Omnipaque 350 injection

Following a diagnostic coronary angiography without administration of nitroglycerin, pressure measurements were performed using a pressure wire (PressureWire, PressureWire, Abbott, USA). Aortic pressure at the tip of the guiding catheter and at the tip of the pressure wire was equalized. The pressure wire was then advanced to the distal part of the coronary artery. Pressure at the distal site and mean aortic pressure were simultaneously recorded, followed by OCT imaging. A frequency domain OCT catheter (ILUMIEN, Abbot Vascular, Santa Clara, California, USA, or FastView, Terumo, Tokyo, Japan) was advanced distally to the lesion. An X-ray contrast medium (Omnipaque 350 Injection, Daiichi Sankyo Co, Ltd, Tokyo, Japan) was infused through the guiding catheter at 2–4 mL/s for approximately 3–6 s using an injector pump (Mark V; Medrad, Pennsylvania, USA), followed by pullback of the OCT imaging probe at 10–40 mm/s to obtain the image of the coronary artery. To confirm the precise site of the spasm, the provocation test was performed with incremental doses of acetylcholine or ergometrine, as recommended in the guideline^{4 (link)}. After administration of nitroglycerin, OCT imaging was repeated. All OCT images were digitally stored and analyzed using Image J (National Institute of Health, Bethesda, MD, USA).