The intensity of risk factors in young women with ACS
Epidemiological studies have shown that hypertension, hyperlipidemia, smoking and diabetes are the four major risk factors for coronary heart disease [12, 13]。The results of this study showed that the age of young women was (40.77 ± 4.02) years-old in ACS group and (40.57 ± 4.01)years-old in control group, and was no significant difference (P > 0.05) compared between two groups. The subjects in the control group received coronary angiography examination and was proved to be not the coronary artery lesion or to have only mild atherosclerotic plaque, and stenosis with less than 50% of coronary artery lumen diameter. The proportion of combined risk factors in the control group was significantly lower than that in the ACS group (P < 0.05). The risk factors in ACS group was respectively overweight (64.10%), hypertension (49.88%), hyperlipidemia (35.66%), diabetes (23.37%), depression or anxiety disorder (16.62%), gynecological diseases (16.39%), hyperuricemia (15.18%), family history of early onset coronary heart disease (14.94%), hyperhomocysteinemia (11.33%), low thyroid function (14.96%), high cholesterol (8.43%), high CRP (7.47%). Other risk factors account for a smaller proportion (see Table 1). However, except for renal artery stenosis, there were statistically significant differences in the distribution of risk factors compared between groups(P < 0.01)。These results are consistent with those of the Framingham Heart Study〔14༌15〕.The result of Framingham Heart Study showed the relative risk of coronary heart disease in obese women increased by 64%, and was statistically significant differences compared with a 46% increase in men. The regression analysis in this study shows that the relative risk in obese (overweight) women with ACS was more than 400% of those in normal young women without ACS༈P < 0.01༉. The results of this study showed that 64.10% cases with overweight in the ACS group were significantly higher than those (16.63%) in the control group (P < 0.01). Of the 266 overweight (obese) patients in the ACS group, 98.13 percent were overweight with one to four risk factors (P < 0.01). This result showed that the combination of multiple risk factors is one of the main causes of overweight cases with ACS. In addition to the four traditional risk factors of hypertension, hyperlipidemia, smoking and diabetes, the regression analysis results showed that in young women, hyperhomocysteinemia,overweight /obesity, high CRP, hypothyroidism༌gynecological diseases, depression or anxiety, cardiac insufficiency, and oral contraceptives, family history of early onset CHD and autoimmune diseases are independent risk factors. This is the main characteristic of risk factors in young women with ACS[16]. In the ACS group, the distribution proportion of these risk factors was significantly higher than that in the control group (P < 0.01). Among the ACS patients in this study, 54.70% cases were combination with 2 to 3 risk factors, and 86.03% were combination with 1 to 4 risk factors. There were statistically significant differences in the number of combined risk factors compared between the two groups (P < 0.01). This result indicates that the co-existence of multiple risk factors is the main cause for the occurrence of ACS in young women. It has been reported that gynecological diseases combined with cardiovascular disease (such as hypertension) and diabetes increase the risk of ischemic heart disease by two times[17].The patients who smoke and also take oral contraceptives have a seven-fold increased risk of developing arteriosclerotic cardiovascular disease [18]。The results of this study also showed that the smoking rate of ACS patients was significantly higher than that of the control group (P < 0.05). Hyperuricemia is an independent risk factor in women with CHD, but not in men [19]。Estrogen has a protective effect on the heart [20, 21]. After menopause, estrogen secretion gradually decreases in women, which cause metabolic disorders and lead to increased blood lipids and increased blood viscosity, thus leading to atherosclerosis and significantly increasing the incidence of coronary heart disease [22]. So menopause is a unique risk factor for coronary heart disease in women [23]。
The role of lipids, creatinine, uric acid, homocysteine and inflammatory reactions on the pathogenesis of ACS
The results of this study showed that the serum levels of LDL, TG, creatinine(Crea), CRP and Hcy in the ACS group were significantly higher than those in the control group (P < 0.01).This showed that these factors are involved in the occurrence and development of ACS in young women [24]. The proportion of hyperlipidemia(40.72%) in ACS group was significantly higher than that (3.13%) in control group (P < 0.01). Hyperuricemia (14.94%) in ACS group was significantly higher than that (6.51%) in control group (P < 0.01). The HDL/LDL ratio (0.53 ± 0.19) in the control group was significantly higher than that (0.46 ± 0.18) in the ACS group (P < 0.01). The TC/HDL ratio (4.19 ± 1.52) in the ACS group was significantly higher than that (3.58 ± 0.93) in the control group (P < 0.01). This indicates that lipids and uric acid are involved in the pathogenesis of ACS in young women[25, 26]. Hcy has been proven to be risk factor for coronary heart disease. Hcy level (10.30 ± 6.04umol/L) in ACS group was significantly higher than that (8.46 ± 2.45umol/L) in control group, with a statistically significant difference (P < 0.01) compared between two groups. This indicates that Hcy is also a risk factor suffering from ACS in young women.
The relationship between CRP and ACS is complex. CRP promotes the formation of unstable plaques of coronary atherosclerosis and triggers the rupture of vulnerable plaques, cause thrombosis in coronary arteries and lead to the occurrence of ACS and acute myocardial infarction (AMI). CRP can reduce the stability of nitric oxide synthase mRNA in endothelial cells, which leads to the decrease of the expression of nitric oxide synthase protein and to inhibits endothelial cells to produce nitric oxide. Nitric oxide has a role of maintaining the elasticity of blood vessel, and dilating the blood vessels, being against vasoconstriction caused by endothelin and angiotensin Ⅱ, and promoting the formation of blood vessels. CRP may also increase the expression of endothelial cell adhesion molecules and enzymatically bind to modified low-density lipoprotein which promote monocyte aggregation into the atheromatous plaque to cause plaque instability. AMI necrosis substance stimulates the production of CRP. Therefore, the increase of CRP is proportional to the number of myocardial cells necrosis. CRP rises to the peak value in 2 days after the onset of AMI, and then drops gradually. This suggests that there is a causal relationship between CRP and the onset of ACS, and that CRP is an important risk factor for the onset of ACS in young women. This study showed that the average CRP (3.40 ± 5.98 mg/L) in ACS group was significantly higher than that(1.24 ± 1.46 mg/L)in control group༈P < 0.01. A bivariate correlation analysis of CRP level and age yielded a Pearson Correlation of -0.129 and a P value of 0.000 as the double-tail test. This showed that CRP level is negatively correlated with age, that is, the younger female is the higher CRP level, indicating the role of CRP on the occurrence and development of ACS in young female. Previous studies have shown that high sensitivity C-reactive protein (hs-CRP) elevation can predict future adverse cardiac events [27]. Anti-inflammatory drugs, such as colchicine, methotrexate and IL-1β inhibitor canakinumab can reduce the inflammatory response and significantly reduce the risk of cardiovascular events. This result confirms that inflammatory response is involved in the occurrence and development of ACS.