Table 2.

Practical Considerations for Invasive Assessment of Coronary Vascular Function

Procedure	Practical Points
Set-up	Acetylcholine may be pre-ordered, according to local arrangements.
	Obtain informed consent.
	Undertake team briefing on indication and protocol.
	Administer heparin 5,000 IU (as per local standard care procedures).
	Use radial artery access; avoid administration of vasodilator drugs, as they may confound measurement of coronary vascular function.
	Administer short-acting intra-arterial GTN (avoid verapamil/GDN).
	Use a 5-F guide catheter to reduce spasm in small radial arteries.
Coronary angiography
Projection	Choose an imaging projection that reveals the long axis of the target vessel (i.e., no foreshortening), with minimal vessel overlap.
TIMI frame count	Ensure that cine acquisition is sufficiently long to assess for myocardial blush of contrast media.
Diagnostic guidewire	A single target coronary artery may be sufficient for diagnosis and decision making; in general, select the left anterior descending coronary artery.
	If normal results are obtained and clinical suspicion remains high, consider undertaking the IDP in a second coronary artery.
	Advance the guidewire into the distal third of the target coronary artery.
ComboWire Doppler	Consider using a buddy wire to safely advance the ComboWire.
Coronary reactivity testing	Avoid a vasodilator cocktail in radial procedures.
	Retain the buddy wire in situ to facilitate direct intracoronary testing.
	A dedicated intracoronary catheter is generally not necessary (and may increase the risks of the procedure); injection of acetylcholine is done through the guiding catheter into the lumen of the left main coronary artery. Prior to starting the infusion of acetylcholine, initially flush the lumen of the guide with ∼2 ml of the infusate (depending on the French size of the catheter used) to replace the flushing saline in the shaft of the catheter. Once the acetylcholine solution has reached the tip of the catheter, further injection is done more slowly and steadily over 20 s. The catheter is then slowly refilled with saline, remembering that this procedure will lead to extrusion of acetylcholine at the tip of the catheter for at least as long until all the acetylcholine solution is replaced by saline.
	If infusing into a “dominant” coronary artery, consider “half dose” of the acetylcholine to limit bradycardia.
	In cases with normal coronary function or “negative” test responses, if clinical suspicion persists, a dose of 200 μg may be infused into the left coronary artery, increasing sensitivity without impairment of specificity.
	Use isosorbide dinitrate, which has short-acting effects, unlike GTN.

GDN = glyceryl dinitrate; GTN = glyceryl trinitrate; IDP = interventional diagnostic procedure.