
==== Front
Heliyon
Heliyon
Heliyon
2405-8440
Elsevier

S2405-8440(24)12816-2
10.1016/j.heliyon.2024.e36785
e36785
Research Article
Pulse signal may be a key bridge connecting cardiology and pulse diagnosis of TCM
Tang Qingfeng tqf1013@aqnu.edu.cn
ab
Chen Yan-kun chen.yankun@stu.hnucm.edu.cn
c
Liu Shiping lsp123456789lsp@qq.com
a
Wang Jue wj11197@163.com
db
Zhang Liangliang 18237145173@163.com
a
Qu Haoyu quhaoyu@hnucm.edu.cn
e⁎
An Hui anvui@126.com
f⁎
a Digital and Intelligent Health Research Center, Anqing Normal University, Anqing 246133, China
b School of Traditional Chinese Medicine, Shanghai University of Traditional Chinese Medicine, Shanghai 201203, China
c Precision Medicine R&D Center, Zhuhai Institute of Advanced Technology, Chinese Academy of Sciences, Zhuhai 519000, China
d RainbowFish Rehabilitation & Nursing School, Hangzhou Vocational & Technical College, Hangzhou 310018, China
e School of Informatics, Hunan University of Chinese Medicine, Changsha 410036, China
f Health Management & Physical Examination Center, Xiangyang Central Hospital, Affiliated Hospital of Hubei University of Arts and Science, Xiangyang 441021, China
⁎ Corresponding authors. quhaoyu@hnucm.edu.cnanvui@126.com
28 8 2024
15 9 2024
28 8 2024
10 17 e3678515 2 2024
10 8 2024
22 8 2024
© 2024 The Author(s)
2024
https://creativecommons.org/licenses/by-nc/4.0/ This is an open access article under the CC BY-NC license (http://creativecommons.org/licenses/by-nc/4.0/).
Objective

This study extracts atherosclerosis indices from six channels of Cunkou and discusses the data distribution, aims to explore the connection between cardiology of modern medicine (MM) and traditional Chinese medicine (TCM) pulse diagnosis.

Methods

We use a device capable of simultaneously collecting the pulse signals of the Cun, Guan and Chi to test the population participating in routine physical examinations. Firstly, we collected pressure pulse waves from six channels of Cunkou of 1045 healthy subjects (578 men and 467 women, average age=37.99±16.02 years). Secondly, we extracted the two most common arteriosclerosis indices pulse transit time (PTT) and Augmentation index (AIx) from six-channel pulse waves. Lastly, T-test and correlation test were taken to analyze the differences and relevance of the atherosclerosis indices extracted from six channels of Cunkou.

Results

When analyzing AIx and PTT at different wrist, it was found that AIx of left wrist is significantly higher than that of right wrist (P<0.001), while the PTT of left wrist is significantly lower than that of right wrist (P<0.001), a phenomenon that is common in both men and women. Furthermore, regardless of whether it is left or right wrist, the AIx at Chi channel is higher than that at Cun (P<0.05) and Guan (P<0.05). At the same time, the PTT at Guan is bigger than that at Cun in two wrists (P<0.05). However, when the specific channel is not considered, there is no significant difference in AIx and PTT between each channel and the corresponding wrist (P>0.05). In addition, regardless of gender, when the specific channel is not considered, AIx and PTT of each wrist are significantly correlated with age (P<0.001).

Conclusions

The differences of the atherosclerosis indices AIx and PTT in six channels support that the method of six-channel pulse diagnosis is indispensable in TCM. Additionally, the pulse waves obtained from each channel can be utilized as a dependable foundation for diagnosing atherosclerotic conditions. This study is beneficial for promoting the integration of TCM and MM in diagnosing disease.

Keywords

Atherosclerosis index
Augmentation index
Cardiology
Data distribution
Pulse transit time
Six-channel pulse diagnosis
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pmc1 Introduction

Cardiovascular disease (CVD) is the commonest diseases to threaten people's physical and mental health, and atherosclerosis is an important risk factor for CVD [1]. It is significant to assess atherosclerosis for the prevention of CVD. Meanwhile, it is a usual way to evaluate atherosclerosis by testing the shape characteristics of pulse signal [2]. Ferreira et al. discoursed that pulse signal analysis is a bridge between traditional Chinese medicine (TCM) pulse diagnosis and cardiology [3]. In fact, the researchers of different medical backgrounds all over the world have carried out a lot of contributions in this field. Assessing atherosclerosis by the feature parameters of pulse signals of radial artery is one of the most important research hotspots in modern medicine (MM). The pulse data from one stronger beating point of radial artery is usually collected [4].

Pulse transit time (PTT) and Augmentation index (AIx) are the most common atherosclerosis indices of pulse signal. Normally, one single cycle pulse data of healthy people includes three special peaks, sequentially referred to as Percussion Wave (PW), Tidal Wave (TW) and Dicrotic Wave (DW). AIx is equal to the ratio of TW value to PW value (AIx= P2/P1), and PTT is represented by the time difference of PW and TW (PTT=T2-T1), as given in Fig. 1(a, b). TW is formed as the result of the reflection of blood flow. The progression of arteriosclerosis with increasing age leads to an acceleration in blood flow velocity. This, in turn, results in a higher energy of the TW, indicated by an increase in AIx, and an earlier occurrence of the TW, indicated by a decrease in PTT [5]. AIx was proposed as an important index to access vascular stiffness [6]. The previous studies have shown that AIx is positively age-related. Moreover, AIx is a potential marker to CVD, Choi pointed out that AIx is closely related to Framingham risk score [7]. PTT was obtained to evaluate arteriosclerosis by one single pulse wave [5]. The study proposed by Tang et al. showed PTT was closely related to age [8].Figure 1 Extracting AIx and PTT from the pulse signal. AIx= P2/P1, PTT=T2-T1. The data shown in panel (a) is for a 23 years old woman, and panel (b) is for a 59 years old woman. An increase in age indicates an increase in AIx, while a decrease in PTT.

Figure 1

Moreover, the analysis for pulse signal is an important part of quantitative research on pulse condition of TCM. The distribution differences of characteristic parameters extracted from pulse signal of the patients with arteriosclerosis were studied. Chen believed that the radial pulse wave of the subjects with different degree of arteriosclerosis is also different [9]. Liu found that partial features of pulse diagnosis information between Qi deficiency constitution and Yang deficiency constitution are significantly difference in northwest China [10]. Xu pointed out that the partial pulse parameters of hypertensive patients were significantly different from the normal control group [11]. Besides, many researches shown that the pulse waves at Cun, Guan and Chi are different [12], [13].

However, six channels of Cunkou respectively correspond to Zangfu is an important theory of TCM diagnosis, which is disputed in MM:

(i)Taking the pulse atCunkoualone has become a unique diagnostic method of pulse diagnosis in TCM[14]. TCM diagnosis has a history of nearly two thousand years. Cunkou represents radial artery at two wrists, which consists of Cun, Guan and Chi, as shown in Fig. 2. There are six channels in two wrists, six-channel pulse diagnosis is the important method of pulse diagnosis in TCM. The quantitative study on pulse condition of Cunkou is an essential part of modern research in TCM, it is also one of the main research directions to evaluate arteriosclerosis by analyzing the pulse signal of six channels [15].Figure 2 The diagram for collecting pressure pulse signal of six channels at Cunkou. There are three pulse-taking channels of Cun, Guan and Chi in each wrist.

Figure 2

(ii) MM hardly pays attention to the location of pulse detection inCunkou. Cun, Guan, Chi has not been widely accepted in MM. MM mainly focuses on the point of Cunkou with strong pulse beats [4], [8]. Therefore, it is a hot and difficult research topic in medical field to combine the research viewpoints of MM with TCM [16].

This study aims to contribute the integration between the research perspectives of cardiology in MM and the necessity of six-channel pulse diagnosis in TCM:

• In response to the difficulty in identifying TW of the pulse wave, we propose fourth-order derivative to estimate the location of TW, and further extract the two most common parameters (AIx and PTT) for evaluating arteriosclerosis.

• We analyze the differences of arteriosclerosis indices acquired from six channels of Cunkou to support the necessity of six-channel pulse diagnosis in TCM.

• We analyze the correlation of arteriosclerosis indices between two wrists, as well as the correlation between arteriosclerosis indices and age, to verify the conclusions of MM, without considering Cun, Guan and Chi.

2 Methods

2.1 Study design

TCM believes that the pulse beat at six channels of Cunkou represents the health status of different Zangfu of the body, but the different channels of Cun, Guan and Chi are not distinguished in MM. In order to explore the connection between TCM and MM, we designed the research framework, as given in Fig. 3.Figure 3 The flowchart for the methodology of this work. This study analyzes the correlation of atherosclerosis indicators extracted from the pulse signals of the six channels and explores the connection between cardiology of MM and TCM pulse diagnosis.

Figure 3

This work supports the necessity of the six-channels pulse diagnosis, a cornerstone of TCM, by conducting a comparative analysis of atherosclerosis indices across various channels and between the wrists. Furthermore, eschewing Cun, Guan and Chi of TCM, this work endeavors to elucidate the relevance between atherosclerosis indicators and age, as well as to assess the correlation of these parameters between two wrists. This comprehensive approach aims to corroborate the findings of MM research pertaining to atherosclerosis.

2.2 Subjects

We recruited 1045 healthy subjects (578 men and 467 women) who participated in health examination at Hunan Academy of Traditional Chinese Medicine Affiliated Hospital, The Fourth Hospital of Changsha and The First Hospital of Hunan University of Chinese Medicine. The characteristics of subjects were given in Table 1.Table 1 Basic characteristic of the subjects.

Table 1	Male (n=578)	Female (n=467)	P value	
Age (years)	40.33±15.73	35.09±14.72	P<0.001	
Height (cm)	168.12±7.06	158.19±5.45	P<0.001	
Weight (kg)	66.75±11.31	54.59±8.54	P<0.001	
BMI (kg/m2)	23.60±3.56	21.83±3.36	P<0.001	
SBP (mmHg)	120.54±12.64	113.91±14.33	P<0.001	
DBP (mmHg)	75.28±9.41	71.04±9.93	P<0.001	
PP (mmHg)	45.26±10.14	42.87±10.59	P<0.001	
HR (beats/min)	75.92±12.45	77.92±12.64	P<0.05	
BMI: body mass index; DBP: diastolic blood pressure; HR: heart rate; PP: pulse pressure; SBP: systolic blood pressure. All values are given as mean ± std. The differences of 8 characteristics were significance (P<0.05).

We included the subjects who passed the health examination, it mainly included heart rate, blood pressure and body temperature. We excluded the subjects who had a history of CVD, and the subjects with a history of dependence on drugs or alcohol were also excluded.

Data collection was mainly accomplished by the medical students, who had at least three years of experience. The process was supervised by the management department of the three hospitals.

2.3 Equipment and measurements

The pulse data acquisition equipment (Patent number: 200810225717.0) [17] was developed by China Academy of Chinese Medicine Sciences (CACMS), which adopted pressure sensors. The device can simultaneously collect pulse data from three channels of single wrist at 1000 Hz sampling frequency. Moreover, the device automatically converts the units of data collected by sensors into gram-force and saves the data on the local disk.

All participants had a rest at least 3 minutes before testing, and then pulse data of six channels was collected successively. Each time recorded approximately 30 s. During the testing, the subjects are instructed to sit upright while keeping their arms relaxed, ensuring that the heart and the position of data collection are essentially at the same horizontal level. Meanwhile, the device can adjust the contact pressure on the skin to obtain clear pulse data. Maijing records “Marked by the styloid process of radius, the inner side of the styloid process is Guan, the front of Guan is Cun, and the back of Guan is Chi”. The details were shown in Fig. 4(a, b).Figure 4 The channels of Cun, Guan and Chi when collecting pulse data. Panel (a) illustrates the collection channels, and panel (b) shows the posture of the subject.

Figure 4

2.4 Extracting AIx and PTT

There is great difference in pulse signals among different people. In many cases, The TW is extremely faint and the location of the TW is not obvious. In view of this, the fourth derivative was used to recognize the location of TW [18], as shown in Fig. 5(a, b). Before extracting AIx and PTT, baseline correction is essential. The baseline is obtained by fitting the start and end points of the pulse signal with a linear model. The previous works had proposed that it is an effective approach [4], [5], [8]. AIx and PTT of all pulse data were extracted by this method in this work.Figure 5 In both panel (a) and panel (b), fourth derivative can effectively identify the position of TW. AIx is equal to the ration of P2 to P1, and PTT is expressed by the time difference of the PW and TW. The unit for the vertical axis is gram-force, and the unit of the horizontal axis is the sampling time point at a sampling frequency of 1000 Hz.

Figure 5

2.5 Verifying the potential necessity of six-channel pulse diagnose in TCM

In TCM, Zangfu actually includes heart, lung, liver, spleen, kidney and life gate. Six channels of Cunkou represent different Zangfu, and reflect the health status of different Zangfu. In details, Left-Cun, Right-Cun, Left-Guan, Right-Guan, Left-Chi and Right-Chi represent heart, lung, liver, spleen, kidney and life gate respectively. The TCM doctors diagnose disease by touching the pulse of six channels.

The pulse diagnosis based on six channels is an essential component of TCM pulse diagnosis. This work focuses on the necessity of this pulse diagnosis method. Thus, we demonstrate the potential value of six-channel pulse diagnosis by analyzing the differences in key parameters extracted from the pulse signals of six channels. Therefore, we should verify whether there is difference in the parameters of pulse data at six channels of Cunkou. This work not only analyzes the differences in different wrists, but also analyzes the differences between the three channels of Cun, Guan and Chi.

2.6 Verifying the research conclusions in MM

In MM, six-channel pulse diagnose has not been widely accepted. We want to verify whether the pulse wave of any channel can be used as the basis for evaluating atherosclerosis. So we analyze the difference of the parameters between each channel and the corresponding wrist. We also should analyze the data distribution of the atherosclerosis indices without considering three channels. In this study, we verify whether the atherosclerosis indices are age-related and analyze the correlation of atherosclerosis indices between left and right wrist.

2.7 Statistical methods

The values in this manuscript were expressed as mean±std. The difference of basic characteristic parameters between male and female were analyzed by variance analysis (ANOVA). The difference of two wrists was evaluated by paired sample T-test (PSTT). The difference of AIx and PTT among different channels was also evaluated based on PSTT. The difference of AIx and PTT between each channel and the corresponding wrist was calculated by independent sample T-test (ISTT). The relevance of age with AIx and PTT was calculated by unary linear regression (ULR). The relevance between left and right wrist was also calculated by ULR. P<0.05 was considered to indicate statistical significance. All data works were processed in MATLAB.

3 Results

3.1 AIx and PTT in different wrists

The differences of two arteriosclerosis indices between left and right wrist were compared in Table 2. In this part, the value of each wrist is the average value of the corresponding three channels of Cun, Guan and Chi. AIx was bigger in left wrist than right wrist both in men and women (P<0.001). Moreover, PTT was smaller in left wrist than right wrist both in men and women (P<0.001).Table 2 The difference of two parameters between left and right wrist.

Table 2	Alx	PTT	
Left wrist	Right wrist	P value	Left wrist	Right wrist	P value	
Male (n=578)	0.669±0.196	0.648±0.201	P<0.001	0.128±0.012	0.130±0.013	P<0.001	
Female (n=467)	0.702±0.184	0.681±0.192	P<0.001	0.131±0.014	0.133±0.015	P<0.001	
AIx: Augmentation index; PTT: pulse transit time. The values are given as mean±std. Paired sample T-test was used to analyze the differences of AIx and PTT between two wrists in male and female.

3.2 AIx and PTT at six channels of Cunkou

The differences of AIx at six channels of Cunkou we show in Fig. 6. The AIx of men and women are calculated together. AIx was bigger in left wrist than right wrist (P<0.05). In details, AIx at Chi was bigger than that of Cun (P<0.05), and AIx at Chi was bigger than that of Guan both in two wrists (P<0.05). The difference between Cun and Guan was not statistically significant both in two wrists (P>0.05).Figure 6 The significance of difference of AIx at six channels of Cunkou, ′*′ represents P<0.05 based on paired sample T-test.

Figure 6

Furthermore, we also analyzed the difference of AIx between each channel and the corresponding wrist, the results are given in Fig. 7(a-f). There were insignificant difference (P>0.05) in AIx between each channel and the corresponding wrist.Figure 7 The difference of AIx between each channel and the corresponding wrist. In panel (a), (b) and (c), the differences of AIx in Left-Cun, Left-Guan, Left-Chi, and left wrist are compared, respectively. In panel (d), (e) and (f), the differences of AIx in Right-Cun, Right-Guan, Right-Chi, and right wrist are compared, respectively.

Figure 7

Fig. 8 illustrated the differences of PTT at six channels of Cunkou. The PTT data of men and women are calculated together. In details, PTT of right wrist was bigger than that of left wrist (P<0.05). Moreover, PTT at Chi was bigger than that at Cun in right wrist (P<0.05), and it was not statistically significant in left wrist (P>0.05). In additional, PTT at Guan was bigger than that at Cun both in left and right wrists (P<0.05), and the difference between Guan and Chi was not statistically significant both in left and right wrists (P>0.05). Moreover, difference of PTT between each channel and the corresponding wrist were given in Fig. 9(a-f). The results showed that the difference of PTT between each channel and the corresponding wrist was not statistically significant (P>0.05)Figure 8 The significance of difference of PTT at six channels of Cunkou, ′*′ represents P<0.05 based on paired sample T-test.

Figure 8

Figure 9 The difference of PTT between each channel and the corresponding wrist. In panel (a), (b) and (c), the differences of PTT in Left-Cun, Left-Guan, Left-Chi, and left wrist are compared, respectively. In panel (d), (e) and (f), the differences of PTT in Right-Cun, Right-Guan, Right-Chi, and right wrist are compared, respectively.

Figure 9

3.3 The relevance of AIx and PTT between left and right wrist

Fig. 10(a, b) illustrated the relevance of AIx between two wrists in different genders. The value of each wrist is the average value of the corresponding three channels. There was a statistically significant correlation between right and left wrist both in men and women (P<0.001). The correlation coefficients were both larger than 0.95.Figure 10 Panel (a) shows the relevance of AIx between right and left wrist in man. Panel (b) gives the relevance of AIx between right and left wrist in woman.

Figure 10

The relevance of PTT between right and left wrist in different genders was given in Fig. 11(a, b). The value of each wrist is the average value of the corresponding three channels. There was also a statistically significant correlation between right and left wrist both in men and women (P<0.001), and the correlation coefficients were as high as 0.90 and 0.88, respectively.Figure 11 Panel (a) shows the relevance of PTT between right and left wrist in man. Panel (b) gives the relevance of PTT between right and left wrist in woman.

Figure 11

3.4 The relevance of age with AIx and PTT

The relevance between age and AIx was given in Table 3. AIx of left wrist and AIx of right wrist were statistically significant to age (P<0.001) both in men and women without considering three channels, the value of each wrist was not the average value of the corresponding three channels. Moreover, AIx was positively age-related (P<0.001) in each channel.Table 3 The relevance between age and AIx at different channels and different wrist.

Table 3Sex	Wrist	P value	r	Channel	P value	r	
Male				Cun (n=578)	P<0.001	0.472	
Left wrist (n=578×3)	P<0.001	0.473	Guan (n=578)	P<0.001	0.486	
			Chi (n=578)	P<0.001	0.464	
			Cun (n=578)	P<0.001	0.506	
Right wrist (n=578×3)	P<0.001	0.520	Guan (n=578)	P<0.001	0.531	
			Chi (n=578)	P<0.001	0.527	


	
Female				Cun (n=467)	P<0.001	0.557	
Left wrist (n=467×3)	P<0.001	0.562	Guan (n=467)	P<0.001	0.590	
			Chi (n=467)	P<0.001	0.541	
			Cun (n=467)	P<0.001	0.624	
Right wrist (n=467×3)	P<0.001	0.614	Guan (n=467)	P<0.001	0.633	
			Chi (n=467)	P<0.001	0.586	
The results of the linear regression show that AIx at each location is significantly correlated with age. r and P value represent the results of the correlation coefficient and the linear correlation test, respectively. Additionally, when not distinguishing between the different pulse channels (Cun, Guan and Chi), AIx at each wrist is also significantly correlated with age.

Table 4 showed the relevance between age and PTT. PTT of left wrist and PTT of right wrist were statistically significant to age (P<0.05) both in men and women in the condition of neglecting three channels, the value of each wrist was not the average value of the corresponding three channels. There was a statistically negative correlation (P<0.05) between PTT and age in each channel.Table 4 The relevance between age and PTT at different channels and different wrists.

Table 4Sex	Wrist	P value	r	Channel	P value	r	
Male				Cun (n=578)	P<0.05	-0.106	
Left wrist (n=578×3)	P<0.001	-0.125	Guan (n=578)	P<0.005	-0.124	
			Chi (n=578)	P<0.001	-0.144	
			Cun (n=578)	P<0.005	-0.126	
Right wrist (n=578×3)	P<0.001	-0.126	Guan (n=578)	P<0.005	-0.118	
			Chi (n=578)	P<0.001	-0.134	


	
Female				Cun (n=467)	P<0.001	-0.171	
Left wrist (n=467×3)	P<0.001	-0.197	Guan (n=467)	P<0.001	-0.179	
			Chi (n=467)	P<0.001	-0.240	
			Cun (n=467)	P<0.001	-0.162	
Right wrist (n=467×3)	P<0.001	-0.200	Guan (n=467)	P<0.001	-0.214	
			Chi (n=467)	P<0.001	-0.223	
The results of the linear regression show that PTT at each location is significantly correlated with age. r and P value represent the results of the correlation coefficient and the linear correlation test, respectively. Additionally, when not distinguishing between the different pulse channels (Cun, Guan and Chi), PTT at each wrist is also significantly correlated with age.

4 Discussion

The research on pulse signal is not only a hot spot in MM, but also an important part of quantitative analysis for pulse diagnosis in TCM [7]. However, the viewpoint of six-channel pulse diagnosis in TCM has not been widely accepted in MM. Few studies simultaneously focus on the differences and connections between pulse diagnosis theory of TCM and cardiology of MM. Therefore, it is greatly significant to integrate TCM with MM by analyzing the difference and regularity of the pulse signals at six channels of Cunkou. Indeed, the researchers have pointed out that the analysis for pulse signal is a bridge between cardiology of MM and pulse diagnosis of TCM [3]. This study extracted AIx and PTT from pressure pulse waves of six channels at Cunkou and analyzed the distribution characteristics of the atherosclerosis indices. We found that the research conclusions of pulse diagnosis in TCM and MM are both interpretable.

4.1 The differences of left and right distinguish Yin and Yang in TCM

Syndromedifferentiation is the basic principle to recognize diseases in TCM. In fact, the differences between right and left hand have been also recorded in the ancient books of TCM. Neijing believes that left and right hands can be used to distinguish Yin and Yang, the left pulse is Yang pulse and the right pulse is Yin pulse [19]. Yang and Yin are not specific but relative in TCM, and they are used to describe the difference. The results of this study show that AIx and PTT are different between left and right wrist, given in Table 2. In both men and women, AIx of right wrist is smaller than that of left wrist (P<0.001), and PTT of right wrist is bigger than that of left wrist (P<0.001). It illustrates that the vascular elasticity of right hand is better than left hand. Some researchers believe that frequent use of right hand is one of the main reasons for better vascular elasticity of right hand [20].

4.2 The differences of Cun, Guan and Chi support six-channel pulse diagnosis in TCM

Meanwhile, Six-channel pulsed diagnosis is an important method of pulse diagnosis in TCM. The contents recorded in Neijing indicate that the six channels of Cunkou can reflect the health status of different Zangfu [21]. In clinical practice, the doctors of TCM need to carefully check the pulse condition of six channels, then compare the pulse condition of six channels and diagnose on diseases [22]. This study shows that there are slight differences in the two arteriosclerosis indices of six channels. Specifically speaking, AIx at Chi is bigger than that of Cun (P<0.05) and Guan (P<0.05), the difference of left wrist is identical to the right wrist (Fig. 6). Besides, PTT at Chi is bigger than that at Cun, it is statistically significant in right wrist (P<0.05) but not statistically significant in left wrist (P>0.05). PTT at Guan is bigger than that of Cun, which is statistically significant in both wrists (P<0.05) (Fig. 8). Different channels of Cun, Guan and Chi at two wrists represent heart, liver, kidney, lung, spleen and life gate [23]. The ancient book of TCM Suwen records “The pulse of liver is Xian, the pulse of heart is Gou, the pulse of spleen is Dai, the pulse of lung is Mao, and the pulse of kidney is Shi”. The differences of arteriosclerosis indices at six channels of Cunkou verify the necessity of six-channel pulse diagnosis in TCM. TCM believes that the differences at six channels of Cunkou are judged by a combination of various factors. AIx and PTT are components of these factors. This study explores the way to verify the differences of six channels by analyzing the distribution characteristics of AIx and PTT.

4.3 High correlations between two wrists indicate the effectiveness of any side

Moreover, the researchers of MM not only use the pulse wave from radial artery (Cunkou) but also the pulse wave from carotid artery to access atherosclerosis. Sugawara proposed that AIx obtained from carotid and radial artery is very similar, and they are both effective parameters for evaluating vascular function [24]. In this work, the correlation between the left and right wrist is extremely strong (P<0.001, r>0.88) whether AIx or PTT, shown in Fig. 10(a, b) and Fig. 11(a, b). The results in this work show that the two atherosclerosis indices of two wrists are consistent, which is a further perfection to the research viewpoint of Sugawara.

4.4 Any channel of Cun, Guan and Chi can serve as an effective basis for evaluating arteriosclerosis

In the other hand, six channels of Cunkou are not considered in MM and the pulse data from one stronger beating point of radial artery (Cunkou) is usually collected. In this study, Fig. 7(a-f) and Fig. 9(a-f) analyzed the difference of AIx and PTT between each channel and the corresponding wrist, and the difference is not statistically significant (P>0.05). In addition, we discussed the relevance between age and the two atherosclerosis indices of each channel, we found that each relevance is statistically significant (P<0.05). Moreover, we also analyze the correlation between age and the two atherosclerosis indices of each wrist without considering six-channel. The results are given in Table 3 and Table 4, AIx of either wrist is positively correlated with age (P<0.001) and the PTT of either wrist is negatively correlated with age (P<0.001). The findings are consistent with the conclusions research on AIx and PTT in MM [5], [7].

4.5 Limitations and future works

However, this study also has limitations. Three channels (Cun, Guan, Chi) and three depths (Fu, Zhong, Chen) called Three Channels and Nine Indicators (TPNI), which plays an irreplaceable role in TCM pulse diagnosis. Furthermore, this study did not focus on the impact of epidemiological characteristics such as age categories, active or sedentary on the results. Thus, these potential influence factors will be considered in our future works.

5 Conclusions

This study aimed to build the bridge between cardiology of MM and TCM pulse diagnosis by analyzing the data distribution of AIx and PTT extracted from pressure pulse wave of six channels at Cunkou. The results suggest the necessity of six-channel pulse diagnosis in TCM. Besides, In MM, pulse signals from any channel can serve as an effective basis for evaluating arteriosclerosis without considering Cun, Guan and Chi. This study further expands the horizons for integrating the theories of TCM and MM in the diagnosis and treatment of diseases.

Ethics statement

A signed informed consent form was provided for each subject before testing. This study was approved by the ethics committee of Xiangyang Central Hospital under the registration number 2023-070, and complied with the principles of the Declaration of Helsinki and was approved by the Ethics Committee of our institution.

CRediT authorship contribution statement

Qingfeng Tang: Writing – review & editing, Writing – original draft, Funding acquisition. Yan-kun Chen: Methodology, Data curation. Shiping Liu: Writing – original draft, Software. Jue Wang: Methodology. Liangliang Zhang: Funding acquisition, Formal analysis. Haoyu Qu: Supervision, Resources, Funding acquisition. Hui An: Supervision, Methodology.

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Data availability

The data associated with this study are not deposited into a publicly available repository, but the data will be made available from H.Y. Qu on reasonable request.

Acknowledgements

This work was supported by 10.13039/501100001809 National Nature Science Foundation of China (No. 62302014 ), 10.13039/501100003995 Anhui Provincial Natural Science Foundation (No. 2108085QF269 ), the Key Project of Science Research in Universities of Anhui Province of China (2023AH050497 , 2023AH050492 ), and Hunan Provincial Key R & D Plan (No. 2022SK2018 ).
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References

1 Tsao C.W. Aday A.W. Almarzooq Z.I. Anderson C.A. Arora P. Avery C.L. Baker-Smith C.M. Beaton A.Z. Boehme A.K. Buxton A.E. Commodore-Mensah Y. Elkind M.S. Evenson K.R. Eze-Nliam C. Fugar S. Generoso G. Heard D.G. Hiremath S. Ho J.E. Kalani R. Kazi D.S. Ko D. Levine D.A. Liu J. Ma J. Magnani J.W. Michos E.D. Mussolino M.E. Navaneethan S.D. Parikh N.I. Poudel R. Rezk-Hanna M. Roth G.A. Shah N.S. St-Onge M.-P. Thacker E.L. Virani S.S. Voeks J.H. Wang N.-Y. Wong N.D. Wong S.S. Yaffe K. Martin S.S. Heart disease and stroke statistics—2023 update: a report from the American heart association Circulation 147 8 2023 93 621
2 Claessens P.J. Peeters R. Claessens L. Claessens C. Claessens J. Claessens P.M. Pulse wave analysis measurements: important, underestimated and undervalued parameters in cardiovascular health problems Front. Cardiovasc. Med. 10 2023 1266258
3 Ferreira A.S. Lopes A. Pulse waveform analysis as a bridge between pulse examination in Chinese medicine and cardiology Chin. J. Integr. Med. 19 4 2013 307 314 23546634
4 Tang Q.F. Tao C. Pan Z. Wang G. Liu K. Pan Z. Liu G. Su B. Liu N. A novel method for vascular age estimation via pressure pulse wave of radial artery Biomed. Signal Process. Control 78 2022 103904
5 Tang Q.F. Huang L. Pan Z.G. Multiple linear regression model for vascular aging assessment based on radial artery pulse wave Eur. J. Int. Med. 28 2019 92 97
6 Shuang P.C. Yang J. Li C. Zang Y. Ma J. Chen F. Luo Y. Zhang D. Effect of bmi on central arterial reflected wave augmentation index, toe-brachial index, brachial-ankle pulse wave velocity and ankle-brachial index in Chinese elderly hypertensive patients with hemorrhagic stroke J. Stroke Cerebrovasc. Dis. 30 9 2021 105945
7 Choi J. Kim S. Joo S. Kim K.S. Augmentation index is associated with coronary revascularization in patients with high framingham risk scores: a hospital-based observational study BMC Cardiovasc. Disord. 15 2015 131 26481213
8 Tang Q.F. Pan Z.Q. Tao C.L. Jiang J. Su B.Y. An H. Liu G.D. Pan Z.G. Vascular age acquired from the pulse signal: a new index to screen early vascular aging Comput. Biol. Med. 151 2022 106355
9 Chen C. Liu J. Zhou N.Y. Wei H. Yi J.X. An E.J. Song S.B. Fan X.Q. Wang N.Y. Correlation analysis between traditional Chinese medicine pulse diagnosis information and degree of vascular sclerosis China J. Tradit. Chin. Med. Pharm. 38 9 2023 4410 4413
10 Liu L. An E.J. Liu J. Wang N.Y. Wang X.Y. Fan X.Q. Song S.B. Characterization of pulse diagnosis information of Qi deficiency and Yang deficiency in northwest healthy people China J. Tradit. Chin. Med. Pharm. 38 02 2023 862 865
11 Xu Y. Xiao H. Xu F. Gao D.W. Feasibility evaluation on ultrafast imaging combined with pulsography in detection of arterial elasticity for patients with primary hypertension J. Shanghai Univ. Tradit. Chin. Med. 30 2 2016 42 45
12 Lee B.J. Jeon Y.J. Bae J.H. Yim M.H. Kim J.Y. Gender differences in arterial pulse wave and anatomical properties in healthy Korean adults Eur. J. Int. Med. 25 2019 41 48
13 Li N. Yu J.R. Hu H.Q. Mao X.B. Zhao Y.P. Huang L.Q. The correlation study of Cun, Guan and Chi position based on wrist pulse characteristics IEEE Access 9 2021 28917 28929
14 Luo T.Y. Cong Q. Qu Y.S. Analysis of the “localization diagnosis” of Cun Kou pulse Inn. Mong. J. Tradit. Chin. Med. 42 1 2023 136 137
15 Liang X.R. Wang F.R. Arteriosclerosis based on the theory of “disease in the pulse, regulate with blood” in the “Huangdi Neijing” J. Integr. Cardiovasc. Cerebrovasc. Dis. 18 2021 2919 2921
16 Zhang J.Y. Peng Q.H. Yan J.F. Bibliometric analysis on research hotspots and evolutionary trends of artificial intelligence application in traditional Chinese medicine diagnosis Digit. Chin. Med. 6 2 2023 136 150
17 Wang N. Yu Y. Huang D. Xu B. Liu J. Li T. Xue L.Y. Shan Z.Y. Chen Y.P. Wang J. Pulse diagnosis signals analysis of fatty liver disease and cirrhosis patients by using machine learning Sci. World J. 2015 2015 859192
18 Pan Z.Q. Tao C.L. Tang Q.F. A fourth derivative based tool for pulse signal special point identification Xiao L. Xu D. Thirteenth International Conference on Graphics and Image Processing (ICGIP 2021), Vol. 12083 2022 International Society for Optics and Photonics, SPIE 120832R
19 Chen H.J. Yuan K.H. The description for yin Yang pulse by Huangdi Neijing J. Basic Chin. Med. 22 11 2016 1453 1454
20 Zhu L.P. Wu H.J. Zhang Z.F. Xu Y.Z.J.T. Tu L.P. Xu F.J. Fei Z.F. Analysis on pulse condition and pulse diagram parameter of 54 healthy college students Acta Univ. Tradit. Med. Sin. Pharmacol. Shanghai 27 2 2013 28 31
21 Shi Y.B. Yang H.Y. Yuan R.H. Discussion on characteristics of radial pulse manifestation from the perspective of tactile frequency and threshold J. Tradit. Chin. Med. 62 14 2021 6
22 Xu B. Chen W. Theory and clinical application of Cun, Guan, Chi on Cunkou pulse J. Sichuan Tradit. Chin. Med. 35 8 2017 23 25
23 Ma J.J. Ren L. Shang D.Y. Zheng H.X. Gu F. Differentiation and treatment of deficiency and excess of five Zang organs in inner canon of Huangdi J. Basic Chin. Med. 29 9 2023 1421 1425
24 Sugawara J. Komine H. Hayashi K. Maeda S. Matsuda M. Relationship between augmentation index obtained from carotid and radial artery pressure waveforms J. Hypertens. 25 2 2007 375 17211244
