ST segment depression on 24-hour electrocardiography predicts incident atrial fibrillation in two population-based cohorts

ST-depression at 24hECG has not been studied in relation to atrial fibrillation (AF) risk. We aimed to determine whether ST-depression at 24hECG was associated with incident AF in two Swedish population-based cohorts - a sub-cohort of the Malmo Diet and Cancer study (MDCS), and the cohort 'Men born in 1914', and to determine whether 24hECG could be used to predict AF development. There were 378 acceptable 24hECG recordings in the MDCS (mean age 64.5 years, 43% men) and 394 acceptable recordings in 'Men born in 1914' (mean age 68.8 years). Incidence of AF was monitored using national registers of hospitalizations and outpatient visits in Sweden. Mean follow-up +/- SD (cumulative incidence) was 10.4 +/- 2 years (11.3%) in MDCS, and 10.9 +/- 4 years (7.3%) in 'Men born in 1914'. ST-depressions were independently associated with incident AF; hazard ratio (HR) (95% CI) 2.41 (1.29-4.50, P = 0.006) and 2.28 (1.05-4.95, P = 0.038) after adjustment [age, sex, height, weight, systolic blood pressure, smoking, anti-hypertensive drugs, LDL/total cholesterol, and HOMA-IR (in MDCS)]. AF incidence was substantially lower in individuals who had neither ST-depressions or high supraventricular activity (SVA, negative predictive value 0.97 and 0.94, in MDCS and 'Men born in 1914', respectively), and similar in men and women. ST-depression at 24h-ECG is independently associated with incident AF, and incidence is substantially lower in individuals with neither ST-depression or high SVA. 24hECG can be used not only to diagnose AF but also to identify individuals at high and low AF risk.