Principles of echo Flashcards
What is the relationship between velocity, frequency and wavelength
c= λ f
what is the velocity in air, tissue and blood
330 m/sec, 1540 m/sec, and 1570 m/sec
In what frequency range does diagnostic US operate?
2 - 10 MHz (cw human hearing (16 Hz - 16 KHz)
What is the relationship between frequency, image quality and penetration?
Higher frequency results in a better image but less penetration
What is the Bernouilli equation?
∆P=4 × V^2
What is the maximum velocity of PW?
1.5 - 2.0 m/sec
What is the Nyquist limit?
The limit to the maximum velocity that we can record with PW doppler
What is the Nyquist limit equal to?
1/2 of pulse repetition frequency (i.e. sampling frequency)
How to improve M-mode resolution?
Decrease the scanner width
What is the normal E wave velocity of the MV?
Usually < 1.0 m/sec
What is the normal doppler velocity across the AV?
0.9 - 1.7 m/sec
What is the normal velocity across the TV?
1.7 - 2.3 m/sec
What views and modes do you use to measure size of LV?
1) M-Mode in short axis view (can also you PS-LAX)
2) 2D 4 chamber view or short axis view
What is the normal systolic and diastolic measurements of LV?
1) LVd: 43 +/- 7 mm
2) LVs: 28 +/- 6 mm
What are the normal diameters for the aortic annulus, sinus, STJ and Asc aorta? What view do you use on TTE & TEE?
1) Annulus <25 mm
2) Sinus <40 mm
3) STJ <30 mm
4) Asc aorta <35 mm
TTE: PS LAX
TEE: ME AV LAX (120)
What is the normal LV wall thickness?
< 12 mm
What is the DDx for LVH?
HTN, Outflow obstruction (AS, HOCM), infiltration (amyloid, sarcoid, fabry’s), metabolic (Cushing’s), renal disase, athlete’s heart, obesity & congenital
What is the calculation for SV? How do you obtain measurements?
SV: CSA x VTI
1) Measure LVOT in systole just below aortic valve on LAX
2) PW just below aortic valve in LVOT
Write the continuity equation
CSA (AV) x VTI (AV) = CSA (LVOT) x VTI (LVOT)
What is the normal RV wall thickness?
< 5 mm
What is normal TAPSE?
20 - 25mm. Impaired systolic motion if < 10 mm
Differentiate RV pressure and volume overload on 2D echo.
Both result in a D-shaped septum (paradoxical motion) at different parts of the cardiac cycle:
1) Diastolic -> volume overload of RV
2) Systolic -> pressure overload of RV
What is the DDx for RV dysfunction & dilatation?
1) Volume overload (TR, acute overload, IAH)
2) Primary cardiac problems
- RV ischemia / infarction
- CM (dilated, septic, myocarditis etc)
3) Increased afterload (PH, ASD, VSD, RVOT obstruction)
How do you measure TAPSE?
Use M-mode across TV annulus and measure excursion
DDx of LAE?
1) HTN
2) MV disease (MR, MS)
3) AV disease (AoS, AI)
4) AF
5) CAD
6) CM (DCM, HCM)
What are the two methods that you can measure LA size? What are the normal sizes?
1) AV SAX, M mode at end systolie (<50mm)
2) apical 4 chamber (Area <= 20 mm2)
How do you classify LAE using area measure?
Normal <=20 mm2
Mild 20 - 30
Mod 30 - 40
severe >40
What are the septal dimension cutoffs for LVH?
- Normal is <= 10 mm.
- Mild 11 - 13
- Moderate 14 - 16
- Severe >=17
What is a sigmoid septum? What are the associations? What problems may it cause?
it is a regional problem near LVOT (usually less than 3 cm in length). May lead to SAM. Associated with HTN and LVH
How do you quantify LV mass?
1) Measure length of LV in 4ch view at end diastole and measure from apical endocardium to plane of mitral annulus
2) Measure epicardial diameter and endocardial diameter at end-diastole (cut across papillary muscles)
What are the echo features of HTN?
- LAE
- RVH
- Diastolic dysfunction
- Dilated aorta
