The validity of pharmacologic stress testing and subsequent myocardial perfusion imaging is uncertain in those patients who may have taken caffeine within the 24 hours before testing. For such patients, two new challenge tests have been developed. An intravenous bolus dose of adenosine is given at a dose of 6 mg in a period of 1 or 2 seconds. A physiologic response qualifies the patient to proceed with the scheduled stress test. In the occasional patient who exhibits no pharmacologic symptoms during an infusion test, a similar bolus dose of 6 mg adenosine can validate perfusion tests. These two applications are successful regardless of whether adenosine or dipyridamole infusions are performed. Based on this multicenter experience over 4 years, the authors estimate that 5 to 10 of patients undergoing pharmacologic testing are appropriate candidates for a challenge test.
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