Agreement of Computerized QT and QTc Interval Measurements Between Both Bedside and Expert Nurses Using Electronic Calipers

Abstract

Background In hospitalized patients, QT/QTc (heart rate corrected) prolongation on the electrocardiogram (ECG) increases the risk of torsade de pointes. Manual measurements are time-consuming and often inaccurate. Some bedside monitors automatically and continuously measure QT/QTc; however, the agreement between computerized versus nurse-measured values has not been evaluated. Objective The aim of this study was to examine the agreement between computerized QT/QTc and bedside and expert nurses who used electronic calipers. Methods This was a prospective observational study in 3 intensive care units. Up to 2 QT/QTc measurements (milliseconds) per patient were collected. Bland-Altman test was used to analyze measurement agreement. Results A total of 54 QT/QTc measurements from 34 patients admitted to the ICU were included. The mean difference (bias) for QT comparisons was as follows: computerized versus expert nurses, −11.04 ± 4.45 milliseconds (95% confidence interval [CI], −2.3 to −19.8; P = .016), and computerized versus bedside nurses, −13.72 ± 6.70 (95% CI, −0.70 to −26.8; P = .044). The mean bias for QTc comparisons was as follows: computerized versus expert nurses, −12.46 ± 5.80 (95% CI, −1.1 to −23.8; P = .035), and computerized versus bedside nurses, −18.49 ± 7.90 (95% CI, −3.0 to −33.9; P = .022). Conclusion Computerized QT/QTc measurements calculated by bedside monitor software and measurements performed by nurses were in close agreement; statistically significant differences were found, but differences were less than 20 milliseconds (on-half of a small box), indicating no clinical significance. Computerized measurements may be a suitable alternative to nurse-measured QT/QTc. This could reduce inaccuracies and nurse burden while increasing adherence to practice recommendations. Further research comparing computerized QT/QTc from bedside monitoring to standard 12-lead electrocardiogram in a larger sample, including non-ICU patients, is needed.