Assessment of severity of aortic regurgitation by echocardiography

PresenterDR PRAVEEN GUPTA

Moderator DR AJIT ANANTHAKRISHNA

PILLAI

Date - 2/08/2016

Department of Cardiology,JIPMER

Pondicherry, India

Introduction

Aortic Regurgitation (AR) is diastolic reflux of blood from the aorta to

the LV

Caused by

Malfunction of the aortic valve leaflets

Dilation of the aortic root and annulus

Combination of these factors

Aortic root disease >50% of all Aortic valve replacement (AVRs)

Evaluating the Severity of Aortic Regurgitation

Effective

regurgitant

orifice area

Volume or fraction of regurgitant flow

Size or extent of the regurgitant jet within the LV

Evaluating the Severity of Aortic Regurgitation

By Colour flow imaging Record jet in multiple imaging

planes to provide a three-

dimensional assessment of its

dimensions

Area of the jet,estimated by

planimetry.

Parasternal long-axis view, the

height of the jet just below the

valve measured

This dimension can also be

expressed as a percentage of left

ventricular outflow tract

dimension to provide an estimate

of severity

Three examples of aortic regurgitation are provided, all taken from the parasternal long-axis view using color Doppler. Mild (A), moderate (B), and severe (C) aortic regurgitation are illustrated.

Evaluating the Severity of Aortic Regurgitationby colour flow imaging

The greater the percentage is of the left ventricular outflow tract that is

filled by the jet at its origin, the more severe the regurgitation.

A jet that occupies > 60% of the LVOT (either height or area) indicates

severe AR.

A similar approach uses the short-axis view with the imaging plane

positioned immediately proximal to the aortic valve .

The outflow tract is directly visualized as a circular space, and the

regurgitant jet is visualized as a two-dimensional shape within this circle

Using transesophageal echocardiography, the jet can be visualized from the short-axis view, just below the aortic valve. A: The regurgitant orifice is visualized with two-dimensional imaging. B: Color Doppler is used to demonstrate flow within the regurgitant orifice. C: The regurgitant orifice area is measured by planimetry (0.75 cm2).

Evaluating the Severity of Aortic RegurgitationBy Colour flow imaging

A:The schematic demonstrates how the dimensions of the color jet of aortic regurgitation can be used to estimate severity. B: The jet height just below the aortic valve (arrows) can be measured and compared with the dimension of the left ventricular outflow tract. This is a useful measure of severity

Evaluating the Severity of Aortic RegurgitationBy colour flow imaging

Both length of the jet and area of jet method conveys unreliable

information about overall severity.

The best dimensional predictors of angiographic severity are, jet area

indexed to the LV short-axis area (parasternal short-axis view) and jet

diameter indexed to LVOT diameter immediately proximal to the valve

(paraternal long axis view)

Limitations to the use of color flow mapping

Eccentric jets tends to alter the perception of severity

Size of the jet is instrument dependent.

Changes in gain, color scale, transducer frequency, and wall filters affect

the jet appearance

Jet is greater from an apical view compared with a parasternal view

Regurgitant orifice area in chronic aortic regurgitation changes (and

usually decreases) during diastole, and it lead to color Doppler to

overestimate severity because the visualized jet area would reflect peak

rather than mean orifice area

Vena Contracta

• Narrowest portion of a jet that occurs at or just downstream

from the orifice

• Measure of the effective regurgitant orifice area (EROA)

• Independent of flow rate and driving pressure• Small errors in measurement lead to a large percent error

and misclassification of the severity of regurgitation

Vena Contracta

Vena contracta width of ≥ 6 mm

correlates well with severe AR

(sensitivity 95%, specificity 90%)

Vena contracta width of < 3 mm

specific for mild AR.

Enriquez-Sarano M, et al. NEJM

2004; 351: 1539-1546

.

Proximal Isovelocity Surface Area (PISA)by colour flow

Acceleration of flow occurs proximal

to the valve plane with a series of

isovelocity “surfaces” leading to the

high-velocity jet in the regurgitant

orifice.

Velocity for a PISA =aliasing velocity

where a distinct red-blue interface

seen (at this interface, velocity is

equivalent to Nyquist limit).

Surface area of the PISA region is

2πr2

Proximal Isovelocity Surface Area

Peak regurgitant flow obtained

by multiplying surface area by

aliasing velocity

Effective regurgitant orifice

area (EROA) is peak

regurgitant flow divided by

peak velocity obtained by CW

Doppler.

PISA Limitations

Isovelocity contour flattens as it approaches the orifice,

underestimating flow

Proximal structures can distort the isovelocity contour

Sensitive to errors in radius measurement

10% error in radius leads to 21% error in flow

Multiple measurements

Technically challenging

Evaluating the Severity of Aortic Regurgitation by Continuous Doppler

The simplest approach compares the density or darkness of the envelope of the antegrade

aortic flow and the regurgitant jet.

Mild aortic regurgitation the velocity of the regurgitant jet remains relatively high and the

envelope appears flat.

With more severe aortic regurgitation, steeper slope of the Doppler envelope.

The deceleration of jet velocity can be described as either the slope or the pressure

half-time of the jet

Factors, including aortic compliance, blood pressure, and left ventricular

size and compliance affect these measures

Evaluating the Severity of Aortic Regurgitationby Continuous Wave Doppler

This schematic illustrates how hemodynamic changes are reflected in the Doppler velocity tracing. Left: Mild aortic regurgitation (AR) is associated with a fairly flat contour of the regurgitant jet. Right: As severity increases, the slope of the jet becomes steeper. These changes are the result of the instantaneous pressure gradient between the aorta and left ventricle during diastole

Pressure Half-Time

Rate at which aortic and LV pressures equalize

Most relaible in the setting of acute regurgitation

Rapid rate of decline in aortic pressure is reflected in steeper diastolic

deceleration slope

A pressure half-time less than 250 milliseconds or a slope greater than 400

cm/sec2 are indicators of severe aortic regurgitation

Evaluating the Severity of Aortic RegurgitationPressure Half-Time

Continuous wave Doppler imaging of the aortic regurgitation (AR) jet permits quantitation of both slope and pressure half-time (P½t). Top: An example of mild aortic regurgitation is demonstrated. The slope is relatively flat and the P½t is long. Bottom: An example of severe aortic regurgitation demonstrates a much steeper slope and shorter P½t.

Pressure Half-Time

For a given severity of AR, P1/2 will be shortened by elevated LVEDP or

vasodilator therapy that reduces AR

With acute AR-triangular-shaped CW-Doppler with linear deceleration

slope from maximum velocity to baseline

Pressure Half-Time

Limitations of pressure half-time assessment

Pressure half-time sensitive to chronicity of AR

Acute AR leads to much shorter values than chronic AR when LV is dilated

with increased compliance

Pressure half-time varies with SVR

Vasodilators may shorten the pressure half-time even as the aortic

regurgitant fraction improves

Evaluating the Severity of Aortic Regurgitation Regurgitant Volume or Fraction

Pulsed Doppler imaging

Stroke volume at any valve annulus is derived as the product of CSA and

VTI of flow at the annulus

In the absence of regurgitation, SV determinations at different sites (LVOT,

mitral annulus, pulmonic annulus) should be equal

Mild: < 30 cc (< 30%)

Mild-moderate: 30-44 cc (30-39%)

Moderately severe: 45-59 cc (40-49%)

Severe: ≥60 cc (≥50%)

Evaluating the Severity of Aortic Regurgitation Regurgitant Volume or Fraction

Stroke volume can be measured

through any valve within the

heart. This schematic

demonstrates how stroke volume

can be calculated at the level of

the aortic valve and mitral valve .

The difference in stroke volume

represents the regurgitant volume.

In addition, the regurgitant

fraction can be calculated

Regurgitant Volume or FractionLimitation

Cannot be used in presence of shunts

Sensitive to small measurement errors

Requires multiple measurements,

Assumes no regurgitation at reference valve

Limited quantitative information

Affected by sample volume location

Evaluating the Severity of Aortic Regurgitation Pulsed Doppler imaging

Severe AR - diastolic flow reversal in the descending aorta

Nonquantitative approach using pulsed Doppler imaging

Presence of holodiastolic flow reversal in the descending aorta has been

correlated with severe aortic regurgitation

False positives may occur if a PDA is present

This parameter is dependent on vessel compliance and the location of the

sample volume

Evaluating the Severity of Aortic Regurgitationby M-mode echocardiography and two-dimensional imaging

End-diastolic

End-systolic LV

dimensions

Ejection fraction

Fractional shortening

End-systolic wall stress

LV systolic dysfunction

Increase in end-systolic

dimension

Criteria for Severe AR

Jet width >_65% of LVOT

Vena contracta >0.6 cm

Holodiastolic flow reversal in the proximal abdominal aorta

Rvol>_60 ml/beat

RF>50%

ERO>_0.3 cm2

Angiography grade 3+ to 4+

Evidence of LV dilation

Take Home Message

The best dimensional predictors of angiographic severity are jet area

indexed to the LV short-axis area (parasternal short-axis view) and jet

diameter indexed to LVOT diameter immediately proximal to the valve

(paraternal long axis view)

Jet length is not a reliable index of severity

The pressure half-time is most relaible in the setting of acute regurgitation

Holodiastolic flow reversal is a marker of at least moderate regurgitation

References• Recommendations for Evaluation of the Severity of Native Valvular

Regurgitation with Two-dimensional and Doppler Echocardiography, A report from the American Society of Echocardiography’s Nomenclature and Standards Committee and The Task Force on Valvular Regurgitation

• Feigenbaum's Echocardiography, 6th Edition, Feigenbaum, Harvey; Armstrong, William F.; Ryan, Thomas,Copyright ©2005 Lippincott Williams & Wilkins

• Braunwald's Heart Disease: A Textbook of Cardiovascular Medicine, 10th Edition