Incidental Abnormal ECG Findings and Long-Term Cardiovascular Morbidity and Mortality: a Population Based Study

Background: The additional prognostic value of a resting electrocardiogram (ECG) in long-term cardiovascular disease (CVD)-risk-assessment is questionable.

Objective: To assess a possible association of incidental abnormal ECG findings with long-term increased risk of CVD incidence and all-cause mortality, and to evaluate the additional prognostic value of ECG as a screening tool in adults without known CVD.

Methods: 2601 Israeli men and women without known CVD were followed for up to 40 years. During 1976-1982, participants underwent interviews, physical examinations and ECG. During 1999-2004, 930 survivals were followed for cumulative CVD-incidence, determined from self-report, medical history, and repeated ECG. The total cohort was followed for all-cause mortality until May 2017.

Results: At baseline, 1199(46.1%) were found to have incidental abnormal ECG findings (exposed-group). During a median follow-up of 23 years, 294 (31.6%) of the 930 follow-up survivals developed CVD. Incidental abnormal ECG findings were associated with CVD-risk (odds ratio=1.46, 95%CI, 1.09-1.97). The addition of such findings to a traditional CVD risk prediction model correctly reclassified 7.4% of participants (95%CI=1.48%-13.3%), according to three risk categories (mild (<20%), moderate (20%-30%) and high risk (>30%)), but did not improve mortality risk classification. During a median follow-up of 31-years, 1,719(66.1%) of the total cohort died. Adjusted Cox regression demonstrated a hazard ratio (HR) for all-cause mortality of 1.18(95%CI, 1.07-1.30) for exposed vs. unexposed individuals. Non-specific T-wave changes and left-axis deviation were the incidental ECG abnormalities that were associated with all-cause mortality [HR=1.18(95%CI 1.05-1.33) and HR=1.19(95%CI 1.00-1.42), respectively].

Conclusion: Incidental abnormal ECG findings were associated with increased long-term CVD-risk and all-cause mortality among individuals without known CVD, and improved risk classification for CVD incidence but not for all-cause mortality.