Electrocardiographic abnormalities improve classification of coronary heart disease risk in women: Tehran Lipid and Glucose Study

Abstract

Objectives: To examine the added value of electrocardiogram (ECG) abnormalities beyond the Framingham risk score (FRS) in risk stratification for coronary heart disease (CHD) in a population of Middle Eastern women.

Methods: The study population consisted of 2568 women aged ≥30 years, free from CHD symptoms and with no major Q or QS wave or complete left-bundle branch block in their baseline ECG. ECG abnormalities included ST depression (Minnesota codes 4.1-4.2), or T-wave items (Minnesota codes 5.1-5.2). Participants were categorized into 3 groups, according to their FRS. Cox regression analysis was used to estimate the hazard ratios (HR) of CHD events for ECG abnormalities among each FRS group. Net Reclassification Index (NRI) was used as the measure of predictive ability added to the FRS by ECG abnormalities.

Results: During 9.3 years, 127 CHD events occurred. In the FRS adjusted analysis, the HRs (95%CI) of CHD events were 3.69 (0.87-15.68), 3.82 (2.01-7.23) and 1.39 (0.47-4.16) for ECG abnormalities in each FRS category (i.e. 0-4.9%, 5-19.9 and ≥20%, respectively). Addition of ECG abnormalities to FRS did not significantly increase the C-statistics (0.838), but improved the predictive ability of the FRS by 20.8 (95% CIs 5.0-38.9) using the cut point free NRI.

Conclusion: Among women, only in the intermediate risk group, ECG abnormalities were independently associated with increased risk of developing CHD. Addition of the ECG abnormalities to the FRS improved the classification of coronary heart disease risk, especially in this group.