Download The ideal perfusion tracer

Nuclear Medicine in Cardiology
A. Hussein S. Kartamihardja
Department of Nuclear Medicine
Padjadjaran University – Dr. Hasan Sadikin Hospital
What does the heart do ?
• The heart is a powerful muscle
consisting of two pumps side
by side.
• Its steady beating maintains
flow of blood to all parts of the
body throughout life.
Diagnostic modalities in heart disease
ECG/ Treadmill
Radiography
Echocardiography
CT scan
MRI
Angiography
Radionuclide imaging
Department of Nuclear Medicine
Padjadjaran University – Dr. Hasan Sadikin Hospital
Cardiac Nuclear Medicine
Radiopharmaceutical
Instrumentation
Department of Nuclear Medicine
Padjadjaran University – Dr. Hasan Sadikin Hospital
Physician
History of nuclear cardiology
Blumgard and Weiss (1927) :
the first use of radioactivity in the study of the
cardiovascular system
Wilson : measurement of the circulation times
Tl-201 (1971)
The development and improvement of SPECT
The development and established Tc-labeled agents
Alternative stress than physical exercise
Gate-spect allows simultaneous assessment both of
myocardial perfusion, function and assessment of
myocardial viability
Gamma camera coincidence imaging system
Myocardial metabolic imaging
Department of Nuclear Medicine
Padjadjaran University – Dr. Hasan Sadikin Hospital
The ideal perfusion radiopharmaceutical
Distribution in the myocardium in linier
proportional to blood flow.
Efficient myocardial extraction from
blood on the first passage through the
heart
Stable retention within myocardium
during data acquisition
Rapid elimination allowing repeat
studies under different conditions
Good imaging characteristics (short half
life, low radiation burden to the patient)
Ready availability
Competitive pricing
No current tracer possesses all of these
properties.
Department of Nuclear Medicine
Padjadjaran University – Dr. Hasan Sadikin Hospital
Thallium-201
Tc-99m Teboroxim
Tc-99m MIBI
Tc-99m Tetrofosmin
Thallium –201
Basic Properties
A metallic element which behaves chemically in a
similar manner to potassium and is given as thallous
chloride
Photon energy is low, and 88% of its emissions are
x-ray with photon energy of 60-80keV
Gamma photons of 135 and 167 keV (12%)
Enter myocyte by


60% active transport via Na+/K+ ATPase pump
40% passively along the electrochemical gradient
Distribution within the myocardium is proportional to
blood flow
The half life of elimination within the heart is
approximately 7 hrs
Department of Nuclear Medicine
Padjadjaran University – Dr. Hasan Sadikin Hospital
Tc-99m MIBI (methoxyisobutylisonitrile)
Tc-99m TETROFOSMIN (Basic Properties)
It is lipophilic
Distribution within the myocardium is proportional to
blood flow
Diffuses out of the capillary into cardiac myocytes and
is associated with mitochondria within the cell.
Cardiac uptake is depend on normal mitochondrial
function.
Liver uptake of tetrofosmin is not as prominent as with
Tc-99m MIBI
No redistribution
Department of Nuclear Medicine
Padjadjaran University – Dr. Hasan Sadikin Hospital
Correlation between Tl-201 and Tc-99m tetrofosmin imaging
Department of Nuclear Medicine
Padjadjaran University – Dr. Hasan Sadikin Hospital
Clinical application of Nuclear Cardiology
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•
•
•
•
•
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CAD
Acute and post MI
Cardiomyopathy
Valvular disease and Shunts
Cardiotoxicity
Aneurysms
Transplants
Diagnosis & prognosis
Risk stratification
Medical vs. surgical treatment
Efficiency of management
Stress-rest Tl-201 and Tc-99m labeled agents has been widely used in the
diagnosis and assessment of coronary artery disease
MPI still an important position in clinical practice
only 1/3 of symptom-free men with exercise induced ST segment depression
had coronary angiographic lesions > 50% diameter stenosis
MPI has been proposed to improve the accuracy and risk assessment of
exercise testing in patients with suspected CAD
Sensitivity 74% - 96%, specificity 65% -97%
Department of Nuclear Medicine
Padjadjaran University – Dr. Hasan Sadikin Hospital
Principles of myocardial perfusion imaging ?
Imaging at 24 hrs is sometimes performed
when the question of underestimation of
myocardial mass in the redistribution
images is clinically important
• What is coronary artery disease ?
• A condition where there is progressive damage to the vessel wall
supplying the coronary arteries.
• Unbalance between demand and supply O2 to myocardium
Department of Nuclear Medicine
Padjadjaran University – Dr. Hasan Sadikin Hospital
Cardiac stress test
Physical exercises
Exercise has to be adequate to produced the
heterogenity in blood flow to achieve high
detection sensitivity
 Treadmil
 Ergocycle
Pharmacological
Pharmacological stress test become important,
since many patients are unable to exercise
Pharmacological stress agents largely remove
the need for patient cooperation and motivation,
and enable a confident assessment of cardiac
function in virtually all cases
 Dipyridamole
 Dobutamine
 Adenosine
Department of Nuclear Medicine
Padjadjaran University – Dr. Hasan Sadikin Hospital
Dipyridamole
Coronary artery dilator
The effects of dipyridamole
include a mild decrease in
systolic BP, slight increase HR.
The side effects include
flushing, abdominal pain,
nausea, vomiting, transient AV
block and bronchospasm
Infusion dose of 0.56 mg/kg
over four minutes (0.14
ml/kg/min)
Department of Nuclear Medicine
Padjadjaran University – Dr. Hasan Sadikin Hospital
Dobutamine
The ß-agonists increase myocardial oxygen demand
through a combined inotropic and chronotropic action
It dilates the distal coronary vessels, which leads to an
increase in coronary flow
Dose up to 40 ug/kg/min (commence at 10 ug/kg/min and
proceed in 10 ug/kg/min step every 3 min)
Non-cardiac symptoms cause by dobutamine include
tingling, flushing, nausea, headache, shaking and
lightheadedness
Department of Nuclear Medicine
Padjadjaran University – Dr. Hasan Sadikin Hospital
Adenosine
Is a naturally occurring purine which mediates the cellular action of
dipyridamole
No significant difference between the coronary hyperemic response
to adenosine and dipyridamol
Has very short half life of between 2 – 10 seconds
Maximal coronary vasodilatation is achieved in 85% of patients with
intravenous dose of 140ugr/kg/min
Side effect are similar to those with dipyridamol
Department of Nuclear Medicine
Padjadjaran University – Dr. Hasan Sadikin Hospital
Spect imaging
In SPECT imaging, the heart is viewed in 3
planes :
1.
The horizontal long axis, which is
parallel to the long axis of the heart
from base to apex. It begins at the
inferior aspect of the heart and
progresses superiorly
2.
The vertical long axis, which is
perpendicular to the horizontal long
axis. It begins at the lateral aspect of
left ventricle and proceeds medially
through the septum
3.
The short axis of the heart which is
perpendicular to both of the long axes.
It begins at the base of the heart and
progress through the mid plane to the
apex
Department of Nuclear Medicine
Padjadjaran University – Dr. Hasan Sadikin Hospital
Image interpretation
I. Defects
 Location
 Extent
 Severity
 Reversible or fixed
 Quantitative or semi quantitative analysis
II. Other information
 Transient ischemic dilation
 Lung uptake
Department of Nuclear Medicine
Padjadjaran University – Dr. Hasan Sadikin Hospital
Normal perfusion scan
There is a wide variety of normal
appearances arising from
variation in size and position of
the heart, body size and quality
of tomographic acquisition
Knowledge of these variation
and confidence in their
identification is vital to prevent
the reporting of defects as
normal variant
An important issue to bear in
mind if difficulty arise in
distinguishing normal variants
from true defects
Department of Nuclear Medicine
Padjadjaran University – Dr. Hasan Sadikin Hospital
Department of Nuclear Medicine
Padjadjaran University – Dr. Hasan Sadikin Hospital
G 2121-00
PRE-PTCA
POST-PTCA
Differences between stress and rest/redistribution imaging
indicates reversibility (ischemia)
Department of Nuclear Medicine
Padjadjaran University – Dr. Hasan Sadikin Hospital
M724499
PATIENT NO : M724499
SEX
: MALE
AGE
: 53 YRS
CLINICAL INDICATION :
TWO ACUTE
CORONARY EPISODES
ANGIOGRAM:
A STENOSIS AT THE PROXIMAL AND MIDDLE THIRDS OF THE LAD ARTERY
Department of Nuclear Medicine
Padjadjaran University – Dr. Hasan Sadikin Hospital
REST MPI SPECT
NO
SEX
AGE
ECG
GATED BLOOD POOL
: S 0585/01
: MALE
: 60 YRS
: NON Q-WAVE MYOCARDIAL INFARCTION
Department of Nuclear Medicine
Padjadjaran University – Dr. Hasan Sadikin Hospital
S 0585/01
Comparison between SPECT and Treadmill exercise test
Variable
SPECT
Treadmill
++
++++
++++
+
Familiarity
++
++++
Accuracy
+++
+
Localization
++++
+
Extent of disease
++++
+
Viable myocardium
++++
+
Left ventricular function
++++
+
Risk assessment
++++
+
Availability
Cost
Department of Nuclear Medicine
Padjadjaran University – Dr. Hasan Sadikin Hospital
Risk Stratification
Outcome following non-fatal MI
:
Low risk group
50% - 66% of the patients
Can be managed with medical
treatment
High risk group
34% - 50% of the patients
Prone to future complications with 3
months death, re-infarction, CHF and
unstable angina
Separation of high and low
risk groups :
•
•
•
•
•
•
Clinical evaluation
Rest and stress ECG*
Rest and stress RNA*
Rest and stress MPI*
Rest and stress echo
Angiography
• Recommended by ACC & AHA
Task Force
• Nuclear cardiology separates high risk patient who need invasive and
expensive procedures and low risk patient who do not.
• Acts as a ”Gate - Keeper” for referral to angiography.
Department of Nuclear Medicine
Padjadjaran University – Dr. Hasan Sadikin Hospital
Myocardial perfusion scan findings associated with increased risk
for cardiac events after acute myocardial infarction
Perfusion defects induced by
exercise or pharmacological
Reversible perfusion defects in
multiple coronary vascular
territories
Large perfusion defect size
Improved reperfusion after Tl201 reinjection
Increased lung uptake
Left ventricular cavity dilatation
Left ventricular dysfunction on
gated myocardial perfusion
scan
Abnormal right ventricular
uptake
Department of Nuclear Medicine
Padjadjaran University – Dr. Hasan Sadikin Hospital
Myocardial Viability / Hibernation
Persistently impaired myocardial and left ventricular function at rest, due to reduced
coronary blood flow. (Rahimtola)
The functional abnormality can be partially or completely restored to normal by
reducing myocardial oxygen demand and/or increasing coronary blood flow
Myocardial dysfunction is expected to be
irreversible in regions with myocardial scar, but
can be improved in region with ischemic but viable
or hibernating myocardium.
The determination of myocardium viability in
patients with CAD and the LV dysfunction has
become a frequent issue since interventional
cardiology is growing rapidly.
The differentiation of scar from hibernating
myocardium is important.
Up to now, radionuclide myocardial imaging holds
the most important promise in this field.
Metabolic measurement by PET may be the most
sensitive non-invasive approach for the evaluation
of myocardial viability.
Department of Nuclear Medicine
Padjadjaran University – Dr. Hasan Sadikin Hospital
Myocardial Viability
Why separate viable from scar tissue ?
• Surgical treatment for viable
myocardium results in 11.5% event
rate compared to 50% after medical
treatment
• Surgical treatment for poor viability
and scar have survival rate of 79%
compared to 97% with viable tissue
LVD due to viable tissue have worse
prognostic than scars with annual
survival of 50% compared with 92%
(PET data)
Department of Nuclear Medicine
Padjadjaran University – Dr. Hasan Sadikin Hospital
Techniques for assessing myocardial viability
Regional wall motion evaluation
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Ventriculography (gated spect)
Echocardiography (dobutamine)
Radionuclide angiography
Magnetic resonance imaging
Perfusion and cell membrane integrity
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Tl-201protocols
Tc-99m sestamibi
Tc-99m tetrofosmin
Nitrate-augmented perfusion imaging
Assessment of metabolism
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Well established for predicting functional recovery after
revisualization
F-18 FDG
I-123 fatty acids (IPPA, BMIPP)
Department of Nuclear Medicine
Padjadjaran University – Dr. Hasan Sadikin Hospital
Cost Effectiveness of Nuclear Cardiology
Historical Background
Nuclear Cardiology as “ a better stress test ”
Detection of CAD as a benchmark for success
Gold standard : coronary angiography
Misconceptions
• Expensive stress test
• Sensitivity < 100%
• False positive
• Imperfect correlation
with angiography
The changing paradigm
• Angiography provides information on anatomy
• Nuclear cardiology provides information on
function/physiology
• Physiology is as important as anatomy, and
perhaps more important
• Functional testing with nuclear imaging
provide comparable prognostic information at
lower cost than angiography, non-invasive
• Information provided by nuclear cardiology
can reduce cost and optimize treatment
Department of Nuclear Medicine
Padjadjaran University – Dr. Hasan Sadikin Hospital
Summary
MPI has been widely used and an important position in the
diagnosis and assessment of CAD Sensitivity 74% - 96%, specificity
65% -97%
Nuclear cardiology separates persistent defect with LV dysfunction
but viable myocardium from scar tissue
• Nuclear cardiology separates high risk patient who need invasive
and expensive procedures from low risk patient who do not.
• Acts as a ”Gate - Keeper” for referral to angiography.
Cost of management strategies using MPI are cheaper and equally
effective when compared with strategies without MPI with same
outcome.
Department of Nuclear Medicine
Padjadjaran University – Dr. Hasan Sadikin Hospital
Thank you !
Department of Nuclear Medicine
Padjadjaran University – Dr. Hasan Sadikin Hospital