A prolonged QTc‐interval at the emergency department: Should we always be prepared for the worst?

Abstract

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.

Prevalence and risk factors for acquired long QT syndrome in the emergency department: a retrospective observational study

“…Previous studies estimate that the prevalence of LQTS in the ED is 30%-40%. [17][18][19][20] Our results show that this syndrome is particularly common in this setting, even when accounting only for patients with a severely prolonged QTc. Similar to other studies, we detected that these were mainly older patients (73.49±14.79 years).…”

“…Previous studies reported a prevalence between 28.5%-35% in the ED for QT prolongation, both acquired and hereditary. [17][18][19][20] Also, approximately 25% of the patients admitted to cardiac intensive care units (ICUs) had prolonged QTc intervals at admission [3] and 20%-24% had severely prolonged QTc intervals when admitted to any ICU. [21,22] The prevalence of QTc interval greater than 500 ms in other hospital wards was 0.7%-0.9%.…”

Prolonged QT Interval in Cirrhosis: Twisting Time?

“…14,16 In the acute setting at an emergency department, the use of appropriate QT correction formulas has shown to reduce the number of patients considered to have a prolonged QTc by 65%. 17 In patients with liver disease, the Fridericia formula has recently been shown to be superior over other formulas and its use is therefore recommended in patients with cirrhosis. [18][19][20] Identifying significant QTc prolongation starts with defining normal values (Table 1).…”

“… 11 , 14 The short-term predictive value for a prolonged QTc at the emergency department to predict in-hospital mortality was limited, whereas a severely prolonged QTc >500 ms was associated with in-hospital cardiovascular events. 17 …”

“…On a population level, due to the many factors that influence the QTc interval (e.g., obesity, diabetes, cardiomyopathies, and neurological disorders), a prolonged QTc interval may reflect a generic, long-term risk factor, unless acute changes in the QTc interval are present which may serve as a short-term risk factor. 17 Several of these acute ECG features associated with development of TdP have been described, such as short-term QT variability, 50 T-wave alternans, 51 T-peak to T-end time, 52 and T-wave notching. 53 As most of these features are associated with imminent TdP, within minutes or hours, their utility for guidance of long-term therapy and risk reduction is limited.…”