Utility of transcranial color flow imaging for detecting high risk morphology of patent foramen ovale in patients with cerebral infarction

Background Micro-bubble test by using transcranial color flow imaging (TCCFI) is important as a screening evaluation for diagnosis of paradoxical cerebral embolism which requires the proof of right to left shunt at atrial septum. In addition, high risk features of patent foramen ovale (PFO) that may allow thrombus to easily pass through the PFO itself were previously reported. However, little is known about the association between the degrees on micro-bubble test by TCCFI and the features of high risk PFO. Purpose Our aim is to clarify the relationship between the degree of micro-bubble test in TCCFI and the morphology of PFO from transesophageal echocardiography (TEE). Methods Seventy-seven patients in whom cardiogenic embolism was strongly suspected by neurologists in Showa University from April to December in 2019 were retrospectively studied. 55 patients underwent both TCCFI and TEE with sufficient Valsalva stress. TCCFI grade of micro-bubble test was classified into 3 groups (A: none, B: small, and C: massive), in which signified “none” is no sign of micro-embolic signals (MES) within 30 seconds, “small” is 1 or more MES, and “massive” is so much MES look like a curtain (Figure). Evaluated high risk characteristics of PFO for cerebral embolism as previously reported were as follows; (1) tunnel height, (2) tunnel length, (3) total excursion distance into right and left atrium, (4) existence of Eustachian valve or Chiari network, (6) angle of PFO from inferior vena cava (7) large shunt (20 or more micro-bubbles). Results Of all TCCFI-positive patients (n=32; Group B=19, Group C=13) with cerebral embolism, PFOs were detected in 23 patients in TEE. Therefore, the sensitivity and specificity of TCCFI to PFO were 87% and 63% (AUC=0.75, p<0.001, respectively). Interestingly, all 13 patients (Group C) had manifest PFOs. Moreover, group C include 2 patients with platypnea orthodeoxia syndrome in which hypoxia in the sitting position becomes apparent. Among PFO-positive patients, tunnel height, length, total excursion distance into right and left atrium, and large shunt in TEE were significantly larger in Group C than Group B (p<0.05). Conclusions Micro-bubble test by using TCCFI may have screening advantages in predicting paradoxical cerebral embolism, high-risk morphology of PFO, and platypnea orthodeoxia syndrome. Figure 1 Funding Acknowledgement Type of funding source: None