Abstract 20170: High Prevalence of QT Interval Prolongation in Hospitalized Patients is Linked to Mortality: Results of the QT in Practice (QTIP) Study.
Electrocardiographic (ECG) QT interval prolongation increases the risk for sudden death due to torsades de pointes. The American Heart Association's recent Scientific Statement outlines indications for QT monitoring in hospital settings. We performed a prospective study of 1039 consecutive patients admitted to critical care units at a large academic medical center. Study aims were to determine the need for QT monitoring, the prevalence and predictors of QT prolongation, the relationship of QT prolongation with hospital mortality, and nurses’ abilities to perform QTc measurement.
Methods: Patients: Continuous QT monitoring software was installed in all monitored beds (n=154) across 5 critical care units. A QT interval >500 milliseconds was considered prolonged. All episodes of QT prolongation were manually over read.
Nurses: During 47 hospital-wide inservices, nurses (n=379) were asked to manually measure/calculate the QTc interval on a sample rhythm strip.
Results: Overall 67,648 hours of ECG data (65 hours/patient) were obtained. Seven hundred and seventeen (69%) patients had AHA indications recommending QT monitoring. Only 6% of nurses could perform QTc measurement prior to the inservice. One quarter (24%) of patients developed QT prolongation; more women developed QT prolongation than men (30% vs 20%, p=.001). Independent predictors explaining 16% - 24% variance were female sex, number of proarrhythmic drugs, hypokalemia, hypocalcemia, hyperglycemia, high serum creatinine, history of cerebrovascular accident and hypothyroidism. Patients with QT prolongation had greater in-hospital mortality than patients without (8.7% v 2.6%, Fishers exact p < .0005). Controlling for known risk factors for mortality, patients with QT prolongation were 3 times more likely to die in the hospital (OR 2.99 95% C.I. 1.1 - 8.1).
Conclusions: This study demonstrates that critical care patients, especially women, have a high need for QT monitoring. Nurses however are not adept at performing this skill. Dangerous QT prolongation is common (24%), and is associated with in-hospital mortality.
- © 2010 by American Heart Association, Inc.