Arterial Stiffening Influence of Sympathetic Nerve Activity

Abstract

Abstract-Studies in animals and humans suggest that sympathetic activity exerts a stiffening influence on large and middle-sized artery walls. We sought to obtain further evidence on this issue by measuring radial artery distensibility in an allotransplanted and thus denervated hand using the contralateral artery as control. In 2 men, blood pressure was measured by a semiautomatic device (Dinamap). Diastolic diameter, systo-diastolic diameter excursion (ultrasound Wall Track system), and distensibility (Reneman formula) of both radial arteries were measured at a level corresponding to 4 cm below the suture of the transplanted hand 40 days after surgery and every 4 weeks for the next 6 months. After surgery, systo-diastolic diameter excursion and distensibility were much greater in the transplanted radial artery than in the contralateral vessel, reaching values similar to the contralateral ones after 4 months, when signs of reinnervation of the transplanted hands had appeared. Radial deinnervation was accompanied by an increased arterial distensibility, which provides further evidence of the sympathetic stiffening effect on arterial wall in humans. Key Words: denervation Ⅲ sympathetic nervous system Ⅲ transplantation S ympathetic nerve activity exerts a "tonic" stiffening influence on arterial wall. 1,2 This has been shown in animals in which chemical sympathectomy was accompanied by an increase in carotid artery distensibility. 3 It has also been shown in humans in whom anesthesia of the brachial plexus and anesthesia of the low spinal cord and lumbar sympathectomy were all followed by an increase in the distensibility of the radial or the femoral artery, reflecting the stiffening effect neural influences exerted on the vessel wall. 4 Our hospital started a program of allotransplantation of the hand 2 years ago. This gave us a chance to determine what happens to arterial distensibility in transplanted organs and to make use of another human "model" on which to study the relationship between sympathetic tone and arterial distensibility, which could be measured at various times after the surgical intervention in the radial artery below the transplantation line, using the values obtained from the contralateral vessel as control. This article reports the results obtained in 2 patients. MethodsWe studied 2 men (patient 1, age 35 years; patient 2, age 31 years) who underwent allotransplantation of the right hand, which had been lost in a previous car accident. Both patients underwent a routine pretransplantation investigation and morphological and functional testing of the forearm stumps to ensure immunologic and mechanical donor-recipient compatibility. They were administered treatment with monoclonal antibodies anti-CD25 (Baxilimab, Simulect), FK506 (tacrolimus, Prograf), mycophenolate mofetil (Cell Cept), and prednisone immediately after surgery to prevent graft rejection. Maintenance therapy was unchanged throughout the study duration. The post -treatment program of rehabilitation (started as the swelling subsided...

Metabolic Syndrome and Vascular Alterations in Normotensive Subjects at Risk of Diabetes Mellitus

“…10 It is worth noting that MS has been demonstrated to further impair central arterial stiffness even in the presence of an established risk factor, such as essential hypertension, 32 leading to target organ damage, namely left ventricular hypertrophy. 5 Taken together, these considerations support the hypothesis that arterial stiffness might represent an important alteration contributing to the increased cardiovascular risk associated with the MS. 14,15 Possible mechanism explaining selective alteration on central aortic stiffness includes increased oxidative stress, 28 sympathetic nervous system activation, 33 and inflammation. 34 However, it has to be pointed out that an important cardiovascular risk factor, LDL cholesterol, which was higher in our patients with MS, was significantly associated with central arterial stiffness.…”

Increased Arterial Stiffness in Normoglycemic Normotensive Offspring of Type 2 Diabetic Parents

“…Second, because glucose values were normal and similar between the offspring of diabetic parents and control subjects, the arterial stiffening cannot be ascribed to any adverse effect of this substance on the functional characteristics of the vessel wall. 23,24 Third, although an increase in body weight and/or a state of insulin resistance reduce large artery distensibility (via a sympathetic activation [25][26][27][28][29][30] and possibly also via trophic influences that may alter the tissue composition of the vessel wall), it is also unlikely that these factors played a major role. This is because there was no relationship between BMI and carotid distensibility, which, in offspring of diabetic parents, was reduced also when BMI was normal.…”

Evidence for Pressure‐Independent Sympathetic Modulation of Central Pulse Wave Velocity

“…Similarly, arterial stiffening associated with healthy aging demonstrates similar relative increases in sympathetic outflow,15, 16 though parallel changes in blood pressure occur also 8, 9, 11. Sympathetic outflow to the vasculature is known to elicit vasoconstriction at resistance vessels17 and is shown to alter the local vascular properties of large and medium conduit arteries 18, 19, 20, 21. Importantly, the reductions in brachial artery distensibility with sympathetic activation occurred independent of changes in arterial pressure and diameter 22…”