Abstract 301: Therapeutic Hypothermia Induced Change in Electrocardiographic Parameters and In-Hospital Mortality

Introduction: Therapeutic hypothermia (TH) is recommended by the American Heart Association for selected patients over the age of 18 who remain comatose after a cardiac arrest. Hypothermia triggers changes in electrocardiogram (ECG) parameters, but the association of these changes to in-hospital mortality remains unclear. Hypothesis: We hypothesized that TH would decrease heart rate (HR) and increase QTc interval without change in mortality. Methods: We retrospectively compared the ECG parameters from the pre-cooling phase to the ECG performed during the hypothermic phase (target temperature 33° Celsius) on all consecutive patients who received TH between 12/2006 and 2/2011 at our institution (n=58). Paired 2-sample t-test was used to compare ECG parameters and hospital outcomes. In-hospital mortality related to QTc interval change was compared using Pearson’s chi-squared test. Results: Compared to the pre-cooling ECG parameters, TH resulted in significant increases in PR and QTc intervals and decrease in HR ( Table ). During hospitalization, 27 of the 58 patients who received TH died. Patients who survived versus patients who died did not differ in HR change (-20.2 vs -25.4, p=0.58), change in PR interval (+11.7 vs +2.6, p=0.33), or change in QTc interval (+51.0 vs +27.8, p=0.22). Patients who survived had a longer QRS increase with TH than those who died (+5.6 vs -22.5, p=0.006). Eleven patients presented with right bundle branch block (RBBB) morphology on their pre-cooling ECG, but only 1 continued to have RBBB during cooling. Three patients presented with left bundle branch block (LBBB), but only 2 remained in LBBB with cooling. None developed new bundle branch block during TH. Comparing patients who had decreased QTc intervals with TH to those with prolonged QTc intervals, 9 out of 16 died in the former group whereas 16 out of 39 died in the latter group (p=0.0001). Conclusion: Therapeutic hypothermia in comatose patients with cardiac arrest led to a significant decrease in heart rate and prolongation of QTc interval with no association to mortality. Further research is needed to examine whether prolongation of QTc and/or QRS with hypothermia reflects improved outcomes. ![Graphic][1] [1]: /embed/inline-graphic-1.gif