Role of electrocardiographic stress testing in ANOCA

When a person with positive treadmill exercise ECG is shown to have normal epicardial coronary arteries on coronary angiography, the treadmill ECG is often branded as a false positive test. But this may not be the case if the coronary microvascular function is also evaluated. Patients having angina with nonobstructive coronary arteries (ANOCA) were enrolled in a study for assessment of coronary microvascular function and exercise ECG. Those with ANOCA having fractional flow reserve >0.80 and preserved left ventricular ejection fraction >50% were included in the study. Of the 160 patients who underwent coronary angiography with physiological assessment, 120 underwent exercise ECG stress test by standard Bruce protocol. Of these 20 more were excluded for various reasons. Finally, of the 102 patients recruited for the study, 32 had ischemic ischemic ST segment response [1].

Endothelium-independent microvascular function was assessed using intravenous adenosine. This was followed by assessment of endothelium-dependent microvascular function using graded intracoronary infusion of acetylcholine via guide catheter. The study authors noted that ischemia during exercise stress test had 100% specificity for detecting coronary microvascular dysfunction in patients with ANOCA. Endothelium dependent microvascular dysfunction was the strongest predictor of ischemia during exercise. Learning point is that positive treadmill exercise test in the absence of obstructive coronary artery disease should not be just discarded as false positive. Coronary microvascular function assessment has to be included in the evaluation of such persons.

Reference

1. Sinha A, Dutta U, Demir OM, De Silva K, Ellis H, Belford S, Ogden M, Li Kam Wa M, Morgan HP, Shah AM, Chiribiri A, Webb AJ, Marber M, Rahman H, Perera D. Rethinking False Positive Exercise Electrocardiographic Stress Tests by Assessing Coronary Microvascular Function. J Am Coll Cardiol. 2024 Jan 16;83(2):291-299. doi: 10.1016/j.jacc.2023.10.034. PMID: 38199706; PMCID: PMC10790243.