Key result
Tilt-induced syncope is linked to a ~17% lower LF/HF ratio of systolic blood pressure variability.
Why the study?
Autonomic changes play an essential role in the genesis of neurally mediated syncope, but differences in beat-to-beat heart rate and systolic blood pressure variability during tilt testing between patients with and without syncope are not well characterized.
Do spectral indices of beat-to-beat SBPV and HRV differ during head-up tilt test in patients with and without neurally mediated syncope?
Case-Control (n=46)
No
Do spectral indices of beat-to-beat SBPV and HRV differ during head-up tilt test in patients with and without neurally mediated syncope?
Absolute Event Rate: 4.84% vs 5.8%
p-value: p=<0.001
Patients with neurally mediated syncope exhibit abnormal autonomic function at rest and an exaggerated sympathetic response followed by withdrawal during tilt testing.
Hypothesis-generating for SBPV indices in neurally mediated syncope; requires prospective validation before clinical adoption.
Introduction: Autonomic changes play an essential role in the genesis of neurally mediated syncope (NMS). The aim of this study was to compare the changes of the autonomic nervous system (ANS) by measuring spectral indices of beat-to-beat systolic blood pressure and heart rate variability (SBPV and HRV) in ranges of low frequency (LF), high frequency (HF), and the LF/HF ratio during head-up tilt test (HUTT) in patients with and without a syncope response. Methods: In this case-control study of 46 patients with a suspected history of unexplained syncope, data were recorded separately during the typical three phases of HUTT. Patients who developed syncope were designated as the case group and the rest as the control group. Results: Thirty one patients experienced syncope during HUTT. Resting HRV and SBPV indices were significantly lower in cases than controls. After tilting in the syncope group, both HF and LF powers of SBPV showed a significant and gradual decrease. LF/HF in HRV increased in both groups similarly during the test but in SBPV, mainly driven by oscilations in its LF power, it increased significantly more during the first two phases of the test in syncope patients only to paradoxically decrease during active tilt (P< 0.001). Conclusion: Our findings show an abnormal autonomic function in patients with syncope, both at rest and tilting. Fluctuations of spectral indices of beat-to-beat SBPV, a potential noval index of pure sympathetic activity, show an exaggerated response during tilt and its withdrawal before syncope.
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Akbarzadeh et al. (2022) conducted a case-control in Neurally mediated syncope (n=46). Syncope response during head-up tilt test vs. No syncope response was evaluated on LF/HF ratio of systolic blood pressure variability during active tilt (p=<0.001). Patients who developed syncope during a head-up tilt test exhibited a paradoxical decrease in the low-frequency to high-frequency ratio of systolic blood pressure variability during active tilt compared to controls (P<0.001).
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