Background: Previous studies have shown that prolonged QRS duration increases the risk of death in patients with heart failure and after an ST-segment elevation acute myocardial infarction. Very little data exist about the prognostic implications of QRS duration in the non-ST-segment elevation acute coronary syndrome (NST-ACS): unstable angina and non-ST elevation acute myocardial infarction (non-STEMI).
Methods: This is a prospective and observational study in which we included 502 patients (age 71+/-10 years, 68% males, 29% diabetes) consecutively admitted for NST-ACS. QRS duration was manually measured from the 12-lead electrocardiogram. Our aim is to assess the relation between the QRS duration on admission (QRSd) and the risk of cardiovascular death (CvD) in the long-term.
Results: Mean QRSd was: 93+/-19 ms. After a median follow-up of 450 days, the cumulative incidence of CvD was: 17.8%. QRSd correlated with the incidence of CvD during the follow-up period: c=0.72 (p<0.001). The best cut-off point was 90 ms (sensitivity, specificity and negative predictive value of QRSd>or=90 ms for CvD: 82, 68 and 93%). According to the Kaplan-Meier analysis, QRSd>or=90 ms was associated with an increase in the risk of CvD: 26.6% versus 7.2% (log rank: 28.6; p<0.001). Cumulative incidence of CvD was higher in QRSd>or=90 ms in patients with unstable angina: 15.5% versus 4% (p=0.02), and in those with non-STEMI: 30.5% versus 8.9% (p<0.001). After adjusting for other significant variables (Cox-regression analysis), QRSd>or=90 ms persisted as an independent predictor for overall CvD (Hazard Ratio: 2.62; 95% Confidence Interval: 1.44-4.74; p<0.001).
Conclusion: In NST-ACS, the QRSd, even in the normal range, has prognostic implications. QRSd>or=90 ms is independently associated with an increased risk of CvD in the long-term.