| Background:High blood pressure (BP) is the most important risk factor for stroke and other vascular events, accounting for approximately 54% of stroke and 47% of ischemic heart disease worldwide. In recent years, the studies of the relationship of hypertension and carotid atherosclerosis, the relationship between carotid atherosclerosis and stroke, and the relationship between hypertension and stroke had been the focus. The study also found that high blood pressure is closely related to the carotid atherosclerosis, and carotid atherosclerosis is a important cause of stroke. Stroke is divided into ischemic and hemorrhagic cerebral apoplexy, ischemic stroke is the mostcommon type of stroke in our country. Ischemic stroke is defined as the sudden reduction of local brain artery blood perfusion or complete interrupt of blood flow, which causes the destruction of local brain structure and function without the supply of blood and oxygen, sugar, etc., and then a series of nervous system symptoms will happen. Stroke is a high morbidity, high mortality, high morbidity, high rate of relapse of "four high" disease. Stroke is easy to recur, It will increase the illness every time. So stroke causes serious damage to the national health and living standards. A family need to pay a great deal of manpower and material resources because of a stroke patient. In China, the annual stroke mortality rate is approximately 1.6 million, approximately 157 per 100 000, which has exceeded heart disease to become the leading cause of death and adult disability. Stroke causes approximately 116 deaths in population of 100 000 in cities and 111 deaths in rural areas. In addition, China has 2.5 million new stroke cases each year and 7.5 million stroke survivors. China now faces similar cardiovascular and stroke risk factors as in the Western nations:hypertension, diabetes mellitus, hypercholesterolemia, smoking, coronary artery disease, arterial fibrillation, physical inactivity, and obesity. Among them, hypertension remains the most important risk factor for all types of strokes with the highest population-attributable risk at 34.6%.It is noteworthy that, stroke can be prevented and controlled, but most people lack both of the all-round recognition and enough attention about stroke. Therefore, it need to understand the severity of the stroke fully and screen high-risk patients of brain stroke early. It is the top priority to improve the level of the treatment and prevention of stroke and reduce the morbidity, disability rate and mortality of stroke. Despite the challenges and the amount of work the Chinese people are facing in providing better stroke care, the Chinese people have developed a lot of clinical studies to find this leading cause of death and improve stroke care. Healthcare organizations and community-based health education groups also have conducted varied educational activities on stroke prevention, including treating hypertension, stop smoking, healthy eating habits, and so on. Therefore, we urgently need to recognize the severity of the stroke fully, screening high-risk patients with stroke early, raise the level of the treatment and prevention of stroke, and reduce the incidence, morbidity and mortality of stroke.High blood pressure is the most important and independent risk factor of stroke. The main cause of stroke caused by high blood pressure is likely to lead to the changes in the structure and function of the vessel walls of cardiovascular and cerebrovascular. High blood pressure can cause micro-cerebral vessels constriction, If blood pressure rises for a long time, the structure and function of the blood vessel walls because of a lack of oxygen, the smaller arteries become thickened,narrowed and elasticity decreased, which play an important role in forming and aggravating atherosclerosis. And because the contraction and expansion of micro-cerebral vessels can not change with blood pressure fluctuating, when a drop in blood pressure can cause cerebral hypoperfusion and ischemia. On the contrary, cerebral hyperemia, edema and bleeding can caused by cerebral luxury perfusion.Physiologically, BP undergoes continuous fluctuations over time as a result of a complex interaction among cardiovascular control mechanisms. Blood pressure variability (BPV) defined as continuous fluctuations of blood pressure over over a period of time. With the deep research of the hypertension, BPV attracted more and more people’s concern and attention, it has become one of hot topics in the field of hypertension. Blood pressure variability(BPV) is characterized by marked short-term BPV occurring within a 24h period (beat-to-beat, minute-to-minute, hour-to-hour, and day-to-night changes) and also by long-term BPV occurring over more-prolonged periods of time (days, weeks, months, seasons, and even years).Recently, the study have shown that the blood pressure variability has been proved to be playing an important role in the regulate mechanisms of cardiovascular system. In recent years, several scholars also indicate that blood pressure variability is greater than the average blood pressure in the value of the prediction of cardiovascular event, and BPV may be another important index for assessment of the risk in patients with hypertension. People know about the relationship between the level of blood pressure and target organ damage quite well, but the importance of BPV are far from adequate attention.Because of the development and use of 24h ambulatory blood pressure monitoring(ABPM) in the late 1960s, people have a deeper understanding of BPV. Frattola et al. also constitute the first longitudinal evidence that cardiovascular complications of hypertension may depend on the degree of 24h blood pressure variability. Moreover, the hypertension population-based prospective studies have shown that ambulatory blood pressure better predicts than clinic blood pressure measurements the risk of subsequent cardiovascular events. So in the clinical study, the assessment of short-term BPV in the clinical setting is made possible by the growing use of 24h ABPM. From these recordings, it is possible to examine the prognostic of ABPM and its BPV over the hypertensive people.In previous studies, in both longitudinal and cross-sectional studies has clearly shown that useful information may arise from analysis of blood pressure variability (BPV), and variation in blood pressure has also been reported to be associated with cerebrovascular diseases. High blood pressure usually affects blood vessels firstly especially for artery, which is an important leading cause of other target organ damage. One cause link for this association was the development of atherosclerosis. Carotid intima-media thickness (IMT) is a non-invasive indicator of early atherosclerosis, and carotid atherosclerosis is one of the most important independent risk factor for ischemic stroke, which plays an important role in the formation and development of ischemic stroke. And the widely use of B-mode ultrasound offers the opportunity to assess the intima-media thickness (IMT) of carotid artery as a reliable market for the extent of atherosclerosis. Date from previous investigations indicated that the carotid IMT was positively correlated to 24h ABPM blood pressure variability. For example, in the study of Sander et al., they found that the SD of diurnal systolic blood pressure variability as the strongest predictor for IMT. Now scholars at international and domestic have understand the importance of vascular lesions in cerebral apoplexy gradually, and it is important to prevention and treatment of cerebrovascular disease, for preventing stroke prevention in advance.The previous research also showed that both the daytime, and 24 h systolic BPV are positively associated with IMT. Therefore the question that has arisen from the above findings is obviously which pressure has the greater clinical significance and can thus be taken as the best predictor of the patient’s Cardiovascular and cerebrovascular events, which need more studies to find it.This paper will address this issue on the basis of the relationship between BPV and IMT to demonstrate the major impact of circadian blood pressure patterns on the development of early carotid atherosclerosis. In our study, we calculate SD, CV, and ARV of average systolic (SBP), diastolic (DBP), and mean BP values over the 24 h, with the daytime and the nighttime periods separately considered. We designed this study to prospectively analyze the relationship between changes in circadian blood pressure patterns and the progression of early carotid atherosclerosis.Objective:We collect research data using the technology of 24 h ambulatory blood pressure monitoring(ABPM) and carotid ultrasound to statistical analysis. And carotid intima-media thickness(IMT) as a reliable market for the extent of atherosclerosis. The aim is to explore the relationship between short-term blood pressure variability and the carotid intima-media thickness(IMT), in the hope of exploring the impact of the blood pressure variability(BPV) on the occurrence and development of cardiovascular disease, screening for cardiovascular disease in patients at early stage, and predicting cardiovascular disease early.Methods:We conduct a study (134 subjects, aged 23 -79) to evaluate the relationship between blood pressure variability and carotid intima-media thickness in the Second People’s Hospital of Shenzhen, Guangdong Province, China. A thorough history and physical examination should been carried out on all patients. The blood pressure of hypertension was collected using the 24h ambulatory blood pressure monitoring, and its variability was evaluated using standard deviation (SD), coefficient of variation (CV), and average real variability (ARV) during 24h, daytime and nighttime. All the intima-media thickness measurements are collected by ultrasound. And all valid statistical analyses were performed using SPSS statistical package.All subjects are divided into hypertension group and control group (no hypertension group), comparing the general clinical characteristics between the two groups. For hypertension, all subjects are divided into normal IMT group and abnormal IMT group, comparing the general clinical characteristics and blood pressure values between the two groups. The blood pressure variabilities evaluated with SD, CV, and ARV for all hypertension subjects (N=78), analyzing the relationship between the two BPVs respectively. And we analyze the correlation between the blood pressure variability(evaluated with SD,CV,and ARV) and carotid intima-media thickness/number of plaques in all hypertension subjects. We also analyze the correlation between mean blood pressure values and carotidintima-mediathickness/number of plaquesin all hypertension subjects. Finally, multiple regression analysis of left carotid intima-media thickness and blood pressure variabilities is carried out in our study.Results:As the results showed, Both of right and left carotid intima-media thickness (IMT) in the hypertension group was higher than the control group(P<0.05). For the baseline characteristics, the subjects in the hypertension group were significantly older than the subjects in the control group (P<0.05). And BM3 in the hypertension group was higher, which is statistical significance (P<0.05). In the abnormal IMT group, both the number of plaques and carotid IMT were higher than the normal IMT group (P<0.001). And age, smoking rates and 24h PP in the abnormal IMT group were higher, which is statistical significance (P< 0.05). While no significant differences were found in other indicators (P>0.05).We compared the correlations of these BPV values in each group of the two using Pearson’s test.Except the DBPV in nighttime between CV and SD, ARV respectively(P>0.05), no significant differences were found among the three indices of BPV, they had strongly positive correlation (P <0.01). Moreover, we found that all of the SBPV values were greater than those of DBPV when evaluated using SD and ARV. In contrast, the DBPV values were found to be greater than SBPV when using CV as a measure.For all hypertension subjects, there is no significant correlation between the BPVs and RCCA-IMT/number of plaques (P>0.005), whereas, the daytime SBPV,24h SBPV and daytime DBPV showed a positive correlation with LCCA-IMT/number of plaques (P<0.05). In addition, for the mean CCA-IMT/number of plaques, only daytime SBPV were significant(P<0.05). There was no significant correlation between these BP variables and carotid IMT, whereas,24h PP, daytime PP, and nighttime PP were positively associated with the number of plaques. Moreover, a negative correlation was found between the nighttime average DBP and the number of plaques. In addition, the number of plaques in LCCA had higher correlation with PP and DBP than that in RCCA.Multiple regression analysisindicated daytime SBPV-SD was positively associated with LCCA-IMT.Conclusion:The results show that systolic blood pressure variability during daytime and 24h had significant correlation with intima-media thickness, for the hypertensive subjects from the southern area of China. The influence on carotid IMT caused by high blood pressure is partly determined by the BPV. Moreover, we also found the daytime systolic blood pressure variability to be the best predictor for the progression of intima-media thickness in multivariate regression analysis. In addition, the present study suggests that the correlation between blood pressure variability and left carotid common artery-intima-media thickness/number of plaques is stronger than right carotid common artery-intima-media thickness/number of plaques. |
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