1. High frequency ultrasound = 2.0 - 7.5 MHz
A. Adults = 2.0 - 2.5 MHz
B. Pediatric = 3.0 - 5.0 MHz
C. TEE = 3.5 - 7.5 MHz
D. M-mode "ice pick view"
E. 2D sector scanning
F. Doppler effect
G. Color flow imaging
2. Standard Transducer Positions
3. Doppler Effect
A. Sound frequency increases as sound source moves toward observer; frequency decreases as source moves away.
B. Ultrasound of known frequency is transmitted to heart or blood vessel.
C. Moving RBC's reflect ultrasound waves at altered frequency depending on direction RBC's are moving.
D. Frequency shift is used to estimate blood flow velocity.
4. Color Flow Imaging
A. Doppler flow velocity sampled at multiple sites (gates)
Frequency shift converted to color scheme
1) Blood flow toward transducer = RED
2) Blood flow away = BLUE
3) Turbulence (multiple directions) = GREEN
4) High frequency = WRAP AROUND OR ALIASING
5. Hemodynamic Assessment by Doppler
A. Doppler shift measures blood flow velocity
Flow velocity converted to pressure gradient by Bernoulli equation
1) DP = 4 x (V2)2
Sum of flow velocity during ejection period = time velocity integral (TVI)
1) Used with cross sectional area to calculate flow
1) Continuity equation
2) Pressure half-time
E. Flow velocity across a regurgitant valve is related to intracardiac pressure
6. Typical 2D ECHO Patterns
Ensure optimal result of reconstructive cardiac surgery
1) Cardiac valve
2) Congenital defect repair
Minimize CV complications during operation
1) Air embolism
2) Cardiac wall motion (value controversial)
C. Trouble-shooting the hemodynamically unstable patient