Computerized QT and QTc Measurements From Bedside ICU Monitors Are Similar to Those Derived From a Standard 12-Lead ECG

Abstract

QT/QTc prolongation is associated with an increased risk for torsade de pointes. In at-risk hospitalized patients, it is common to obtain a standard 12-lead electrocardiogram (ECG) for this assessment, but this interrupts patient care. Our hospital recently introduced bedside monitors in the intensive care unit (ICU) with continuous QT/QTc software. However, only four of the seven available ECG leads are used.

Purpose

Evaluate the agreement between computerized QT/QTc measurements from the bedside monitor (four leads) and a time-matched standard 12-lead ECG.

Design

Prospective observational study in three adult ICUs.

Methods

QT/QTc measurements were obtained from a convenience sample, and the two ECG types were ≤ 30 min apart. Agreement was evaluated using Bland–Altman analysis.

Results

A total of 120 patients were evaluated for inclusion, and 60 (50%) had a 12-lead ECG for comparison. The mean bias difference for QT measurements was not statistically different (β = −2.47, 95% CI = 5.50 to −11.05; p = 0.44; limits of agreement (LOA) = −64.37 to 59.44). Similar non-statistical differences were observed for QTc (β = −3.20, 95% CI = 5.50 to −11.05; p = 0.44; LOA = −67.43 to 61.03).

Conclusion

There was good agreement for both QT and QTc measurements between the two methods. These pilot data are promising and suggest QT/QTc measurements from bedside monitors (four leads) may be an acceptable alternative to obtaining additional standard 12-lead ECGs. Given that half of the ICU patients screened did not have a 12-lead ECG recorded, bedside monitor QT/QTc's could identify at-risk patients. However, an evaluation in a larger sample and non-ICU patients is warranted.