Zsuzsanna Visontai

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⩽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.

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 ± 2.1·10^–3·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· 10^–3·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.

Decreased cardiovagal regulation in exfoliation syndrome.

PurposeTo investigate the parasympathetic cardiovascular regulation, baroreflex sensitivity (BRS), and pulse wave velocity (PWV) in exfoliation syndrome (XFS). MethodsHeart rate variability indices [standard deviation of all RR intervals (SDNN); the mean of absolute successive differences (RMSSD); the percentage of intervals differing by >50 ms from the preceding interval (pNN50); low frequency power, and high frequency power], as well as BRS and PWV, were determined on 27 consecutive white XFS patients and 20 white control subjects under standard circumstances, with controlled breath rate of 0.25 Hz. The paired t test, the Mann-Whitney U test, and the Fisher exact test were used for comparisons. ResultsThere was no significant difference between the XFS and control groups in sex distribution, age, heart rate, blood pressure, body mass index, systemic diseases, or medication. But in XFS patients, SDNN (mean±SD, 24±7.3 vs. 49±16.5 ms), RMSSD (17±7.3 vs. 45±29.1 ms), pNN50 (1.6%±2.5% vs. 17.7%±25.9%), high frequency (112±109 vs. 479±554 ms2), and BRS (4.64±2.12 vs. 9.49±4.76 ms/mm Hg for BRS+ and 5.28±2.16 vs. 10.29±4.62 ms/mm Hg for BRS−) were all significantly lower than in the control group (P<0.01 for each parameter). Low frequency was also reduced in XFS (72±55 vs. 253±241 ms2) (P=0.027). In XFS, PWV was significantly increased compared with the control group (11.6±4.1 vs. 9.3±2.2 m/s) (P=0.023). DiscussionOur results suggest a clinically and statistically significant impairment of cardiovagal regulation and impairment of conduit artery function in XFS patients.

Carotid artery elasticity and baroreflex sensitivity in patients with glaucoma.

Purpose:To investigate non-invasively the elasticity of common carotid artery and the arterial baroreflex function in patients with chronic open-angle glaucoma. Patients and Methods:Data were obtained from patients with chronic open-angle glaucoma (n = 16) [primary open angle- and juvenile open-angle glaucoma] and from age- and sex-matched healthy control subjects (n = 18). End diastolic diameter and pulsatile distension of the common carotid artery were measured with a high-precision, automated ultrasound wall-tracking system (WTS). Spontaneous fluctuation in cardiac interval and systolic pressure were used to determine baroreflex sensitivity. Results:There was no difference in heart rate and pulse pressure between patients with glaucoma and the control subjects. In the glaucoma patients both distensibility coefficient of common carotid artery and baroreflex sensitivity were reduced (two-way factorial ANOVA; P < 0.002). Stiffness (characterizing the rigidity of vessel wall) was higher in the glaucoma patients than in the controls (P = 0.002). Conclusions:Our results suggest that in patients with chronic open-angle glaucoma the arterial rigidity is significantly increased and therefore the baroreflex function is significantly decreased. These findings may have relevance in the understanding of the autonomic dysfunction and vascular dysregulation in glaucoma.

Carotid artery stiffening does not explain baroreflex impairment in pre-eclampsia

Stiffening of the barosensory vessel wall in hypertension has been suggested to play a role in the associated baroreflex impairment. The carotid distensibility-BRS (baroreflex sensitivity) relationship, however, has not been studied in pre-eclampsia, a condition where hypertension is spontaneously reversible. Twelve normotensive pregnant women and 12 patients with pre-eclampsia matched for maternal age and week of gestation were studied in the third trimester and 3 months postpartum. Carotid artery diastolic diameter and pulsatile distension was measured by echo-wall tracking and carotid pulse pressure by applanation tonometry, and the carotid distensibility coefficient was calculated. Spontaneous BRS was determined by the sequence and spectral methods from 10 min continuous recording of ECG and finger arterial blood pressure. In the third trimester, carotid distensibility was lower in patients with pre-eclampsia than in normotensive pregnant women (2.47+/-0.17 compared with 4.08+/-0.16 x 10(-3)/mmHg); postpartum, it increased moderately in patients, but remained below normotensive values (3.25+/-0.12 compared with 4.25+/-0.19 x 10(-3)/mmHg). In the third trimester, both patients and healthy pregnant women had equally low BRS values; postpartum, the various BRS indices increased markedly (by 60-190%) and to the same level in both groups. No correlation was found between changes in carotid artery distensibility and those in BRS from the third trimester to postpartum period in patients and healthy pregnant women. The lack of association between changes in carotid distensibility and BRS suggest that stiffening of the carotid artery in pre-eclampsia is not responsible for baroreflex dysfunction.

Reduced Baroreceptor Sensitivity and Elasticity of the Carotid Artery in a Preeclamptic Patient

Baroreflex sensitivity, distensibility coefficient, and intima-media thickness (IMT) of the common carotid artery were determined in a preeclamptic patient during 1st and 3rd trimesters as well as after childbirth. From the beginning of her pregnancy, baroreflex sensitivity and distensibility coefficient of the carotid artery exhibited a parallel decline, whereas the IMT increased as compared with normotensive pregnancies. The values of all parameters examined returned to their initial levels after 14 weeks of delivery. These results suggest that augmented IMT and carotid stiffness coupled to baroreceptor dysfunction may have contributed to the perturbation of blood pressure control in our preeclamptic patient.

Unoprostone Isopropyl Pretreatment Decreases Endothelin-1 Release and the Intra-Ocular Pressure Spike Induced by Laser Trabeculoplasty in the Rabbit

Purpose: We have previously shown that the intra-ocular pressure (IOP) spike due to argon laser trabeculoplasty (ALT) is caused by an acute endothelin-1 (ET-1) release from the uveal tissue into the aqueous humour of rabbit eyes. In this study we investigated whether pretreatment with topical unoprostone isopropyl, a functional antagonist of ET-1, protects against the pressure spike due to ALT in the rabbit model. Methods: IOP of both eyes of 17 pigmented rabbits was measured with a TonoPen XL tonometer under general anaesthesia (baseline measurement). Then the right eyes were treated with topical unoprostone isopropyl 0.12% BID for 6 days, and the left eyes similarly received balanced salt solution (BSS) twice daily. After the last morning instillation, IOP for both eyes was measured under general anaesthesia after 2 h in group 1 and after 3 h in group 2 animals. Then, for both groups, ALT was performed on both eyes. Thirty minutes after laser treatment (and still under general anaesthesia), IOP was measured again. Then the aqueous humour was aspirated for measurement of ET-1 concentration. Results: Baselineindividual IOP differences (left eye minus right eye) were not significant in both groups: mean ± SD 0.25 ± 1.16 and –0.33 ± 0.71 mm Hg, respectively (paired t test, p > 0.05 for both groups). On day 6, 2 h (group 1) and 3 h (group 2) after the last instillation but before laser trabeculoplasty, the difference (BSS-pretreated left eye minus unoprostone-pretreated right eye) increased to 2.13 ± 2.10 mm Hg (p = 0.024) and 1.33 ± 0.71 mm Hg (p = 0.0005), respectively. Thirty minutes after ALT, the IOP difference was 2.63 ± 2.67 mm Hg in group 1 (p = 0.027), but no difference was seen in group 2 (0.67 ± 1.94 mm Hg, p = 0.332). In group 1, postoperative aqueous humour ET-1 concentration for the unoprostone-pretreated right eye was significantly lower than that for the BSS-pretreated left eye (paired t test, p = 0.01); but in group 2 no inter-ocular difference in ET-1 concentration was found (p = 0.976). Conclusion: Topical unoprostone pretreatment decreases laser-induced ET-1 release and diminishes the IOP spike caused by ALT in vivo within 2 h after instillation, when the concentration of unoprostone in the aqueous humour is high.