Right-to-left shunt is associated with reduced cerebral vascular reactivity in migraine patients with aura.

OBJECTIVE: To investigate whether right-to-left shunt (RLS) associated with patent foramen ovale (PFO) is associated with altered cerebrovascular reactivity (CVR) in migraine patients with aura. METHODS: This cross-sectional observational study enrolled migraine patients with aura who attended the outpatient clinic of Anhui No. 2 Provincial People's Hospital between December 2022 and September 2025. All patients underwent contrast-enhanced transcranial Doppler (c-TCD) examination, confirmed by contrast transthoracic echocardiography (c-TTE), to detect RLS and determine PFO status. PFO-negative patients served as the internal control group. RLS was graded (0-3) based on the number of microembolic signals (MES), and patients were further classified as having either latent RLS (microbubbles appearing only after Valsalva maneuver) or persistent RLS (microbubbles appearing at rest). Cerebrovascular reactivity was indirectly assessed by measuring the breath-holding index (BHI) via transcranial Doppler. BHI differences were compared between PFO-positive (+) and PFO-negative (-) groups, between latent and persistent PFO groups, and across different RLS grade groups. RESULTS: Compared with the PFO (-) group, the PFO (+) group exhibited significantly reduced BHI values in the bilateral middle cerebral arteries (MCAs) and bilateral posterior cerebral arteries (PCAs; all P < 0.05). The reduction in BHI became more pronounced with increasing RLS severity grade, showing a significant monotonic trend (Spearman's ρ ranging from -0.401 to -0.466, all P < 0.001). Furthermore, migraine patients with aura who had persistent PFO demonstrated a greater decrease in BHI than those with latent PFO compared with the PFO (-) group (P < 0.05). CONCLUSION: RLS associated with PFO is associated with reduced CVR in migraine patients with aura, with more pronounced reductions in cases of large shunts and persistent shunt types.