The Prevalence and Factors Associated With QTc Prolongation Among Emergency Department Patients

Study objective

Previous studies have suggested that QTc prolongation may lead to significant morbidity and mortality. The prevalence of QTc prolongation among emergency department (ED) patients is unknown. The purpose of this study is to determine the prevalence of QTc prolongation among ED patients.

Methods

This was a retrospective review of ED and inpatient data for all patients with an ECG conducted for any reason at a tertiary care university ED during a 3-month period. QTc prolongation was defined as computer-generated QTc intervals greater than or equal to 450 ms for men and greater than or equal to 460 ms for women.

Results

Of the 1,558 eligible cases, 544 patients had QTc prolongation (35%; 95% confidence interval [CI] 32% to 37%). The prevalence of QTc intervals greater than or equal to 500 ms was 8% (120/1,558; 95% CI 6% to 9%). The most common comorbidities were structural heart disease, renal failure, and stroke. Forty-four percent (239/544; 95% CI 40% to 48%) of patients with any degree of QTc prolongation were discharged from the ED. Furthermore, 23% (28/120; 95% CI 16% to 32%) of patients with QTc intervals greater than or equal to 500 ms were discharged from the ED, including 16 patients with QTc intervals greater than or equal to 500 ms and QRS durations less than 120 ms (16/60; 27%; 95% CI 16% to 40%). Five percent of the patients with QTc prolongation died in the ED or during hospitalization (27/544; 95% CI 3% to 7%); none had QTc prolongation or torsades de pointes listed as a cause of death.

Conclusion

QTc prolongation occurred frequently among ED patients who had an ECG study for any reason. Nearly half of all patients with QTc prolongation were discharged from the ED.