UCSF

QT interval prolongation on the electrocardiogram is a marker of abnormal ventricular repolarization and is associated with Torsades de Pointes, sudden death, and all-cause mortality in outpatient samples. This is the first inpatient study of acutely ill adults performed to determine the: 1) need for QT monitoring as outlined in American Heart Association (AHA) guidelines, 2) prevalence and predictors of QT prolongation, 3) association of QT prolongation with hospital length of stay and all-cause mortality and 4) ability of acute care nurses to perform accurate QT measurement by routine manual methods. Methods: Special study software (Philips Healthcare, Andover, MA) was installed to measure the QT and heart-rate-corrected QT (QTc) interval every minute in all patients admitted to 5 hospital units over a 2-month period. Patient data were abstracted directly from the medical record. Nurses' knowledge and skills were assessed by pre-post tests conducted during QT-related classes repeated 44 times on all nursing shifts. Nurses were taught how to measure the QT interval from a rhythm strip using hand-held calipers and to calculate the QTc using the Bazett formula. Results: Patients. 67,648 hours of QT data were obtained from 1039 patients. 73% of patients had at least 1 AHA indication for QT monitoring. 24% had an episode of dangerous QT interval prolongation > 500 milliseconds lasting 15 minutes or more. In a multivariate logistic regression analysis, predictors of QT prolongation were female sex, number of proarrhythmic drugs, low potassium or calcium, high glucose or creatinine, and history of stroke or hypothyroidism. An episode of QT prolongation was associated with longer length of stay (11.53 v 5.52 days, p <.0005) and greater all-cause mortality (8.7% v 2.6%, Fishers exact p < .0005). Patients with QT prolongation had 3 times the odds for all-cause mortality than those without (OR 2.99; 95% C.I., 1.1 - 8.1). Nurses. 391 participated in the classes (81.5% response rate). Education improved nurses' QT knowledge scores (44% v 77%, p <.0005). Nurses ability to calculate the QTc interval also improved (5.6% v 51.9%, p <.0005). Conclusion. A majority (73%) of acutely ill patients need QT monitoring and a significant proportion (24%) develop dangerous QT prolongation. QT prolongation is associated with longer hospitalization and 3 times the odds for mortality. With education, nurses' ability to perform QT measurement improves; however, an unacceptably high proportion (48%) is still unable to correctly measure the QTc interval. These data suggest that the need for QT monitoring is high and that software added to hospital cardiac monitors may be valuable to identify high risk patients who may warrant closer follow-up.