Acetylcholine (ACh) spasm provocation test

The acetylcholine test allows to detect a spasm of the epicardial coronary arteries (the segment of the coronary tree visible at coronarography) or a spasm of the microcirculation (consisting of small vessels, not detectable with the current angiographic methods).

The examination is performed under local anesthesia, from a radial or femoral arterial access and consists in the cannulation generally of the left coronary artery and intracoronary infusion of increasing doses of aceticolin, a vasodilator molecule able to produce, however, a coronary vasoconstriction in patients with an alteration of the endothelium (the inner lining of the arterial wall).

The aceticolin test is of fundamental importance in the diagnosis of variant angina (or Prinzmetal's angina) in which it is spasm of the epicardial coronary arteries that causes anginal symptoms. In these patients, after intracoronary administration of aceticolin, there is narrowing of the coronary lumen associated with the appearance of symptoms and electrocardiogram alterations.

The aceticolin test also allows the identification of patients with microcirculatory spasm. Such patients, after intracoronary administration of aceticolin, present onset of anginal symptoms and electrocardiographic alterations, but no detectable narrowing of epicardial coronary arteries.

In both categories of patients this examination is however diriment in the diagnosis and allows to set an adequate pharmacological therapy with calcium channel blockers.