Valvular Regurgitation

Basic Principles

Etiology and Severity of Valve Regurgitation

▪ The cause of valve regurgitation often can be inferred from the anatomy and motion of the valve and supporting structures.
▪ Measurement of regurgitant severity is based on the fluid dynamics of flow across the regurgitant orifice (Table 12.1).

Key Points

□ Inadequate leaflet coaptation results in valve leakage, with severity best defined by the size of the regurgitant orifice area (ROA).
□ Upstream from the orifice, flow accelerates in the proximal convergence zone.
□ In the orifice, flow is a laminar with a high velocity, reflecting the pressure difference between the two chambers on either side of the valve.
□ Downstream from the orifice, flow is disturbed with the direction, size, and shape of the regurgitant jet dependent on several factors (Table 12.2).

Vena Contracta (Fig. 12.1)

▪ Narrowest width of the regurgitant jet, measured using color Doppler flow imaging.
▪ Also may be measured with three-dimensional (3D) color imaging.

Key Points

□ Optimal color flow images show flow acceleration proximal to the regurgitant valve and distal jet expansion in the receiving chamber, with the vena contracta being the narrow neck between them.
□ Vena contracta measurements are most accurate with:
- □ The flow signal in the near field of the image (e.g., transthoracic parasternal long-axis views)
- □ A narrow sector width to optimize frame rate
- □ Zoom mode to increase image size
□ Small differences in vena contracta width correspond to substantial changes in regurgitant severity grade so that if a precise and accurate measurement is not possible, other approaches should be used (Table 12.3).
□ 3D imaging of vena contracta area is a promising new approach but remains limited by low temporal resolution.

Proximal Isovelocity Surface Area

▪ Blood flow accelerates proximal to a regurgitant orifice.

TABLE 12.1

Relationship Between Fluid Dynamics of Valvular Regurgitation and Diagnostic Approach
Fluid Dynamic Characteristic	Diagnostic Approach
Conservation of mass through the regurgitant orifice	Continuity equation for regurgitant orifice area (ROA)
High-velocity jet in regurgitant orifice	Pressure-velocity relationship of CW Doppler curve
Proximal flow convergence	Proximal isovelocity surface area (PISA)
Downstream flow disturbance	Jet area in chamber receiving regurgitant flow
Increased volume flow across valve	Stroke volume (SV) across regurgitant minus competent valve

From Otto, CM: Textbook of clinical echocardiography, ed 6, Philadelphia, 2018, Elsevier.

TABLE 12.2

Factors That Affect Regurgitant Jet Size and Shape
Physiologic
Regurgitant volume
Driving pressure
Size and shape of regurgitant orifice
Receiving chamber constraint
Wall impingement
Timing relative to the cardiac cycle
Influence of coexisting jets or flow streams
Technical
Ultrasound system gain
Nyquist limit (pulse repetition frequency)
Transducer frequency
Frame rate
Image plane
Depth
Signal strength

From Otto, CM: Textbook of clinical echocardiography, ed 6, Philadelphia, 2018, Elsevier.

▪ The aliasing velocity on color Doppler flow imaging provides visualization of a contour where all the blood cells have the same velocity (isovelocity) (Fig. 12.2).
▪ The shape of this proximal isovelocity contour typically is a hemisphere so that the proximal isovelcity surface area (PISA) is:

PISA ( cm 2 ) = 2 πr 2

(12.1)

▪ Volume flow rate is area times velocity (in this case, the PISA and aliasing velocity):

Instantaneous flow rate ( cm 3 / s ) = PISA ( cm 2 ) × V aliasing ( cm / s )

(12.2)

Key Points

□ The PISA is best visualized from a window where the ultrasound beam is parallel to the flow direction, typically the apical long-axis or 4-chamber view for mitral regurgitation.
Fig. 12.1 Fluid dynamics of valve regurgitation.Streamlines of blood flow are shown in red. Flow proximal to the regurgitant orifice increases in velocity as the flow stream narrows into the regurgitant orifice. A proximal isovelocity surface area (PISA) is represented by the blue line that connects points with the same velocity on each stream line. Multiple PISA are present proximal to the orifice; the PISA seen with color flow depends on the aliasing velocity of the color scale. The flow stream continues to narrow beyond the orifice with the narrowest point or vena contracta reflecting regurgitant severity.
□ The aliasing velocity is decreased to 30 to 40 cm/s in the direction of flow by shifting the Doppler baseline, which enhances PISA visualization.
□ Both a narrow color sector and zoom mode are used for accurate measurement.
□ PISA measures instantaneous flow rate (cm³/s). PISA must be integrated over the flow period to obtain flow volume (cm³ or mL).
□ PISA may be inaccurate when the proximal flow field is not hemispherical, so this approach is more useful for central jets compared with eccentric jets.
□ It is more difficult to visualize the PISA when regurgitation is mild, and it is more difficult to visualize a PISA for aortic, compared with mitral, regurgitation.
□ Identification of the valve plane by two-dimensional (2D) or 3D imaging is critical, because the PISA measurement is from the aliasing velocity to the valve orifice.

TABLE 12.3

Doppler Evaluation of Valvular Regurgitation
Method	Doppler Parameters	Limitations	Correlation with Other Imaging Modalities
Color flow imaging	• Jet origin • Jet direction • Jet size	• Variation with technical and physiologic factors	• LV or aortic angiography • CMR flow visualization
CW Doppler	• Signal intensity • Shape of velocity curve	• Qualitative	• Invasive hemodynamics • CMR velocity data
Vena contracta width	• Width of jet origin	• Small values, careful measurement needed	• CMR flow visualization
Proximal isovelocity surface area (PISA)	• Calculation of RVol and ROA	• Less accurate with eccentric jets • Peak values only	• CMR flow visualization
Volume flow at two sites	• Calculation of RVol and ROA	• Tedious	• Invasive RVol and RF • CMR measurement of volume flow rates. • CMR LV and RV SVs
Distal flow reversals	• Pulmonary vein (MR), aorta (AR) or hepatic vein (TR)	• Qualitative, affected by filing pressures, AF	• None

From Otto, CM: Textbook of clinical echocardiography, ed 6, Philadelphia, 2018, Elsevier.

Regurgitant Volume (Fig. 12.3)

▪ Regurgitant volume is the amount of blood that flows backward across the valve, measured in cm³ or mL.
▪ Regurgitant volume can be calculated by subtracting the stroke volume (SV) across a competent valve (forward SV) from the antegrade volume flow rate across the regurgitant valve (total SV):

Regurgitant volume = Total SV − Forward SV

(12.3)

▪ Total SV also can be calculated by 2D or 3D echocardiographic measurement of LV SV.

Key Points

□ Transvalvular volume flow rate calculations are based on diameter measurements (using a circular cross-sectional area [CSA]) and the velocity-time integral (VTI) of flow at that site:

SV = CSA × VTI = π ( D/2 ) 2 × VTI

(12.4)

□ Small errors in diameter measurement lead to large errors in calculated SV.
□ The largest source of error is ensuring that diameter is measured at the same level as the VTI recording; this is particularly problematic for transmitral volume flow.
Fig. 12.3 Volume flow at two sites.In this patient with aortic regurgitation, regurgitant volume is calculated as the difference between total stroke volume (SV) across the aortic valve and forward SV across the mitral valve. The diameter (D, left) and velocity-time integral (VTI) (right) for transaortic (top) and transmitral (bottom) flow are shown. Transaortic (total) stroke volume (TSV) is LVOT cross-sectional area (CSA = πr² = 3.14[2 cm/2]² = 3.14 cm²) times the VTI (TSV = 3.14 cm² × 32 cm = 100 mL). Transmitral (forward) stroke volume (FSV) is π(2.8 cm /2)² × 13.2 cm = 81 mL. Then regurgitant volume (RVol) is TSV − FSV or 100 mL − 81 mL = 19 mL. Regurgitant fraction is 19 mL / 100 mL × 100% = 19%. These findings suggest mild regurgitation. Ao, Aorta; LVOT, left ventricular outflow tract; VTI, velocity-time integral.
□ When both aortic and mitral valves are regurgitant, pulmonic valve flow rate can be used for forward SV.
□ 2D LV volumes provide total SV when image planes and endocardial definition are adequate, but volumes may be underestimated if apical views are foreshortened.

Regurgitant Orifice Area

▪ Conceptually, the regurgitant orifice area (ROA) is the size of the defect in the closed valve that allows valve regurgitation.
▪ The actual anatomy of the regurgitant orifice may be complex, sometimes with multiple sites of backflow across the valve.
▪ The continuity equation applies to both antegrade and retrograde flow across a valve.
▪ Thus, ROA can be calculated from regurgitant volume (RVol) and the VTI of the regurgitant jet (RJ) as:

ROA ( cm 3 ) = RVol / VTI RJ

(12.5)

Key Points

□ ROA can be calculated using regurgitant volume calculated by any method.
□ The continuous-wave (CW) recording of the regurgitant jet is used to trace the VTI (Fig. 12.4) to go with the regurgitant volume calculation from Fig. 12.3.
□ Instantaneous ROA also can be estimated using the PISA approach by dividing the PISA instantaneous volume flow rate by the maximum regurgitant jet velocity:

ROA ( cm 3 ) = PISA ( cm 3 /s ) /V RJ ( cm/s )

(12.6)

□ The PISA-estimated ROA reflects the instantaneous ROA only; thus, it is most useful for regurgitation that occurs equally throughout the flow period.
Fig. 12.4 Regurgitant orifice area (ROA) calculation.The velocity-time integral (VTI) of aortic regurgitant flow in the same patient shown in Fig. 12.3 is used to calculate ROA as the RVol/VTI = 18 cm³ /181 cm = 0.1 cm², consistent with mild regurgitation.
□ In clinical practice, ROA should be calculated by more than one method, if possible, to ensure validity.

Distal Flow Reversals

▪ The direction of blood flow distal to a regurgitant valve is reversed from normal when regurgitation is severe.
- ○ With severe mitral regurgitation, there is systolic flow reversal in the pulmonary veins, but this finding is not specific unless the rhythm is normal sinus.
- ○ With severe aortic regurgitation, there is holodiastolic flow reversal in the aorta (Fig. 12.5).
- ○ With severe tricuspid regurgitation, there is systolic flow reversal in the hepatic veins (Fig. 12.6), but this finding is not specific unless the rhythm is normal sinus.
▪ This qualitative indicator is integrated with other findings in classifying overall regurgitant severity.

Key Points

□ These findings are more specific when flow reversal is more distal (e.g., abdominal compared with thoracic aorta for aortic regurgitation) and more severe (e.g., reversed versus blunted pulmonary vein systolic flow in mitral regurgitation).
□ Normal atrial filling during ventricular systole (atrial diastole) depends on normal atrial contraction timing and force. Thus, flow reversal is sometimes seen even when regurgitation is not severe.
□ Causes of false-positive systolic flow reversal include atrial fibrillation or ventricular pacing, resulting in systolic reversal in hepatic and pulmonary veins even when regurgitation is not severe.
□ Diastolic flow reversal in the descending aorta also is seen with a patent ductus arteriosus.
Fig. 12.5 Holodiastolic flow reversal in the descending thoracic aorta.In this patient with moderate to severe aortic regurgitation (AR), a suprasternal notch window was used to record pulsed Doppler flow in the descending thoracic aorta. Holodiastolic flow reversal (arrows) also may be seen with other causes of diastolic flow exiting the proximal aorta, including a patent ductus arteriosus or a large arteriovenous fistula in an upper extremity.
□ Flow reversal is best detected with low wall filter settings, gain reduced to avoid channel cross-talk, and with the scale adjusted to the velocity range of interest.
□ Normal patterns of flow sometimes are mistaken for flow reversal.
- □ In the descending aorta, early diastolic flow reversal is normal.
- □ In the hepatic veins, the atrial reversal can be prominent and may appear to extend into early systole.

Continuous-Wave Doppler Signal (Fig. 12.7)

▪ The shape of the CW Doppler signal reflects the instantaneous pressure differences between the two chambers.
▪ The density of the CW Doppler signal, relative to antegrade flow, reflects the volume of regurgitant flow.

Key Points

□ The diastolic deceleration slope (or pressure half-time) of the aortic regurgitant signal is steeper (shorter) with more severe aortic regurgitation.
□ A late systolic decline in velocity with mitral regurgitation reflects a rise in LA pressure, suggestive of a v-wave.
□ Care is needed to ensure the Doppler recording is made with the ultrasound beam parallel to the direction of the regurgitant jet at the vena contracta.
□ Optimal CW recordings of the regurgitant jets show a smooth velocity curve with a dense signal along the outer edge of the spectral signal.
Fig. 12.6 Hepatic vein systolic flow reversal.Color Doppler imaging in a 4-chamber view (left) shows a large jet of tricuspid regurgitation (TR) with a wide vena contracta width (about 8 mm). The hepatic vein flow signal, recorded from the subcostal window in the central hepatic vein (right), shows flow toward the transducer in systole (arrows), also called systolic flow reversal, consistent with severe tricuspid regurgitation.
Fig. 12.7 Regurgitation hemodynamics.The shape of the CW Doppler velocity curve reflects the instantaneous pressure differences between the aorta and LV in diastole, with the relationship between LV and aortic pressures (top) and Doppler velocities (bottom) shown for chronic (green) and acute (blue) aortic regurgitation (AR). Ao, Aorta.
From Otto, CM: Textbook of clinical echocardiography, ed 6, Philadelphia, 2018, Elsevier.
□ Recordings are enhanced using gray-scale spectral analysis with the velocity scale adjusted to the range of interest, the wall filters increased to improve the signal-to-noise ratio, and gains lowered to avoid overestimation of velocities.

Aortic Regurgitation

Step-by-Step Approach

Step 1: Determine the Etiology of Regurgitation

▪ Aortic regurgitation is due either to disease of the valve leaflets or abnormalities of the aortic root (Fig. 12.8).
▪ Primary causes of aortic leaflet dysfunction include bicuspid valve, rheumatic disease, endocarditis, calcific disease, and some systemic diseases.
▪ Aortic root enlargement resulting in aortic regurgitation may be due to Marfan syndrome, familial aortic aneurysm, hypertension, or aortic dissection.

Key Points

□ Long- and short-axis images of the aortic valve allow identification of a bicuspid aortic valve (two leaflets in systole), rheumatic disease (commissural fusion), vegetations, and calcific changes (Fig. 12.9).
□ Leaflet perforation or fenestration cannot be visualized but is inferred from the location of the regurgitant jet orifice identified by color Doppler.
□ When aortic regurgitation is more than mild, Doppler flow in the aorta should be measured at several sites as detailed in Chapter 16. The transducer is moved cephalad to visualize the ascending aorta.
□ Marfan syndrome is characterized by loss of the normal acute angle at the sinotubular junction.
□ Systemic inflammatory diseases associated with aortic regurgitation cause dilation of the aorta and thickening of the posterior aortic root extending onto the base of the anterior mitral leaflet.

Fig. 12.10 Aortic regurgitation vena contracta.Examples of measuring vena contracta width with a centrally (left) and eccentrically (right) directed jet of aortic regurgitation. Vena contracta width in aortic regurgitation is best recorded in the parasternal long-axis view using zoom mode to focus on the aortic valve. The narrowest width of the regurgitant jet is measured, ideally with the proximal flow acceleration and distal jet expansion regions seen. Vena contracta width is measured perpendicular to the jet direction; with an eccentrically directed jet, this measurement is not perpendicular to the LV outflow tract. Ao, Aorta.

Step 2: Determine the Severity of Regurgitation

▪ Regurgitant severity is evaluated using a stepwise approach with integration of several types of data.
▪ In addition to Doppler measures of regurgitant severity, the cause of regurgitation, and LV size and systolic function are important parameters in clinical decision making.

Step 2A: Measurement of Vena Contracta Width Is the Initial Step in Evaluation of Aortic Regurgitation (Fig. 12.10)

Key Points

□ With aortic regurgitation vena contracta usually is best measured in the parasternal long-axis view on transthoracic echocardiography (TTE) or the long-axis view at about 120° rotation on transesophageal echocardiography (TEE).
□ Vena contracta is measured as the smallest width of the jet, taking care with eccentric jets to avoid an oblique diameter measurement.
□ A vena contracta width less than 0.3 cm indicates mild regurgitation; a vena contracta width greater than 0.6 cm indicates severe regurgitation.
□ Further evaluation is needed when vena contracta is 0.3 to 0.6 cm, when images of the vena contracta are suboptimal, or when further quantitation is needed for clinical decision making.

Step 2B: Evaluation of Diastolic Flow Reversal in the Descending Aorta Is a Simple, Reliable Approach to Evaluation of Aortic Regurgitant Severity

Key Points

□ Holodiastolic flow reversal in the proximal abdominal aorta is highly specific for severe aortic regurgitation (Fig. 12.11).
Fig. 12.12 CW Doppler evaluation of aortic regurgitation.The CW Doppler signal provides information on (1) the velocity of antegrade flow (v) reflecting both the volume of flow and coexisting valve stenosis, (2) the relative density of the regurgitant signal compared with the density of antegrade flow, and (3) the time course of the velocity signal. In this example, the diastolic slope is 2.4 m/s², with a pressure half-time of 528 ms, and the signal is only slightly less dense than antegrade flow; both these features are consistent with moderate regurgitation. The systolic velocity indicates concurrent aortic stenosis.
□ Holodiastolic flow reversal in the descending thoracic aorta is seen in some patients with moderate aortic regurgitation as well as those with severe aortic regurgitation.
□ Early diastolic flow reversal in the descending aorta is normal and should not be mistaken for aortic regurgitation.
□ If holodiastolic aortic flow reversal is seen, but there is no color Doppler evidence of severe aortic regurgitation, evaluate for a patent ductus arteriosus, which also causes aortic diastolic flow reversal due to flow from the aorta into the pulmonary artery.

Step 2C: CW Doppler Evaluation of Aortic Regurgitation Is a Standard Part of the Evaluation

Key Points

□ Aortic regurgitation usually is best recorded from an apical approach using CW Doppler, because this window allows parallel alignment between the ultrasound beam and regurgitant jet.
□ In cases with an eccentric posteriorly directed aortic regurgitant jet, the best intercept angle may be obtained from the parasternal window.
□ On TEE, a transgastric apical view may allow recording of the aortic regurgitant jet, but it may not be possible to obtain a parallel intercept angle using TEE.
□ The density of the velocity signal compared with the density of the antegrade signal provides a qualitative measure of regurgitant severity (Fig. 12.12).
□ In general, a steep diastolic deceleration slope (pressure half-time <200 ms) is consistent with severe regurgitation, whereas a flat slope (>500 ms) indicates mild regurgitation. However, some patients with compensated severe regurgitation have a long pressure half-time.
□ Pressure half-time is measured using the same approach as measurement of pressure half-time in mitral stenosis (see Chapter 11).

Step 2D: When Further Quantitation Is Needed, Regurgitant Volume and Orifice Area Can Be Calculated

Key Points

□ The most common approach is to calculate total stroke volume across the aortic valve and then subtract forward stroke volume (calculated across the mitral or pulmonic valve) to determine regurgitant volume.
□ Regugitant orifice area is calculated by dividing regurgitant volume by the VTI of the CW aortic regurgitation velocity curve.
□ The PISA is often difficult to visualize with aortic regurgitation.

Methods to calculate regurgitant volume based on antegrade and retrograde flow in the descending aorta have been described but are not routinely used.

Step 3: Evaluate Antegrade Aortic Flow and Stenosis

▪ Many patients with aortic regurgitation also have some degree of aortic stenosis.
▪ However, antegrade aortic velocity is increased in patients with severe regurgitation because of the increased antegrade volume flow rate across the aortic valve in systole.
▪ Thus, in addition to velocity and mean pressure gradient, aortic valve area should be calculated using the continuity equation as described in Chapter 11.

Step 4: Evaluate the Consequences of Chronic LV Pressure and Volume Overload

▪ The LV dilates in response to the chronic load imposed by aortic regurgitation with the extent of LV dilation reflecting the severity of regurgitation (Fig. 12.13).
▪ Some patients develop irreversible LV dysfunction in the absence of symptoms so that the most important parameters to measure on echocardiography in patients with chronic severe aortic regurgitation are LV size and ejection fraction.

Only gold members can continue reading. Log In or Register to continue

Stay updated, free articles. Join our Telegram channel

Tags: Echocardiography Review Guide

Apr 23, 2020 | Posted by admin in CARDIOLOGY | Comments Off

Key Points

Key Points

Key Points

Key Points

Key Points

Step 2A: Measurement of Vena Contracta Width Is the Initial Step in Evaluation of Aortic Regurgitation (Fig. 12.10)

Key Points

Step 2B: Evaluation of Diastolic Flow Reversal in the Descending Aorta Is a Simple, Reliable Approach to Evaluation of Aortic Regurgitant Severity

Key Points

Step 2C: CW Doppler Evaluation of Aortic Regurgitation Is a Standard Part of the Evaluation

Key Points

Step 2D: When Further Quantitation Is Needed, Regurgitant Volume and Orifice Area Can Be Calculated

Key Points

Related

Stay updated, free articles. Join our Telegram channel

Thoracic Key

Fastest Thoracic Insight Engine

Valvular Regurgitation

Valvular Regurgitation

Basic Principles

Etiology and Severity of Valve Regurgitation

Vena Contracta (Fig. 12.1)

Key Points

Proximal Isovelocity Surface Area

Regurgitant Volume (Fig. 12.3)

Key Points

Regurgitant Orifice Area

Distal Flow Reversals

Continuous-Wave Doppler Signal (Fig. 12.7)

Key Points

Aortic Regurgitation

Step-by-Step Approach

Step 1: Determine the Etiology of Regurgitation

Step 2: Determine the Severity of Regurgitation

Step 3: Evaluate Antegrade Aortic Flow and Stenosis

Step 4: Evaluate the Consequences of Chronic LV Pressure and Volume Overload

Full access? Get Clinical Tree

Thoracic Key

Fastest Thoracic Insight Engine

Valvular Regurgitation

Basic Principles

Etiology and Severity of Valve Regurgitation

Key Points

Vena Contracta (Fig. 12.1)

Key Points

Proximal Isovelocity Surface Area

Key Points

Regurgitant Volume (Fig. 12.3)

Key Points

Regurgitant Orifice Area

Key Points

Distal Flow Reversals

Key Points

Continuous-Wave Doppler Signal (Fig. 12.7)

Key Points

Aortic Regurgitation

Step-by-Step Approach

Step 1: Determine the Etiology of Regurgitation

Key Points

Step 2: Determine the Severity of Regurgitation

Step 2A: Measurement of Vena Contracta Width Is the Initial Step in Evaluation of Aortic Regurgitation (Fig. 12.10)

Key Points

Step 2B: Evaluation of Diastolic Flow Reversal in the Descending Aorta Is a Simple, Reliable Approach to Evaluation of Aortic Regurgitant Severity

Key Points

Step 2C: CW Doppler Evaluation of Aortic Regurgitation Is a Standard Part of the Evaluation

Key Points

Step 2D: When Further Quantitation Is Needed, Regurgitant Volume and Orifice Area Can Be Calculated

Key Points

Step 3: Evaluate Antegrade Aortic Flow and Stenosis

Step 4: Evaluate the Consequences of Chronic LV Pressure and Volume Overload

Share this:

Related

Related posts:

Stay updated, free articles. Join our Telegram channel

Full access? Get Clinical Tree