Clinical paperSevere QTc prolongation under mild hypothermia treatment and incidence of arrhythmias after cardiac arrest—A prospective study in 34 survivors with continuous Holter ECG☆
Introduction
Mild therapeutic hypothermia (MTH) has become a routine procedure in survivors after cardiac arrest to improve neurological outcome following the current guidelines by the International Liaison Committee on Resuscitation (ILCOR) and the European Resuscitation Council (ERC).1 A possible transient bradycardia is well known under conditions of hypothermia but only a few studies evaluated the influence of MTH towards heart rate variability and the risk of life-threatening arrhythmias.2, 3 A currently published case series described in four patients undergoing MTH a prolongation of the corrected QT interval (QTc).4 QTc prolongation itself can promote the development of malignant arrhythmias, for example ventricular tachycardia (VT).5
This prospective study was conducted to evaluate the frequency of malignant arrhythmias and to analyse the possible effect of hypothermia on the QTc interval using a continuous Holter ECG during MTH treatment.
Section snippets
Methods
The protocol of this prospective single center study was approved by the local ethics committee on human research and is conducted in accordance with the guidelines of the Declaration of Helsinki. Written informed consent for the use of routine clinical data is part of the standard contract between patients and the Charité Universitätsmedizin Berlin and was obtained from patients or their legal representatives, if available. During the inclusion period between April 2009 and December 2009 a
Baseline characteristics
Median age was 61.5 years (52.0–77.5 IQR) with a majority of OHCA patients (82.3%). In n = 15 the initial rhythm was ventricular fibrillation (VF), n = 12 had asystole and n = 7 suffered cardiac arrest due to pulseless electrical activity. The median number of defibrillations in the VF group was 2 (1.26–4.0 IQR). 20.6% of the patients received initial antiarrhythmic drug treatment with amiodarone during resuscitation (bolus dosage of 300 mg i.v. once) and three patients received 300 mg amiodarone bolus
Discussion
This is the first study revealing a profound prolongation of the QTc interval during MTH without a severe incidence of life-threatening arrhythmias. Furthermore no Torsade de pointes were detected during 48 h Holter ECG monitoring, although a tight correlation was observed of prolonged QTc interval and decreasing temperature level in patients undergoing MTH and only a low incidence of VT has been recorded.
In general, if central body temperature decreases, a decrease of heart rate, spontaneous
Conclusion
According to our results, during mild hypothermia treatment one should closely monitor the QTc interval and should be aware of potentially upcoming malignant arrhythmias. Furthermore, the treatment with drugs causing an additional prolongation of QTc interval, especially anti-arrhythmic drugs and antibiotics that are frequently used in the ICU setting, should be made with caution. However, routine and frequent ECG recording with respect to the QTc interval should become part of any hypothermia
Conflict of interest
None declared.
Acknowledgments
The authors would like to thank Astrid Caemmerer for assistance and support throughout the study. This work was supported by Schiller MediLog GmbH, Wiesbaden, Germany, with technical equipment (Medilog AR12 recorder).
References (14)
- et al.
Therapeutic hypothermia after cardiac arrest. An advisory statement by the Advancement Life support Task Force of the International Liaison committee on Resuscitation
Resuscitation
(2003) - et al.
Assessment of outcome after severe brain damage
Lancet
(1975) - et al.
Hypothermia: evaluation, electrocardiographic manifestations, and management
Am J Med
(2006) - et al.
Effect of hypothermia on transthoracic defibrillation in a swine model
Resuscitation
(2005) - et al.
The prevalence and factors associated with QTc prolongation among emergency department patients
Ann Emerg Med
(2009) - et al.
Changes in the PQRST intervals and heart rate variability associated with rewarming in two newborns undergoing hypothermia therapy
Neonatology
(2009) - et al.
Arrhythmias and heart rate variability during and after therapeutic hypothermia for cardiac arrest
Crit Care Med
(2009)
Cited by (32)
Targeted Hypothermia vs Targeted Normothermia in Survivors of Cardiac Arrest: A Systematic Review and Meta-Analysis of Randomized Trials
2022, American Journal of MedicineCitation Excerpt :On the other hand, the risk of significant arrhythmia was increased. QTc prolongation is frequently observed in patients undergoing therapeutic hypothermia, but it was not associated with increased risk of in-hospital mortality in one study.22-24 A study of 47 patients treated with therapeutic hypothermia to 32-34°C after cardiac arrest showed that the heart rate decreased and the QTc increased during hypothermia; also, 38.3% of patients had arrhythmia, most commonly non-sustained ventricular tachycardia.23
QTc interval in survivors of out of hospital cardiac arrest
2021, International Journal of CardiologyCitation Excerpt :It is unclear whether this is a transient phenomenon, or a manifestation of an underlying arrhythmic substrate such as Long QT syndrome (LQTS). Furthermore, QTc interval prolongation has been described in association with TTM, although previous studies have not linked this with increased incidence of malignant arrhythmias [12–16]. In this observational study, we sought to clarify the incidence of QTc interval prolongation post-OHCA, the behaviour of QTc interval during admission and persistence at discharge.
Targeted temperature management after sudden cardiac arrest: Proarrhythmic or antiarrhythmic? Probably both
2018, Journal of Critical CareDeterminants of cardiac repolarization and risk for ventricular arrhythmias during mild therapeutic hypothermia
2018, Journal of Critical CareCitation Excerpt :A high ventricular arrhythmic event rate may be expected in the post-resuscitation population. However, previous studies assessing the arrhythmic risks associated with MTH did not include a control group of patients who were not exposed to MTH [5,10,11]. Thus, it is difficult to distinguish MTH-related ventricular arrhythmias from those arising from multiple additional risk factors other than exposure to hypothermia.
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A Spanish translated version of the abstract of this article appears as Appendix in the final online version at doi:10.1016/j.resuscitation.2011.02.043.