Out-of-hospital Cardiac Arrest (OHCA) Biomarkers

Aggressive treatment for patients with out-of-hospital cardiac arrest (OHCA) can result in
return of spontaneous circulation (ROSC). However, prognosis for these patients remains poor,
with low rates of survival to hospital admission and low rates of survival to hospital
discharge. Furthermore, due to the exquisite sensitivity to hypoxic injury of neural tissue
(dependent on aerobic respiration) relative to that of cardiac muscle, patients for whom ROSC
can be obtained often suffer devastating neurological injury, with potential poor long-term
neurological outcome. In some ischemic processes, for example, myocardial infarction, rapid
measurement of cardiac biomarkers (e.g. Troponin isoform) is invaluable to current diagnosis
and management. However, with regards to ischemic brain injury, there is currently no rapid,
definitive diagnostic test to prognosticate outcome in OHCA. Biomarkers measurable in blood
would have vital applications in prognosis and clinical research of neurological outcome in
OHCA.

Other groups have studied the neurological predictive values of biomarkers after OHCA. A
variety of proteins including S100B, neuron-specific enolase, and G-FAP, co-peptin, Tau,
neurofilament light/ heavy chain, and secretoneurin have been proposed as potential
biomarkers of neurological outcome at OHCA. Unfortunately, many of these have been shown to
have several drawbacks. For example, some lack specificity due to being released during
resuscitation (e.g., S100B is found extracerebrally in muscle, adipocytes, and chondrocytes,
creating a confounding factor in CA patients receiving chest compressions). Others have
lacked sufficient sensitivity in the prognosticating of neurological outcome (ref).
Furthermore, there is a paucity of human studies in cardiac arrest on newer biomarkers that
have been studied in other acute brain injury disease processes that could potentially serve
as candidate biomarkers predicting neurological outcome at post cardiac arrest hypoxic brain
injuries. Biomarkers such as UCH-L1, SBDP, and MBP have not been studied in a OHCA cohort.

The Investigator therefore propose a prospective, observational study in which the
investigator will incorporate a minimally invasive and minimal risk measurement of blood
biomarkers at time of ROSC. This would be done by drawing blood at ROSC (0-59mins), and
additional blood draws at hours 6, 12, 18, 24, 48, 72, and on day 4, 5, and 6. The
Investigator will then determine whether biomarker levels correlates with survival to
hospital admission, survival to hospital discharge, and functional neurologic outcome at
discharge and at 6 months. The Investigator intend to sample patients that present to the
emergency department with non-CA chest pain in our study as well, which will allow us to draw
stable inferences.

Inclusion Criteria:

- >18 years old

Study cohort:

- Non-traumatic out of hospital cardiac arrest

- Control cohort:

- Chest pain of non-cardiac etiology

Exclusion Criteria:

Both cohorts:

- Females of child bearing age with positive pregnancy test

- Neurodegenerative disease or other neurological disorder (dementia, Parkinson's
disease, multiple sclerosis, seizure disorder, or brain tumours)

- History of neurosurgery within the last 30 days Acute brain injury within the last 30
days (ischemic/ haemorrhagic stroke, traumatic brain injury) Subject is anemic OR
donated blood within the last 8 weeks OR has a hematological disorder that requires
transfusions Subject has history of liver failure OR renal failure

Study cohort:

Advanced directives against resuscitation Traumatic cardiac arrest In hospital cardiac
arrest Failure to attain ROSC + visible signs of death (livor mortis, rigor mortis)

Control cohort:

EKG changes: New ST-elevation consistent with myocardial infarction NSTEMI Hemodynamically
unstable