We sought to examine the relationship of the QTc interval with mortality and functional outcome after acute ischemic stroke, and determine whether a threshold cutoff is present beyond which risk of death increases.
The QTc interval was measured for all patients presenting to the emergency department. The outcomes were mortality at 90 days and functional outcome at hospital discharge. The cutoffs were determined plotting martingale residuals.
Patients with a prolonged QTc interval were more likely to die within 90 days compared with patients without a prolonged interval (relative risk [RR] 2.5; 95% confidence interval [CI] 1.5-4.1; P < .001). The estimated survival at 90 days was 70.5% and 87.1%, respectively. This association retained statistical significance after adjusting for age and National Institutes of Health Stroke Scale score (RR 1.7; 95% CI 1.0-2.9; P = .043). Patients with a prolonged QTc interval were also more likely to have poor functional status compared with patients without a prolonged interval (odds ratio 1.8; 95% CI 1.2-3.0; P = .006). This association was not statistically significant after adjusting for age and National Institutes of Health Stroke Scale score (odds ratio 1.2; 95% CI 0.7-2.4). The identified threshold cutoffs for increased risk of death at 90 days were 440 milliseconds for women and 438 milliseconds for men.
There appears to be an increased risk of early death in patients with acute ischemic stroke and a prolonged QTc interval at the time of emergency department presentation. Prognosis appears to be worse with QTc intervals longer than 440 milliseconds in women and longer than 438 milliseconds in men.