Post-spastic flow recovery time to document vasospasm induced ischemia during acetylcholine provocation testing

Intracoronary acetylcholine (ACh) provocation is an established method for diagnosing epicardial and microvascular vasospasm in contemporary clinical practice. We hypothesize that ACh-induced vasospasm is followed by post-spastic reactive hyperemia (PSRH), which is measured as an increased flow-recovery time. To assess flow-recovery time, indicative of ischemia, among the diagnostic endotypes that follow ACh provocation testing. Patients with angina and non-obstructive coronary artery disease on angiography who underwent ACh provocation testing were included in this analysis. Doppler flow was continuously measured during the procedure and used to determine the flow-recovery time, which was calculated as time between cessation of ACh infusion and the point of flow recovery. Conventional provocation testing according to the COVADIS criteria diagnosed vasospasm in 63%(77/123), an equivocal result in 22%(27/123) and a negative result in 15%(19/123) of patients. In reaction to the highest-dose of ACh, flow-recovery time was significantly extended and similar in the epicardial, microvascular and equivocal test results compared to the negative result (all p < 0.001) indicative of PSRH. Flow-recovery time in patients with an equivocal result is similar to patients with vasospasm, which indicates the occurrence of myocardial ischemia and therefore, these patients may benefit from medical treatment.