Objective: To test the potential value of more frequent QT interval measurement in hospitalized patients.
Design: We performed a prospective, observational study.
Setting: All adult intensive care unit and progressive care unit beds of a university medical center.
Patients: All patients admitted to one of six critical care units over a 2-month period were included in analyses.
Interventions: All critical care beds (n = 154) were upgraded to a continuous QT monitoring system (Philips Healthcare).
Measurements and Main Results: QT data were extracted from the bedside monitors for offline analysis. A corrected QT interval >500 msecs was considered prolonged. Episodes of QT prolongation were manually over-read. Electrocardiogram data (67,648 hrs, mean 65 hrs/patient) were obtained. QT prolongation was present in 24%. There were 16 cardiac arrests, with one resulting from Torsade de Pointes (6%). Predictors of QT prolongation were female sex, QT-prolonging drugs, hypokalemia, hypocalcemia, hyperglycemia, high creatinine, history of stroke, and hypothyroidism. Patients with QT prolongation had longer hospitalization (276 hrs vs. 132 hrs, p < .0005) and had three times the odds for all-cause in-hospital mortality compared to patients without QT prolongation (odds ratio 2.99 95% confidence interval 1.1–8.1).
Conclusions: We find QT prolongation to be common (24%), with Torsade de Pointes representing 6% of in-hospital cardiac arrests. Predictors of QT prolongation in the acutely ill population are similar to those previously identified in ambulatory populations. Acutely ill patients with QT prolongation have longer lengths of hospitalization and nearly three times the odds for mortality then those without QT prolongation.
From the Department of Physiological Nursing (DP, GC, JNL, BJD), University of California San Francisco, San Francisco, CA; Advanced Algorithm Research Center (EH), Philips Healthcare, San Jose, CA; Stanford University Medical Center (JAS, AW), Stanford, CA; School of Nursing (MF), Yale University, New Haven, CT.
* See also p. 658.
Supported, in part, by a research gift from Philips Healthcare.
Dr. Pickham received an unrestricted research gift from Philips Healthcare. Dr. Helfenbein received a patent as a full-time Philips Healthcare employee. Dr. Helfenbein also holds stock ownership and options with Philips Healthcare. The remaining authors have not disclosed any potential conflicts of interest.
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