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Aortic Regurgitation (AR) on Echocardiography - Detailed Notes

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1. Overview and Role of Echocardiography

• Detection and etiology of AR
• Grading regurgitant severity
• Assessing LV size and systolic function (serial surveillance)
• Timing surgical intervention

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2. Valve Anatomy Assessment (2D Imaging)

Views Used

• Parasternal long-axis (PLAX) - best for leaflet morphology, regurgitant jet origin
• Parasternal short-axis (PSAX) - number of cusps, commissural fusion, calcification
• Apical 5-chamber / 3-chamber - overall valve function
• Suprasternal notch (SSN) and subcostal - aortic flow reversal

Key 2D Findings by Etiology

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3. Indirect Signs of AR (2D / M-mode)

• Anterior mitral leaflet flutter (M-mode): High-frequency diastolic vibration of the anterior mitral leaflet caused by impingement of the AR jet - a classic indirect sign
• Reverse doming of anterior mitral leaflet: In PSAX view the anterior leaflet curves oppositely to rheumatic MS; caused by the AR jet pushing it posteriorly
• Increased E-point septal separation (EPSS): Reflects elevated LV filling or reduced LV function
• Premature mitral valve closure: Seen in acute severe AR when LV diastolic pressure rises rapidly above LA pressure - indicates need for urgent surgery
• Jet lesion: Area of increased echogenicity on the septum or anterior mitral leaflet where the AR jet impinges (fibrotic reaction, seen on 2D)
• LV dilation: Progressive in chronic AR - the largest end-diastolic volumes of all valvular heart diseases

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4. Evaluation of Aortic Regurgitant Severity

Step 1 - Screening Examination (Color Flow + CW Doppler)

• Color flow imaging in PLAX and PSAX identifies the AR jet origin and provides an initial impression of severity
• A central jet filling <25% of LVOT diameter is consistent with mild AR
• CW Doppler from apical approach: a weak or absent diastolic signal below the baseline = no significant AR
• If the screen is positive for more than mild AR, proceed to vena contracta measurement

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Step 2 - Vena Contracta Width (Color Flow, PLAX)

• Accurate for simple (single) jets; not validated for multiple jets
• Eccentric jets: measure perpendicular to the jet long axis, not the LVOT long axis
• 3D vena contracta area shows promise for non-symmetrical orifices but limited by low frame rates

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Step 3 - Jet Width / LVOT Ratio (Color Flow, PLAX)

• Measured in PLAX as the ratio of AR jet width at its origin to the LVOT diameter
• Jet width/LVOT ratio >65% is consistent with severe AR
• Inaccurate for eccentric jets - use vena contracta instead in those cases
• A jet/LVOT area ratio >60% by planimetry of the PSAX view is another criterion

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Step 4 - Aortic Diastolic Flow Reversal (Pulsed Doppler)

• In the suprasternal notch view, holodiastolic flow reversal can be detected in the proximal descending thoracic aorta
• The subcostal window is used to record flow in the proximal abdominal aorta (most specific site for severe AR)

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Step 5 - Continuous-Wave (CW) Doppler Signal

A. Signal Density (Qualitative)

• Compare intensity of the retrograde diastolic signal to the antegrade systolic flow signal
• Dense signal = equal density to antegrade → suggests severe AR (large regurgitant volume)
• Faint/incomplete signal → mild AR

B. Deceleration Slope / Pressure Half-Time (PHT)

• A flat slope (slow deceleration) = aorta-LV pressure gradient maintained throughout diastole = mild AR
• A steep slope (rapid deceleration) = rapid pressure equalization = severe AR (especially acute)

• PHT is affected by LV compliance and arterial pressure, not just regurgitant severity
• Accuracy depends heavily on correct beam alignment with the AR jet - off-axis measurements will underestimate the slope
• In chronic severe AR with compliant LV, PHT may be borderline (200-500 ms); in acute AR, PHT is nearly always <200 ms
• PHT should be used as a complementary finding, not in isolation

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Step 6 - Quantitative Doppler (Volume Flow at Two Sites)

Formulas

• CSA = π × (diameter/2)² (cross-sectional area, assuming circular geometry)
• LVOT diameter measured in PLAX in mid-systole; VTI measured by pulsed Doppler in apical view
• Mitral annulus (MA) diameter measured in apical 4-chamber (PLAX); VTI measured at same level
• VTI_AR = velocity-time integral of the CW Doppler AR signal (the diastolic retrograde signal)

Severity Thresholds

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Step 7 - PISA (Proximal Isovelocity Surface Area) Method

• Regurgitant flow rate = PISA × aliasing velocity
• PISA = 2πr² (hemisphere assumption)
• Shift baseline toward the AR jet direction to an aliasing velocity of 30-40 cm/s for best measurement
• Limitations: poor feasibility with heavy valve calcification; large errors from small mismeasurements (errors are squared); less valid for multiple jets

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5. Summary Severity Criteria Table

• If most parameters are concordant → assign grade
• If discordant → label as indeterminate and use clinical context, CMR, or repeat echo
• Qualitative signs alone are adequate for acute AR because quantitative methods are not accurate when the LV is non-dilated (normal-sized)

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6. Acute vs. Chronic AR - Echo Differences

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7. LV Response - Dimensions and Function

Key Measurements

• In AR, LVEF is an unreliable marker of myocardial contractility because preload is elevated (Frank-Starling effect artificially maintains EF)
• Subclinical myocardial dysfunction can occur with normal LVEF - GLS is more sensitive
• An irreversible decrease in systolic function can occur without symptoms - this is why serial echo is mandatory
• 3D volumetric assessment is preferred over linear measurements because it avoids apical foreshortening

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8. Aortic Root and Ascending Aorta Measurement

• Aortic root dilation may be the primary cause of AR (functional AR from non-coaptation)
• Dilation may coexist even when valve leaflets are the primary culprit

Measurement Sites (PLAX, standard)

1. Annulus
2. Sinuses of Valsalva
3. Sinotubular junction (STJ)
4. Proximal ascending aorta

Intervention Thresholds (diameter)

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9. Disease Staging (ASE/ACC/AHA Framework)

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10. Color Flow Doppler - AR Jet Characteristics

• Central jets: originate at the center of the valve (aortic root dilation, Marfan)
• Eccentric jets: originate from the margin of one leaflet (bicuspid valve, leaflet prolapse, endocarditis)
• Eccentric jets underestimate severity by jet area/width methods → vena contracta is the preferred measure

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11. TEE (Transesophageal Echocardiography)

• Poor TTE windows
• Pre-operative valve repair planning
• Intraoperative guidance (valve repair or replacement)
• Suspected endocarditis (abscess, perforation)
• Aortic dissection (confirm leaflet involvement)

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12. Stress Echocardiography

• Used when symptoms are out of proportion to the degree of AR on resting echo
• Exercise echo can unmask reduced exercise capacity or reveal LV dysfunction not apparent at rest
• Useful in asymptomatic patients where the decision to operate is borderline

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13. Follow-Up Echo Intervals (Surveillance)

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14. Post-TAVR / Post-Surgical Echo

• Assessed immediately post-procedure and on follow-up
• Severity graded using same vena contracta, flow reversal, and quantitative criteria
• Circumferential extent of paravalvular leak on short-axis view: < 10% mild; 10-20% moderate; > 20% severe

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Key Points Summary

1. Screening = color flow PLAX + CW Doppler (apical). Weak CW signal = no significant AR.
2. Vena contracta > 0.6 cm = severe AR (most reproducible single measure).
3. Holodiastolic flow reversal in proximal abdominal aorta = severe AR (most specific qualitative sign).
4. PHT < 200 ms = severe AR (but heavily dependent on LV compliance and beam alignment).
5. Quantitative criteria for severe: RVol ≥ 60 mL, RF ≥ 50%, ROA ≥ 0.30 cm².
6. Premature mitral valve closure = pathognomonic of acute severe AR (LVEDP > LAP).
7. Anterior mitral leaflet flutter = indirect sign of AR jet impingement on MV.
8. LV function thresholds for surgery: LVEF < 50%, LVESD > 50 mm, LVEDD > 65 mm.
9. Always measure aortic root at all four standard levels - dilation may be the primary etiology.
10. Multi-parameter, integrated approach is mandatory - no single criterion is sufficient.

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