NUCLEAR CARDIOLOGY Flashcards
What is nuclear cardiology?
A field of cardiology that uses radioisotopes to assess myocardial perfusion and myocardial function.
What is myocardial perfusion imaging (MPI)?
A noninvasive imaging method that utilizes radioisotopes to assess regional myocardial blood flow, function, and viability.
What imaging techniques can be used in MPI?
- Single-photon emission computed tomography (SPECT)
- Positron emission tomography (PET)
What happens during the stress portion of an MPI test?
Exercise increases myocardial demand or a pharmacologic agent is used to produce vasodilation in the coronary vascular bed.
How does a normal blood vessel respond to stress during MPI?
A normal vessel can increase coronary blood flow up to four times its baseline.
What is a perfusion defect?
An area of reduced radiotracer uptake in the myocardium.
What differentiates a fixed defect from a reversible defect in MPI?
A fixed defect occurs during both stress and rest, while a reversible defect is present only during stress.
What are the uses of myocardial perfusion imaging?
- Diagnose coronary artery disease (CAD)
- Localize and quantify ischemia
- Determine infarct size
- Risk stratification
- Assess residual ischemia after revascularization
- Assess myocardial viability
What is the sensitivity and specificity of MPI compared to stress echocardiography?
Sensitivity: 85% vs. 75%; Specificity: 79% vs. 88%.
What are the two main radiopharmaceutical agents used in MPI SPECT?
- Thallium-201 (Tl-201)
- Technetium-99m (Tc-99m)
What is the half-life of Thallium-201?
73 hours.
What is a key characteristic of Thallium-201 in MPI?
Myocardial redistribution after initial uptake.
What is the half-life of Technetium-99m?
6 hours.
What is the importance of Technetium’s short half-life?
It reduces radiation exposure to the patient.
What are the stress modalities for myocardial perfusion imaging?
- Exercise-induced
- Pharmacologic
What are common forms of exercise used in stress testing?
- Treadmill
- Bicycle
- Isometric handgrip
What is a major contraindication for exercise stress testing?
Severe aortic stenosis or decompensated heart failure.
What is the sum difference score (SDS) in MPI?
The difference between summed rest score (SRS) and summed stress score (SSS), representing the amount of ischemia.
Fill in the blank: A _______ defect suggests the presence of ischemia.
reversible
True or False: A fixed defect always indicates myocardial scar.
False.
What is the method used for semiquantitative analysis of perfusion defects?
Scores from 0 to 4 are assigned to each segment based on severity.
What does a score of 0 indicate in semiquantitative evaluation?
Normal count.
What does a score of 4 indicate in semiquantitative evaluation?
Absence of uptake.
What is dobutamine used for?
Diagnose CAD, assess risk for those who cannot exercise
CAD stands for coronary artery disease.
List contraindications for the use of dobutamine.
- Cannot exercise
- LBBB on ECG
- Severe AS
- Decompensated heart failure
- Active acute coronary syndrome
- Bronchospastic COPD or asthma
- Heart block
- Hypotension
- Tachyarrhythmias
- Uncontrolled hypertension
LBBB stands for left bundle branch block; AS stands for aortic stenosis; COPD stands for chronic obstructive pulmonary disease.
What is a notable advantage of using dobutamine in stress testing?
Produces excellent vasodilation equal to that of exercise
FS refers to functional status.
What is the Duke treadmill score used for?
Determining prognosis for cardiac events
It takes into account exercise time, chest pain grade, and ST-segment deviation.
What is the significance of achieving 85% of maximal predicted heart rate during exercise?
It indicates that pharmacologic agents can be used if unable to exercise to that level
Maximal predicted heart rate is calculated as ‘220 - age’.
What are the pharmacologic stress agents mentioned?
- Dobutamine
- Dipyridamole
- Adenosine
- Regadenoson
How do dipyridamole, adenosine, and regadenoson function as vasodilators?
They act on adenosine receptors causing a 3.5- to 5-fold increase in myocardial blood flow
Dipyridamole increases endogenous adenosine levels, while adenosine and regadenoson increase levels exogenously.
What are common side effects of vasodilators?
- Flushing
- Headache
- Nausea
- Shortness of breath
True or False: Vasodilators are safe for patients with severe bronchospastic COPD.
False
However, recent research shows regadenoson may be safe for patients with mild and moderate COPD.
What is the purpose of gated SPECT imaging?
To assess left ventricular volumes and left ventricular ejection fraction (LVEF)
Gating allows determination of ventricular volumes at different points in the cardiac cycle.
What does first-pass radionuclide angiography (FPRNA) assess?
LVEF, right ventricular ejection fraction, regional wall motion, and cardiopulmonary shunts
It uses a bolus technique and rapid acquisition.
List the benefits of using radionuclide angiography to assess LVEF.
- Accurate and reproducible measure
- Less expensive than MRI
- Useful when other methods are not possible
- Independent predictor of cardiac events
What is the range of radiation exposure for patients during nuclear tests?
From about 3 mSv to upward of 30 mSv
mSv stands for milliSievert.
What is the ALARA principle in the context of radiation exposure?
To keep radiation exposure as low as reasonably achievable
This is important to minimize the risk of developing malignancy.
What should physicians discuss with patients prior to nuclear tests?
Risks and benefits of radiation exposure
