L. Carr 1,∗, A. Camuglia 1, M. Dooris 1, A. Lo1, J. Atherton1, S. Prasad1,2 1 Royal Brisbane and Women’s Hospital, Brisbane, Australia 2 Mater Adult Hospital, Brisbane, Australia Background: The E/E′ ratio has an established role in the assessment of left ventricular filling pressures (LVFP) in stable patients. Patients with acute coronary syndrome (ACS) were excluded from the original studies, therefore it is unknownwhether the E/E′ ratio is a robustmeasure of LVFP in this subgroup. We sought to perform an invasive haemodynamic validation study with near-simultaneous measurement of Doppler echocardiographic parameters and invasivelymeasured LVFP in patientswithNSTEACS. Methods: A total of 20 unselected patients with NSTEACs underwent a limited transthoracic echocardiogram immediately prior to cardiac catheterisation. Mitral inflow E-wave and tissue Doppler derived E′ at the septal mitral annulus was measured. Invasive measurement of LVFP was then performed with a pigtail catheter in mid shallow expiration. Pre-A wave left ventricular diastolic pressure (pre-A LVDP) for five consecutive cycles was recorded and averaged. Results: The mean age of patients was 64.1 years, with 72% males. All patients had Troponin+ve ACS. The mean LVEF was 52%. Angiographic findings included threevessel disease in 12.5% and LAD culprit lesions in 25%. Univariate linear regression showed septal E/E′ had a significant association with pre-A LVDP (p= 0.004). Multivariate linear regression showed septal E/E′ to be an independent predictor of pre-A LVDP (p= 0.003). A septal E/E′ cut-off of 12 identified all cases of pre-A LVDP >12mmHg. ROC analysis showed that the septal E/E′ had an AUC of 0.91 for predicting pre-A LVDP. Conclusions: Septal E/E′ ratio is a valid non-invasive assessment of elevated filling pressures in patients with NSTEACS.