Abstract 18116: The Effect of Therapeutic Hypothermia on QT and Corrected QT Intervals in Patients With Cardiac Arrest and Their Association With Malignant Arrhythmias
Background: Therapeutic hypothermia (TH) is used to improve neurological outcomes after cardiac arrest. The effects of TH on manually and computer derived measures of the QT and corrected QT (QTc) intervals, and their association with malignant arrhythmias, have not been well characterized.
Methods: We performed a retrospective study of 193 patients undergoing TH for cardiac arrest between July 2007 and February 2013, reviewing 12-lead electrocardiograms before, during and after TH if available. We tabulated both manually-calculated and computer-derived QT and QTc intervals and examined the relationship between QTc and the occurrence of malignant arrhythmias, as well as the influence of ejection fraction (EF), serum electrolytes and any known QT-prolonging medications.
Results: 193 patients underwent TH for cardiac arrest, among which 100% (n=193) had a pre-TH ECG; 87% (n=167) had an ECG during-TH, and 74% (n=142) had a post-TH ECG. Computerized QTc was significantly different than manually derived QTc at all times (all p<0.05).
QTc before, during and post-TH were 459, 504 and 444 milliseconds (msec) respectively using computer derived QTc; and 509, 516 and 457 msec using manually derived QTc (all with significant differences p<0.05 at pre-TH vs. during TH, and during-TH vs. post-TH). There was no significant difference in computerized or manual QT and QTc at any time in patients with absence vs presence of malignant arrhythmias. There was also no difference in the presence of prior-to-admission QTc prolonging medications (36% vs. 41%, p=0.8), K+ (3.8 vs. 3.9 mEq/L, p=0.7), Mg+ (1.7 vs. 1.7 mEq/L, p=0.5), or EF (50 vs. 30%, p=0.3) in patients with absence vs presence of malignant arrhythmias.
Conclusions: Cardiac arrest patients experience significant acute changes in QT and QTc during TH. However, changes in QT and QTc are not associated with a greater risk for malignant arrhythmias and should not lead to premature cessation of TH.
Author Disclosures: D.F. Miranda: None. Y. Sandoval: None. Z.P. Rosol: None. S.W. Smith: None. B.A. Bart: None. S.R. Goldsmith: None.
- © 2014 by American Heart Association, Inc.