Monitoring the corrected QT in the acute care setting: A comparison of the 12­lead ECG and bedside monitor.

INTRODUCTION: Prolongation of the QT interval is a well-recognized complication associated with many commonly used medications. Emergency Department monitoring of the corrected QT (QTc) both before and after medication administration is typically performed using the 12­lead electrocardiogram (ECG). The purpose of this study is to compare the QTc reported on the 12­lead ECG to that reported by single brand of bedside monitor. METHODS: A convenience sample of emergency department patients over the age of 18 undergoing bedside monitoring and who had an ECG ordered by their treating physician were enrolled. These patients underwent simultaneous ECG and monitor QTc calculation. The primary outcome of interest was the correlation between the monitor and ECG QTc. Secondary outcomes included ability of each method to identify patients with a QTc >500ms and the ability of each method to identify patients with a QTc <450ms. RESULTS: A total of 125 patients had simultaneous ECG and monitor QTc measurements recorded. There was moderate correlation between the monitor and ECG QTc (Pearson's correlation coefficient=0.55). The median difference between the ECG QTc and the monitor QTc (ECG QTc minus monitor QTc) was -7ms (IQR -23 to 11ms). CONCLUSION: We found that there was moderate correlation between the QTc reported on the 12 lead ECG and that reported by the bedside monitor. This correlation is not strong enough to support the use of the bedside monitor as a substitute for the 12­lead ECG when evaluating a patient's QTc.