Abstract TP007: Beyond Echocardiography: How Transcranial Doppler Transforms Right-to-Left Shunt Detection and Stroke Management

Background: Although growing evidence shows that transthoracic echocardiography (TTE) has limited sensitivity for detecting right-to-left shunt (RLS) in patients with ischemic stroke, most comprehensive stroke centers in the United States continue to use TTE as the initial screening test. We evaluated the impact of transitioning to transcranial Doppler (TCD) as the primary screening tool for RLS in patients presenting with acute ischemic stroke of unknown etiology. Methods: In this single-center cohort study at Hennepin County Medical Center (Minneapolis), consecutive patients with acute ischemic stroke of unknown etiology over a 6-month period underwent both TTE with bubble study and TCD with bubble study. We compared RLS detection rates, documented the location of high-intensity transient signals (HITS) on TCD, and recorded downstream management changes. Detection frequency was calculated for each modality, and the relative likelihood of RLS detection with TCD versus TTE was estimated using paired analysis. Results: Thirty-one patients were included (mean age 52 years, 39% female). The odds of RLS detection were nearly three times higher with TCD compared to TTE (odds ratio = 2.93, 95% CI = 1.16–7.40). TCD was positive while TTE was negative in 45% of patients; among these, 35.7% had a moderate to large degree of shunting. No patient was positive on TTE and negative on TCD. HITS were most often detected in the bilateral middle cerebral arteries. In 22% of cases, RLS detection by TCD led to changes in management, including deep vein thrombosis screening, referral for patent foramen ovale closure evaluation, and adjustment of antithrombotic therapy. Conclusion: Transitioning from TTE to TCD as the initial screening method for RLS substantially increased detection rates, identified shunts missed by TTE, and influenced patient management. These findings support the adoption of TCD with bubble study as a first-line diagnostic approach for RLS detection in comprehensive stroke centers.