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Harvard Medical School
You will need to sign a consent form giving your doctor permission to perform this test. Tell your doctor if you have ever had an allergic reaction to lidocaine or the numbing medicine used at the dentist's office. Also tell your doctor if you have ever had an allergic reaction to any heart medicines.
Talk with your doctor ahead of time if you are taking insulin, or if you take aspirin, nonsteroidal antiinflammatory drugs, or other medicines that affect blood clotting. It may be necessary to stop or adjust the dose of these medicines before your test. Most people need to have a blood test done some time before the procedure to make sure they are not at high risk for bleeding complications.
Your doctor may tell you not to eat anything for 12 or more hours before the test. A few people require an anti-anxiety medicine, which occasionally causes nausea, and therefore some doctors prefer to have you come with an empty stomach. You might need to plan to spend the night in the hospital afterwards for recovery.