Acquired Long QT Interval: A Case Series of Multifactorial QT Prolongation

Abstract

Background: Acquired long QT (LQT) interval is thought to be a consequence of drug therapy and electrolyte disturbances. Hypothesis: We characterize the potential effects of polypharmacy in a case series of acquired LQT and torsades de pointes (TdP) in order to determine whether multiple risk factors play a role in the development of LQT. Methods: The case series consisted of 11 patients presenting to 4 tertiary care hospitals with LQT and ≥2 risk factors for developing LQT. Clinical characteristics, medications, electrolyte disturbances, and course in hospital were analyzed. Results: Mean age was 49.1 ± 5.8 years. Eight patients were female. Four had hypertension, 1 had a history of dilated cardiomyopathy, and 1 patient demonstrated complete atrioventricular block. Average QTc interval at presentation was 633.8 ± 29.2 ms. Nine patients developed TdP. In 3, LQT was not initially detected and amiodarone was administered, followed by development of TdP. Patients were taking an average of 2.8 ± 0.3 QT-prolonging medications-an antidepressant in 6 cases and a diuretic in 8 cases. All patients had an electrolyte abnormality; 8 patients presented with severe hypokalemia (<3.0 mmol/L). Average serum potassium and magnesium were 2.82 ± 0.10 mmol/L and 0.75 ± 0.03 mmol/L, respectively. There were no deaths. Conclusions: This case series highlights the risks of polypharmacy in the development of LQT and TdP. It illustrates the importance of early detection of LQT in patients with multiple risk factors in ensuring appropriate treatment.

Torsade de Pointes and Persistent QTc Prolongation after Intravenous Amiodarone

“…In another case, QTc normalized one day after 570 mg intravenous amiodarone [2]. However, in a further patient, QTc prolongation persisted for 5 days after 450 mg intravenous amiodarone, possibly due to concurrent methadone treatment [3]. In contrast with these findings, the most interesting observation in our case was the markedly prolonged time-course of QTc lengthening, which normalized 15 days after 1.65 g amiodarone administration.…”

Interaction Between Domperidone and Ketoconazole: Toward Prediction of Consequent QTc Prolongation Using Purely In Vitro Information

“…While the first conclusion one may draw would be related to the shortcomings of the model, evidence from other literature supports the outcome of the modeling as recent reports suggest that DOM carries significant cardiac risk and should be withdrawn from the market 31 , 32 . The simulation results, from the risk assessment point of view, suggest potential risks 33 , 34 . It is in this line that the European Medicines Agency initiated reviewing the DOM via the Belgian Medicines Agency 35…”

Update to Practice Standards for Electrocardiographic Monitoring in Hospital Settings: A Scientific Statement From the American Heart Association

“…Evidence suggests that a combination of clinical risk factors and QTpro longing medications may present increased risk for TdP. 97 Among inpatients with observed prolonged QTc interval, monitoring is a high priority if they exhibit any of the risk factors or specific electrocardiographic indi cators of impending TdP (Table 5).…”