Ultrasound of Heart SDL Flashcards
how is the patient prepared for ultrasound
clip over apical beat and apply water & gel
what is the patient position
right then left lateral recumbency
why is the echocradiogram done in lateral recumbency
- the lateral recumbency, the lower lung partially collapses under the weight of the heart and mediastinum –> this process in the lower lung is known as hydrostatic congestion and the upper most lung hyperinflates to compensate
- also the heart is fixed at the base but free at the apex so in lateral recumbency the cardiac apex falls towards the lower thoracic wall and pushes the lung out of the way
bigger area which is free from air filled lung
what transducers are best suited for imaging the heart
phased array due to small areas of contact with skin
produces a fan shaped image and allows visualization of a large structure like the heart through the small intercostal spaces
what is the B or brightness mode
and why is it used
produces the familiar real time grey scale images that represents a thin slice through the patient and vary the direction of the beam
- allows orientation of heart
- ensure that entire heart is examined systematically and no features missed
- performance of a repeatable exam and performance of standard measurements which are necessary for the comparison of findings to published results
what is the standard right parasternal view obtained
with the beam orientated at right angles to the long axis of the heart and roughly parallel with the intercostal space
what will the chambers of the heart appear
anechoic or black because blood = fluid
what does the muscular wall of the heart appear as
echogenic
what does the pericardium appear as
hyperechoic line around the outside of the heart and produces an acoustic shadow with reverberation artefact due to the air filled lung immediately beyond it
what are 3 standard right parasternal short axis views through the hear
- left ventricle
- mitral valve (fish mouth)
- heart base (aorta, pulmonic trunk and left atrium)
identify the structures on long axis view (standard right parasternal view)
how is the right parasternal long axis of the left ventricle obtained
first obtain the short axis view through the left ventricle and then rotate the transducer through 90° so the beam is orientated parallel to the long axis of the heart and roughly at right angles with intercostal space
what can be seen on the right parasternal long axis view of the left ventricle
can see the left atrium, mitral valve and left ventricles
the interventricular septum is located between the left and right ventrcles
the right side of the heart is still in the near field of image so it may not be weel imaged due to distortion of beam
it is possible to see the right atrium, tricuspid valve and right ventricle
the pericardium appears as hyperechoic line adhered to outside of heart
what are the right parasternal long axis views
- left ventricle and left atrium –> chordae tendinae
- left ventricle and aorta
what is the hyperchoic strands that can be seen running through the mtiral valve in this view
papillary muscles which represent the chordae tendinae that serve to tether the mitral valve leaflets and are therefore normal structures
what are the LPS views
- 4 chamber: left atrium, left ventricle, mitral valve, right atrium, right ventricle and tricuspid valve
- 5 chamber: directing the beam so the aortic outflow tract also appears
in these views blood is flowing either directly up the screen through the mitral valve and tricuspid valves or down the screen through the aortic valve –> useful for doppler
summarize all the views in RPS short axis, RPS long axis, LPS views
- RPS short axis: left ventricle, mitral valve, heart base (aorta, pulmonic trunk and left atrium)
- RPS long axis: left ventricle & left atrium, left ventricle & aorta
- LPS: 4 chamber, 5 chamber
what is M-mode/time-motion mode used for
performed using standard B-mode images
a cursor line is positioned through B-mode image –> displayed against time as a chart across the screen that is updated
can be used with ECG to identify the stage of the cardiac cycle
how is cardiac wall thickness measured
a standard right parasternal short axis through the left ventricle at the level of the papillary muscles immediately below the level of the chordae tendinae
M-mode cursor is positioned so it bisects a symmetrical line through the left ventricle between the papillary muscles
measured at end diastole (onset of QRS complex) and at systole (T wave)
what can the B-mode RPS long axis through LV and LA be used for
to assess
LV lumen diameter
end diastole - MV open/max area
end systole 4
what can also be used to measure LV thickness
M-mode LV function
RPS short axis through LV
what is the shortening fraction and what info does it provide (what would reduction, increase mean)
the measurements of LV lumen diameter and interventricular septum are fed into equation on machine to produce a shortening fraction
provides info regarding the function or contractility of the left ventricular wall
reduction suggests reduced cardiac function and an increase means compensatory hypercontractility (incompetent mitral valve)
what is the normal shortening fraction range in dogs and cats
dogs: 25-45%
cats: 30-55%
how is ejection fraction determined and why is it used
by calculating the ejection fraction
using B mode RPS long axis through the left ventricle and left atrium:
- image is stopped at both end diastole and end systole (using ECG or by determining the point which internal diameter of LV is at max and min)
- cursor drawn round the internal surface of the LV –> calculate the internal area at end diastole and end systole
- comparison of values gives ejection fraction
what is the normal value of ejection fraction
>50%
how is E-point to septal separation (EPSS) calculated and what is normal value
M-mode measurement
using standard B mode RPS short axis view at level of mitral valve (fishmouth view)
-cursor is placed through the mitral valve and the resulting M mode trace demonstrates the movement of the 2 valve leaflets with time as they make M and W shape –> distance between valve and IVS
normal <7mm
what does EPSS value indicate
early indicator of left ventricular volume overload and dilation
how is left atrial size measured
standard B mode RPS short axis image through base of heart
freeze image with aortic valve visible (mercedes benze appearance)
cursor used to directly compare the diameter of left atrium and the aorta at systole
what are the normal ratio values of left atrium and the aorta measurement
dogs: 1:1-1.4
cats: 1:1.2-1.7
what are the M-mode measurements
- wall thickness (LV and interventricular septum)
- shortening fraction (LV function)
- ejection fraction (LV function)
- E-point septal separation (EPSS) (LV dilation)
what are the B-mode measurements
- left atrial enlargement (LA:aorta)
what are the 3 ways doppler assess blood flow
- direction
- velocity (beam parallel with direction movement = most accurate)
- uniformity (laminar vs. turbulent)
what is colourflow doppler and what mode is it
standard B-mode images used to guide doppler “gate” placement:
- LPS 4/5 chamber views (aorta, MV, TV)
- RPS SA heart base view (pulmonic trunk)
what do the colours of the doppler mean
BART
blue = away from transducer (aortic/pulmonic outflow)
red = towards transducer (mitral/tricuspid inflow)
how is the pulmonic outlfow tract best visualized using doppler
using standard RPS short axis view through the base of the heart where normal pulmonic outlfow is also downt the screen, away from the transducer (blue)
how are valvular incompetences identified with doppler
opposite colour of flow in the wrong direction between the normal pulses or inflow or outflow depending on the valve
turbulent flow produces a mulitcoloured appearance (mosaic)
what does colour flow doppler not allow measure of
velocty
how is spectral doppler used
colourflow used to guide placement of spectral doppler cursor box over areas of normal inflow/outflow and over any areas of abnormal flow
activation of pulsed wave produces a trace of blood flow through the box against time
what do mitral/tricuspid flow appear like on spectral doppler pulsed wave
in standard B mode LPS 4 chamber views
- mitral and tricuspid inflow is up the screen towards the transducer –> normal inflow is peaks above the baseline
normal: two peaks during every diastole
first peak (E): or early peak due to passive filling of ventricles from atria and then flow reduces as the valves begins to close
the second peak (A): contraction of atria before the valves close completely at the onset of systole
how are aortic/pulmonic flows assessed using spectral doppler
aortic valve is assessed using standard B-mode LPS 5 chamber view
pulmonic valve: standard B-mode RPS short axis view through the base of the heart
what does normal aortic/pulmonic flow appear on spectral doppler
normal outflow: during systole is a single peak below the baseline with a white outline and black centre –> normal laminar flow (velocity can be measured)
what does regurgitant aortic/pulmonic outlfow appear as on spectral doppler
can be seen during diastole between peaks of normal outflow and is in opposite direction and above baseline (ECG used to identify this)
usually turbulent so incompetence produces an “envelope” on the trace that is filled in with white rather than a black centre and white outline in the normal laminar outflow
what is the Bernoulli equation and what info does it give
velocity = height/depth of peak
p1-p2 = 4V^2
the velocity of regurgitant flow across a valve can be measured
can be used to measure the pressure differences across the valve (can give info if heart is functioning in presence of incompetent valve)
what is continuous wave doppler used for
measure flow in areas that has exceeded the capacity of pulsed wave
when is continuous wave doppler used
in cases with pulmonic and aortic stenosis where the restricted area is present causes a high velocity blood flow past it
ex. this trace shows aortic outflow being measured below the baseline at a speed of more than 4 m/s (normal is 1.2 m/s) –> also regurgitant flow present above the baseline between the peaks of outlfow and both sets of flow have an envelope that is filled in
what is B (brightness) mode RPS and LPS standard views used for (4)
- identify physical changes
- subjectivetly assess the function of heart (although have to be quite marked before this is possible on B-mode images alone)
- objective measurement of cardiac structures such as determining the size of atrium
- guide M-mode/doppler cursor placement
what does the M (motion) mode allow assessment of
objective measurements of cardiac chamber size and left ventricular function
what are the doppler modes and what are they used to measure
- colourflow: info regarding the direction and uniformity of flow but does not allow us to objectively measure flow velocity (large screen areas of flow within the heart and guide placement of spectral doppler gate)
- pulsed wave spectral doppler: objectively measure blood flow within the heart and will identify the regurgitant and turbulent flow (limit to max velocity it can measure)
- continuous wave: used when max velocity is exceeded in pulsed
