The Extent of Myocardial Injury During Prolonged Targeted Temperature Management After Out-of-Hospital Cardiac Arrest
The aim of this study is to evaluate the extent of myocardial injury by cardiac biomarkers during prolonged targeted temperature management of 24 hours vs 48 hours after out-of-hospital cardiac arrest.
This randomized Scandinavian multicenter study compares the extent of myocardial injury quantified by area under the curve (AUC) of cardiac biomarkers during prolonged targeted temperature management at 33°C ± 1°C of 24 hours and 48 hours, respectively. Through a period of 2.5 years, 161 comatose out-of-hospital cardiac arrest patients were randomized to targeted temperature management for 24 hours (n = 77) or 48 hours (n = 84). The AUC was calculated using both high-sensitivity cardiac troponin T (hs-cTnTAUC) and creatine kinase-myocardial band (CK-MBAUC) that were based upon measurements of these biomarkers every 6 hours upon admission until 96 hours after reaching target temperature.
The median hs-cTnTAUC of 33,827 ng/L/h (interquartile range [IQR] 11,366-117,690) of targeted temperature management at 24 hours did not differ significantly from that of 28,973 ng/L/h (IQR 10,656-163,655) at 48 hours. In contrast, the median CK-MBAUC of 1829 μg/L/h (IQR 800-6799) during targeted temperature management at 24 hours was significantly lower than that of 2428 μg/L/h (IQR 1163-10,906) within targeted temperature management at 48 hours, P <.05.
This study of comatose out-of-hospital cardiac arrest survivors showed no difference between the extents of myocardial injury estimated by hs-cTnTAUC of prolonged targeted temperature management of 48 hours vs 24 hours, although the CK-MBAUC was significantly higher during 48 hours vs 24 hours. Hence, it seems unlikely that the duration of targeted temperature management has a beneficial effect on the extent of myocardial injury after out-of-hospital cardiac arrest, and may even have a worsening effect.
Targeted temperature management is recommended as an integrated part of postresuscitation care after out-of-hospital cardiac arrest.1, 2, 3 Although the main goal with targeted temperature management is to reduce the cerebral injury and to improve survival,4, 5, 6 the practical value of the treatment to moderate the myocardial injury occurring in out-of-hospital cardiac arrest survivors has also been discussed for years.7, 8, 9, 10, 11, 12 The extent of myocardial injury, whether ischemic or nonischemic, is reflected by the released amount of cardiac biomarkers into the blood, enabling the assessment of area under the curve (AUC) and the determination of peak values. In this way, the AUC and the peak values of different cardiac biomarkers have been applied to evaluate the cardioprotective effect of targeted temperature management in newborns with perinatal asphyxia by means of cardiac troponin I (hs-cTnI) measurements13 and in adults by measuring creatine kinase and creatine kinase-myocardial band (CK-MB).7
The high-sensitivity cardiac troponin T (hs-cTnT) has been proven to be a more specific and sensitive indicator for myocardial injury than CK-MB,14 and its levels reflect myocardial injury well, following resuscitation after cardiac arrest.15 Additionally, it has been applied as a prognostic marker following targeted temperature management in data from the FINNRESUSCI study.16 Detection of an acute myocardial infarction in cardiac arrest patients is expedited by hs-cTnT measurements, even with confounding conditions due to the resuscitation per se and critical illness.17
However, factors like timing, cooling rate, depth, and length of targeted temperature management are still undetermined regarding the impact on the myocardial injury. Therefore, a potential demonstration of an alteration of the AUC of cardiac biomarkers through targeted temperature management, as an estimation of a cardioprotective effect, would be important. To the best of our knowledge, such an assessment of prolonged targeted temperature management in adult out-of-hospital cardiac arrest survivors has never been performed.
Thus, the aim of this study was to investigate whether there is a difference in the extent of myocardial injury as assessed by AUC of hs-cTnT and CK-MB of targeted temperature management at 33°C ± 1°C for 48 hours compared with 24 hours in out-of-hospital cardiac arrest survivors.
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-Anders Morten Grejs, MD, Jakob Gjedsted, MD, PhD, Kristian Thygesen, MD, DMSc, Jens Flensted Lassen, MD, PhD, Bodil Steen Rasmussen, MD, PhD, Anni Nørgaard Jeppesen, MD, Christophe Henri Valdemar Duez, MD, Eldar Søreide, MD, PhD, Hans Kirkegaard, MD, DMSc, PhD
This article originally appeared in the January 2017 issue of The American Journal of Medicine.