Jornal de Toxicologia Clínica
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QT Interval Prolongation after Cardiac Surgery; An Interesting Biological Phenomenon or A Clinical Problem? Data from the Prolonqit Study

Mohammad Toma, Peter Marstrand, Kristina Holmenlund, Saadia Umar, Michael Wanscher, Steen Pehrson and Juliane Theilade

Abstract Objective: Intrinsic and extrinsic factors may combine to delay the cardiac repolarization measured as the QT interval in the 12-lead electrocardiogram (ECG). As the duration of the QT interval is widely applied as an–albeit imperfect–marker of risk for malignant arrhythmias we characterized the prevalence and consequences of iatrogenic QT prolongation in patients undergoing cardiac surgery. Design/patients/setting: We prospectively included clinical data and ECGs from 259 patients admitted to the intensive care unit following cardiac surgery. Main results: Prolonged QT interval is common in patients undergoing cardiac surgery; 18% of patients displayed a QTc interval longer than 500 ms in the immediate postoperative period. The majority of these patients also showed QTc prolongation before surgery, however, the QTc interval was additionally prolonged following surgery. Drugs that prolong the QT interval were commonly used. The number of these drugs used in combination correlated with the prolongation of the QTc interval. QTc duration was not prolonged in patients with reduced left ventricular ejection fraction or renal function or in patients with atrial or ventricular arrhythmias or death. Conclusions: An increased QT interval is a common finding amongst cardiothoracic surgery patients and it correlates to the administration of drugs with QT prolonging effects in the immediate postoperative period. We could not prove a correlation between the observed QT prolongation and adverse outcomes. However, the high prevalence of ECG abnormalities corresponding to the use of certain drugs calls for caution if treatment is continued especially when intensive care and monitoring is terminated.