Transcranial Doppler as a Primary Screening Tool for Detecting Right‐to‐Left Shunt in Cryptogenic Stroke Patients?

BACKGROUND: Cryptogenic stroke (CS), a subtype of ischemic stroke with undetermined etiology, accounts for approximately 25% of the cases. Patent foramen ovale (PFO) is an important potential cause of CS via paradoxical embolism. While transesophageal echocardiography (TEE) is the current gold standard for PFO detection, transcranial Doppler (TCD) ultrasound offers a noninvasive alternative with potential advantages in sensitivity for right-to-left shunt (RLS) detection. This study's main goal is to evaluate the diagnostic performance of TCD compared to TEE for PFO detection in CS patients. METHODS: We prospectively enrolled 110 patients aged 18-65 years with confirmed CS from 2020 to 2024. All underwent TCD screening for RLS using a standardized protocol. Subsequently, they were categorized based on a simplified version of the Spencer Logarithmic Scale, followed by confirmatory TEE. Clinical characteristics, imaging findings, TCD results, and indications for PFO closure were analyzed. RESULTS: The mean age of the cohort was 45 years, with 58.2% being males. TEE identified PFO in 44.5% (49/110) of subjects. TCD accurately detected RLS in 42 of the 49 PFO cases (85.7%) confirmed by TEE. For PFO detection, TCD demonstrated a sensitivity of 85.4%, specificity of 88.5%, PPV of 85.4%, and Youden's index of 0.73. Notably, of the seven PFO cases missed by TCD, none received percutaneous closure based on clinical criteria. CONCLUSIONS: TCD exhibited high diagnostic accuracy for detecting high-risk PFO in patients with CS when compared to the gold-standard TEE. As a noninvasive modality, TCD may serve as an effective screening tool to identify CS patients who could potentially benefit from confirmatory TEE and subsequent PFO closure intervention. The findings support the use of TCD as a screening tool to triage CS patients for confirmatory TEE and potential PFO closure.