Introduction: We developed a novel probe (paste-able soft ultrasound probe; PSUP) attached to the cervix for detection of right-to-left shunt (RLS), because insufficient temporal bone window interrupts the precise examination for diagnosis of RLS.
Hypothesis: We assessed the hypothesis that diagnostic ability of PSUP for RLS detection is equal to those of transesophageal echocardiography (TEE).
Methods: Subjects were patients with ischemic stroke and transient ischemic attack who underwent TEE. PSUP was a 2.0-MHz center frequency, which had an equal property with TCD, and the shape was thin, soft, and square modified for attachment to the neck. At first, we performed TEE with the echoscope at the level of the fossa ovalis after injection of saline agitated with air in the right antecubital vein. The procedure was performed with and without Valsalva maneuver. Visualization of microembolic signals (MES) induced contrast agent within the right atrium and crossing the interatrial septum was considered as positive patent foramen ovale (PFO). We divided PFO into two groups according to number of MES, such as small PFO (1-29 of MES) and large PFO (≥30 of MES). Then, monitoring using PSUP was performed at unilateral common carotid artery (CCA) using similar preparation and procedure to TEE. RLS by PSUP diagnosed when we found 1and more MES in CCA. We compared detectable rate by size of PFO between TEE and PSUP, and calculated accuracy of PSUP against TEE.
Results: From May 2014 to July 2015, 62 patients (46 male, mean age of 61 years) were included in this study. We diagnosed 26 of 62 patients (42%) as PFO by TEE, whereas PSUP detected in 17 of them (27%). As a reference of TEE findings, diagnostic ability of PSUP was 58% of sensitivity, 94% of specificity, and 79% of accuracy. In TEE examination, large PFO was 11 patients and small was 15 patients. PSUP could evaluate large PFO (9 of 11 patients) more accurately than small one (6 of 15, 82% vs. 40%, p=0.05).
Conclusion: PSUP should have a considerable accuracy of large PFO diagnosis. For patients with insufficient temporal bone window, PSUP may play an important role of detecting large PFO.