Proteomic Analysis of Serum Samples After Cardiac Arrest: a TTM-trial Substudy

Proteomic Analysis of Serum Samples After Cardiac Arrest: a TTM-trial Substudy

Cardiac arrest remains a large contributor to morbidity and mortality. Animal studies suggest an improvement in mortality and neurological function with hypothermia after cardiac arrest, a finding that could not be verified in large clinical trials such as Target Temperature Management after Out-of-hospital Cardiac arrest (TTM) trial. Multimodal neuroprognostication is an important tool for differentiating patients that will recover after cardiac arrest, and currently only one biomarker is in clinical use. The purpose of this study is to explore proteomics profiles in TTM trial patients in order to search for potential novel biomarkers, therapeutic targets, and to explore phenotypes of post-cardiac arrest syndrome.

Background: A pilot study investigating proteomic profiles from 78 patients from the Target Temperature Management after Out-of-hospital Cardiac arrest (TTM) trial revealed 35 proteins associated to functional outcome, and six proteins associated to targeted temperature management at 33 °C. We plan to investigate proteomic profiles in the full cohort of the previously collected TTM-trial biobank. The aim is to stratify protein profiles based on survival, functional outcome, targeted temperature management, and MIRACLE2 score in order to search for potential novel biomarkers, therapeutic targets, and to explore phenotypes of post-cardiac arrest syndrome.

Methods: All patients with available serum samples at 24, 48, and/or 72 hours after return of spontaneous circulation will be included in the liquid chromatography and tandem mass spectrometry analysis using diaPASEF, combining data-independent-acquisition of spectra with parallel accumulation-serial fragmentation. Statistical analysis will include data normalisation, exploratory principal component analysis, and differential expression analysis. Changes in serum protein abundance will be analysed according to survival and binary functional outcome (modified Rankin Scale 0-3 vs. 4-6) at six-months after randomisation, randomisation to target temperature of 33 °C or 36 °C, and the MIRACLE2 score. Secondary stratifications will include sex, age, time to return of spontaneous circulation, shockable vs. non-shockable initial rhythm, circulatory shock on admission, and presumed cause of death.

Conclusion: This study will provide information about proteomic profiles after cardiac arrest and may give insight for identification of novel biomarkers for prediction of outcome.

Inclusion Criteria as defined in the TTM trial (NCT01020916):

• Age ≥ 18 years old
• Out-of-hospital cardiac arrest (OHCA) of presumed cardiac cause
• Return of spontaneous circulation (ROSC)
• Unconsciousness (Glasgow Coma Score < 8) (patients not able to obey verbal commands) after sustained ROSC

Exclusion Criteria as defined in the TTM trial (NCT01020916):

• In-hospital cardiac arrest
• OHCA of presumed non-cardiac cause, e.g. after trauma or dissection/rupture of major artery OR Cardiac arrest caused by initial hypoxia (i.e. drowning, suffocation, hanging).
• Known bleeding diathesis (medically induced coagulopathy (e.g warfarin, clopidogrel) does not exclude the patient).
• Suspected or confirmed acute intracranial bleeding
• Suspected or confirmed acute stroke
• Unwitnessed asystole
• Known limitations in therapy and Do Not Resuscitate-order
• Known disease making 180 days survival unlikely
• Known pre-arrest CPC 3 or 4
• Temperature < 30°C on admission
• > 4 hours (240 minutes) from ROSC to screening
• Systolic blood pressure < 80 mm Hg in spite of fluid loading/vasopressor and/or inotropic medication/intra aortic balloon pump. If the systolic blood pressure (SBP) is recovering during the inclusion window (220 minutes) the patient can be included.