Abstract WP110: Predictors Of False Positive Shunt Detected By Transcranial Doppler: When Is Intracardiac Echocardiogram Beneficial?

Background and Objective: Right to left shunts (RLS) found with patent foramen ovale (PFO) are implicated in the pathogenesis of cryptogenic stroke and a risk factor for neurological event. The capability and sensitivity of Transcranial Doppler ultrasound (TCD) to detect a PFO has been established. However, predictors of false positive shunts detected by TCD and benefit of intracardiac echocardiogram (ICE) when studies show conflicting results have not been determined. Methods: In this retrospective study, patients who underwent shunt testing with ICE ± endovascular atrial septal defect closure from 2018 till 2022 were included. We abstracted data regarding the type of study used for shunt detection such as transthoracic echocardiogram (TTE), transesophageal echocardiogram (TEE), ICE and TCD. PFO size and characteristics were evaluated. International consensus criteria were used for TCD PFO detection. Results: A total of 184 patients underwent ICE testing, of which 169 (93.4%) had prior TTE, 116 (63%) TEE, and 48 (25%) prior TCD. Among 48 patients with TCD, 24 had negative TTE and 4 had negative TEE. Mean (SD) age was 51.1(14.4). 110(59.8%) were female. Among all patient with ICE 169 (91.8%) had PFO. PFOs were detected in 38 out of 48 (79.1%) patients who had been assessed with both ICE and TCD, whereas 6 patients (12/5%) were found to have a RLS on TCD but no PFO on ICE, p<0.01. Comparing ICE and TCD grading scores for shunt detected, 45.2% had higher grade by TCD compared to ICE, p= 0.17. Among the six false positive cases on TCD, four of them had shower of microembolization and 2 of them had 0-10 HITS microemboli detection. Conclusion: Transcranial Doppler ultrasound detection of right to left shunt remains highly sensitive and a non-invasive tool. Considering ICE as gold standard, TCD is associated with false positive shunt detection. Further studies are warranted to assess the shunt characteristics on TCD that are associated with higher predictive value for identifying PFO.