Global Longitudinal Strain Response to Exercise ECG test As a Predictive Tool to Exclude Coronary Artery Disease in Patients with Suspected Unstable Angina

Background: In patients with suspected unstable angina, normal troponin, and a nondiagnostic ECG, excluding obstructive coronary artery disease without invasive angiography remains difficult. This study assessed whether global longitudinal strain (GLS) measured immediately after exercise adds diagnostic value beyond standard post-exercise echocardiographic indices.Methods: In this prospective, single-center diagnostic case-control study, 200 adults undergoing invasive coronary angiography for suspected unstable angina underwent resting echocardiography, treadmill exercise ECG, and speckle-tracking imaging obtained immediately after exercise. Significant obstructive coronary artery disease (CAD) was defined as ≥70% diameter stenosis of a major epicardial vessel; 100 patients met this criterion and 100 did not.Results: The groups were similar at baseline apart from higher resting blood pressures among those with obstructive CAD. Exercise-induced ST depression occurred in 45.0% of the obstructive-CAD group versus 32.0% of controls. Resting GLS did not differ between groups, but immediate post-exercise GLS was significantly less negative among patients with obstructive CAD (-19.5 ± 2.6% vs. -22.5 ± 2.2%; p < 0.001) and showed the highest diagnostic accuracy of the parameters examined (AUC 0.89; 95% CI 0.83-0.95), surpassing wall motion score index (AUC 0.81) and ejection fraction (AUC 0.72). It remained independently associated with obstructive CAD on multivariable analysis (adjusted OR 1.58; p < 0.001) and improved classification beyond exercise ECG alone (NRI 0.62; IDI 0.14), with high reproducibility (ICCs 0.92 and 0.88).Conclusions: Immediate post-exercise GLS was the strongest discriminator of obstructive CAD among the indices studied and may complement exercise ECG in troponin-negative patients with suspected unstable angina.