Background-Cardiovagal autonomic control declines with age in adult subjects, which is related in part to increasing stiffness of the barosensory vessel wall. It is not known, however, whether autonomic function changes with age in children. Methods and Results-We studied 137 healthy subjects divided into 4 age groups: group 1, 7 to 14 years; group 2, 11 to 14 years; group 3, 15 to 18 years; and group 4, 19 to 22 years. Brachial artery pressure was measured by sphygmomanometry and continuous radial artery pressure and carotid artery pulse pressure (⌬P) by applanation tonometry. The R-R interval was derived from the ECG. Autonomic function was assessed by spontaneous sequence and frequency-domain indices, which indicate the extent of coupling between fluctuations in heart rate and systolic pressure. Carotid artery diastolic diameter (DD) and pulsatile distension (⌬D) were measured by echo wall tracking; carotid compliance coefficient (CC) was defined as ⌬D/⌬P and distensibility coefficient as 2⌬D/DD · ⌬P. , with no significant changes afterward. CC and DC were inversely proportional to age (rϭϪ0.49 and Ϫ0.62, respectively, PϽ0.001). The efficiency of neural integrative mechanisms, estimated as the ratio of spontaneous indices and CC, more than doubled from group 1 to group 3. Spontaneous indices were linearly related to measures of cardiac vagal activity. Conclusions-The increase in spontaneous indices from early childhood to adolescence, despite gradual stiffening of the carotid artery, may indicate improved cardiovagal autonomic function, which is most likely a result of maturation of neural mechanisms, attaining peak level at adolescence.

Purpose:To retrospectively assess the magnetic resonance (MR) imaging predictors of success at reducing uterine leiomyoma volume and achieving patient symptom relief 12 months after MR imaging-guided focused ultrasound surgery. Materials and Methods:This single-center retrospective analysis of 71 symptomatic fibroids in 66 women was approved by the institutional review board and was HIPAA-compliant. Patients were treated with MR imaging-guided focused ultrasound surgery. The volume of treated fibroid and nonperfused volume (NPV) were calculated with software, while symptom outcome was assessed with a symptom severity score (SSS). Fibroids were classified as hyperintense or hypointense relative to skeletal muscle on pretreatment T2-weighted MR images. Results:Baseline volume of treated fibroids was 255.5 cm 3 Ϯ 201.7 (standard deviation), and baseline SSS was 61.5 Ϯ 14.9. Both pretreatment fibroid signal intensity (SI) and posttreatment NPV predicted 12-month volume reduction independently: Fibroids with an NPV of at least 20% or with low SI both showed significantly larger volume reduction (17.0% Ϯ 13.0 and 17.2% Ϯ 20.1, respectively) than fibroids with an NPV less than 20% or with high SI (10.7% Ϯ 18.2 and no significant change, respectively). Patients whose fibroids demonstrated an NPV of at least 20% also experienced a larger decrease in SSS than did patients with fibroids with an NPV less than 20% (50.1% Ϯ 19.8 vs 32.6% Ϯ 29.9). Conclusion:Fibroids with low SI on pretreatment T2-weighted MR images were more likely to shrink than were ones with high SI. The larger the NPV immediately after treatment, the greater the volume reduction and symptom relief were. These findings may help both in selecting appropriate patients for MR-guided focused ultrasound surgery and in predicting patient outcome.

Arterial baroreflex function is altered by dynamic exercise, but it is not clear to what extent baroreflex changes are due to altered transduction of pressure into deformation of the barosensory vessel wall. In this study we measured changes in mean common carotid artery diameter and the pulsatile pressure : diameter ratio (PDR) during and after dynamic exercise. Ten young, healthy subjects performed a graded exercise protocol to exhaustion on a bicycle ergometer. Carotid dimensions were measured with an ultrasound wall-tracking system; central arterial pressure was measured with the use of radial tonometry and the generalized transfer function; baroreflex sensitivity (BRS) was assessed in the post-exercise period by spectral analysis and the sequence method. Data are given as means ± S.E.M. Mean carotid artery diameter increased during exercise as compared with control levels, but carotid distension amplitude did not change. PDR was reduced from 27.3 ± 2.7 to 13.7 ± 1.0 mm mmHg _1 . Immediately after stopping exercise, the carotid artery constricted and PDR remained reduced. At 60 min post-exercise, the carotid artery dilated and the PDR increased above control levels (33.9 ± 1.4 mm mmHg _1 ). The post-exercise changes in PDR were closely paralleled by those in BRS (0.74 ≤ r ≤ 0.83, P < 0.05). These changes in mean carotid diameter and PDR suggest that the mean baroreceptor activity level increases during exercise, with reduced dynamic sensitivity; at the end of exercise baroreceptors are suddenly unloaded, then at 1 h post-exercise, baroreceptor activity increases again with increasing dynamic sensitivity. The close correlation between PDR and BRS observed at post-exercise underlies the significance of mechanical factors in arterial baroreflex control.

Systemic arterial compliance has been known to increase during healthy pregnancy, whereas, recently, the carotid artery has been reported to stiffen. To clarify this controversy, we simultaneously measured aortic PWV (pulse wave velocity) and carotid artery elastic parameters in a cohort of pregnant women. Twelve normotensive pregnant women were studied longitudinally during the three trimesters of pregnancy (T1, T2 and T3 respectively) and 12 weeks PP (postpartum). Carotid artery diastolic diameter and pulsatile distension was measured by an echo-wall tracking method and carotid pulse pressure by applanation tonometry. Carotid strain, compliance, distensibility coefficient, stiffness index beta, Einc (incremental elastic modulus) and augmentation index were calculated. Aortic PWV was determined to estimate aortic distensibility. All carotid artery elastic parameters indicated significant stiffening from T1 to T3 (1.8+/-0.2 versus 2.9+/-0.3 mmHg for Einc), which was reversed after delivery (2.3+/-0.2 mmHg). Aortic PWV decreased during pregnancy (6.2+/-0.2 versus 5.4+/-0.2 m/s) and increased in the PP period (6.7+/-0.2 m/s). No correlation was found between changes in carotid artery elastic parameters and changes in aortic PWV either from T1 to T3 or from T3 to PP. The carotid artery exhibits regionally specific stiffening during pregnancy, which appears to represent a qualitatively different change in arterial elastic behaviour.

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.

Arterial baroreflex sensitivity (BRS) is markedly reduced in middle-aged patients with end-stage renal disease (ESRD), due to the combined effects of aging, arterial stiffening, and autonomic neuropathy. Much less is known about the effects of ESRD on arterial baroreflex in juvenile patients. Therefore, we investigated baroreflex function and its relation to carotid artery elasticity and heart rate variability in children and young adults with ESRD. We studied 42 subjects (9-30 years): 14 patients on maintenance hemodialysis (HD), 14 renal transplant recipients (RT), and 14 healthy control subjects (C). Baroreflex function was determined by pharmacological (BRS) and spontaneous (sequence and spectral indices) techniques. Carotid artery elasticity was characterized by stiffness index beta. Heart rate variability was assessed using time and frequency domain measures. Data are expressed as mean+/-s.d. BRS was markedly reduced in HD as compared to C (10.0+/-4.2 vs 25.7+/-5.9 ms/mm Hg); spontaneous indices were reduced to similar extent. Carotid artery stiffness was approximately 50% higher in HD than in C and was inversely related to BRS. Heart rate variability was also compromised in HD, and was directly related to spontaneous indices. No significant differences existed in any of these variables between RT and C. Decreased baroreflex function in juvenile HD is partly due to loss of carotid artery elasticity and partly due to impaired heart rate variability. Renal transplantation may partly prevent impairment or improve compromised baroreflex function in young patients with ESRD.

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.

Abstract-Transposition of great arteries is the consequence of abnormal aorticopulmonary septation. Animal embryonic data indicate that septation and elastogenesis are related events, but human and clinical data are not available. We tested the hypothesis that large artery elastic function was impaired in patients with transposition of great arteries. We studied 34 patients aged 9 to 19 years, 12Ϯ3 years after atrial switch operation; 14 patients aged 7 to 9 years, 8Ϯ1 years after arterial switch operation; and 108 healthy control subjects matched for age. Carotid artery diastolic diameter and pulsatile distension were determined by echo wall-tracking; carotid blood pressure was measured by tonometry. Systolic pressure was higher and diastolic pressure was lower in patients than in controls. Patients with atrial and arterial switch repair were compared with their respective controls by 2-factor ANOVA. For patients with atrial switch repair versus control, stiffness index ␤ was 4.9Ϯ1.5 versus 3.1Ϯ1.0 (PϽ0.001); for patients witch arterial switch versus control, stiffness index ␤ was 3.8Ϯ1.1 versus 2.1Ϯ0.6 (PϽ0.001). Similar differences were observed for carotid compliance, distensibility, and incremental elastic modulus as well.The interaction term was not significant for any of the elastic variables, indicating that carotid stiffening was a characteristic of the condition and not the consequence of different hemodynamics. Carotid artery is markedly stiffer in patients, suggesting that impaired elastogenesis may constitute part of the congenital abnormality. Since carotid artery stiffness has been established as an independent cardiovascular risk factor, this condition may have consequences in the clinical management of these patients. Key Words: carotid arteries Ⅲ arteries Ⅲ elasticity T ransposition of great arteries (TGA) is a severe congenital heart defect in which the aorta arises from the right ventricle and the pulmonary artery from the left ventricle. TGA is the consequence of abnormal aorticopulmonary septal development. In animal models it has been demonstrated that great vessel elastogenesis was related to aorticopulmonary septation. 1,2 Neural crest cells in the avian embryo, which form the septum, also synthesize the elastogenic matrix of the large vessel wall. 1 We hypothesized that elastogenesis and aorticopulmonary septation were related events in human subjects as well; therefore, we compared the elastic parameters of the common carotid artery, a representative of large elastic arteries, in TGA patients and in age-matched control subjects to investigate whether impairment of large artery elastic function constituted part of congenital abnormality.