Mini review: Sudden cardiac death (2017)

Sudden cardiac death (SCD) is a sudden unexpected death due to a demise of the myocardium. SCD also includes an acute precipitating trigger that lies in the brain and a chronic electrical instability of the myocardium. Most SCDs in absolute terms occur in subjects with no known pre-existing heart disease. The incidence of SCD may be about 20% per year in patients with heart failure and those with markers of arrhythmias, compared with about 1-2% in the general population, i.e., subjects with no “known” pre-existing heart disease. Some early symptoms of SCD include fatigue, fainting, blackouts and dizziness due to blood stopping to flow to the brain and other organs of the body. SCD is responsible for a sizable portion of the over 19 million deaths globally each year from CVDs. Acute anxiety, hypertension, hyperlipidemia, family history, arrhythmias, diabetes mellitus, prediabetes, metabolic syndrome and obesity are risk factors to precipitate SCD. In addition, other behavioral risk factors including type A personality, physical inactivity, smoking, male gender, women after menopause, unhealthy diet and modern lifestyle, such as regularly eating fast foods or foods rich in saturated fats, and late-night sleep; excess sugar, alcohol and salt intake can also predispose to SCD. Deficiency in some cations and vitamins, especially magnesium, potassium, flavonoids and trace elements, and thiamine, have been associated with SCD. One or a combination of these risk factors can lead to pathological conditions and cardiovascular diseases (CVDs) that predispose to SCD. The most common physio-pathological event is the rupture of the vulnerable atherosclerotic plaque with athero-thrombosis, observed in the majority of the patients with acute coronary syndromes (ACSs) and SCD. In an animal experiment, it has been reported that neutrophil-depleted animals had worsened cardiac function, increased fibrosis, and progressively developed heart failure, indicating that high neutrophil counts are considered a predictor of adverse clinical outcomes and mortality in patients with ACS. These cells may have a detrimental effect in the acute inflammatory phase after infarction. ACSs in patients with type 2 diabetes double the risk of SCD, and the risk is greater with higher blood glucose. ACS patients with STEMI and NSTEMI have increased risk of SCD, with several gender differences in presentation to emergency care. Recent advances in cardiac imaging techniques as CMR (Cardiac Magnetic Resonance Imaging) can help in the preclinical detection of patients at risk of serious cardiac arrhythmias and SCD. Late gadolinium has been used to identify areas of myocardial fibrosis which is arrhythmogenic in cardiomyopathy, right ventricular dysplasia and some cases of mitral valve prolapsed syndrome as well. Speckle tracking echocardiography is recently used as an important tool in the diagnosis of non STEMI in critical care departments, which can add greatly to the triage of diagnosis of ACS. Finally, tissue Doppler imaging and deformation imaging is crucial for the early detection of patients at risk for SCD in certain patients with hypertrophic cardiomyopathy in the preclinical phase. In order to prevent SCD, it is imperative to impose an aggressive management of cardiovascular risk factors, including performing exercise regularly, educating patients about the dangers of CVDs, promoting a healthy diet, restricting consumption of sugar and salt, advocating moderation in alcohol consumption and smoking cessation to promote a heart healthy behavior to all, young children in particular.