Transcript Magnetic Resonance Imaging in Ischaemic Heart Disease (ASM 2011)

Danny Cho Wai Man,
Rad I (DR), Queen Mary Hospital
April 2011
Outline
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Introduction
Clinical investigations of IHD
MRI in the assessment of IHD
Safety in Cardiac MR examination
Imaging protocol for IHD in QMH
Introduction
 In Hong Kong, heart disease is the
second leading cause of death in 2009
(after cancer)
 More than six thousand and four
hundred people died from heart disease
in 2009
 It accounts for 15% of all death
Introduction
 Diagnosis of IHD requires careful history
taking and physical examination, along
with direct investigation
 Diagnostic imaging plays an important
role in the proper assessment and
management of coronary artery disease
Clinical investigations of IHD
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Electrocardiography (ECG)
Echocardiography
Nuclear medicine
Positron emission tomography (PET)
Computed tomography (CT)
Coronary angiography
Magnetic resonance imaging (MRI)
Electrocardiography(ECG)
 One of the standard investigation performed in
patients with chest pain
 Exercise stress electrocardiography is the most
widely applied test to obtain objective evidence
of myocardial ischaemia and significant
coronary artery disease
Echocardiography
 Provides a good estimate of
ventricular size as well as
regional and generalized left
ventricular wall motion
 Stress echocardiography
either by exercise or by
pharmacological means is
comparable in accuracy to
radionuclide testing for
diagnosis of coronary artery
disease
Radionuclide Imaging
 Provides higher sensitivity
and specificity for the
diagnosis of IHD than
exercise ECG testing
 It can provide functional
or physiological and
prognostic information, is
quantifiable and
reproducible
Positron Emission Tomography
(PET)
 Provides more accurate result
for the detection of CAD
 Provides an estimate of
coronary blood flow and
coronary flow reserve as well
as myocardial viability
 Popularity limited by the high
cost
Computed Tomography (CT)
 CT angiography provides high resolution
imaging of the heart and give good
visualization of the coronary arteries
Coronary Angiography
 Gold standard in the
diagnosis of ischaemic heart
disease
 It has a very good spatial
resolution of 300m
 Ascertains the anatomic
extend and severity of the
atherosclerotic involvement
of the coronary arteries
Magnetic Resonance Imaging
(MRI)
 Global cardiac function and regional
wall motion abnormalities
 Regional perfusion
 Myocardial infarction
 Coronary MRA
Cardiac function & regional
wall motion
 For patients with heart failure or
myocardial infarction due to IHD
 Assessment of cardiac function is
important prior to commencement and
for monitoring of therapy
Cardiac function & regional
wall motion
 Good spatial and temporal resolution
 Allowing imaging of systolic and diastolic
phases of both right and left ventricles
 Cine short-axis images from base to
apex
 Yields reproducible data for myocardial mass
and ventricular size
 Regional wall thickness of ventricle,
valvular motion, and regional wall
motion can be clearly defined
 Good contrast between blood pool and
myocardium
Cardiac function & regional
wall motion
 Commercially available software
yields calculations of stroke volume,
ejection fraction, end-systolic
volume, end-diastolic volume,
myocardial wall thickening within
few minutes
 Advantages of non-invasiveness, no
irradiation, high reproducibility,
and high repeatability of results
make it an ideal tool for serial
measurement and monitoring of
cardiac function
First-pass
Myocardial Perfusion
 For the detection of regional
ischaemia
 Good temporal resolution to image
first-pass of contrast medium
through myocardium
 Adequate contrast between normal
and ischaemic myocardium
 Adequate coverage from apex to
base of the heart (multiple short axis
slices in basal, mid-ventricular, and
apical regions of left ventricle)
First-pass
Myocardial Perfusion
 In view of the auto-regulatory function of
coronary arteriolar beds, stenosed coronary
arteriolar beds will vasodilate to maintain
adequate blood supply to myocardium
 Stenosed coronary arteries usually have normal
myocardial perfusion at rest
 First-pass myocardial perfusion during stress
condition is necessary for demonstration of
perfusion defects
Stress Cardiac MRI Exam.
 Physical stress may not be feasible
within the MRI environment
 Pharmacological stress will be
more easily to implement using
vasodilator e.g. adenosine
 Myocardial blood flow will increase
fourfold to fivefold downstream of
normal coronary arteries, but does
not increase downstream of
stenosed arteries because the
related arteriolar beds have already
vasodilated maximally
Stress Cardiac MRI Exam.
 Myocardium receiving blood
supply from an significantly
stenosed coronary artery will
show hypoperfusion compared
with normal myocardium
 Normally perfused myocardium
shows greater enhancement at a
faster rate than hypoperfused
myocardium
LV
Normal
myocardium
Infarcted or
Ischaemic
myocardium
Adenosine Stress Cardiac MRI
Exam.
 Short half life (<10 secs)
 Better patient tolerence
 Side effects of Adenosine
 Mild decrease in systemic blood pressure
 Mild increase in heart rate
 Increase respiratory rate
 Headache
 Dizziness
 Shortness of breath
 Nausea
 flushing
Contraindications of Adenosine
 Acute Myocardial infarction within few days
 Asthma
 Second- or third-degree atrio-ventricular
block
 Sick sinus syndrome
 Symptomatic bradycardia
Patient Preparation for
Adenosine Stress MRI Exam.
 Refrain from caffeinated food and drink for
24 hours
 Such as coffee, tea, coke and chocolate
 Adenosine antagonist
 Interfere with the ability of Adenosine to dilate
arteries
 False negative examination result
Adenosine Stress Cardiac MRI
Exam.
 Adenosine at 140g/kg/min intravenously for
4 mins
 Gadolinium-DTPA (0.05 mmol/kg) is rapidly
infused (4ml/sec)
 First-pass imaging is performed using
gradient echo pulse sequence on multiple
short axis slices (basal, middle, and apex) of
the left ventricle during a breath hold
Adenosine Stress Cardiac MRI
Exam.
 Normal myocardium shows a
“blush” of bright signal
throughout the cardiac cycle
 Ischaemic or infarcted
myocardium will show a
persistent dark signal, either
subendocardial or transmural in
location
 The perfusion defect shall follow
the supply territory of the
coronary arteries
Myocardial Viability
 Differentiation between viable
and non-viable myocardium is
important
 Transmural extent
 Viable myocardium may benefit
from revascularization and
resume normal cardiac function
 Function cannot be restored to
nonviable tissue
Myocardial Infarction
 Post-gadolinium myocardial delay enhancement
technique
 Areas of infarct or scar have increased volume of
distribution of gadolinium as compared to normal
myocardium
 There is more efficient egress of gadolinium from normal
myocardium compared to infarcted tissue
 Hyperenhancement of infarcted myocardium 10-20mins
after contrast administration
Ischaemia vs Infarction
 Ischaemic and infarcted myocardium can be
differentiated by first-pass myocardial
perfusion and myocardial delay enhancement
techniques
Ischaemic but
Non-viable
viable myocardium myocardium
Rest perfusion
Normal signal
Signal loss
Stress perfusion
Signal loss
Signal loss
Myocardial delay
enhancement
None
Presence
Safety of Stress Cardiac MRI
Exam.
 Staff of multiple disciplines
(including Radiographers,
Radiologists, Nurses &
Cardiologists will be involved in
stress cardiac MRI examination
 Only properly screened personnel
shall be allowed to enter the
control access area of MRI
Scanner Room
Safety of Stress Cardiac MRI
Exam.
 Patient screening for any contra-indications of MRI and Adenosine e.g.
cardiac pacemaker or asthmatic history
 ECG investigation will be performed before stress MRI examination to
assess any second- or third –degree heart block or acute myocardial
infarction, which are contraindications for Adenosine stress examination
 Adequate patient preparation
 ECG investigation will be performed after stress MRI examination to
exclude Adenosine induced infarction
Safety of Stress Cardiac MRI
Exam.
 A total of 0.2mmol/kg Gd-based contrast
medium will be administered for rest
perfusion, stress perfusion and myocardial
delay enhancement imaging
 In view of the risk of Nephrogenic Systemtic
Fibrosis (NSF) for patients with severe or endstage renal disease, renal function test result
should be checked for high-risk patients
 Informed consent shall be obtained if
necessary
Safety of Stress Cardiac MRI
Exam.
 Multiple MRI-safe ancillary equipment are
necessary for stress MRI examination
 Infusion pump
 Power injector
 Vital sign monitoring system
NIBP, Pulse rate, SaO2
 ECG electrode and leads
Safety of Stress Cardiac MRI
Exam.
 Examination checklist
 Patient monitoring records
Safety of Stress Cardiac MRI
Exam.
 Aminophylline shall be ready for emergency
situation
 Belongs to a group of medicines known as
xanthines
 Treat breathing difficulties associated with
reversible airway obstruction, as in bronchial
spasm
Safety of Stress Cardiac MRI
Exam.
 Cardiologist will stay in the
MRI scanner room during
administration of
Adenosine to monitor the
patient’s condition
 The infusion of Adenosine
will be terminated in case
of symptoms of flushing,
SOB and chest pain
 Continuous monitoring of
vital signs during entire
stress MRI examination
Protocols of Adenosine Stress
MRI Exam. in DR, QMH
0.05mmol/Kg
MR Contrast
Media
Localizer
Sequences
Myocardial
Perfusion
(Stress*)
Short axis view
0.05mmol/Kg
MR Contrast
Media
FIESTA Cine
Short Axis View
FIESTA Cine
2-chamber, 4chamber or 3chamber view
Delay 10mins
Total Imaging Time: about 45mins
Additional 0.1mmol/Kg
MR Contrast Media
injected immediately
after rest perfusion study
Myocardial
Perfusion
(Rest)
Short axis view
Delay 10mins
Myocardial
Viability Study:
Short axis, 2-, 3- &
4-chamber views
Localizers
 3-plane localizer, 2-chamber, 4-chamber
localizer
 The goal is to prescribe imaging planes along
short- and long-axis of the heart
 Short axis view
 2-chamber view
 3-chamber view
 4-chamber view
Localizers
3-plane localizer
Short Axis View
 Cover from base to apex
 Quantification of LV & RV volumes,
ejection fraction and myocardial mass
 Evaluation of regional wall motion
Long Axis Views
3-Chamber
2-Chamber
4-Chamber
Left Ventricular Segmentation
First-pass Myocardial
Perfusion
Rest
Stress
Myocardial Delay Enhancement
Conclusion
 MRI has a definite role in the assessment and
management of patients with IHD
 It is an ideal imaging technique for serial
follow-up and screening due to being noninvasive and involves no irradiation
 An single examination can assess cardiac
function, regional wall motion, regional
perfusion, and the extent of infarction
Thank you