OBJECTIVES: @entity11924 ( @entity1112 ) is a clinical condition characterised by angina, positive exercise stress test and negative coronary angiography; it has often been attributed to sympathetic hyperactivity. Here we tested the hypothesis that a parasympathetic, rather than a sympathetic, dysfunction could be the cause of the autonomic imbalance observed in @entity1112 . METHODS: In 20 subjects with diagnosed @entity1112 and in 12 age-matched controls, we studied autonomic function by performing spectral analysis of RR interval and finger arterial pressure (SAP), in supine position and during head-up tilting. We also carried out a set of tests of parasympathetic function. RESULTS: The group of @entity1112 @entity1 did not differ significantly from control subjects in any of the variables tested. In a subgroup of 13 @entity1112 , however, tilting increased the low-frequency power of SAP, but did not induce the expected increase in low-frequency and decrease in high-frequency power of RR. These @entity1 , in supine position, had significantly lower sinus @entity943 and a higher ratio of low to high frequency of RR, in comparison with control subjects. We interpreted these differences as signs of reduced parasympathetic, but essentially normal sympathetic, activity. The parasympathetic tests confirmed @entity73 in the same @entity1112 subjects. On the other hand, all the tests indicated normal parasympathetic functions in the control subjects and in those @entity1112 @entity1 who displayed the expected spectral changes in tilting. CONCLUSIONS: In about two thirds of the @entity1 with @entity1112 , the pathophysiological mechanism causing the symptoms could be related to the reduced parasympathetic tone, rather than to an augmented sympathetic activity.

Evidence of @entity73 in some XXXX with @entity11924 .

@entity1 :: ('9606', 'Species') :: ['patients'] @entity73 :: ('MESH:D003072', 'Disease') :: ['vagal impairment'] @entity1112 :: ('MESH:D040181', 'Disease') :: ['SX'] @entity11924 :: ('MESH:D017566', 'Disease') :: ['Cardiac syndrome X'] @entity943 :: ('MESH:D001145', 'Disease') :: ['arrhythmia']
@entity1 :: (9606,Species) :: ['patients']
