Determining the Cause of Coronary Vasomotor Disorders in Patients With Ischemia and Nonobstructive Coronary Arteries: Design and Rationale of the DISCOVER INOCA Prospective, Multicenter Registry

Background: Approximately 30% to 50% of patients who are referred for diagnostic coronary angiography are found to have no obstructive coronary artery disease (CAD). Ischemia and nonobstructive coronary arteries (INOCA) is increasingly recognized and encompasses coronary microvascular dysfunction, vasospastic angina, symptomatic myocardial bridging, and other vasomotor disorders. However, the prevalence of these disorders and whether underlying atherosclerotic plaque burden and morphology affect the long-term outcomes of each physiologic phenotype is unknown.

Methods: The DISCOVER INOCA registry is ongoing at 8 centers in the United States and plans to enroll 500 patients with ischemic heart disease referred for angiography undergoing coronary function testing (CFT). All participants will complete patient-reported outcome measures and undergo protocol-guided angiography, acetylcholine provocation, coronary thermodilution, and intravascular imaging. Follow-up assessments occur at 30 days, 6 months, 1 year, and annually for 5 years. The primary short-term end point is the prevalence of INOCA phenotypes based on physiology and the degree of atherosclerosis based on intravascular ultrasound or optical coherence tomography (intravascular imaging). The primary long-term end point is the incidence of major adverse cardiovascular events, defined as a composite of cardiovascular death, myocardial infarction, hospitalization for cardiovascular causes, or coronary revascularization at a follow-up of 5 years. At the time of this publication, 100 participants have been enrolled.

Conclusions: DISCOVER INOCA is the first prospective study of INOCA patients to integrate anatomic and physiologic measures of disease and correlate them with long-term outcomes. DISCOVER INOCA will report on the prevalence of INOCA phenotypes, the safety of comprehensive invasive CFT, and the impact of testing on diagnoses and medical therapy. Symptoms and cardiovascular adverse events at long-term follow-up will be determined in patients with no obstructive CAD undergoing angiography.