Increased ambulatory arterial stiffness index in obese children.

OBJECTIVE Altered arterial stiffness is a recognized risk factor of poor cardiovascular health. Ambulatory arterial stiffness index (AASI, defined as one minus the regression slope of diastolic on systolic blood pressure values derived from a 24 h arterial blood pressure monitoring, ABPM) is an upcoming and readily available marker of arterial stiffness. Our hypothesis was that AASI is increased in obese children compared to age- and gender matched healthy subjects. METHODS AASI was calculated from ABPM in 101 obese children (BMI ≥ 1.88 SDS according to age- and sex-specific BMI charts), 45% girls, median BMI SDS 2.8 (interquartile range (IQR) 2.5-3.4), median age 11.5 years (9.1-13.4) and compared with an age and gender matched healthy control group of 71 subjects with median BMI SDS 0.0 (-0.8-0.5). Multivariate regression analysis was applied to identify significant independent factors explaining AASI variability in this population. RESULTS AASI was significantly higher in obese children compared to controls (0.388 (0.254-0.499) versus 0.190 (0.070-0.320), p < 0.0001), but blood pressure values were similar. In a multivariate analysis including obese children only, AASI was independently predicted by 24-h systolic blood pressure SDS (p = 0.012); in a multivariate analysis including obese children and controls BMI SDS and pulse pressure independently influenced AASI (p < 0.001). CONCLUSIONS This study shows that AASI, a surrogate marker of arterial stiffness, is increased in obese children. AASI seems to be influenced by BMI and pulse pressure independently of systolic and diastolic blood pressure values, suggesting that other factors are involved in increased arterial stiffness in obese children.

Detection of haemorrhagic shock: Are vital signs obsolete? A commentary by Dr M. Luginbühl

The ATLS program by the American college of surgeons is probably the most important globally active training organization dedicated to improve trauma management. Detection of acute haemorrhagic shock belongs to the key issues in clinical practice and thus also in medical teaching. (In this issue of the journal William Schulz and Ian McConachrie critically review the ATLS shock classification Table 1), which has been criticized after several attempts of validation have failed [1]. The main problem is that distinct ranges of heart rate are related to ranges of uncompensated blood loss and that the heart rate decrease observed in severe haemorrhagic shock is ignored [2]. Table 1. Estimated blood loos based on patient's initial presentation (ATLS Students Course Manual, 9th Edition, American College of Surgeons 2012). Class I Class II Class III Class IV Blood loss ml Up to 750 750–1500 1500–2000 >2000 Blood loss (% blood volume) Up to 15% 15–30% 30–40% >40% Pulse rate (BPM) <100 100–120 120–140 >140 Systolic blood pressure Normal Normal Decreased Decreased Pulse pressure Normal or ↑ Decreased Decreased Decreased Respiratory rate 14–20 20–30 30–40 >35 Urine output (ml/h) >30 20–30 5–15 negligible CNS/mental status Slightly anxious Mildly anxious Anxious, confused Confused, lethargic Initial fluid replacement Crystalloid Crystalloid Crystalloid and blood Crystalloid and blood Table options In a retrospective evaluation of the Trauma Audit and Research Network (TARN) database blood loss was estimated according to the injuries in nearly 165,000 adult trauma patients and each patient was allocated to one of the four ATLS shock classes [3]. Although heart rate increased and systolic blood pressure decreased from class I to class IV, respiratory rate and GCS were similar. The median heart rate in class IV patients was substantially lower than the value of 140 min−1 postulated by ATLS. Moreover deterioration of the different parameters does not necessarily go parallel as suggested in the ATLS shock classification [4] and [5]. In all these studies injury severity score (ISS) and mortality increased with in increasing shock class [3] and with increasing heart rate and decreasing blood pressure [4] and [5]. This supports the general concept that the higher heart rate and the lower blood pressure, the sicker is the patient. A prospective study attempted to validate a shock classification derived from the ATLS shock classes [6]. The authors used a combination of heart rate, blood pressure, clinically estimated blood loss and response to fluid resuscitation to classify trauma patients (Table 2) [6]. In their initial assessment of 715 predominantly blunt trauma patients 78% were classified as normal (Class 0), 14% as Class I, 6% as Class II and only 1% as Class III and Class IV respectively. This corresponds to the results from the previous retrospective studies [4] and [5]. The main endpoint used in the prospective study was therefore presence or absence of significant haemorrhage, defined as chest tube drainage >500 ml, evidence of >500 ml of blood loss in peritoneum, retroperitoneum or pelvic cavity on CT scan or requirement of any blood transfusion >2000 ml of crystalloid. Because of the low prevalence of class II or higher grades statistical evaluation was limited to a comparison between Class 0 and Class I–IV combined. As in the retrospective studies, Lawton did not find a statistical difference of heart rate and blood pressure among the five groups either, although there was a tendency to a higher heart rate in Class II patients. Apparently classification during primary survey did not rely on vital signs but considered the rather soft criterion of “clinical estimation of blood loss” and requirement of fluid substitution. This suggests that allocation of an individual patient to a shock classification was probably more an intuitive decision than an objective calculation the shock classification. Nevertheless it was a significant predictor of ISS [6]. Table 2. Shock grade categories in prospective validation study (Lawton, 2014) [6]. Normal No haemorrhage Class I Mild Class II Moderate Class III Severe Class IV Moribund Vitals Normal Normal HR > 100 with SBP >90 mmHg SBP < 90 mmHg SBP < 90 mmHg or imminent arrest Response to fluid bolus (1000 ml) NA Yes, no further fluid required Yes, no further fluid required Requires repeated fluid boluses Declining SBP despite fluid boluses Estimated blood loss (ml) None Up to 750 750–1500 1500–2000 >2000 Table options What does this mean for clinical practice and medical teaching? All these studies illustrate the difficulty to validate a useful and accepted physiologic general concept of the response of the organism to fluid loss: Decrease of cardiac output, increase of heart rate, decrease of pulse pressure occurring first and hypotension and bradycardia occurring only later. Increasing heart rate, increasing diastolic blood pressure or decreasing systolic blood pressure should make any clinician consider hypovolaemia first, because it is treatable and deterioration of the patient is preventable. This is true for the patient on the ward, the sedated patient in the intensive care unit or the anesthetized patients in the OR. We will therefore continue to teach this typical pattern but will continue to mention the exceptions and pitfalls on a second stage. The shock classification of ATLS is primarily used to illustrate the typical pattern of acute haemorrhagic shock (tachycardia and hypotension) as opposed to the Cushing reflex (bradycardia and hypertension) in severe head injury and intracranial hypertension or to the neurogenic shock in acute tetraplegia or high paraplegia (relative bradycardia and hypotension). Schulz and McConachrie nicely summarize the various confounders and exceptions from the general pattern and explain why in clinical reality patients often do not present with the “typical” pictures of our textbooks [1]. ATLS refers to the pitfalls in the signs of acute haemorrhage as well: Advanced age, athletes, pregnancy, medications and pace makers and explicitly state that individual subjects may not follow the general pattern. Obviously the ATLS shock classification which is the basis for a number of questions in the written test of the ATLS students course and which has been used for decades probably needs modification and cannot be literally applied in clinical practice. The European Trauma Course, another important Trauma training program uses the same parameters to estimate blood loss together with clinical exam and laboratory findings (e.g. base deficit and lactate) but does not use a shock classification related to absolute values. In conclusion the typical physiologic response to haemorrhage as illustrated by the ATLS shock classes remains an important issue in clinical practice and in teaching. The estimation of the severity haemorrhage in the initial assessment trauma patients is (and was never) solely based on vital signs only but includes the pattern of injuries, the requirement of fluid substitution and potential confounders. Vital signs are not obsolete especially in the course of treatment but must be interpreted in view of the clinical context. Conflict of interest None declared. Member of Swiss national ATLS core faculty.

Ethnic disparity in defensive coping endothelial responses: The SABPA study

OBJECTIVES Defensive coping (DefS) in Blacks has been associated with greater cardiovascular risk than in their White counterparts. We examined associations between endothelial function mental stress responses and markers of vascular structure in a bi-ethnic cohort. METHODS We examined vascular function and structure in 368 Black (43.84±8.31years) and White Africans (44.78±10.90years). Fasting blood samples, 24h blood pressure, left carotid intima-media thickness of the far wall (L-CIMTf), and left carotid cross-sectional wall area (L-CSWA) values were obtained. von Willebrand factor (VWF), endothelin-1 (ET-1) and nitric oxide metabolite (NOx) responses to the Stroop mental stress test were calculated to assess endothelial function. DefS was assessed using the Coping Strategy Indicator questionnaire. Interaction between main effects was demonstrated for 283 participants with DefS scores above the mean of 26 for L-CIMTf. RESULTS Blunted stress responses for VWF (men 16.71% vs. 51.10%; women 0.85% vs. 42.09%, respectively) and NOx (men -64.52% vs. 74.89%; women -76.16% vs. 113.29%, respectively) were evident in the DefS Blacks compared to the DefS Whites (p<0.001). ET-1 increased more in Blacks (men 150% and women 227%, p<0.001) compared to the Whites (men 61.25% and women 35.49%, p<0.001). Ambulatory pulse pressure, but not endothelial function markers, contributed to L-CIMTf (ΔR(2)=0.11 p<0.001), and L-CSWA (ΔR(2)=0.08, p<0.001) in DefS African men but not in any other group. CONCLUSIONS Blunted stress-induced NOx and VWF responses and augmented ET-1 responses in DefS Blacks indicate endothelial dysfunction. DefS may facilitate disturbed endothelial responses and enforce vascular remodelling via compensatory increases in pulse pressure in Black men. These observations may indicate an increased risk of cardiovascular incidents via functional and structural changes of the vasculature in DefS Blacks.

1D.03: Inactive Matrix Gla Protein is Assocated with Renal Resistive Index in a Population-Based Study

OBJECTIVE Renal resistive index (RRI) varies directly with renal vascular stiffness and pulse pressure. RRI correlates positively with arteriolosclerosis in damaged kidneys and predicts progressive renal dysfunction. Matrix Gla-protein (MGP) is a vascular calcification inhibitor that needs vitamin K to be activated. Inactive MGP, known as desphospho-uncarboxylated MGP (dp-ucMGP), can be measured in plasma and has been associated with various cardiovascular (CV) markers, CV outcomes and mortality. In this study we hypothesize that increased RRI is associated with high levels of dp-ucMGP. DESIGN AND METHOD We recruited participants via a multi-center family-based cross-sectional study in Switzerland exploring the role of genes and kidney hemodynamics in blood pressure regulation. Dp-ucMGP was quantified in plasma samples by sandwich ELISA. Renal doppler sonography was performed using a standardized protocol to measure RRIs on 3 segmental arteries in each kidney. The mean of the 6 measures was reported. Multiple regression analysis was performed to estimate associations between RRI and dp-ucMGP adjusting for sex, age, pulse pressure, mean pressure, renal function and other CV risk factors. RESULTS We included 1035 participants in our analyses. Mean values were 0.64 ± 0.06 for RRI and 0.44 ± 0.21 (nmol/L) for dp-ucMGP. RRI was positively associated with dp-ucMGP both before and after adjustment for sex, age, body mass index, pulse pressure, mean pressure, heart rate, renal function, low and high density lipoprotein, smoking status, diabetes, blood pressure and cholesterol lowering drugs, and history of CV disease (P < 0.001). CONCLUSIONS RRI is independently and positively associated with high levels of dp-ucMGP after adjustment for pulse pressure and common CV risk factors. Further studies are needed to determine if vitamin K supplementation can have a positive effect on renal vascular stiffness and kidney function.

The role of the experience and expression of anger in future cardiovascular profiles in young adolescents

Cardiovascular disease (CVD) is this nation's leading source of morbidity and mortality, with health disparities evident. Despite inconsistencies in the literature, there is a growing body of evidence that links anger and CV reactivity (CVR) to future CVD. Because CVD is a life-long process with beginnings in childhood, and because adolescents experience and express anger frequently, the need to understand the role that anger has in future CV profiles is important. If identifiable patterns are found, nursing interventions can be implemented at the most beneficial point in the lifespan. This study examined data collected as part of The Heartfelt Study (N = 374), which investigated anger in relation to 24-hour ambulatory blood pressure (BP) and CVR in a multi-ethnic (African, Hispanic, and European American) sample of adolescents (Time 1). This investigator conducted a follow-up for all The Heartfelt Study participants, 11 to 13 years old at the beginning of study, still in attendance at the middle school (N = 44) one year later (Time 2) to determine: (1) changes in anger over time were associated with changes in ambulatory CV profiles: systolic (SBP), diastolic (DBP), heart rate (HR), and pulse pressure (PP) over time; and (2) the extent to which CVR, initiated by talking about a recent anger-producing event, related to future ambulatory CV profiles. A mixed-effects regression for repeated measures was used to analyze the data and found that SBP reactivity at Time 1 was significantly (β = 0.2341, t = 5.91, p < 0.0001) associated with ambulatory SBP at Time 2 and PP reactivity at Time 1 was significantly (β = 0.1530, t = 5.70, p < 0.0001) associated with ambulatory PP at Time 2. Changes in anger over time were not associated with changes in ambulatory BP measures over time. Further research on anger and CVR among adolescents over longer periods of time is recommended. ^

Hemodynamic changes associated with manual and automated lateral rotation in mechanically ventilated intensive care patients

Objective: To investigate hemodynamic responses to lateral rotation. ^ Design: Time-series within a randomized controlled trial pilot study. ^ Setting: A medical intensive care unit (ICU) and a medical-surgical ICU in two tertiary care hospitals. ^ Patients: Adult patients receiving mechanical ventilation. ^ Interventions: Two-hourly manual or continuous automated lateral rotation. ^ Measurements and Main Results: Heart rate (HR) and arterial pressure were sampled every 6 seconds for > 24 hours, and pulse pressure (PP) was computed. Turn data were obtained from a turning flow sheet (manual turn) or with an angle sensor (automated turn). Within-subject ensemble averages were computed for HR, mean arterial pressure (MAP), and PP across turns. Sixteen patients were randomized to either the manual (n = 8) or automated (n = 8) turn. Three patients did not complete the study due to hemodynamic instability, bed malfunction or extubation, leaving 13 patients (n = 6 manual turn and n = 7 automated turn) for analysis. Seven patients (54%) had an arterial line. Changes in hemodynamic variables were statistically significant increases ( p < .05), but few changes were clinically important, defined as ≥ 10 bpm (HR) or ≥ 10 mmHg (MAP and PP), and were observed only in the manual-turn group. All manual-turn patients had prolonged recovery to baseline in HR, MAP and PP of up to 45 minutes (p ≤ .05). No significant turning-related periodicities were found for HR, MAP, or PP. Cross-correlations between variables showed variable lead-lag relations in both groups. A statistically, but not clinically, significant increase in HR of 3 bpm was found for the manual-turn group in the back compared with the right lateral position ( F = 14.37, df = 1, 11, p = .003). ^ Conclusions: Mechanically ventilated critically ill patients experience modest hemodynamic changes with manual lateral rotation. A clinically inconsequential increase in HR, MAP, and PP may persist for up to 45 minutes. Automated lateral rotation has negligible hemodynamic effects. ^

Cardiovascular implications of exposure to traffic air pollution during exercise

Regular aerobic exercise is recommended by physicians to improve health and longevity. However, individuals exercising in urban regions are often in contact with air pollution, which includes particles and gases associated with respiratory disease and cancer. We describe the recent evidence on the cardiovascular effects of air pollution, and the implications of exercising in polluted environments, with a view to informing clinicians and other health professionals. There is now strong evidence that fine and ultra fine particulate matter present in air pollution increases cardiovascular morbidity and mortality. The main mechanisms of disease appear to be related to an increase in the pathogenic processes associated with atherosclerosis. People exercising in environments pervaded by air contaminants are probably at increased risk, due to an exercise-induced amplification in respiratory uptake, lung deposition and toxicity of inhaled pollutants. We make evidence-based recommendations for minimizing exposure to air-borne toxins while exercising, and suggest that this advice be passed on to patients where appropriate.

Noninvasive tests for arterial structure, function, and compliance: Do they identify risk or diagnose disease?

Background: Brachial artery reactivity (BAR), carotid intima-media thickness (IMT), and applanation tonometry for evaluation of total arterial compliance may provide information about preclinical vascular disease. We sought to determine whether these tests could be used to identify patients with coronary artery disease (CAD) without being influenced by their ability to identify those at risk ford CAD developing. Methods: We studied 100 patients and compared 3 groups: 35 patients with known CAD; 34 patients with symptoms and risk factors but no CAD identified by stress echocardiography (risk group); and 31 control subjects. BAR and IMT were measured using standard methods, and total arterial compliance was calculated by the pulse-pressure method from simultaneous radial applanation tonometry and pulsed wave Doppler of the left ventricular outflow. Ischemia was identified as a new or worsening wall-motion abnormality induced by stress. Results: In a comparison between the control subjects and patients either at risk for developing CAD or with CAD, the predictors of risk for CAD were: age (P = .01); smoking history (P = .002); hypercholesterolemia (P = .002); and hypertension (P = .004) (model R = 0.82; P = .0001). The independent predictors of CAD were: IMT (P = .001); BAR (P = .04); sex (P = .005); and hypertension (P = .005) (model R = 0.80; P = .0001). Conclusion: IMT, BAR, and traditional cardiovascular risk factors appear to identify patients at risk for CAD developing. However, only IMT was significantly different between patients at risk for developing CAD and those with overt CAD.

Response of B-type natriuretic pepticle to exercise in hypertensive patients with suspected diastolic heart failure: Correlation with cardiac function, hemodynamics, and workload

Background Diastolic heart failure (DHF) is characterized by dyspnea due to increased left ventricular (LV) filling pressures during stress. We sought the relationship of exercise-induced increases in B-type natriuretic peptide (BNP) to LV filling pressures and parameters of cardiovascular performance in suspected DHF. Methods Twenty-six treated hypertensive patients with suspected DHF (exertional dyspnea, LV ejection fraction >50%, and diastolic dysfunction) underwent maximal exercise echocardiography using the Bruce protocol. BNP, transmitral Doppler, and tissue Doppler for systolic (So) and early (Ea) and late (Aa) diastolic mitral annular velocities were obtained at rest and peak stress. LV filling pressures were estimated with E/Ea ratios. Results Resting BNP correlated with resting pulse pressure (r=0.45, P=0.02). Maximal exercise performance (4.6 +/- 2.5min) was limited by dyspnea. Blood pressure increased with exercise (from 143 +/- 19/88 +/- 8 to 191 +/- 22/90 +/- 10 mm Hg); 13 patients (50%) had a hypertensive response. Peak exercise BNP correlated with peak transmitral E velocity (r = 0.41, P <.05) and peak heart rate (r = -0.40, P <.05). BNP increased with exercise (from 48 57 to 74 97 pg/mL, P =.007), and the increment of BNP with exercise was associated with maximal workload and peak exercise So, Ea, and Aa (P <.01 for all). Filling pressures, approximated by lateral E/Ea ratio, increased with exercise (7.7 +/- 2.0 to 10.0 +/- 4.8, P <.01). BNP was higher in patients with possibly elevated filling pressures at peak exercise (E/Ea >10) compared to those with normal pressures (123 +/- 124 vs 45 +/- 71 pg/mL, P =.027). Conclusions Augmentation of BNP with exercise in hypertensive patients with suspected DHF is associated with better exercise capacity, LV systolic and diastolic function, and left atrial function. Peak exercise BNP levels may identify exercise-induced elevation of filling pressures in DHF.

The effect of exercise on large artery haemodynamics in healthy young men

Background Brachial blood pressure predicts cardiovascular outcome at rest and during exercise. However, because of pulse pressure amplification, there is a marked difference between brachial pressure and central (aortic) pressure. Although central pressure is likely to have greater clinical importance, very little data exist regarding the central haemodynamic response to exercise. The aim of the present study was to determine the central and peripheral haemodynamic response to incremental aerobic exercise. Materials and methods Twelve healthy men aged 31 +/- 1 years (mean +/- SEM) exercised at 50%, 60%, 70% and 80% of their maximal heart rate (HRmax) on a bicycle ergometer. Central blood pressure and estimated aortic pulse wave velocity, assessed by timing of the reflected wave (T-R), were obtained noninvasively using pulse wave analysis. Pulse pressure amplification was defined as the ratio of peripheral to central pulse pressure and, to assess the influence of wave reflection on amplification, the ratio of peripheral pulse pressure to nonaugmented central pulse pressure (PPP : CDBP-P-1) was also calculated. Results During exercise, there was a significant, intensity-related, increase in mean arterial pressure and heart rate (P < 0.001). There was also a significant increase in pulse pressure amplification and in PPP : CDBP-P-1 (P < 0.001), but both were independent of exercise intensity. Estimated aortic pulse wave velocity increased during exercise (P < 0.001), indicating increased aortic stiffness. There was also a positive association between aortic pulse wave velocity and mean arterial pressure (r = 0.54; P < 0.001). Conclusions Exercise significantly increases pulse pressure amplification and estimated aortic stiffness.

Myocardial and vascular dysfunction and exercise capacity in the metabolic syndrome

The metabolic syndrome (MS) is associated with cardiovascular risk exceeding that expected from atherosclerotic risk factors, but the mechanism of this association is unclear. We sought to determine the effects of the MS on myocardial and vascular function and cardiorespiratory fitness in 393 subjects with significant risk factors but no cardiovascular disease and negative stress echocardiographic findings. Myocardial function was assessed by global strain rate, strain, and regional systolic velocity (s(m)) and diastolic velocity (e(m)) using tissue Doppler imaging. Arterial compliance was assessed using the pulse pressure method, involving simultaneous radial applanation tonometry and echocardiographic measurement of stroke volume. Exercise capacity was measured by expired gas analysis. Significant and incremental variations in left ventricular systolic (s(m), global strain, and strain rate) and diastolic (e(m)) function were found according to the number of components of MS (p <0.001). MS contributed to reduced systolic and diastolic function even in those without left ventricular hypertrophy (p <0.01). A similar dose-response association was present between the number of components of the MS and exercise capacity (p <0.001) and arterial compliance. The global strain rate and em were independent predictors of exercise capacity. In conclusion, subclinical left ventricular dysfunction corresponded to the degree of metabolic burden, and these myocardial changes were associated with reduced cardiorespiratory fitness.' Subjects with MS who also have subclinical myocardial abnormalities and reduced cardiorespiratory fitness may have a higher risk of cardiovascular disease events and heart failure. (C) 2005 Elsevier Inc. All rights reserved.

Influence of arterial compliance on presence and extent of ischaemia during stress echocardiography

Objective: To seek an association between total arterial compliance (TAC) and the extent of ischaemia at stress echocardiography. Design: Cohort study. Setting: Regional cardiac centre. Methods: 255 consecutive patients (147 men; mean (SD) age 58 (8)) presenting for stress echocardiography for clinical indications were studied. Wall motion score index (WMSI) was calculated and ischaemia was defined by an inducible or worsening wall motion abnormality. Peak WMSI was used to reflect the extent of dysfunction (ischaemia or scar), and Delta WMSI was indicative of extent of ischaemia. TAC was assessed at rest by simultaneous radial applanation tonometry and pulsed wave Doppler in all patients. Results: Ischaemia was identified by stress echocardiography in 65 patients (25%). TAC was similar in the groups with negative and positive echocardiograms (1.08 (0.41) v 1.17 (0.51) ml/ mm Hg, not significant). However, the extent of dysfunction was associated with TAC independently of age, blood pressure, risk factors, and use of a beta blocker. Moreover, the extent of ischaemia was determined by TAC, risk factors, and use of a b blocker. Conclusion: While traditional cardiovascular risk factors are strong predictors of ischaemia on stress echocardiography, TAC is an independent predictor of the extent of ischaemia.

Abnormal systemic and ocular vascular response to temperature provocation in primary open-angle glaucoma patients:a case for autonomic failure?

PURPOSE. To assess systemic and ocular vascular reactivity in response to warm and cold provocation in untreated patients with primary open-angle glaucoma and normal control subjects. METHODS. Twenty-four patients with primary open-angle glaucoma and 22 normal control subjects were subjected to a modified cold pressor test involving immersion of the right hand in 40°C warm water followed by 4°C cold water exposure, and finger and ocular blood flow were assessed by means of peripheral laser Doppler flowmetry and retinal flowmetry, respectively. Finger and body temperature as well as intraocular pressure, systemic blood pressure, systemic pulse pressure, heart rate, and ocular perfusion pressure were also monitored. RESULTS. The patients with glaucoma demonstrated an increase in diastolic blood pressure (P = 0.023), heart rate (P = 0.010), and mean ocular perfusion pressure (P = 0.039) during immersion of the tested hand in 40°C water. During cold provocation, the patients demonstrated a significant decrease in finger (P = 0.0003) and ocular blood flow (the parameter velocity measured at the temporal neuroretinal rim area; P = 0.021). Normal subjects did not demonstrate any blood flow or finger temperature changes during immersion of the tested hand in 40°C water (P > 0.05); however, they exhibited increases in systolic blood pressure (P = 0.034) and pulse pressure (P = 0.0009) and a decrease in finger blood flow (P = 0.0001) during cold provocation. In normal subjects, the ocular blood flow was unchanged during high- and low-temperature challenge. CONCLUSIONS. Cold provocation elicits a different blood pressure, and ocular blood flow response in patients with primary open-angle glaucoma compared with control subjects. These findings suggest a systemic autonomic failure and ocular vascular dysregulation in POAG patients.

Effects of Exposure to the Sound from Seismic Airguns on Pallid Sturgeon and Paddlefish - Data Set

Dataset for publication in PLOS One

A systems approach to cardiovascular health and disease with a focus on aortic wave dynamics

Cardiovascular diseases (CVDs) have reached an epidemic proportion in the US and worldwide with serious consequences in terms of human suffering and economic impact. More than one third of American adults are suffering from CVDs. The total direct and indirect costs of CVDs are more than $500 billion per year. Therefore, there is an urgent need to develop noninvasive diagnostics methods, to design minimally invasive assist devices, and to develop economical and easy-to-use monitoring systems for cardiovascular diseases. In order to achieve these goals, it is necessary to gain a better understanding of the subsystems that constitute the cardiovascular system. The aorta is one of these subsystems whose role in cardiovascular functioning has been underestimated. Traditionally, the aorta and its branches have been viewed as resistive conduits connected to an active pump (left ventricle of the heart). However, this perception fails to explain many observed physiological results. My goal in this thesis is to demonstrate the subtle but important role of the aorta as a system, with focus on the wave dynamics in the aorta.

The operation of a healthy heart is based on an optimized balance between its pumping characteristics and the hemodynamics of the aorta and vascular branches. The delicate balance between the aorta and heart can be impaired due to aging, smoking, or disease. The heart generates pulsatile flow that produces pressure and flow waves as it enters into the compliant aorta. These aortic waves propagate and reflect from reflection sites (bifurcations and tapering). They can act constructively and assist the blood circulation. However, they may act destructively, promoting diseases or initiating sudden cardiac death. These waves also carry information about the diseases of the heart, vascular disease, and coupling of heart and aorta. In order to elucidate the role of the aorta as a dynamic system, the interplay between the dominant wave dynamic parameters is investigated in this study. These parameters are heart rate, aortic compliance (wave speed), and locations of reflection sites. Both computational and experimental approaches have been used in this research. In some cases, the results are further explained using theoretical models.

The main findings of this study are as follows: (i) developing a physiologically realistic outflow boundary condition for blood flow modeling in a compliant vasculature; (ii) demonstrating that pulse pressure as a single index cannot predict the true level of pulsatile workload on the left ventricle; (iii) proving that there is an optimum heart rate in which the pulsatile workload of the heart is minimized and that the optimum heart rate shifts to a higher value as aortic rigidity increases; (iv) introducing a simple bio-inspired device for correction and optimization of aortic wave reflection that reduces the workload on the heart; (v) deriving a non-dimensional number that can predict the optimum wave dynamic state in a mammalian cardiovascular system; (vi) demonstrating that waves can create a pumping effect in the aorta; (vii) introducing a system parameter and a new medical index, Intrinsic Frequency, that can be used for noninvasive diagnosis of heart and vascular diseases; and (viii) proposing a new medical hypothesis for sudden cardiac death in young athletes.