Cognitive function after cardiac arrest and temperature management; rationale and description of a sub-study in the Target Temperature Management trial

Effects of Hypothermia vs Normothermia on Societal Participation and Cognitive Function at 6 Months in Survivors After Out-of-Hospital Cardiac Arrest: A Predefined Analysis of the TTM2 Randomized Clinical Trial

Importance

The Targeted Hypothermia vs Targeted Normothermia After Out-of-Hospital Cardiac Arrest (TTM2) trial reported no difference in mortality or poor functional outcome at 6 months after out-of-hospital cardiac arrest (OHCA). This predefined exploratory analysis provides more detailed estimation of brain dysfunction for the comparison of the 2 intervention regimens.

Objectives

To investigate the effects of targeted hypothermia vs targeted normothermia on functional outcome with focus on societal participation and cognitive function in survivors 6 months after OHCA.

Design, Setting, and Participants

This study is a predefined analysis of an international multicenter, randomized clinical trial that took place from November 2017 to January 2020 and included participants at 61 hospitals in 14 countries. A structured follow-up for survivors performed at 6 months was by masked outcome assessors. The last follow-up took place in October 2020. Participants included 1861 adult (older than 18 years) patients with OHCA who were comatose at hospital admission. At 6 months, 939 of 1861 were alive and invited to a follow-up, of which 103 of 939 declined or were missing.

Interventions

Randomization 1:1 to temperature control with targeted hypothermia at 33 °C or targeted normothermia and early treatment of fever (37.8 °C or higher).

Main outcomes and measures

Functional outcome focusing on societal participation assessed by the Glasgow Outcome Scale Extended ([GOSE] 1 to 8) and cognitive function assessed by the Montreal Cognitive Assessment ([MoCA] 0 to 30) and the Symbol Digit Modalities Test ([SDMT] z scores). Higher scores represent better outcomes.

Results

At 6 months, 836 of 939 survivors with a mean age of 60 (SD, 13) (range, 18 to 88) years (700 of 836 male [84%]) participated in the follow-up. There were no differences between the 2 intervention groups in functional outcome focusing on societal participation (GOSE score, odds ratio, 0.91; 95% CI, 0.71-1.17; P = .46) or in cognitive function by MoCA (mean difference, 0.36; 95% CI,-0.33 to 1.05; P = .37) and SDMT (mean difference, 0.06; 95% CI,-0.16 to 0.27; P = .62). Limitations in societal participation (GOSE score less than 7) were common regardless of intervention (hypothermia, 178 of 415 [43%]; normothermia, 168 of 419 [40%]). Cognitive impairment was identified in 353 of 599 survivors (59%).

Conclusions

In this predefined analysis of comatose patients after OHCA, hypothermia did not lead to better functional outcome assessed with a focus on societal participation and cognitive function than management with normothermia. At 6 months, many survivors had not regained their pre-arrest activities and roles, and mild cognitive dysfunction was common.

Trial Registration

ClinicalTrials.gov Identifier: NCT02908308.

Self-reported limitations in physical function are common 6 months after out-of-hospital cardiac arrest

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Limitations in physical function are common in cardiac arrest survivors.

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Age and gender are associated with limitations in physical function.

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Cognitive impairment is a predictive variable for physical limitations.

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Anxiety and depression symptoms are associated with physical limitations.

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Physical function should be addressed at follow-up after cardiac arrest.

Title

Self-reported limitations in physical function are common 6 months after out-of-hospital cardiac arrest.

Background

Out-of-hospital cardiac arrest (OHCA) survivors generally report good health-related quality of life, but physical aspects of health seem more affected than other domains. Limitations in physical function after surviving OHCA have received little attention.

Aims

To describe physical function 6 months after OHCA and compare it with a group of ST elevation myocardial infarction (STEMI) controls, matched for country, age, sex and time of the cardiac event. A second aim was to explore variables potentially associated with self-reported limitations in physical function in OHCA survivors.

Methods

A cross-sectional sub-study of the Targeted Temperature Management at 33 °C versus 36 °C (TTM) trial with a follow-up 6 months post-event. Physical function was the main outcome assessed with the self-reported Physical Functioning-10 items scale (PF-10). PF-10 is presented as T-scores (0–100), where 50 represents the norm mean. Scores <47 at a group level, or <45 at an individual level indicate limitations in physical function.

Results

287 OHCA survivors and 119 STEMI controls participated. Self-reported physical function by PF-10 was significantly lower for OHCA survivors compared to STEMI controls (mean 46.0, SD 11.2 vs. 48.8, SD 9.0, p = 0.025). 38% of OHCA survivors compared to 26% of STEMI controls reported limitations in physical function at an individual level (p = 0.022). The most predictive variables for self-reported limitations in physical function in OHCA survivors were older age, female sex, cognitive impairment, and symptoms of anxiety and depression after 6 months.

Conclusion

Self-reported limitations in physical function are more common in OHCA survivors compared to STEMI controls.

Trial registration

ClinicalTrials.gov Identifier: NCT01946932.

Protocol summary and statistical analysis plan for the Targeted Therapeutic Mild Hypercapnia after Resuscitated Cardiac Arrest (TAME) trial

Background: Targeted therapeutic mild hypercapnia may attenuate brain injury in comatose adults resuscitated from out-of-hospital cardiac arrest. Objective: To describe the study protocol and statistical analysis plan for the Targeted Therapeutic Mild Hypercapnia after Resuscitated Cardiac Arrest (TAME) trial. Design, setting, participants and interventions: TAME is a phase 3, multicentre, parallel-group, participant- and outcome assessor-blinded randomised controlled trial that will be conducted in intensive care units in Australia, Canada, Ireland, Saudi Arabia, New Zealand, Scandinavia, Singapore, Central and Western Europe, and the United Kingdom. A total of 1700 comatose adults resuscitated from out-of-hospital cardiac arrest will be randomly assigned to 24 hours of targeted therapeutic mild hypercapnia (arterial carbon dioxide tension 50-55 mmHg) or targeted normocapnia (arterial carbon dioxide tension 35-45 mmHg) in a 1:1 ratio. TAME recruitment began in March 2018 and is expected to be complete in September 2021. Main outcome measures: The primary outcome measure is the proportion of participants with a favourable functional outcome at 6 months. Functional outcomes will be assessed using the Glasgow Outcome Scale-Extended (GOSE); this scale ranges from 1 to 8, with a higher value indicating a better outcome. We will define participants with a GOSE of 5 to 8 as having a favourable functional outcome. Secondary outcomes include 6-month mortality, cognitive function and quality of life. All analyses will be conducted on an intention-to-treat basis. Results and conclusions: TAME will compare the effect of targeted therapeutic mild hypercapnia versus targeted normocapnia on functional outcomes in adults resuscitated from out-of-hospital cardiac arrest who are admitted to an intensive care unit. Trial registration: Australian and New Zealand Clinical Trials Registry (ACTRN12617000036314p) and ClinicalTrials.gov (NCT03114033).

Caregiver burden and health-related quality of life amongst caregivers of out-of-hospital cardiac arrest survivors

AIMS

To describe burden and health-related quality of life amongst caregivers of out-of-hospital cardiac arrest survivors and explore the potential association with cognitive function of the survivors. Caregivers of patients with ST-elevation myocardial infarction were used as controls.

METHODS

Data were collected from the cognitive substudy of the Targeted Temperature Management-trial. Caregiver burden was assessed with the 22-item Zarit Burden Interview, with scores ≤20 considered as no burden. Health-related quality of life was assessed with the SF-36v2®, with T-scores 47-53 representing the norm. Cardiac arrest survivors were categorized based on the results from cognitive assessments as having "no cognitive impairment" or "cognitive impairment".

RESULTS

Follow-up 6 months post event was performed for caregivers of 272 cardiac arrest survivors and 108 matched myocardial infarction controls, included at an intended ratio of 2:1. In general, caregivers of cardiac arrest survivors and controls reported similar caregiver burden. The overall scores for quality of life were within normative levels and similar for caregivers of cardiac arrest survivors and control patients. Compared to those with no cognitive impairment, caregivers of cognitively impaired cardiac arrest survivors (n = 126) reported higher levels of burden (median 18 versus 8, p < 0.001) and worse quality of life in five of eight domains, particularly "Role-Emotional" (mean 45.7 versus 49.5, p = 0.002).

CONCLUSIONS

In general, caregivers of cardiac arrest survivors and myocardial infarction controls reported similar levels of burden and quality of life. Cognitive outcome and functional dependency of the cardiac arrest survivor impact burden and quality of life of the caregiver.

Long-term physical and psychological outcomes after out-of-hospital cardiac arrest-protocol for a national cross-sectional survey of survivors and their relatives (the DANCAS survey)

INTRODUCTION

The number of out-of-hospital cardiac arrest (OHCA) survivors is increasing. However, there remains limited knowledge on the long-term physical and psychological problems suffered by survivors and their relatives. The aims of the DANCAS (DANish cardiac arrest survivorship) survey are to describe the prevalence of physical and psychological problems, identify predictors associated with suffering them and to determine unmet rehabilitation needs in order to make recommendations on the timing and content of future rehabilitation interventions.

METHODS AND ANALYSIS

The DANCAS survey has a cross-sectional design involving a survey of OHCA survivors and their relatives. OHCA survivors will be identified through the Danish Cardiac Arrest Registry as having suffered an OHCA between 1 January 2016 and 31 December 2019. Each survivor will be asked to identify their closest relative to complete the relatives' survey. Contents of survivor survey: EQ-5D-5Level, Hospital Anxiety and Depression Scale, Two Simple Questions, Modified Fatigue Impact Scale, 12-item WHO Disability Assessment Scale 2.0, plus questions on unmet rehabilitation and information needs. Contents of relatives' survey: World Health Organisation-Five Well-Being Index, Hospital Anxiety and Depression Scale, Informant Questionnaire on Cognitive Decline in the Elderly-Cardiac Arrest and the Modified Caregiver Strain Index. Self-report outcome data collected through the surveys will be enriched by data from Danish national registries including demographic characteristics, circumstances of cardiac arrest and comorbidities. The survey will be completed either electronically or by post December 2020-February 2021.

ETHICS AND DISSEMINATION

The study will be conducted in accordance with the Declaration of Helsinki. Surveys and registry-based research studies do not normally require ethical approval in Denmark. This has been confirmed for this study by the Region of Southern Denmark ethics committee (20192000-19). Results of the study will be disseminated via several peer-reviewed publications and will be presented at national and international conferences.

Protocol for outcome reporting and follow-up in the Targeted Hypothermia versus Targeted Normothermia after Out-of-Hospital Cardiac Arrest trial (TTM2)

AIMS

The TTM2-trial is a multi-centre randomised clinical trial where targeted temperature management (TTM) at 33 °C will be compared with normothermia and early treatment of fever (≥37.8 °C) after Out-of-Hospital Cardiac Arrest (OHCA). This paper presents the design and rationale of the TTM2-trial follow-up, where information on secondary and exploratory outcomes will be collected. We also present the explorative outcome analyses which will focus on neurocognitive function and societal participation in OHCA-survivors.

METHODS

Blinded outcome-assessors will perform follow-up at 30-days after the OHCA with a telephone interview, including the modified Rankin Scale (mRS) and the Glasgow Outcome Scale Extended (GOSE). Face-to-face meetings will be performed at 6 and 24-months, and include reports on outcome from several sources of information: clinician-reported: mRS, GOSE; patient-reported: EuroQol-5 Dimensions-5 Level responses version (EQ-5D-5L), Life satisfaction, Two Simple Questions; observer-reported: Informant Questionnaire on Cognitive Decline in the Elderly-Cardiac Arrest version (IQCODE-CA) and neurocognitive performance measures: Montreal Cognitive Assessment, (MoCA), Symbol Digit Modalities Test (SDMT). Exploratory analyses will be performed with an emphasis on brain injury in the survivors, where the two intervention groups will be compared for potential differences in neuro-cognitive function (MoCA, SDMT) and societal participation (GOSE). Strategies to increase inter-rater reliability and decrease missing data are described.

DISCUSSION

The TTM2-trial follow-up is a pragmatic yet detailed pre-planned and standardised assessment of patient's outcome designed to ensure data-quality, decrease missing data and provide optimal conditions to investigate clinically relevant effects of TTM, including OHCA-survivors' neurocognitive function and societal participation.

Gender differences in cognitive outcome after cardiac arrest: A retrospective cohort study

Introduction: Recent studies have suggested gender disparities in neurologic outcome after cardiac arrest (CA). However, the relation between gender and cognitive outcome has been rarely examined. Here we investigated whether sex is associated with cognitive outcome after CA events.Methods: A retrospective analysis was conducted using data collected at our institution from January 2006 to May 2017. Patients were included if they had a documented CA and were able to participate in structured neuropsychological testing. Cognitive status was assessed at about 2.1 month after CA and included tests of attention as well as short and long-term memory. Gender was used as the main predictor of outcome and was studied in relation to age, depressive mood, therapeutic hypothermia (TH), and other potential confounders.Results: Males were more likely to show favorable cognitive outcome in both univariate and multivariate analyses. Women were more likely to exhibit depressive mood. Patients who underwent TH (31% of the patients) did not show any gender differences in benefits from the treatment. Among males and females, no significant differences between age groups could be observed.Conclusions: Male sex was associated with favorable cognitive outcome after CA which could not be attributed to baseline characteristics.

Arterial blood pressure during targeted temperature management after out-of-hospital cardiac arrest and association with brain injury and long-term cognitive function

OBJECTIVES

During targeted temperature management after out-of-hospital cardiac arrest infusion of vasoactive drugs is often needed to ensure cerebral perfusion pressure. This study investigated mean arterial pressure after out-of-hospital cardiac arrest and the association with brain injury and long-term cognitive function.

METHODS

Post-hoc analysis of patients surviving at least 48 hours in the biobank substudy of the targeted temperature management trial with available blood pressure data. Patients were stratified in three groups according to mean arterial pressure during targeted temperature management (4-28 hours after admission; <70 mmHg, 70-80 mmHg, >80 mmHg). A biomarker of brain injury, neuron-specific enolase, was measured and impaired cognitive function was defined as a mini-mental state examination score below 27 in 6-month survivors.

RESULTS

Of the 657 patients included in the present analysis, 154 (23%) had mean arterial pressure less than 70 mmHg, 288 (44%) had mean arterial pressure between 70 and 80 mmHg and 215 (33%) had mean arterial pressure greater than 80 mmHg. There were no statistically significant differences in survival (P=0.35) or neuron-specific enolase levels (P=0.12) between the groups. The level of target temperature did not statistically significantly interact with mean arterial pressure regarding neuron-specific enolase (P_{interaction_MAP*TTM}=0.58). In the subgroup of survivors with impaired cognitive function (n=132) (35%) mean arterial pressure during targeted temperature management was significantly higher (P_group=0.03).

CONCLUSIONS

In a large cohort of comatose out-of-hospital cardiac arrest patients, low mean arterial pressure during targeted temperature management was not associated with higher neuron-specific enolase regardless of the level of target temperature (33°C or 36°C for 24 hours). In survivors with impaired cognitive function, mean arterial pressure during targeted temperature management was significantly higher.

Design of DISCO-Direct or Subacute Coronary Angiography in Out-of-Hospital Cardiac Arrest study

BACKGROUND

Acute coronary syndrome is a common cause of out-of-hospital cardiac arrest (OHCA). In patients with OHCA presenting with ST elevation, immediate coronary angiography and potential percutaneous coronary intervention (PCI) after return of spontaneous circulation are recommended. However, the evidence for this invasive strategy in patients without ST elevation is limited. Observational studies have shown a culprit coronary artery occlusion in about 30% of these patients, indicating the electrocardiogram's (ECG's) limited sensitivity. The aim of this study is to determine whether immediate coronary angiography and subsequent PCI will provide outcome benefits in OHCA patients without ST elevation.

METHODS/DESIGN

We describe the design of the DIrect or Subacute Coronary angiography in Out-of-hospital cardiac arrest study (DISCO)-a pragmatic national, multicenter, randomized, clinical study. OHCA patients presenting with no ST elevation on their first recorded ECG will be randomized to a strategy of immediate coronary angiography or to standard of care with admission to intensive care and angiography after 3days at the earliest unless the patient shows signs of acute ischemia or hemodynamic instability. Primary end point is 30-day survival. An estimated 1,006 patients give 80% power (α = .05) to detect a 20% improved 30-day survival rate from 45% to 54%. Secondary outcomes include good neurologic recovery at 30days and 6months, and cognitive function and cardiac function at 6months.

CONCLUSION

This randomized clinical study will evaluate the effect of immediate coronary angiography after OHCA on 30-day survival in patients without ST elevation on their first recorded ECG.

Anxiety and depression among out-of-hospital cardiac arrest survivors

AIM

Survivors of out-of-hospital cardiac arrest (OHCA) may experience psychological distress but the actual prevalence is unknown. The aim of this study was to investigate anxiety and depression within a large cohort of OHCA-survivors.

METHODS

OHCA-survivors randomized to targeted temperature of 33 °C or 36 °C within the Target Temperature Management trial (TTM-trial) attended a follow-up after 6 months that included the questionnaire Hospital Anxiety and Depression Scale (HADS). A control group with ST-elevation myocardial infarction (STEMI) completed the same follow-up. Correlations to variables assumed to be associated with anxiety and depression in OHCA-survivors were tested.

RESULTS

At follow-up 278 OHCA-survivors and 119 STEMI-controls completed the HADS where 24% of OHCA-survivors (28% in 33 °C group/22% in 36 °C group, p=0.83) and 19% of the STEMI-controls reported symptoms of anxiety (OR 1.32; 95% CI (0.78-2.25), p=0.30). Depressive symptoms were reported by 13% of OHCA-survivors (equal in both intervention groups, p=0.96) and 8% of STEMI-controls (OR 1.76; 95% CI (0.82-3.79), p=0.15). Anxiety and depression among OHCA-survivors correlated to Health-Related Quality-of-Life, and subjectively reported cognitive deterioration by patient or observer. In addition, depression was associated with a poor neurological outcome.

CONCLUSION

One fourth of OHCA-survivors reported symptoms of anxiety and/or depression at 6 months which was similar to STEMI-controls and previous normative data. Subjective cognitive problems were associated with an increased risk for psychological distress. Since psychological distress affects long-term prognosis of cardiac patients in general it should be addressed during follow-up of survivors with OHCA due to a cardiac cause. ClinicalTrials.gov NCT01020916/NCT01946932.

Interpreting the results of the targeted temperature management trial in cardiac arrest

The targeted temperature management (TTM) trial, which found that cooling to 33°C after witnessed cardiac arrest (CA) conferred no benefits compared with 36°C, has led to much debate in the hypothermia community. This article discusses what lessons can be drawn. The TTM trial achieved far better outcomes in controls than any previous randomized controlled trial (RCT) or any nonrandomized study where no fever control was applied. On the other hand, rates of good outcomes in the hypothermia group were somewhat lower than in previous RCTs and most nonrandomized studies. The TTM authors conclude that benefits of temperature management are derived exclusively from fever control and that further lowering of temperature confers no benefit. Indeed, without doubt, the TTM trial demonstrates the crucial importance of strict fever control after CA and that this provides sufficient neuroprotection for some patients. However, we argue that the hypothermia intervention was executed suboptimally (possibly inadvertent selection bias; late start of cooling, up to 4 hours after ROSC; slow cooling rates, 10 hours to target temperature; more rapid rewarming than previous studies; and some other issues). This could explain high rates of good outcomes in controls and lower-than-expected rates in patients cooled to 33°C compared with previous randomized and nonrandomized studies. Outside of two previous RCTs, the use of hypothermia after CA is supported by hundreds of animal experiments, evidence from 46 before-after studies and large registries, and indirect supporting evidence from 7 RCTs in newborns with neonatal asphyxia. In addition, one RCT found improved outcomes with 32°C compared with 34°C. It remains to be explained why the TTM results so completely contradict previous studies in this field. These issues should be thoroughly discussed before changes in guidelines and protocols are made. Ending or modifying hypothermia treatment after CA should require the strongest possible evidence.

Cognitive function in survivors of out-of-hospital cardiac arrest after target temperature management at 33°C versus 36°C

BACKGROUND

Target temperature management is recommended as a neuroprotective strategy after out-of-hospital cardiac arrest. Potential effects of different target temperatures on cognitive impairment commonly described in survivors have not been investigated sufficiently. The primary aim of this study was to evaluate whether a target temperature of 33°C compared with 36°C was favorable for cognitive function; the secondary aim was to describe cognitive impairment in cardiac arrest survivors in general.

METHODS AND RESULTS

Study sites included 652 cardiac arrest survivors originally randomized and stratified for site to temperature control at 33°C or 36°C within the Target Temperature Management trial. Survival until 180 days after the arrest was 52% (33°C, n=178/328; 36°C, n=164/324). Survivors were invited to a face-to-face follow-up, and 287 cardiac arrest survivors (33°C, n=148/36°C, n=139) were assessed with tests for memory (Rivermead Behavioural Memory Test), executive functions (Frontal Assessment Battery), and attention/mental speed (Symbol Digit Modalities Test). A control group of 119 matched patients hospitalized for acute ST-segment-elevation myocardial infarction without cardiac arrest performed the same assessments. Half of the cardiac arrest survivors had cognitive impairment, which was mostly mild. Cognitive outcome did not differ (P>0.30) between the 2 temperature groups (33°C/36°C). Compared with control subjects with ST-segment-elevation myocardial infarction, attention/mental speed was more affected among cardiac arrest patients, but results for memory and executive functioning were similar.

CONCLUSIONS

Cognitive function was comparable in survivors of out-of-hospital cardiac arrest when a temperature of 33°C and 36°C was targeted. Cognitive impairment detected in cardiac arrest survivors was also common in matched control subjects with ST-segment-elevation myocardial infarction not having had a cardiac arrest.

CLINICAL TRIAL REGISTRATION

URL: http://www.clinicaltrials.gov. Unique identifier: NCT01946932.