the regurgitant jet in the right ventricular outflow tract, typically from the parasternal short-axis view or subcostal approach, to obtain the characteristic diastolic flow velocity envelope. 1

Optimal Imaging Windows and Technique

Standard Views for PI Assessment

• Parasternal short-axis view at the level of the aortic valve is the primary window for visualizing the pulmonic valve and obtaining Doppler signals 1
• Subcostal approach provides an alternative window when parasternal views are suboptimal 1
• The pulmonary valve is more difficult to visualize than other valves due to limited acoustic access, so multiple windows should be attempted 1

Color Doppler Mapping First

• Begin with color Doppler to identify the regurgitant jet in the right ventricular outflow tract directed toward the RV 1
• The color jet appears immediately after pulmonary valve closure and extends through diastole 1
• Measure the maximum jet width at its origin (at the junction of the RV outflow tract and pulmonary annulus) in the same frame where you measure the RV outflow tract width 1

CW Doppler Tracing Technique

Cursor Placement

• Align the CW Doppler cursor parallel to the direction of the regurgitant jet as visualized on color Doppler 1, 2
• Position the sample volume just below the pulmonic valve in the RV outflow tract 1
• Optimize the angle to obtain the highest velocity signal (ideally <20 degrees from parallel) 2

Characteristic PI Doppler Pattern

• The normal PI pattern shows a rapid rise in flow velocity immediately after pulmonary valve closure followed by gradual deceleration until the next valve opening 2
• The spectral envelope should be traced from the onset of regurgitation (immediately after P2) through end-diastole 3
• Pathological PI demonstrates holodiastolic flow (throughout diastole) versus physiological PI which is brief and spindle-shaped 1

Key Measurements to Obtain from the CW Doppler Trace

Peak Velocity

• Measure the peak velocity at the beginning of diastole (immediately after valve closure) 2
• Higher peak velocities indicate higher pulmonary artery pressures 2
• The peak velocity can be used to estimate the pulmonary artery to RV pressure gradient using the simplified Bernoulli equation (PG = 4V²) 2

Deceleration Time (DT)

• Trace from peak velocity to the point where velocity reaches baseline 3
• Severe PI shows shorter DT (<261 ms) compared to mild-moderate PI (>317 ms) 3
• DT is measured in milliseconds along the deceleration slope 3

Pressure Half-Time (PHT)

• PHT is the time required for peak velocity to decrease to peak velocity divided by √2 3, 4
• PHT <100 ms indicates severe PI with 93% sensitivity and 93% specificity 3
• PHT >95 ms suggests mild PI 4
• In congenital disease, PHT <100 ms yields good sensitivity and specificity for severe regurgitation 1

Slope of Deceleration

• Calculate the slope by measuring the rate of velocity decrease (in m/s²) 4
• Slope >4.9 m/s² indicates severe PI and is the most valuable parameter for predicting need for pulmonary valve replacement 4
• Steeper slopes (rapid deceleration) indicate more severe regurgitation 4

No-Flow Time (NFT)

• NFT is the time from end of PI flow to onset of next systolic flow 3
• Measure from where the PI Doppler signal returns to baseline until the next systolic ejection begins 3
• NFT >80 ms indicates severe PI with 84% sensitivity and 93% specificity 3
• Calculate NFT/flow time ratio and NFT/diastolic period fraction 3

Diastolic Time-Velocity Integral (TVI)

• Trace the entire diastolic regurgitant envelope to obtain the diastolic TVI 5
• Also measure the systolic forward flow TVI in the main pulmonary artery 5
• Calculate the diastolic/systolic TVI ratio as a quantitative measure 5
• A ratio of 0.49 corresponds to RF of 20%, while 0.72 corresponds to RF of 40% 5

Additional Echocardiographic Signs of Severe PI

Uncommon but Specific Findings

• Holodiastolic flow reversal in the pulmonary artery (detected in 3.7% of severe PI cases) indicates severe regurgitation 6
• Premature opening of the pulmonic valve (seen in 1.5% of severe PI) occurs when RV diastolic pressure exceeds PA pressure 6
• Premature closure of the tricuspid valve (present in 6.6% of severe PI) results from rapid RV pressure rise in diastole 6
• Very low peak velocity of the PI jet (<1.5 m/s) despite severe regurgitation indicates pressure equalization between PA and RV 6
• Laminar retrograde flow pattern (rather than turbulent) can occur in severe PI 6

RV Consequences Assessment

• Measure RV dimensions as RV dilatation (>4.1 cm) suggests hemodynamically significant PI 3
• Assess RV systolic function qualitatively, though absence of RV dilatation does not exclude severe acute PI 1
• Evaluate for interventricular septal flattening which indicates RV volume overload 7

Common Pitfalls to Avoid

Technical Errors

• Do not rely solely on jet width as it is highly dependent on driving pressure and has high inter-observer variability 1
• Avoid measuring PI in the presence of inadequate color Doppler gain settings which can over- or underestimate jet size 1
• Do not use vena contracta width alone as it lacks validation studies and the shape is often complex 1

Interpretation Errors

• PHT is shortened not only by severe PI but also by elevated RV diastolic pressure and restrictive RV physiology 1
• In acute severe PI, RV size may be normal despite severe regurgitation 1
• Color jet area can be brief and inaccurate in severe PI when diastolic pressure equalization occurs early 1

Clinical Context

• Always correlate Doppler findings with 2D imaging of valve morphology to distinguish primary valve pathology from functional regurgitation 1
• Consider that functional PR jets are typically small, central, and spindle-shaped, while pathological PR is holodiastolic and wider 1