96 Stress echocardiography sured using 2D speckle tracking. Functional capacity was assessed with a treadmill stress test and expressed as metabolic equivalents (METs). We analyzed left atrial strain values with functional capacity through linear correlations (Bonferroni type adjustment). Results: In our group of patients, the relationship between left atrial ejection fraction and METs were not shown to be significant (r=0.11, p=0.34), but atrial strain values were significant predictors of

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... tional capacity. Left atrial strain was significantly related to the diastolic patron, assessed by E/E' valor (r= -0.26, p=0.0269). We found a direct proportional relationship between peak atrial strain measured during the left atrial reservoir phase and METs (r=0.55, p<0.001) and an inverse relationship between the strain rate measured during the conduit phase and METs (r= -0.55, p<0.001). In our sample, we did not find any statistically significant association between E/E' rest with exercise capacity (r= -0.17, p=0.146). Conclusion: In our preserved left ventricular function group of patients, left atrial function assessed with speckle tracking was a significant predictor of functional capacity, better than left atrial ejection fraction or E/E' rest. P559 | BEDSIDE The aVR lead ST-segment elevation during the exercise stress test as a predictor of a left main stenosis Background: ST-segment elevation in lead aVR is an important predictor of acute left main (LM) coronary artery obstruction, but its predictive value in a setting of exercise treadmill testing is still unclear. Purpose: The aims of our study were to assess the incidence and predictors of LM/ostial left anterior descending (LAD) coronary artery and/or ostial circumflex (Cx) artery stenosis in patients referred to exercise testing presenting with exercise-induced ST segment elevation in lead aVR. Methods: Out of 9052 patients who underwent stress echocardiography testing from 2012 to 2016 in our laboratory, we identified 76 patients (55 men; mean age of 61±8.4 years), presenting with ST segment elevation in lead aVR during exercise. All the patients underwent coronary angiography. Significant LM/ostial LAD or ostial Cx stenosis was defined as narrowing ≥50% of diameter stenosis. We analyzed baseline clinical characteristics, hemodynamic response to exercise, rest and stress electrocardiograms as well as baseline and peak exercise echocardiography images in all patients. We calculated Duke treadmill score and changes in wall motion score index (delta WMSI). Results: Significant LM/ostial LAD or ostial Cx stenosis was present in 26/76 patients (34%) with exercise-induced ST segment elevation in lead aVR. There were no statistically significant differences in majority of baseline clinical characteristics and hemodynamic response between patients with and without significant LM/ostial LAD or ostial Cx stenosis. However, patients with LM/ostial LAD and ostial Cx stenosis were older (63±8 years vs. 60±9 years, p=0.19), with a lower Duke treadmill score (-7±6 vs. -3±4, p=.004) in comparison to those without significant LM/ostial LAD or ostial Cx stenosis, and the showed more severe wall motion abnormalities with exercise (delta WMSI 0.61±0.32 vs. 0.40±0.27, p=0.022). Sensitivity of Duke score ≤-5 in detection of significant LM/ostial LAD or ostial Cx stenosis was 65%, with specificity of 68% (AUC 0.706). Patients with aVR lead elevation accompanied by ST-segment depression in leads V3-V6, are most likely to have significant LM/ostial LAD/ or ostial Cx stenosis (p=0.023) in conjunction with ST depression in leads D2, D3, aVF. Conclusions: ST-segment elevation in lead aVR has limited sensitivity in a detection of significant LM/ostial LAD or/and ostial Cx stenosis. Nevertheless, if aVR elevation is accompanied by ST-segment depression in leads V3-V6, patients are most likely to have significant LM/ostial LAD or/and ostial Cx stenosis. Additionally, the Duke treadmill score can be calculated to help identify this subset of patients.