Key result
Higher plasma epinephrine levels and a greater Epi/NE ratio at 2 minutes of head-up tilt were significantly correlated with a shorter time to syncope (R = -0.58, P=0.001 and R = -0.49, P=0.007).
Why the study?
Whether marked increases in plasma epinephrine levels and epinephrine/norepinephrine ratio contribute directly to vasovagal syncope susceptibility during head-up tilt remained uncertain.
Observational (n=33)
Effect estimate: R = -0.58
p-value: p=0.001
Greater early rises in epinephrine and the epinephrine/norepinephrine ratio during head-up tilt testing are associated with a shorter time to vasovagal syncope, suggesting a pathophysiological role for catecholamines in syncope susceptibility.
Early epinephrine surge may predict shorter tilt-induced syncope time; hypothesis-generating for catecholamine mechanisms but leaves open therapeutic implications.
BACKGROUND: Head-up tilt (HUT) is widely used for diagnostic evaluation of patients with suspected vasovagal syncope (VVS), but also offers an opportunity to study VVS pathophysiology. In this regard, it is known that plasma epinephrine (Epi) levels and Epi/norepinephrine (NE) ratio are markedly increased from baseline at the time of HUT-induced VVS. However, whether these changes contribute to VVS susceptibility remains uncertain. OBJECTIVE: We hypothesized that if catecholamines contributed to VVS directly, then a greater increase of plasma Epi and Epi/NE ratio early during HUT would be associated with shorter time to syncope. METHODS: The patient population comprised 33 individuals (14 men, 43 ± 2 years) with suspected VVS in whom 70° HUT reproduced symptoms. Arterial Epi and NE concentrations were collected at baseline (supine) and 2 minutes of HUT. Linear, exponential, and multiple regression were used to access the association between changing catecholamine levels and time to syncope. RESULTS: Mean ± SD time to positive HUT was 11 (7.6) minutes. Higher plasma Epi levels (pg/mL) both at baseline and at 2 minutes upright correlated with shorter time to syncope (baseline, R = -0.35, P = 0.048; and 2 minutes, R = -0.58, P = 0.001). Similarly, a greater Epi/NE ratio at 2 minutes head-up correlated with earlier time to syncope (R = -0.49, P = 0.007). These relationships remained significant after adjusting for age and sex (P = 0.006 and 0.02, respectively). CONCLUSION: Greater Epi levels and Epi/NE ratio early during HUT were associated with shorter time to VVS, suggesting a possible contribution to VVS susceptibility.
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Kohno et al. (2018) conducted an observational in Suspected vasovagal syncope (n=33). Plasma epinephrine levels and Epi/norepinephrine ratio was evaluated on Time to syncope (R = -0.58, p=0.001). Higher plasma epinephrine levels and a greater Epi/NE ratio at 2 minutes of head-up tilt were significantly correlated with a shorter time to syncope (R = -0.58, P=0.001 and R = -0.49, P=0.007).
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