Clinical PotpourriThe effect of targeted temperature management on QT and corrected QT intervals in patients with cardiac arrest☆
Introduction
Targeted Temperature Management (TTM) improves neurological outcomes and survival after out-of-hospital cardiac arrest (OHCA) secondary to ventricular fibrillation (VF) [1], [2]. Accordingly, TTM has become a routine procedure in those suffering OHCA (of any cause, though data for proof of benefit in non-VF populations is lacking). Moreover, Part 8 of the current American Heart Association Guidelines for Cardiopulmonary Resuscitation recommends the use TTM in all comatose adult patients with ROSC after cardiac arrest [3]. Hypothermia has well described cardiac side effects including both bradycardia and prolongation of the QT interval [4], [5]. These, combined with the increased incidence of recurrent arrhythmias after successful return of spontaneous circulation (ROSC) raises concern for monitoring guidelines surrounding patients undergoing TTM and their risk of recurrent arrhythmias [6]. There have been few studies that have examined or proposed cardiac monitoring parameters and the rate of arrhythmias in patients undergoing TTM. The primary purpose of this study was to determine whether the QTc interval was prolonged during hypothermia, and if so, to investigate whether there was an association between the occurrence of malignant arrhythmias and the QTc. We also assessed the relationship between the presence of QTc prolonging medications, QTc measurements and the occurrence of malignant arrhythmias.
Section snippets
Methods
We performed a retrospective, single-center study of all patients undergoing TTM after OHCA between July 2007 and February 2013. Study approval was obtained from the Human Subjects Research Committee and Hennepin County Medical Center. All patients received TH treatment after resuscitation regardless of their presenting rhythm. Therapeutic hypothermia was initiated following the established institutional protocol either with ArticSun® or Alsius®cooling machine. The target temperature was 33.5 °C
Results
Two hundred and thirty patients presented with OHCA, of which 193 underwent TTM. In 106 (55%) patients, the initial rhythm was VF or VT, 49 (25%) had asystole, 31(16%) presented with pulseless electrical activity (PEA), and 7 (4%) had undocumented rhythms. The median age of the patients was 55 years, 132 were male, 121 were Caucasian, 33 had a history of coronary disease, 33 had a history of heart failure, 10 had ESRD. 53 had a history of diabetes. 70 had exposure to QT prolonging medications
Discussion
In our series, patients undergoing hypothermia experienced a statistically significant prolongation of both the QT and the QTc intervals (p < 0.0001) Table 1. This finding is congruent with data published in other studies of smaller sizes [9], [10], [11] and is of clinical relevance during hypothermia. In this report we also provide data on differences between manually-derived and computer-derived QT and QTc. Manually derived values for all ECGs were analyzed by two readers using an agreed upon
Conclusion
QT and QTc interval prolongation was observed consistently in patients undergoing TTM. Computer-derived values were statistically different than all manually derived values for QTc. The magnitude of the QTc was not different in patients exposed to QTc prolonging medication nor was the QTc different in those patients with and without malignant arrhythmia. As a result of this analysis, we can conclude that TH clearly prolongs the QT and the QTc and that this prolongation does not appear to
Acknowledgements
All authors had full access to all data in the study and take responsibility for the integrity of the data and accuracy of analysis. ZR, DM, SG contributed substantially to the writing of the manuscript and revising for critical intellectual content. All authors have provided final approval for the version to be published.
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Cited by (14)
QTc interval in survivors of out of hospital cardiac arrest
2021, International Journal of CardiologyCitation Excerpt :If intubated, patients are then transferred to intensive care, where iatrogenic lowering of body temperature (targeted temperature management (TTM)) is generally employed for its favourable effects on neurological recovery [9–11]. Post cardiac arrest, the appearance of a prolonged QTc interval on the surface electrocardiogram (ECG) has been described [12,13]. It is unclear whether this is a transient phenomenon, or a manifestation of an underlying arrhythmic substrate such as Long QT syndrome (LQTS).
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2023, Scandinavian Journal of Trauma, Resuscitation and Emergency MedicineMyocardial electrophysiological and mechanical changes caused by moderate hypothermia—A clinical study
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None of the authors report conflict of interest related to this work.