ANOCA and INOCA: Non-Invasive Diagnosis of Chronic Coronary Artery Disease

Medical research continues to refine the understanding of chest pain in patients who do not exhibit obstructive coronary artery disease. New data and updated clinical guidelines are highlighting the significance of Angina with non-obstructive coronary arteries (ANOCA) and Ischaemia with non-obstructive coronary arteries (INOCA).

According to a correspondence published in The Lancet on April 11, 2026, ANOCA and INOCA are identified as important causes of chest pain. These conditions are associated with a decrease in the quality of life for patients and an increase in mortality.

The prevalence of these conditions is significant in clinical settings. Data from the Inclusive Invasive Physiological Assessment in Angina Syndromes registry indicates that ANOCA accounted for 20% of patients who were referred for invasive coronary angiography following a positive stress test.

Understanding ANOCA and INOCA

ANOCA and INOCA describe scenarios where patients experience symptoms of myocardial ischaemia—such as effort or rest angina and exertional dyspnoea—despite the absence of obstructive coronary artery disease. Obstructive CAD is typically defined as a diameter reduction of 50% or more, or a fractional flow reserve (FFR) of 0.

The European Association of Percutaneous Cardiovascular Interventions (EAPCI) notes that patients with these conditions present a wide spectrum of signs and symptoms. Because these symptoms may not align with traditional obstructive patterns, they are often misdiagnosed as non-cardiac, which can lead to under-investigation and under-treatment.

Diagnostic Pathways and Guidelines

The 2024 European Society of Cardiology (ESC) guidelines for chronic coronary syndromes provide specific recommendations for managing these patients. To confirm or exclude the diagnosis of obstructive CAD or INOCA in individuals with an uncertain diagnosis from non-invasive testing, the ESC provides a Class 1B recommendation for invasive coronary angiography combined with invasive functional testing.

Invasive functional testing focuses on assessing the coronary microcirculation. Key diagnostic parameters include the index of microcirculatory resistance (IMR) and coronary flow reserve (CFR).

The COVADIS group has provided standardized criteria for identifying coronary microvascular dysfunction (CMD), which characterizes these conditions. These criteria include:

• A coronary flow reserve (CFR) of less than 2.5.
• An index of microcirculatory resistance (IMR) of 25 or greater.

The Role of Non-Invasive Testing

While invasive procedures are the gold standard for confirmation, non-invasive tools remain critical in the initial diagnostic pathway. Exercise electrocardiography stress testing (EST) has been analyzed for its utility in suspected ANOCA/INOCA cases.

Research suggests that while EST has a limited ability to confirm the presence of underlying microvascular disease, it possesses a high negative predictive value. This makes it a valuable tool for ruling out the conditions in certain patients.

The goal of these diagnostic efforts is to move toward tailored treatment. Evidence indicates that applying treatment based on a specific diagnosis improves both the symptoms and the overall quality of life for patients suffering from myocardial ischaemia with non-obstructive coronary arteries.