Download Introduction to echocardiography

Introduction to Echocardiography
Courtesy of Dr. Susan Yeon, M.D., J.D.
Edited by Dr. Joyce Meng M.D.
Ultrasound Imaging
• US beam transmitted into chest with
reflection, scattering, refraction, and attenuation
• Signal is reflected off interfaces
– tissue planes
– blood/tissue borders
• Attenuation of transmitted beam reduces
returning signal to 1/10,000 of original
power
Production of ultrasound
• Piezoelectric crystals
– Transmitter: Emit ultrasound when stimulated by
electric current
– Receiver: Produce electric current when stimulated by
returning ultrasound signal
• Depth information is determined by the time delay
of the returned signal
• Transducer sends out pulses of ultrasound and
“listens” for returning signal
Two-dimensional imaging
• Multiple pulses sent out along adjacent scan
lines
• Sector formed by multiple scan lines
• Process repeated multiple times for “live”
imaging
• Speed of US in tissue and rapid signal
processing allow real time imaging
(30 frames/sec)
Johann Christian Doppler
1803-1853
Doppler effect
• A sound wave reflected from a moving
object changes its frequency proportional to
the velocity of the object
Doppler Effect
Doppler effect used to calculate
velocity of galaxies as well as velocity
of trains
or red blood cells relative to observer
Doppler
• Pulse of ultrasound directed at moving object (blood)
• Frequency shift of returning signal indicates direction and velocity of
object
• Pulsed wave Doppler
– Determine velocity in a small area called sample volume
– Cannot resolve velocities >1m/sec
• Continuous wave Doppler
– Cannot resolve location of velocity along line
– Can resolve any physiologic velocity
• Color Doppler
– Sample a large area and inform us of
• Direction of jet
• Extent of jet
• Limited temporal resolution
Color vs Pulse Wave Doppler
-Mild to moderate MR
MR velocity aliases since
velocity> 1 m/sec
Continuous Wave Doppler
Toward
Transducer
Time
Away from
Transducer
Velocity cm/sec
Some Uses of Transthoracic
Echocardiography
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•
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Evaluation of ventricular structure
and systolic and diastolic function
– Congestive heart failure
– Coronary artery disease
– Cardiomyopathies
Valvular abnormalities
– Prolapse
– Regurgitation
– Stenosis
Masses
– Endocarditis
– Thrombus
– Benign or malignant tumors
• Pericardial disease
• Pulmonary hypertension
• Congenital abnormalities
– Atrial or ventricular septal
defects
– Patent foramen ovale
– Transposition of the great
vessels
The Normal Echocardiogram
Standard Views
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•
•
•
•
•
Parasternal Long Axis
Parasternal Short Axis
Apical 4 Chamber
Apical 2 Chamber
Apical 3 Chamber
Subcostal Long Axis
Standard Echocardiographic Views
Valvular regurgitation
• Color doppler showing
tricuspid and mitral
regurgitation
• Looking at the size, width,
color (therefore the
velocity) and the location
of the jet is one way of
determining the severity
of the regurgitation.
Bernoulli Equation
Daniel Bernoulli
1700-1782
• Change in pressure
across a small orifice is
proportional to the
square of the velocity of
the fluid flowing through
the orifice
• Simplified Equation
pv2
Application of Bernoulli
• Measurement of PA pressure
– Velocity of tricuspid regurgitation jet is proportional
to RV systolic pressure
– Can estimate RA pressure
– PA=RA+4(peak TR velocity)2
– VERY IMPORTANT- off angle
measurements underestimates velocity.
RV
RA
TR
Continuity Equation
• Measure stenotic valve area
• Usually applied to aortic stenosis
• Assumptions
– Fluid is incompressible
– Flow = mean velocity * cross sectional area
– Flow by any cross section in the pipe is the
same F1=F2
A1V1=A2V2
Aortic Stenosis Calculations
Pulsed Wave LVOT
Continuous Wave AV
Again, off-axis measurements will introduce error!!
Aortic Stenosis Calculations
Blood Flow r1
1 m/sec
A1=šr12
If the LVOT radius is 1 cm,
then the AV area is
A1*V1 3.14*1
A2=
= 4 = 0.8cm2
V2
4 m/sec
Transesophageal Echocardiogram
Ultrasound probe in the
esophagus
• Offers superior views of
the posterior structures of
the heart (LA, pulm veins,
mitral valve)
– Decreased distance between
the transducer and the
structures
– No intervening lung,
bones…etc
Disdvantages of TTE vs TEE
• TEE
• TTE
– More invasive
– Maybe less optimal for
anterior structures
– Transducer position
restricted by the esophagus
• Cannot obtain standard
anatomic measurements
(i.e. forshortened)
• Cannot always align the
ultrasound beam parallel
to the flow of interest.
– Image quality often
suboptimal due to
intervening tissue and long
distance between the
transducer and the heart
(especially for posterior
structures)
Complications of TEE
• Fairly safe procedure:
– Risk of esophageal intubation includes dental trauma, esophageal
trauma/perforation, bleeding, aspiration, dislodgement of NG/ET
tube…etc.
– Risk of conscious sedation including hypotension, respiration
depression…etc.
– Complication serious enough to interrupt the procedure in <1%, mortality
rate of fewer than 1 in 10,000 patients.
• Contraindicated mostly due to local esophageal problems:
– Esophageal stricture or malignancy
– Recent esophageal ulcer or hemorrhage
– Zenker’s diverticulum.
• Needs screening endoscpy and/or barium swallow prior to TEE if there
is a history of odynophagia and dysphagia
Stress Echocardiography
• Can be done after exercise testing or dobutamine infusion
• Image acquired shortly after exercise and compared with
baseline to detect newly induced wall motion
abnormalities.
– Have to acquire the image quickly enough
• Overall accuracy- 76% sensitive, 88% specific
• Compare to SPECT MPI, about 10% less sensitive and
10% more specific
• Stress echo is not a full echo! Detail assessment of
valvular function, pulmonary artery pressure…etc. are not
routinely done.
Echo can also evaluate masses and
vegetations