Characterization and implications of intracoronary hemodynamic assessment during coronary spasm provocation testing

Background: Current diagnostic criteria for coronary spasm are based on patient's symptoms, ECG shifts and epicardial vasoconstriction during acetylcholine (ACh) spasm testing.

Aims: To assess the feasibility and diagnostic value of coronary blood flow (CBF) and resistance (CR) assessment as objective parameters during ACh testing.

Methods: Eighty-nine patients who underwent intracoronary reactivity testing including ACh testing with synchronous Doppler wire-based measurements of CBF and CR were included. Coronary microvascular and epicardial spasm, respectively, were diagnosed based on COVADIS criteria.

Results: Patients were 63 ± 13 years old, predominantly female (69%) and had preserved LV ejection fraction (64 ± 8%). Overall, assessment of CBF and CR during ACh testing revealed a decrease in CBF of 0.62 (0.17-1.53)-fold and an increase of CR of 1.45 [0.67-4.02]-fold in spasm patients compared to 2.08 (1.73-4.76) for CBF and 0.45 (0.44-0.63) for CR in patients without coronary spasm (both p < 0.01). Receiver operating characteristic revealed a high diagnostic ability of CBF and CR (AUC 0.86, p < 0.001, respectively) in identifying patients with coronary spasm. However, in 21% of patients with epicardial spasm and 42% of patients with microvascular spasm a paradoxical response was observed.

Conclusions: This study demonstrates feasibility and potential diagnostic value of intracoronary physiology assessments during ACh testing. We observed opposite responses of CBF and CR to ACh in patients with positive vs. negative spasm test. While a decrease in CBF and an increase in CR during ACh seem pathognomonic for spasm, some patients with coronary spasm demonstrate paradoxical ACh response demanding further scientific investigations.