Magnetic Resonance Imaging in Ischaemic Heart Disease

8/11/2019 Magnetic Resonance Imaging in Ischaemic Heart Disease

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Danny Cho Wai Man,

Rad I (DR), Queen Mary HospitalApril 2011


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Outline

Introduction

Clinical investigations of IHD

MRI in the assessment of IHD

Safety in Cardiac MR examination

Imaging protocol for IHD in QMH


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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


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Introduction

Diagnosis of IHD requires careful historytaking and physical examination, along

with direct investigation Diagnostic imaging plays an important

role in the proper assessment and

management of coronary artery disease


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Clinical investigations of IHD

Electrocardiography (ECG)

Echocardiography

Nuclear medicine Positron emission tomography (PET)

Computed tomography (CT)

Coronary angiography

Magnetic resonance imaging (MRI)


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Electrocardiography(ECG)

One of the standard investigation performed inpatients with chest pain

Exercise stress electrocardiography is the most

widely applied test to obtain objective evidenceof myocardial ischaemia and significantcoronary artery disease


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Echocardiography

Provides a good estimate ofventricular size as well as

regional and generalized left

ventricular wall motion

Stress echocardiographyeither by exercise or by

pharmacological means is

comparable in accuracy to

radionuclide testing for

diagnosis of coronary artery

disease


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Radionuclide Imaging

Provides higher sensitivityand specificity for thediagnosis of IHD than

exercise ECG testing

It can provide functionalor physiological and

prognostic information, isquantifiable andreproducible


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Positron Emission Tomography

(PET) Provides more accurate result

for the detection of CAD

Provides an estimate ofcoronary blood flow andcoronary flow reserve as well

as myocardial viability

Popularity limited by the highcost


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Computed Tomography (CT)

CT angiography provides high resolution

imaging of the heart and give good

visualization of the coronary arteries


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Coronary Angiography

Gold standard in the

diagnosis of ischaemic heart

disease

It has a very good spatialresolution of 300m

Ascertains the anatomicextend and severity of the

atherosclerotic involvement

of the coronary arteries


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Magnetic Resonance Imaging

(MRI)

Global cardiac function and regional

wall motion abnormalities Regional perfusion

Myocardial infarction Coronary MRA


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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


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wall motion Good spatial and temporal resolution

Allowing imaging of systolic and diastolicphases of both right and left ventricles

Cine short-axis images from base toapex

Yields reproducible data for myocardial massand ventricular size

Regional wall thickness of ventricle,valvular motion, and regional wallmotion can be clearly defined

Good contrast between blood pool andmyocardium


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wall motion Commercially available software

yields calculations of stroke volume,ejection fraction, end-systolic

volume, end-diastolic volume,myocardial wall thickening withinfew minutes

Advantages of non-invasiveness, noirradiation, high reproducibility,and high repeatability of resultsmake it an ideal tool for serialmeasurement and monitoring ofcardiac function


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First-pass

Myocardial Perfusion For the detection of regional

ischaemia

Good temporal resolution to imagefirst-pass of contrast mediumthrough myocardium

Adequate contrast between normaland ischaemic myocardium

Adequate coverage from apex tobase of the heart (multiple short axisslices in basal, mid-ventricular, andapical regions of left ventricle)


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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 stresscondition is necessary for demonstration of

perfusion defects


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Stress Cardiac MRI Exam.

Physical stress may not be feasiblewithin the MRI environment

Pharmacological stress will bemore easily to implement usingvasodilator e.g. adenosine

Myocardial blood flow will increasefourfold to fivefold downstream ofnormal coronary arteries, but does

not increase downstream ofstenosed arteries because therelated arteriolar beds have alreadyvasodilated maximally


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Stress Cardiac MRI Exam.

Myocardium receiving bloodsupply from an significantlystenosed coronary artery willshow hypoperfusion comparedwith normal myocardium

Normally perfused myocardiumshows greater enhancement at afaster rate than hypoperfusedmyocardium

LV

Normal

myocardium

Infarcted or

Ischaemic

myocardium


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Adenosine Stress Cardiac MRI

Exam. Short half life (


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Contraindications of Adenosine

Acute Myocardial infarction within few days

Asthma

Second- or third-degree atrio-ventricularblock

Sick sinus syndrome

Symptomatic bradycardia


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Patient Preparation for

Adenosine Stress MRI Exam.

Refrain from caffeinated food and drink for24 hours

Such as coffee, tea, coke and chocolate

Adenosine antagonist

Interfere with the ability of Adenosine to dilatearteries

False negative examination result


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Exam.

Adenosine at 140g/kg/min intravenously for4 mins

Gadolinium-DTPA (0.05 mmol/kg) is rapidlyinfused (4ml/sec)

First-pass imaging is performed usinggradient echo pulse sequence on multiple

short axis slices (basal, middle, and apex) ofthe left ventricle during a breath hold


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Exam. Normal myocardium shows a

blush of bright signal

throughout the cardiac cycle

Ischaemic or infarctedmyocardium will show a

persistent dark signal, eithersubendocardial or transmural in

location The perfusion defect shall follow

the supply territory of the

coronary arteries


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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


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Myocardial Infarction

Post-gadolinium myocardial delay enhancementtechnique

Areas of infarct or scar have increased volume ofdistribution of gadolinium as compared to normalmyocardium

There is more efficient egress of gadolinium from normalmyocardium compared to infarcted tissue

Hyperenhancement of infarcted myocardium 10-20mins

after contrast administration


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Ischaemia vs Infarction

Ischaemic and infarcted myocardium can bedifferentiated by first-pass myocardialperfusion and myocardial delay enhancementtechniques

Ischaemic butviable myocardium

Non-viablemyocardium

Rest perfusion Normal signal Signal lossStress perfusion Signal loss Signal loss

Myocardial delayenhancement

None Presence


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Safety of Stress Cardiac MRI

Exam.

Staff of multiple disciplines(including Radiographers,

Radiologists, Nurses &

Cardiologists will be involved instress cardiac MRI examination

Only properly screened personnelshall be allowed to enter the

control access area of MRIScanner Room


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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 toassess any second- or third degree heart block or acute myocardialinfarction, which are contraindications for Adenosine stress examination

Adequate patient preparation

ECG investigation will be performed after stress MRI examination toexclude Adenosine induced infarction


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Exam. A total of 0.2mmol/kg Gd-based contrast

medium will be administered for restperfusion, stress perfusion and myocardialdelay enhancement imaging

In view of the risk of Nephrogenic SystemticFibrosis (NSF) for patients with severe or end-stage renal disease, renal function test resultshould be checked for high-risk patients

Informed consent shall be obtained if

necessary


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Exam.

Multiple MRI-safe ancillary equipment arenecessary for stress MRI examination

Infusion pump

Power injector

Vital sign monitoring system

NIBP, Pulse rate, SaO2

ECG electrode and leads


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Exam.

Examination checklist

Patient monitoring records


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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


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Exam.

Cardiologist will stay in theMRI scanner room duringadministration of

Adenosine to monitor thepatients condition

The infusion of Adenosinewill be terminated in caseof symptoms of flushing,SOB and chest pain

Continuous monitoring ofvital signs during entirestress MRI examination


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Protocols of Adenosine Stress

MRI Exam. in DR, QMH

Myocardial

Perfusion

(Stress*)

Short axis view

Myocardial

Perfusion

(Rest)

Short axis view

Myocardial

Viability Study:

Short axis, 2-, 3- &

4-chamber views

0.05mmol/Kg

MR Contrast

Media

0.05mmol/Kg

MR Contrast

Media

Localizer

Sequences

Additional 0.1mmol/Kg

MR Contrast Media

injected immediately

after rest perfusion study

Delay 10mins

FIESTA Cine

Short Axis View

FIESTA Cine

2-chamber, 4-

chamber or 3-

chamber view

Delay 10mins

Total Imaging Time: about 45mins


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Localizers

3-plane localizer, 2-chamber, 4-chamberlocalizer

The goal is to prescribe imaging planes alongshort- and long-axis of the heart

Short axis view

2-chamber view

3-chamber view

4-chamber view


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Localizers

3-plane localizer


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Short Axis View

Cover from base to apex Quantification of LV & RV volumes,

ejection fraction and myocardial mass

Evaluation of regional wall motion


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Long Axis Views

2-Chamber 3-Chamber

4-Chamber

Left Ventricular Segmentation


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First-pass Myocardial

Perfusion

Rest Stress


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Myocardial Delay Enhancement


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Conclusion

MRI has a definite role in the assessment andmanagement of patients with IHD

It is an ideal imaging technique for serialfollow-up and screening due to being non-invasive and involves no irradiation

An single examination can assess cardiac

function, regional wall motion, regionalperfusion, and the extent of infarction


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Thank you

Documents

Magnetic Resonance Imaging in Ischaemic Heart Disease