BACKGROUND:Non-traditional EKG parameters such as QRS pattern and QRS duration (QRSd) are being investigated in acute coronary syndrome as prognostic markers. Following an infarction, the heart attempts to compensate for myocardial loss through remodeling which eventually lowers the ejection fraction (LVEF). Our objective is to evaluate the relationship between the QRSd at the time of NSTEMI and extent of coronary artery disease (CAD) and changes in LVEF. METHODS AND RESULTS:Patients admitted with NSTEMI between 08/01/2006 and 9/30/2012 were included. Patients were classified into high or low QRSd at cutoff value of 90ms noted on initial EKG after excluding bundle-branch block. A total of 536 patients with mean age of 66±14years were included. 49% were male and majority were African American (73%). Patients within the higher QRSd group had a lower LVEF at the time of the NSTEMI compared to those with QRSd <90ms (47±15% vs. 50±13%; p<0.038). The LVEF remained lower in the high QRS group on follow up to 12months (47±15% vs. 52±11%; p<0.001). The high QRSd group had a higher incidence of severe LV dysfunction at baseline (27% vs. 18%; p<0.045). Logistic regression analysis revealed that a QRSd ≥90ms was also independently associated with a severely reduced LVEF on follow-up (OR=2.7; CI 1.55-4.69; p<0.001). CONCLUSION:QRSd ≥90ms at the time of NSTEMI is predictive of three-vessel/left main coronary artery involvement and a lower LVEF. This depression in LVEF is maintained for up to 12months. Thus, the QRSd at time of NSTEMI has additional prognostic significance.