To determine if the association between electrocardiographic left ventricular hypertrophy (ECG-LVH) and ischaemic stroke is partially explained by the concomitant presence of QT prolongation.
A total of 24 948 (mean age = 65 ± 9.4 years; 40% black; 55% women) participants from the REasons for Geographic And Racial Differences in Stroke (REGARDS) study were included in this analysis. Electrocardiographic left ventricular hypertrophy was defined by the Sokolow–Lyon criteria. Heart rate-adjusted QT (QT a) was computed using a linear regression model. Adjudicated ischaemic stroke events were the outcome of interest. Cox regression was used to compute hazard ratios (HRs) and 95% confidence intervals (CIs) for associations between ECG-LVH and prolonged QT a, in isolation and combined, with ischaemic stroke. There were 2422 (9.7%) participants with ECG-LVH, 820 (3.3%) with prolonged QT a, and 161 (0.6%) with both. Over a median follow-up of 7.6 years, 714 (2.9%) ischaemic stroke events occurred. After adjustment for stroke risk factors and potential confounders, an increased risk of ischaemic stroke was observed among participants with ECG-LVH and prolonged QT a (HR = 1.85, 95% CI = 1.04–3.30), isolated ECG-LVH (HR = 1.40, 95% CI = 1.13–1.75), and isolated prolonged QT a (HR = 1.45, 95% CI = 1.04–2.03) compared with participants without either condition. When ECG-LVH and prolonged QT a were examined as separate variables, the risk of ischaemic stroke for each condition remained statistically significant.