Which medications are used to perform pharmacologic stress testing for cardiac assessment?

Updated: Nov 20, 2018
  • Author: Richard S Krause, MD; Chief Editor: Barry E Brenner, MD, PhD, FACEP  more...
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Answer

For patients unable to exercise, pharmacologic agents are used to stress the myocardium and produce the characteristic electrocardiographic (ECG) or nuclear imaging findings. Pharmacologic stress testing is indicated for patients who would be unable to adequately perform an exercise stress test. An exercise test is considered inadequate when a patient cannot either reach 85% of the predicted maximum heart rate or achieve a workload of 5 metabolic equivalents of task (METs) for 3 minutes. A pharmacologic test is preferred over an exercise test in patients with aortic stenosis, left bundle branch block, a paced rhythm, recent myocardial infarction (MI), and severe hypertension, even if they were able to exercise adequately. [20]

Adenosine, regadenoson and dipyridamole are coronary vasodilators. In terms of blood flow, normal vessels are up to 400% more responsive to the vasodilatory effect than stenotic vessels. This difference in response leads to differential flow, and perfusion defects appear in cardiac nuclear imaging or as ST-segment changes on the ECG.

Contraindications to adenosine use include active asthma, high-grade heart block, and hypotension. Caffeine or theophylline should be stopped 12 hours before adenosine is given. Regadenoson and dipyridamole have similar contraindications (although studies have indicated that regadenoson is relatively safe in patients with asthma). [21] In addition, in November 2013, the US Food and Drug Administration (FDA) issued a warning that regadenoson and adenosine should not be used for cardiac nuclear stress tests in patients with signs or symptoms of unstable angina or cardiovascular instability, because these drugs may increase the risk for a fatal heart attack. [2, 3]

Dobutamine is a direct cardiac inotrope and chromotrope. It consequently increases myocardial oxygen demand similar to exercise and allows ischemic areas to become visible on nuclear scanning or apparent as ST depression on the ECG.

Dobutamine contraindications include hemodynamically significant left ventricular outflow tract obstruction, tachyarrhythmias (including prior history of ventricular tachycardia), uncontrolled hypertension (blood pressure > 200/110 mmHg), aortic dissection, or large aortic aneurysm. Beta-blockers should be discontinued so that the response to dobutamine will not be attenuated.


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