nPrognostic Value and Interplay between Myocardial Tissue Velocities in Patients Undergoing Coronary Artery Bypass Grafting.
Early diastolic tissue velocity (e’) by tissue Doppler imaging (TDI) represents an early marker of left ventricular (LV) dysfunction in ischemic heart disease. We assessed the value of e’ for predicting mortality in patients undergoing coronary artery bypass grafting (CABG). We retrospectively investigated patients treated with CABG between 2006-2011. Before surgery, all patients underwent an echocardiogram with TDI to measure tissue velocities: systolic (s’), e’, and late diastolic (a’). The primary outcome was all-cause mortality. Survival analysis was applied. Improvement of EuroSCORE-II was assessed by net reclassification index. Of 660 patients, 72 (11%) died during a median follow-up time of 3.8 years. Mean age was 68 years, LVEF 50%, and 84% were men. All tissue velocities showed a significant negative association with outcome and e’ provided highest Harrell’s C-statistics (c-stat=0.68). After multivariable adjustment for EuroSCORE-II, LV hypertrophy, LV internal diameter, and global longitudinal strain, declining e’ was associated with a higher risk of mortality (HR=1.35 (1.12-1.61), p=0.001, per 1cm/s absolute decrease). LVEF≤40% modified the relationship between both s’ and e’ and outcome (p for interaction=0.021 and 0.024, respectively), such that neither predicted mortality when LVEF was ≤40%. In patients with LVEF>40%, only e’ remained a predictor after multivariable adjustments (HR=1.36 (1.10-1.69), p=0.005, per 1cm/s absolute decrease). A net reclassification index improvement of 14% was observed when adding global e’ to the EuroSCORE-II. In conclusion, e’ is an independent predictor of all-cause mortality in patients undergoing CABG, especially in patients with LVEF>40%, and improves the predictive value of EuroSCORE-II.