ECHO (CARDIAC ULTRASOUND)Echo is something we experience all the time.If we shout into a well, the echo comes back amoment later. The echo occurs because someof the sound waves in our shout reflect off asurface (either the water at the bottom of thewell or the wall on the far side) and travel backto our ears. A similar principle applies incardiac ultrasound.
GENERATION OF AN ULTRASOUND IMAGEEchocardiography (echo orechocardiogram) is a type of ultrasoundtest that uses high-pitched sound waves toproduce an image of the heart.The sound waves are sent through adevice called a transducer and arereflected off the various structures of theheart.These echoes are converted into picturesof the heart that can be seen on a videomonitor.
Transducers, typically made of quartz or titanate ceramic, use crystals that exhibit the piezoelectric effect
PROPERTIES OF ULTRASOUND sequence of compression and rarefaction is described by sine waves characterized in terms of Wavelength distance between two peaks of the sine wave Frequency number of cycles that occur in 1 second Amplitude measure of tissue compression Propagation velocity speed of an ultrasound wave traveling through tissue Echocardiography uses frequencies of 2.5 to 7.5 million cycles/sec (MHz)
PROPERTIES OF ULTRASOUND Image resolution is characterized in terms of Axial resolution(along length) Elevational resolution(thickness of image) Temporal resolution(ability to accurately locate moving structures at a particular instant in time) Lateral resolution(increased frequency-less divergence
PROPERTIES OF ULTRASOUND Attenuation :- a function of tissue absorption , divergence of ultrasound energy as it moves away from the transducer, reflection, and scattering
PROPERTIES OF ULTRASOUND Acoustic impedance :- refers to the resistance that an ultrasound wave meets when traveling though tissue Mismatches in acoustic impedance and attenuation are important to consider in imaging the heart For example, the upper aortic arch is difficult to visualize from the esophagus
PROPERTIES OF ULTRASOUND GAIN -to amplify low amplitude ultrasound waves reflected back to transducer PULSE REPETITION FREQUENCY -no of pulses that leave or are returned back to transducer in a single second -image depth increases PRF decreases
THE MODALITIES OF ECHOThe following modalities of echo are used clinically:1. Conventional echo Motion- mode echo (M-mode echo) Two-Dimensional echo (2-D echo) 3-D ECHO2. Doppler Echo Continuous wave (CW) Doppler Pulsed wave (PW) Doppler Colour flow(CF) DopplerAll modalities follow the same principle of ultrasoundDiffer in how reflected sound waves are collected and analysed
M-MODE ECHOCARDIOGRAPHYAn M- mode echocardiogram isnot a "picture" of the heart, butrather a diagram that shows howthe positions of its structureschange during the course of thecardiac cycle.M-mode recordings permitmeasurement of cardiacdimensions and motion patterns.Also facilitate analysis of timerelationships with otherphysiological variables such asECG, and heart sounds.
TWO-DIMENSIONAL ECHO (2-D ECHO)This technique is used to "see" theactual structures and motion of theheart structures at work.Ultrasound is transmitted alongseveral scan lines(90-120), over awide arc(about 900) and many timesper second.The combination of reflectedultrasound signals builds up an imageon the display screen.A 2-D echo view appears cone-shaped on the monitor.
3-D ECHO The advance from 2D to real-time 3D echocardiography has proved difficult. The time needed to acquire the requisite 2D images, the computing challenge of collating them into 3D images, and the display challenge of depicting 3D images on a 2D video screen all contributed to the difficulty. Matrix-array transducers typically, contain over 3000 imaging elements and electronically rotate the 2D ultrasound beam through 180 degrees in milliseconds to acquire the requisite 2D images in a fraction of the time possible with mechanically rotated multiplane transducers.
DOPPLER ECHOCATDIOGRAPHY DOPPLER SHIFT(CHRISTIAN DOPPLER) The ultrasound that bounces off moving red blood cells is reflected back to the transducer at a slightly different frequency than that emitted from the transducer. The shift in frequency allows the ultrasound machine to estimate blood flow velocity and direction of flow.
DOPPLER ECHOCARDIOGRAPHYDoppler echocardiography is amethod for detecting the directionand velocity of moving blood withinthe heart.Pulsed Wave (PW) useful for lowvelocity flow e.g. MV flowContinuous Wave (CW) useful forhigh velocity flow e.g aortic stenosisColor Flow (CF) Different colors areused to designate the direction ofblood flow. red is flow toward, andblue is flow away from thetransducer with turbulent flow shownas a mosaic pattern.
Doppler Advantages Disadvantages Clinical UsesTechniquePulsed Measures blood Cannot measure To measure bloodwave flow velocities at fast blood flow flow velocities selected areas of velocities through the interest 3-5 mm (>1 m/sec) because pulmonary veins and wide along the of aliasing mitral valve and in ultrasound scan line low-flow areas within the heartContinuous Detects blood flow Cannot identify To measure bloodwave velocities up to location of the flow velocities 7 m/sec (not subject peak velocity through the aorta, to the Nyquist limit) along the aortic valve, stenotic ultrasound scan valve lesions, and line regurgitant valvular jetsColor flow Presents the spatial Like pulsed wave To enhance relationships Doppler, cannot recognition of between structure measure fast blood valvular and blood flow flow velocities abnormalities, aortic because of dissections, and aliasing intracardiac shunts
One limitation of PWD is that it may be too slow to capture the velocity of fast-moving blood cells. This phenomenon is known as aliasing. The limit at which the sampling rate fails to accurately capture the true velocity is called the Nyquist limit Aliasing of PWD occurs at blood flow velocities greater than 0.8 to 1.0 m/sec. Normal flow within the heart may reach 1.4 m/sec and pathologic flow up to 6 m/sec.
REASONS FOR SUCCESS OF TEE1. Close proximity of esophagus to post wall of heart – no intervening structure like bone or lung2. Monitor the heart over time, such as during cardiac surgeries3. Extremely safe & well tolerated so that it can be performed in critically ill patients & very small infants
CATEGORY 1 INDICATIONS FOR TEE Intraoperative evaluation of acute, persistent, and life-threatening hemodynamic disturbances Intraoperative use in valve repair Intraoperative use in congenital heart surgery for most lesions requiring cardiopulmonary bypass Intraoperative use in repair of hypertrophic obstructive cardiomyopathy Intraoperative use for endocarditis when preoperative testing was inadequate or extension of infection to perivalvular tissue is suspected Preoperative use in unstable patients with suspected thoracic aortic aneurysms, dissection, or disruption who need to be evaluated quickly Intraoperative assessment of aortic valve function during repair of aortic dissections with possible aortic valve involvement Intraoperative evaluation of pericardial window procedures Use in the intensive care unit for unstable patients with unexplained hemodynamic disturbances, suspected valve disease
EQUIPMENT DESIGN AND OPERATION A miniaturized echocardiographic transducer (about 40 mm long, 13 mm wide, and 11 mm thick) mounted on the tip of a gastroscope. Transducer is with 64 piezoelectric elements operating at 3.7 to 7.5 MHz
Like standardgastroscopes tworotary knobs controlthe movements
CONT. Relative1. Esophageal diverticulum,2. Varices,3. Fistula, and4. Previous esophageal surgery, history of gastric surgery, mediastinal irradiation, unexplained swallowing difficulties
PATIENT PREPARATION Informed consent Pt. should fast for at least 4 – 6 hrs Thorough history should be taken – any dysphagia i.v. access Pre oxygenation Suction should be available
BASIC TRANSESOPHAGEALEXAMINATION Patient is anesthetized (topically) The contents of the stomach are suctioned Patients neck is then extended and the well-lubricated TEE probe is introduced If the probe does not pass blindly, a laryngoscope can be used
TRANSGASTRICVIEWSMOST IMPORTANTTRANSESOPHAGEAL VIEWSBEST FOR EVALUATING LEFTAND RIGHT VENTRICULARFUNCTIONCOMMONLY EMPLOYED INTRAOPERATIVE TEE TO ASSESSEJECTION FRACTION ANDWALL MOTION POST-OPERATIVELYDEEP TRANSGASTRIC VIEWSARE THE BEST VIEWS TOOBTAIN ACCURATEGRADIENTS ACROSS THEAORTIC VALVE TO ASSESSTHE DEGREE OF AS OR AR
HIGH ESOPHAGEALHIGH ESOPHAGEAL VIEWS AREHELPFUL FOR EVALUATING THEGREAT VESSELS INCLUDINGTHE AORTIC ROOT ANDCORONARY ARTERIES,ASCENDING AORTA AND THEPULMONARY ARTERY. AUSEFULL LANDMARK IS THEMID-ESOPHAGEAL VIEW OF THEAORTIC VALVE IN SHORT AXIS AT40-60 DEGREES. BYWITHDRAWING FROM THELEVEL OF THE AORTIC VALVE,THE ORIGIN OF THE CORONARYARTERIES CAN BE VISUALIZED
TRANSTHORACIC ECHOA standard echocardiogram is also knownas a transthoracic echocardiogram (TTE),or cardiac ultrasound.The subject is asked to lie in the semirecumbent position on his or her left sidewith the head elevated.The left arm is tucked under the head andthe right arm lies along the right side ofthe bodyStandard positions on the chest wall areused for placement of the transducercalled “echo windows”
PARASTERNAL LONG-AXIS VIEW (PLAX)Transducer position: leftsternal edge; 2nd – 4thintercostal spaceMarker dot direction: pointstowards right shoulderMost echo studies begin withthis viewIt sets the stage forsubsequent echo viewsMany structures seen fromthis view
PARASTERNAL SHORT AXIS VIEW (PSAX)Transducer position: left sternaledge; 2nd – 4th intercostal spaceMarker dot direction: pointstowards left shoulder(900clockwise from PLAX view)By tilting transducer on an axisbetween the left hip and rightshoulder, short axis views areobtained at different levels,from the aorta to the LV apex.Many structures seen
PAPILLARY MUSCLE (PM)LEVEL PSAX at the level of the papillary muscles are used usually for the purposes of describing abnormal LV wall motion LV wall thickness can also be assessed
APICAL 4-CHAMBER VIEW (AP4CH)Transducer position:apex of heartMarker dot direction:points towards leftshoulderThe AP5CH view isobtained from thisview by slight anteriorangulation of thetransducer towardsthe chest wall. TheLVOT can then bevisualised
APICAL 2-CHAMBER VIEW (AP2CH)Transducer position: apexof the heartMarker dot direction:points towards left side ofneck (450 anticlockwisefrom AP4CH view)Good for assessment ofLV anterior wallLV inferior wall
SUB–COSTAL 4 CHAMBER VIEW(SC4CH)Transducer position: under thexiphisternumMarker dot position: pointstowards left shoulderThe subject lies supine with headslightly low (no pillow). With feeton the bed, the knees are slightlyelevatedBetter images are obtained withthe abdomen relaxed and duringinspirationInteratrial septum, pericardialeffusion, abdominal aorta are seen
SUPRASTERNAL VIEW Transducer position: suprasternal notch Marker dot direction: points towards left jaw The subject lies supine with the neck hyperextended. The head is rotated slightly towards the left The position of arms or legs and the phase of respiration have no bearing on this echo window Arch of aorta is seen
ASSESSMENT OF HEMODYNAMICS 1.Evaluation of Ventricular Filling -measurement of EDA -LV filling pressure 2.Estimation of Cardiac Output - measuring both the velocity and the cross- sectional area of blood flow at appropriate locations in the heart or great vessels gives stroke volume
CONT. 3.Assessment of Ventricular Systolic FunctionFractional area change (FAC) during systoleis a commonly used measure of global LVfunction. FAC = (EDA - ESA)/EDA
CONT. 4.Assessment of Ventricular Diastolic Function -E/A ratio -E wave (higher-velocity component across mitral valve generated by atrial pressure and ventricular relaxation in early diastole) -A wave(second lower-velocitycomponent generated by atrial contraction in late diastole)
5.DETECTION OF MYOCARDIALISCHEMIA Within seconds after the onset of myocardial ischemia, affected segments of the heart cease contracting normally New intraoperative segmental wall motion abnormalities (SWMAs) diagnostic of myocardial ischemia Not all SWMAs are indicative of myocardial ischemia(myocardial stunning,severe hypovolemia)
6.VALVULAR PATHOLOGIES MS-ME 4 chamber, 2 chamber LAX-in 2 D ECHO appears as thickened dome towards LV-color flow doppler shows turbulent jet flow into LV MR-similar views as for MS
GRADING FOR MITRAL REGURGITATION Jet Width at Jet Area (% LAa) Jet Depth (% LAd) Origin (mm)MILD >2 <25 <50MODERATE 3-5 25-50 50-90SEVERE >5 <50 >100
VALVULAR PATHOLOGIES AS-ME AV SAX shows thickening of aortic leaflets-Deep TG LAX with CWD estimates pressure gradient across the AV AR-ME AV LAX- With color Doppler positioned over the leaflets and outflow tract, aortic regurgitation is recognized as a color jet emanating from the valve during diastole
GRADING FOR AORTIC INSUFFICIENCY Jet Width at Jet Area (% LVOT) Jet Depth into the Origin (mm) LV (cm)MILD <2 <33 1-2MODERATE 3-5 <66 3-5SEVERE >5 100 >5
7. STRESS ECHO New regional wall motion abnormalities, a decline in ejection fraction, and an increase in end-systolic volume with stress are all indicators of myocardial ischemia. Exercise stress testing is usually done with exercise protocols using either upright treadmill or bicycle exercise. Pharmacologic testing can also be performed by infusion of dobutamine to increase myocardial oxygen demand. Dobutamine echocardiography has also been used to assess myocardial viability in patients with poor systolic function and concomitant CAD. It determine the hemodynamic response to stress, In patients with low-output, low-gradient aortic stenosis
UNDERSTANDING ECHO REPORT LEFT VENTRICLE WALLS IVS(d) 0.6-1.1 cm IVS(s) 0.8-2.0 cm PW(d) 0.6-1.1 cm PW(s) 0.8-2.0 cm CHAMBERS LVID(d) 3.7-5.6 cm LVID(s) 1.8-4.2 cm RWT <0.42 cm SYSTOLIC FUNCTION FS 34-44% EF >50% MASS LVMI 50-95 g/m2 women men RANGE MILD MODER SEVER RANGE MILD MODER SEVER ATE E ATE EEF >55 45-54 30-44 <30 >55 45-50 30-44 <30(%)
UNDERSTANDING ECHO REPORT RIGHT VENTRICLE RVD (at base) 2.6-4.3 cm LEFT ATRIUM LAD(anteroposterior) 2.3-3.8 cm LAV ( ml/m2) 16-28 Aortic root dimension (cm) 2.0–3.5 Aortic cusps separation (cm) 1.5–2.6 Pulmonary AA dia 1.5-2.1 cm(mild 2.2-2.5,moderate 2.6-2.9, severe >3 cm) Mitral flow (m/s) 0.6–1.3 Tricuspid flow (m/s) 0.3–0.7 Aorta (m/s) 1.0–1.7 Pulmonary artery (m/s) 0.6–0.9
CONCLUSIONEchocardiography provides a substantialamount of structural and functionalinformation about the heart.Still frames provide anatomical detail.Dynamic images tell us aboutphysiological functionThe quality of an echo is highly operatordependent and proportional toexperience and skill, therefore the valueof information derived depends heavilyon operation and interpretation