The effect of targeted temperature management on QT and corrected QT intervals in patients with cardiac arrest

doi:10.1016/j.jcrc.2017.02.030

Journal of Critical Care

Volume 39, June 2017, Pages 182-184

https://doi.org/10.1016/j.jcrc.2017.02.030 Get rights and content

Highlights

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QT and QTC intervals prolong during TTM after cardiac arrest.
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QT and QTC duration were not affected by medication.
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Qtc was not different in patients with and without malignant arrhythmias.

Abstract

Background

Targeted Temperature Management (TTM) improves outcomes after cardiac arrest but may affect the QT and QTc intervals which could increase the chance of subsequent arrhythmia. We report here the effects of TTM on both computer-derived and manually calculated QT and QTc as well as the relationship of the length of the QTc and serious arrhythmia in a retrospective single-center experience.

Methods

193 patients undergoing TTM for cardiac arrest were studied. 12-lead electrocardiograms (ECG) were measured before, during and after TTM. We assessed the QT and Bazett-corrected QT intervals (QTc) and examined the relationship between QTc and the occurrence of malignant arrhythmias.

Results

Both the QT and QTc increased during TTM whether derived manually or from the computer algorithm, although values were different with the two methods. Neither the QT nor the QTc were significantly longer in those patients with malignant arrhythmias.

Conclusions

QT and QTc prolong during TTM. There was no differential increase in the QTc in patients who experienced malignant arrhythmias. While the mechanism of QTc prolongation is not clear, it would not appear that the degree of QTc prolongation has an adverse effect on cardiac rhythm during TTM.

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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There are more references available in the full text version of this article.

Cited by (14)

QTc interval in survivors of out of hospital cardiac arrest
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Citation 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).
QTc interval (QTc) prolongation is seen on the post-arrest electrocardiogram (ECG) of many out of hospital cardiac arrest (OHCA) survivors. It remains unclear whether this is a transient phenomenon or a manifestation of an underlying arrhythmic substrate.
This observational study assessed the trend of QTc in an unselected group of patients presenting with OHCA. We sought to identify any relationship between QTc, gender and aetiology of arrest. We observed whether targeted temperature management (TTM) is associated with malignant arrhythmia.
We analysed 60 patients presenting with OHCA to the Bristol Heart Institute during a 20-month period. We measured QTc on admission and assessed for persistence, development and resolution of prolongation at up to 5 time points post-OHCA. Aetiology of arrest was divided into coronary, non-coronary or primary arrhythmic to investigate for patterns in QTc behaviour.
81.7% (49/60) of arrests were attributed to an acute coronary event. 55% (33/60) had QTc prolongation on admission, of which 79% resolved. There were no significant differences in QTc behaviour by aetiology.
One patient presenting with a normal QTc, developed prolongation during admission and received a genetic diagnosis of Long QT Syndrome. TTM was employed in 57/60, with no increased incidence of malignant arrhythmia.
Prolonged QTc on admission does not imply a primary arrhythmic aetiology and resolves in the majority pre-discharge. However, an initial normal QTc post-OHCA does not preclude a diagnosis of Long QT syndrome, highlighting the importance of thorough investigations in these patients. TTM appears safe from a cardiac perspective.
Remodeling of the 12-lead electrocardiogram in immediate survivors of sudden cardiac arrest
2020, Resuscitation
Citation Excerpt :
To our knowledge, this is the first prospective study to assess SCA-induced electrical abnormalities compared to baseline measurements obtained from ECGs prior and unrelated to the SCA event. While several prior studies have shown that the QT and QTc increase at least temporarily after cardiac arrest,5,6,12,13 our investigation offers several key differences/advantages: for one, these prior studies looked at post-resuscitation electrical changes in either very specific clinical settings such as during targeted temperature management (TTM) therapy or in the setting of pre-existing known inherited conduction disease. Accordingly, with these prior studies, it was unclear whether findings were related to the arrest, subsequent intervention, or pre-existing substrate.
The ECG is a critical diagnostic tool for the management of immediate sudden cardiac arrest (SCA) survivors, but can be altered as a consequence of the SCA event. A limited number of studies report that electrical remodeling post SCA is due to prolonged myocardial repolarization, but a better understanding of this phenomenon is needed.
To identify specific ECG abnormalities that follow SCA in immediate survivors.
SCA survivors with a pre-arrest ECG and an ECG obtained within 48 h post-SCA were prospectively collected in the Oregon Sudden Unexpected Death Study (Portland metro region) from 2002–2015. Ventricular depolarization and repolarization measurements were compared between pre-arrest and post-arrest ECGs using paired t-tests and assessed for association with survival using unpaired t-tests and Pearson’s chi-square tests.
A pre-arrest ECG and post-arrest ECG were available for 297 SCA cases (67.8 ± 13.4 years; 65.3% male). From the pre- to post-arrest setting, there was a significant mean increase in QRS (21 ms, p < 0.001) and QTc (35 ms, p < 0.001) in each SCA case, while there was no significant change in the JTc (4 ms, p = 0.361). Post-arrest QRS duration was significantly shorter in cases who survived to hospital discharge compared with those who did not survive (mean QRSD 115 ± 29 ms vs 127 ± 34 ms; p = 0.006).
Contrary to expectations, electrical remodeling of the ECG due to SCA occurs due to prolongation of ventricular depolarization (QRSD), and not repolarization (JTc). Prolonged QRSD may also assist with prognostication and warrants further evaluation.
Proarrhythmic changes in human cardiomyocytes during hypothermia by milrinone and isoprenaline, but not levosimendan: an experimental in vitro study
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2022, Biology
Myocardial electrophysiological and mechanical changes caused by moderate hypothermia—A clinical study
2022, Physiological Reports
Characterization of the adult zebrafish electrocardiogram
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^☆: None of the authors report conflict of interest related to this work.

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Clinical PotpourriThe effect of targeted temperature management on QT and corrected QT intervals in patients with cardiac arrest☆

Highlights

Abstract

Background

Methods

Results

Conclusions

Introduction

Section snippets

Methods

Results

Discussion

Conclusion

Acknowledgements

Am J Med

Heart Rhythm

Resuscitation

Treatment of comatose survivors of out-of-hospital cardiac arrest with induced hypothermia

N Engl J Med

Mild therapeutic hypothermia to improve the neurologic outcome after cardiac arrest

N Engl J Med

Part 1: executive summary: 2015 American Heart Association guidelines update for cardiopulmonary resuscitation and emergency cardiovascular care

Circulation

Clinical Potpourri
The effect of targeted temperature management on QT and corrected QT intervals in patients with cardiac arrest☆