ReACHallenge Trial: Acetylcholine Rechallenge After Pretreatment With Vasoactive Drugs

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.