Prolonged ST segment depression after stress testing: Does it really identify more severe disease?

Background: It is generally perceived that the persistence of ST segment depression for more than 5 min after treadmill exercise testing (ETT) signifies a strongly positive test and predicts more severe ischemia and coronary artery disease. Aim: The aim of this study was to determine if prolonged ST segment changes (>5 min) after ETT identifies patients with more severe ischemia and thus severe coronary artery disease. Methods: Twenty five patients (19 males, mean age 58±10 years) with >1 mm ST segment depression and recovery time ≤5 min (group 1) and 25 patients (20 males, mean age 62±10 years) with >1 mm ST segment depression and recovery time >5 min (group 2) undergoing ETT and single photon emission computed tomography were prospectively enrolled. Summed stress and difference scores, stress and reversible extent % of perfusion abnormalities, and lung heart ratio was calculated. Results: There was no significant difference in the mean summed stress score (9±9 versus 13±10, P=0.13), summed difference score (4±3 versus 6±5, P=0.13), stress extent % (14±16 versus 19±13, P=0.13), extent of reversibility % (7±9 versus 7±7, P=0.93), or lung heart ratio (0.48±0.07 versus 0.46±0.07, P=0.50) between the two groups. There was no significant difference in the incidence of severe ischemia (summed difference score >13) in the 2 groups (24% versus 40%, P=0.36). Conclusion: We conclude that utilizing the commonly used cutoff for prolonged ST segment depression: >5 min in recovery, does not identify patients with more severe ischemia or coronary artery disease and, therefore, at increased risk. Thus, it appears unnecessary to give special consideration to these patients by way of prolonged monitoring in recovery, or a more aggressive non-invasive ischemia imaging approach after the ETT.