Increase of carotid artery stiffness and decrease of baroreflex sensitivity in exfoliation syndrome and glaucoma.

AIM: To investigate the distensibility of the common carotid artery (CCA), baroreflex sensitivity (BRS) and its relation to plasma homocysteine concentration in exfoliation syndrome or exfoliation glaucoma (XFS/XFG). METHODS: Homocysteine concentrations were measured in 30 XFS/XFG patients and 18 age matched controls. In 21 patients and 17 controls the end diastolic diameter of the CCA and pulsatile distension were measured and BRS was calculated. RESULTS: There was no significant difference between the groups in sex distribution, age, heart rate, blood pressure, systemic diseases, or medication. In XFS/XFG patients homocysteine concentration was significantly elevated (unpaired t test, p = 0.023), and CCA stiffness was higher (p<0.05), while strain, cross sectional compliance coefficient, distensibility, and BRS were significantly reduced compared to the controls (Mann-Whitney U test, p< or =0.013 for each parameter). In XFS/XFG patients a positive correlation was found between age and plasma homocysteine level (Pearson's correlation, r = 0.490, p = 0.007), and a negative correlation between age and BRS (Kendall's correlation r = -0.374, p = 0.021), as well as between homocysteine concentration and BRS (Kendall's correlation r = -0.377, p = 0.024). No correlation was seen between these variables in the control group. CONCLUSIONS: These results suggest a pathological large artery function as well as altered parasympathetic vascular control in XFS/XFG which increases with age and with higher homocysteine concentration.

Impaired baroreflex function during pregnancy is associated with stiffening of the carotid artery.

OBJECTIVE: The baroreflex sensitivity and the distensibility of the carotid artery were measured during normotensive pregnancy to test the hypothesis that changes in baroreflex sensitivity are related to carotid artery stiffening. DESIGN: Data were obtained from pregnant subjects during each trimester (T1, T2, T3; n = 23) and postpartum (n = 11). End-diastolic diameter and pulsatile distension of the carotid artery were measured with an ultrasound wall-tracking system, and the distensibility coefficient was calculated. Spontaneous fluctuations in cardiac interval and systolic pressure were used to determine baroreflex sensitivity. RESULTS: Both distensibility coefficient and baroreflex sensitivity were reduced from T1 to T3 (5.1 +/- 1.6 vs. 3.7 +/- 0.9 10(-3)/mmHg and 10.1 +/- 2.9 vs. 5.7 +/- 1.8 ms/mmHg, respectively). Baroreflex sensitivity and carotid distensibility coefficient were linearly related in each subject (r = 0.62 +/- 0.12). Augmentation index and return time changes indicated a global increase in arterial distensibility. CONCLUSIONS: Stiffening of the carotid artery significantly contributes to the impairment of baroreflex sensitivity during pregnancy, and represents a region specific change as global arterial distensibility was found to increase during pregnancy.

Static versus dynamic distensibility of the carotid artery in humans.

In clinical studies, the elastic behavior of central arteries is usually assessed by measuring dynamic distensibility. In this study, we aimed to investigate how dynamic and static distensibility of the common carotid artery (D(dyn) and D(stat), respectively) are related in 28 healthy volunteers of 20-71 years. The carotid diameter and its change with the pressure pulse were measured using an ultrasound echo-tracking device. Arterial blood pressure was measured by Finapres and carotid pressure was determined by applanation tonometry. D(dyn) was determined at rest using the pressure pulse, while D(stat) was determined during pressor responses induced by handgrip or cold pressor test. Data are given as mean +/- 1 SD. In younger subjects (<35 years), D(stat) did not differ from D(dyn) (7.0 +/- 3.4 vs. 6.5 +/- 2.1 x 10(-3) x mm Hg(-1), respectively), whereas in older subjects (>35 years), D(stat) was significantly higher than D(dyn) (3.8 +/- 1.4 vs. 2.1 +/- 0.9 x 10(-3) x mm Hg(-1), p < 0.001). For all subjects, D(stat) and D(dyn) decreased with increasing age and mean arterial pressure (MAP). Using stepwise multiple regression analysis, the strongest predictor of D(stat) proved to be MAP, while that of D(dyn) was age. D(stat) was found to be linearly related to the hysteresis loop area of the pressure-diameter relation (r = 0. 94), i.e. to vessel wall viscosity. It is concluded that, with increasing age, static distensibility overestimates the distension capacity of large arteries.

Assessment of the viscosity of the pulmonary artery wall.

Large artery wall viscosity reduces the efficiency of heart/vessel coupling. The aim of the present study was to assess pulmonary artery wall viscosity through comparison of the static (Dst) and dynamic distensibility (Ddyn) of the vessel wall. Right pulmonary artery pressure and diameter was measured in 13 patients and eight healthy volunteers. Ddyn was calculated as the relative change in end-diastolic diameter induced by the pressure pulse, and Dst as the relative change in mean diameter induced by the change in mean pressure during steady-state exercise. Dst did not differ significantly from Ddyn (mean+/-SD 22.8+/-19.2 versus 21.0+/-18.3 10(-3) mmHg(-1)), as tested by paired t-test and analysis of covariance, with age as covariant. End-diastolic diameter increased, whereas Dst and Ddyn decreased as a function of age (r=-0.69 and -0.67, respectively; p<0.01 for both). Ddyn did not change from rest to exercise in spite of a 23+/-16-beats-min(-1) increase in cardiac frequency. Pulmonary artery wall viscosity was negligible and no increase in wall viscosity occurred during cardioacceleration.

[The role of vascular nitric oxide (NO) in the pathomechanism of pre-eclampsia]. / A vascularis nitrogén-oxid (NO) szerepe a praeeclampsia patomechanizmusában.

The significance of nitric-oxide as a biological mediator is increasingly elucidated in various physiological processes. In addition to the endothelium dependent vasodilator effect it also plays an important role as a neurotransmitter. Possible synthesis of endothelial nitric-oxide is an essential factor in the regulation of blood pressure and utero-placental circulation. Recently the relationship of nitric-oxide and preeclampsia has extensively been studied. The results of human studies and animal experiments suggest that insufficient production of endothelial nitric-oxide probably has an important role in the pathomechanism of preeclampsia.