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

Mohammad Toma

doi:10.4172/2161-0495.1000195

Abstract

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.

Highlights

Prolongation of the QT interval on the electrocardiogram has been associated with an increased risk of malignant arrhythmias, cardiac arrest and death [1]
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
That QT interval prolongation is common among patients undergoing cardiothoracic surgery (Table 1); 69 patients (27%) displayed a QTc interval longer than 480 ms

Summary

Introduction

Prolongation of the QT interval on the electrocardiogram has been associated with an increased risk of malignant arrhythmias, cardiac arrest and death [1]. Case series of torsades de pointes ventricular tachyarrhythmia suggest that the extent of QT interval prolongation may be used as a marker for a given drug’s cardiotoxicity [2,3]. We wanted to ascertain how common prolonged QTc interval (QT interval corrected by heart rate) is in post-cardiac surgery patients in one of the largest Heart Centers in Europe. We wanted to determine whether QT interval prolongation is a common finding among consecutive patients following cardiac surgery, whether this possibly observed QT interval prolongation is acquired and/or mainly seen in patients with cardiac or renal dysfunction. We sought to establish whether QT interval prolongation in this group would reflect the prevalence of atrial and ventricular arrhythmias and death

Methods

Results

Discussion

Conclusion