Gender differences in vascular compliance in young, healthy subjects assessed by pulse contour analysis

Novel superpixel method to visualize fundus blood flow resistivity in healthy adults

We aimed to perform superpixel segmentation of ocular blood flow maps obtained using laser speckle flowgraphy (LSFG) and investigate the effects of systemic parameters such as body weight, height, and sex on ocular blood flow resistivity. We studied 757 healthy participants (583 men, 174 women). We calculated the average beat strength over mean blur rate (BOM) as a LSFG resistivity index, as a function of age and sex using ordinary regions of interest (ROI) centered on the optic nerve head (ONH), the retinal vessels region and tissue around the ONH, and the choroid (CHD). We compared the ROI and superpixel-based methods, which are segmented based on image processing, for calculating the BOM. The sex differences in the BOM for the ONH, retinal-vessels region and tissue region of the ONH and CHD were significant for individuals aged ≤ 50 years (P < 0.01) but not those > 50 years old (P > 0.05). The average BOMs calculated using the ROI and superpixel methods were strongly correlated in the ONH (coefficient = 0.87, R² = 0.8, P < 0.0001, n = 5465). In summary, a superpixel-segmented BOM map is suitable for two-dimensional visualization of ocular blood flow resistivity.

Characterization of forehead blood flow bias on NIRS signals during neural activation with a verbal fluency task

The major problem of near-infrared spectroscopy (NIRS) for brain activity measurement during verbal fluency task is the overlapping forehead scalp blood flow (FBF) on the target cerebral blood flow (CBF). There could be among-individual differences in the influence of FBF on CBF. We investigated effects of FBF on CBF by comparing signals obtained through a laser Doppler flowmeter (LDF) and NIRS using the modified Beer-Lambert Law (MBLL). Among 25 healthy individuals, 7 participants showed a strong correlation between LDF and NIRS signals (r_s >0.500). There were no significant differences according to age or sex. Subsequently, we applied the hemodynamic separation method to the values calculated using the MBLL (Δ[oxy-Hb]_M): to separate the concentration of oxygenated hemoglobin in the forehead (Δ[oxy-Hb]_F) and cerebral cortex (Δ[oxy-Hb]_C). First, we found that the influence of Δ[oxy-Hb]_F on Δ[oxy-Hb]_C in the high r_s group was almost twice as large as that in the low r_s group. Second, presence of sex and age differences in the influence of Δ[oxy-Hb]_F on Δ[oxy-Hb]_C were suggested. Based on the results, we discuss the factors affecting FBF and the resulting variations in NIRS signals.

The effect of grape (Vitis vinifera) seed extract supplementation on flow-mediated dilation, blood pressure, and heart rate: A systematic review and meta-analysis of controlled trials with duration- and dose-response analysis

The objective of this systematic review and meta-analysis of controlled trials was to assess the long-term effect of grape seed extract (GSE) supplementation on flow-mediated dilation (FMD), systolic blood pressure (SBP), diastolic blood pressure (DBP), and heart rate (HR) in adults. Web of Science, Scopus, Medline, Cochrane Library, and Google Scholar were searched up to May 24, 2021. Nineteen trials were included in this study. Weighted mean difference (WMD) and 95% confidence interval (CI) were calculated using a random-effects model. GSE supplementation significantly reduced DBP (WMD: -2.20 mmHg, 95% CI: -3.79 to -0.60, I² = 88.8%) and HR (WMD: -1.25 bpm, 95% CI: -2.32 to -0.19, I² = 59.5%) but had no significant effects on FMD (WMD: 1.02%, 95% CI: -0.62 to 2.66, I² = 92.0%) and SBP (WMD: -3.55 mmHg, 95% CI: -7.59 to 0.49, I² = 97.4%). Subgroup analysis revealed that the dose and duration of GSE administration and the characteristics of study participants could be sources of between-study heterogeneity. Significant non-linear relationships were found between DBP and the duration of GSE supplementation (P = 0.044) and its dose (P = 0.007). In conclusion, GSE may be beneficial for individuals with or at risk of cardiovascular disease because it may have hypotensive and HR-lowering properties.

Sex differences in the vascular function and related mechanisms: role of 17β-estradiol

The incidence of cardiovascular disease (CVD) is lower in premenopausal women but increases with age and menopause compared with similarly aged men. Based on the prevalence of CVD in postmenopausal women, sex hormone-dependent mechanisms have been postulated to be the primary factors responsible for the protection from CVD in premenopausal women. Recent Women’s Health Initiative studies, Cochrane Review studies, the Early Versus Late Intervention Trial with Estradiol Study, and the Kronos Early Estrogen Prevention Study have suggested that beneficial effects of hormone replacement therapy (HRT) are seen in women of <60 yr of age and if initiated within <10 yr of menopause. In contrast, the beneficial effects of HRT are not seen in women of >60 yr of age and if commenced after 10 yr of menopause. The higher incidence of CVD and the failure of HRT in postmenopausal aged women could be partly associated with fundamental differences in the vascular structure and function between men and women and in between pre- and postmenopausal women, respectively. In this regard, previous studies from human and animal studies have identified several sex differences in vascular function and associated mechanisms. The female sex hormone 17β-estradiol regulates the majority of these mechanisms. In this review, we summarize the sex differences in vascular structure, myogenic properties, endothelium-dependent and -independent mechanisms, and the role of 17β-estradiol in the regulation of vascular function.

The independent association of preoperative serum albumin on the functional maturation of radiocephalic arteriovenous fistulae

PURPOSE

The aim of this study is to test the null hypothesis that preoperative albumin along with other preoperative confounders have no impact on the functional maturation of radiocephalic arteriovenous fistulae (RCAVF).

METHODS

A retrospective cohort study of n = 195 individuals undergoing RCAVF formation from July 2013 to December 2015 was conducted. The null hypothesis was assessed through chi squared test. Independent association of each variable was evaluated through univariate and multivariate logistic regression model. Pearson's correlation test was also performed between scale variables to establish their causal link.

RESULTS

Preoperative hypoalbuminaemic group of individuals demonstrated significant failure of maturation (49.3% vs. 27.2%, p = 0.002). At multivariate analysis, hypoalbuminemia remained an independent marker of fistula failure (OR 0.40, 95% CI 0.21-0.76, p = 0.004) and demonstrated a weak but a positive correlation at the endpoint of maturation (R = 0.223, p = 0.002).

CONCLUSIONS

Preoperative hypoalbuminemia (<35 mg/dL) is independently associated with 40% reduction in the functional maturation of RCAVF. Stratification of this readily available biomarker prior to RCAVF formation may require consideration subjected to further research.

Gender differences in tibial microvascular flow responses to head down tilt and lower body negative pressure

The purpose of the investigation was to study lower body negative pressure recovery in response to head down tilt position in men and women. The study examined the primary hypothesis that tibial bone microvascular flow responses to HDT and lower body negative pressure (LBNP) differ in women and men. Nine women and nine men between 20 to 30 years of age participated in the study. Tibial microvascular flow, head and tibial oxygenation and calf circumference were measured using photoplethysmography (PPG), near‐infrared spectroscopy (NIRS) and strain gauge plethysmography (SGP), respectively, during sitting (control baseline), supine, 15° HDT, and 15° HDT with 25 mmHg LBNP. Tibial microvascular flow with HDT increased by 57% from supine position (from 1.4V ± 0.7 to 2.2V ± 1.0 HDT; ANOVA P < 0.05) in men but there is no significant difference between supine and HDT in women. Ten minutes of LBNP during 15^oHDT restored tibial bone microvascular flows to supine levels, (from 2.2V±1.0 HDT to 1.1V ± 0.7 supine; ANOVA P < 0.05) in men but not in women. These data support the concept that there are gender specific microvascular responses to a fluid‐shift countermeasure such as LBNP. Thus, gender differences should be considered while developing future countermeasure strategies to headward fluid shifts in microgravity.

Sex differences in ventricular-vascular coupling following endurance training

Introduction

Ventricular and vascular coupling is defined as the ratio of arterial elastance (Ea) to ventricular elastance (Elv) and describes the interaction between the heart and arterial system. There are sex differences in both arterial and ventricular function in response to both acute exercise and aerobic exercise training.

Purpose

To examine the effects of aerobic exercise training on elastances and the coupling ratio in young adult men and women. We hypothesized a reduction in the coupling ratio in both sexes due to a decrease in Ea that would be more pronounced in men and an increase in Elv that would be larger in women.

Methods

Fifty-three healthy, young adults completed the study. Central pulse wave velocity and heart volumes were measured before and after an 8-week aerobic training intervention. Elastances were calculated as Ea = end-systolic pressure/stroke volume and Elv = end-systolic pressure/end-systolic volume and indexed to body surface area.

Results

After the intervention, women augmented indexed and un-indexed Elv from 2.09 ± 0.61 to 2.52 ± 0.80 mmHg/ml, p < 0.05, and reduced the coupling ratio from 0.72 ± 18 to 0.62 ± 15, p < 0.05, while men maintained their pre-training ratio (from 0.66 ± 0.20 to 0.74 ± 0.21, p > 0.05). Women also reduced end-systolic pressure (from 91 ± 10 to 87 ± 10 mmHg), and both groups reduced central pulse wave velocity (from 6.0 ± 1.0 to 5.6 ± 0.6 m/s, p < 0.05).

Conclusion

We conclude that after 8 weeks of aerobic training, only women reduced their coupling ratio due to an increase in Elv. This suggests that aerobic exercise training elicits sex-dependent changes in the coupling ratio in young, healthy individuals.

A comparison of third-generation semi-invasive arterial waveform analysis with thermodilution in patients undergoing coronary surgery

Uncalibrated semi-invasive continous monitoring of cardiac index (CI) has recently gained increasing interest. The aim of the present study was to compare the accuracy of CI determination based on arterial waveform analysis with transpulmonary thermodilution. Fifty patients scheduled for elective coronary surgery were studied after induction of anaesthesia and before and after cardiopulmonary bypass (CPB), respectively. Each patient was monitored with a central venous line, the PiCCO system, and the FloTrac/Vigileo-system. Measurements included CI derived by transpulmonary thermodilution and uncalibrated semi-invasive pulse contour analysis. Percentage changes of CI were calculated. There was a moderate, but significant correlation between pulse contour CI and thermodilution CI both before (r² = 0.72, P < 0.0001) and after (r² = 0.62, P < 0.0001) CPB, with a percentage error of 31% and 25%, respectively. Changes in pulse contour CI showed a significant correlation with changes in thermodilution CI both before (r² = 0.52, P < 0.0001) and after (r² = 0.67, P < 0.0001) CPB. Our findings demonstrated that uncalibrated semi-invasive monitoring system was able to reliably measure CI compared with transpulmonary thermodilution in patients undergoing elective coronary surgery. Furthermore, the semi-invasive monitoring device was able to track haemodynamic changes and trends.

Effects of an 8-month yoga intervention on arterial compliance and muscle strength in premenopausal women

Previous studies have indicated that Yoga exercise has a positive effect on reducing blood pressure and heart rate. However, no randomized controlled studies to date have investigated its effects on arterial compliance. The purpose of this study was to investigate the effects of an 8-month Yoga intervention on arterial compliance and muscle strength in normal premenopausal women 35-50 years of age. Thirty-four women were randomly assigned either to a Yoga exercise group (YE, n = 16) or a control group (CON, n = 18). Participants in YE group performed 60 minutes of an Ashtanga Yoga series 2 times/week with one day between sessions for 8 months. Each Yoga session consisted of 15 minutes of warm-up exercises, 35 minutes of Ashtanga Yoga postures and 10 minutes of cool-down with relaxation; and the session intensity was progressively increased during the 8 months. Participants in CON were encouraged to maintain their normal daily lifestyles monitored by the bone-specific physical activity questionnaire at 2 month intervals for 8 months. Arterial compliance (pulse contour analysis) and muscle strength (1 Repetition Maximum) were assessed at baseline and after the intervention. Arterial compliance of the large and small arteries was not affected by the 8 month Yoga training (p > 0.05). Also, there were no significant (p > 0.05) group, time, or group × time interaction effects for cardiovascular variables. YE group significantly (p < 0.01) improved leg press muscle strength compared to CON (11.4% vs. -6.5%). Eight months of Ashtanga Yoga training was beneficial for improving leg press strength, but not arterial compliance in premenopausal women. Key pointsThe 8 month Yoga training did not affect arterial compliance of the large and small arteries.None of the cardiovascular variables were changed by the Yoga intervention.Isotonic muscle strength was not altered by the Yoga intervention, with the exception of leg press.

Cardio-ventilatory coupling in young healthy resting subjects

In this work, cardio-ventilatory coupling (CVC) refers to the statistical relationship between the onset of either inspiration (I) or expiration (E) and the timing of heartbeats (R-waves) before and after these respiratory events. CVC was assessed in healthy, young (<45 yr), resting, supine subjects (n = 19). Four intervals were analyzed: time from I-onset to both the prior R-wave (R-to-I) and the following R-wave (I-to-R), as well as time from E-onset to both the prior R-wave (R-to-E) and following R-wave (E-to-R). The degree of coupling was quantified in terms of transformed relative Shannon entropy (tRSE), and χ(2) tests based on histograms of interval times from 200 breaths. Subjects were studied twice, from 5 to 27 days apart, and the test-retest reliability of CVC measures was computed. Several factors pointed to the relative importance of the R-to-I interval compared with other intervals. Coupling was significantly stronger for the R-to-I interval, coupling reliability was largest for the R-to-I interval, and only tRSE for the R-to-I interval was correlated with height, weight, and body surface area. The high test-retest reliability for CVC in the R-to-I interval provides support for the hypothesis that CVC strength is a subject trait. Across subjects, a peak ~138 ms prior to I-onset was characteristic of CVC in the R-to-I interval, although individual subjects also had earlier peaks (longer R-to-I intervals). CVC for the R-to-I interval was unrelated to two separate measures of respiratory sinus arrhythmia (RSA), suggesting that these two forms of coupling (CVC and RSA) are independent.

Uncalibrated pulse power analysis fails to reliably measure cardiac output in patients undergoing coronary artery bypass surgery

Introduction

Uncalibrated arterial pulse power analysis has been recently introduced for continuous monitoring of cardiac index (CI). The aim of the present study was to compare the accuracy of arterial pulse power analysis with intermittent transpulmonary thermodilution (TPTD) before and after cardiopulmonary bypass (CPB).

Methods

Forty-two patients scheduled for elective coronary surgery were studied after induction of anaesthesia, before and after CPB respectively. Each patient was monitored with the pulse contour cardiac output (PiCCO) system, a central venous line and the recently introduced LiDCO monitoring system. Haemodynamic variables included measurement of CI derived by transpulmonary thermodilution (CI_TPTD) or CI derived by pulse power analysis (CI_PP), before and after calibration (CI_PPnon-cal., CI_PPcal.). Percentage changes of CI (ΔCI_TPTD, ΔCI_{PPnon-cal./PPcal.}) were calculated to analyse directional changes.

Results

Before CPB there was no significant correlation between CI_PPnon-cal. and CI_TPTD (r² = 0.04, P = 0.08) with a percentage error (PE) of 86%. Higher mean arterial pressure (MAP) values were significantly correlated with higher CI_PPnon-cal. (r² = 0.26, P < 0.0001). After CPB, CI_PPcal. revealed a significant correlation compared with CI_TPTD (r² = 0.77, P < 0.0001) with PE of 28%. Changes in CI_PPcal. (ΔCI_PPcal.) showed a correlation with changes in CI_TPTD (ΔCI_TPTD) only after CPB (r² = 0.52, P = 0.005).

Conclusions

Uncalibrated pulse power analysis was significantly influenced by MAP and was not able to reliably measure CI compared with TPTD. Calibration improved accuracy, but pulse power analysis was still not consistently interchangeable with TPTD. Only calibrated pulse power analysis was able to reliably track haemodynamic changes and trends.

Relation of Arterial Properties to Left Ventricular Hypertrophy in Hypertensive Adults: Focus on Gender-Related Differences

Background: Although gender-related differences in ventricular remodeling and arterial stiffness have been described, the impact of gender on the association between vascular compliance and left ventricular hypertrophy (LVH) has not been investigated. The current study was designed to determine the gender-related differences in the association between echographically determined LVH measures and arterial stiffness in hypertensive men and women. Methods: In the current study, 104 hypertensive participants (61 men and 43 women) were enrolled. Large artery elasticity index (LAEI) and small artery elasticity index (SAEI) were determined using pulse wave contour analysis (HDI CR 2000, Eagan, Minnesota). Left ventricular hypertrophy parameters including intraventricular septum thickness (IVST), posterior wall thickness (PWT), and left ventricular mass index (LVMI) were assessed echographically. Results: Hypertensive male versus female were similar in terms of age, body mass index (BMI), blood pressure, concomitant medications, and cardiovascular risk factors. Left ventricular mass index was significantly, inversely associated with IVST (r = —.32, P = .01), PWT (r = —.32, P = .01), and LVMI (r = —.28, P = .03) in men and significantly, inversely associated with IVST (r = —39, P = .01), PWT (r = —.42, P = .005), LVMI (r = —.54, P < .0001) in women. Small artery elasticity index was significantly, inversely associated with LVMI (r = —0.36, P = .02) in women only. In regression analysis, LAEI explained more variability than SAEI and was an independent predictor of LVH parameters in hypertensive men and women. Conclusions: Compliance of large arteries is potentially an independent predictor of LVH in hypertensive men and women. Therefore, arterial compliance is being considered an important tool in predicting LVH in hypertensive participants.

Vascular compliance is reduced in geriatric people with angiographic coronary atherosclerosis

This study investigated the value of arterial elasticity measurement in the early diagnosis of angiographic coronary artery atherosclerosis in 105 consecutive elderly patients. They were divided into two groups according to the results of selective coronary angiography: 55 with coronary atherosclerosis and 50 with a normal coronary angiogram. The Gensini score of the coronary artery was acquired and capacitive arterial compliance (C1) and oscillatory arterial compliance (C2) were measured. An independent-sample t-test was used to evaluate the difference in C1 and C2 between the two groups. Bivariate analyses were performed to study the association between the Gensini score and C1 and C2. A significant difference between the two groups in C2 was found and the Gensini score of the coronary artery was significantly correlated with C2. Identification of early coronary atherosclerosis in geriatrics may be aided by the prognostic value of C2.

Vascular compliance in the cardiometabolic syndrome

Elevated systolic blood pressure and increased pulse pressure are important predictors of vascular stiffening (compliance), left ventricular hypertrophy, coronary heart disease, heart failure, stroke, vascular dementia, and chronic kidney disease. Advances in noninvasive methods that measure arterial stiffness have led to increased understanding of the mechanisms underlying vascular dysfunction and the development of associated risk factors. The ability to detect and monitor changes in the physical properties of arteries has the potential to allow early interventions that may prevent disease or attenuate its progression. In this paper, the authors briefly review the various methods available to measure vascular compliance and review pathologic processes that lead to insulin resistance, endothelial dysfunction, inflammation, and sympathetic activation, all of which may contribute to increased arterial stiffness in the cardiometabolic syndrome. Strategies to improve vascular compliance are also discussed.

Elasticity indices of large and small arteries in relation to the metabolic syndrome in Chinese

BACKGROUND

The purpose of this study was to investigate the elasticity of large and small arteries in relation to the components of the metabolic syndrome in a Chinese population.

METHODS

Arterial elasticity indices were derived from pulse wave analysis based on a modified Windkessel model in 688 subjects, aged 33-65 years, who volunteered to participate in our study.

RESULTS

The study population included 420 (61.0%) men and 433 (62.9%) hypertensive patients, of whom 197 (28.6%) took antihypertensive medication. Overall, the presence of the metabolic syndrome was 20.5%. In univariate analysis, both large artery elasticity index (C1) and small artery elasticity index (C2) were higher in men than in women (P < or = 0.008) and were inversely (P < or = 0.05) correlated with age, systolic and diastolic blood pressure (BP), pulse pressure, pulse rate, and plasma glucose concentration, and positively (P < 0.0001) correlated with body height and body weight. In men, smokers, compared with nonsmokers, had significantly lower C2 (P = 0.007), but they had similar C1 (P = 0.33). In adjusted analysis, patients with the metabolic syndrome, compared with those without, had significantly (P < 0.01) lower C1 and C2. In continuous adjusted analysis, both C1 and C2 were significantly (P < 0.0001) associated with systolic and diastolic BP, whereas in addition, C1 was also significantly associated with plasma glucose concentration (P = 0.007), and C2 with serum high-density lipoprotein (HDL) cholesterol (P = 0.02).

CONCLUSIONS

The metabolic syndrome is indeed a risk factor for reduced arterial elasticity.

Endurance running and digit ratio (2D:4D): Implications for fetal testosterone effects on running speed and vascular health

There is anatomical and physiological evidence that endurance running (ER), i.e., running one or more kilometers using aerobic metabolism, originated early in the evolution of Homo, and the consequences of early selection for ER may be important in modern Homo. Here we examine ER performance in competitive ER. ER is sex dependent such that men tend to run faster than women, and the influence of sex on ER suggests that it may be modified by testosterone (T). It is shown that a putative proxy for prenatal T, the ratio of the length of the 2nd and 4th digits (2D:4D), is correlated with ER. Thus performance in training for ER was associated with high prenatal T, as measured by low 2D:4D, in both men and women. In cross-country races from 1 to 4 miles, 2D:4D explained about 25% of the variance in both male and female ER. Therefore, speed in ER was dependent on a proxy for prenatal T. 2D:4D correlates with performance in sport and exercises, which test a mix of strength and fitness, but the associations are in general quite weak with 2D:4D accounting for less than 10% of the variance in performance. Our finding that 2D:4D explains about 25% of the variance in ER suggests that prenatal T is important in determining efficiency in aerobic exercise. Early populations of Homo may have been strongly selected for ER and high prenatal T. The implications of this for patterns of predisposition to cardiovascular disease in modern Homo are discussed.

Exercise frequency and arterial compliance in non-diabetic and type 1 diabetic individuals

BACKGROUND

The role of exercise in preventing cardiovascular disease (CVD) has been well documented. To determine whether this benefit could be related to effects on vascular endothelial function and vessel wall elasticity, thereby preserving arterial compliance, we examined the relationship between habitual exercise and arterial compliance as measured by pulse wave analysis.

DESIGN

A cross-sectional study of healthy volunteers and patients with type 1 diabetes.

METHODS

Non-diabetic individuals not taking cholesterol or blood pressure-lowering medication (n=176) and patients with type 1 diabetes (n=105), aged 17-70 years, were recruited. Small and large artery compliance and other haemodynamic variables were measured using the PulseWave CR-2000 cardiovascular profiling system. A questionnaire was completed to assess the frequency of physical activity.

RESULTS

In multivariate analysis, undertaking three or more episodes of vigorous activity per week was associated with having a 1 unit greater small artery compliance, independent of age, sex, height, diabetes status and blood pressure. The effect was especially marked in non-diabetic women.

CONCLUSIONS

The results support other findings that regular physical activity protects against CVD, through the preservation of vascular compliance.

Noninvasive Arterial Measurements of Vascular Damage in Healthy Young Adults: Relation to Coronary Heart Disease Risk

PURPOSE

There is an increasing interest in noninvasive measurements of early structural or functional changes in large arteries such as pulse wave velocity (PWV), carotid intima-media thickness (CIMT), and augmentation index (AIx). These measurements may be applied in etiologic or prognostic research. The role of the AIx as a marker of cardiovascular risk has not fully been established. Our aim was to study whether AIx is related to coronary heart disease (CHD) risk and to compare the strength of the relations of AIx, PWV, and CIMT with cardiovascular risk in healthy young adults.

METHODS

Our study included 224 men and 273 women (mean age 28 years, range 27-30 years) from the Atherosclerosis Risk in Young Adults (ARYA) study. Cardiovascular risk profile was determined and CHD risk was estimated using the Framingham risk score. AIx, PWV and CIMT were measured using standard methods. Data were analyzed in strata of gender using linear regression models.

RESULTS

In men, PWV and CIMT were most strongly related to CHD risk. The increase in CHD risk per standard deviation increase in measurement was 0.24%/m/s, 95% CI (0.01;0.33) and 0.32%/mm, 95% CI (0.08;0.55), whereas the AIx was not significantly related to CHD risk (0.09 %/% 95% CI [-0.15;0.33]). In women, AIx, PWV, and CIMT were weakly but significantly related to CHD risk; there was no clear difference between the measurements.

CONCLUSION

In young men, PWV and CIMT are better measures of CHD risk than AIx. In women, AIx, PWV and CIMT estimate CHD risk equally well.

High-fat meal impairs vascular compliance in a subgroup of young healthy subjects

Postprandial hypertriglyceridemia impairs endothelial function and may possibly worsen vascular compliance by increasing oxidative stress. Large (C1) and small (C2) artery compliance, glucose, insulin, and triglycerides (TGs) were measured hourly for 6 hours in 18 young healthy volunteers after a low-fat meal and a high-fat meal, with and without antioxidant vitamins. C1 and C2 declined significantly for 6 hours after fat ingestion in 8 subjects ("fat reactors") and increased in 10 ("nonreactors"). Fat reactors had higher fasting and peak serum TGs after fat loading and increased baseline glucose and insulin levels and homeostasis model assessment of insulin resistance (HOMA(IR)). Fasting insulin correlated with C1 and C2 only in fat reactors. After fat intake, plasma nitric oxide metabolites decreased more in fat reactors than in nonreactors (17.0% +/- 5.1% vs 4.8% +/- 2.1%; P < .05). In fat reactors, pretreatment with antioxidant vitamins before the high-fat meal blunted the fall in C1 but not in C2. Compliance was unchanged after the low-fat meal. Normal weight young subjects with an insulin resistance phenotype show significantly decreased vascular compliance, increased postprandial TG peaks, and markedly reduced plasma nitric oxide metabolites after a high-fat meal.

Diabetes is associated with dramatically decreased survival in female but not male subjects with cystic fibrosis

OBJECTIVE

Survival analysis was performed on a prospectively followed cohort of patients with cystic fibrosis (CF) to determine the impact of the development of diabetes on survival.

RESEARCH DESIGN AND METHODS

Clinical data were retrieved for patients diagnosed with CF-related diabetes (CFRD) at the Minnesota CF Center in 1987-2002. Kaplan-Meier survival analysis was performed to estimate median survival. Data were analyzed by Cox regression to evaluate the influence of clinical characteristics at the time of CFRD diagnosis on mortality.

RESULTS

Clinical information was reviewed from 1,081 CF patients. A total of 123 patients with CFRD with fasting hyperglycemia were identified (58 males). Median survival was 49.5 years for male subjects without diabetes, 47.4 years for male subjects with diabetes, 47.0 years for female subjects without diabetes, and 30.7 years for female subjects with diabetes. Only female sex and forced expiratory volume in 1 s at the time of CFRD diagnosis were significant predictors of the subsequent risk of death (P < 0.001). This strong association was not confounded by CFTR genotype, BMI, steroid use, respiratory pathogens, HbA1c, or pregnancy.

CONCLUSIONS

Female subjects with CFRD have a remarkably poorer prognosis compared with all male subjects with CF and female subjects with CF but without diabetes. The etiology of this sex difference is not clear. We speculate it might involve the interaction of female hormones and diabetes on promotion of a proinflammatory state or that androgens might protect male subjects from the catabolic effects of insulin deficiency. Alternatively, the appearance of frank diabetes in female subjects with CF may simply be a marker for some other biological difference that is not immediately apparent.

Use of lithium dilution and pulse contour analysis cardiac output determination in anaesthetized horses: a clinical evaluation

OBJECTIVE

To assess the suitability of a human algorithm for calculation of continuous cardiac output from the arterial pulse waveform, in anaesthetized horses.

STUDY DESIGN

Prospective clinical study.

ANIMALS

Twenty-four clinical cases undergoing anaesthesia for various conditions.

MATERIALS AND METHODS

Cardiac output (Qt), measured by lithium dilution (QtLiDCO), was compared with a preceding, calibrated Qt measured from the pulse waveform (QtPulse). These comparisons were repeated every 20-30 minutes. Positive inotropes or vasopressors were administered when clinically indicated. Cardiac indices from 30.7 to 114.9 mL kg(-1) minute(-1) were recorded. Unusually shaped QtLiDCO curves were rejected and the measurement was repeated immediately.

RESULTS

Eighty-nine comparisons were made between QtLiDCO and QtPulse. The bias between the mean (+/-SD) of the two methods (QtLiDCO - QtPulse) was -0.07 L minute(-1)(+/-3.08) (0.24 +/- 6.48 mL kg(-1) minute(-1)). The limits of agreement were -12.72 and 13.2 mL kg(-1) minute(-1) (Bland & Altman 1986; Mantha et al. 2000). Linear regression analysis demonstrated a correlation coefficient (r2) of 0.89. Cardiac output in individual patients varied from 49.1 to 183% of the initial measurement at the time of calibration. Linear regression of log-transformed Qt variation for each method found a mean difference of 9% with limits of agreement of -4.1 to 22.1%.

CONCLUSIONS AND CLINICAL RELEVANCE

This method of pulse contour analysis is a relatively noninvasive and reliable way of monitoring continuous Qt in the horse under anaesthesia. The ability to easily monitor Qt might decrease morbidity and mortality in the anaesthetized horse.

Relationship between DRD4 polymorphism and lipid metabolism: what is the role of novelty seeking?

OBJECTIVE

This study examined the association of the dopamine receptor D4 (DRD4) gene polymorphism with the temperament dimension of novelty seeking (NS) on cardiovascular heart disease risk factors [the levels of high-density lipoprotein (HDL) cholesterol, low-density lipoprotein (LDL) cholesterol, and triglycerides].

METHOD

From the ongoing population-based study of 'Cardiovascular Risk in Young Finns', 125 participants were DRD4 genotyped in 1997 and responded to the NS scale of the Temperament and Character Inventory in 2001. Their cholesterol and triglyceride concentrations were assessed in 2001.

RESULTS

Having a 2- or 5-allele DRD4 polymorphism was related to high HDL cholesterol levels in men, but to low HDL cholesterol levels in women. NS was related to triglycerides in men and to LDL in women, but this was mediated by behavioral, age, and weight factors, and NS was not the underlying factor for the association between the polymorphism and lipids.

CONCLUSION

Our preliminary findings suggest that there is a link between the dopaminergic receptor gene DRD4 and lipid metabolism, but this link is dependent on gender.

Hypertension: a review for clinicians

Despite the existence of a variety of consistent hypertension guidelines,the issue of inadequate management of the condition persists. The challenge for health care professionals is not only to understand and adopt the guidelines but also to take a holistic approach to patient care. In addition, clinicians need to encourage adherence to medication protocols, which will hopefully lead to an overall reduction in morbidity and mortality associated with hypertension. It is the clinician's professional responsibility to be cognizant of the emerging research on vasoactive substances as new drugs are being developed that will effect endothelial receptors. It is important that clinicians are trained appropriately in blood pressure measurement and risk factor identification and intervention.

Clinical Relevance of Retrograde Inferior Vena Cava or Hepatic Vein Opacification During Contrast-Enhanced CT

OBJECTIVE

The purpose of this investigation was to explore the clinical relevance of retrograde inferior vena cava or hepatic vein opacification during contrast-enhanced CT.

MATERIALS AND METHODS

We retrospectively identified 127 patients who underwent contemporaneous contrast-enhanced CT of the chest or abdomen and echocardiography. On CT, the presence of retrograde inferior vena cava or hepatic vein opacification and the rate of IV contrast injection (> 3 mL/sec, high; < or = 3 mL/sec, low) were recorded. On echocardiography, the presence of tricuspid regurgitation, pulmonary hypertension, or right ventricular systolic dysfunction was recorded.

RESULTS

Retrograde inferior vena cava or hepatic vein opacification was more common in studies performed with a high rather than a low contrast injection rate (28/56 vs 6/71 patients, respectively; p < 0.01). This finding was 31% sensitive (5/16) and 98% specific (54/55) for right-sided heart disease at low contrast injection rates, and 81% sensitive (17/21) and 69% specific (24/35) at high injection rates. Multivariate logistic regression models showed that high injection rate, tricuspid regurgitation, pulmonary hypertension, and right ventricular systolic dysfunction were independent predictors of retrograde inferior vena cava or hepatic vein opacification (p < 0.05 for each).

CONCLUSION

Retrograde opacification of the inferior vena cava or hepatic veins on CT is a specific but insensitive sign of right-sided heart disease at low contrast injection rates, but the usefulness of this classic sign decreases with high injection rates. This realization is important because many centers increasingly use high-injection-rate CT.

Cardiac output technologies with special reference to the horse

Critical illness, anesthesia, primary cardiovascular disease, and exercise may result in marked hemodynamic alterations. Measuring cardiac output (CO) is central to defining these alterations for both clinician and researcher. In the past 10 years, several new methods of measuring CO have been developed for the human medical market. Some of these methods are now validated in the horse and are in clinical use. The Fick method has been used in equine research for more than a century. It depends on simultaneous measurement of mixed venous (pulmonary arterial) and peripheral arterial oxygen content and oxygen uptake by the lungs. The technique is technically demanding, which restricts its clinical use. Indicator dilution techniques, with indocyanine green, cold (thermodilution), or lithium as the marker, have also been widely used in the horse. The indocyanine technique is cumbersome, and thermodilution requires right heart catheterization, which is not a benign procedure, making both of these methods less than ideal for clinical use. Lithium dilution requires catheterization of a peripheral artery and a jugular vein. It has recently been validated in anesthetized adult horses and neonatal foals. Doppler echocardiography is a noninvasive ultrasound-based technique. More accurate measurements are obtained with transesophageal than with transthoracic measurements; however, both methods require considerable technical expertise. Bioimpedance and pulse contour analysis are 2 new methods that have yet to be validated in the horse. With the currently available technology, lithium dilution appears to be the method of measuring CO best suited to the equine clinic.

Comparison of generalized and gender-specific transfer functions for the derivation of aortic waveforms

Arterial transfer functions have been promoted for the derivation of central aortic waveform characteristics not usually accessible noninvasively, but possibly of prognostic significance. The utility of generalized rather than gender-specific transfer functions has not been assessed. Invasive central aortic and noninvasive radial (Millar Mikro-tip tonometer) blood pressure waveforms were recorded simultaneously in 78 subjects (61 male and 17 female). Average transfer functions were obtained for the whole group and for each gender by two methods. Reverse transformation was performed with the use of each transfer function. Measured aortic waveform parameters were compared with those derived using average, gender-appropriate, and gender-inappropriate transfer functions. Differences in central waveform characteristics were demonstrated between men and women. Derived waveform parameters were significantly different from measured values [e.g., subendocardial viability index and augmentation index (P < 0.001)]. A gender-appropriate transfer function significantly improved the derivation of some parameters, including systolic pressure and systolic and diastolic pressure time integrals (P < 0.05). Generalized arterial transfer functions may not be universally applicable across all waveform parameters of potential interest, and gender-specific transfer functions may be more appropriate.

The effect of antihypertensive drugs on vascular compliance

Measurement of vascular compliance has assumed increasing importance as a marker of early disease of the vascular wall, a predictor of future vascular disease, and a way to monitor the effects of vasoactive agents on arterial wall stiffness. Vascular compliance can be estimated by several methods: measurement of the pulse pressure, or pulse pressure-stroke volume ratio; analysis of the systolic pulse wave augmentation index and the diastolic pulse wave contour; ultrasonic echo-tracking; and MRI. Because few comparative studies have been done, the physiologic significance of the measures of compliance obtained by each method is uncertain. Antihypertensive drugs may improve vascular compliance by reducing blood pressure, relaxing vascular smooth muscle, or promoting long-term effects on vascular smooth muscle and cardiomyocyte growth and remodeling. Angiotensin converting enzyme (ACE) inhibitors have been reported to improve vascular compliance in nearly all studies, suggesting a beneficial class effect independent of blood pressure reduction. Favorable changes in the vascular wall-lumen ratio of small vessels from subcutaneous gluteal biopsy specimens after treatment with ACE inhibitors and the persistence of improved vascular compliance after withdrawal of therapy indicate that these agents may produce long-term vascular remodeling. Although few studies have been done, angiotensin II receptor antagonists improve vascular compliance, possibly by blocking angiotensin II-mediated cell proliferation and increasing apoptosis via unopposed AT1 receptor stimulation. In contrast, calcium antagonists and beta-blockers have variable effects on vascular compliance, although beta-blockers with intrinsic sympathomimetic activity improve vascular compliance. Diuretics have little effect on vascular compliance beyond their blood pressure-lowering actions, except for spironolactone, which by improving vascular compliance may have contributed to the reduction in heart failure mortality seen in the Randomized Aldactone Evaluation Study.