Electrocardiogram QT interval increases in acute stroke.
Mulcahy J., Johnson P., James M.
BACKGROUND AND OBJECTIVE: Acute stroke patients have a greater QT interval (QT) and QT interval dispersion than case controls, but evidence for a causal association between stroke and electrocardiogram (ECG) changes is limited because studies examined QT interval after stroke only. This retrospective observational study examined the change in QT interval around the time of acute stroke by comparing pre- and post-stroke ECGs. METHODS: QT was measured from all leads of the most recent pre-stroke and the earliest post-stroke ECGs of patients admitted with cerebral infarction or haemorrhage. QTmax (the longest QT interval) and QTmin (the shortest) for each ECG were identified. RESULTS: Data from 45 patients were analysed, mean age = 80 years, 87% ischaemic strokes. The mean increase for QTmax was 14.9 ms (95% CI = 6.1-23.7, p < 0.01), for QTmin 10.8 ms (95% CI = 2.5-19.0, p < 0.02) and for QT dispersion 4.1 ms (p = 0.14). No significant differences in QT change were found for different stroke subtypes or side of stroke. Regression analysis revealed no significant confounding variables. CONCLUSIONS: This study demonstrates an increase in QTmax and QTmin following acute stroke, while the QT rise was not significant. Negative results of analysis for potential confounders suggested that the increase in QT interval is probably due to the effect of acute stroke on cardiac autonomic function. A larger study may demonstrate a relation between QT disturbance and cerebral infarct size and site.