Relation of Minor Electrocardiographic Abnormalities to Cardiovascular Mortality

Although minor electrocardiographic (ECG) abnormalities are common findings in clinical practice, their prognostic significance remains unclear due to inconsistent reports. We hypothesized that this inconsistency is due to the traditional focus on examining their prognostic significance as a binary variable (i.e., presence vs absence of any abnormality) ignoring the number of abnormalities. We tested this hypothesis in 6,467 participants (mean age 59 years, 53% women) from the Third National Health and Nutrition Examination Survey who were free of baseline cardiovascular disease (CVD) and major ECG abnormalities. ECG abnormalities were defined from digitally recorded and centrally processed standard electrocardiograms using the Minnesota ECG Classification. CVD mortality was ascertained using National Death Index. About 38% of participants (n = 2,438) had at least 1 minor ECG abnormality at baseline. During a median follow-up of 13.9 years, 755 CVD deaths occurred. In a multivariable Cox model, presence of at least 1 minor ECG abnormality was marginally associated with increased risk of CVD mortality (hazard ratio (95% confidence interval):1.15(1.00,1.34), p-value = 0.04)). However, as the number of ECG abnormalities increases, the association with CVD mortality showed a dose-response relation (event rate per 1,000 person-year of 7.3, 10.1, and 16.7 in participants with 0, 1, and ≥2 ECG abnormalities, respectively; p-value for trend <0.01). Also, each additional minor ECG abnormality was associated with a 13% increased risk of CVD mortality (hazard ratio (95% confidence interval): 1.13(1.04, 1.24)). In conclusion, the number, not only the mere presence of minor ECG abnormalities should be taken into account to understand the prognostic significance of these common findings.