Hyperglycemia is associated with corrected QT prolongation and mortality in acutely ill patients.
BACKGROUND
The QT interval on an electrocardiogram represents ventricular repolarization time. Increased length of this interval, known as corrected QT (QTc) prolongation, can be a precursor to torsade de pointes, a potentially life-threatening ventricular dysrhythmia. An association exists between blood glucose and QTc interval in ambulatory populations. Because both hyperglycemia and QTc prolongation are common in critically ill patients, we sought to examine the relationship between blood glucose, QTc interval prolongation, and all-cause mortality in critically ill patients.


METHODS
We studied adult patients admitted to cardiac monitoring units. Blood glucose and other clinical variables were abstracted from the medical record. Corrected QT measurements were automatically derived from continuous bedside cardiac monitoring systems.


RESULTS
Twenty-five percent (233/940) of the patients had QTc prolongation, and 53% had elevated blood glucose (>140 mg/dL) during hospitalization. Adjusted odds for QTc prolongation were 2.1 (95% confidence interval, 1.5-3.1) for moderately elevated blood glucose (140-180 mg/dL) and 3.7 (95% confidence interval, 2.5-5.4) for severely elevated blood glucose (>180 mg/dL). Mortality rate was highest (16%) in patients experiencing both severely elevated blood glucose (>180 mg/dL) and QTc interval prolongation.


CONCLUSIONS
Hyperglycemia is linked with QTc prolongation, and both are associated with increased odds of mortality in critically ill patients. Further studies are needed to extrapolate the relationship between glucose and ventricular repolarization, as well as appropriate glucose control parameters and QTc interval monitoring in critical care units.
David Pickham, PhD, RN Assistant Adjunct Professor, Department of Physiological Nursing, University of California, San Francisco. Elena Flowers, PhD, RN, MS, MAS Assistant Professor, Department of Physiological Nursing, University of California, San Francisco. Barbara J. Drew, PhD, RN Professor, Department of Physiological Nursing, University of California, San Francisco.
David
D
Pickham
Elena
E
Flowers
Barbara J
BJ
Drew
D000328:Adult; D000368:Aged; D016638:Critical Illness; D004562:Electrocardiography; D005260:Female; D006329:Heart Conduction System / Q000503:physiopathology*; D006801:Humans; D006943:Hyperglycemia / Q000150:complications* / Q000401:mortality; D008133:Long QT Syndrome / Q000150:complications* / Q000401:mortality; D008297:Male; D008875:Middle Aged