Comparison of cardio-cerebral hemodynamics in non-prodromal and prodromal vasovagal syncope: a prospective...

Vasovagal syncope (VVS) without aura is characterised by a high fall risk and misdiagnosis rate. However, its hemodynamic characteristics remain unclear.

A total of 221 participants were prospectively and consecutively enrolled, including 34 patients with non-prodromal VVS, 118 patients with prodromal VVS, and 69 non-syncope controls. All participants completed the head-up tilt test (HUTT) combined with transcranial Doppler (TCD). Blood pressure, heart rate, and cerebral hemodynamic parameters were monitored dynamically during the test. Data were statistically analysed.

The non-prodromal VVS group consisted predominantly of males (70.59% vs. 37.29%), had a higher body mass index (median 24.14 vs. 21.26 kg/m²), and was older (median 47 vs. 37 years) (all p < 0.05). The baseline cerebral blood flow velocity (CBFV) in the non-prodromal VVS group was significantly lower than that in the prodromal VVS group (55 vs. 60 cm/s, p = 0.009), and the decrease of CBFV during the tilt test preceded the change of blood pressure. During the return to the supine position after HUTT, systolic blood pressure was significantly higher in the non-prodromal VVS group than in the prodromal VVS group (p = 0.019), and the heart rate increment was greater during the drug-induced phase.

Non-prodromal VVS, with its unique hemodynamic profile involving early cerebral hypoperfusion and impaired central compensatory mechanisms, represents a high-risk subtype associated with higher fall risk. The identified hemodynamic differences may serve as objective biomarkers for its diagnosis. This study highlights the need for tailored management strategies.