Radial Pulse Spectrum Analysis as Risk Markers to Improve the Risk Stratification of Silent Myocardial Ischemia in Type 2 Diabetic Patients.

Diabetic patients with silent myocardial ischemia (SMI) have elevated rates of morbidity and mortality and need intensive care and monitoring. An early predictor of SMI may lead to early diagnosis and medical treatment to prevent progression and adverse clinical events. Therefore, this paper was aimed to evaluate the radial pulse spectrum as risk markers to improve the risk stratification of SMI in type-2 diabetic patients; 195 diabetic patients at high-risk of SMI were enrolled. All patients underwent myocardial perfusion imaging and radial pressure wave measurement. The spectrum analysis of the radial pressure wave was calculated and transformed into Fourier series coefficients Cns and Pns. The risk of SMI (odds ratio: 4.46, 95%, C.I. 1.61-12.4, [Formula: see text]) was raised in diabetic patients classified high-risk group by C2. Multivariable regression analysis showed that C2 ([Formula: see text]) and ankle-brachial index [(ABI) [Formula: see text])] were related to SMI ([Formula: see text] and [Formula: see text]). The myocardial ischemic score (MIS), combining C2, C3, and P5, the albumin-to-creatinine ratio (ACR), and ABI, presented an excellent risk stratification performance in enrolled patients (odds ratio: 5.78, 95%, C.I. 2.29-14.6, [Formula: see text]). The area under receiver operating characteristic curves for C2, C3, P5, ABI, ACR, and MIS were 0.66, 0.60, 0.68, 0.51, 0.56, and 0.74, respectively, in identifying SMI. This paper demonstrated that C2 was independently associated with the extent of SMI in multivariable regression analysis. Odds ratio and chi-square tests reflected that C2 could be an important marker for the risk stratification of SMI. Furthermore, MIS, adding radial pulse spectrum analysis to ACR and ABI, could significantly improve the risk stratification of SMI in type-2 diabetic patients compared to any single risk factor.

Effect of black tea consumption on radial blood pulse spectrum and cognitive health.

Black tea consumption has been proven to improve endothelial function and to lower the risk of stroke and cognitive impairment. Several effects of black tea on cardiovascular system had been surveyed. However, the black tea effect on pressure pulse spectrum remains unknown. The study was aimed to investigate the influence of black tea on radial blood pressure and Pulse Spectrum. Fourteen healthy subjects received water and single doses of black tea (0.05g/Kg) in separate weeks. The radial blood pressure and pulse wave were measured and the pressure pulses were evaluated using harmonic analysis. This report confirmed that black tea consumption (dose=0.05g/Kg) significantly increased third, fifth, (P<0.1), sixth, seventh, and eighth harmonics (p<0.05) of radial pressure wave comparing to water control. We proposed that black tea may increase cerebral blood flow (CBF), which was deduced from the results and from the conclusions of previous studies. The results also showed that the harmonic components of pressure pulse could be the vascular kinetic index that assessed the hemodynamic status in each time frame before and after consumption of black tea.

Past, Present, and Future of the Pulse Examination ( mài zhen).

The pulse examination ( mài zhen) is a unique diagnostic approach of Traditional Chinese Medicine. The description of pulse examination in the history of Traditional Chinese Medicine is full of amazement and mythology. After researching in hemodynamics and investigating in clinical application for three decades, this article describes the development and the merits and demerits of pulse examination. The experiences of the ancients are tried to be illustrated with modern knowledge and language. As the theory of resonant blood circulation is discovered, Traditional Chinese Medicine could be on the shoulder of Newton and then lead the development of modern medicine. Hope the tool of pulse examination constructed according to eigen-vector with specific time domain and position can bring the running water for Traditional Chinese Medicine. Quantitative research could overcome the plight of analog logic qualitative research, and therefore bring new health revolution.

Effects of antihypertensive drugs on specific harmonic indices of the pulse waveform in normotensive Wistar Kyoto rats.

We used a self-comparison method and harmonic analysis to compare the blood pressure wave before and after the injection of antihypertensive drugs (atenolol, captopril, and losartan) in normotensive Wistar Kyoto rats. Systolic and diastolic blood pressures decreased significantly after the intraperitoneal injection of drugs. Atenolol significantly reduced all the harmonic proportions of the pulse wave, while captopril and losartan significantly increased the first and fourth harmonic proportions. These findings are the same as those reported for human subjects and confirm that harmonic analysis of the pressure pulse is a useful method to study the efficacy of antihypertensive drugs.

Relations between beat-to-beat microcirculatory blood flow and variations therein.

OBJECTIVE: Analyzing the beat-to-beat cardiovascular variability (e.g., heart-rate variability analysis) provides important information regarding circulatory autonomic control. The present study aimed to use laser Doppler flowmetry (LDF) and beat-to-beat analysis to elucidate changes in the microcirculatory blood flow (MBF) and variations (MBFV) therein induced by local heating stimulation. METHOD: For each experiment, we applied nonpainful local heating and recorded a 20-min heating effect, which was segmented into four measurements separated by 5 min as M1-M4. DCflux (average LDF flux) was calculated for each pulse, and the coefficient of variance of DCflux (DCCV) was then calculated to evaluate the beat-to-beat MBFV. RESULTS: In the linear regression analysis of the M2-M4 data sequence, the slope between relative changes (compared with M1 values) in DCCV and DCflux, and those between the proceeding DCCV and the subsequent DCflux, were negative (R(2) > 0.40 for all; p < 0.05). CONCLUSION: This is the first study to reveal a possible time-domain relationship between changes in MBF and MBFV parameters. Our results suggest that MBFV evaluated from the beat-to-beat LDF waveform is useful for monitoring the microcirculatory regulatory activities of arteriolar openings, and might therefore be particularly meaningful when evaluating treatment techniques or drugs aimed at improving microcirculatory perfusion.

Effects of acupuncture at the Hoku acupoint on the pulsatile laser Doppler signal at the heartbeat frequency.

We aimed to assess the effects of acupuncture by analyzing the alternating current (AC) component of skin blood-flow signals (around the heartbeat frequency) simultaneously recorded at the Hoku acupoint, which is an important acupoint in oriental medicine, and two nearby non-acupoints following acupuncture stimulation (AS). Laser Doppler flowmetry signals were measured in 28 experiments on nine volunteers. Each experiment involved the recording of a 20-min control-data sequence and two sets of effects data recorded 0-20 min and 50-70 min after the AS had been stopped. The direct current (DC) and AC components (DCflux and ACflux, respectively), pulse width (PW), and foot delay time (FDT) of the flux signal were calculated. The DCflux, ACflux, PW, and FDT were all significantly increased only at Hoku following AS. Regression analysis between the DCflux and ACflux revealed that the slope was largest (>1) at Hoku among the measurement sites. Our results indicated that both the DCflux and ACflux in the microcirculatory perfusion were increased by stimulation at the Hoku acupoint, with the change being greatest for the latter. Parameters calculated from the pulsatile flux waveform, such as the PW and FDT, could contribute to noninvasive evaluations of the sympathetic neural activities and of the improvement in perfusion following AS.

Noninvasive blood glucose monitoring using the optical signal of pulsatile microcirculation: a pilot study in subjects with diabetes.

OBJECTIVE: The objective of this study was to determine the conditions for optimizing measurements obtained with a noninvasive blood glucose monitor using the optical signal of pulsatile microcirculation (OSPM) in both prediabetic and diabetic subjects receiving medication. RESEARCH DESIGN AND METHODS: Eighteen subjects (3 prediabetic, 15 diabetic) aged 61.8 [15.9] years (mean [S.D.]) were studied. OSPM was the pulsatile component (P) of the signal obtained and analyzed by a blood glucose monitor. The measurement was calibrated to the fingerstick meter for each subject for personal calibration. Data were obtained from all subjects using both meters. RESULTS: A total of 179 data pairs were measured and analyzed. The validity of the position of the tested finger was assessed using the position criterion, which resulted in the removal of 38 data pairs. The criterion for the intensity of the P signal was satisfied by 141 data pairs, with nonconforming data (with a much lower P signal) mainly occurring below 26 degrees C. A total of 113 data points passed both criteria, and 100% of them fell within Zones A and B of the Clarke error grid. Data in Zones A and B exhibited a linear relationship (r=.81; slope=0.82; intercept=28.0) between noninvasive and fingerstick measurements. CONCLUSIONS: Environmental temperature has the greatest influence on the capability of the OSPM technique to monitoring blood glucose concentration, which is subject dependent. The position of the tested finger is the second major factor, hence a carefully designed finger adaptor is essential.

Connection between RR-interval length and the pulsatile microcirculatory flow.

The present study used laser Doppler flowmetry (LDF) to investigate the connection between skin microcirculatory flow and the length of the RR interval (LRR). Local heating was performed on healthy volunteers to further elucidate its effect on LDF index. ECG and LDF signals were measured in 102 trials on seven volunteers. Each experiment involved a 5 min control and a 5 min heating-effect sequence. Each laser Doppler flux pulse was categorized into four groups according to its LRR compared with the 5 min average LRR. Synchronized averaging analysis was applied to the four groups of pulses to obtain their averaged waveforms, from which four flux parameters were calculated. The ac component of the flux increased significantly with increasing LRR, and the differences therein between the groups with LRR more than 4% smaller and more than 4% larger than the average LRR increased from 15.8% during the control period to 23.9% during the heating period. Understanding of the different flux responses between the control and local-heating experiments may aid the development of a new index, which helps to avoid LDF's main drawback of providing only qualitative measurement.

Spectral analysis on the microcirculatory laser Doppler signal at the acupuncture point.

We aimed to characterize the frequency spectra of skin blood flow signals simultaneously recorded at Hoku, an important acupoint in oriental medicine, and two nearby nonacupoints to understand the underlying physiological mechanism of acupuncture points. ECG and laser Doppler flowmetry signals were measured simultaneously. A four-level Haar wavelet transform was applied to the measured 20-minute LDF signals, and periodic oscillations with five characteristic frequency peaks were obtained within the following frequency bands: 0.0095-0.021, 0.021-0.052, 0.052-0.145, 0.145-0.6, and 0.6-1.6 Hz (defined as FR1-FR5), respectively. The power in FR3 was significantly larger at Hoku than at the two nonacupoints. Spectral analysis of the flux signal revealed that one of the major microcirculatory differences between acupoints and nonacupoints was in the different myogenic responses of their vascular beds. This information may aid the development of a method to noninvasively study the microcirculatory characteristics of the acupoint.

Effects of angiotensin II on flux rise time in rats (a time index of laser Doppler flowmetry) and its relation with microvascular structures.

Laser Doppler flowmetry (LDF) is a popular method for monitoring the microcirculation, but it does not provide absolute measurements on local area with small size microvessels. Instead, the mean flux response is generally compared between before and after stimulus. In this study, we proposed a new dimension for comparing the LDF signals. The flux rise time (FRT), a time index with absolute physical quantity, was extracted from noisy LDF signals using a pulsatile-based synchronized-averaging method. We investigated the changes of FRT and its relation to the microvascular resistance (MVR) under the selective effects of angiotensin II (Ang II) on the kidney and the plantar palm. Ang II was infused into anesthetized Wistar Kyoto rats via the femoral vein for 1 h. Using the heartbeat as a self-trigger, we calculated the FRT and MVR from the renal cortical flux, plantar palm flux, and abdominal aortic blood pressure recorded before, during, and after Ang II infusion. The control FRT values were similar in the two vascular beds. Ang II decreased the renal cortical flux but significantly increased the FRT and MVR of both beds. The effects on the renal FRT and renal MVR were selectively larger than those on the palm FRT and palm MVR. The results indicate that the changes of FRT and MVR are similarly physiologically linked with microvascular structures. As an MVR-related absolute physical quantity, the FRT could be developed as a monitoring tool in physiological, pathological, and pharmacological investigations.

Study on the microcirculatory blood velocity of acupoint monitored by laser Doppler signal.

Meridian system composed of acupoints is the most fundamental concept to build oriental medicine. In this study, we employ LDF measurement to compare the microcirculatory blood velocity of acupuncture point and its surrounding tissues. Measurements were performed around an important acupoint in oriental medicine, Hoh-Ku (Li4, on the hand), in healthy volunteers. The study presented has shown that the acupoints have significantly slower mean blood velocity than their surrounding tissues (p all < 0.005). This finding facilitates the detection of the position of acupuncture point and helps us to provide a possible connection between microcirculatory physiology and the underlying mechanism of acupoints.

Evaluation of stationarity of laser Doppler signal in the pulse-based synchronized-averaging analysis.

Pulse parameters calculated from the LDF waveform based on time-domain synchronized averaging analysis were shown to be able to discriminate the difference in microvascular resistance, however its applicability depends seriously on the assumption of signal stationarity. In this study, our aim is to investigate the effect of pulse number, which may destroy the signal stationarity, on the pulse LDF parameters. The study presented here has established the criteria for pulse number to achieve the signal stationarity so that the microcirculatory discriminability of the pulse-based time-averaging analysis on LDF signal can be improved. The proposed quantitative method to verify the assumption of signal stationarity when utilizing time-averaging can also be applied to analysis of other bio-signals.

Microcirculatory characteristics of acupuncture points obtained by laser Doppler flowmetry.

Acupuncture points (acupoints) form part of the meridian system that constitutes the most fundamental concept in oriental medicine, but their physiological basis has not been clarified. In this study we employed laser Doppler flowmetry (LDF) to extract the microcirculatory characteristics of acupoints and their surrounding tissues, and we interpreted the results from the viewpoint of microcirculatory physiology. Three groups of measurements were performed focusing on the following two important acupoints in oriental medicine in healthy volunteers (n = 13 for group A and n = 9 for groups B and C, respectively): Hoh-Ku (Li4, on the hand) and Ching-Ku (B64, on the foot). The two groups of measurements around Hoh-Ku (Groups A and B) were so designed as to examine the effect of the direction of the nonacupoint away from the acupoint, whereas comparison between the Hoh-Ku and the Ching-Ku measurements was to verify whether the phenomenon was consistent in the upper and the lower extremities. We found that the mean LDF signals were significantly larger at the acupoints than in their surrounding tissues (all p < 0.05), which indicates a larger blood supply into the microvascular beds of acupoints. The results indicate that the physical properties of the vascular structure of acupoints may affect the perfusion resistance, and thereby modulate the microcirculatory perfusion in accordance with tissue needs. This finding facilitates the localization of acupoints, helps in identifying the connection between microcirculatory physiology and responses to acupoint stimulation, and introduces an objective research method for understanding the mechanisms that underlie oriental medicine.

Losing harmonic stability of arterial pulse in terminally ill patients.

OBJECTIVE: To measure the coefficient of variation of the harmonic magnitude (HCV) of the radial arterial pulse before death of cancer patients. METHODS: We non-invasively recorded the radical arterial pulse of 21 end-stage cancer patients, 31 healthy subjects, and 47 outpatient department (OPD) patients. During the 2-week study, eight cancer patients expired. RESULTS: There were no considerable differences in diastolic or systolic blood pressure between cancer patients and other subjects; however, all six HCVs were significantly higher in the cancer patients (P<0.05). Within the cancer patient group, the first and second HCV were notably higher in the patients that expired (P<0.05), and the first to fourth HCVs were significantly increased on their last day (P<0.05). In the control healthy subjects and the OPD group, the HCVs were below 5 and 8%, respectively. In the cancer patients, the third to sixth HCVs were higher than 15%. On the last day of the cancer patients that expired, even the first and second HCVs were higher than 15%. CONCLUSIONS: During the dying process, the traditional diastolic and systolic blood pressure did not show significant changes; however, all the harmonic components gradually lost their stability. The HCVs, which increased first for the high-frequency components and then the low-frequency components, could quantitatively reflect the severity of different stages of illness.

The natural frequencies of the arterial system and their relation to the heart rate.

We assume the major function of the arterial system is transporting energy via its transverse vibration to facilitate the blood flowing all the way down to the microcirculation. A highly efficient system is related to maintaining a large pressure pulse along the artery for a given ventricular power. The arterial system is described as a composition of many infinitesimal Windkessels. The strong tethering in the longitudinal direction connects all the Windkessels together and makes them vibrate in coupled modes. It was assumed that at rest condition, the arterial system is in a steady distributed oscillatory state, which is the superposition of many harmonic modes of the transverse vibration in the arterial wall and the adherent blood. Every vibration mode has its own characteristic frequency, which depends on the geometry, the mass density, the elasticity, and the tethering of the arterial system. If the heart rate is near the fundamental natural frequency, the system is in a good resonance condition, we call this "frequency matching." In this condition, the pulsatile pressure wave is maximized. A pressure wave equation derived previously was used to predict this fundamental frequency. The theoretical result gave that heart rate is proportional to the average high-frequency phase velocity of the pressure wave and the inverse of the animal body length dimension. The area compliance related to the efficiency of the circulatory system is also mentioned.

One important area gradient force has been omitted in the Moens and Korteweg's Equation.

Pulse wave velocity is mostly related to the young's modulus by the Moens and Korteweg's formula. In deriving this formula, the wall's effect on the blood was ignored at the first step and the pressure gradient was considered as the only driving force in the axial flow of the blood. The local area gradient was assumed to be zero. However, for a real arterial system with compliance, the area gradient is automatically accompanied with the pressure gradient and it will contribute an area gradient force. This force has been omitted so far without any justification because it will contribute a nonlinear term and also leads an obstacle for the analogy with the transmission line theory. We give a quantitative evaluation of the ratio of the area gradient force to the pressure gradient force and find that it is more than 50% in the main artery. This shows the inadequacy and the inaccuracy of the pulse wave velocity derived based on this axial flow equation. We propose that starting from the radial equation of motion might provide an alternate, feasible method to study hemodynamics by energy concern.

Pressure pulse velocity is related to the longitudinal elastic properties of the artery.

It is known that arteries in their natural position are always subject to a longitudinal stress. However, the effect of this strong longitudinal tension has seldom been addressed. In this paper, we point out that the traditional pulse wave velocity formulae considering only the circumferential elasticity fail to include all the important energies. We present a vigorous derivation of a pressure wave equation, the pressure wave equation with total energy, which considers all the important energies of the whole arterial system by treating the arterial wall and the blood as one system. Our model proposes that the energy transport in the main arterial system is primarily via the transverse vibration motion of the elastic wall. The final equation indicates that the longitudinal stress is essential and the high frequency phase velocity is related to the longitudinal tension along the arterial wall and its Young's shearing modulus. By applying this equation, we suggest that longitudinal elastic property is an important factor in hemodynamics and in the treatment of cardiovascular diseases.