Cardiocerebral hemodynamic characteristics of vasovagal syncope associated with cerebral autoregulation impairment

It is generally believed that cerebral hypoperfusion in patients with vasovagal syncope (VVS) is secondary to hypotension; however, current evidence suggests that this is not always the case. Thus, this study aimed to analyze the hemodynamic characteristics of patients with VVS and dynamic cerebral autoregulation (CA) dysfunction (referred to as CA-impaired VVS) to improve the diagnosis and treatment of this VVS subtype.

This retrospective study included 143 patients with VVS who underwent the head-up tilt test (HUTT) using transcranial Doppler (TCD). Patients were divided into two groups based on pathogenesis: CA-impaired VVS and blood pressure drop-dominant VVS. Hemodynamic parameters, including systolic and diastolic blood pressure, heart rate, and cerebral blood flow velocity (CBFV), were compared between the two groups to further analyze the differences in cardiocerebral hemodynamic indices.

CA-impaired VVS accounted for 58% of the cases. During basic HUTT in the upright tilt position, the minimum systolic blood pressure (SBP), minimum diastolic blood pressure (DBP), and minimum mean arterial pressure (MAP) were significantly higher in the CA-impaired group than in the blood pressure drop-dominant group (p < 0.05). Similarly, during the sublingual nitroglycerin HUTT in the upright tilt position, the minimum SBP, DBP, and MAP were significantly higher in the CA-impaired group than in the blood pressure drop-dominant group (p < 0.05). After returning to the supine position, the mean SBP, DBP, and MAP remained significantly higher in the CA-impaired group than in the blood pressure drop-dominant group (p < 0.05). In addition, the positivity rates for orthostatic tachycardia in the CA-impaired and blood pressure drop-dominant VVS groups were 73.5 and 65.0%, respectively. The incidence of neurogenic orthostatic hypotension was 2.4% in the CA-impaired group, which was significantly lower than the 16.7% in the blood pressure drop-dominant group (p = 0.002).

This study reveals the characteristics and differences in cardiocerebral hemodynamics between CA-impaired and blood pressure drop-dominant subtypes of VVS, deepens the understanding of VVS pathogenesis, facilitates the accurate diagnosis of VVS, and enhances the ability to interpret its results.