Estimation Of Central Blood Pressure Research Articles

Validation of a Suprasystolic Cuff System for Static and Dynamic Representation of the Central Pressure Waveform.

Noninvasive pulse waveform analysis is valuable for central cardiovascular assessment, yet controversies persist over its validity in peripheral measurements. Our objective was to compare waveform features from a cuff system with suprasystolic blood pressure hold with an invasive aortic measurement. This study analyzed data from 88 subjects undergoing concurrent aortic catheterization and brachial pulse waveform acquisition using a suprasystolic blood pressure cuff system. Oscillometric blood pressure (BP) was compared with invasive aortic systolic BP and diastolic BP. Association between cuff and catheter waveform features was performed on a set of 15 parameters inclusive of magnitudes, time intervals, pressure-time integrals, and slopes of the pulsations. The evaluation covered both static (subject-averaged values) and dynamic (breathing-induced fluctuations) behaviors. Peripheral BP values from the cuff device were higher than catheter values (systolic BP-residual, 6.5 mm Hg; diastolic BP-residual, 12.4 mm Hg). Physiological correction for pressure amplification in the arterial system improved systolic BP prediction (r2=0.83). Dynamic calibration generated noninvasive BP fluctuations that reflect those invasively measured (systolic BP Pearson R=0.73, P<0.001; diastolic BP Pearson R=0.53, P<0.001). Static and dynamic analyses revealed a set of parameters with strong associations between catheter and cuff (Pearson R>0.5, P<0.001), encompassing magnitudes, timings, and pressure-time integrals but not slope-based parameters. This study demonstrated that the device and methods for peripheral waveform measurements presented here can be used for noninvasive estimation of central BP and a subset of aortic waveform features. These results serve as a benchmark for central cardiovascular assessment using suprasystolic BP cuff-based devices and contribute to preserving system dynamics in noninvasive measurements.

Assessing the accuracy of systolic aortic pressure estimation from a brachial cuff alone: a comparison with radial tonometry.

A novel method for estimating central systolic aortic pressure (cSAP) has emerged, relying solely on peripheral mean (MBP) and diastolic (DBP) blood pressures. We aimed to assess the accuracy of this Direct Central Blood Pressure estimation using cuff alone (DCBPcuff=MBP²/DBP) in comparison to the use of generalized transfer function to derive cSAP from radial tonometry (cSAPtono). This retrospective analysis involved International Database of Central Arterial properties for Risk Stratification (IDCARS) data (Aparicio et al., Am J Hypertens 2022). The dataset encompassed 10,930 subjects from 13 longitudinal cohort studies worldwide (54.8%women; median age 46.0 years; office hypertension: 40.1%; treated: 61.0%), documenting cSAPtono via SphygmoCor calibrated against brachial systolic BP (SBP) and DBP. Our analysis focused on aggregate group data from 12/13 studies (89%patients) where full BP dataset was available. A 35% form factor was used to estimate MBP = (DBP+(0.35×(SBP-DBP)), from which DCBPcuff was derived. The predefined acceptable error for cSAPtono estimation was set at ≤5mmHg. The cSAPtono values ranged 103.8-127.0 mmHg (n=12). The error between DCBPcuff and cSAPtono was 0.2 ± 1.4 mmHg, with no influence of the mean. Errors ranged from -1.8 to 2.9 mmHg across studies. No significant difference in errors was observed between BP measurements obtained via oscillometry (n=9) vs auscultation (n=3) (p=0.50). Using published aggregate group data and a 35% form factor, DCBPcuff demonstrated remarkable accuracy in estimating cSAPtono, regardless of the BP measurement technique. However, given that individual BP values were unavailable, further documentation is required to establish DCBPcuff's precision.

Non-Invasive Estimation of Central Systolic Blood Pressure by Radial Tonometry: A Simplified Approach.

Central systolic blood pressure (cSBP) provides valuable clinical and physiological information. A recent invasive study showed that cSBP can be reliably estimated from mean (MBP) and diastolic (DBP) blood pressure. In this non-invasive study, we compared cSBP calculated using a Direct Central Blood Pressure estimation (DCBP = MBP2/DBP) with cSBP estimated by radial tonometry. Consecutive patients referred for cardiovascular assessment and prevention were prospectively included. Using applanation tonometry with SphygmoCor device, cSBP was estimated using an inbuilt generalized transfer function derived from radial pressure waveform, which was calibrated to oscillometric brachial SBP and DBP. The time-averaged MBP was calculated from the radial pulse waveform. The minimum acceptable error (DCBP-cSBP) was set at ≤5 (mean) and ≤8 mmHg (SD). We included 160 patients (58 years, 54%men). The cSBP was 123.1 ± 18.3 mmHg (range 86-181 mmHg). The (DCBP-cSBP) error was -1.4 ± 4.9 mmHg. There was a linear relationship between cSBP and DCBP (R2 = 0.93). Forty-seven patients (29%) had cSBP values ≥ 130 mmHg, and a DCBP value > 126 mmHg exhibited a sensitivity of 91.5% and specificity of 94.7% in discriminating this threshold (Youden index = 0.86; AUC = 0.965). Using the DCBP formula, radial tonometry allows for the robust estimation of cSBP without the need for a generalized transfer function. This finding may have implications for risk stratification.

PS-C03-12: FINGER-TO-TOE PULSE WAVE VELOCITY IN RESPONSE TO SITTING POSITION

Objective: Aortic stiffness is a non-traditional risk factor for cardiovascular disease and mortality and is associated with increased central pulse pressure. It is generally measured by carotid-femoral pulse wave velocity (PWV) in a supine position. We hypothesized that, in a sitting position, the additional hydrostatic pressure exerted on the vascular wall could represent a vascular stress test. Two alternative methods can now estimate aortic stiffness and can be used conveniently in different positions: 1) brachial pulse wave analysis approach used by Mobil-O-Graph and 2) transit time approach using finger-to-toe PWV by photoplethysmography with the pOpmetre. The aim of the present study is to determine the impact of postural changes on PWV and central blood pressure estimation using these two distinct methods. Design and method: Central blood pressure and PWV were assessed in 20 healthy subjects using Mobil-O-Graph (PWV-M) and pOpmetre (PWV-pop) in three positions: supine in bed, supine in reclining chair and sitting. Central systolic blood pressure (SBP) was determined by calibration of brachial systolic and diastolic blood pressures by both methods (SBP-M and SBP-pop). Generalized estimating equations were used for analysis. Results: The PWV-M remained relatively constant and generally independent of the position (5.5 ± 1.0, 5.3 ± 1.0 and 5.5 ± 1.0 m/s). While PWV-M and PWV-pop were similar in the supine position (5.5 ± 1.0 vs 5.4 ± 1.3 m/s, P = NS), PWV-pop increased very significantly to 5.9 ± 1.5 m/s in supine in reclining chair position (P = 0.04), and to 9.2 ± 1.7 m/s in sitting position (P &lt; 0.001). Central blood pressure estimation remained similar for SBP-M (110.2 ± 10.3 vs 106.9 ± 10.5 vs 108.8 ± 11.1 mmHg, P = NS) and for SBP-pop (107.7 ± 10.4 vs 110.3 ± 9.6 vs 109.5 ± 9.9 mmHg, P = NS). Conclusions: These results suggest that estimated PWV by brachial pulse wave analysis remains robust independent of position. However, the estimated finger-to-toe PWV by pulse transit time increases remarkably with the imposition of hydrostatic pressure on the vascular wall. We conclude that the finger-to-toe PWV may provide the opportunity to evaluated vascular wall property in a dynamic fashion using postural changes as a stress test.

Single measurement estimation of central blood pressure using an arterial transfer function

Background: Central blood pressure (BP) better reflects the loading conditions on the major organs and is more closely correlated with future cardiovascular events. The increased invasiveness and risk of infection prevents the routine measurement of central BP. Arterial transfer functions can provide central BP estimates from clinically available peripheral measurements. However, current methods are either generalized, potentially lacking the ability to adapt to inter and intra subject variability, or individualized based on additional, clinically unavailable, pulse transit time measurements. This work proposes a novel, self-contained method for individualizing an arterial transfer function from a single peripheral pressure measurement, capable of accurately estimating central BP in a range of hemodynamic conditions. Methods: Pulse wave analysis of femoral BP waves was employed to formulate initial approximations of central BP and arterial inlet flow waveforms, to serve as objective functions for the identification of all model parameters. Root mean squared error (RMSE), and systolic and pulse pressure errors were assessed with respect to invasive aortic BP measurements in a seven (7) porcine endotoxin experiments. Systolic and pulse pressure errors were analysed using Bland-Altman analysis. Method accuracy is also compared with an idealized transfer function, derived using the measured aortic-femoral pulse transit time and minimizing the RMSE of model output pressure with respect to reference aortic pressure, a generalized transfer function model, and invasive femoral pressure measurements. Results: Mean bias and limits of agreement (95% CI) for the proposed method were 1.0(-4.6, 6.7)mmHg and -1.0(-6.6, 4.6)mmHg for systolic and pulse pressure, respectively, compared to 3.6(-0.9, 8.2)mmHg and 2.7(-1.8, 7.3)mmHg for the generalized transfer function model. Mean bias and limits of agreement for femoral pressure measurements were -6.4(-15.0, 2.3)mmHg and -9.4(-18.1, -0.8)mmHg, for systolic and pulse pressure, respectively. The pooled mean and standard deviation of the RMSE produced by the single measurement method, relative to reference aortic pressure, was 4.3(1.1)mmHg, consistent with estimates produced by the idealized transfer function, 3.9(1.2)mmHg, and improving of the generalized transfer function, 4.6(1.4)mmHg. Conclusions: The proposed single measurement method provides accurate central BP estimates from routinely available peripheral pressure measurements, and nothing else. The method allows for the individualization of transfer functions on a per patient basis to better capture changes in patient condition during the progression of disease and subsequent treatment, at no additional clinical cost.

Enhancing central blood pressure accuracy through statistical modeling: A proof-of-concept study.

Non-invasive estimation of central blood pressure (BP) may have better prognostic value than brachial BP. The accuracy of central BP is limited in certain populations, such as in females and the elderly. This study aims to examine whether statistical modeling of central BP for clinical and hemodynamic parameters results in enhanced accuracy. This study is a cross-sectional analysis of 500 patients who underwent cardiac catheterization. Non-invasive brachial cuff and central BP were measured simultaneously to invasive aortic systolic BP (AoSBP). Central BP was calibrated for brachial systolic (SBP) and diastolic BP (Type I calibration; C1SBP) or brachial mean and diastolic BP (Type II calibration; C2SBP). Differences between central SBP and the corresponding AoSBP were assessed with linear regression models using clinical and hemodynamic parameters. These parameters were then added to C1SBP and C2SBP in adjusted models to predict AoSBP. Accuracy and precision were computed in the overall population and per age or sex strata. C1SBP underestimated AoSBP by 11.2 mmHg (±13.5) and C2SBP overestimated it by 6.2 mmHg (±14.8). Estimated SBP amplification and heart rate were the greatest predictors of C1- and C2-AoSBP accuracies, respectively. Statistical modeling improved both accuracy (0.0 mmHg) and precision (±11.4) but more importantly, eliminated the differences of accuracy seen in different sex and age groups. Statistical modeling greatly enhances the accuracy of central BP measurements and abolishes sex- and age-based differences. Such factors could easily be implemented in central BP devices to improve their accuracy.

Central blood pressure estimation in type 1 diabetes: impact and implications of peripheral calibration method.

Peripheral blood pressure (BP) waveforms are used for noninvasive central BP estimation. Central BP could assist in cardiovascular risk assessment in patients with type 1 diabetes mellitus (T1DM). However, correct calibration of peripheral BP waveforms is important to accurately estimate central BP. We examined differences in central BP estimated by radial artery tonometry depending on which brachial BP (SBP/DBP vs. MAP/DBP) is used for calibration of the radial waveforms, for the first time in T1DM. A cross-sectional study in T1DM patients without known cardiovascular disease. Radial artery BP waveforms were acquired using applanation tonometry ( SphygmoCor ) for the estimation of central SBP, central pulse pressure (PP) and central augmentation pressure, using either brachial SBP/DBP or MAP/DBP for the calibration of the radial pressure waveforms. Fifty-four patients (age: 46 ± 9.5 years; T1DM duration: 27 ± 8.8 years) were evaluated. Central BP parameters were significantly higher when brachial MAP/DBP-calibration was used compared with brachial SBP/DBP-calibration (7.5 ± 5.04, 7.5 ± 5.04 and 1.5 ± 1.36 mmHg higher central SBP, central PP and central augmentation pressure, respectively, P < 0.001). In patients with T1DM, there are significant differences in central BP values estimated with radial artery tonometry, depending on the method used for calibration of the radial waveforms. Brachial MAP/DBP-calibration resulted in consistently higher central BP as compared to using brachial SBP/DBP, leading to patient re-stratification. Hence, the accuracy of noninvasive estimation of central BP by radial tonometry is dependent on calibration approach, and this problem must be resolved in validation studies using an invasive reference standard to determine which method best estimates true central BP.

Accuracy Difference of Noninvasive Blood Pressure Measurements by Sex and Height

Women are at higher risk of cardiovascular events than men with similar blood pressure (BP). Whether this discrepancy in risk is associated with the accuracy of brachial cuff BP measurements is unknown. To examine the difference in brachial cuff BP accuracy in men and women compared with invasively measured aortic BP and to evaluate whether noninvasive central BP estimation varies with sex. This cross-sectional study enrolled 500 participants without severe aortic stenosis or atrial fibrillation from January 1 to December 31, 2019, who were undergoing nonurgent coronary angiography at a tertiary care academic hospital. Simultaneous measurements of invasive aortic BP and noninvasive BP. Sex differences in accuracy were determined by calculating the mean difference between the noninvasive measurements (brachial and noninvasive central BP) and the invasive aortic BP (reference). Linear regression and mediation analyses were performed to identify mediators between sex and brachial cuff accuracy. This study included 500 participants (145 female [29%] and 355 male [71%]; 471 [94%] White; mean [SD] age, 66 [10] years). Baseline characteristics were similar for both sexes apart from body habitus. Despite similar brachial cuff systolic BP (SBP) (mean [SD], 124.5 [17.7] mm Hg in women vs 124.4 [16.4] in men; P = .97), invasive aortic SBP was higher in women (mean [SD], 130.9 [21.7] in women vs 124.7 [20.1] mm Hg in men; P < .001). The brachial cuff was relatively accurate compared with invasive aortic SBP estimation in men (mean [SD] difference, -0.3 [11.7] mm Hg) but not in women (mean [SD] difference, -6.5 [12.1] mm Hg). Noninvasive central SBP (calibrated for mean and diastolic BP) was more accurate in women (mean [SD] difference, 0.6 [15.3] mm Hg) than in men (mean [SD] difference, 8.3 [14.2] mm Hg). This association of sex with accuracy was mostly mediated by height (3.4 mm Hg; 95% CI, 1.1-5.6 mm Hg; 55% mediation). In this cross-sectional study, women had higher true aortic SBP than men with similar brachial cuff SBP, an association that was mostly mediated by a shorter stature. This difference in BP measurement may lead to unrecognized undertreatment of women and could partly explain why women are at greater risk for cardiovascular diseases for a given brachial cuff BP than men. These findings may justify the need to study sex-specific BP targets or integration of sex-specific parameters in BP estimation algorithms.

CENTRAL BLOOD PRESSURE ESTIMATION IN TYPE 1 DIABETES: IMPACT OF PERIPHERAL BLOOD PRESSURE CALIBRATION APPROACH

Objective: Pulse wave analysis (PWA) of peripheral arterial pressure waveforms is used for non-invasive estimation of central blood pressure (BP), which can assist in cardiovascular (CV) risk assessment in populations with a high CV burden such as patients with type 1 diabetes (T1DM). However, correct calibration of peripheral BP waveforms is important in order to accurately estimate central BP. The impact of peripheral BP waveform calibration on central BP is not investigated yet in T1DM. Therefore, this study aims first for the first time in a T1DM patient cohort, to examine differences in central BP parameters estimated by PWA of radial BP waveforms, depending on which brachial BP (SBP/DBP vs. DBP/MAP) is used for calibration of the radial BP waveforms. Design and method: Cross-sectional study, in which adult T1DM patients without known CVD were enrolled. Radial artery BP waveforms were acquired using applanation tonometry (SphygmoCorâ) for the estimation of central systolic BP (central SBP), central pulse pressure (central PP) and central augmentation pressure (central AP), using either brachial SBP/DBP or DBP/MAP for calibration of the radial pressure waveforms. Brachial MAP was calculated using a fixed form factor of 40% (MAP = brachial DBP + 0.40 × brachial PP). Results: 54 patients (M/F: 32/22; age: 46 ± 9.5 yrs; T1DM duration: 27 ± 8.8 yrs) were evaluated. All three estimated central BP parameters were significantly higher when brachial DBP/MAP was used compared to SBP/DBP calibration (7.5 ± 5.04 mmHg, 7.5 ± 5.04 mmHg and 1.5 ± 1.36 mmHg higher central SBP, PP and AP, respectively, p &lt; 0.001). Brachial-to-radial SBP amplification was estimated at 10 ± 7.1 mmHg (p &lt; 0.001). Conclusions: This study confirms for the first time that in patients with T1DM there are significant differences in central BP parameters estimated with PWA, depending on the method used for calibration of the radial pressure waveforms. Brachial DBP/MAP calibration resulted in consistently higher central BP parameters as compared to using SBP/DBP. Hence, it seems that brachial-to-radial SBP amplification is important to take into account in the estimation of central BP parameters also in patients with T1DM.

IMPACT OF POSTURAL POSITION ON DETERMINATION OF AORTIC STIFFNESS AND CENTRAL BLOOD PRESSURE

Objective: Aortic stiffness is associated with increased central pulse pressure and cardiovascular disease and mortality. It is generally performed by determination of carotid-femoral pulse wave velocity (PWV) in a supine position. Two alternative approaches have been developed to estimate aortic stiffness, namely brachial pulse waveform analysis (Mobil-O-Graph) and finger-to-toe PWV by photoplethysmography (pOpmeter). These devices make it possible to assess and estimate aortic stiffness conveniently in different positions. However, it remains unclear if the values obtained are independent of the position at the time of measurement. Therefore, the aim of the present study is to determine the extent of postural changes on pulse wave velocity and central blood pressure estimation using pOpmetre and Mobil-O-Graph devices in a group of healthy controls. Design and method: Central blood pressure and PWV were assessed in 20 healthy subjects using both Mobil-O-Graph (PWV-M) and pOpmetre (PWV-pop) in three positions: supine position in bed, supine position in medical sampling chair and a sitting position. Central systolic blood pressure (SBP) was determined by calibration of brachial systolic and diastolic blood pressures (C1 calibration) by both methods (SBP-M and SBP-pop). Results: In the supine position in bed, PWV-M and PWV-pop were similar (5.5 ± 1.0 vs 5.4 ± 1.3 m/s, P = NS). In the supine position in a sampling chair, PWV-M decreased slightly (5.3 ± 1.0 m/s, P = 0.04 vs supine in bed), while PWV-pop increased significantly (5.9 ± 1.5 m/s, P = 0.04 vs supine in bed). However, in the sitting position, while PWV-M was not statistically different from the supine position (5.5 ± 1.0 m/s, P = NS), PWV-pop increased very significantly (9.2 ± 1.7 m/s, P &lt; 0.001). Central blood pressure estimation remained similar for SBP-M (110.2 ± 10.3 vs 106.9 ± 10.5 vs 108.8 ± 11.1 mmHg, P = NS) and for SBP-pop (107.7 ± 10.4 vs 110.3 ± 9.6 vs 109.5 ± 9.9 mmHg, P = NS). Conclusions: These preliminary results tell us that postural position has little impact on the determination of aortic stiffness by the approach using brachial pulse wave analysis. However, finger-to-toe PWV increases remarkably with changes in position, possibly offering to explore the relationship between hydrostatic pressure and arterial stiffness as a dynamic test.

CENTRAL BLOOD PRESSURE MEASUREMENT IN CHILDREN AND ADOLESCENTS: SYSTEMATIC REVIEW

Objective: Central aortic blood pressure (BP) has attracted the researchers interest due to its potential to improving cardiovascular risk stratification. We reviewed the published data on central BP in children and adolescents excluding those with chronic heart, lung or kidney disease, congenital anomaly or syndrome, malignancy, and acute illness. Design and method: A systematic review of literature based on PubMed database was conducted by two independent researchers up to January 2021 in accordance with the PRISMA guidelines. Additional studies were identified from the reference lists of relevant articles. Results: A total of 56 eligible articles were identified (Table). The available literature advocates a positive association between male gender, age, height, African-American descent, preterm birth, hypertension and diabetes with central BP, whereas the association of birth weight and physical exercise with central BP was inverse. Regarding the relationship of central BP with indices of preclinical target organ damage, 11 studies showed a positive association with pulse wave velocity, 7 with left ventricular mass index, 5 with carotid intima-media thickness, and 4 with augmentation index. Two studies reported an inverse association with the equivalent of the central retinal artery. The studies testing non-invasive techniques for central BP estimation reported that they approach the invasive technique with adequate accuracy, with crucial impact of the calibration method. Tonometry remains the most studied non-invasive measurement method, followed by oscillometry. Two studies provided normalcy values using the oscillometric method. The evidence on 24-hour ambulatory central BP is limited. Conclusions: The evidence on central BP measurement in youth is limited and derived from non-invasive evaluation in static conditions using tonometry. Central BP in children and adolescents seems to be affected by multiple factors and is associated with preclinical target organ damage.

New Method to Estimate Central Systolic Blood Pressure From Peripheral Pressure: A Proof of Concept and Validation Study.

Objective: The non-invasive estimation of central systolic blood pressure (cSBP) is increasingly performed using new devices based on various pulse acquisition techniques and mathematical analyses. These devices are most often calibrated assuming that mean (MBP) and diastolic (DBP) BP are essentially unchanged when pressure wave travels from aorta to peripheral artery, an assumption which is evidence-based. We tested a new empirical formula for the direct central blood pressure estimation of cSBP using MBP and DBP only (DCBP = MBP2/DBP).Methods and Results: First, we performed a post-hoc analysis of our prospective invasive high-fidelity aortic pressure database (n = 139, age 49 ± 12 years, 78% men). The cSBP was 146.0 ± 31.1 mmHg. The error between aortic DCBP and cSBP was −0.9 ± 7.4 mmHg, and there was no bias across the cSBP range (82.5–204.0 mmHg). Second, we analyzed 64 patients from two studies of the literature in whom invasive high-fidelity pressures were simultaneously obtained in the aorta and brachial artery. The weighed mean error between brachial DCBP and cSBP was 1.1 mmHg. Finally, 30 intensive care unit patients equipped with fluid-filled catheter in the radial artery were prospectively studied. The cSBP (115.7 ± 18.2 mmHg) was estimated by carotid tonometry. The error between radial DCBP and cSBP was −0.4 ± 5.8 mmHg, and there was no bias across the range.Conclusion: Our study shows that cSBP could be reliably estimated from MBP and DBP only, provided BP measurement errors are minimized. DCBP may have implications for assessing cardiovascular risk associated with cSBP on large BP databases, a point that deserves further studies.

Estimating Central Blood Pressure From a Single Peripheral Pressure Measurement

Abstract This paper presents a set of criteria used to identify the parameters describing a tube-load model of the arterial system to estimate central blood pressure (BP). The criteria are generalizable to accommodate for inter- and intra-subject variability encountered in the ICU. The proposed single measurement transfer function (SMTF) requires only a single peripheral pressure measurement, commonly available in the ICU, for central pressure estimation, removing the need for an additional measurement of pulse transit time, common to other central BP estimation models. The method was tested using data from six (6) porcine experiments where septic shock was induced and subsequent treatment was performed. Systolic pressure (SP), pulse pressure (PP) and root-mean-squared (RMSE) errors relative to invasive measurements of aortic pressure were used to assess accuracy. The SMTF method produced mean errors ≤5mmHg across all metrics with 84.4, 88.7 and 63.2% of SP, PP, and RMSE, respectively, within this bound of measured central pressure. Peripheral BP accuracy was also assessed as it is commonly used as a surrogate for central BP in clinical settings. Finally, two alternate methods utilizing the same model equations with additional inputs, one using the measured pulse transit time and the other minimizing the RMSE with measured aortic pressure, were implemented to compare the SMTF accuracy to best case outputs given the model equations.

Learning-Based Model for Central Blood Pressure Estimation using Feature Extracted from ECG and PPG signals.

Pre-detection of hypertension mostly considers the measurement of Brachial Artery Blood Pressure (BABP). Although being a standard vital, it is still considered a poor alternative for Central Blood Pressure (CBP). However, CBP is measured invasively during the process of cardiac catheterization (Cath). Though cuff-less techniques to estimate BABP are widely employed, CBP estimation has not been explored yet. Moreover, to best of our knowledge intermittent CBP estimation has not been proposed earlier. Therefore, we present a cuff-less and beat-by-beat CBP estimation technique using linear regression analysis on features extracted from continuous Electrocardiogram (ECG) and Photoplethysmograph (PPG) signals. Unlike for BABP estimation, 30 supplementary features to conventional pulse transit time such as ST-interval, Psystolic peak interval, etc., were extracted to enhance CBP accuracy. This extraction was done using Haar wavelet along with modulus maxima. Feature selection has been done using the wrapper technique and reduced using principal component analysis. Segregation of each beat was achieved with the help of constraints developed based on iteration and backtracing. This model estimates Systolic CBP with a validation error of 0.109±2.37 mmHg and Diastolic CBP with an error of 0.031±2.102 mmHg for 33 Cath lab patients.

Blind Estimation of Central Blood Pressure Using Least-Squares with Mean Matching and Box Constraints.

Central aortic blood pressure (CABP) is a very-well recognized source of information to asses the cardiovascular system conditions. However, the clinical measurement protocol of this pulse wave is very intrusive and burdensome as it requires expert staff and complicated invasive settings. On the other hand, the measurement of peripheral blood pressure is much more straightforward and easy-to-get non-invasively. Several mathematical tools have been employed in the past few decades to reconstruct CABP waveforms from distorted peripheral pressure signals. More specifically, the cross-relation approach together with the widely used least-squares method, are shown to be effective as a way to estimate CABP waves. In this paper, we propose an improved cross-relation method that leverages the values of the diastolic and systolic pressures as box constraints. In addition, a mean-matching criterion is introduced to relax the need for the input and output mean values to be strictly equal. Using the proposed method, the root mean squared error is reduced by approximately 20% while the computational complexity is not significantly increased.

Aortic Calcification Affects Noninvasive Estimates of Central Blood Pressure in Patients with Severe Chronic Kidney Disease

Background: Central blood pressure (BP) assessed noninvasively considerably underestimates true invasively measured aortic BP in chronic kidney disease (CKD) patients. The difference between the estimated and the true aortic BP increases with decreasing estimated glomerular filtration rates (eGFR). The present study investigated whether aortic calcification affects noninvasive estimates of central BP. Methods: Twenty-four patients with CKD stage 4–5 undergoing coronary angiography and an aortic computed tomography scan were included (63% males, age [mean ± SD ] 53 ± 11 years, and eGFR 9 ± 5 mL/min/1.73 m²). Invasive aortic BP was measured through the angiography catheter, while non-invasive central BP was obtained using radial artery tonometry with a SphygmoCor® device. The Agatston calcium score (CS) in the aorta was quantified on CT scans using the CS on CT scans. Results: The invasive aortic systolic BP (SBP) was 152 ± 23 mm Hg, while the estimated central SBP was 133 ± 20 mm Hg. Ten patients had a CS of 0 in the aorta, while 14 patients had a CS >0 in the aorta. The estimated central SBP was lower than the invasive aortic SBP in patients with aortic calcification compared to patients without (mean difference 8 mm Hg, 95% CI 0.3–16; p = 0.04). The brachial SBP was lower than the aortic SBP in patients with aortic calcification compared to patients without (mean difference 10 mm Hg, 95% CI 2–19; p = 0.02). Conclusion: In patients with advanced CKD the presence of aortic calcification is associated with a higher difference between invasively measured central aortic BP and non-invasive estimates of central BP as compared to patients without calcifications.

DIFFERENCES IN BIOMARKERS LEVELS AND BRACHIAL AND CENTRAL BLOOD PRESSURE DURING THE ACUTE PHASE OF STROKE BETWEEN LACUNAR AND OTHER ISCHEMIC STROKES SUBTYPES

Objective: We aimed to evaluate the differences in biomarker levels and brachial and central blood pressure estimates during the acute and subacute phase of stroke, between lacunar infarcts and other ischemic stroke subtypes. Design and method: Patients > 18 years old, with a first episode of ischemic stroke, admitted to our institution between July 2015 and July 2017 were consecutively included. Subjects with Rankin > 2 and patients with history of previous heart failure were excluded. Blood pressure (BP) was measured at admission and during the acute phase of stroke. Determination of proBNP, urinary albumin excretion (UAE) and an echocardiographic study were performed in all subjects. The aortic pulse wave velocity (aPWV) and 24 h brachial and central BP (24h-ABPM) were measured by means of Mobil-O-Graph device during the subacute phase of stroke. Results: 71 subjects with a first episode of ischemic stroke were included, mean age: 64.7 ± 13.9 years, 62% men: 22 lacunar stroke (31%), and 49 cases (69%) with non lacunar ischemic stroke. The levels of proBNP were significantly lower in patients with lacunar stroke as compared as atherothrombotic and cardioembolic stroke (median: 36, 277 and 274 pg/mL, respectively; p = 0.009). After adjusting for age, patients with lacunar stroke had significantly higher levels of BP in the emergency department: systolic BP 173 ± 37 vs 153 ± 28 mm Hg respectively; p = 0.006, diastolic BP: 97 ± 21 vs 86 ± 16 mm Hg; p = 0.035, and during the acute phase of stroke: systolic BP 142 ± 19 vs 128 ± 16 mm Hg; p = 0.002; diastolic BP: 79 ± 12 and 73 ± 12 mm Hg respectively; p = 0.025. Regarding 24h-ABPM, patients with lacunar stroke showed higher values of daytime pulse pressure, daytime brachial systolic BP, daytime brachial diastolic BP and central BP estimates, after adjusting for age. No significant differences were observed in target organ damage between the different ischemic stroke subtypes. Conclusions: Patients with a first episode of lacunar stroke had lower levels of proBNP and higher BP levels during acute and subacute phase of stroke, suggesting a closer relationship with hypertension.

Comparison of laboratory and ambulatory measures of central blood pressure and pulse wave reflection: hitting the target or missing the mark?

Prior studies demonstrating clinical significance of noninvasive estimates of central blood pressure (BP) and pulse wave reflection have relied primarily on discrete resting measures. The aim of this study was to compare central BP and pulse wave reflection measures sampled during a single resting laboratory visit against those obtained under ambulatory conditions. The secondary aim was to investigate the reproducibility of ambulatory central BP and pulse wave reflection measurements. Forty healthy participants (21 males; 24 ± 3 years) completed three measurements of brachial artery pulse wave analysis (Oscar 2 with SphygmoCor Inside) in the laboratory followed by 24 hours of ambulatory monitoring. Seventeen participants repeated the 24-hour ambulatory monitoring visit after at least 1 week. Ambulatory measures were divided into daytime (9 AM–9 PM), nighttime (1 AM–6 AM), and 24-hour periods. Compared with laboratory measurements, central systolic BP, augmentation pressure, and augmentation index (with and without heart rate normalization) were higher (all P < .01) during daytime and 24-hour periods but lower during the nighttime period (all P < .001). The drop in nighttime brachial systolic BP was larger than central systolic pressure (Δ −20 ± 6 vs. −15 ± 6 mm Hg; P < .0001). Repeat ambulatory measurements of central BP and pulse wave reflection displayed good-to-excellent intraclass correlation coefficients (r = 0.58–0.86; all P < .01), although measures of pulse wave reflection had higher coefficients of variation (14%–41%). The results highlight absolute differences in central BP and pulse wave reflection between discrete laboratory and ambulatory conditions. The use of ambulatory measures of central BP and pulse wave reflection warrant further investigation for clinical prognostic value.

Cuff-Based Oscillometric Central and Brachial Blood Pressures Obtained Through ABPM are Similarly Associated with Renal Organ Damage in Arterial Hypertension

Background/Aims: Central blood pressure (BP) has been suggested to be a better estimator of hypertension-associated risks. We aimed to evaluate the association of 24-hour central BP, in comparison with 24-hour peripheral BP, with the presence of renal organ damage in hypertensive patients. Methods: Brachial and central (calculated by an oscillometric system through brachial pulse wave analysis) office BP and ambulatory BP monitoring (ABPM) data and aortic pulse wave velocity (PWV) were measured in 208 hypertensive patients. Renal organ damage was evaluated by means of the albumin to creatinine ratio and the estimated glomerular filtration rate. Results: Fifty-four patients (25.9%) were affected by renal organ damage, displaying either microalbuminuria (urinary albumin excretion ≥30 mg/g creatinine) or an estimated glomerular filtration rate (eGFR) <60 ml/min/1.73 m². Compared to those without renal abnormalities, hypertensive patients with kidney damage had higher values of office brachial systolic BP (SBP) and pulse pressure (PP), and 24-h, daytime, and nighttime central and brachial SBP and PP. They also had a blunted nocturnal decrease in both central and brachial BP, and higher values of aortic PWV. After adjustment for age, gender, and antihypertensive treatment, only ABPM-derived BP estimates (both central and brachial) showed significant associations with the presence of renal damage. Odds ratios for central BP estimates were not significantly higher than those obtained for brachial BP. Conclusion: Compared with peripheral ABPM, cuff-based oscillometric central ABPM does not show a closer association with presence of renal organ damage in hypertensive patients. More studies, however, need to be done to better identify the role of central BP in clinical practice.

A Feasibility Study of Wearable Central Blood-Pressure Measurement System

A noninvasive estimation of central blood-pressure is required by the researchers or the medical practitioners in the cardiovascular treatment. In this study, first of all, a cardiovascular simulator based on the electrical circuits is described based on the model based approach and then, the representation of aorta model as a pressure transfer function is shown. This representation accelerates the simulator and then, makes it possible to estimate the central blood-pressure from a wearable gouge measurement in a real-time way. The system consisting of a main station, gateways and wearable blood-pressure gauges using one-board microcomputer is actually implemented. The functions and performances of the system are experimentally evaluated and the obtained results show the feasibility of central blood-pressure estimation and the localization of some examinees having wearable gauges with the practical accuracy and speed.