Abstract 12444: ECG Changes in Patients Treated with Mild Hypothermia After Cardio-Pulmonary Resuscitation for Out-of-Hospital Cardiac Arrest
Background: Mild therapeutic hypothermia improves neurologic outcome in patients after resuscitation. Under hypothermia, changes in the 12-lead ECG are observed. However, the effect of mild therapeutic hypothermia on parameters of the 12-lead ECG has not yet been systematically investigated.
Methods: In consecutive patients admitted after succesful out-of-hospital cardiac arrest due to ventricular fibrillation or asystole, hypothermia (33-34°C) was induced for 24 hours via an intravenous cooling catheter. After the cooling period, controlled rewarming (0.2°/h) was started to re-establish normothermia. On admission to hospital, during hypothermia and after rewarming a 12-lead ECG was recorded and the following parameters were determined: heart rate, PQ interval, QRS period and heart-rate-corrected QT interval.
Results: 68 patients were included (49 male, 19 female). The mean age was 65.0 ± 12.5 years. During hypothermia, heart rate decreased significantly from 87.1 ± 21.1/min to 72.3 ± 20.3/min (p<0,001). PQ interval did not change significantly (167.2 ± 23.0 ms vs. 171.4 ± 39.2 ms during hypothermia). Compared to the time of admission to hospital, QRS duration decreased during hypothermia significantly from 128.6 ± 31.5 ms to 119.2 ± 26.0 ms (p=0,025) and continued to decrease during the period of rewarming (109.9 ± 27.7 ms, p<0.01). The heart-rate-corrected QT interval showed a signficant prolongation during hypothermia from 480.3 ± 50.4 ms to 521.2 ± 46.9 ms (p<0,001) and a shortening after rewarming to 473.7 ± 45.4 ms.
Conclusions: Therapeutic hypothermia leads to significant prolongation of the heart-rate-corrected QT interval. This effect must be considered in patients after cardio-pulmonary resuscitation to avoid misinterpretation of the ECG concerning the cause of cardiac arrest.
- © 2011 by American Heart Association, Inc.