Abstract 113: The Benign Nature of Therapeutic Hypothermia--Induced Long QTc
Introduction: Therapeutic hypothermia (TH) can prolong the QT interval, however, this is generally not associated with Torsade de pointes (TdP). We hypothesize that the danger of the lengthened QTc could be mitigated by a decrease in QT dispersion.
Methods: All survivors of cardiac arrest who completed a minimum of twelve hours of TH at Bellevue Hospital Medical Center were evaluated for study inclusion (January 2007- March 2010). Electrocardiograms were obtained before and after 12 hours of TH. The Wilcoxon Signed Ranks Test was used to compare the QTc intervals and used to compare the QT dispersion values. QT dispersion was not measured in patients with atrial fibrillation. Continuous variables are summarized as medians and (interquartile, IQR) ranges.
Results: Data were available on 30 patients. Six patients were excluded for premature termination of TH (none arrhythmia related). Four additional patients were excluded for lack of electrocardiograms or pacing. Thus, 20 patients were included for analysis. Diagnoses of cardiac arrest included: ventricular fibrillation (n=8), pulseless electrical activity (n=4), ventricular tachycardia (n=3), asystole (n=1), polymorphic ventricular tachycardia (n=1), and unknown (n=3). TH was associated with a prolongation of the QTc (475 ms [IQR 441 ms - 526 ms] vs 527 ms [IQR 511 ms - 585 ms], p<0.001; n=20). TH was also associated with a reduction in the QT dispersion (40 ms [IQR 15 ms - 80 ms] vs 20 ms [IQR 0 ms - 25 ms], p<0.01, n=14). No patient had TdP. QTc increased significantly in patients that received amiodarone during TH (465 ms [IQR 444 ms - 502ms] to 531 ms [499 ms, 557 ms], p = 0.005, n=10).
Conclusions: Therapeutic hypothermia significantly prolongs the QTc interval, but was not associated with TdP. The observed decrease in QTc dispersion is a possible mechanism for protection. These data suggest that TH need not be terminated prematurely secondary to prolongation of the QTc interval.
- © 2011 by American Heart Association, Inc.