| Summary: | 碩士 === 國立交通大學 === 分子醫學與生物工程研究所 === 102 === Heart rate variability (HRV) is the temporal variation between sequences of consecutive heartbeats. On a standard electrocardiogram (ECG), the duration between two adjacent R wave peaks is termed the R-R interval. The resulting period between adjacent QRS complexes resulting from sinus node depolarization is termed the N-N (normal-normal) interval, and HRV is the measurement of the variability of the N-N intervals. The last two decades have witnessed the recognition of a significant relationship between the autonomic nervous system and cardiovascular mortality, including sudden cardiac death. HRV investigation has its use in the prediction of long-term survival in patients who had suffered from congestive myocardial infarction, or had valvular or congenital heart disease. Depressed HRV is a predictor of mortality and arrhythmic complications independent of other recognized risk factors. HRV assessed from short-term recordings may be used for initial screening of all survivors of an acute myocardial infarction. The purpose is to evaluate the gender and postural effects in HRV parameters between symptomatic MVPS patients and an apparently healthy population.
A total of 118 patients, 7 males and 111 females, who had been echocardiographically diagnosed as having MVPS at Taipei Medical University Hospital cardiology clinic from November 2008 to January 2013, and 148 healthy people (54 males and 94 females) with normal 12-lead ECG without previous history of medical disease from National Chiao-Tung University and residents in Hsinchu were recruited for the study. All subjects had sign an informed consent and agree to take part in the research.
A locally developed Taiwanese machine (DailyCare BioMedical’sReadMyHeart®) was used to record the HRV. One lead ECG (modified lead Ⅱ) was used for signals collection and analysis. The QRS complexes were detected and labelled automatically. The results of the automatic analysis were reviewed subsequently, and any errors in R-wave detection and QRS labelled were then edited manually. The subjects were asked to rest 5 minutes before each HRV recording (Lying, sitting and standing.) All the recordings were taken during the daytime (between 9:00 AM to 4:00 PM) to avoid the diurnal influence of the autonomic difference.
For time-domain HRV measures, the mean N-N intervals and the standard deviation of N-N intervals during 5 minutes (SDNN) were then calculated. For frequency-domain HRV parameters analysis, spectral power was quantified by fast Fourier transformation and autoregressive method for the following frequency bands: 0.15-0.4 Hz (high frequency), 0.04-0.15 Hz (low frequency). Time domain parameters used were SDNN, RMSSD and NN50. Frequency domain parameters selected were TP, LF, HF and LF/HF. These parameters were defined in accordance with the 1996 ACC/AHA/ESC consensus.
To make sure our data is normal distribution, Kolmogorov–Smirnov test was used at first. And then Paired Student t test was used to characterize differences in HRV variables. All HRV variables were expressed as mean ± SD. All statistical analyses were performed using Microsoft Excel 2007. A P value <0.05 was determined as statistically significant.
In Time domain only SDNN between MVPS and Normal was statistically significantly different in all positions, and so as Frequency domain’s Total Power. In Frequency domain all Parameters were shown to have significant differences except in lying position. Between male and female in time domain, there were statistically differences of RMSSD and NN50 at lying both in MVPS and Normal. In frequency domain, all parameters were statistically significantly different in all postures both in MVPS and normal except total power. For postural changes, in normal group that time domain parameters only RMSSD was statistically differences between lying and sitting, but in other postural compared, all parameters were significantly different. And it is the same as in frequency domain parameters, only TP in lying compared with sitting posture had no difference. In MVPS group, the result of time domain parameters and frequency domain were the same as in normal group, except in sitting compared with standing posture. SDNN of time domain, and TP of frequency domain had no significant difference.
From the results, we concluded that the SDNN is compatible with Total Power as demonstrated in the previous reports. Gender specific HRV variation had been reported in our previous study in normal Taiwanese. It is further strengthened the digenetic criteria for HRV should be gender specific in MVPS as well. Moreover, more male MVPS cases should be recruited for further clarification of this issue. Although time domain parameters might not be of use for the evaluation MVPS, frequency domain with postural changes might be a useful tool in MVPS diagnosis risk stratification.
|
|---|
