Increased Sympathetic Nerve Activity Correlates With Neurovascular Compression at the Rostral Ventrolateral Medulla (original) (raw)
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Neurovascular compression: sympathetic activity in severe arterial hypertension
Physiological research / Academia Scientiarum Bohemoslovaca, 2009
Compression of the rostral ventrolateral medulla oblongata (RVLM) by an abnormally located artery is regarded as one possible cause of arterial hypertension. There exists a limited set of data suggesting that increased sympathetic activity in patients with RVLM compression may lead to arterial hypertension. Accordingly, we decided to assess the sympathetic activity in patients with severe arterial hypertension and to investigate any correlation with the presence of RVLM compression. Sixty-four patients with severe arterial hypertension were enrolled in our study. Sympathetic activity was evaluated using 24-hour urinary norepinephrine as measured by high-pressure liquid chromatography with electrochemical detection. The presence of RVLM compression was assessed with magnetic resonance imaging. Neurovascular compression of the RVLM was identified in 40 patients, 27 of whom presented left-sided compression. Twenty-four hour urinary norepinephrine averaged 263.6+/-135.9 nmol in patients...
Journal of the American College of Cardiology, 2004
We planned to examine the relationship between neurovascular compression (NVC) of the rostral ventrolateral medulla (RVLM) and the magnitude of central sympathetic hyperactivity in normal subjects and in patients with untreated and uncomplicated essential hypertension (EHT). BACKGROUND Previously it has not been possible to establish a definitive relationship between EHT and NVC of the RVLM, a location containing efferent sympathetic vasoconstrictor neurons. Furthermore, the relationship between NVC and magnitude of sympathetic nerve hyperactivity has not been adequately examined, despite the knowledge that hyperactivity varies according to EHT severity.
elationship of Neurovascular ompression to Central Sympathetic ischarge and Essential Hypertension
2016
OBJECTIVES We planned to examine the relationship between neurovascular compression (NVC) of the rostral ventrolateral medulla (RVLM) and the magnitude of central sympathetic hyperactivity in normal subjects and in patients with untreated and uncomplicated essential hypertension (EHT). BACKGROUND Previously it has not been possible to establish a definitive relationship between EHT and NVC of the RVLM, a location containing efferent sympathetic vasoconstrictor neurons. Furthermore, the relationship between NVC and magnitude of sympathetic nerve hyperactivity has not been adequately examined, despite the knowledge that hyperactivity varies according to EHT severity. METHODS In 83 subjects, we used magnetic resonance imaging to detect NVC and, independently, peroneal microneurography to quantify muscle sympathetic nerve activity (MSNA), expressed as the mean frequency of multi-unit discharge (m-MSNA) and of single units (s-MSNA). Subjects were classified according to arterial pressure...
Hypertension, 2000
The pathophysiological factors of neurogenic or sympathetically mediated essential hypertension are unknown. Neurons close to the surface of the ventrolateral medulla (specifically, in the retro-olivary sulcus [ROS]) are integrally involved in the control of blood pressure by means of efferent connections to presympathetic neurons in the spinal cord. It is hypothesized that vascular contact with the ROS is pathogenically involved in neurogenically mediated hypertension. We evaluated that theory in 20 subjects with uncomplicated stage 1 to stage 2 essential hypertension (EHTN) (18 of whom completed the study). The baseline supine plasma norepinephrine level served as an index of central sympathetic outflow. The response of blood pressure to clonidine was used as a surrogate marker for neurogenically mediated hypertension. We also examined the relationship between those markers and evidence of anatomic abnormalities in the area of the ROS that was provided by magnetic resonance imaging. A vessel contacted the left ROS in 5 of the 18 subjects. Those 5 subjects had higher plasma norepinephrine concentrations than did the 13 subjects without this vascular contact (358Ϯ46 versus 76Ϯ43 pg/mL, PϽ0.001). These 5 subjects also exhibited a significant depressor response to clonidine that tended to be greater than that seen in the 13 subjects without vascular contact (Ϫ20.6Ϯ3.2 versus Ϫ13.6Ϯ9 mm Hg). Both race and baseline mean blood pressure had only an independent effect on the depressor response to clonidine. The findings are consistent with the theory that vascular contact with the left ROS may contribute to neurogenically mediated "essential" hypertension in some patients.
Circulation, 2005
Background— Despite the accumulated knowledge of human muscle sympathetic nerve activity (SNA) as measured by microneurography, whether muscle SNA parallels renal and cardiac SNAs remains unknown. Method and Results— In experiment 1, muscle (microneurography, tibial nerve), renal, and cardiac SNAs were recorded in anesthetized rabbits (n=6) while arterial pressure was changed by intravenous bolus injections of nitroprusside (3 μg/kg) followed by phenylephrine (3 μg/kg). In experiment 2, the carotid sinus region was vascularly isolated in anesthetized, vagotomized, and aorta-denervated rabbits (n=10). The 3 SNAs were recorded while intracarotid sinus pressure was increased stepwise from 40 to 160 mm Hg in 20-mm Hg increments maintained for 60 seconds each. Muscle SNA averaged over 1 minute was well correlated with renal ( r =0.96±0.01, mean±SE) and cardiac ( r =0.96±0.01) SNAs in experiment 1 (baroreflex closed-loop condition) and also with renal ( r =0.97±0.01) and cardiac ( r =0.97...
Sympathetic neural control of cardiovascular function is essential for normal regulation of blood pressure and tissue perfusion. In the present review we discuss sympathetic neural mechanisms in human cardiovascular physiology and pathophysiology, with a focus on evidence from direct recordings of sympathetic nerve activity using microneurography. Measurements of sympathetic nerve activity to skeletal muscle have provided extensive information regarding reflex control of blood pressure and blood flow in conditions ranging from rest to postural changes, exercise, and mental stress in populations ranging from healthy controls to patients with hypertension and heart failure. Measurements of skin sympathetic nerve activity have also provided important insights into neural control, but are often more difficult to interpret since the activity contains several types of nerve impulses with different functions. Although most studies have focused on group mean differences, we provide evidence that individual variability in sympathetic nerve activity is important to the ultimate understanding of these integrated physiological mechanisms.
Hypertension (Dallas, Tex. : 1979), 2018
Muscle sympathetic nerve activity (MSNA) has shown that sympathetic activation may occur in essential hypertension (EHT). However, the small sample size of the studies, the heterogeneity of the patients examined, and the presence of confounders represented major weaknesses not allowing to draw definite conclusions. Among the 432 studies identified providing information in EHT on MSNA, 63 were eligible (1216 patients) and meta-analyzed grouping them on the basis of clinically relevant questions: (1) Is MSNA increased in hypertension of mild/moderate-to-severe degree? (2) Does sympathetic activation occur in borderline, white-coat, and masked EHT? (3) Is MSNA related to clinic and ambulatory blood pressure and target organ damage? (4) Are heart rate and venous plasma norepinephrine valuable surrogate markers of MSNA in clinical practice? The results show that MSNA was significantly greater (1.5×; <0.001) in mild-to-moderate and severe EHT as compared with normotensive controls and ...