Cardiovascular MCQs
Practice questions on myocardial perfusion imaging, viability assessment, and ventricular function studies.
What is the mechanism of thallium-201 redistribution?
Explanation: Tl-201 continuously exchanges across cell membranes via Na/K-ATPase. Initial uptake reflects blood flow, but over time it redistributes based on potassium pools and cellular viability.
In gated SPECT, the R-R interval is typically divided into how many frames?
Explanation: The R-R interval is typically divided into 8 or 16 frames. Eight frames is most common, with each frame representing ~12.5% of the cardiac cycle.
Which finding on gated SPECT suggests a LOW ejection fraction?
Explanation: Large end-systolic cavity with minimal wall motion indicates poor contractile function and low EF. Small end-systolic cavity with vigorous wall thickening indicates preserved function.
Breast attenuation artifact typically affects which myocardial wall?
Explanation: Breast tissue attenuates photons from the anterior and anteroseptal walls, creating fixed defects. Prone imaging or attenuation correction helps differentiate artifact from disease.
Aminophylline reverses the effects of which stress agent?
Explanation: Aminophylline is an adenosine receptor antagonist that reverses adenosine/regadenoson side effects. Patients should avoid caffeine before these agents as it also blocks adenosine receptors.
Which stress agent is preferred for patients with severe reactive airway disease?
Explanation: Dobutamine is the preferred pharmacologic stress agent for patients with asthma/COPD because adenosine receptor agonists can cause bronchospasm.
A ‘reversible defect’ on stress/rest MPI indicates:
Explanation: A reversible defect (present on stress, normalized on rest) indicates ischemia - viable myocardium with inadequate blood supply during stress but adequate supply at rest.
Transient ischemic dilation (TID) on MPI suggests:
Explanation: TID (larger LV cavity on stress vs rest images) suggests severe/extensive CAD, often indicating balanced ischemia or diffuse subendocardial ischemia.
Left Bundle Branch Block (LBBB) often causes a false-positive septal defect due to:
Explanation: LBBB causes asynchronous septal contraction (septal beaking). During exercise stress at high heart rates, this creates a reversible septal defect (artifact). Pharmacologic stress is preferred.
Which agent has the shortest physical half-life?
Explanation: Rubidium-82: 75 seconds; Ammonia N-13: 10 minutes; Tc-99m: 6 hours; Tl-201: 73 hours.
The ‘rim sign’ (cardiac creep) is associated with:
Explanation: Upward creep of the heart during acquisition (often due to deep breathing/diaphragm movement post-exercise) causes a specific artifact pattern known as the rim sign.
Metabolic viability imaging with F-18 FDG requires:
Explanation: To promote glucose uptake by the myocardium, patients are glucose-loaded (oral glucose load + insulin) to switch the heart from fatty acid to glucose metabolism (metabolic clamping).
Dipyridamole acts by:
Explanation: Dipyridamole inhibits the cellular reuptake of adenosine, thereby increasing extracellular adenosine levels and causing vasodilation.
Clinical Pearl: Caffeine-containing products should be avoided for at least 12-24 hours before adenosine or regadenoson stress testing.