ESP-INOCA: Rationale and design of a national multicentre registry for prognostic stratification in patients with suspected myocardial ischaemia and non-obstructive coronary arteries.

Introduction: Obstructive coronary artery disease (CAD) has long been recognized as the primary mechanism underlying myocardial ischaemia. However, up to 50 % of patients with angina and objective evidence of ischaemia present with non-obstructed coronary arteries (INOCA) in the coronary angiography, falling under the umbrella term INOCA, a heterogeneous group that remains frequently underdiagnosed and undertreated. Performing a coronary function test (CFT) enables us to diagnose and stratify these patients into different endotypes and start a targeted medical therapy. This study aims to determine the prevalence and long-term clinical outcomes of the different INOCA endotypes through a nationwide registry.

Methods And Results: ESP-INOCA (ClinicalTrials.gov Identifier: NCT06327672) is a Spanish multicentre, observational, longitudinal and prospective registry enrolling patients with chronic coronary syndromes and suspected myocardial ischaemia, referred for invasive coronary angiography. Patients are included if no obstructive CAD is found and a CFT is performed. Endothelium-independent vascular function will be evaluated through the analysis of coronary flow reserve and index of microvascular resistance using the bolus-thermodilution technique. The presence of coronary vasomotor disorders will be assessed by the acetylcholine test. The primary outcome is a composite of all-cause death, acute myocardial infarction, emergency department visits for acute chest pain, hospital admissions for angina or heart failure at one year of follow-up.

Conclusions: This large multicentre registry will provide valuable insights into the long-term prognosis of INOCA endotypes, contributing to improved risk stratification and a better understanding of this heterogeneous clinical entity.