Although the risk for adverse effects due to stress testing is low, it is not nonexistent. In many facilities the patient is asked to sign a consent form prior to the procedure. A sample consent form for stress testing is shown in the accompanying box.
Cardiovascular Nuclear Imaging and Exercise Laboratory
Consent for Stress Testing I am scheduled to undergo a cardiac stress test. I understand that this test involves walking or running on a treadmill. I understand that this test involves the infusion of a medication that stresses the heart.
During the test I will be watched for symptoms and monitored by an electrocardiogram. In addition heart rate and blood pressure measurements will be taken.
I understand that certain complications may occur including, but not limited to, heart attack, heart rhythm abnormality, stroke and death. I also understand that physical trauma may be incurred during the performance of the test. The general purpose, potential benefits, possible hazards and inconveniences of stress testing have been explained to my satisfaction and I have been given the opportunity to ask any questions that I have concerning the test. I hereby consent to the performance of the test.
Patient signature Patient print name
Responsible physician signature Responsible physician print name
If a patient states that she is, or may be, pregnant or that she is breastfeeding, a radionuclide imaging study can only be performed after consulting with the RSO and the medical director. All benefits and risks must be weighed and discussed with the patient before proceeding with the procedure. The discussion should be documented in writing.
PREPARATION FOR EXERCISE/STRESS PROTOCOLS
Stress Tc-99m-Agent (Tc-99m-Sestamibi or Tc-99m-Tetrofosmin) First
• No coffee or caffeine-containing drinks or food can be ingested during the 12 h prior to the scheduled test.
• Patients are allowed to drink fruit juices, white milk, or water.
• Patients should be off theophylline-based medications for 48 h prior to the test. This should be done in consultation with the referring physicians
The reason for these instructions is that caffeine is a specific blocker of adenosine receptors and makes dipyridamole or adenosine infusion ineffective and will likely result in false-negative tests. (See Table 4-1.) It is not rare that a patient's exercise capacity is overestimated and they need to be switched to pharmacological stress. Therefore, as noted previously, it is advisable to give the same instruction about abstinence of caffeine-containing beverages and food to all scheduled patients.
• Patients should continue their other medications unless directed otherwise by their physician.
Rest Tc-99m-Agent (Tc-99m-Sestamibi or Tc-99m-Tetrofosmin) First
• The instructions are the same as for the "stress-first" procedure. However, the patients may eat a light breakfast or a light lunch if time permits before rest study. Patients should be NPO 4 h prior to stress.
• Patients should be off theophylline-based medications for 48 h following their physicians advice.
• Prior to the test the instructions are the same as for the "stress-first" procedure.
• Between the stress and redistribution part of the procedure, the patient may take liquids but no solid food. Caffeine is allowed after the stress portion. Diabetics may eat a light meal if needed.
The reason for this instruction is that ingestion of food after stress inhibits the redistribution of Tl-201and defects may appear falsely fixed.
Dual Isotope Rest-Thallium Stress-Tc-99m-Agent (Tc-99m-Sestamibi or Tc-99m-Tetrofosmin) Imaging
• The instructions are the same as for the "rest-first" procedure. The patients may eat a light breakfast or a light lunch if time permits before Rest study. Patients should be NPO 4 h prior to stress.
Caffeine-Containing Beverages, Food and Medications that Compete with Adenosine Receptor Sites
Coffee (including "decaffeinated" coffee) Tea
Sodas (including regular, diet and "caffeine free" beverages) Chocolate drinks and chocolate products Medications (partial list) Anacin® Exedrin®)
Cold combination medication (Kolephrin)
Goody's headache powder
Oxtriphylline (Choledyl®) Aminophylline®
Patients should be off theophylline-based medications for 48 h following their physicians advice.
In a well-run facility details of all procedures and policies are described in written protocols to ensure standardization and consistency of daily operations. Since no imaging facility operates under identical circumstances, protocols must be modified to meet specific needs. In order to meet standards for accreditation by the ICANL, for example, well-detailed "laboratory-specific protocols" play an important role (See Chapter 18 and on line: www.icanl.org). This chapter discusses:
• Indications and methodology
• Physical exercise testing
• Pharmacological stress testing
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