High Skin Sympathetic Nerve Activity in Patients with Recurrent Syncope

Area of Science:

• Cardiology
• Autonomic Neuroscience
• Medical Diagnostics

Background:

• Autonomic dysfunction is implicated in vasovagal syncope (VVS).
• Head-up tilting test (HUT) is a standard diagnostic tool for VVS.
• The novel neuECG method simultaneously records skin electrical signals and electrocardiograms.

Purpose of the Study:

• To investigate the relationship between skin sympathetic nerve activity (SKNA) and HUT results.
• To determine if elevated SKNA predicts positive HUT outcomes.
• To evaluate the predictive value of a novel SKNA-SDNN index for syncope.

Main Methods:

• 41 subjects underwent HUT using the "Italian protocol" with neuECG monitoring.
• Analyzed average SKNA (aSKNA) and standard deviation of normal-to-normal intervals (SDNN) during HUT phases.
• Calculated the "SKNA-SDNN index" using resting aSKNA and SDNN ratios.

Main Results:

• 16 out of 41 subjects (39%) experienced syncope during HUT.
• Tilt-positive subjects exhibited significantly higher resting aSKNA (1.21 ± 0.27 µV) compared to tilt-negative subjects (1.02 ± 0.29 µV).
• Significant SKNA surges and withdrawals occurred 30 seconds before and after syncope events (p ≤ 0.006).
• The SKNA-SDNN index demonstrated strong predictive capability for syncope (p < 0.001).

Conclusions:

• Elevated resting SKNA is associated with positive HUT results, indicating a predisposition to VVS.
• The SKNA-SDNN index serves as a novel and effective marker for predicting syncope during HUT.
• This study highlights the utility of neuECG in assessing autonomic function related to VVS.