Echocardiography Flashcards
Which frequency probe has the greatest penetrance?
The lower the frequency, the greater the penetrance
(think about it: we only use 12 on little babies bc they are so small and don’t need a ton of penetrance)
What frequency probe has the greatest axial spacial resolution?
The higher the frequency probe
What are three ways to increase the frame rate?
1) narrow the sector width (less info to interpret)
2) Decrease depth (less time needed for info to get back to probe)
3) Reduce number of lines per frame (less time to complete each image)
How does the echo machine extrapolate the velocity of blood flow?
Machine knows frequency shift, which is proportional to velocity. With the frequency shift info, can solve for velocity, provided the angle of interrogation is minimal
What frequency probe has a higher Nyquist limit?
Low frequency
What is the Nyquist limit equation?
Nyquis limit = Pulse repetition rate /2
What is the simplified Bernoulli Equation?
Pressure = 4 v ^2
When can you not use the simplified Bernoulli equation?
When the proximal velocity is > 2 m/s
Need to use Pressure = 4 (v2^2-v1^2)
What equation can be used to estimate an area of a vessel or valve?
The continuity equation:
Area of valve x v1 = area of valve x v2
If you know the area of one valve and the velocities at the two points, can solve for area of valve you don’t know
How does echo and cath differ in their ability to measure a pressure gradient?
Echo measures peak instantenous gradient while cath measures peak to peak gradient
Peak instantaneous gradient tends to overestimate pressure differences
What pharmacologic agent is used in an stress echo?
Dobutamine +/- Atropine
What is an average E:A ratio?
E = 0.6 m/s
A= 0.3 m/s
E/A = 2
How does PW doppler work?
Probe uses one crystal that both emits and receives the sound pulses
Describe how the progression of disease can be seen in the E/A ratio of a mitral inflow pattern
Normal: E/A ratio ~ 2
Grade 1 diastolic dysfunction- Impaired relaxation: E/A ratio is <1 (A > E)
Grade 2 diastolic dysfunction - Pseudonormalization, E/A ratio flips and appears “normal” with E>A
Grade 3 restrictive diastolic dysfunction: E/A ratio is > 2
Mitral annulus velocity appears similarly
Contrast agents in echo:
- What side do they travel to?
- What are they good for?
- What is their acoustic impedance compared to blood?
- How long do they stick around?
1) Left side of the heart
2) Highlighting the endocardium of the left heart
3) Acoustic impedance is greater than blood (ie: more visable)
4) Stick around for 3-5 minutes][=[=
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