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 MR velocity aliases since velocity> 1 m/sec -Mild to moderate MR

Continuous Wave Doppler Toward Transducer Time Away from Transducer Velocity cm/sec

Some Uses of Transthoracic Echocardiography 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 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 pv2 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. RA RV TR

Continuity Equation A1V1=A2V2 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

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 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. TTE 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