Potential Chonobiological Triggering Factors of Acute Heart Attack

摘要

The immediate triggers of acute heart attack or acute coronary syndrome (ACS) are not known exactly. There is a marked increase in sympathetic activity, neuroendocrino- logical dysfunction, oxidative stress and deficiency of ω3 fatty acids, vitamins, minerals, as well as antioxidants during ACS. Energy intake and expenditure have diurnal variation throughout 24- hour cycle and any disturbance in this cycle may result into disruption of the endogenous clock and neurohumoral dysfunctions. Clinical studies have reported an increased incidence of reinfarction, sudden death, coronary constriction, myocardial ischaemia, vascular variability disorders and angina, during second quarter of the 24 hour cycle, at the point where there is rapid withdrawal of vagal activity and increase in sympathetic tone. In several studies, among patients with heart attack, there was a significant 2-3 fold increase in cardiac events in the second quarter of the day (6-12 hours) compared to other quarters respectively. Triggers of heart attack were noted in up to 80.0% of patients in various studies. Brain related and psychological mechanisms, i.e., emotional stress, sleep deprivation, cold climate, hot climate, large meals and physical exertion were observed among 30-50% of patients. Such triggers have also been reported in Europe, North America and Asia. These triggering factors are known to enhance sympathetic activity and decrease vagal tone, resulting into increased secretion of plasma cortisol, noradrenaline, aldosterone, angiotensin converting enzyme, interleukin-1, 2, 6, 18 and tumor necrosis factor-alpha, that are proinflammatory. There is also a deficiency in the serum levels of ω3 fatty acids, vitamin A, E, C, coenzyme Q10, magnesium, potassium, melatonin, interleukin-10 (antiinflammatory) and increase in TBARS, MDA, diene conjugates, TNF-alpha and IL-6, which are indicators of oxidative damage and inflammation, respectively. It is not clear whether the predisposition of ACS is due to size of the meals or other proinflammatory factors of meals.