Introduction QTc‐interval prolongation is associated with ventricular arrhythmias and mortality in a general population. Bazett's correction formula (QTcB) is routinely used despite its overcorrection at high heart rates. Recently, we proposed a patient‐specific QT correcting algorithm (QTcA) resulting in improved rate correction and predictive value in a general population. We hypothesize risk stratification at the Emergency Department (ED) could be improved using QTcA. Methods and Results A retrospective case‐control study including a randomized age‐ and sex‐matched control population was performed at a tertiary care ED. A total of 1930 patients were included in the analysis (63.0% males, age 71.5 ± 15.6 years). Patient characteristics, history, and test results at the time of the electrocardiogram were collected. QTc was dichotomized as prolonged (>450 millisecond for men, >470 millisecond for women) or severely prolonged (>500 millisecond). Implementation of QTcA would reduce the number of patients considered to have a prolonged QTc by 65.2%, for severely prolonged QTc 79.6%. Multivariate regression was performed for in‐hospital mortality, cardiovascular endpoints, and hospital admission. Neither a prolonged QTcB (HR 1.04; 95% CI, 0.64‐1.69) nor QTcA (HR 0.76; 95% CI, 0.42‐1.38) was an independent predictor of in‐hospital mortality. A severely prolonged QTcA (OR, 2.54; 95% CI, 1.04‐6.23) was an independent predictor of cardiovascular events. Both a prolonged QTcA (OR, 1.52; 95% CI, 1.06‐2.18) and a prolonged QTcB (OR, 1.37; 95% CI, 1.05‐1.79) were associated with higher hospitalization rates. Conclusions QTcA reduced the number of patients considered at risk. Neither QTcB nor QTcA were predictors of in‐hospital mortality. A severely prolonged QTcA was associated with cardiovascular events.

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