ECHOCARDIOGRAPHY

Presented by ; Dr.Manoj ChandelModerated by; Dr.Yashwant

• Definition• Properties of ultrasound• Principles of image optimization• Doppler shifts• TTE• TEE; PROCEDURE,INDICATIONS,

APPLICATIONS,CONTRAINDICATIONS,COMPLICATIONS,ADVANTAGES

ECHO• Also known as cardiac ultrasound

• Uses sound waves to create pictures of heart.It uses standard ultrasound tech to image 2D slices of heart.The latest ultrasound sys. 3D real time imaging

• The test gives information about size and shape of heart and how well heart chambers and valves are working

• The test also identify areas of heart ms that are not contracting normally due to poor blood flow or injury from previous heart attack

• Helps in calculation of C.O as well as ejection fraction,cardiac dimensions

• A type of echo called doppler ultrasound shows how well blood flows through the chambers and valves of heart

• Echo can detect possible blood clots inside the heart,fluid build up in the pericardium and problems with the aorta

• Echo was the 1st appl of i.v contrast enhanced ultrasound

PROPERTIES OF USG• USG machine generates an imperceptible vibration

within a transducer(device that converts energy from one form into other) that when put next to tissue surfaces, vibrates the surrounding tissue( musle , blood, fat or bone)

• During vibration particles within the tissue compress and then spread apart. This dual process is called compression and rarefaction

• The sequence of compression and rarefaction is described by sine waves and is characterised

• In terms of wavelength,frequency,amplitude and propagation vel.

• Wavelength: distance between 2 peaks of sine waves

• Frequency:no.of cycles in 1second

• Amplitude:measure of tissue compression.It represents loudness of USG wave in dB

• Propagation vel.;describes speed of USG wave travelling through tissue.In blood it is 1500m/s

• Propagation vel=wavelength x frequency

• Transducers ,typically made of quartz or titanate ceramic use crystals that exhibit piezoelectric effect

• With electricity,crystal vibrates and emits USG.The reverse also holds i.e when USG wave strikes a piezoelectric crystal and make it vibrate,the crystal generates electricity.Thus the same crystal can serve as emitter and receiver of USG

• ECHO uses ultrasound waves with frequency 2.5-7.5 million cycles/sec. Slower the Freq,greater the depth of penetration and faster the freq,greater the resolution

• Freq>7.5 Hz are not used as they produce wavelength too short for adequate penetration into tissue

BASIC PRINCIPLES OF IMAGE OPTIMIZATION

• In ECHO,the crystals emits very short pulses of ultrasound(0.5-3micro sec)and receive reflected USG for 250-500 micro sec.

• The pulse repitition frequency(PRF)is the no.of pulses that leave and return the transducer in 1 sec

• As image depth is increased,the time required to reach the target depth and return increases and PRF decreases

• PRF is described in Hz.,it is audible and ranges 1-10 kHz

• Early echo displays used this principle to map out depth of structures within heart. The 1st echo motion studies were 1-D views of cardiac st. produced by single crystal transducers with the results traced on moving photosensitive paper

• Today it is used to view rapidly moving st. such as valve leaflets as it can produce upto 1800 images/sec

• However it reveals only a small portion of heart at one time

• To generate 2D images ultrasound machines were configured to sequentially redirect the beam over an area of interest

• Although 2D tech produce only 30 images/sec,it provides enormous adv. in recognising anatomic and pathologic landmarks

• Matrix array transducers solved the image acquisition problem.They contain over 3000 imaging elements and electronically rotate 2D usg beam 180 degree in millisec. To acquire the requisite 2D image in a fraction of time

DOPPLER EFFECT

• Defined as the apparent change in the freq. of waves(sound or light) when the source and observer are in motion relative to each other,with the freq. increasing when source and observer approach each other and decreasing when they move apart

• When applied to echo,it provides a significant enhancement to 2D imaging

• With doppler, blood flow vel. can be measured as blood flows through structures inside heart.The USG that bounces off moving RBCs is reflected back to transducer at a slightly different freq. than that emitted from transducer

• The shift in freq allows the USG machine to estimate blood flow vel. and direction of flow

• Doppler shifts are presented in 3 ways

• 1.PWD• 2.CWD• 3.CFD• With PWD,a small sampling

vol(cursor)is placed in an area of interest within 2D image. Transducer generates a pulse of USG and then switches to the receive mode and awaits the arrival of reflected portion of USG pulse

• Ultrasound machine then measures freq. shift(Doppler shift)

• Limitation: too slow to capture the vel. of fast moving blood cells(aliasing)

• CWD: uses 2 separate transducers,one to continuously emit USG and one to receive it. However infinite pulse repition rate allows insufficient time for 1st pulse to return to transducer before next is emitted

• and so ultrasound machine cannot precisely define the location of moving blood cells

• CFD: based on PWD and uses multiple sample vol.along a scan line

• A color code is used to depict flow toward(red) and away(blue) from the transducer. Lighter and darker shades of red and blue denote relatively faster and slower vel.

• TISSUE DOPPLER: new use of PWD tech to measure myocardial vel. Instead of blood flow vel.

• During LV contraction,mitral annulus descends towards the apex of heart.Tissue doppler imaging measures vel. of this descent(Sm) and (Sm)correlates with traditional measures of LV fun.

• Sm decreases in myocardial ischemia• 4 chamber c.s view is best for measuring Sm

TRANSTHORACIC ECHO

• A standard echo is called TTE.• In this case,the echo transducer or probe is

placed on the chest wall and images are taken through the chest wall

• Non invasive,highly accurate and quick assessment of overall health of heart

• Accuracy reduced by obesity,copd,chest wall deformities

• Bubble contrast TTE involves the injection of agitated saline into a vein followed by echo study.The bubbles are initially detected in RA and RV. IF bubbles appear in left heart, this indicates shunt PFO,ASD,VSD,AV malformation

TEE

• Recommended if regular or transthoracic echo is unclear or when a much clearer picture of certain areas of heart is needed

• PROCEDURE;• Patient is anaesthetised,trachea

intubated,contents of stomach are suctioned• Gentle massage of left upper quadrant of abd.

during suction removes air which can otherwise degrade imaging

• Patient neck extended and well lubricated TEE probe introduced into midline of hypopharynx with transducer side facing anteriorly.

• Laryngoscope is used to lift larynx anteriorly and probe is placed into oesophagus

• During insertion or withdrawl of transducer ,the controls of gastroscope must be in neutral or relaxed position to allow the transducer to follow the natural course ,minimising injury.

• TEE provides extremly valuable information about cardiac anatomy and function during surgery

• 2D,multiplane TEE can detect regional and global ventricular abnormalities,chamber dimensions,valvular anatomy and presence of intracardiac air

• It can also be helpful in confirming cannulation of coronary sinus for cardioplegia

• Multiple views can be taken from upper and mid oesophagus and transgastric positions. Two most commonly used views for monitoring during cardiac surgery are 4 chamber view and transgastric view (short axis)

• The advent of live 3D echo offers great promise for better visualisation of complex anatomic features,assessment of valvular fun and assessment of regional/global fun.

Indications of Perioperative TEE

• Category 1:supported by strongest evidence or expert opinion;TEE is frequently useful in improving clinical outcome

• Intraoperative evaluation of acute,persistent and life threatening hemodynamic disturbances in which ventricular function and its determinants are uncertain and have not responded to treatment

• I/O use in valve repair• I/O use in CHD surgery requiring CPB • I/O use in repair of HOCM

• I/O use in endocarditis • Preoperative use in unstable patients with

suspected thoracic aortic aneurysms,dissection or disruption who need to be evaluated quickly

• I/o assessment of aortic valve function during repair of aortic dissections with +ve aortic valve involvement

• I/O evaluation of pericardial window procedures

• Category2;supported by weaker evidence;TEE may be useful in improving clinical outcome

• Use in ICU for unstable patients with unexplained hemodynamic disturbances,suspected valve disease or thromboembolic problems(if other tests have not confirmed the diagnoses)

INDICATIONS OF TEE

• I/O assessment of valve replacement,repair of cardiac aneurysm,removal of cardiac tumors,aortic atheromatous disease or other sources of aortic emboli,pericardectomy,pericardial effusions or evaluation of pericardial surg.,anastomotic sites during heart and lung transplantation

• i/o detection of foreign bodies,air emboli

• i/o use for suspected cardiac trauma,intracardiac thrombectomy or pul.embolectomy

• Monitoring placement and fun. Of assist devices

• Category 3: little current scientific or expert support;TEE is infrequently useful in improving outcome

• i/o use ;:during cardiomyopathies other than HOCM,for uncomplicated pericarditis,endocarditis

• i/o evaluation of myocardial perfusion,coronary artery anatomy,graft patency,pleuropulmonary diseases,repair of thoracic aortic injuries

• i/o monitoring emboli during orthopaedic proc.,monitoring placement of intraaortic balloon pump,automatic implantable cardiac defibrillators or pul. Artery cathetors

APPLICATIONS OF ECHO

• Assessment of ventricular fun.;

• Assessed by global systolic fun.,determined by• 1. Ejection fraction and LV end diastolic vol.• 2.,Diastolic fun.(looking for abn. Relaxation

and restrictive distolic patterns by checking mitral flow vel.)and

• 3. Regional systolic fun.

• 4.Wall motion and thickening abnormalities• Regional wall abnormalities following

myocardial ischemia often appear before ecg changes

• Classified into 3 categories• 1.hypokinesis(reduced wall motion)• 2.akinesis(no wall motion)• 3.dyskinesis(paradoxical wall motion)

• Normal LVEF is 55 to 70%, It decreases in weakness of heart ms(dilated cardiomyopathy), heart attack, valvular ds.

• LV diastolic fun.: • Stage 1: impaired(slow) early LV relaxation.

Patient is asymptomatic with normal filling P. Deceleration time>240sec

• Stage 2: mod. Impaired early LV relaxation with decreased LV compliance

• Deceleration time=160-240 sec• Effects of slow early LV relaxation on end

diastolic filling are opposed by elevated LA pressure and mitral flow vel. return to normal(pseudonormalisation)

• Symp.; exertional dyspnoea• Stage 3: restricted filling pattern• Severe decrease in LV compliance and slow

• early LV relaxation• Filling pressure markedly increased• Deceleration time<160 sec• Symptoms: dyspnoea with min. exertion

APPLICATIONS OF ECHO

• 2.Assessing valvular fun.;

• Valvular morphology can be assessed by multiplane TEE.Pressure gradients,stenotic valve area,severity of stenosis and severity of valvular regurgition can be assessed by Doppler echo and color flow imaging

• Colours are usually adjusted so that flow towards the probe is red and flow in the opposite direction is blue

• TEE can also detect Prosthetic valve dysfun. Such as obst,regurgition and endocarditis

• TEE images in the upper mid esophagus at 40 to 60 degree and 110 to 130 degree are most useful for examing aortic valve and ascending aorta

• Doppler flow across AV must be measured looking up from TG view

APPLICATIONS OF ECHO

• Mitral valve is examined from ME position in 0 degree and 150 degree view.TEE is an invaluable aid in MV repair surg

• 3.EXAMINATION OF RESIDUAL AIR Air is introduced into heart during all open heart

procedures.Residual amounts of air often remains even after best manaeuvers

TEE is very helpful in detecting residual air so that additonal surgical manaeuvers can be undertaken

to help avoid cerebral or coronary embolism4.ASSESSMENT OF OTHER CARDIAC

ABNORMALITIESTEE can also detect CHD like

PFO,ASD,VSD,Pericardial diseases like P.temponade and constrictive pericarditis,cardiac tumors

Doppler color flow imaging helps delineate abn. Intracardiac blood flows and shunts

• TEE is used to assess the amount of myomectomy in patients of HOCM

• Upper,mid and LE views arw helpful in diagnosing aortic ds.(aortic dissection,aneurysm,atheroma)

• DETECTION OF MYOCARDIAL ISCHEMIA• Within seconds after onset of myocardial

ischemia,affected segments of heart cease contracting normally

• In patients undergoing CVS surg,new i/o SWMA is diagnostic of myocardial ischemia

• ST changes may not occur earliar but SWMA helps in detecting such changes

• Detection rate of SWMA is more than double that of ECG

• Not all SWMA are indicative of ischemia,Myocarditis,MI,Myocardial stunning also cause SWMA

• LV wall thickness <0.6- Old infarction. If inotropic stimulation improves SWMA– Stunning is likely.A sudden severe decrease in SWMA– Myocardial ischemia

TEE IN NON CARDIAC SURG. AND CRITICAL CARE

• TEE has a vital role in determining the etiology of the instability and in guiding vol. resuscitation during hemodynamic instability and massive blood loss

• Hypotension has only 2 possible causes; Inadequate C.O or inappropriately low systemic vascular resistance

• TEE is useful in its d/d: During severe hypotension,qualitative TEE estimates ventricular filling and fun. And serve as practical guide for administeration of fluids,inotropes and vasopressors

• In severe LV failure,ventricular filling(assessed by end diastolic area)is increased and ejection is decreased,whereas in inappropriately low systemic vascular resistance ventricular filling is usually normal or low and ejection is increased

• Hypovolemia is easily recognised as decrease in ventricular filling and increase in ejection

VALVULAR DISEASES

• AORTIC STENOSIS• Degree of AS is appreciated easily in ME AV SAX

cross section(25-45degree with image depth 10-12cm)where extent of leaflet opening can be estimated visually or measured directly by planimetry

• Severe stenosis is characterised by marked thickening of leaflets and severely reduced leaflet motion(valve opening area<1sq.cm)

AORTIC REGURGITATIONDegree of AR is best appreciated in ME AV LAX

cross section(110-130 degree).With color doppler positioned over the leaflets and

outflow tract,AR is recognised as a color jet emnating from the valve during diastole

MILD AR: diastolic color jet <2mm at its origin in the valve,that occupies <1/3rd of c.s area of LV outflow tract and extends min(1-2cm)intoLV

• MOD. AR:• DCJ 3-5mm,occupying <2/3rd of c.s area of

LVOT and extending 3-5cm into LV• SEVERE AR: DCJ >5mm,occupying entire LVOT

and extending well into LV

• MITRAL STENOSIS;• Presense and severity of MS is

seen in ME 4chamber(0degree with image depth 10-12cm) 2 chamber(90degree with image depth 14-16cm)or LAX c.s(135degree)

• 2D imaging reveals thickened leaflets that dome towards LV and open poorly

• Color doppler reveals laminar flow acceleration into stenotic orifice and turbulent

Normal color doppler aliasing

• Jet emerging into ventricle• PWD and CWD show

increased peak and mean vel. Mathematical calculations from these traces such as pressure half time,are the most precise methods to assess severity of MS and formulas for these are built into the software of each usg

• Severe MS causes marked LA enlargement and

• LA spontaneous contrast i.e swirling,smokelike appearance of 1-2mm densities not attributable to exogenously administered contrast agents but to aggregation of red cells in areas of low flow

• Whenever LA enlargement and spontaneos contrast are noted,THROMBUS in the LA should be suspected

• MITRAL REGURGITATION• Severity is evaluated from same c.s as for M.S• MILD MR: systolic color

jet<2mm,occupies<25%of LA c.s area and extends<1/2 the distance to post.wall of LA

• MOD.MR; SCJ 3-5mm,occupies<50%of LA c.s area and extends 50-90%of distance to post.wall of LA

• SEVERE MR:• SCJ>5mm,occupies most

of LA and extending into pul.vein and LA

• Eccentrically directed jets of MR that hug the wall of LA are a/w more severe valvular regurgitation than their c.s area might suggest

Contraindications of TEE

• Absolute C/A• 1. previous oesophagectomy• 2.severe oesophageal obst.• 3.Oesophageal perforation• 4.ongoing oesophageal haemorrhage• 5.recent upper GI surg• 6.Esophageal

diverticulum,varices,scleroderma,stricture

• Relative c/a • Atlantoaxial joint ds.• Mediastinal irradiation• Unexplained swallowing difficulties• Hiatal hernia

COMPLICATIONS

• Odynophagia• Upper GI haemorrhage• Oesophageal perforation• Dental injury• ETT malposition

ADVANTAGES OF TEE OVER TTE

• CLEAR IMAGES • Heart rests directly upon oesophagus leaving

only few mm that the usg beam has to travel. This reduces the weakening of usg signal,generating a stronger return signal,ultimately enhancing image and doppler quality

• In TTE usg must traverse skin,fat,ribs and lungs

• All these st. along with increased distance the beam must travel,weaken the usg signal thus degrading the image and doppler quality

• In PAEDIATRIC cases TTE has a high degree of sensitivity for detection of supportive evidence of endocarditis and TEE should be reserved for patients with a poor transthoracic window

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