Role of the Transcranial Doppler Bubble Test in the Diagnostic Pathway of a Patent Foramen Ovale in Embolic Stroke of Undetermined Source

Background: A patent foramen ovale (PFO) is frequently found in embolic stroke of undetermined source (ESUS). The transcranial Doppler (TCD) bubble test allows for the sensitive detection of right-to-left shunt but is still underused in standard diagnostic procedures. Objective: This study aimed to evaluate the clinical impact of the TCD bubble test on diagnostic reclassification and secondary prevention strategies in patients with ESUS. Methods: We conducted a retrospective observational study including ESUS patients admitted to the Department of Neurology, Ibn Rochd University Hospital, a tertiary care neurology center in Casablanca, Morocco, between January 2023 and July 2025. All patients underwent the TCD bubble test. Transesophageal echocardiography (TEE) was performed when clinically indicated. Right-to-left shunt severity was graded according to international consensus criteria. PFO was considered confirmed only when functional evidence on TCD and anatomical confirmation on TEE were concordant. Clinical, imaging, and therapeutic data were analyzed descriptively. Results: A total of 117 patients met the inclusion criteria (mean age 45.5 ± 12.4 years; 73/117 (62.0%) female). TCD detected a right-to-left shunt in 48/117 patients (41.0%), with a severe shunt or curtain effect observed in 23/117 patients (19.7%). An adequate Valsalva maneuver was achieved in 109/117 examinations (93.2%). TEE was performed in 59/117 patients (50.4%). Initial discordance between TCD and TEE was observed in 13/59 patients (22.0%). Repeat TEE, performed in selected discordant cases, led to diagnostic correction in all re-evaluated patients, increasing final concordance to 54/59 (91.5%). Overall, PFO was confirmed in 39/117 patients (33.3%). In one patient with a severe shunt on TCD and a negative TEE, further evaluation revealed a pulmonary arteriovenous malformation. TCD findings directly influenced clinical management, including antithrombotic strategy selection and referral for percutaneous PFO closure. Percutaneous closure was performed in 22/117 patients (18.8%), including selected individuals aged ≥60 years with high-risk functional and anatomical features. Conclusions: In patients with ESUS, the TCD bubble test provides valuable clinical information that corrects diagnostic errors and directly influences secondary prevention strategies. By guiding the use and interpretation of TEE and supporting personalized treatment decisions, TCD acts as an effective first-line screening and gatekeeper tool in ESUS diagnostic pathways.