A 65-year-old man with stable angina is scheduled for a pharmacologic stress test using intravenous dipyridamole. He reports daily consumption of a caffeinated beverage. Which instruction is most critical prior to the test?

• A Hold beta-blockers for 24 hours
• B Fast for 12 hours
• C Discontinue ACE inhibitors on the day of the test
• D Avoid methylxanthines for 24 hours ✓

Explanation

Dipyridamole causes coronary vasodilation and can induce ischemia via coronary steal. Methylxanthines like caffeine are competitive antagonists of adenosine receptors and block the vasodilatory effect of dipyridamole, rendering the test falsely negative. Beta-blockers are held for exercise stress tests, not pharmacologic vasodilator tests.

Reference: Braunwald's Heart Disease, 12th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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