Digital Pulse Wave Analysis Research Articles

Low-Frequency Vibration Facilitates Post-Exercise Cardiovascular Autonomic Recovery

It is important to use short breaks to accelerate post-exercise recovery in sports. Previous studies have revealed that vibration can reduce post-exercise muscle soreness. However, there is still high heterogeneity in the effects of vibration on cardiovascular autonomic activities, and most studies to date have focused on high-frequency vibration. This study aimed to investigate the effect of low-frequency lower-body vibration (LBV) on post-exercise changes in heart rate variability and peripheral arterial tone. Ten men and 9 women aged 20 to 25 were recruited for this study. Each subject visited the testing room three times with at least 2 days in between. Each time, the subject received one of the three different vibration frequencies (0, 5, and 15 Hz) in a random order in the sitting position for 10 minutes. LBV was performed immediately after a static standing (control) test and 3-min-step test. Heart rate variability and digital volume pulse wave were recorded during the vibration phase (V1: vibration 0-5 minutes; V2: 6-10 minutes) and the recovery phase (Rc1: recovery phase 11-15 minutes; Rc2: 16-20 minutes). The result of digital pulse wave analysis showed that the reflection index (RI) under 15 Hz decreased during V1. Heart rate of the 15-Hz group also decreased during Rc1 and Rc2. According to the analysis of heart rate variability, low-frequency power/high-frequency power (LF/HF) decreased and normalized high-frequency power (nHF) increased during V2, Rc1 and Rc2 under 15 Hz and, during Rc2 under 5 Hz vibration. This study confirmed that the application of low-frequency LBV after exercise can reduce peripheral vascular tone, accelerate heart rate recovery, decrease cardiac sympathetic nerve activity, and promote parasympathetic nerve activity. The effect was more pronounced at 15 Hz than at 5 Hz. The findings provide a method to accelerate cardiovascular autonomic recovery after exercise.

Arterial stiffness in normal pregnancy as assessed by digital pulse wave analysis by photoplethysmography - A longitudinal study.

It might in the future be valuable to screen for increased maternal arterial stiffness, i.e. low compliance, since it is associated with development of hypertensive complications in pregnancy. Digital pulse wave analysis (DPA) is an easy and manageable method for arterial stiffness assessment. We aimed to investigate gestational influence on DPA variables longitudinally, and establish gestational age-adjusted reference values in normal pregnancy. DPA measurements were performed longitudinally up to five times during pregnancy in 139 healthy women. Reference curves for DPA variables aging index (AI), b/a and d/a relative to gestational age were calculated with linear and polynomial mixed-effects models, and the influences of age and parity investigated with analysis of variance and analysis of covariance. A p < 0.05 was regarded significant. All DPA variables were significantly associated with GA with best fit for a quadratic model. Arterial compliance peaked in the late second trimester. Age and parity independently influenced DPA variables but did not change the associations with gestational age. DPA reflects longitudinal changes in arterial compliance in normal pregnancy but individual variance of DPA changes were greater than the influence of GA. Normal distributions of AI, b/a and d/a at 14-24 weeks are presented, but it remains to show whether these can be used to detect pathological hemodynamic alterations in pregnancy.

Arterial stiffness during controlled ovarian hyperstimulation and early pregnancy in women exposed to assisted reproduction

ABSTRACTIntroduction: Female sex hormones have vasorelaxing effects in non-pregnant and pregnant women. We aimed to investigate the effect of controlled ovarian hyperstimulation (COH) for in vitro fertilization (IVF), and early pregnancy, on arterial stiffness as assessed by digital pulse wave analysis (DPA), hypothesizing reduced arterial stiffness as an effect of increased estrogen levels.Material and methods: A total of 68 women undergoing IVF were examined with DPA before conception and during IVF treatment with COH and embryo transfer (ET), and in gestational week seven in 19 women who became pregnant. Heart rate (HR), mean arterial pressure (MAP) and the DPA variables cardiac ejection elasticity index (EEI), b/a, dicrotic index (DI), d/a and aging index (AI) were measured.Results: HR was significantly increased at all measuring points (p ≤ 0.003) but MAP only at ET (p 0.007). DPA variables representing large arteries (EEI, b/a) and peripheral arteries (DI, but not d/a), and the global variable AI, indicated increased arterial stiffness at ET compared with baseline (p ≤ 0.035). No DPA variable was significantly changed at pregnancy measurements compared to baseline.Conclusion: During COH for IVF treatment, DPA showed no changes in arterial stiffness during the follicular phase or in early pregnancy, but increased arterial stiffness in central and peripheral arteries in the early luteal phase. The result suggests a hormonal hemodynamic activation counteracting the effects of estrogen.

Can flavonoid-rich chocolate modulate arterial elasticity and pathological uterine artery Doppler blood flow in pregnant women? A pilot study

Introduction: Dark chocolate has shown beneficial effects on cardiovascular health and might also modulate hypertensive complications in pregnancy and uteroplacental blood flow. Increased uteroplacental resistance is associated with systemic arterial stiffness. We aimed to investigate the short-term effect of flavonoid-rich chocolate on arterial stiffness and Doppler blood flow velocimetry indexes in pregnant women with compromised uteroplacental blood flow.Methods: Doppler blood flow velocimetry and digital pulse wave analysis (DPA) were performed in 25 women pregnant in the second and third trimesters with uterine artery (UtA) score (UAS) 3–4, before and after 3 days of ingestion of chocolate with high flavonoid and antioxidant contents. UtA pulsatility index (PI), UtA diastolic notching, UAS (semiquantitative measure of PI and notching combined), and umbilical artery PI were calculated, and DPA variables representing central and peripheral maternal arteries were recorded.Results: Mean UtA PI (p = .049) and UAS (p = .025) significantly decreased after chocolate consumption. There were no significant changes in UtA diastolic notching or any DPA indexes of arterial stiffness/vascular tone.Conclusion: Chocolate may have beneficial effects on the uteroplacental circulation, but in this pilot study, we could not demonstrate effects on arterial vascular tone as assessed by DPA.

Association between uterine artery Doppler blood flow changes and arterial wall elasticity in pregnant women

Introduction: Uterine artery (UtA) Doppler velocimetry changes and increased arterial stiffness are associated with preeclampsia. We aimed to investigate the relation between UtA velocimetry changes and arterial stiffness in pregnant women.Methods: Doppler velocimetry and photoplethysmographic digital pulse wave analysis (DPA) were performed in 173 pregnant women in the second or the third trimester, where UtA Doppler pulsatility index (PI), diastolic notching, and UtA score (UAS) combining notching and high PI were calculated. DPA stiffness parameters representing large arteries were ejection elasticity index (EEI) and b/a, small arteries dicrotic index (DI) and d/a, and global stiffness the aging index (AI).Results: One hundred and thirty women had normal Doppler and 43 had diastolic notching, of whom nine had high PI. DI indicated increased stiffness in small arteries when notching was present (p = 0.044) and showed a significant but weak correlation to UAS (p = 0.025, tau 0.12). EEI and b/a indicated increased large artery stiffness (p ≤0.014), d/a small artery stiffness (p = 0.023), and AI a systemic stiffness (p = 0.040) when high PI.Conclusion: High UtA PI was associated with increased systemic arterial stiffness, whereas notching was related to increased stiffness in small arteries only. This indicates pathophysiological differences between the two Doppler parameters.

Blood pressure changes after catheter-based renal denervation are related to reductions in total peripheral resistance.

Renal denervation (RDN) can reduce sympathetic activity and blood pressure (BP) in patients with uncontrolled hypertension. The exact mechanisms by which RDN results in BP reductions are yet not fully established. This study investigated the effects of RDN on office BP, 24-h ambulatory BP, noninvasive 10-min beat-to-beat digital pulse wave analysis, total peripheral resistance (TPR), cardiac output, and plasma renin and aldosterone serum concentrations in 30 patients with resistant hypertension. Adherence to antihypertensive drugs was assessed by liquid chromatography high-resolution tandem mass spectrometry analysis in plasma and urine at baseline and at 6 month. RDN significantly reduced office BP, beat-to-beat BP, and 24-h ambulatory BP by 19/6 (P = 0.021/P = 0.012), 12/7 (P = 0.005/P = 0.005), and 10/5 mmHg (P = 0.001/P = 0.049) at 6 months, respectively. TPR decreased from 1696 to 1377 dyn × s/cm (-19%; P = 0.027). This reduction was not associated with significant changes in cardiac output. The changes in office, ambulatory, and beat-to-beat BP correlated with the reductions of TPR. Adherence to antihypertensive treatment remained unchanged during the study period (84.7% at baseline, 83.6% at 6 months, P = 0.782). RDN reduced office BP, beat-to-beat BP, and 24-h ambulatory BP in patients with resistant hypertension after 6 months. The BP changes were associated with reductions in peripheral resistance, whereas cardiac output, plasma renin, and aldosterone levels remained unchanged. The observed effects were not explained by an increased intake of antihypertensive medications.

Digital Photoplethysmography for Assessment of Arterial Stiffness: Repeatability and Comparison with Applanation Tonometry.

IntroductionArterial stiffness is an independent risk factor for cardiovascular morbidity and can be assessed by applanation tonometry by measuring pulse wave velocity (PWV) and augmentation index (AIX) by pressure pulse wave analysis (PWA). As an inexpensive and operator independent alternative, photoelectric plethysmography (PPG) has been introduced with analysis of the digital volume pulse wave (DPA) and its second derivatives of wave reflections.ObjectiveThe objective was to investigate the repeatability of arterial stiffness parameters measured by digital pulse wave analysis (DPA) and the associations to applanation tonometry parameters.Methods and Results112 pregnant and non-pregnant individuals of different ages and genders were examined with SphygmoCor arterial wall tonometry and Meridian DPA finger photoplethysmography. Coefficients of repeatability, Bland-Altman plots, intraclass correlation coefficients and correlations to heart rate (HR) and body height were calculated for DPA variables, and the DPA variables were compared to tonometry variables left ventricular ejection time (LVET), PWV and AIX. No DPA variable showed any systematic measurement error or excellent repeatability, but dicrotic index (DI), dicrotic dilatation index (DDI), cardiac ejection elasticity index (EEI), aging index (AI) and second derivatives of the crude pulse wave curve, b/a and e/a, showed good repeatability. Overall, the correlations to AIX were better than to PWV, with correlations coefficients >0.70 for EEI, AI and b/a. Considering the level of repeatability and the correlations to tonometry, the overall best DPA parameters were EEI, AI and b/a. The two pansystolic time parameters, ejection time compensated (ETc) by DPA and LVET by tonometry, showed a significant but weak correlation.ConclusionFor estimation of the LV function, ETc, EEI and b/a are suitable, for large artery stiffness EEI, and for small arteries DI and DDI. The only global parameter, AI, showed a high repeatability and the overall best correlations with AIX and PWV.

P16 Plasma hydrogen sulfide (H2S) levels in CKD patients

Animal models of chronic kidney disease (CKD) [1] and CKD patients [2] have reduced plasma hydrogen sulfide (H2S) concentrations. H2S inhibits phosphate-induced calcification and osteoblastic differentiation of vascular smooth muscle cells [2] , which may suggest it has a role in arterial calcification. The aim of the present study was to measure plasma H2S concentrations in CKD patients and investigate whether these measurement correlate with markers of vascular calcification or arterial stiffness. 54 Hypertensive non-diabetic patients (⩾70 years) with CKD stages 3 and 4 (n = 29), and hypertensive non-CKD matched controls (n = 25) were used in this study. Pulse wave velocity (PWV) and analysis were assessed by applanation tonometry, central hemodynamics by continuous digital pulse wave analysis, and vascular calcification (VC) by superficial femoral artery CT. Plasma hydrogen sulfide was determined following conversion to methylene blue using the zinc–dimethyl phenylenediamine trapping method described by Stipanuk and Beck [3] . Data was analysed by Spearman correlation. Plasma concentrations of H2S were not different between CKD (range 0.34 to 9.99 μM, mean 3.27 ± 0.40 (SEM)) and non-CKD patients (range 0.45 to 10.93 μM, mean 2.99 ± 0.58 (SEM)). Plasma H2S measurements did not correlate with vascular calcification scores, total peripheral resistance or pulse wave velocity. However, within the CKD patients only (n = 28), a negative correlation was observed between plasma H2S and pulse wave velocity (r=-0.36, P = 0.0545). A negative correlation was also found between plasma H2S and plasma parathyroid hormone levels (r=-0.3, P = 0.0379), but not between plasma H2S and plasma vitamin D levels. There was a trend for a positive correlation between plasma corrected calcium levels and plasma H2S (r = 0.26, P = 0.0620) but not with plasma phosphate levels. This reached significance in the CKD patient only group for corrected calcium levels (r = 0.47, P = 0.0101). This pilot data did not find a correlation between vascular calcification in a population of elderly CKD and non-CKD patients, but did observe a relationship between arterial stiffness and H2S in the CKD patients. Correlations between plasma H2S levels and plasma calcium and parathyroid hormone do suggest a role for H2S in the regulation of calcium levels within the body, which warrants further research.

Comparison of photoplethysmographic and arterial tonometry-derived indices of arterial stiffness

Arterial tonometry is a method to assess arterial stiffness and has become a valuable tool in the stratification of cardiovascular risk. The arterial tonometry-derived augmentation index (AIx) is a marker of arterial stiffness and an independent predictor of mortality. As the AIx is relatively cumbersome to obtain, simpler methods such as analysis of pulse waves obtained by digital photoplethysmography have been proposed to estimate arterial stiffness. The objective of this study is to compare the usefulness of the stiffness index (SI) derived from digital photoplethysmography and the AIx derived from radial tonometry for stratification of cardiovascular risk. We studied 83 subjects with a heterogeneous cardiovascular risk profile and determined the ability of the two devices to differentiate subjects with low from subjects with high cardiovascular risk estimated by the Europe (EU)-heart score. Failure rate in both devices was similar (3.6%). AIx and SI were modestly correlated (r=0.48, P<0.001) and both indexes correlated with the EU-score (r=0.54, P<0.001) and (r=0.56, P<0.001), respectively. Both devices discriminated accurately between subjects with high cardiovascular risk (upper tertile of the EU-score) and low cardiovascular risk (lower tertile). However, only the SI differentiated significantly between subjects with intermediate risk (middle tertile) and high risk (upper tertile). Compared with the AIx, assessment of the SI derived by digital photoplethysmography is simple and possibly yields an advantage in risk stratification of subjects with intermediate and high cardiovascular risk. Therefore, digital pulse wave analysis may be a valuable tool to estimate arterial stiffness in large clinical studies.

The Impact of Antihypertensive Drug Therapy on Endotoxemia in Elderly Patients with Chronic Kidney Disease

Endotoxin (ET) is recognized to cause adverse effects on cardiovascular (CV) structure. Circulatory translocation of gut bacterial ET is described in heart failure. Chronic kidney disease (CKD) is common in older people and aggressive BP control is the cornerstone of management. We therefore studied ET after improvement of the overall CV milieu with introduction of optimized antihypertensive therapy (AHT). We recruited 40 hypertensive nondiabetic patients (≥70 years) with CKD stages 3 and 4 and hypertensive non-CKD matched controls. Assessment was performed after complete AHT washout and repeated after AHT reintroduction to target BP 130/80 mmHg. Pulse wave velocity (PWV) and analysis were assessed by applanation tonometry, central hemodynamics by continuous digital pulse wave analysis, vascular calcification (VC) by superficial femoral artery CT, and serum ET by Limulus Amebocyte assay. Mean age was 76 ± 5 years, estimated GFR (eGFR) (CKD group) was 40 ± 14 ml/min per 1.73 m(2), and achieved BP was 128/69 mmHg. Washout ET was 0.042 ± 0.011 EU/ml and was independent of renal function, gender, age, BP, VC, arterial stiffness, and high-sensitivity C-reactive protein. ET significantly decreased with AHT (to 0.020 ± 0.028 EU/ml; P < 0.001) and was associated with eGFR (R = -0.38; P = 0.02), arterial wave reflection (Augmentation Index R = -0.42; P = 0.01), and degree of tonic vasodilatation (total peripheral resistance R = -0.37; P = 0.03), but not VC, PWV, gender, age, BP, or high-sensitivity C-reactive protein. Elderly patients with hypertension have elevated serum ET. Improvement of their CV status with optimized AHT is associated with a significant reduction in endotoxemia. Further investigation of the potential pathophysiological mechanisms linking CV disease and CKD with this previously unappreciated effect of AHT appears warranted.

Effects of peritoneal dialysis fluid biocompatibility on baroreflex sensitivity

Conventional low biocompatibility peritoneal dialysis (PD) fluid composition has been driven by manufacturing expediency and cost limitations. PD is associated with significant acute changes in cardiovascular functional parameters, at least in part influenced by fluid composition. Short-term control of blood pressure (BP) is under control of the baroreflex arc. The aim of this study was to investigate the effects of PD fluid biocompatibility on baroreflex sensitivity (BRS). We studied 10 non-diabetic established continuous ambulatory PD patients, in a randomized crossover trial comparing conventional and biocompatible PD fluids. Systemic hemodynamics were continuously monitored using digital pulse-wave analysis. Plasma glucose and insulin were assessed during treatment with both 1.36% and 3.86% glucose-containing fluids. BRS was calculated offline from continuous BP and interbeat interval data. BRS was significantly higher with conventional PD fluid during both 1.36% (P<0.001) and 3.86% (P<0.001) dwells. Systolic BP was higher; heart rate, stroke volume, and cardiac output were lower; and total peripheral resistance increased during exposure to either fluid. There were significant differences between fluids with respect to the magnitude of these responses. Plasma glucose and insulin concentrations, and ultrafiltration volumes were significantly higher during the 3.86% dwell than the 1.36% dwell, but there were no differences between standard and biocompatible fluids. We have demonstrated for the first time that PD fluid biocompatibility rapidly affects BRS. These changes occur against a background of cardiovascular variability, hyperinsulinemia, and hyperglycemia. Further research is needed to explore the mechanism and, more importantly, the consequences of these findings.