| Objective: There are obvious biological rhythms in living organisms.From the molecular biochemistry,the physiological activities of tissues and organs,to the mental behavior of individuals are almost exist periodic fluctuations at different frequencies.Many physiological phenomena(e.g.,heart rate,blood pressure,etc.)and pathological events(myocardial ischemia and infarction,arrhythmia,sudden cardiac death)of the cardiovascular system show typical circadian variation,which is the basic biological characteristics of cardiovascular system.One of the manifestations of heart activity is the electrical activity that occurs before mechanical contraction of the heart.The current of myocardial activation can be transmitted from the heart thro ugh the body tissue to the body surface.The body surface at different positions have different potential.In accordance with the timing of cardiac excitement,the potential recorded from body surface to forms a continuous curve,i.e.ECG.Each cardiac cycle in the ECG can be formed on a corresponding wave group changes.The ECG parameters P wave,QRS wave,T wave duration and amplitude,QTc interval are widely used clinically.Studies found that some indices of ECG,such as QRS wave duration and amplitude,P-R interval,QT interval show circadian rhythms.This study aim to observe whether the commonly used indicators have diurnal variation.By observing the diurnal fluctuation of the 24-hour ambulatory ECG parameters of the healthy subjects,to provide auxiliary diagnosis of the disease and the use of drugs and drug toxicity to determine and adjust the dosage to provide more accurate evidence.Method:1 Subjects: Screening the healthy people receive 24-hour Holter monitoring in the ECG room of Hebei Provincial People’s Hospital during May to October 2017.Patients with significant non-sinus rhythm,bundle branch block,complex heart rhythm,and diagnosed with hypertens ion,organic heart disease,diabetes,electrolyte metabolism disorder were excluded from the study.None of them received any drugs that affect the heart rate,cardiac conduction and autonomic activity,such as β-blockers,calcium antagonists,etc.2 Experimental Methods: Record the subjects’ basic information such as age,height,weight,medical history,physical examination,biochemical tests and echocardiography.Collect ECG data of subjects for 24 hours under general daily activities.Select the ECG data at 6:00,10:00,14:00,18:00,22:00,and 02:00.The manual measurement method was used to measure the data at fixed lead II.The duration and amplitude of P wave,QRS wave and T wave were measured.The PR and QTc intervals were measured.Five consecutive wave forms were selected and measured repeatedly three times.Individual repeated measurements,obtained and recorded on average.3 Statistical Methods: Using SPSS21.0 statistical software for statistical analys is.The measurement data were expressed as mean ± standard deviation(X ± SD),and those in the normal distribution data were analyzed by one-way ANOVA.The results of non-normal distribution of measurement data were expressed as median(interquartile range)M(QR),and Kruskal-Wallis H rank sum tests were used for comparison among groups.P <0.05 for the difference was statistically significant.Results:1.One-way ANOVA analysis showed that there were significant differences among PR intervals at different time points(P <0.05).Among the six time points collected,the PR interval was the shortest at 06:00(0.135 ± 0.028s)in the morning,the longest at 02:00(0.189 ± 0.039s)and at 10:00(0.158 ± 0.034s),14:00(0.161 ± 0.038s),18:00(0.162 ± 0.028s),22:00(0.173 ± 0.036s),PR interval maintained at a relatively long level.The LSD test showed that the PR intervals at 10:00(0.158 ± 0.034s),14:00(0.161 ± 0.038s),18:00(0.162 ± 0.028s)and 22:00(0.173 ± 0.036s)have no significant difference between each two groups.There were significant differences between two groups at 02:00(0.189 ± 0.039s)and 06:00(0.135 ± 0.028s),02:00(0.189 ± 0.039s)and 06:00(0.135 ± 0.028 s)also have s ignificant differences.2.The results of Kruskal-Wallis Test showed that there is no difference in P wave duration(P> 0.05)at different time.3.One-way ANOVA analysis showed that P wave amplitude at different time points had significant difference(P< 0.05).The amplitude of P wave was the lowest at 02:00(0.180 ± 0.045mv),with the highest amplitude at 10:00(0.239 ± 0.078mv),at 14:00(0.206 ± 0.062mv),18:00(0.194 ± 0.062mv),22:00(0.188 ± 0.053mv)amplitude decreased gradually and increased again at 06:00(0.201 ± 0.080mv)in the morning.LSD test results: 10:00(0.239 ± 0.078mv)compared with the remaining five time points had significant differences.There was no significant difference between 02:00(0.180±0.045mv),06:00(0.201 ± 0.080mv),14:00(0.206 ± 0.062mv),18:00(0.194 ± 0.062mv),22:00(0.188 ± 0.053mv).4.The results of Kruskal-Wallis Test showed no significant difference in QRS duration at different time points(P> 0.05).5.One-way ANOVA analysis showed that there was a significant difference in QRS amplitudes between different time points(P <0.01).The amplitude of QRS was the highest at 10:00 AM(1.750 ± 0.662mv).At 14:00(1.408 ± 0.518mv),18:00(1.345 ± 0.522mv)and 22:00(1.352 ± 0.479mv)maintained at a relatively lower level.QRS amplitudes were the lowest at 02:00(1.296 ± 0.462mv).LSD test results : The difference between 02:00(1.296 ± 0.462s)and 06:00(1.667 ± 0.700s)and 10:00(1.750 ± 0.662s)was significant.There was a difference compared 06:00(1.667 ± 0.700s)to 18:00(1.345 ± 0.522s)and 22:00(1.352 ± 0.479s).The difference between 10:00(1.750 ± 0.662s)and 14:00(1.408 ± 0.518s),18:00(1.345 ± 0.522s),22:00(1.352 ± 0.479s)was significant.No difference between the rest of time points.6.One-way ANOVA analysis showed that there were significant differences in T wave duration at different time points(P <0.05).T wave duration was relatively shorter at 06:00(0.217 ± 0.039s),10:00(0.206 ± 0.029s)and 18:00(0.201 ± 0.029s).T wave duration was relatively longer at 14:00(0.220 ± 0.261s),22:00(0.221 ± 0.034s).the longest duration at 02:00(0.229 ± 0.034s).LSD test results: 02:00(0.229 ± 0.034s)compared with 10:00(0.206 ± 0.029s)and 18:00(0.201 ± 0.029s)showed a statistically significant difference.No difference compared between the remaining time points.7.One-way ANOVA showed that the amplitude of T wave has significant difference at different time points(P <0.05).The amplitude was the lowest at 14:00(0.304 ± 0.129s)in the afternoon,and the amplitude increased at 18:00(0.345 ± 0.138s)and 22:00(0.361 ± 0.172s),the maximum amplitude showed at 02:00(0.424 ± 0.200s)but become lower again at 6:00(0.376 ± 0.185s)in the morning and was further lower at 10:00(0.311 ± 0.132s)but still higher than 14:00(0.304 ± 0.129s).The LSD test indicated that there was a significant difference between 02:00(0.424 ± 0.200s)and 10:00(0.311 ± 0.132s)and 14:00(0.304 ± 0.129s).There were no significant differences in comparison of any two time points.8.The results of Kruskal-Wallis Test showed that QTc has no significant difference at different time points(P> 0.05).Conclusion:1.P-R interval,P wave and QRS wave amplitude,T wave duration and amplitude fluctuating day and night.2.P wave time,QRS time limit,QTc interval at different time points remained relatively stable,without significant diurnal changes. |
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