Editing Cardiac stress test (section)

== Use of pharmacological agents to stress the heart ==
Pharmacologic stress testing relies on [[coronary steal]]. Vasodilators are used to dilate coronary vessels, which causes increased blood velocity and flow rate in normal vessels and less of a response in stenotic vessels. This difference in response leads to a steal of flow and perfusion defects appear in cardiac nuclear scans or as ST-segment changes.<ref name="Medscape: Pharmacologic Stress Testing 2021">{{cite journal |last=Akinpelu |first=David |date=17 October 2021 |title=Pharmacologic Stress Testing: Background, Indications, Contraindications |url=https://emedicine.medscape.com/article/1827166-overview |access-date=26 March 2022 |website=Medscape Reference}}</ref>

The choice of pharmacologic stress agents used in the test depends on factors such as potential drug interactions with other treatments and concomitant diseases.

Pharmacologic agents such as adenosine, regadenoson (Lexiscan), or dipyridamole is generally used when a patient cannot achieve adequate work level with treadmill exercise, or has poorly controlled [[hypertension]] or left [[bundle branch block]]. However, an exercise stress test may provide more information about exercise tolerance than a pharmacologic stress test.<ref name="WeissmanAdelmann2004">{{cite book|last1=Weissman|first1=Neil J.|last2=Adelmann|first2=Gabriel A.|title=Cardiac imaging secrets|url=https://books.google.com/books?id=TTWdpgTFU9cC&pg=PA126|access-date=25 September 2011|year=2004|publisher=Elsevier Health Sciences|isbn=978-1-56053-515-7|pages=126–}}</ref>

Commonly used agents include:
* [[Vasodilators]] acting as [[adenosine receptor]] agonists, such as [[adenosine]] itself, and [[dipyridamole]] (Persantine),<ref name="NichollsWorthley2011">{{cite book|last1=Nicholls|first1=Stephen J.|last2=Worthley|first2=Stephen|title=Cardiovascular Imaging for Clinical Practice|url=https://books.google.com/books?id=JUDJp7DFpxUC&pg=PA198|access-date=25 September 2011|date=January 2011|publisher=Jones & Bartlett Learning|isbn=978-0-7637-5622-2|pages=198–}}</ref> which acts indirectly at the receptor.
* [[Regadenoson]] (Lexiscan), which acts specifically at the [[adenosine A2A receptor]], thus affecting the heart more than the lung.
* [[Dobutamine]]{{snd}} The effects of [[beta-agonist]]s such as dobutamine can be reversed by administering [[beta-blocker]]s such as [[propranolol]].

Regadenoson or dobutamine is often used in patients with severe [[reactive airway disease]] ([[asthma]] or [[COPD]]) as adenosine and dipyridamole can cause acute exacerbation of these conditions. If the patient's asthma is treated with an inhaler then it should be used as a pre-treatment prior to the injection of the pharmacologic stress agent. In addition, if the patient is actively wheezing then the physician should determine the benefits versus the risk to the patient of performing a stress test especially outside of a hospital setting. [[Caffeine]] is usually held 24 hours prior to an adenosine stress test, as it is a competitive antagonist of the A2A adenosine receptor and can attenuate the vasodilatory effects adenosine.{{citation needed|date=March 2021}}

[[Aminophylline]] may be used to attenuate severe and/or persistent adverse reactions to adenosine and regadenoson.<ref>{{Cite journal |last1=Abidov |first1=Aiden |last2=Dilsizian |first2=Vasken |last3=Doukky |first3=Rami |last4=Duvall |first4=W. Lane |last5=Dyke |first5=Christopher |last6=Elliott |first6=Michael D. |last7=Hage |first7=Fadi G. |last8=Henzlova |first8=Milena J. |last9=Johnson |first9=Nils P. |last10=Schwartz |first10=Ronald G. |last11=Thomas |first11=Gregory S. |last12=Einstein |first12=Andrew J. |date=2018-12-20 |title=Aminophylline shortage and current recommendations for reversal of vasodilator stress: an ASNC information statement endorsed by SCMR |journal=Journal of Cardiovascular Magnetic Resonance |volume=20 |issue=1 |page=87 |doi=10.1186/s12968-018-0510-7 |doi-access=free |issn=1097-6647 |pmc=6300896 |pmid=30567577}}</ref>