Vasospastic angina (VSA) occurs at rest and on exertion, with transient electrocardiographic ischemic changes. VSA presents with spontaneous coronary artery spasm (CAS); it has been associated with stable angina, acute coronary syndromes, and sudden cardiac death. CAS can be identified in normal arteries or non-obstructive coronary atherosclerosis, but is also prevalent in patients with coronary artery disease. The diagnosis is made with invasive coronary reactivity testing with provocation using acetylcholine (Ach). Epicardial spasms can be visualized through coronary angiography as a reversible epicardial vessel narrowing, while the diagnosis of microvascular spasm can be made when angina symptoms and ECG changes happen following intracoronary Ach without epicardial spasm. Identification of CAS allows for risk stratification and specific therapies targeting endothelial dysfunction and paradoxical vascular smooth muscle cell constriction. Therapies include calcium channel blockers as monotherapy or in a combination of a dihydropyridine and non-dihydropyridine. Short-acting nitrates offer acute symptomatic relief but long-acting nitrates should be used sparingly. This current update on invasive evaluation of VSA discusses unified Ach protocols.