Abstract 10281: Frequency, Temporal Onset, and Risk Factors Associated With Acquired Long Qt Syndrome in a Critical Care Population
Background: An adverse event associated with medication administration is prolongation of the QT interval on the electrocardiogram known as acquired long QT syndrome (aLQTS). aLQTS increases the risk of developing Torsades de Pointe, a life-threatening cardiac arrhythmia. Prevention of adverse outcomes from aLQTS is challenging because of the multiple classes of medications associated with this condition. Intensive care unit (ICU) patients are at a particularly high risk for developing aLQTS because of multiple medications received; however, frequency of aLQTS in ICUs is unknown. The purpose of this study was to describe in an ICU population, 1) frequency of aLQTS; 2) average time period for the onset of aLQTS; 3) medications and host risk factors associated with aLQTS.
Methods: QT intervals were collected hourly for 72 hours on 88 consecutive subjects. QT intervals were corrected for heart rate (QTc) using Bazett's formula. Data points included: baseline (admission), first long, longest, and final QTc measures. Positive aLQTS was defined as a QTc ≥ 500 ms or QTc ≥ 60 ms increase from baseline. Medications and host risk factors were collected.
Results: aLQTS occurred in 52.3% of the sample. All subjects positive for aLQTS (n=46) had a mean onset of 7.4 + 9.4 hours from ICU admission. Subjects who developed aLQTS after ICU admission (n=32) had a mean onset of 10.6 + 9.5 hours; 14 were positive for aLQTS upon ICU admission. A significant difference was noted between subjects positive and negative for aLQTS who received a QT prolonging medication (p = .012). Thirteen subjects (28.3%) developed aLQTS in the absence of a known QT prolonging medication. Five medications but no other host risk factors were found to be statistically significant predictors for the development of aLQTS.
Conclusions: aLQTS was present in more than one-half of the sample. Approximately a quarter of the subjects developed aLQTS in the absence of an offending medication, indicating the importance of frequent QTc monitoring in all patients in ICUs. Larger studies to determine host risk factors associated with aLQTS in ICU populations are warranted.
- © 2010 by American Heart Association, Inc.