Chapter 18: Nuclear Cardiology
The concept that CAD can be detected with radiopharmaceuticals used for SPECT-MPI is based on the ability to detect a relative reduction in myocardial perfusion in a region supplied by a significantly stenosed vessel when compared with a normal region during hyperemia. Which of the following factors beyond focal percent stenosis can affect the degree of hyperemia achievable in diseased vessels?
A. Myocardial mass distal to the stenosis
B. Endothelial dysfunction
C. Nonatherosclerotic microvascular disease
The answer is E. (Hurst’s The Heart, 14th Edition, Chap. 18) Multiple factors beyond focal percent stenosis can also affect the degree of hyperemia achievable in diseased vessels. These include stenosis length, myocardial mass distal to the stenosis, plaque composition, diffuse atherosclerosis, nonatherosclerotic microvascular disease, and endothelial dysfunction.1,2 In general, a significant reduction in maximal hyperemia is usually present when stenosis severity exceeds 70%.3 However, when compared to assessment of fractional flow reserve (FFR), considered the gold standard, only 35% of vessels visually assessed as having 50% to 70% stenosis manifest a decrease in maximal hyperemia.4
A 55-year-old double-amputee man with a prior history of ischemic heart disease, migraine, dyslipidemia, and hypertension was admitted to the emergency department with central chest pain. His medications include bisoprolol, amlodipine, isosorbide dinitrate, aspirin, ramipril, rosuvastatin, and the over-the-counter Excedrin Migraine. Initial ECG and biomarkers were within normal limits. Three days after admission, the patient underwent stress nuclear SPECT-MPI for risk stratification. With regard to his medications, which of the following statements is true?
A. Bisoprolol should be discontinued for 12 hours before stress imaging
B. Amlodipine should be discontinued for 12 hours before stress imaging
C. Isosorbide dinitrate should be discontinued for 48 hours before stress imaging
D. Excedrin Migraine should be discontinued for 24 hours before stress imaging
The answer is D. (Hurst’s The Heart, 14th Edition, Chap. 18) In general, for purposes of diagnosis or initial risk stratification, stress nuclear MPI is performed with the patient off anti-ischemic medications5 because these medications may limit the development of ischemia during the stress test. When feasible, the use of beta-blockers or long-acting calcium channel blockers should be discontinued for 48 hours before stress imaging, and long-acting nitrates should be discontinued for 12 hours before stress imaging.5 In general, discontinuation of compounds containing caffeine (Excedrin ...