Background: The ratio of early mitral inflow velocity to early diastolic strain rate (E/e'sr) is a novel echocardiographic measure to estimate early left ventricular (LV) filling pressure. We hypothesize that E/e'sr is a predictor of outcome following coronary artery bypass grafting (CABG) and that it is superior to the conventionally used E/e'. Methods & results: Consecutive patients undergoing isolated CABG at Gentofte Hospital (n = 652) were included. The mean age of the study population was 67 ± 9 years, 84% were male, mean LVEF was 50 ± 11%. Prior to surgery, all patients underwent an extensive echocardiographic examination. The outcome was all-cause mortality. During follow-up (median 3.8 years [IQR: 2.7; 4.9 years]), a total of 73 (11.2%) died. Both E/e' and E/e'sr were significant predictors in univariable models. In a multivariable model, E/e'sr remained an independent predictor of outcome (HR:1.05 [1.01–1.10], p = 0.049, per 10 cm increase) whereas E/e' did not (HR:1.05 [0.99–1.11], p = 0.053, per 1-unit increase). The relationship between E/e'sr, and the outcome was significantly modified by GLS (p for interaction = 0.043). In the multivariable model, E/e'sr was still significantly associated with the outcome in patients with high GLS (≥13.6%) (HR:1.18 [1.02–1.36], p = 0.029) but not in patients with low GLS (HR 1.04 CI95%: [0.99–1.10], p = 0.14). E/e' was not a significant predictor of all-cause mortality after multivariable adjustment in neither of the groups. E/e'sr improved net reclassification with 33% when added to EuroSCOREII. Conclusion: Following CABG, preoperative E/e'sr is an independent predictor of all-cause mortality, especially in patients with preserved systolic function and superior to E/e'.