DIagnostics, RBC Levels of n-3 Fatty Acids and Serum Vitamin D in Patients With Out-of-Hospital Cardiac Arrest (OHCA)

Background:

Sudden cardiac death (SCD), also termed sudden cardiac arrest (SCA), accounts for approximately 15 percent of the total mortality in industrialized countries. In Europe, the incidence of out-of-hospital Emergency Medical Services (EMS) attended sudden cardiac arrest (SCA) is estimated to 81.6/100 000 person-years, 52.5 % of which is presumed to have a cardiac cause [1]. Coronary artery disease (CAD) is the most common underlying heart disease associated with out-of-hospital cardiac arrest (OHCA) [2]. SCD is the initial presentation of CAD in 15 percent of CAD-patients [3]. Furthermore, it is also the most frequent mechanism of death in patients with known CAD, accounting for 40-50 percent of CAD-mortality [4]. Compared to healthy subjects the incidence of SCD is six- to tenfold higher in the presence of clinically recognized heart disease [5], and cardiomyopathies represents the second largest cause of SCD [6]. Despite early advanced cardiopulmonary resuscitation (CPR) provided by the EMS the mortality rate remains high [1]. Due to the dramatic consequence of SCA, understanding of pathophysiological mechanisms and early identification of etiology is essential to improve outcome.

SCA due to VF may be the presenting symptom of acute myocardial ischemia or may be a consequence of scarring due to a previous myocardial infarction (MI). Cardiac troponin (c-Tn) is the most commonly used biomarker for diagnosing an acute myocardial infarction (AMI) [7]. Although earlier detection of AMI may be obtained by the introduction of high sensitivity (hs)-cTn assays, there still remains a troponin-blind period very early after symptom onset [8, 9], with the need for serial blood sampling to diagnose or exclude an AMI [7, 9]. Furthermore, there are challenges related to the specificity of elevated levels of hs-cTn [10, 11]. Therefore, measurement of hs-cTn in a single blood draw in the ambulance or at admission may not provide sufficient information for the diagnosis of AMI among patients with OHCA.

Lately, several studies have demonstrated an incremental diagnostic value of copeptin when added to conventional cTn or hs-cTn for early detection of AMI [12, 13]. Copeptin levels peak early (0-1 h) after symptom onset and are already increased at the time of first medical contact in the ambulance for patients with MI [8]. Copeptin used in combination with hs-cTn may therefore improve the diagnosis of AMI in very early presenters, and help differentiating the underlying cause of SCD.

Copeptin has also been demonstrated to be an independent predictor of adverse events following MI [14] and is shown to be associated with outcome after OHCA [15, 16]. Less is known about the prognostic value of troponins in patients experiencing a cardiac arrest (CA). Higher values of hs-cTnT are seen in one-year non-survivors as compared to survivors of OHCA, although not shown to be an independent predictor of 12-months survival [10]. In our study, the objective will be to evaluate the diagnostic and prognostic utility of hs-cTnT and copeptin in SCA patients.