Reference Values

 

 

  • Normal Dimensions
  • Common Equations
  • Scanning Protocols
  • Diastolic Parameters
  • Diastolic Dysfunction
  • RA Pressure Estimator
  • Aortic Stenosis
  • Aortic Regurgitation
  • Mitral Stenosis
  • Mitral Regurgitation
  • Pulmonic Stenosis

 

Normal Dimensions:

Ranges for normal dimensions of common structures are delineated in the table below. Note that though M-mode has long been used for measurement of LV dimensions, 2-D measurements are likely more reliable and are being used with increasing frequency as the standard measurements at many institutions.

LV Diastolic Dimension: 

3.7-5.5 cm

LV Systolic Dimension:

2.0-4.0 cm

Interventricular septum* (Diastole): 

0.6-1.1 cm

   LV Posterior Wall* (Diastole): 

0.6-1.1 cm

LVOT diameter (Systole):   

1.8-2.2 cm

Aortic Root** (Diastole):

2.0-3.7 cm

Left Atrium (Systole):

2.0-4.0 cm

Left Atrial Area (4 chamber):

<20 cm2

Left Atrial Volume/m2 BSA:

16-28 ml

RV Diastolic Dimension:

0.9-2.5 cm

*These measurements are used to determine LV hypertrophy. In general <1.1cm is normal, 1.1-.1.3 is mild left ventricular hypertrophy, 1.4-1.6 is moderate hypertrophy and >1.7cm is severe hypertrophy. There is some variation by gender. Hypertrophy of course can be assessed using many other measurements including LV mass.

**The aortic root measurements should be corrected for body surface area. Hence a root size of 3.8cm in a tall individual may be normal but a 3.6cm root may be enlarged in a very small individual.

 

 

1. Modified Bernoulli Equation

The Bernoulli equation is used to describe the relationship between velocity across an orifice such as a valve and the pressure gradient across the orifice.

Pressure gradient = 4V12-4V02

Here V0 is the flow velocity proximal to the valve and V1 is the peak velocity through the valve. In most situations, V1>>>V0 and if V0 is <1.0 m/s, this term can be ignored and the modified Bernoulli equation can be used:

Pressure gradient = 4V12

2. Continuity Equation

The continuity equation is most commonly employed to calculate the aortic valve area in aortic stenosis. However, theoretically it can be used to calculate any stenotic valve area. The continuity equation is based on the principle of conservation of mass - i.e. that flow proximal to an orifice must equal flow at the orifice in the absence of a shunt. Note that in echocardiography, we calculate flow by multiplying area by velocity time integral through that area. For the aortic valve:

Area (LVOT) x VTI (LVOT) = Area (AV) x VTI (AV)

Area (AV) = Area (LVOT) x VTI(LVOT) / VTI (AV)

Area (AV) = 0.785 x LVOT Diameter Squared x VTI(LVOT) / VTI (AV)

3. Gorlin Equation

The Gorlin Equation is the "gold standard" for invasive assessment of aortic and mitral valve areas with cardiac catheterization. The complete Gorlin formula for aortic stenosis is:

Valve area (cm2) =                                        Cardiac Output (ml/min)                                                 
                           Heart Rate (beats/min) * Systolic Ejection Period (s) * 44.3 * square root(mean gradient)

 


However, the Hakki modification of the Gorlin formula allows for a rough and ready assessment of aortic valve area during a procedure. It is based on the observation that at most heart rates the product of HR x SEP x 44.3 is close to 1000. Thus, the equation becomes:

Aortic Valve area (cm2) ~ Cardiac Output (L/min)
                                    square root (mean gradient) 

4. Proximal Isovelocity Surface Area (PISA)

PISA is used to most commonly used to calculate the regurgitant orifice area with regurgitant valvular lesions, typically mitral regurgitation. PISA takes advantage of flow convergence at an orifice with multiple hemispheres of color flow of equal velocity (isovelocity)

ERO = [2*Pi*(PISA radius)2 x aliasing velocity)/peak MR velocity

5. Mitral Valve Area by Pressure Half Time

MVA (cm2) = 220/pressure half time OR

MVA (cm2) = 750/deceleration time


  • Standard Transthoracic Protocol
  • Limited Follow Up Transthoracic
  • Screening Questions for TEE
  • Standard Transesophageal Protocol
  •  

Protocol for Transthoracic Echocardiographic Study

2 beat clips – default to 2 seconds for poor ECG tracing or tachycardia

Parasternal long-axis

Maximum depth – examine images posterior to left ventricle Change depth 2D view parasternal to minimal depth to include posterior wall of LA/LV
M-mode aorta and left atrium – measurements
LV at the level of the mitral valve chords
If M-mode measurements are inaccurate – 2D measurements
Color flow aortic valve
Color flow mitral valve
High parasternal view – ascending aorta

Pulmonary valve

Long axis 2D
Color Doppler
Spectral pulse Doppler above and below valve

RV inflow

2D
Color flow Doppler
Spectral pulse wave
Continuous wave Doppler

Short axis -  Aortic Valve Level

Pulmonic valve:
2D
Color flow Doppler
Pulse wave Doppler above and below valve
Continuous wave Doppler if necessary
Examine pulmonary artery branches if possible (color)

Aortic valve:
2D
Coronaries if possible
Color flow Doppler

Tricuspid valve:
2D
Pulse wave leaflet tips
Color flow Doppler
Continuous Wave

Apical 4-Chamber

2D Overview for wall motion
Mitral valve:
Zoom mitral valve
Color flow Doppler MV inflow and then all LA
Adjust color baseline for PISA if necessary
Spectral Doppler pulse wave mitral valve leaflet tips
Left atrium (if necessary)
Pulmonary venous inflow
Tricuspid valve:
2 dimensional
Color flow Doppler
Spectral pulse wave at tricuspid valve leaflet tips
Continuous wave
Interatrial septum 2D – ADDITIONAL OFF AXIS VIEW IF SUSPICIOUS
Color flow Doppler
Tissue Doppler septal and lateral
TAPSE – TV annular displacement – M-mode cursor through TV annulus

Apical 5-Chamber View

2D Overview AV and LVOT
Color flow Doppler LVOT
Pulse wave Doppler examination of left ventricular outflow track pulse down septum if necessary
Continuous wave spectral Doppler not necessary if valve opening normally – any abnormality; pulse wave Doppler above and below valve
Continuous wave Doppler across AV if necessary

Apical 2-Chamber View

Overview for wall motion
Color flow mitral valve
Pulse wave mitral valve leaflet tips

Apical Long Axis

2D Overview for wall motion
Mitral valve:
Color flow Doppler mitral valve
Pulse wave mitral valve at leaflet tips
Aortic valve:
Color flow Doppler aortic valve
Continuous wave if necessary
LVOT:
Color flow Doppler LVOT
Pulse wave Doppler LVOT

Subcostal 4-Chamber View

2D Overview for wall motion
Interatrial septum – color flow (and pulse if necessary)
Tricuspid valve color flow Doppler
Continuous wave if necessary
Short axis aortic valve /pulmonary artery (Doppler if necessary)
Short axis left ventricle
IVC with inspiration
Hepatic vein pulse wave Doppler
Abdominal aorta 2D
Pulse and color Doppler

Suprasternal Notch

2D ascending aorta, transverse arch, descending aorta
Pulse wave descending thoracic aorta (continuous wave if necessary)
AS cases must include Doppler of the valve from the suprasternal notch, right sternal edge and PEDHOFF probe at 3 sites.

 

Protocol for 2nd Follow-up Transthoracic Echocardiographic Study

Sonographer Algorithm: 

1. Has the patient had 2 TTE in the last 4 days – yes? Go on to #2
2. Look up old report - no significant abnormalities? If none go on to #3, if yes check with attending
3. Is the indication for post ablation or same indication as previous study? Yes? Go on the #4
4. Is the patient in the MICU or SICU – Yes: check with attending if follow-up protocol is acceptable. No: tech may proceed with follow-up protocol as below:

2 beat clips – default to 2 seconds for poor ECG tracing or tachycardia

Parasternal long-axis                

Maximal depth - Check for left pleural effusion
Change depth to normal 2D view to assess pericardium

Parasternal short-axis view                

3 levels of LV

Apical 4-chamber view                

2D overview to see endocardium
Change depth to assess LV
Sweeps (25 mm speed) at MV tips and TV tips
Color MV
Color TV with CW if possible

Subcostal view                

Check 4 chamber for effusion
IAS with color ? Shunt
IVC collapse

IF THERE IS A SIGNIFICANT EFFUSION OR SIGNIFICANT RESPIRATORY VARIATION ON MV AND TV THEN DO SWEEPS IN APICAL 5 FOR AV AND PSAX FOR PV

  1. Screening Questions For TEE

    1. Does food ever got stuck going down?

    2. Do you ever have pain when swallowing?

    3. Have you ever had surgery on your esophagus (the tube between your mouth and stomach)?

    4. Have you ever been told you have a narrowing or varices of your esophagus or had a dilatation?

    5. Have you ever had an ulcer or surgery on your stomach?

    6. Have you have had bleeding from your stomach?

    7. Do you have any loose teeth?

    8. Patients must be informed that they can eat absolutely nothing (including water and meds) for 6 hours before the procedure.

Standard Trans-esophageal Protocol

In all patients, the views necessary to answer the clinical question should be obtained first. (Example: the left atrium and left atrial appendage should be imaged initial in the pre-cardioversion study). It is recommended that the study include the following views, unless a previous study or patient condition make this inadvisable.

TEE Study:

1. Four chamber view - overview

2. Mitral valve

0 ° Four chamber view – 2D examine all planes
Color flow Doppler examine all planes
Pulse wave with sample volume at leaflet tips
Zoom as indicated
30° (as above)
60°(as above)
90 °   (as above)  
120° (as above)

3. Left atrium

Appendage at 30° increments, 0-135  - image left atrial appendage in 2D
Pulse wave Doppler in best parallel plane
Definity for significant difficulty in distinguishing artifact vs thrombus
Pulmonary veins – pulsed wave Doppler left and right veins (MR cases)
Posterior left atrium

4. Interatrial septum

Image from 0° and then omniplane exam especially at 90°
Color flow Doppler imaging in both planes
saline contrast injection with Valsalva if
a) Ordered
b) Indicated from clinical history
c) PFO detected or suspected
d) Interatrial septum aneurysm or hypermobility      
Bicaval view

5. Aortic valve

Image at 0 ° 2D and color
Image at 30° to 60° (obtain short axis) – 2D and color
Coronary arteries
120-130° 2D and color of valve, rotate through valve, LVOT and ascending aorta

6. Pulmonic valve

Image at 90-130° 2D and color
Return to 0° attempt to visualize pulmonary valves and left and right main pulmonary arteries

7. Tricuspid Valve

0° four chamber view, 2D and color
130° attempt continuous wave

8. Four chamber view

Wall motion – angle to image RV

9. Transgastric view

0° 2D short axis of MV, advance to papillary muscle level and apex if possible
90° 2D long axis of LV and RV

10. Aorta – Thoracic and Abdominal aorta

Withdraw the probe while imaging descending aorta and arch, short and long axis

 

Normal Diastolic Parameters

A variety of Doppler parameters can be used to assess LV diastolic function and filling pressures. The simplest and most commonly employed is the PW Doppler of mitral inflow at the tip of the mitral leaflets. In the normal heart, this produces an E or early wave and an A wave which occurs with atrial contraction. Tissue Doppler, which measures the lower velocity motion of the myocardial tissue in diastole at the mitral annulus also provides an insight into myocardial relaxation. Lastly, PW Doppler in the pulmonary veins can also be used for assessment of LV filling. The normal ranges for all these parameters are listed in the table below:

E Wave Velocity (m/s)
0.6-1.2
A Wave Velocity (m/s)
0.4-0.8
E/A Ratio
1-1.5
E Wave Decel Time (ms)
150-200
IVRT (ms)
60-100
E' Septal (cm/s)
8-10
E' Lateral (cm/s)
10-12
PV S/D Ratio
>1
PV Ar Velocity (cm/s)
<35
PV a duration - MV A duration (ms)
<20

 

 

 

 

 

Diastolic Dysfunction

The variety of Doppler parameters can be used in concert to quantify the degree of diastolic dysfunction and elevation in left sided filling pressures. The Grade I, there is impaired relaxation with normal LA and LV pressures. This is a common finding in the elderly and may be a normal finding in patients >65 years of age. Typically, E<A and the E decel time and IVRT are prolonged. Mitral TDI is low or low normal. In Grade Ib, there is impaired relaxation with elevated LVEDP. Here E<A, but S>>D and Ar velocity is >35 cm/s. As diastolic dysfunction worsens, left atrial pressure rises such that a greater proportion of filling occurs in early diastole. This results initially in pseudonormalization with E>A, but here S<D, and mitral TDI velocities are low and E/E' ratio will be high. As diastolic function worsens, left atrial pressure rises further, E wave velocity rises and E' velocity falls, as does E decel time and IVRT leading to a restrictive filling pattern.

Grade LAP E:A E Decel IVRT S:D Ar Vel Mitral TDI E/E'
0 - Normal
Normal
1.0-1.5
150-240
60-100
S>D
<35 cm/s
Normal
<8
I - Impaired Relaxation (IR)
Normal
0.4-0.9
>240
>100
S>D
<35 cm/s
Normal/Low
<8
Ib - IR w/high LVEDP
Normal
0.4-0.9
>240
60-100
S>>D
>35 cm/s
Low
<8
II = Pseudonormal
High
1.5-2.0
150-200
<90
S<D
>35 cm/s
Low
>15
III - Restrictive
High
>2.0
<150
<90
S<<D
>35 cm/s
Low
>15

 

Estimating RA Pressure From IVC Dimensions

Note that RA pressure can be estimated by examining the diameter of the IVC and the degree to which the IVC collapses with an inspiratory 'sniff' maneuver. Note that though this is useful as a guide, there is a fair degree of error in appropriately viewing the IVC and a measure of subjectivity in determining the degree of IVC collapse.

RA Pressure mmHg (Range) IVC Diameter Inspiratory Collapse
3 (0-5) less than or equal to 2.1cm complete collapse
3 (0-5) less than or equal to 2.1cm >50% collapse
8 (5-10) less than or equal to 2.1cm <50% collapse
8 (5-10) greater than 2.1 cm >50% collapse
15 (10-20) greater than 2.1 cm <50% collapse
15 (10-20) greater than 2.1 cm no collapse

* note that young athletes can have IVC diameters >2.1 normally and that vented patients may have IVCs that do not collapse normally therefore this algorithm may not be accurate in those individuals.

Chart adapted from Rudski et. al. J Am Soc Echocardiogr 2010;23:685-713

Aortic Stenosis

A variety of methods are commonly employed to assess the degree of aortic stenosis including valve area by planimetry, peak and mean transvalvular gradients and valve area calculated by the continuity equation. In patients with LV dysfunction, the AVA by continuity equation can be particularly helpful as patients with low gradients may have severe aortic stenosis due to severe LV dysfunction. Aortic stenosis is typically quantified as mild, moderate, severe and 'critical' based on the variables in the table below:

AS Grading
Mean Gradient (mm Hg)
Peak Velocity (m/s)
AVA (cm2)
Normal
<10
<2.6
>2.5
Mild
10-25
2.6-2.9
1.5-2.5
Moderate
20-45
3.0-4.0
1.0-1.5
Severe
>45
>4.0
0.7-1.0
Critical
>50
>4.0
<0.7

 

Source: ASE Guidelines for Clinical Practice.

 

Aortic Regurgitation

There are also numerous ways to measure severity of aortic regurgitation including the width of the vena contracta jet in the parasternal long axis, the pressure half time method as well as more quantitative measures such as the regurgitant volume or fraction. Abnormal Values these parameters are shown below

 

AR grading
Central Jet Width*
Vena Contracta Width*
Pressure Half Time
Regurgitant volume (per beat)
Regurgitant Fraction
EROA
Mild
<25% of LVOT width
<0.3cm
>500 ms
<30 ml
<30%
<0.1cm^2
Moderate
25-65% of LVOT width
0.3-0.6 cm
500 to 200 ms
30-59 ml
30-49%
0.1-0.3cm^2
Severe
>65% of LVOT width
>0.6 cm
<200 ms
>60 ml
>50%
>0.3 cm^2

*This is assessed in the parasternal long axis view

EROA - effective regurgitant orifice area

Source: ASE Guidelines for Clinical Practice.

Mitral Stenosis

There are multiple methods for calculating a mitral valve area for assessment of mitral stenosis. These include the pressure half time method, the continuity equation, the PISA method and even planimetry by TTE or TEE. Important echo parameters that support these valve area calculations, according to the American Society of Echocardiography the mean gradient and pulmonary artery pressure. Thus mitral stenosis is graded as follows:

MS grading
Valve Area
Mean Gradient*
Pulmonary Artery Pressure (mmHg)*
Mild
>1.5 cm^2
<5 mmHg
<30 mmHg
Moderate
1.0-1.5 cm^2
5-10 mmHg
30-50 mmHg
Severe
<1.0 cm^2
>10 mmHg
>50 mmHg

 

* Supportive findings. The valve area is the primary determinant of severity of stenosis.

Source: ASE Guidelines for Clinical Practice.

Mitral Regurgitation

There are numerous methods for assessing mitral regurgitation quantitatively (i.e. beyond just the estimate with color Doppler) which include vena contracta width, use of PISA calculations and continuity equation to assess regurgitant fraction and volume as well as supportive qualitative signs. Values are shown in the table below.

MR Grading
Vena Contracta Width*
Jet Area**
CW density and shape
Regurgitant Volume
Regurgitant Fraction
EROA
Mild
<0.3cm
<20% of LA area
soft density, parabolic
<30 ml
30%
<0.2 cm^2
Moderate
0.3-0.6cm
20-40% of LA area
intermediate density, parabolic
30 to 59 ml
30-49%
0.2-0.39 cm^2
Severe
>0.6cm
>40% of LA area
dense jet, triangular shaped
>60 ml
>50%
0.40 cm^2 or greater

* This is measured in the parasternal long axis view.

** This is using appropriate color Doppler settings.

EROA - effective regurgitant orifice area

Source: ASE Guidelines for Clinical Practice.

Pulmonic Stenosis

Pulmonic stenosis is typically a result of congenital heart disease, either as an isolated defect with a bicuspid or dysplastic valve or as part of a syndrome (e.g. Tetralogy of Fallot, Noonan's syndrome). Pure calcific PS with an otherwise normal valve is uncommon even in elderly patients. The degree of PS is typically quantitated based on 2 D morphology (subjective) and peak transvalvular gradient (more objective)

PS Grade
Peak Gradient
Mild
5-25 mmHg
Moderate
25-49 mmHg
Severe
>50 mmHg