Nuclear Medicine in Cardiology

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Nuclear Medicine in Cardiology
A. Hussein S. Kartamihardja
Department of Nuclear Medicine Padjadjaran
University Dr. Hasan Sadikin Hospital
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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
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Cardiac Nuclear Medicine
Radiopharmaceutical
Physician
Instrumentation
Department of Nuclear Medicine Padjadjaran
University Dr. Hasan Sadikin Hospital
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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
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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.

• Thallium-201
• Tc-99m Teboroxim
• Tc-99m MIBI
• Tc-99m Tetrofosmin

Department of Nuclear Medicine Padjadjaran
University Dr. Hasan Sadikin Hospital
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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
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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
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Correlation between Tl-201 and Tc-99m tetrofosmin
imaging
Department of Nuclear Medicine Padjadjaran
University Dr. Hasan Sadikin Hospital
9
Clinical application of Nuclear Cardiology

• 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 practiceonly 1/3
of symptom-free men with exercise induced
ST segment depression had coronary angiographic
lesions gt 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
10
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
11
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
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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
13
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
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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
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Spect imaging

• In SPECT imaging, the heart is viewed in 3 planes
  
• 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
• 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
• 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
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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
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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
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Department of Nuclear Medicine Padjadjaran
University Dr. Hasan Sadikin Hospital
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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
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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
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REST MPI SPECT
GATED BLOOD POOL
NO S 0585/01  SEX MALE AGE
60 YRS ECG NON Q-WAVE MYOCARDIAL INFARCTION
S 0585/01
Department of Nuclear Medicine Padjadjaran
University Dr. Hasan Sadikin Hospital
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Comparison between SPECT and Treadmill exercise
test
Variable SPECT Treadmill
Availability
Cost
Familiarity
Accuracy
Localization
Extent of disease
Viable myocardium
Left ventricular function
Risk assessment
Department of Nuclear Medicine Padjadjaran
University Dr. Hasan Sadikin Hospital
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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
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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 Tl-201 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
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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
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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
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Techniques for assessing myocardial viability

• Regional wall motion evaluation
• Ventriculography (gated spect)
• Echocardiography (dobutamine)
• Radionuclide angiography
• Magnetic resonance imaging
• Perfusion and cell membrane integrity
• Tl-201protocols
• Tc-99m sestamibi
• Tc-99m tetrofosmin
• Nitrate-augmented perfusion imaging
• Assessment of metabolism
• 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
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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 lt 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
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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
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Thank you !
Department of Nuclear Medicine Padjadjaran
University Dr. Hasan Sadikin Hospital