Hour-to-hour and week-to-week variability and reproducibility of wave reflection indices derived by aortic pulse wave analysis: implications for studies with repeated measurements

Central Systolic Blood Pressure as a Risk Factor for Accelerated Progression of Arterial Stiffness

AIMS

In the arterial tree, a pressure gradient of the systolic blood pressure (SBP) is observed from the center to the periphery, with the pressure being higher in the periphery because of pressure wave reflection. However, this gradient is attenuated, with elevation of the central SBP (cSBP), in cases with abnormal pressure wave reflection in the arterial tree. It remains unclear if increase of the cSBP might be an independent risk factor for accelerated progression of arterial stiffness. We conducted this prospective observational study using latent growth curve model (LGCM) analyses to examine if elevated cSBP might be an independent risk factor for accelerated progression of the arterial stiffness in middle-aged Japanese men.

METHODS

In this 9-year prospective observational study, we analyzed the data of 3862 middle-aged Japanese men (43±10years old) without cerebrocardiovascular disease at the study baseline who had undergone repeated annual measurements of the brachial-ankle pulse wave velocity (baPWV) and cSBP, as represented by the second peak of the radial pressure waveform (SBP2) in radial pressure waveform analysis.

RESULTS

During the follow-up period (6.3±2.5years), significant increases of both the baPWV and SBP2 were observed in all the subjects. Analysis using the LGCM confirmed that the SBP2, a marker of the cSBP (B=0.260, P＜0.001), was a significant determinant of the slope of the annual changes of the baPWV during the study period.

CONCLUSIONS

Our finding may appear to confirm elevated cSBP as an independent risk factor for accelerated progression of the arterial stiffness in middle-aged Japanese men.

Association of pulse wave velocity and pressure wave reflection with the ankle-brachial pressure index in Japanese men not suffering from peripheral artery disease

BACKGROUND AND AIMS

We examined the cross-sectional and longitudinal association of arterial stiffness and pressure wave reflection with the ankle-brachial pressure index (ABI) in middle-aged Japanese subjects free of peripheral artery disease (PAD).

METHODS

ABI, brachial-ankle pulse wave velocity (baPWV) and radial augmentation index (rAI) were measured annually during the 9-year observation period in 3066 men (42 ± 9 years old) with ABI ≥1.00 at baseline of the study period, and not taking any antihypertensive medication.

RESULTS

In the cross-sectional assessments, mediation analysis demonstrated that baPWV showed both direct and indirect (via the rAI) associations with ABI, and rAI showed both direct and indirect (via the heart-arm difference of systolic blood pressure) associations with the ankle-arm difference of systolic blood pressure, both at study baseline and end of study period. Mixed model linear regression analysis of the repeated-measurement data obtained over the 9-year observation period demonstrated that annual increase of baPWV (estimate = 0.73 × 10^-4, p < 0.01) and rAI (estimate = 0.33 × 10^-3, <0.01) was associated with ABI. When baPWV and rAI were entered into the same model, only baPWV showed a significant longitudinal association with ABI.

CONCLUSION

In middle-aged Japanese men free of PAD, arterial stiffness may contribute to ABI directly and via pressure wave reflection. Pressure wave reflection may contribute to ABI directly and, at least in part, via attenuation of peripheral pulse pressure amplification.

Increased aortic augmentation index is associated with reduced exercise capacity after heart transplantation

OBJECTIVE

Exercise capacity is often reduced after heart transplantation. We aimed to investigate the association between aortic stiffness and exercise capacity after heart transplantation.

METHODS

We retrospectively analyzed the data of patients who underwent a cardiopulmonary exercise test and central hemodynamic measurements over 1 year following heart transplantation, from Janary 2011 to June 2018.

RESULTS

A total of 54 patients (mean age, 49 years; 72% men) were analyzed. The median peak oxygen uptake level was 21.1 ml/kg per min at a median time of 13 months after heart transplantation. In univariate linear regression, recipient age, pulmonary arterial pressure, pulmonary capillary wedge pressure, hemoglobin level, estimated glomerular filtration rate, aortic augmentation index, and pulse wave velocity were significant predictors for peak oxygen uptake level. After adjustment for other confounding variables, heart rate-corrected aortic augmentation index was a significant predictor for peak oxygen uptake (β = -0.141, 95% confidence interval, -0.263 to -0.058, P = 0.003).

CONCLUSION

In the present study, increased aortic augmentation index was associated with reduced exercise capacity after heart transplantation. Therefore, this simple measurement of aortic stiffness should be periodically used for the evaluation of exercise capacity after heart transplantation.

Quantitative Comparison of the Performance of Piezoresistive, Piezoelectric, Acceleration, and Optical Pulse Wave Sensors

The accurate measurement of the arterial pulse wave is beneficial to clinical health assessment and is important for the effective diagnosis of many types of cardiovascular disease. A variety of sensors have been developed for the non-invasive detection of these waves, but the type of sensor has an impact on the measurement results. Therefore, it is necessary to compare and analyze the signals obtained under a range of conditions using various pulse sensors to aid in making an informed choice of the appropriate type. From the available types we have selected four: a piezoresistive strain gauge sensor (PESG) and a piezoelectric Millar tonometer (the former with the ability to measure contact force), a circular film acceleration sensor, and an optical reflection sensor. Pulse wave signals were recorded from the left radial, carotid, femoral, and digital arteries of 60 subjects using these four sensors. Their performance was evaluated by analyzing their susceptibilities to external factors (contact force, measuring site, and ambient light intensity) and by comparing their stability and reproducibility. Under medium contact force, the peak-to-peak amplitude of the signals was higher than that at high and low force levels and the variability of signal waveform was small. The optical sensor was susceptible to ambient light. Analysis of the intra-class correlation coefficients (ICCs) of the pulse wave parameters showed that the tonometer and accelerometer had good stability (ICC > 0.80), and the PESG and optical sensor had moderate stability (0.46 < ICC < 0.86). Intra-observer analysis showed that the tonometer and accelerometer had good reproducibility (ICC > 0.75) and the PESG and optical sensor had moderate reproducibility (0.42 < ICC < 0.91). Inter-observer analysis demonstrated that the accelerometer had good reproducibility (ICC > 0.85) and the three other sensors had moderate reproducibility (0.52 < ICC < 0.96). We conclude that the type of sensor and measurement site affect pulse wave characteristics and the careful selection of appropriate sensor and measurement site are required according to the research and clinical need. Moreover, the influence of external factors such as contact pressure and ambient light should be fully taken into account.

Influences on the Functional Behavior of Great Arteries during Orthostasis

Background

Arterial compliance reduction has been associated with aging and hypertension in supine position. However, the dynamic effects of orthostatism on aortic distensibility has not been defined.

Objective

We sought to determine the orthostatic influence and the interference of age, blood pressure (BP) and heart rate (HR) on the great arteries during gravitational stress.

Methods

Ninety-three healthy volunteers (age 42 ± 16 years). Carotid-femoral pulse wave velocity (PWV) assumed as aortic stiffness was assessed in supine position (basal phase), during tilt test (TT) (orthostatic phase) and after return to supine position (recovery phase). Simultaneously with PWV acquisition, measures of BP and HR rate were recorded.

Results

PWV during TT increased significantly compared to the basal and recovery phases (11.7 ± 2.5 m/s vs. 10.1 ± 2.3 m/s and 9.5 ± 2.0 m/s). Systolic BP (r = 0.55, r = 0.46 and r = 0.39) and age (r = 0.59, r = 0.63 and r = 0.39) correlated with PWV in all phases. The significance level for all tests was established as α = 0.05.

Conclusion

We conclude that there is a permanent increase in PWV during orthostatic position that was returned to basal level at the recovery phase. This dynamic pattern of PWV response, during postural changes, can be explained by an increase in hydrostatic pressure at the level of abdominal aorta which with smaller radius and an increased elastic modulus, propagates the pulse in a faster way. Considering that it could increase central pulse reflection during the orthostatic position, we speculate that this mechanism may play a role in the overall adaptation of humans to gravitational stress.

Telomere Length and Vascular Phenotypes in a Population-Based Cohort of Children and Midlife Adults

Background Telomere length has been inversely associated with cardiovascular disease in adulthood, but its relationship to preclinical cardiovascular phenotypes across the life course remains unclear. We investigated associations of telomere length with vascular structure and function in children and midlife adults. Methods and Results Population-based cross-sectional CheckPoint (Child Health CheckPoint) study of 11- to 12-year-old children and their parents, nested within the LSAC (Longitudinal Study of Australian Children). Telomere length (telomeric genomic DNA [T]/β-globin single-copy gene [S] [T/S ratio]) was measured by quantitative polymerase chain reaction from blood-derived genomic DNA. Vascular structure was assessed by carotid intima-media thickness, and vascular function was assessed by carotid-femoral pulse-wave velocity and carotid elasticity. Mean (SD) T/S ratio was 1.09 (0.55) in children (n=1206; 51% girls) and 0.81 (0.38) in adults (n=1343; 87% women). Linear regression models, adjusted for potential confounders, revealed no evidence of an association between T/S ratio and carotid intima-media thickness, carotid-femoral pulse-wave velocity, or carotid elasticity in children. In adults, longer telomeres were associated with greater carotid elasticity (0.14% per 10-mm Hg higher per unit of T/S ratio; 95% CI, 0.04%-0.2%; P=0.007), but not carotid intima-media thickness (-0.9 μm; 95% CI, -14 to 13 μm; P=0.9) or carotid-femoral pulse-wave velocity (-0.10 m/s; 95% CI, -0.3 to 0.07 m/s; P=0.2). In logistic regression analysis, telomere length did not predict poorer vascular measures at either age. Conclusions In midlife adults, but not children, there was some evidence that telomere length was associated with vascular elasticity but not thickness. Associations between telomere length and cardiovascular phenotypes may become more evident in later life, with advancing pathological changes.

A randomized controlled trial to assess the central hemodynamic response to exercise in patients with transient ischaemic attack and minor stroke

Early exercise engagement elicits meaningful changes in peripheral blood pressure in patients diagnosed with transient ischaemic attack (TIA) or minor stroke. However, central hemodynamic markers may provide clinicians with important diagnostic and prognostic information beyond that provided by peripheral blood pressure readings. The purpose of this single-centre, randomized, parallel-group clinical trial was to determine the effect of a 12-week aerobic exercise intervention on central and peripheral hemodynamic variables in patients with TIA or minor stroke. In this study, 47 participants (66±10 years) completed a baseline assessment, which involved the measurement of central and peripheral hemodynamic parameters, undertaken in the morning, in a fasted state. Participants were randomized to either a 12-week exercise or control group on completion of the baseline assessment. An identical follow-up assessment was completed post intervention. Central hemodynamic variables were assessed using an oscillometric device at both assessments. Analysis of covariance demonstrated a significant interaction for central and peripheral blood pressure and augmentation index (all P<0.05; η_p².09–.11), with the exercise group presenting lower values than the control group post intervention (118±17 vs 132±28 mm Hg for central blood pressure; 125±19 vs 138±28 mm Hg for peripheral blood pressure; 104±49 vs 115±67% for augmentation index). The present study demonstrates that participation in an exercise program soon after stroke/TIA diagnosis may elicit significant beneficial changes to a patient's central systolic blood pressure and augmentation index. This may positively impact upon the treatment strategies implemented by clinicians in the care of patients with TIA and minor stroke.

Reliability of oscillometric central blood pressure responses to submaximal exercise

BACKGROUND

Central blood pressure responses to exercise may provide clinicians with a superior diagnostic and prognostic tool. However, to be of value in a clinical setting these assessments must be simple to conduct and reliable.

OBJECTIVE

Using oscillometric pulse wave analysis (PWA), determine the upper limit for between-day reliability of central SBP (cSBP) and central pressure augmentation (AIx) responses to three progressive stages of submaximal exercise in a cohort of young, healthy participants.

METHODS

Fifteen healthy males [25.8 years (SD 5.7), 23.9 kg/m (SD 2.5)] were tested on three different mornings in a fasted state, separated by a maximum of 14 days. Central hemodynamic variables were assessed on the left upper arm. Participants underwent three progressive stages of submaximal cycling at 50 W (low), 100 W (moderate) and 150 W (moderate-hard).

RESULTS

During low and moderate-intensity exercise the intra-class correlation coefficient (ICC) values for cSBP (0.79-0.80) and AIx (0.81-0.85) indicated excellent reliability (ICC > 0.75). For the moderate-hard intensity AIx could not be computed, and the ICC for cSBP was adequate (0.72).

CONCLUSION

Findings from this study suggest that, at least in a young, healthy cohort, oscillometric PWA can be used to reliably assess central blood pressure measurements during exercise, up to a moderate intensity. Although further work is required to verify these findings in clinical cohorts, these measurements may potentially provide clinicians with a practical option for obtaining important hemodynamic information beyond that provided by resting peripheral blood pressure.

Reliability of oscillometric central blood pressure and wave reflection readings: effects of posture and fasting

OBJECTIVE

Oscillometric pulse wave analysis devices have recently emerged, presenting suitable options for investigating central hemodynamic properties in clinical practice. This study sought to examine whether the between-day reliability of central SBP (cSBP) and systemic arterial wave reflection (augmentation index, AIx) readings exceed the criterion for acceptable reliability or are affected by posture (supine and seated) and fasting state.

METHODS

Twenty healthy adults (50% female, 27.9 years, 24.2 kg/m) were tested on six different mornings: 3 days fasted and 3 days nonfasted. On each occasion, participants were tested in supine and seated postures. Oscillometric pressure waveforms were recorded on left upper arm.

RESULTS

For cSBP, there was nonsignificant main effect for fasting state (P = 0.819) but there was a main effect for posture (P = 0.002). Conversely, for AIx, there was nonsignificant main effect for posture (P = 0.537) but there was a large main effect for fasting state (P = < 0.001). The criterion intraclass correlation coefficient value of 0.75 was exceeded for both variables when participants were assessed under the combined supine-fasted condition. For cSBP, the reliability coefficient was lowest (best) when supine fasted (6.8 mmHg) and greatest (worst) when seated nonfasted (8.6 mmHg). For AIx, the reliability coefficient was lower for the supine (11.4-11.7%) compared with the seated (14.0-15.2%) posture.

CONCLUSION

Findings from this study suggest that oscillometric assessments of central hemodynamic variables exceed the criterion for acceptable reliability and are most reliable when participants are evaluated while supine and fasted.

Reliability of oscillometric central hemodynamic responses to an orthostatic challenge

BACKGROUND

Monitoring central hemodynamic responses to an orthostatic challenge may provide important insight into autonomic nervous system function. Oscillometric pulse wave analysis devices have recently emerged, presenting clinically viable options for investigating central hemodynamic properties. The purpose of the current study was to determine whether oscillometric pulse wave analysis can be used to reliably (between-day) assess central blood pressure and central pressure augmentation (augmentation index) responses to a 5 min orthostatic challenge (modified tilt-table).

METHODS

Twenty healthy adults (26.4 y (SD 5.2), 55% F, 24.7 kg/m(2) (SD 3.8)) were tested on 3 different mornings in the fasted state, separated by a maximum of 7 days. Central hemodynamic variables were assessed on the left arm using an oscillometric device.

RESULTS

Repeated measures analysis of variance indicated a significant main effect of the modified tilt-table for all central hemodynamic variables (P < 0.001). In response to the tilt, central diastolic pressure increased by 4.5 mmHg (CI: 2.6, 6.4), central systolic blood pressure increased by 2.3 (CI: 4.4, 0.16) mmHg, and augmentation index decreased by an absolute - 5.3%, (CI: -2.7, -7.9%). The intra-class correlation coefficient values for central diastolic pressure (0.83-0.86), central systolic blood pressure (0.80-0.87) and AIx (0.79-0.82) were above the 0.75 criterion in both the supine and tilted positions, indicating excellent between-day reliability.

CONCLUSION

Central hemodynamic responses to an orthostatic challenge can be assessed with acceptable between-day reliability using oscillometric pulse wave analysis.

Weight reduction and aortic stiffness in obese children and adolescents: a 1-year follow-up study

Little is known about the effect of weight reduction on aortic stiffness and especially so in the young. The present study investigates whether weight reduction influences aortic stiffness in obese children and adolescents. Carotid-femoral pulse wave velocity (cfPWV) and augmentation index at heart rate 75 (AIx@HR75) were measured in 72 obese patients aged 10-18 years at baseline and after 1-year of lifestyle intervention (follow-up). We found that although the degree of obesity decreased (Δbody mass index z-score: -0.24±0.45, P<0.0001), cfPWV was higher at follow-up (ΔcfPWV: 0.27±0.47 m s(-1), P<0.0001), which was explained by the increase in age (β=0.12 ms(-1)  per year, 95% confidence interval (CI) 0.07-0.17, P<0.0001) and partly by changes in mean arterial pressure and heart rate. Changes in cfPWV were not related to changes in obesity measures. No significant change was found in AIx@HR75 (ΔAIx@HR75: 2.10±9.73%, P=0.072), but changes in AIx@HR75 were related to changes in abdominal fat (Δwaist/height ratio: β=50.3, 95% CI 6.7-94.0, P=0.02) and changes in total body fat percent by dual energy X-ray absorptiometry scan (Δtotal body fat (%): β=0.7, 95% CI 0.1-1.3, P=0.02) when adjusted for gender and relevant baseline confounders. In conclusion, no clear effect of weight reduction was found on aortic stiffness, although changes in AIx@HR75 were associated with changes in both abdominal fat and total body fat percent. The higher cfPWV at follow-up was related to the older age.

Validation of oscillometric pulse wave analysis measurements in children

BACKGROUND

Pulse wave analysis (PWA) has emerged as a noninvasive, valid, reliable, and widely used technique to investigate central blood pressures and systemic arterial wave reflection (augmentation index). The gold-standard technique is tonometry, but this technique can be challenging, especially when used on children. The purpose of this study was to validate oscillometric PWA for use in children.

METHODS

Fifty-seven healthy children were recruited for participation. Central blood pressures and peripheral augmentation index (pAIx) were measured objectively using oscillometric (Pulsecor R7) and tonometric (SphygmaCor) devices. All measurements were made during the same visit under standardized conditions between the hours of 8 am and 10 am in the fasted state.

RESULTS

Tonometric measurements were unsuccessful on 1 child. Comparisons were made on 56 children (mean age = 9.8±1.0 y; 57% male). A very strong relationship was found between devices for central systolic (r = 0.94; P < 0.001), diastolic (r = 0.99; P < 0.001) and mean (r = 0.96; P < 0.001) blood pressures. However, Bland-Altman analysis indicated a bias toward greater systolic blood pressures with the oscillometric monitor (mean difference = 4.5mm Hg; 95% confidence interval (CI) = -5.16 to -3.89). A good relationship was found for pAIx (r = 0.71; P < 0.001); the mean difference between devices was -1.70% (95% CI = -4.47% to 1.08%), which is not significantly different from zero.

CONCLUSIONS

Findings from this study suggest that oscillometric PWA provides valid measures of central blood pressure and arterial wave reflection in children aged 8-10 years.

Should the augmentation index be normalized to heart rate?

Pulse wave analysis(PWA) is widely used to investigate systemic arterial stiffness. The augmentation index(AIx), the primary outcome derived from PWA, is influenced by the mean arterial pressure(MAP), age, gender and heart rate(HR). Gender- and age-specific reference values have been devised, and it is recommended that the MAP be used as a statistical covariate. The AIx is also commonly statistically adjusted to a HR of 75 b·min(-1); however, this approach may be physiologically and statistically inappropriate. First, there appears to be an important physiological chronic interaction between HR and arterial stiffness. Second, the method used to correct to HR assumes that the relationship with AIx is uniform across populations. A more appropriate practice may be to include HR as an independent predictor or covariate; this approach is particularly recommended for longitudinal studies, in which changes in HR may help to explain changes in arterial stiffness.

The Vicorder device compared with SphygmoCor in the assessment of carotid-femoral pulse wave velocity in patients with peripheral arterial disease

To assess the reliability and reproducibility of the Vicorder's carotid-femoral pulse wave velocity (cfPWV) measurements in patients with peripheral arterial disease (PAD) and to compare between cfPWV measurements obtained using the Vicorder with those obtained using the SphygmoCor device as a reference. Some 30 patients with PAD (23 men, mean age 64.9±7.5) underwent cfPWV measurement twice by a single investigator during one visit using the Vicorder and the SphygmoCor according to the manufacturer's instructions. Intra-rater reproducibility for each device was assessed using intraclass correlation coefficients (ICC) and Bland-Altman method. The latter was also used to compare between the two devices. The mean difference (s.d.) between repeated measurements was 0.03±0.92 m s(-1), P=0.85 and 0.01±0.54 m s(-1), P=0.91 for the SphygmoCor and Vicorder, respectively. Measurements of cfPWV were highly reproducible using both devices (ICC=0.94 and 0.92, for the Vicorder and SphygmoCor, respectively). Limits of Agreement using the Bland-Altman method were -1.07 to 1.09 m s(-1) and -1.79 to 1.85 m s(-1) for the Vicorder and the SphygmoCor, respectively. Bland-Altman plots indicated that 90% of the cfPWV measurements using the Vicorder and 93% of the measurements using the SphygmoCor fell within two s.d.s of the mean difference. Transit time (TT) differed significantly between the two devices (mean difference 30±9.2 m s, P<0.001), with the Vicorder recording higher values. Nevertheless, the two devices recorded nearly similar cfPWV measurements (mean difference -0.69±1.6 m s(-1), P=0.02) with 97% of cfPWV values falling within two s.d. values of the mean difference on Bland-Altman plot. Both devices generated highly reproducible cfPWV measurements in patients with PAD and were in good agreement when compared with each other. However, the discrepancy in TT between the two devices lead to the Vicorder producing lower values of cfPWV at high values produced by the SphygmoCor.

Assessments of arterial stiffness and endothelial function using pulse wave analysis

Conventionally, the assessments of endothelial function and arterial stiffness require different sets of equipment, making the inclusion of both tests impractical for clinical and epidemiological studies. Pulse wave analysis (PWA) provides useful information regarding the mechanical properties of the arterial tree and can also be used to assess endothelial function. PWA is a simple, valid, reliable, and inexpensive technique, offering great clinical and epidemiological potential. The current paper will outline how to measure arterial stiffness and endothelial function using this technique and include discussion of validity and reliability.

Assessment of differences between repeated pulse wave velocity measurements in terms of 'bias' in the extrapolated cardiovascular risk and the classification of aortic stiffness: is a single PWV measurement enough?

Currently, there is no recommendation regarding the minimum number of pulse wave velocity (PWV) measurements to optimize individual's cardiovascular risk (CVR) stratification. The aim of this study was to examine differences between three single consecutive and averaged PWV measurements in terms of the extrapolated CVR and the classification of aortic stiffness as normal. In 60 subjects who referred for CVR assessment, three repeated measurements of blood pressure (BP), heart rate and PWV were performed. The reproducibility was evaluated by the intraclass correlation coefficient (ICC) and mean±s.d. of differences. The absolute differences between single and averaged PWV measurements were classified as: ≤0.25, 0.26-0.49, 0.50-0.99 and ≥1 m s(-1). A difference ≥0.5 m s(-1) (corresponding to 7.5% change in CVR, meta-analysis data from >12 000 subjects) was considered as clinically meaningful; PWV values (single or averaged) were classified as normal according to respective age-corrected normal values (European Network data). Kappa statistic was used to evaluate the agreement between classifications. PWV for the first, second and third measurement was 7.0±1.9, 6.9±1.9, 6.9±2.0 m s(-1), respectively (P=0.319); BP and heart rate did not vary significantly. A good reproducibility between single measurements was observed (ICC>0.94, s.d. ranged between 0.43 and 0.64 m s(-1)). A high percent with difference ≥0.5 m s(-1) was observed between: any pair of the three single PWV measurements (26.6-38.3%); the first or second single measurement and the average of the first and second (18.3%); any single measurement and the average of three measurements (10-20%). In only up to 5% a difference ≥0.5 m s(-1) was observed between the average of three and the average of any two PWV measurements. There was no significant agreement regarding PWV classification as normal between: the first or second measurement and the averaged PWV values. There was significant agreement in classification made by the average of the first two and the average of three PWV measurements (κ=0.85, P<0.001). Even when high reproducibility in PWV measurement is succeeded single measurements provide quite variable results in terms of the extrapolated CVR and the classification of aortic stiffness as normal. The average of two PWV measurements provides similar results with the average of three.

Acute effects of 5-methyltetrahydrofolate on endothelial function and asymmetric dimethylarginine in patients with chronic heart failure

BACKGROUND AND AIMS

Folic acid enhances endothelial function in vascular disease states but its effects in chronic heart failure (CHF) are largely unknown. We studied the acute effects of i.v. methyltetrahydrofolate (5MTHF), the active metabolite of folic acid, on endothelial function and asymmetric dimethylarginine (ADMA) in CHF patients.

METHODS AND RESULTS

Twenty two CHF patients and 22 controls received one of the following three-step infusions (1h per each step) in a randomized, parallel group, placebo-control study: (1) active treatment (saline, 5MTHF, and 5MTHF+the endothelial nitric oxide inhibitor N(G)-monomethyl l-arginine, LNMMA); or (2) placebo (salinex3). Endothelium-dependent vasodilatation was assessed by pulse-wave analysis (salbutamol-mediated changes in augmentation index, AIx). 5MTHF did not exert any significant effects on endothelium-dependent vasodilatation both in controls [DeltaAIx post-salbutamol baseline -7.6% (-24.8/-4.1) vs. 5MTHF -5.5% (-16.7/-3.6), medians and interquartile range, and CHF patients [-1.8% (-17.3/+1.3) vs. -2.4% (-3.8/-1.2)]. However, a significant reduction in ADMA concentrations was observed in both groups [controls baseline 0.68micromol/L (0.64/0.77) vs. 5MTHF 0.65 (0.57/0.74); CHF baseline 0.76 (0.63/0.82) vs. 5MTHF 0.69 (0.66/0.71), P=0.05 for both vs. baseline and placebo. These effects persisted during co-infusion with LNMMA.

CONCLUSION

5MTHF did not affect endothelial function but significantly reduced serum ADMA concentrations both in CHF patients and controls. This suggests a direct effect of 5MTHF on ADMA metabolism.

Prediction of cardiovascular events and all-cause mortality with central haemodynamics: a systematic review and meta-analysis

AIMS

To calculate robust quantitative estimates on the predictive value of central pressures and derived central haemodynamic indices for cardiovascular (CV) outcomes and all-cause mortality by meta-analysis of longitudinal studies.

METHODS AND RESULTS

We meta-analysed 11 longitudinal studies that had employed measures of central haemodynamics and had followed 5648 subjects for a mean follow-up of 45 months. The age- and risk-factor-adjusted pooled relative risk (RR) of total CV events was 1.088 (95% CI 1.040-1.139) for a 10 mmHg increase of central systolic pressure, 1.137 (95% CI 1.063-1.215) for a 10 mmHg increase of central pulse pressure (PP), and 1.318 (95% CI 1.093-1.588) for a 10% absolute increase of central augmentation index (AIx). Furthermore, we found that a 10% increase of central AIx was associated with a RR of 1.384 (95% CI 1.192-1.606) for all-cause mortality. When compared with brachial PP, central PP was associated with marginally but not significantly higher RR of clinical events (P = 0.057).

CONCLUSION

Central haemodynamic indexes are independent predictors of future CV events and all-cause mortality. Augmentation index predicts clinical events independently of peripheral pressures, while central PP has a marginally but not significantly (P = 0.057) better predictive ability when compared with peripheral PP.

Arterial Wave Reflections During the Menstrual Cycle of Healthy Women

Increased wave reflection is an independent factor associated with cardiovascular diseases, risk, and mortality. The influence of the menstrual cycle on wave reflections and particularly on the reproducibility of their measurement has never been examined. The aim of the present study was to examine the reproducibility and variability of wave reflection indices in premenopausal healthy women during their menstrual cycle. Thirty-two women were examined at 3 phases of their menstrual cycle: days 1 to 2 (menstrual phase), days 6 to 14 (late follicular), and days 4 to 7 after ovulation (early luteal phase). Applanation tonometry of the radial artery and aortic pulse wave analysis were performed for the calculation of augmentation pressure, augmentation index, and timing of reflected waves. Reproducibility of these measures was evaluated by intraclass correlation coefficient and Bland-Altman analysis, whereas ANOVA was performed to assess their variability during the menstrual cycle. The SD of augmentation index differences between repeated measurements within the menstrual cycle ranged from 7.6% to 9.9%. Bland-Altman analysis indicated no evidence of systemic bias and no trend for the reproducibility of measurements to vary with their underlying mean value. Intraclass correlation coefficient indicated a moderate reproducibility of augmentation index and augmentation pressure (>0.80) and a rather low reproducibility for timing of reflected waves (0.43). Mean augmentation pressure, augmentation index, and timing of reflected waves did not vary significantly during the menstrual cycle (ANOVA). Measurement of wave reflections at the same phase of the menstrual cycle or statistical adjustment could be suggested for optimal study design and data interpretation.

Role of the augmentation index in hypertension

Recent studies have revealed the clinical usefulness of central blood pressure (BP) as an index of risk for cardiovascular disease. The arterial pulse waveform is the sum of the forward pressure wave generated by left ventricular ejection and a backward propagating wave that is subsequently reflected from the peripheral site, and the time point at which these forward and backward propagating waves merge and the amplitude of the reflected (backward) wave affect the level of central BP. The augmentation index (AIx) has been proposed as a measure of the wave reflection, and its clinical usefulness has also been evaluated. In the process, the non-linear relationship between age and AIx, the prognostic value of AIx, and the various effects of antihypertensive drugs on AIx have been shown. However, the clinical usefulness of AIx has not been established, and several questions about its use remain. Future studies will be needed to address these questions, and may contribute to important changes in the management of cardiovascular disease. In this review, we present recent findings on the AIx and discuss the role of this parameter in clinical practice.

Pulse wave analysis is a reproducible technique for measuring central blood pressure during hemodynamic perturbations induced by exercise

BACKGROUND

Central blood pressure (BP) and markers of wave reflection (augmentation index; AIx) measured by radial tonometry have prognostic value independent from brachial BP. The measurement of the central waveform is increasingly used during altered hemodynamics, including exercise, but reliability of the test has not been reported under changed loading conditions. This study aimed to test the technique's reproducibility during major hemodynamic perturbations induced by exercise.

METHODS

Radial waveforms were recorded (SphygmoCor) in 28 healthy subjects (aged 53 +/- 11 years) at rest, during submaximal exercise (cycling at 50, 60, and 70% of maximal age-predicted heart rate (HR)) and immediately after maximal treadmill exercise on two occasions separated by 9 +/- 5 days. Data were compared between testing days. Waveforms were calibrated with brachial BP measured using a mercury sphygmomanometer. Pulse pressure amplification (PPAmp) was defined as the ratio of brachial to central pulse pressure.

RESULTS

There was very good reproducibility between visits at all exercise intensities for all waveform measures, including AIx, central pulse pressure, and PPAmp (intraclass correlations at 50% exercise were 0.93, 0.89, and 0.89, respectively; P < 0.001). The mean difference between tests at this intensity was 0 +/- 4% for AIx, 4 +/- 6 mm Hg for central pulse pressure, and -0.02 +/- 0.09 for PPAmp. There were no significant differences between visits for HR, PPAmp, or AIx at rest or with exercise (P > 0.05 for all).

CONCLUSIONS

Radial tonometry is a reproducible technique for measurement of central waveform indices during perturbations induced by exercise. It should, therefore, be suitable for use in intervention studies in which hemodynamics are altered.

Analysis of short-term reproducibility of arterial vasoreactivity by pulse-wave analysis after pharmacological challenge

1. Pulse-wave analysis (PWA) is an established method to assess arterial wave reflections and arterial vasoreactivity in humans. A high short-term reproducibility of baseline augmentation index (AIx) has been reported. However, the short-term reproducibility of AIx changes following pharmacological challenge with either inhaled salbutamol (endothelium-dependent vasodilatation) or sublingual glyceryl trinitrate (GTN; endothelium-independent vasodilatation), using appropriate statistical methods, is largely unknown. 2. Baseline AIx and GTN- and salbutamol-mediated changes in AIx (all corrected for a heart rate of 75 b.p.m.) were measured on two separate occasions, 1 h apart, in 22 healthy controls (mean (+/-SD) age 52.0 +/- 13.4 years) and 11 elderly patients with chronic heart failure (CHF; 73.1 +/- 8.7 years). Reproducibility was assessed by measuring intraclass correlation coefficients (ICC), coefficients of variation (CV) and Bland-Altman plots. 3. Baseline AIx showed good short-term reproducibility with high ICC in both the control and CHF groups (0.90 and 0.87, respectively). In contrast, in the control and CHF groups, the ICC of GTN- (0.58 and 0.17, respectively) and salbutamol-mediated (0.18 and 0.04, respectively) changes in AIx were substantially low. The CV was relatively low for baseline AIx in control and CHF groups (25.0 and 22.5%, respectively), but not for GTN- (22.3 and 59.8%, respectively) or salbutamol-mediated (45.1 and 184.0%, respectively) changes in AIx. Bland-Altman analysis revealed poor reproducibility, with limits of agreement beyond either +15% or -15% for changes in AIx after GTN and salbutamol for both control and CHF groups. The changes in blood pressure and heart rate following pharmacological challenge were similar between the two measurements. 4. The poor reproducibility of changes in AIx following pharmacological challenge questions the use of this method in acute studies.

Acute changes in vascular function among welders exposed to metal-rich particulate matter

BACKGROUND

Although welding fume exposure is associated with adverse cardiovascular outcomes, the mechanisms remain unclear. To investigate the role of vascular function, we assessed levels of the augmentation index (a correlate of arterial stiffness) after short-term exposure to welding-derived fine particulate matter (PM2.5).

METHODS

In a panel study, we monitored 26 male welders over 24 hours on a welding day (n = 25), a non-welding day (n = 15), or both (n = 14). Augmentation index (expressed as a percent) was obtained in the morning before exposure (baseline) and after exposure in the afternoon and the following morning. Personal PM2.5 exposure was measured over 6 hours of welding or an equivalent non-welding period. We used linear mixed models adjusting for baseline augmentation index, smoking, age, and time to evaluate the effects of welding (binary) and PM2.5 (continuous) on augmentation index levels. We also assessed modification by welding exposure the day before monitoring (binary).

RESULTS

Welding was associated with a 2.8% increase in afternoon augmentation index (95% confidence interval = -1.4 to 7.0) and a 2.4% decrease (-6.9 to 2.2) in next-morning augmentation index. Additional exposure the day prior to monitoring was associated with a greater afternoon increase (5.1%; 0.8 to 9.5). Using PM2.5 concentration, a positive association was observed in the afternoon and an inverse association the next morning; results differed by previous day's welding status after excluding outliers.

CONCLUSIONS

Subsequent to welding fume exposure, there is an increase in afternoon augmentation index and a decrease in next-morning augmentation index, with greater changes after consecutive days of exposure. These results suggest that exposure to the PM2.5 component of welding fume elicits acute adverse vascular responses.

Effects of pre- vs. intra-dialysis folic acid on arterial wave reflections and endothelial function in patients with end-stage renal disease

BACKGROUND

Haemodialysis (HD) is associated with the acute loss through the dialysis membrane of biochemical factors either enhancing [folic acid (F)] or impairing [asymmetric dimethylarginine (ADMA)] arterial function. Changes in these opposing factors might explain the absence of significant modifications in arterial function during HD. We speculated that intra-HD, instead of pre-HD, F administration would provide beneficial effects on arterial wave reflections and endothelial function by preventing HD-induced F loss.

METHODS

Arterial wave reflections [augmentation index (AIx), pulse-wave analysis], endothelium-dependent vasodilation (salbutamol-mediated changes in AIx) and plasma concentrations of F and ADMA were measured pre-HD and end-HD in 10 patients (age 67.7 +/- 10.3 years). Each subject received F 5 mg either pre-HD or intra-HD in two separate studies 2-4 weeks apart, in an open-label randomized cross-over trial.

RESULTS

Pre-HD F administration did not prevent significant reductions in F during HD (end-HD vs. pre-HD, -865 +/- 465 nmol l(-1), P < 0.001), but no significant changes in AIx (+1.4 +/- 5.7%) or salbutamol-mediated AIx modifications (+0.4 +/- 5.5%) were observed. By contrast, intra-HD F administration was associated with significant increases in F (+298 +/- 283 nmol l(-1), P = 0.010) and a significant reduction of AIx (-4.7 +/- 7.2%, P = 0.013), but no effects on salbutamol-mediated AIx changes (+1.5 +/- 4.4%). There was a trend towards greater HD-induced reductions in plasma ADMA concentrations with intra-HD F administration (P = 0.066).

CONCLUSIONS

Intra-HD F administration reduces arterial wave reflections but not endothelial function during HD. Given the prognostic significance of arterial wave reflections in HD patients, the timing of F administration is important in the design of interventional trials in this cohort.

Acute combined effects of olive oil and wine on pressure wave reflections: another beneficial influence of the Mediterranean diet antioxidants?

OBJECTIVES

Combined consumption of olive oil and wine is common in the Mediterranean diet, but there are no data concerning their synergistic haemodynamic response. We sought to determine the combined postprandial effects of wine and olive oil on wave reflections and central haemodynamics.

METHODS

Fifteen healthy subjects consumed four standard meals on different days, containing 50 g of olive oil and 250 ml of wine, in a randomized cross-over study design. Two types of wine [red (R) and white (W)] and two types of olive oil [green (G) and refined (O) (rich and poor in antioxidants, respectively)] were used in all possible combinations (RO, RG, WO and WG). Applanation tonometry and aortic pulse wave analysis were performed when fasting and 1, 2 and 3 h postprandially. A second group of 15 healthy individuals matched for age, gender and body mass index served as the control group.

RESULTS

All meals decreased AIx (RO and RG, P < 0.001; WO, P = 0.007; and WG, P = 0.039). The AIx reduction after RG, RO, WO and WG was significantly different from the respective AIx response of the control group. No difference was observed in the reduction of AIx between sessions, but a significantly earlier peak decrease in AIx, as well as a more prolonged decreasing effect, was observed after RG and RO consumption compared to WO and WG. Central systolic and diastolic pressures were diminished after all four combinations of wine and olive oil (P < 0.05).

CONCLUSIONS

Combined consumption of wine and olive oil provided beneficial postprandial effects on haemodynamics. These findings reveal an additional favourable effect of components of the Mediterranean diet on haemodynamics in the postprandial state.