Arterial baroreflex function in older adults with neurocardiogenic syncope

Area of Science:

• Cardiovascular Physiology
• Geriatric Medicine
• Autonomic Nervous System Function

Background:

• Neurocardiogenic syncope, previously known as vasovagal syncope, is a common cause of falls in older adults.
• The underlying mechanisms contributing to syncope in this demographic remain incompletely understood.
• Orthostatic stress is frequently implicated in the precipitation of syncopal events.

Purpose of the Study:

• To investigate differences in baseline arterial baroreflex function between older adults with and without a neurocardiovascular response to orthostatic stress.
• To elucidate the role of baroreflex sensitivity in the pathophysiology of neurocardiogenic syncope in the elderly.

Main Methods:

• 42 older adults were categorized into two groups: those exhibiting a neurocardiovascular response to head-up tilt (TT+ group) and those who did not (TT- group).
• Neurocardiovascular response was defined by presyncopal symptoms and a significant drop in blood pressure during a 70-degree head-up tilt test post-nitroglycerin administration.
• Arterial baroreflex sensitivity (BRS) was assessed at baseline using the spontaneous baroreflex method, analyzing beat-to-beat fluctuations in blood pressure and heart rate.

Main Results:

• The TT+ group showed significantly higher baseline arterial baroreflex sensitivity, specifically in response to decreases in blood pressure (BRSdown), compared to the TT- group (11.2 vs. 7.3 ms/mm Hg, P=0.011).
• During the tilt test, the TT+ group experienced a more pronounced reduction in overall arterial baroreflex sensitivity than the TT- group (-6.8 vs. -3.2 ms/mm Hg, P=0.012).
• A negative correlation was observed between baseline BRSdown and the duration of the tilt test in the TT+ group (r=-0.329, P=0.041).

Conclusions:

• Older adults who experience neurocardiogenic syncope possess an exaggerated arterial baroreflex sensitivity at rest.
• This heightened baroreflex sensitivity may represent a predisposing factor for neurocardiogenic syncope and subsequent falls in the elderly population.