Biomedical subjects

Sandrine C Millasseau

Publications and source records attributed to Sandrine C Millasseau.

10 recordsLinked to original sources

PubMed2006

Non-invasive assessment of endothelial function: which technique?

OBJECTIVES: The purpose of this study was to compare 3 non-invasive techniques for assessment of endothelial function in adults and children and evaluate their utility in acute inflammation. BACKGROUND: Endothelial dysfunction is a key early event in pre-clinical atherosclerosis. Flow-mediated dilation (FMD), although the established technique, is expensive and technically demanding. Measurements of vascular responses to inhaled salbutamol by pulse wave analysis (PWA) or pulse contour analysis (PCA) are potential alternatives. METHODS: Sixteen adults (mean age 28 years, range 18 to 39) and 16 children (mean age 13 years, range 7 to 17) underwent concurrent vascular function testing on 2 occasions with ultrasound, PWA, and PCA. Eighteen men were also studied before and after typhoid vaccination. RESULTS: Reproducibility of FMD was high in adults and children (coefficient of variation [CV] = 7.1 and 6.3, respectively). Salbutamol responses were more variable with PWA (adults CV = 11.5, children CV = 17.1) and PCA particularly in children (adults CV = 18.2, children CV = 36.3). Flow-mediated dilation (p < 0.001) and PWA with salbutamol (p = 0.03) responses fell after typhoid vaccination, and PCA (p = 0.7) was unchanged. CONCLUSIONS: Vascular dysfunction during acute inflammation can be measured by FMD and by PWA with salbutamol. Flow-mediated dilation is less variable than PWA. Variability of PCA makes this technique currently unsuited to serial measures of endothelial function in children. Flow-mediated dilation remains the most reproducible method.

Adolescent↗

PubMed2006

Acute reduction of blood pressure by nitroglycerin does not normalize large artery stiffness in essential hypertension.

Stiffness of large elastic arteries is elevated in subjects with hypertension, an effect that could potentially be explained by increased distending pressure. We examined effects of an acute change in blood pressure on carotid-femoral pulse wave velocity and carotid artery distensibility (inversely related to stiffness) in normotensive control subjects (n=20, mean age 42) with mean arterial pressure (MAP) 84+/-1.7 mm Hg (mean+/-SE) and subjects with essential hypertension (n=20, mean age 45, MAP 104+/-2.0 mm Hg). Normotensive subjects received intravenous nitroglycerin (NTG) and angiotensin II to lower/increase blood pressure. Hypertensive subjects received NTG to lower blood pressure. Pulse wave velocity was 24% (95% CI: 12% to 35%) higher and carotid distensibility 47% (95% CI: 32% to 63%) lower in hypertensive subjects compared with controls. In normotensive subjects, acute changes in blood pressure produced expected changes in stiffness. However, in hypertensive subjects, despite reducing MAP by 22 mm Hg to the same level as in normotensive subjects, there was no detectable reduction in arterial stiffness: pulse wave velocity remained 24% (95% CI: 10% to 38%) higher and carotid distensibility 48% (95% CI: 31% to 63%) lower in hypertensive compared with normotensive subjects. Because blood pressure-independent effects of NTG are, if anything, to reduce stiffness, these results indicate that elevated carotid and aortic stiffness in hypertensive subjects is not explained by elevated blood pressure but relates to structural change in the arterial wall.

Adult↗

PubMed2006

Aldosterone and left ventricular hypertrophy in Afro-Caribbean subjects with low renin hypertension.

BACKGROUND: Activity of the renin-angiotensin-aldosterone system is thought to play a major role in determining blood pressure (BP) and target organ damage such as left ventricular hypertrophy. In Afro-Caribbean subjects, however, hypertension tends to be more severe despite lower plasma renin activity. We investigated whether this might be due to a different relation between aldosterone and renin in Afro-Caribbean compared to white subjects. METHODS: Plasma aldosterone and renin activity were assessed in the morning after 15 min seated in 383 hypertensive subjects of Afro-Caribbean or white ethnicity (61% Afro-Caribbean, 83% on treatment) attending a hypertension clinic in London, UK. Left ventricular mass index (LVMI) was assessed by echocardiography in 276 subjects. RESULTS: Plasma renin activity was lower in Afro-Caribbean compared to white subjects (0.4 [0.3-1.0] v 1.4 [0.5-3.4] ng/mL/h, medians [interquartile range], P < .0001). Despite this, aldosterone was higher in Afro-Caribbean compared to white subjects (8.0 [6.1-12.6] v 7.4 [2.3-17.1] ng/dL, medians [interquartile range], P < .01). The LVMI corrected for sex and BP was higher in Afro-Caribbean than in white subjects. In Afro-Caribbean but not in white subjects LVMI was independently correlated with plasma aldosterone (standardized regression coefficient, beta= 0.25, P < .001). CONCLUSIONS: In Afro-Caribbean hypertensive subjects in London, plasma aldosterone is elevated despite lower renin and may contribute to increased severity of hypertension and left ventricular hypertrophy in Afro-Caribbean compared to white subjects.

Adult↗

PubMed2006

Contour analysis of the photoplethysmographic pulse measured at the finger.

Analysis of the contour of the peripheral pulse to assess arterial properties was first described in the nineteenth century. With the recognition of the importance of arterial stiffness there has been a resurgence of interest in pulse wave analysis, particularly the analysis of the radial pressure pulse acquired using a tonometer. An alternative technique utilizes a volume pulse. This may conveniently be acquired optically from a finger (digital volume pulse). Although less widely used, this technique deserves further consideration because of its simplicity and ease of use. As with the pressure pulse, the contour of the digital volume pulse is sensitive to changes in arterial tone induced by vasoactive drugs and is influenced by ageing and large artery stiffness. Measurements taken directly from the digital volume pulse or from its second derivative can be used to assess these properties. This review describes the background to digital volume pulse contour analysis, how the technique relates to contour analysis of the pressure pulse, and current and future applications.

Blood Pressure↗

PubMed2005

Evaluation of carotid-femoral pulse wave velocity: influence of timing algorithm and heart rate.

Carotid-femoral pulse wave velocity (PWV), a measure of arterial stiffness, is determined from the time taken for the arterial pulse to propagate from the carotid to the femoral artery. Propagation time is measured variously from the foot of the waveform or point of maximum upslope. We investigated whether these methods give comparable values of PWV at rest, during beta-adrenergic stimulation, and pacing-induced tachycardia. In subjects at rest (n=43), values obtained using the foot-to-foot method (SphygmoCor system) were 1.7+/-0.75 m/s (mean+/-SD) greater than those obtained using the maximum slope (Complior system) at a mean value of 12 m/s. Isoprotenerol (0.5 to 1.5 microg/min; n=10), and pacing (in subjects with permanent pacemakers; n=11) increased heart rate but had differential effects on systolic blood pressure and pulse pressure. The increase in heart rate produced by isoprotenerol (18+/-3 bpm) and pacing (40 bpm) was associated with an increase in PWV measured using both systems (increases of 0.7+/-0.2 m/s and 0.9+/-0.2 m/s for SphygmoCor and Complior, respectively, during isoprotenerol and increases of 2.1+/-0.5 m/s and 1.1+/-0.2 m/s for SphygmoCor and Complior, respectively, during pacing, each P<0.001). Reanalysis of waveforms recorded from the Complior system using the foot-to-foot method produced similar values of PWV to those obtained with the SphygmoCor, confirming that the difference between these systems was attributable to the timing algorithm rather than other aspects of signal acquisition. Carotid-femoral PWV is critically dependent on the method used to determine propagation time, but this does not account for variation of PWV with heart rate.

Adrenergic beta-Agonists↗

PubMed2005

Association of pulse waveform characteristics with birth weight in young adults.

OBJECTIVE: An association between birth weight and blood pressure has been reported in many studies, but the strength of this association has been disputed. Birth weight could, however, be associated with alterations in the proximal arterial tree that have little effect on blood pressure. The objective of this study was to examine the relationship between birth weight and characteristics of the proximal arterial tree determined by pulse wave analysis. METHODS: An optically derived digital volume pulse was used to obtain indices of pressure wave reflection (reflection index; RI) determined by characteristics of small/medium sized arteries and of large artery stiffness (stiffness index; SI) in healthy young adults (n = 220, 111 women, aged 16-26 years). Birth weight was obtained from maternal recall. RESULTS: Diastolic blood pressure was significantly correlated with birth weight (P < 0.001) but birth weight accounted for only 5% of the variance in diastolic blood pressure. RI was significantly correlated with birth weight in women (r = -0.33, P < 0.001) but not in men, and there was a significant interaction between birth weight and sex (P < 0.001). SI was significantly independently correlated with birth weight in both men and women (r = -0.41 and -0.49, each P < 0.0001) and birth weight accounted for 17% of the overall (men and women) variance in SI. CONCLUSIONS: These results suggest a close association between birth weight and characteristics of the arterial tree proximal to resistance vessels in young adults and a sex-specific association with characteristics influencing arterial pressure wave reflection.

Adolescent↗

PubMed2004

Sex differences in age-related stiffening of the aorta in subjects with type 2 diabetes.

Hypertension and type 2 diabetes are associated with increased aortic pulse wave velocity (PWV), a measure of aortic stiffness and a powerful risk factor for cardiovascular events. The association of hypertension with type 2 diabetes may obscure the degree to which diabetes rather than hypertension contributes to an elevated PWV. The objective of this study was to determine whether the presence of type 2 diabetes is associated with an elevated PWV compared with nondiabetic subjects matched for mean arterial blood pressure. PWV was determined by measuring carotid to femoral transit time using applanation tonometry in 186 subjects (104 women) with (n=93) and without (n=93) type 2 diabetes. Diabetic and nondiabetic subjects were matched for age and mean arterial pressure (to +/-5 years and 5 mm Hg, respectively). PWV was strongly correlated with age and mean arterial blood pressure (R=0.59 and 0.29 respectively, each P<0.0001). PWV increased significantly more with age in women with diabetes (slope of regression line+/-SE: 0.19+/-0.03 m x s(-1) x year(-1)) than in nondiabetic women (0.08+/-0.02 m x s(-1) x year(-1), P<0.01 for difference). In men, however, the age-related increase in PWV was similar in diabetic (0.15+/-0.03 m x s(-1) x year(-1)) and nondiabetic subjects (0.13+/-0.03 m. s(-1) x year(-1), P=NS). The interaction of diabetic status with age and with sex was significant (P=0.01). Type 2 diabetes is associated with a greater age-related stiffening of the aorta in women compared with men, and this is not explained by hypertension.

Adult↗

PubMed2003

Effects of inhibition of basal nitric oxide synthesis on carotid-femoral pulse wave velocity and augmentation index in humans.

Aortic stiffness, as measured by carotid-femoral pulse wave velocity (PWV), is a powerful, independent predictor of vascular risk. PWV in muscular arteries is influenced by basal nitric oxide (NO) release. It is not known whether NO also influences carotid-femoral PWV. We examined the effects of an NO synthase inhibitor, NG-monomethyl-l-arginine (L-NMMA), on carotid-femoral PWV and aortic augmentation index (AIx, an indirect measure of arterial stiffness). To control for effects of L-NMMA on distending pressure, we used doses of norepinephrine and dobutamine that caused similar changes in mean arterial blood pressure (MAP). Healthy men (32 to 48 years old, n=8) were studied on 4 occasions and received, in random order, vehicle, L-NMMA (3 mg x kg(-1) by intravenous bolus followed by 3 mg x kg(-1) x h(-1)), norepinephrine (50 ng x kg(-1) x min(-1)), and dobutamine (2.5 to 10 microg x kg(-1) x min(-1)), each for 30 minutes. PWV and AIx were measured by carotid-femoral PWV and radial tonometry, respectively. L-NMMA and norepinephrine increased MAP by 7.8+/-1.7 and 9.7+/-2.1 mm Hg, respectively (each P<0.05 vs vehicle) and increased PWV by 0.7+/-0.2 and 1.0+/-0.3 m x s(-1) (each P<0.01 vs vehicle). Dobutamine, at doses that produced a similar increase in MAP (9.6+/-2.9 mm Hg), increased PWV by 0.8+/-0.2 m x s(-1) (P<0.01 vs vehicle). Changes in PWV caused by the 3 pressor agents were closely correlated with changes in MAP (R>0.99, P<0.0001). L-NMMA and norepinephrine increased AIx, but dobutamine decreased AIx (P<0.01 vs norepinephrine and L-NMMA). Effects of inhibition of basal NO release on carotid-femoral PWV can be explained by the change in MAP that this causes rather than any specific effect of NO inhibition within the aorta.

Adult↗

PubMed2003

Pressure wave reflection assessed from the peripheral pulse: is a transfer function necessary?

Synthesis of the aortic pressure waveform by application of a transfer function to the radial pulse allows the estimation of aortic systolic blood pressure and aortic augmentation index, an index of pressure wave reflection derived from the early systolic component of the waveform. The accuracy of this approach for determining the aortic augmentation index has been questioned, however, and it may be possible to derive similar information without using a transfer function. We compared aortic systolic blood pressure and the aortic augmentation index obtained from carotid and radial arteries with the use of transfer functions. We examined the correlation between the aortic augmentation index and a radial augmentation index obtained without use of a transfer function. Arterial tonometry (Sphygmocor) was performed in 84 subjects including healthy volunteers (n=30), subjects with essential hypertension (n=30), and patients with coronary artery disease (n=24). Effects of nitroglycerine and norepinephrine on aortic and radial augmentation index were examined in 12 healthy volunteers. Values of aortic systolic pressure obtained from radial and carotid arteries by using transfer functions were in acceptable agreement (R=0.98, difference=-0.9+/-4.6 mm Hg; mean+/-SD, n=84), but those of aortic augmentation index differed especially in control subjects (R=0.47, difference=-3.8+/-12.4%). Aortic augmentation index was, however, closely correlated with radial augmentation index (R=0.96, n=84). Nitroglycerine and norepinephrine produced parallel changes in the aortic and radial augmentation index. Our findings question the use of a transfer function to obtain the aortic augmentation index but suggest that similar information on central pressure wave reflection can be obtained directly from the radial pulse.

Adult↗

PubMed2003

The vascular impact of aging and vasoactive drugs: comparison of two digital volume pulse measurements.

BACKGROUND: Indices of pressure wave reflection (RI(DVP)) and large artery stiffness (SI(DVP)) can be derived from the digital volume pulse (DVP). Indices obtained from the second derivative of the DVP have also been proposed to characterize vascular aging and effects of vasoactive drugs. METHODS: We compared RI(DVP) and SI(DVP) with the indices a/b, a/c, a/d, and a/e calculated from sequential peaks of the second derivative of the DVP in 124 healthy men. The DVP was obtained by measuring infrared light transmission through the finger. In 10 men measurements were obtained at baseline and during intravenous infusion of glyceryl trinitrate (GTN, 3 to 300 microg/min) and, on separate occasions, angiotensin II (AII, 75 to 300 microg/min) and saline vehicle. RESULTS: SI(DVP) was strongly associated with age (R = 0.63, P <.001) but little influenced by AII or GTN. RI(DVP) was weakly associated with age but showed a consistent dose-dependent increase during AII and a decrease during GTN. d/a was strongly associated with age (R = -0.66, P <.001), influenced by vasoactive drugs but did not change in a dose-dependent manner during GTN. Other second derivative indices were less strongly correlated with age and showed an inconsistent response to vasoactive drugs. Within subject standard deviations of SI(DVP) and d/a for measurements on different occasions were 2.1 and 5.4 "years of vascular aging" respectively. CONCLUSIONS: In healthy men, RI(DVP) may be a more reliable index of the effects of vasoactive drugs than d/a. SI(DVP) is similarly associated with age as is d/a, but less variable and may thus be a better index of vascular aging.

Adult↗