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Since the inaugural description in 1959 by Prinzmetal,1 coronary artery spasm and abnormal coronary artery vasomotion have been extensively studied both clinically and scientifically. There is no doubt that abnormal epicardial and microvascular coronary vasomotion play an important role in ischaemic heart disease. However, after the introduction of percutaneous coronary intervention, the number of articles and the clinical interest in abnormal coronary vasomotion have declined considerably, at least in the USA and Europe. As a consequence, the functional aspects of coronary artery disease have received less and less attention. There has been a revival of the topic recently, mainly because abnormal coronary vasomotion of the microcirculation has come into focus,2 but also because the clinical presentation of chest pain with unobstructed coronary arteries continues to represent a diagnostic challenge for the clinician.3
In this article we describe common patterns of coronary vasomotor responses to intracoronary acetylcholine provocation testing which may be helpful for interventionalists who plan to start an intracoronary functional testing programme.
Intracoronary acetylcholine provocation testing
Acetylcholine is a transmitter of the parasympathetic nervous system and acts via nicotinic and muscarinic receptors. Muscarinic acetylcholine receptors (mAchR) play a key role in vascular homeostasis. Acetylcholine binds on mAchR in a non-selective way as an agonist. Activation of vascular endothelial mAchR leads to nitric oxide mediated vasodilatation whereas activation of vascular smooth muscle mAchR leads to vasoconstriction. Depending on the integrity of the endothelium and the reagibility of the vascular smooth muscle cells, the net effect of intracoronary acetylcholine administration can be vasodilatation or severe constriction and spasm.4 It should be noted that ∼25% vasoconstriction as compared to baseline in response to higher intracoronary acetylcholine doses may still be within the range of normal responses, as such a reaction can be observed in patients with angiographically normal coronary arteries without chest …
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