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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Agitated saline test in echo:
- How can you determine whether the shunt is intracardiac vs pulmonary?
Intracardiac shunt will have bubbles in left side within 1-2 cardiac cycles
Pulmonary shunt wil have bubbles in 3-5 cardiac cycles
How can you use the vena contracta of an AR jet to judge degree of AR?
Ratio of width of the AR jet at the vena contracta to the aortic valve
Where can you look to judge the degree of AR by diastolic flow reversal on echo?
Abdominal aorta
How do you calculate the myocardial performance index (MPI)?
Time spent in isovolumic contraction + isovolumic relaxation / ejection time
Echo findings of constrictive pericarditis
1) MV inflow - E/A ratio and respiratory variation
2) Mitral valve DTI
3) Hepatic venous doppler
1) E/A ratio usually increases. Respiratory variation of > 25% in MV
2) Mitral valve DTI usually normal
3) Increased flow reversal during atrial systole during expiration (unclear why to me)
In what disease do you find the goose neck deformity on echo and why?
Complete AVSD - Aorta is sprung forward due to loss of AV septum
What is the most diagnostic echo finding for pericardial effusion with tamponade?
Diastolic right ventricular wall collapse
(MV inflow variation has to be >25%)
What is a load independent measurement of LV performance that can be calculated via echo?
Stress velocity index
How do you grade regurgitant fraction on echo and MRI?
<20% mild
20-40% moderate
>40% severe
What is the Coanda effect?
When a jet has a tendancy to become entrained along the wall of the heart- such as supravalvar aortic stenosis (creates discrepant blood pressures in R/L arm)
What velocity do you obtain for surgical purposes in a fixed obstruction such as aortic stenosis?
Mean velocity
What velocity do you obtain for surgical purposes in a dynamic obstruction such as HCM?
Peak instantaneous velocity
What are the most common complications of pediatric TEE?
Airway compromise (per the test book)
Mouth laceration (per the presentation)
Describe spin echo MRI:
- Color of blood
- Purpose
Blood is black
Good for tissue quantification of the heart
Describe CINE MRI
- Color of blood
- Purpose
Blood is white
Good for determining flow and velocities, seeing regurgitation, etc
Which weighted sequence is best for detecting edema of the heart wall? T1 or T2 weighted?
T2
What are two situations where ECG gating is necessary for CT
Coronary arteries
Aortic valve (not aorta tho)
How do you calculate the fractional shortening (FS%) and what is the normal range
LVEDD-LVESD/ LVEDD x 100
28%-28%
How do you calculate the ejection fraction (equation wise)?
LVEDV-LVESV/ LVEDV x 100
How do you calculat the velocity of circumferencial fiber shortening (vcf)? Why is this helpful
Fractional shortening / ejection time
Helpful because its preload independent
What is a normal value for longitudinal strain?
<-18%
What equation can be used to assess RV function?
Fractional area change = RVEDA- RVESA / RVEDA x 100
Normal - 35-40%
What is TAPSE?
A method for assessing RV function by looking at how far the tricuspid valve moves during the cardiac cycle
Grading pulmonary stenosis on echo:
- By RV pressure
- By gradient
RV pressure: If > 2/3, considered severe
Gradient:
Mild: Peak gradient is less than 36 mm Hg
Moderate: Peak gradient is between 36 and 64 mm Hg
