Introduction: While the examination for the evaluation of right-to-left shunt (RLS) using contrast transcranial Doppler (TCD) is useful, insufficient temporal bone window interrupts the adequate TCD examination for precise diagnosis of RLS. Thus, we developed a novel probe (paste-able soft ultrasound probe; PSUP) attached to the cervix for RLS diagnosis.
Hypothesis: Monitoring at carotid artery using PSUP can detect greater number of contrast microembolic signals (cMES) than that of TCD.
Methods: Subjects were patients with ischemic stroke or transient ischemic attack who had one and more cMES in middle cerebral artery detected by screening test of TCD on admission. PSUP was a 2.0-MHz center frequency and had an equal property with TCD transducer. The shape was thin, soft, and square modified for adequate attachment to the neck. We monitored blood flow of unilateral middle cerebral artery by TCD and ipsilateral common carotid artery by PSUP simultaneously. After injection of saline agitated with air in the right antecubital vein, we performed single test without Valsalva maneuver (VM) and triple tests with VM. And then, we compared the number of cMES between PSUP and TCD among each patient.
Results: We performed 48 simultaneous PSUP and TCD examination (12 studies without VM, and 36 studies with VM) on 12 patients (11 male, median age of 49 years) without any complication. The number of cMES on PSUP was significantly larger than that of TCD in all of 48 examination (345 vs. 206, p<0.001), in 12 studies without VM (72 vs. 37, p=0.017), and in 36 studies with VM (273 vs. 169, p<0.001).
Conclusions: In order to evaluate the RLS, PSUP examination at common carotid artery is a powerful approach in comparison with TCD. For patients without sufficient temporal bone window, PSUP should play an important role of RLS diagnosis.