الفهرس 
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Abstract
Acute coronary syndrome is a high-risk manifestation of coronary artery disease and represents a substantial proportion of all acute hospitalizations. Although mortality because of ACS has declined in recent years due to optimization of timely reperfusion and innovations in pharmacological therapy, ischemic heart disease remains a leading cause of death and accounted for millions of deaths annually. Being able to predict the in-hospital complications of patients with ACS at the time of admission is of great importance when trying to determine treatments. Consequently, many large registries have tried to evaluate possible predictors of in-hospital complications in ACS patients as well as short-term complications that may happen. When we shed some light on some of these predictors, HDL is one of the major elements in the blood in the recent studies. It attracts specific attention because, in contrast to other lipoproteins, as many physiological functions of HDL influence the cardiovascular system in favourable ways unless HDL is modified pathologically. The functions of HDL that have been recently discovered include anti-inflammatory and antioxidant activities which are associated with protection from cardiovascular diseases. HDL is positively associated with decreased risk of CHD, an HDL-C of 50 mg/dL or greater is a negative (protective) risk factor. On the other hand, a high-risk HDL cholesterol level is described as one that is below 40 mg/dL carries worse prognosis in patients of ACS. However, the relationship between the in-hospital outcome and the HDL-C levels of samples drawn after arrival (early HDL-C) remains unclear and poorly studied in addition to its predictive value for prognosis and detecting early cardiovascular events after hospital stay. Our study revealed that low HDL carries worse clinical outcome during hospitalisation. This was evident in the higher incidence of developing acute heart failure, cardiogenic shock, critical coronary lesions and low cardiac function. In addition, patients with low HDL level stay more duration than those of normal to high HDL. In contrast, low HDL cannot predict other major events during hospital stay as arrhythmia, heart block, cardiac arrest and death. Some hypotheses may explain this new concept of a relationship between plasma lipids and cardiovascular events which can be summarized as follows: a rapid decrease in HDL-cholesterol acts as surrogate for necrosis, inflammation or neurohumoral activity and being itself as a direct risk factor for in-hospital events through promoting endothelial dysfunction and myocardial ischemia via inhibiting action of peroxonase. Furthermore, both inflammation and insulin resistance may lead to HDL dysfunction. HDL dysfunction and heart failure may mutually reinforce each other, a pattern of cyclic causality may be present. Moreover, our study showed significant increase in heart failure and frequent episodes of angina among patients of low HDL after being discharged from an attack of ACS within one month. This was supported by observations of MIRACL trial which demonstrated a significant relationship between HDL-C at the time of ACS and 16 week risk of recurrent events, with a 1.4% reduction in risk for each 1 mg/dL increment in baseline HDLC. On the other hand, there was no statistical difference regarding other MACE like stent thrombosis, new cerebrovascular events, cardiogenic shock, recent MI and death. To conclude, our results suggest that, similar to other well-known predictors, a low early HDL-C can predict a poor in-hospital outcome in addition to acting as strong predictor for developing of heart failure and worsening angina at the short term.