Wave reflection, assessed by use of the ARCSolver Algorithm for pulse wave separation, is reduced under acute µg conditions in parabolic flight

Weightlessness during long-term space flight over 6-12 months leads to complex individual cardiovascular adaptation. The initial central blood volume expansion followed by a loss of plasma volume is accompanied by changes in vascular mechanoreceptor loads and responsive-ness, altered autonomic reflex control of heart rate and blood pressure, and hormonal changes in the long run. Hence, function and structure of the heart and blood vessels may change. Hemodynamic data obtained during short- and long-term space flight may indicate that the adaptation process resembles ageing of the cardiovascular system characterized by decreased diastolic blood pressure, increased central sympathetic nerve traffic and increased arterial pulse wave velocity. Experiments during parabolic flights in supine position suggest, that stroke volume does not change during transitions between µ-g and 1-g. We tested a novel method of pulse wave separation based on simple oscillometric brachial cuff waveform reading to investigate pulse wave reflection during acute weightlessness in healthy subjects. We hypothesized that the wave reflection magnitude (RM) remains unaltered during parabolic flights in supine position

Different associations between beta-blockers and other antihypertensive medication combinations with brachial blood pressure and aortic waveform parameters

BACKGROUND: Comparing the relationships of antihypertensive medications with brachial blood pressure (BP) and aortic waveform parameters may help clinicians to predict the effect on the latter in brachial BP-based antihypertensive therapy. We aimed to make such comparisons with new waveform measures and a wider range of antihypertensive regimens than examined previously. METHODS: Cross-sectional analysis of 2933 adults (61% male; aged 50–84 years): 1637 on antihypertensive treatment and 1296 untreated hypertensives. Sixteen medicine regimens of up to 4 combinations of drugs from 6 antihypertensive classes were analysed. Aortic systolic BP, augmentation index (AIx), excess pressure integral (EPI), backward pressure amplitude (Pb), reflection index (RI) and pulse wave velocity (PWV) were calculated from aortic pressure waveforms derived from suprasystolic brachial measurement. RESULTS: Forest plots of single-drug class comparisons across regimens with the same number of drugs (for between 1- and 3-drug regimens) revealed that AIx, Pb, RI and/or loge(EPI) were higher (maximum difference = 5.6%, 2.2 mm Hg, 0.0192 and 0.13 loge(mm Hg ⋅ s), respectively) with the use of a beta-blocker compared with vasodilators and diuretics, despite no brachial systolic and diastolic BP differences. These differences were reduced (by 34–57%) or eliminated after adjustment for heart rate, and similar effects occurred when controlling for systolic ejection period or diastolic duration. CONCLUSIONS: Beta-blocker effects on brachial BP may overestimate effects on aortic waveform parameters. Compared to other antihypertensives, beta-blockers have weaker associations with wave reflection measures and EPI; this is predominantly due to influences on heart rate

A comparison between left ventricular ejection time measurement methods during physiological changes induced by simulated microgravity

New findings: What is the central question of this study? First, we validated easy-to-use oscillometric left ventricular ejection time (LVET) against echocardiographic LVET. Second, we investigated progression of left ventricular ejection time index (LVETI), pre-ejection period index (PEPI), total electromechanical systole index (QS2I) and PEP/LVET ratio during 60 days of head-down tilt (HDT). What is the main finding and its importance? The LVETosci and LVETecho showed good agreement in effect direction. Hence, LVETosci might be useful to evaluate cardiovascular responses during space flight. Moreover, the approach might be useful for individual follow-up of patients with altered ejection times. Furthermore, significant effects of 60 days of HDT were captured by measurements of LVETI, PEPI, QS2I and PEP/LVET ratio. Abstract: Systolic time intervals that are easy to detect might be used as parameters reflecting cardiovascular deconditioning. We compared left ventricular ejection time (LVET) measured via ultrasound Doppler on the left ventricular outflow tract with oscillometrically measured LVET, measured at the brachialis. Furthermore, we assessed the progression of the left ventricular ejection time index (LVETI), the pre-ejection period index (PEPI), the Weissler index (PEP/LVET) and the total electromechanical systole index (QS2I) during prolonged strict head-down tilt (HDT) bed rest, including 16 male and eight female subjects. Simultaneous oscillometric and echocardiographic LVET measurements showed significant correlation (r = 0.53 with P = 0.0084 before bed rest and r = 0.73 with P < 0.05 on the last day of bed rest). The shortening of LVET during HDT bed rest measured with both approaches was highly concordant in their effect direction, with a concordance rate of 0.96. Our results also demonstrated a significant decrease of LVETI (P < 0.0001) and QS2I (P = 0.0992) and a prolongation of PEPI (P = 0.0049) and PEP/LVET (P = 0.0003) during HDT bed rest over 60 days. Four days after bed rest, LVETI recovered completely to its baseline value. Owing to the relationship between shortening of LVETI and heart failure progression, the easy-to-use oscillometric method might not only be a useful way to evaluate the cardiovascular system during space flights, but could also be of high value in a clinical setting

AORTIC VESSEL WALL PROPERTIES DURING 60 DAYS STRICT HEAD DOWN TILT BEDREST - PRELIMINARY RESULTS OF AGBRESA

Background Changes in large artery properties including increased arterial compliance and increased carotid artery stiffness have been described after space flight. Altered vascular structure, which heralds cardiovascular risk, and reversible changes in vascular function could contribute to the response. Compared with previous studies, which did not reproduce these findings, AGBRESA applied strict -6° head-down bedrest (HDT) mimicking chronic cephalad fluid shifts in space. In this study, we assessed aortic vessel wall properties using state-of-the art imaging methods and pulse wave analysis and tested for possible protective effects of artificial gravity training. Material and Methods We present preliminary data from 12 healthy subjects (8 men, 4 women) obtained during baseline data collection 9-6 days before bedrest (BDC, supine position) and towards the end of two months head down tilt bedrest (MRI on day 56 and echocardiography on day 60 of HDT). Subjects were assigned to 30 minutes per day continuous short arm centrifugation (cAG), 6 times for 5 minutes interval short arm centrifugation, iAG), or a control group (ctr). We assessed aortic pulse wave velocity using oscillometric upper arm and thigh cuffs (PWV-2C, CardioCube, AIT, Vienna, Austria) and 4D-flow cardiac velocity encoded phase contrast magnetic resonance imaging (PWV-4D-MRI). We also measured area, area changes, and distensibility (AoD) of the ascending aorta by 2D-phase contrast cardiac MRI and arterial compliance (Ca) using transthoracic echocardiography. Results Mean aortic area increased in all subjects after 60 days head down tilt bedrest (5.3±0.7 vs. 5.8±0.7 cm², p<0.05). Stroke volume decreased from 94±13 to 84±10 ml (p<0.05) and pulse pressure from 56±11 to 46±9 mmHg (p<0.05) in part through reductions in stroke volume. The figure illustrates individual data on aortic properties (red diamonds = women). In contrast to the more consistent changes in aortic area, stroke volume, and pulse pressure, aortic distensibility, compliance, and pulse wave velocity responses show substantial inter-individual variability. Conclusion The important finding of our study is that 60 days strict head down bedrest elicit consistent changes in ascending aortic area, pulse pressure, and stroke volume. The resulting changes in vascular loading conditions likely confound vascular function measurements, both, in head down bedrest studies and in space

A new oscillometric method for pulse wave analysis: comparison with a common tonometric method

In the European Society of Cardiology–European Society of Hypertension guidelines of the year 2007, the consequences of arterial stiffness and wave reflection on cardiovascular mortality have a major role. But the investigators claimed the poor availability of devices/methods providing easy and widely suitable measuring of arterial wall stiffness or their surrogates like augmentation index (AIx) or aortic systolic blood pressure (aSBP). The aim of this study was the validation of a novel method determining AIx and aSBP based on an oscillometric method using a common cuff (ARCSolver) against a validated tonometric system (SphygmoCor). aSBP and AIx measured with the SphygmoCor and ARCSolver method were compared for 302 subjects. The mean age was 56 years with an s.d. of 20 years. At least two iterations were performed in each session. This resulted in 749 measurements. For aSBP the mean difference was −0.1 mm Hg with an s.d. of 3.1 mm Hg. The mean difference for AIx was 1.2% with an s.d. of 7.9%. There was no significant difference in reproducibility of AIx for both methods. The variation estimate of inter- and intraobserver measurements was 6.3% for ARCSolver and 7.5% for SphygmoCor. The ARCSolver method is a novel method determining AIx and aSBP based on an oscillometric system with a cuff. The results agree with common accepted tonometric measurements. Its application is easy and for widespread use

Arterial waveform parameters in a large, population-based sample of adults: relationships with ethnicity and lifestyle factors

Little is known about how aortic waveform parameters vary with ethnicity and lifestyle factors. We investigated these issues in a large, population-based sample. We carried out a cross-sectional analysis of 4798 men and women, aged 50–84 years from Auckland, New Zealand. Participants were 3961 European, 321 Pacific, 266 Maori and 250 South Asian people. We assessed modifiable lifestyle factors via questionnaires, and measured body mass index (BMI) and brachial blood pressure (BP). Suprasystolic oscillometry was used to derive aortic pressure, from which several haemodynamic parameters were calculated. Heavy alcohol consumption and BMI were positively related to most waveform parameters. Current smokers had higher levels of aortic augmentation index than non-smokers (difference=3.7%, P<0.0001). Aortic waveform parameters, controlling for demographics, antihypertensives, diabetes and cardiovascular disease (CVD), were higher in non-Europeans than in Europeans. Further adjustment for brachial BP or lifestyle factors (particularly BMI) reduced many differences but several remained. Despite even further adjustment for mean arterial pressure, pulse rate, height and total:high-density lipoprotein cholesterol, compared with Europeans, South Asians had higher levels of all measured aortic waveform parameters (for example, for backward pressure amplitude: β=1.5 mm Hg; P<0.0001), whereas Pacific people had 9% higher loge (excess pressure integral) (P<0.0001). In conclusion, aortic waveform parameters varied with ethnicity in line with the greater prevalence of CVD among non-white populations. Generally, this was true even after accounting for brachial BP, suggesting that waveform parameters may have increased usefulness in capturing ethnic variations in cardiovascular risk. Heavy alcohol consumption, smoking and especially BMI may partially contribute to elevated levels of these parameters

Validation of non-invasive central blood pressure devices: ARTERY Society task force consensus statement on protocol standardization

The original Riva-Rocci method to measure blood pressure (BP) using a cuff at the upper arm assumed the pressure obtained by this technique was a good proxy for central aortic BP.1,2 The clinical (prognostic) importance of brachial cuff BP is undeniable for both the assessment of cardiovascular risk associated with elevated BP and the benefits of treatment-induced BP reduction.3 However, it is also generally appreciated that peripheral artery systolic BP (SBP; brachial or radial artery) may be an inaccurate substitute for central SBP.4 This has been reported in human studies using intra-arterial catheterization of peripheral and central arteries.5–8 There may also be a discrepancy between peripheral and central BP responses to vasoactive drugs.9 These findings are corroborated in larger studies using non-invasive central aortic BP methods,10–13 and, while yet to be fully adopted in clinical practice, an independent prognostic value of central BP has been demonstrated.14–16 Altogether, there is a growing interest among clinicians towards improving risk estimates by using devices that provide more accurate measures of central aortic BP than those provided by current brachial cuff BP methods. Many non-invasive devices have been developed that purport to estimate central BP from different peripheral artery sites (e.g. radial, brachial, carotid arteries) using different principles of recording the pressure or surrogate signals (e.g. applanation tonometry, oscillometry, ultrasound, or magnetic resonance imaging) and different calibration methods to derive central BP. Since upper arm cuff-based devices to estimate central BP are more clinically appealing, in recent years several companies have developed such devices using a variety of techniques (e.g. oscillometric sub-diastolic or supra-systolic waveform analysis with generalized transfer functions), which employ a variety of signal processing steps to estimate central BP from peripheral signals.17,18 Yet, with no standardized guidelines,17 the accuracy testing of these new devices (as well as the preceding devices) has not been undertaken in a uniform fashion with comparable protocols, emphasizing the need for guidance in this field.19–22 An international task force was convened to address this situation