Abstract
Recurrent syncope — abrupt loss of consciousness — can have a serious impact on patients’ quality of life, comparable with chronic illnesses. Vasovagal syncope (VVS) is a specific reflex syncope, in which an inappropriate reaction of the autonomic nervous system (ANS) plays a key role in the pathophysiology. In syncope diagnosis, an ideal diagnostic method should positively identify vasovagal sensitive patients, without the need to perform a specialised head-up tilt table (HUTT) test. We apply a novel methodology of multistructure index (MI) statistics for seamlessly evaluating the size spectrum of the asymmetry properties of magnitudes of neural reflexes responsible for maintaining the homeostatic dynamics of autonomic control. Simultaneous evaluation using the MI of the effects on heart rate and blood pressure involved in achieving homeostasis of contrasting properties of the dynamics of slow and fast neural regulation reveals a clear distinction between vasovagal patients and healthy subjects, who are/are not susceptible to spontaneous fainting. Remarkably, a healthy cardiovascular response to the HUTT test is indeed evident prior to the test, making the MI a robust novel indicator, clearly distinguishing the cardiovascular autonomic regulation of healthy people from that of vasovagal patients without the need to perform an actual HUTT test.
Highlights
The physiological mechanisms responsible for heart rate accelerations and decelerations and for rises and falls in blood pressure are distinct[1]
While considerable research has been devoted to autonomic nervous system (ANS) dysfunction assessment by heart rate variability (HRV) and BPV analysis, less attention has been paid to revealing other mechanisms responsible for syncope by using heart rate and blood pressure variability investigations
The top lines refer to the significance of the difference with respect to the results obtained for the control group (CG) group
Summary
The physiological mechanisms responsible for heart rate accelerations and decelerations and for rises and falls in blood pressure are distinct[1]. A decrease in blood pressure is sensed by arterial baroreceptors, which first results in the decreased activation of the vagal branch of the ANS and in the subsequent rise of the heart rate within one or two following heartbeats. Spectral methods of heart rate and blood pressure variability analysis have been extensively used to describe cardiovascular rhythms and the role of the ANS activity during vasovagal syncope[8, 9]. While considerable research has been devoted to ANS dysfunction assessment by HRV and BPV analysis, less attention has been paid to revealing other mechanisms responsible for syncope by using heart rate and blood pressure variability investigations. This suggests that asymmetric time patterns characterize the underlying dynamics[10, 12], and might be used for better understanding of complex responses provoked by the HUTT
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