ArticleClinical autonomic research : official journal of the Clinical Autonomic Research Society2025
Progressive baroreflex dysfunction and hypotension preceding VVS: a vicious cycle?
Article in Clinical autonomic research : official journal of the Clinical Autonomic Research Society, 2025. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Cited by 1 paper.
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Who cites it
1 citing paper in PubMed.
- Defying gravity: Breath, beat and brain.Experimental physiology · 2025Article
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3 authors.
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Abstract
purposeWe aimed to clarify the mechanism for presyncope, defined as the gradual onset of hypotension, starting some minutes before vasovagal syncope. Although there is a fall in cardiac output and usually vasodilatation, the control of sympathetic activity during presyncope is uncertain.
methodsWe retrospectively compared haemodynamics and muscle sympathetic nerve activity levels from positive tilt tests (without provocation) in patients with known vasovagal syncope (age 41 ± 3 years, 13 female, n = 27) to controls (age 39 ± 3 years, 8 female, n = 13). We used sequence methods to measure vascular sympathetic and cardiovagal baroreflex gain at baseline (lying supine) during tilt, presyncope and recovery.
resultsPatients were tilted for 18.1 ± 1 min, and mean arterial pressure fell to 62 ± 3 mmHg before tilt-back. At baseline and early tilt, all haemodynamic variables were similar to controls, however sympathetic baroreflex gain was increased: -2.7 ± 0.2 bursts/100 beats/mmHg versus -2.0 ± 0.3 (p = 0.03). Cardiovagal baroreflex gain was increased at baseline 11.8 ± 0.6 ms/mmHg versus 9.3 ± 0.8 (p = 0.02). During early presyncope (from 8 to 4 min before tilt-back), sympathetic baroreflex gain fell to -2.4 bursts/100 b/mmHg and thereafter to -0.5 ± 0.3 (p = 0.01) during late presyncope, before losing correlation with mean arterial pressure. In some patients, the regression coefficient reversed before correlation was lost (n = 8) but this did not result in lower levels of nerve activity. At tilt-back, nerve activity fell below baseline levels in at least 63% of patients.
conclusionPresyncope appeared to be initiated by a fall in sympathetic baroreflex gain despite increased levels at baseline and early tilt.
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