TCD in Patent Foramen Ovale (PFO) Evaluation

Transcranial Doppler (TCD) ultrasound has undergone a remarkable transformation in its role within the diagnostic workflow for cryptogenic stroke. Once seen as a supplementary method, it is now recognized as a central diagnostic tool—particularly in the detection of right-to-left shunts (RLS) via bubble testing. This shift is reflected in recent updates from multiple international clinical guidelines, which consistently highlight TCD’s diagnostic performance.

What do the guidelines say?

Here is a detailed look at how the world’s leading societies position TCD in the diagnosis and management of PFO-related stroke:

European Stroke Organisation (ESO), 2024

The 2024 ESO guidelines assess the value of diagnostic modalities in patients aged 18–60 with embolic stroke of undetermined source and suspected PFO. TCD with microbubble contrast is described as having a pooled sensitivity of approximately 96% and is noted to be more sensitive than transthoracic echocardiogram (TTE). The guidelines discuss the use of TCD in settings where TTE or TOE (transoesophageal echocardiogram) are unavailable or inconclusive. The role of TCD is framed within a multi-modality diagnostic pathway.

Society for Cardiovascular Angiography and Interventions (SCAI), 2022

This clinical expert consensus statement emphasizes diagnostic accuracy in the detection of RLS. TCD is labeled as a “highly sensitive” modality capable of identifying the presence and quantifying the magnitude of a shunt. The publication also notes TCD’s role in evaluating residual shunting following PFO closure.

American Heart Association (AHA), 2024 Special Report

In this special report on diagnostic strategies, TCD is described as a reliable method for shunt detection. Robotic-assisted TCD (raTCD) is highlighted as an emerging approach that may improve standardization and reproducibility. The report discusses TCD in the context of broader efforts to streamline diagnostic algorithms using noninvasive techniques.

American Heart Association / American Stroke Association (AHA/ASA), 2021

The 2021 update presents a tiered diagnostic strategy for evaluating PFO in cryptogenic stroke. TCD is positioned as a follow-up diagnostic tool when TTE is negative or inconclusive. If TCD shows evidence of shunting, transesophageal echocardiography (TEE) is then used to visualize the atrial septum and rule out other cardiac sources.

American College of Cardiology (ACC), 2021

This expert consensus pathway identifies TCD as a cost-effective and sensitive method in the initial evaluation of patients with embolic stroke of undetermined source. The publication discusses TCD’s place in the diagnostic process, especially in healthcare settings where TOE access is limited or sedation is contraindicated.

European Society of Cardiology (ESC), 2018

The ESC guidelines mention TCD as one of three noninvasive diagnostic options (along with TTE and TEE) for identifying PFO in patients with cryptogenic stroke. The publication emphasizes a multimodal diagnostic approach, with TCD considered a useful component for detecting RLS during contrast studies.

American Academy of Neurology (AAN), 2023 (Reaffirmed)

This practice advisory focuses on PFO evaluation in the context of embolic stroke. TCD is mentioned as a noninvasive tool suitable for detecting RLS via contrast-enhanced studies, especially when other methods are not definitive. The advisory also addresses uncertainties around PFO causality and highlights TCD’s role in selected younger patients.

American Society of Neuroimaging (ASN) / SCAI Consensus, 2022

In a joint consensus paper on neuroimaging for PFO evaluation, TCD is referred to as particularly useful for detecting RLS. The agreement between TCD and angiography is noted to be “good to excellent,” and TCD is described as having diagnostic performance comparable to or better than TTE in many cases.

Conclusion

The growing inclusion of Transcranial Doppler in clinical guidelines reflects its evolving role in the diagnostic evaluation of PFO-related stroke. Across neurological, cardiovascular, and stroke societies, TCD is consistently recognized for its high sensitivity, noninvasive nature, and utility in detecting right-to-left shunts. Its integration into multimodal diagnostic strategies highlights the importance of accurate, reproducible, and accessible imaging in modern stroke workups.