Introduction

Coronary vasomotor disorders, occurring both at microvascular and epicardial level, can be responsible for myocardial ischemia in a sizeable group of patients undergoing coronary angiography and found to have non-obstructed coronary artery disease (CAD). Intracoronary provocation testing with administration of acetylcholine (ACh) can elicit epicardial or microvascular coronary spasm in susceptible individuals and is therefore fundamental for vasoreactivity evaluation.

Notably, we recently identified some clinical and angiographic predictors of a positive response to ACh provocation testing in patients with non-obstructive CAD, such as acute clinical presentation with myocardial infarction (MI), higher levels of C-reactive protein (CRP) and the presence of myocardial bridging (MB). In this regard, the creation of a clinical risk score able to predict a positive ACh test response based on clinical and angiographic features readily available in the catheterization laboratory could be extremely helpful. Indeed, its implementation could avoid the need for performing the provocation testing, significantly reducing the duration of invasive procedures and the associated albeit limited risks, thus allowing a fast determination of the most appropriate treatments and clinical paths and a parsimonious use of medical resources. Of note, ACh provocation testing is still largely underused in clinical practice, mainly because of perceived concerns regarding the risk of complications, especially in the acute clinical setting. Consequently, the diagnosis of vasomotor disorders is frequently missed, leading to inappropriate medical therapy and a worse outcome. Thus, the identification of patients in whom ACh testing is mostly indicated might facilitate its implementation.

In our study, we aimed to derive and validate a simple risk score to predict a positive ACh test response in a large population of patients presenting with ischemia with non-obstructed coronary arteries (INOCA) or myocardial infarction and non-obstructed coronary arteries (MINOCA).