Administration Time-dependent Effects Of Aspirin On Blood Pressure Variability And Morning Blood Pressure Peak Of Non Hypertension Patients With Coronary Heart Disease

Objective:Blood pressure variability and circadian pattern of blood pressure are two characteristics of blood pressure. Blood pressure variability is called blood pressure fluctuation else,which reflects degree of fluctuation in a period. Morning blood pressure peak means blood pressure rise rapidly and significantly. A number of studies have demonstrated that blood pressure variability and morning blood pressure peak can be correlated closely with cardiovascular events. Therefore,the effect of clinical medication on blood pressure and blood pressure variability should be considered . Asprin is important in the primary and secondary prevention ofhypertension and cornory heart disease, particularly because its inhibitory effects on platelet aggregation.Asprin affords anti-platelet aggregation through the acetylation of cyclooxygenase-1 (COX-1) of platelets and asprin irreversibly inhibit cyclooxygenase 1–mediated thromboxane A2(TXA₂)production by platelets.The clinical effectiveness of aspirin on the primary and secondary prevention of cardiovascular events has been well established. Although aspirin is a potent vasoprotective drug, it is generally believed to have no effect on blood pressure.Nowadays, several recent trials suggest that asprin effects not only platelet aggregation,but also blood pressure when asprin was administered at different time.Studies have shown that aspirin may decrease blood pressure when given at bedtime but not when administered on awakening.These results are still under debate.This study investigates the effects of low-dose aspirin on blood pressure variability and morning blood pressure peak of non hypertension patients with coronary heart disease who received aspirin at different times of the day, designed to explore the best time of administration of asprin. Methods:According to Guidelines for diagnosis of hypertension, a total of 8 male patients who were in hospital during November 2010 to March 2011, diagnosed as the coronary heart disease and normotensive were selected, including 1 patient with unstable angina, 7 with acute myocardial infarction. Age from 41 years to 76 years (mean age 55.62±10.88 years). The exclusion criteria were severe renal or hepatic dysfunction, use of nonsteroidal anti-inflammatory drugs, bleeding disorder, PLT is higher than 300×10⁹/L or lower than 100×10⁹/L.The study had a two-stage crossover design, all of the subjects were sent to two groups randomly(A or B), two periods were designed for each group,each period is 1 week. Besides the basic treatment, Subjects of the first group (group A) were assigned to one 1-week period taking 100 mg of aspirin on awakening first, and then one 1-week period taking 100 mg of aspirin at bedtime.Subjects of the second group (group B) were assigned to one 1-week period taking 100 mg of aspirin at bedtime first, and then one 1-week period taking 100 mg of aspirin on awakening. There was a washout period of 1 week between two periods.All subjects underwent 24-hour ambulatory BP monitoring before the first period and after both intervention periods.24-hour ambulatory blood pressure monitoring (ABPM, SpaceLab 90207) was performed when blood pressure was measured. The systolic and diastolic blood pressures were automatically gauged every 20 minutes from 5:00 AM to 10:00 PM and every 60 minutes during the night. There was no restriction of subjects'daily activities, keep the arm with a cuff still when blood pressure was measured. Connect the ABPM to the computer to get the data.Parameters: the mean of systolic and diastolicblood pressure of 24 hours ( SBP24h, DBP24n ), the mean of systolic and diastolic blood pressure of daytime ( 6:00 to 22:00 ) ( SBPd, DBPd ), the mean of systolic and diastolic blood pressure of night (22:00-6:00) (SBPn, DBPn), the mean of systolic and diastolic blood pressure of morning (5:00-10:00)(SBPm,DBPm), standard deviation of SBP24h (SDSBP24h), standard deviation of DBP24h (SDDBP24h), standard deviation of SBPd (SDSBPd), standard deviation of DBPd (SDDBPd), standard deviation of SBPn (SDSBPn), standard deviation of DBPn (SDDBPn), standard deviation of SBPm (SDSBPm) and standard deviation of DBPm (SDDBPm).Statistical Analysis: all of the statistical analyses were performed using SPSS version 13.0 (SPSS Inc).Variables are presented as mean±SD when the test of normality is accepted, or they are presented as median(quartile range). We used general linear model and nonparametric Wilcoxon signed-rank test to deal accurately with the repeated measurements and cross-over design that we had from each participant, the null hypothesis was rejected when 2-tailed P<0.05.Results:â‘ The order of SBP and DBP: the blood pressure of daytime is higher than the blood pressure of 24 hours,the later is higher than the blood pressure of night.â‘¡The order of blood pressure variability (BPV) of SBP and DBP:the BPV of 24 hours is higher than the same parameter of daytime,the later is higher than the BPV of night.The blood pressure variability of systolic is higher than that of diastolic.â‘¢The difference of BP and BPV among different kinds of intervention(before the use of asprin,asprin at bedtime,asiprin upon awakening ) in each group was not significant.â‘£The blood pressure variablity of night is higher when asprin at bedtime than asprin upon awakening in both SBPV and DBPV.Conclusions:Low-dose aspirin at different times has different effects on blood pressure variability,asprin administered at bedtime may rise the blood pressure variability of night.Effect of aspirin on blood pressure variability is dependent on the time of aspirin administration.