Echocardiography Flashcards
echocardiography
real time ultrasonographic imaging of the heart used to localize and diagnose cardiac disease
what is echocardiogram able to do
- diagnose ALL cardiac disease
- estimates chamber size and wall thickness
- estimates cardiac function
- estimates hemodynamic data - CO, pressures
- provides prognostic and treatment information
- identifies RIGHT heart failure + PERICARDIAL disease
can echocardiogram diagnose left heart failure
NO - requires thoracic radiographs
can echocardiogram image the great vessels well
no
what is the best positioning for an echocardiogram
lateral recumbency
R lateral –> view R side of the heart
L lateral –> view L side of the heart
2D echocardiography
real time 2D cross sectional view of single or multiple parts of the heart in their anatomically correct position during multiple cardiac cycles
does 2D echo provide information on blood flow velocity or direction
no - requires doppler
what size should the LA be in comparison to the RA in a R parasternal long axis 4 chamber view
about equal
what size should the LV be in comparison to the RV in a R parasternal long axis 4 chamber view
LV = 3 x RV
M-mode
creates a time-motion graph by correlating change in structure with timing in the cardiac cycle (ECG)
what is M-mode used for
evaluating IVS and LVFW thickness
calculating fractional shortening to estimate systolic function
doppler echo
assesses blood flow at valves, defects +/- vessels
functions of doppler echo
detects direction, velocity, character/quality, and timing of movement
can be used to calculate pressure gradients across valves, shunts, etc
limitations of doppler echo
HIGHLY angle dependent
cursor alignment MUST be within 15-20 degrees of flow/movement
if at too much of an angle –> will underestimate velocity
what kinds of doppler are there
color
spectral (pulsed wave, continuous wave)
tissue
color flow doppler
applies color to shifts in frequency to rapidly detect abnormal flow
BART
- blue = away
- red = toward
what is the velocity of laminar flow
appears as red and blue
100 cm/s (1 m/s)
what is the velocity of abnormal flow
appears as rainbow flow (many different directions and velocities)
> 100 cm/s
spectral doppler
uses a baseline to detect direction, velocity, and timing of blood flow
function of spectral doppler
calculates pressure gradients
direction on spectral doppler
+ is towards the probe
- is away from the probe
velocity on spectral doppler
Y axis of the tracing in m/s or cm/s
timing on spectral doppler
uses ECG to correlate blood flow changes to timing in the cardiac cycle
systolic –> just after QRS
diastolic –> during T to QRS
how to calculate pressure gradient
Bernoulli’s equation
deltaP = 4 x velocity^2
pulse wave spectral doppler
measures velocity and direction of flow at a specific point along the cursor
allows for velocity assessment at a region of interest
when to use pulse wave doppler
low (normal) velocity blood flow within the heart
can only assess velocities <2 m/s
- once over that, cannot determine direction
continuous wave spectral doppler
measures velocity and direction of flow along entire cursor
cannot localize the site of peak velocity
when to use continuous wave doppler
high (abnormal) velocity blood flow within the heart
can assess ANY velocity with accurate direction assessment
LA:Ao ratio
used to measure L atrial size
quantifies atrial enlargement INDEPENDENT of weight
LA diameter / Ao diameter
normal vs enlarged LA:Ao ratio
normal: LA:Ao < 1.6
enlarged: LA:Ao > 1.6
fractional shortening
used to measure left ventricular function
%FS = (LVIDd - LVIDs) / (LVIDd) x 100
what is normal fractional shortening in dogs and cats
dogs: 30-40%
cats: 40-60%
what view is fractional shortening measured in
M-mode right parasternal short axis LV
how to evaluate concentric and eccentric hypertrophy
ventricle diameter and wall thickness in 2D or M mode
what is normal velocity across outflow tracts
<2 m/s
inflow velocity
assesses AV valves during diastole
E wave + A wave on spectral doppler
E wave
early wave
indicates early passive filling of ventricles
A wave
late wave; indicates late active “atrial kick” filling of ventricles
how to assess E and A wave
used to assess diastolic function
E wave should be > A wave in normal animals due to majority of filling coming from passive flow down pressure gradient
what does an E wave < A wave indicate
non compliant ventricles relying on atrial contraction to fill (ex. HCM)
what is the normal velocity across semilunar valves
1 m/s
what is a normal pressure gradient across semilunar valves
delta P = 4 x 1^2 = 4 mmHg
if aortic pressure is 120 mmHg, how much pressure does the LV need to generate to eject blood into aorta
120 + 4 = 124 mmHg
how do you use tricuspid regurgitation velocity (5 m/s) to estimate systolic pulmonary arterial pressure
calculate the pressure gradient across the regurgitant valve:
- dP = 4 x 5^2 = 100 mmHg
calculate the right ventricular systolic pressure if there is NO atrial enlargement (RASP = 5) :
- RVSP = dP + RASP
- RVSP = 100 + 5 = 105 mmHg
if there is NO evidence of pulmonary stenosis on echo, then:
- sPAP = RVSP
- sPAP = 105 mmHg
(normal sPAP = 25 mmHg)
indicates severe pulmonary hypertension
