ReACHallenge Trial: Acetylcholine Rechallenge After Pretreatment With Vasoactive Drugs (ReACHallenge)

Inclusion Criteria: Clinically indicated coronary angiogram in the setting of angina with non-obstructive coronary artery disease (ANOCA) Non-obstructive coronary artery disease is defined as the absence of coronary artery stenosis ≥ 50%, or if ≥ 50% with non-ischemic resting (RFR > 0.89) and hyperemic indices (FFR > 0.80). ACH provoked epicardial and/or microvascular spasm Left ventricular ejection fraction (LVEF) > 50% Renal function with eGFR ≥ 40 ml/min Exclusion Criteria: Obstructive coronary artery disease (both chronic and acute coronary coronary syndromes) Any cardiomyopathy (including takotsubo stress cardiomyopathy) or severe valvular disease LVEF < 50% Long QT syndrome (LQTS) - genetic or acquired Ventricular paced rhythm Renal failure with eGFR < 40 ml/min Thyroid stimulating hormone (TSH) < lower limit of normal (LLN). A subject taking thyroid replacement therapy may be enrolled with TSH level below LLN if, in the opinion of the investigator, the subject is in a clinically euthyroid state. Known hypersensitivity or contra-indication for either acetylcholine, verapamil, nicorandil or nitroglycerine. Pregnant female subjects. Female subjects of child-bearing potential should be on adequate contraceptive measures or are to be screened with a urine pregnancy test.