World Health Organization (WHO) states that approximately 7 million people died due to ischaemic heart diseases which include myocardial infarction, making it the leading cause of global death (WHO, 2017). Myocardial infarction, also known as heart attack, is characterized by clinical manifestations comprising of ischaemic symptoms, changes in electrocardiogram (ECG) readings and level of cardiac biomarkers, and imaging (Thygesen et al., 2012). One of the major complications of myocardial infarction is sudden cardiac death (Huikuri et al., 2001). By 2030, 23 million deaths are expected due to cardiovascular diseases, partly due to myocardial infarction (Mozaffarian et al., 2015). Global burden of ischaemic heart diseases increases as population and aging group expands (Moran et al., 2014). Healthcare expenditure and patients’ morbidity rise while patients’ productivity decreases due to incapability to work (Heidenreich et al., 2011; Johansson et al., 2017; Likosky et al., 2013; Oksak & Golovanova, 2017). Thus, it is important to have prevention and proper management of myocardial infarction through various approaches that are tailored according to patient’s needs and conditions (American College of Cardiology Foundation & American Heart Association, 2013). One of the measures proposed by national and international guidelines and cardiology bodies worldwide, is to consume omega-3 fatty acids either through diet or supplements (European Society of Cardiology, 2017; Kris-Etherton et al., 2002; Ministry of Health Malaysia, 2014; National Heart Foundation of Australia, 2008; WHO, 2003).
Omega-3 is a type of polyunsaturated fatty acid and also an essential fatty acid as human is unable to synthesize it and it can only be obtained exogenously (Covington, 2004; Simopoulos, 1991). It is an alpha-linolenic acid (ALA) that can be metabolized by human into commonly known components, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) (Covington, 2004; Simopoulos, 1991). Human can obtain EPA and DHA directly through their diet of fish, and ALA through vegetable oils (Covington, 2004; Kris-Etherton et al., 2000). Though it can be acquired through diet, omega-3 supplement is another option for people to obtain adequate amounts of EPA and DHA as suggested by the guidelines (Kris-Etherton et al., 2002; Kris-Etherton et al., 2000). Several studies reported that omega-3 exerts cardioprotective effects through its antiinflammatory and antithrombotic properties plus alteration of endothelial cells, cell membrane, ion channels, plasma lipoproteins, lipid metabolism and others (Jain et al., 2015; Jin & Makoto, 2016; Mozaffarian & Wu, 2011; Nestel et al., 2015).
Several systematic reviews and meta-analysis have been published to assess the cardiovascular benefits of omega-3 (Delgado-Lista et al., 2012; Enns et al., 2014; Kotwal et al., 2012; Kwak et al., 2012; Rizos et al., 2012). However, these systematic reviews have mixed and contradictory results and focused on peripheral arterial disease (Delgado-Lista et al., 2012; Enns et al., 2014; Kotwal et al., 2012; Kwak et al., 2012; Rizos et al., 2012). Additionally these reviews, included open-label studies or studies with secondary prevention or trials which considered omega-3 source from supplement only or marine source alone (Delgado-Lista et al., 2012; Enns et al., 2014; Kotwal et al., 2012; Kwak et al., 2012; Rizos et al., 2012). The aim of the study will be to assess the effects of omega-3, from all sources and as primary and secondary prevention, on risk of myocardial infarction by conducting meta-analysis on randomised controlled trials. The findings of this systematic review will provide updated evidence and determine the presences and extent of usefulness of omega-3 administration in people with myocardial infarction and those with risk of the disease.