Cardiac Imaging Flashcards
Types of non invasive cardiac imaging
Echocardiography
Nuclear imaging
Cardiac MR
CT
What is echocardiography
Ultrasound exam of the heart
Safe powerful painless technique
Practical procedure requiring skill and is operator dependent
Performed at the bed side or in echocardiography labs
Types of echocardiography
Trans thoracic TTE
Probe on the chest wall
trans oesophageal TOE
Swallows probe in oesophagus image the back of the heart
Stress echo trans thoracic at rest and under stress - exercise or adenosine
Standard trans thoracic echo windows
Standard positions on the chest wall allow good penetration of ultrasound Windows include Suprasternal Right para sternal Left para sternal Apical Subcostal
What is TTE limited by
Obesity
Chest wall deformity
Chronic lung disease
TTE techniques
)
M - mode (motion)
-Transmission and reception of echo on a line
-changes in movement observed (valve and ventricular wall motion) and plotted against time
Single ultrasound beam transmitted in one direction - transmission and receptor single line so you can observe changes in motion
Continuous wave Doppler
-severity of stenosis, regurgitation, velocity flow in shunts
Ultrasound beam is directed and received along one line
Can not locate position or velocity
Pulsed wave Doppler
Useful for
Valve flow, diastolic function, stroke volume and cardiac output
Wave is eat and received at a particular point assess flow at the particular point
Colour flow mapping
Multiple direction pulsed wave Doppler which is colour coded
Assessment of regurgitation and shunts
Indication for a TTE
Assessment of anatomy, valve function and ventricular function Suspected endocarditis Suspected myocarditis Pericardial disease and effusion Possible source of emboli Estimation of intracardiac pressures
Why is TOE useful
US probe in oesophagus
Advantage close proximity , no lung obstruction producing a clearer image
Move the probe up and down even into the stomach and change the US beam in relation to the heart
TOE indications
Mitral stenosis, prolapse and regurgitation to determine if the valve is suitable for repair vs replacement Aortic valve disease Prosthetic valves Endocarditis Embolic source Intracardiac masses Congenital heart disease Intraoperative to aid the surgeon
TOE contraindications and complications
Contraindications Dysphagia Oesophageal disease Cervical spine instability Severe pulmonary disease
Complications Trauma - inc perforation Hypoxia Arrhythmia Laryngo/broncho spasm Angina
What does a stress echo do
Assessment of ischaemic heart disease
An alternative to exercise ECG/myocardial perfusion imaging
Echo at rest compared to echo under stress
Exercise
Pharmacological (commonly dobutamine)
Stress echo indications
Ischaemic heart disease
If a patient has a equivocal exercise test are unable to exercise have a resting ECG abnormality so if they were to exercise it would be difficult to see on ECG any change
Localisation of ischaemia
Assessment of viability
LV outflow obstruction
HCM consideration of septal ablation
Complications of stress echo
Sustained arrhythmia
MI
Hypotension
What are the types of nuclear imaging used
Myocardial perfusion imaging
Ventricular function
PET scanning
What is nuclear myocardial perfusion imaging
Tracer used Technetium 99 labelled tracers
Given at rest and under stress
Concentration of the tracer in the myocardium relative to the blood supply
Stress increases flow in normal vessels but not in stenosis vessels
-exercise
-pharmacological stress -adenosine and dobutamine
What are the indications for nuclear myocardial perfusion imaging
-assessment of chest pain where exercise testing is impractical or not possible
-abnormal resting ECG (LBBB, WPW, resting ST depression, paced rhythm)-unable to exercise
Prognosis in ischaemic hear disease
What is nuclear ventricular function
Multi gated acquisition (MUGA)
-planar imaging performed after injection of radiolablled blood cells
Gated scales during myocardial perfusion imaging using Technetium 99 sestamibi
Superseded by echo and CMR usually
What is nuclear PET scanning
Perfusion assessed using water (H2 15O )or ammonia (13NH3)
Cell viability assessed using a glucose analogue FDG labelled with 18F the cells that are alive take up this glucose
Can be used to asses myocardial viability prior to revascularisation
There is restricted availability due to requirement of cyclatron to generate radioactive tracers
What is cardiovascular magnetic resonance imaging (CMR) used for
Determine heartbanatomy Ventricular volumes and mass Function Perfusion Viability Valve assessment Flow measurement Angiography
How is CMR perfusion measured
Heart is imagined
How is CMR viability assessed
Inject gadolinium
Most myocardium after it has been given time to clear will return to black this is normal
If there is a scar there is decreased blood flow to the area so gadolinium lingers
This will be a bright area
Meaning scar
Therefore not viable
How to do a CMR valve assessment /flow
Flow forwards is white
Flow backwards in black
If flow is hindered by a valve defect blood is not flowing where is should this can be detected
Flow
Plot flow Vs Time In the ascending aorta to obtain a graph
The area under the graph is the amount of flow forward and back
The amount back is the regurgitation fraction and the severity of this can be determined from the percentage
How is a cardiac CT used
For calcium scoring in risk assessment
Coronary imaging
How was CT use for heart scans hindered in the past
Hindered by the movement of respiratory motion
But now more slices are taken on a single breath hold
How is cardiac calcium scoring used
See calcium in the vessel in CT imaging
Risk predicted by the amount of calcium in the coronary vessels
Risk assessment score Franium score
Not widely done due to the radiation risk
How is CT coronary imaging done
Image the artistries to see if there is stenosis within.
Lower risks that coronary angiogram
If a stenosis is seen can go on to be further assessed by angiography
Useful to rule out proximal coronary artery in patients enable to exercise or stress testing is unequivocal
