Arterial Pulse Waveform Research Articles

Clinical assessment of a non-invasive wearable MEMS pressure sensor array for monitoring of arterial pulse waveform, heart rate and detection of atrial fibrillation

There is an unmet clinical need for a low cost and easy to use wearable devices for continuous cardiovascular health monitoring. A flexible and wearable wristband, based on microelectromechanical sensor (MEMS) elements array was developed to support this need. The performance of the device in cardiovascular monitoring was investigated by (i) comparing the arterial pressure waveform recordings to the gold standard, invasive catheter recording (n = 18), (ii) analyzing the ability to detect irregularities of the rhythm (n = 7), and (iii) measuring the heartrate monitoring accuracy (n = 31). Arterial waveforms carry important physiological information and the comparison study revealed that the recordings made with the wearable device and with the gold standard device resulted in almost identical (r = 0.9–0.99) pulse waveforms. The device can measure the heart rhythm and possible irregularities in it. A clustering analysis demonstrates a perfect classification accuracy between atrial fibrillation (AF) and sinus rhythm. The heartrate monitoring study showed near perfect beat-to-beat accuracy (sensitivity = 99.1%, precision = 100%) on healthy subjects. In contrast, beat-to-beat detection from coronary artery disease patients was challenging, but the averaged heartrate was extracted successfully (95% CI: −1.2 to 1.1 bpm). In conclusion, the results indicate that the device could be useful in remote monitoring of cardiovascular diseases and personalized medicine.

The effects of variation in the arterial pulse waveform on perivascular flow

Cerebrospinal fluid (CSF) enters nervous tissues through perivascular spaces. Flow through these pathways is important for solute transport and to prevent fluid accumulation. Syringomyelia is commonly associated with subarachnoid space obstructions such as Chiari I malformation. However, the mechanism of development of these fluid-filled cavities is unclear. Studies have suggested that changes in the arterial and CSF pressures could alter normal perivascular flow. This study uses an idealised model of the perivascular space to investigate how variation in the arterial pulse influences fluid flow. The model used simulated subarachnoid pressures from healthy controls (N = 9), Chiari patients with (N = 7) and without (N = 8) syringomyelia. A parametric analysis was conducted to determine how features of the arterial pulse altered flow. The features of interest included: the timing and magnitude of the peak displacement, and the area under the curve in the phases of uptake and decline. A secondary aim was to determine if the previously observed differences between subject groups were sensitive to variation in the arterial pulse wave. The study demonstrated that the Chiari patients without a syrinx maintained a significantly higher level of perivascular inflow over a physiologically likely range of pulse wave shapes. The analysis also suggested that age-related changes in the arterial pulse (i.e. increased late systolic pulse amplitude and faster diastolic decay), could increase resistance to perivascular inflow affecting solute transport.

Reliability and Validity of Non-invasive Blood Pressure Measurement System Using Three-Axis Tactile Force Sensor.

Blood pressure (BP) is a physiological parameter reflecting hemodynamic factors and is crucial in evaluating cardiovascular disease and its prognosis. In the present study, the reliability of a non-invasive and continuous BP measurement using a three-axis tactile force sensor was verified. All the data were collected every 2 min for the short-term experiment, and every 10 min for the long-term experiment. In addition, the effects on the BP measurement of external physical factors such as the tension to the radial artery on applying the device and wrist circumference were evaluated. A high correlation between the measured BP with the proposed system and with the cuff-based non-invasive blood pressure, and reproducibility, were demonstrated. All data satisfied the Association for the Advancement of Medical Instrumentation criteria. The external physical factors did not affect the measurement results. In addition to previous research indicating the high reliability of the arterial pulse waveforms, the present results have demonstrated the reliability of numerical BP values, and this implies that the three-axis force sensor can be used as a patient monitoring device.

Tracking DO2 with Compensatory Reserve during Whole Blood Resuscitation in Baboons

BackgroundHemorrhagic shock can be mitigated by timely and accurate resuscitation designed to restore adequate delivery of oxygen (DO2) by increasing cardiac output (CO). However, standard care of using systolic blood pressure (SBP) as a guide for resuscitation has proven ineffective and can be associated with increased morbidity. We have developed a novel vital sign called the compensatory reserve (CRM) generated from analysis of arterial pulse waveform feature changes that has been validated in experimental and clinical models of hemorrhage. We tested the hypothesis that thresholds of DO2 could be accurately defined by CRM while avoiding over resuscitation during whole blood resuscitation following a 25% hemorrhage in non‐human primates.MethodsTo accomplish this, adult male baboons (n=12) were exposed to a progressive controlled hemorrhage that resulted in an average (± SD) maximal reduction of 601 ± 18 ml of their estimated circulating blood volume of 1,262 ± 64 ml based on body weight. Values of DO2 were calculated as the product of CO times O2 carrying capacity of hemoglobin (i.e., Hb content × 1.34).ResultsAverage (± SD) CRM increased from 6 ± 5 % at the end of hemorrhage to 70 ± 7 % at the end of resuscitation. DO2 of 12.1, 10.3, and 7.0 ml O2·kg−1 ·min−1 were calculated at 0% (baseline), 12.5% and 25% blood loss. By linear regression, CRM values of 6% (decompensation), 35%, and 68% corresponded to calculated DO2 values of 6.0, 9.2, and 12.1 ml O2·kg−1 ·min−1 during resuscitation. As such, return of CRM to baseline during resuscitation with only ~ 450 ml provided adequate DO2 (12.5 ml O2·kg−1 ·min−1) while total blood volume replacement (~600 ml) resulted in over resuscitation as indicated by an average increase in SBP (+17 mmHg) and CO (+0.1 L/min) over baseline values.ConclusionConsistent with our hypothesis, thresholds of DO2 were associated with specific CRM values. A target resuscitation CRM value of 70% minimized the requirement for whole blood, while avoiding over resuscitation. Furthermore, CRM at 0% provided a noninvasive metric for determining critical DO2 at approximately 5.4 ml O2·kg−1 ·min−1.Support or Funding InformationThis research was supported in part by appointment of Ms. Koons to the Postgraduate Research Fellowship Program at the US Army Institute of Surgical Research administered by the Oak Ridge Institute for Science and Education through an interagency agreement between the US Department of Energy and USAMRMC. Study funding was provided by a grant from the US Army Combat Casualty Care Research Program (D‐009‐2014‐USAISR). Linearregression of the relationship between DO2 and compensatory reserve during whole blood resuscitation in baboons. Data are expressed as mean ± SE.imageLinearregression of the relationship between DO2 and compensatory reserve during whole blood resuscitation in baboons. Data are expressed as mean ± SE.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

A novel diagnostic system for Doppler ultrasound of the peripheral arteries to detect the presence of thoracic aortic aneurysm.

We aimed to develop a novel ultrasound system and examine its feasibility for noninvasively detecting thoracic aortic aneurysm (TAA) in clinical settings. We developed a novel ultrasound system consisting of a modified console and data analysis algorithm. The exploratory study included 100 patients hospitalized for elective cardiovascular surgery. After admission, the arterial pulse waveform at the left carotid artery was acquired using the novel system. Based on these data, we inferred the presence of TAA based on arterial viscoelasticity and instability, which are reflected into the time-averaged trajectory of deformation of the blood vessel wall caused by disturbance of blood flow. Meanwhile, all patients underwent computed tomography as preoperative screening to confirm the presence of TAA. The sensitivity and specificity of TAA detection using the novel ultrasound system were calculated. The datasets from 37 patients were not suitable for analysis and were thus discarded. Based on computed tomography findings, 40 patients were categorized into the aneurysm group while 23 were judged not to have and aortic aneurysm. On the other hand, 44 patients were diagnosed as having TAA based on ultrasound findings obtained using the novel system. The overall sensitivity and specificity of the ultrasound system were 0.83 and 0.52, respectively. We successfully developed a novel system for noninvasive, ultrasound-based evaluation of the left carotid artery to detect TAA. Although improvements to the probe and diagnostic algorithm are warranted, this device has potential utility for mass screening to detect asymptomatic TAA as part of community-level healthcare programs.

Assessment of arterial baroreflex sensitivity by different computational analyses of pressure wave signals alone

Background and objectiveBaroreflex sensitivity (BRS) is an important indicator of the functionality of the arterial baroreceptors, and its assessment may have major research and clinical implications. An important requirement for its quantification is the continuous recording of electrocardiography (ECG) signal, so as to extract the RR interval, in parallel with continuous beat-to-beat blood pressure recording. We aimed to accurately calculate the RR Interval from pressure wave recordings per se, namely, the Pulse Interval (PI) using various arterial pulse wave analysis algorithms and to evaluate the precision and accuracy of BRS values calculated with the PI compared to BRS values calculated with the RR Interval. MethodsWe analyzed the open access data of the Eurobavar study, which contains a set of ECG and arterial blood pressure (BP) wave signals recorded at 11 European centers. Pressure waveforms were continuously recorded by the Finapres apparatus which uses a finger cuff. The cuff pressure around the finger is dynamically adjusted by a servo-system to equal intra-arterial pressure, thus allowing the continuous recording of beat-to-beat BP waves. RR Interval was calculated from the ECG, whereas, PI was extracted from the arterial pulse waveforms, using 4 different methods (minimum, maximum, maximum 1st derivative and intersecting tangents method). BRS values were estimated by time domain and frequency domain methods. In order to compare agreement, accuracy, precision, variability, and the association between the reference BRS using the RR Interval and the BRS values using PI, standard statistical methods (i.e. intraclass correlation coefficients, RMSE, regression analysis) and Bland-Altman methods were performed. ResultsWe found that analysis of pressure waves alone by frequency-based (i.e. spectral) methods, provides the most accurate results of BRS estimation compared to time-domain methods (ICC > 0.9, R > 0.9, RMSE > 0.8 ms/mmHg). Concerning the spectral method, any algorithm for PI calculation is sufficient, as all show excellent agreement with the respective RR-intervals determined by ECG time series. Only the intersecting tangents and the maximum 1st derivative methods for PI calculation produce the most accurate results in time domain BRS estimation. ConclusionBRS estimation by proper analysis of pressure wave signals alone is feasible and accurate. Further studies are needed to investigate the clinical validity and relevance of the different BRS estimations in diagnostic, prognostic and therapeutic levels.

Utilization of arterial pulse waveform analysis during non-cardiac surgery in Japan: a retrospective observational study using a nationwide claims database.

Arterial pulse waveform analysis (APWA) is used for cardiac output monitoring. However, data on the frequency of and patient characteristics for specialized pressure transducer for APWA (S-APWA) use are lacking. We retrospectively identified 175,201 patients aged 18years or older, who underwent non-cardiac surgery under general anesthesia with an arterial catheter from January 1, 2014, to December 31, 2016. We extracted data on patient demographics, comorbidities, surgical and anesthesia characteristics, and hospital characteristics. Among the full study cohort, 24,605 (14.0%) patients were monitored using S-APWA. Further, the use of S-APWA was higher in patients undergoing high-risk surgery than in those undergoing low-risk surgery [high vs low: adjusted odds ratio (aOR) 1.95; 95% confidence interval (CI) 1.76-2.15, moderate vs low: aOR 1.11; 95% CI 1.01-1.22] and those with more comorbidities than in those with less comorbidities (high vs low: aOR 1.49; 95% CI 1.42-1.56, moderate vs low: aOR 1.25; 95% CI 1.20-1.31). S-APWA use was significantly associated with both surgery risk and patients' comorbidities. In conclusion, our study may provide a benchmark for future studies related to the appropriate use of S-APWA.

Development of Virtual Pulse Simulation for Pulse Diagnosis Studies

Pulse signals can be used to observe the early sign of patients' health problems. From medical researches, monitoring the characteristic of arterial pulse waveform shows some risk indicator of specific diseases, e.g., hypertension, cardiovascular and heart failure diseases. A simple way to get arterial pulse wave is by using fingers to touch the radial artery position on the wrist. In the traditional Chinese medicine, a physician can use the information of arterial pulse wave-form to identify diseases based on the physician’s ability and experience. The improvement of the skill in pulse measurement can be improved by training using various kinds of pulses that represent each disease. This paper proposes a development of the virtual pulse simulation using Augmented Reality (AR) and haptic device for pulse diagnosis studies under various situations. The pulse simulation generates arterial pulse waveforms based on Sine and Gaussian functions. In this study, the mathematical model can generate the pulse wave like human pulse by setting up specific parameters. We can generate pulse waveform which representing different kinds and states of diseases by varying the mathematical model and parameters such as pulse rate or pulse pressure. The features of this work include how to generate force feedback from the mathematical models using the haptic device and how the virtual 3D can display visual feedback. The pulse simulation is useful for the health sciences students, especially the nursing students in training to identify some diseases. The evaluation of the system was carried out by first-year nursing students regarding usability, satisfaction, and performance.

Changes of Arterial Pulse Waveform Characteristics with Gestational Age during Normal Pregnancy

Arterial pulse waveform analysis has been widely used to reflect physiological changes in the cardiovascular system. This study aimed to comprehensively investigate the changes of waveform characteristics of both photoplethysmographic (PPG) and radial pulses with gestational age during normal pregnancy. PPG and radial pulses were simultaneously recorded from 130 healthy pregnant women at seven gestational time points. After normalizing the arterial pulse waveforms, the abscissa of notch point, the total pulse area and the reflection index were extracted and compared between different measurement points and between the PPG and radial pulses using post-hoc multiple comparisons with Bonferrioni correction. The results showed that the effect of gestational age on all the three waveform characteristics was significant (all p < 0.001) after adjusting for maternal age, heart rate and blood pressures. All the three waveform characteristics demonstrated similar changing trends with gestational age, and they were all significantly different between the measurements from gestational week 12–15 and the others (all p < 0.05, except for the PPG total pulse area between the first and second measurement points). In conclusion, this study has comprehensively quantified similar changes of both PPG and radial pulse waveform characteristics with gestational age.

A novel method to quantify arterial pulse waveform morphology: attractor reconstruction for physiologists and clinicians

Current arterial pulse monitoring systems capture data at high frequencies (100–1000 Hz). However, they typically report averaged or low frequency summary data such as heart rate and systolic, mean and diastolic blood pressure. In doing so, a potential wealth of information contained in the high-fidelity waveform data is discarded, data which has long been known to contain useful information on cardiovascular performance.Here we summarise a new mathematical method, attractor reconstruction, which enables the quantification of arterial waveform shape and variability in real-time. The method can handle long streams of non-stationary data and does not require preprocessing of the raw physiological data by the end user. Whilst the detailed mathematical proofs have been described elsewhere (Aston et al 2008 Physiol. Meas. 39), the authors were motivated to write a summary of the method and its potential utility for biomedical researchers, physiologists and clinician readers.Here we illustrate how this new method may supplement and potentially enhance the sensitivity of detecting cardiovascular disturbances, to aid with biomedical research and clinical decision making.

Arterial Pulse Waveform Characteristics Difference between the Three Trimesters of Healthy Pregnant Women.

During pregnancy, the pregnant mother undergoes significant physiological changes in order to accommodate the developing fetus. In recent years, arterial pulse wave has been widely used to reflect these physiological changes. The aim of this study was to investigate the changes of radial pulse and photoplethysmography (PPG) pulse waveform characteristic with gestational age in normal pregnant women. 40 pregnant women volunteers were recruited from February 2016 to September 2016 from the Haidian Maternal & Child Health Hospital in Beijing. Both radial pulses and PPG pulses were recorded simultaneously using a PowerLab data collection system at a sampling rate of 1000Hz for offline analysis. Their pulses were measured from each pregnant woman at three trimesters (first trimester between week 11-13; second trimester between week 20-22 and the third trimester between week 3739). Three waveform characteristics (total pulse area; pulse area1: the area before the notch position; pulse area2: the area after the notch position) were derived. The results showed that the total pulse area and pulse area2 from both radial and PPG pulses decreased significantly between two paired consecutive trimesters (all P<0.01, except the comparisons between the second and third trimesters for PPG pulses). In summary, this study has quantified the pulse waveform characteristic differences in terms of pulse areas between the three trimesters, providing useful scientific evidence to better understand the cardiovascular physiological changes during normal pregnancy.

Pumping the pulse: a bicycle pump to simulate the arterial pulse waveform.

Pumping the pulse: a bicycle pump to simulate the arterial pulse waveform.

Radial artery pulse waveform analysis based on curve fitting using discrete Fourier series

Background and objectives: Radial artery pulse diagnosis has been playing an important role in traditional Chinese medicine (TCM). For its non-invasion and convenience, the pulse diagnosis has great significance in diseases analysis of modern medicine. The practitioners sense the pulse waveforms in patients’ wrist to make diagnoses based on their non-objective personal experience. With the researches of pulse acquisition platforms and computerized analysis methods, the objective study on pulse diagnosis can help the TCM to keep up with the development of modern medicine.Methods: In this paper, we propose a new method to extract feature from pulse waveform based on discrete Fourier series (DFS). It regards the waveform as one kind of signal that consists of a series of sub-components represented by sine and cosine (SC) signals with different frequencies and amplitudes. After the pulse signals are collected and preprocessed, we fit the average waveform for each sample using discrete Fourier series by least squares. The feature vector is comprised by the coefficients of discrete Fourier series function.Results: Compared with the fitting method using Gaussian mixture function, the fitting errors of proposed method are smaller, which indicate that our method can represent the original signal better. The classification performance of proposed feature is superior to the other features extracted from waveform, liking auto-regression model and Gaussian mixture model.Conclusions: The coefficients of optimized DFS function, who is used to fit the arterial pressure waveforms, can obtain better performance in modeling the waveforms and holds more potential information for distinguishing different psychological states.

An extended one-dimensional arterial network model for the simulation of pressure and flow in upper and lower limb extremities

Arterial pulse wave velocity and pulse waveform analysis have become an established component of cardiovascular research. As validation and assessment of devices is not always trivial in an in vivo setting, arterial network computer models may be useful for that purpose. It is, however, mandatory that the model includes sufficient detail, especially when analysing peripheral waveforms. To extend the existing 1D arterial network model (103 segments) of Reymond et al. to a more detailed model (143 segments) including the foot and hand circulation (radial and tibial arteries). The goal is to (i) extend the existing 1D arterial network model (103 segments) of Reymond et al. to a more detailed model (143 segments) including the foot and hand circulation (Radial and Tibial arteries); (ii) use the extending model as testing tool for pOpmètre® (finger–toe pulse wave velocity). The arterial tree dimensions and properties were taken from the literature and completed with data from patient scans. The model solves the one-dimensional form of the Navier-Stokes equations over each arterial segment. A non-linear viscoelastic constitutive law for the arterial wall was considered. Comparison of simulations with & without detailed hand and foot circulation demonstrate important differences in waveform morphology in the distal beds. The completed model predicts pressure and flow waves in the hand and foot arteries which are in good qualitative agreement with the published in-vivo measurements. The agreement is especially good for the shape and wave details of the flow wave, where all features are reproduced in a rather faithful manner. The correlation between ftPWV and aPWV was good and significant (R 2 = 0.95). The Bland and Altman analysis, mean difference was 0.4 m/s, classifying the ftPWV as good agreement with reference method. The extended model yields realistic pressure and flow waveforms in arteries of the hand and the foot.

Characterisation of the aortic pulse profile of a radial artery applanation tonometry device in patients with aortic stenosis

BackgroundAortic stenosis (AS) is commonly associated with myocardial and systemic arterial dysfunction. We use a radial artery applanation tonometry (B-Pro) device to characterise the arterial pulse profile of patients with...

Monitoring modalities and assessment of fluid status: A practice management guideline from the Eastern Association for the Surgery of Trauma.

Fluid administration in critically ill surgical patients must be closely monitored to avoid complications. Resuscitation guided by invasive methods are not consistently associated with improved outcomes. As such, there has been increased use of focused ultrasound and Arterial Pulse Waveform Analysis (APWA) to monitor and aid resuscitation. An assessment of these methods using the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) framework is presented. A subsection of the Surgical Critical Care Task Force of the Practice Management Guideline Committee of EAST conducted two systematic reviews to address the use of focused ultrasound and APWA in surgical patients being evaluated for shock. Six population, intervention, comparator, and outcome (PICO) questions were generated. Critical outcomes were prediction of fluid responsiveness, reductions in organ failures or complications and mortality. Forest plots were generated for summary data and GRADE methodology was used to assess for quality of the evidence. Reviews are registered in PROSPERO, the International Prospective Register of Systematic Reviews (42015032402 and 42015032530). Twelve focused ultrasound studies and 20 APWA investigations met inclusion criteria. The appropriateness of focused ultrasound or APWA-based protocols to predict fluid responsiveness varied widely by study groups. Results were mixed in the one focused ultrasound study and 9 APWA studies addressing reductions in organ failures or complications. There was no mortality advantage of either modality versus standard care. Quality of the evidence was considered very low to low across all PICO questions. Focused ultrasound and APWA compare favorably to standard methods of evaluation but only in specific clinical settings. Therefore, conditional recommendations are made for the use of these modalities in surgical patients being evaluated for shock. Systematic Review, level II.

Non-invasive, MRI-based estimation of patient-specific aortic blood pressure using one-dimensional blood flow modelling

Background and objectivesClinical evidence shows that central (aortic) blood pressure (CBP) is a better marker of cardiovascular risk than brachial pressure [1]. However, CBP can only be accurately measured invasively, through catheterisation. We propose a novel approach to estimate CBP non-invasively from aortic MRI data and a non-invasive peripheral (brachial) pressure measurement, using a one-dimensional (1-D) model of aortic blood flow.MethodsWe created a population of virtual (computed) subjects, each with distinctive arterial pulse waveforms available at multiple arterial locations, to assess our approach. This was achieved by varying cardiac (stroke volume, cardiac period, time of systole) and arterial (pulse wave velocity, peripheral vascular resistance) parameters of a distributed 1-D model of the larger systemic arteries [2] within a wide range of physiologically plausible values. After optimising our algorithm for the aortic 1-D model in silico, we tested its accuracy in a clinical population of 8 post-coarctation repair patients.ResultsResults from our in silico study, after varying cardiac and arterial parameters by ± 30%, showed maximum relative errors for systolic, mean and diastolic CBP of 4.5%, 3.6% and 4.2%, respectively. Average relative errors for systolic, mean and diastolic CBP were 2.7%, 0.9% and 1.2%, respectively. Corresponding average relative errors from our clinical study were 5.4%, 1.5% and 8.0%.Figure 1CBP estimation using the aortic 1-D model for a given virtual patient.Figure 2Systolic CBP estimated using the aortic 1-D model against reference systolic CBP values from in silico and in vivo data.ConclusionsWe have provided a proof of concept for the non-invasive estimation of patient-specific central blood pressure using computational aortic blood flow modelling in combination with MRI data and a non-invasive peripheral pressure measurement.

Carotid Arterial Pulse Waveform Measurements Using Fiber Bragg Grating Pulse Probe.

Arterial pulse is an established source of information for the clinical assessment of cardiovascular health. The central aortic pressure is known to be a better predictor of cardiovascular status than the peripheral pressure. The carotid arterial pulse is considered to be the best indicator of the central aortic pressure. The present work deals with the development of a novel noninvasive probe based on fiber Bragg grating (FBG) sensor for the real-time acquisition of the pulse waveform in the carotid arterial site. The fiber Bragg grating pulse probe (FBGPP) developed is used to obtain the carotid arterial pulse waveform (CAPW) of individual subjects, in the form of beat-to-beat carotid pulse. The FBGPP developed comprises of an elastic rubber diaphragm that comes into contact with the skin below, which the carotid artery is pulsating, creating strain variations over it. Effectively, the carotid arterial pulse is tranduced into the strain variations over a rubber diaphragm, which is acquired by the FBG sensor bonded over it. The FBGPP is designed such that the positioning and the access for the device to the carotid arterial site can be carried out with ease. Furthermore, the recorded CAPW is subjected to the pulse wave analysis in order to evaluate vital cardiovascular parameters like heart rate, left ventricular ejection time, carotid augmentation index, and ejection duration index, which are indicators of the cardiac health of the subject and the performance of the heart. Also, the linearity between these cardiovascular parameters is explored for a sample size of 55.

Central diastolic pressure decay mediates the relationship between aortic stiffness and myocardial viability: potential implications for aortosclerosis-induced myocardial ischemia.

Stiffening of the aorta often precedes coronary events, but little is known about the aetiological mechanism. We hypothesized that the predisposition to myocardial ischemia could be attributable to aortosclerosis-induced alterations in the central haemodynamics during diastole. Using noninvasive tonometry and ultrasonography, we investigated the arterial pressure pulse waveforms, pulse wave velocities (PWVs) and compliance in 222 patients with hypertension. The diastolic pressure decay was quantified by fitting a mono-exponential curve as P(t) = P0e [λ: decay index; P0: end-systolic pressure; t: time from end-systole]. The myocardial oxygen supply/demand balance was estimated from the subendocardial viability index (SVI). The aortic pressure decay fit to an exponential curve significantly (R = 0.98 ± 0.02) and more closely than the radial pressure decay (P < 0.001). The aortic decay index (median, 0.59 s) was associated with the aortic PWV and compliance (but not with the peripheral PWV or resistance), even after controlling for age, sex, renal function, diabetes and hypercholesterolemia (P < 0.001). Also, both the aortic PWV and compliance (together with the augmentation index) were related to the SVI, although these relationships were no longer significant after accounting for the decay index. Mediation analysis revealed substantial mediating effects of the decay index on the relationship between aortic PWV or compliance and SVI (75-100%), despite the lack of similar effects of the augmentation index. Aortic stiffening with reduced compliance potentially impairs myocardial viability by accelerating the diastolic exponential decay (rather than through enhancing late-systolic augmentation) of the central blood pressure, thus predisposing hypertensive patients to ischemic heart disease.

Central diastolic pressure exponential decay constant and subendocardial flow supply.

Central diastolic pressure exponential decay constant and subendocardial flow supply.