Clinical Significance of High Intensity Transient Signal Detected by TCD.

High intensity transient signals (HITS) were detected in patients with a high risk of stroke. The signals were detected in the middle cerebral artery for 15-30 min by a TC2020 or Multi-Dop DX4. HITS were never detected in young healthy volunteers (n=20) . The HITS count in patients with cerebral infarction (16-20/30 min, n-42) was significantly higher than that in patients without cerebrovascular disease (0.5±0.7/30 min, n17) (p<0.01) . In the cerebral infarction group, the HITS count in patients without antiplatelet (20±29/30 min, n=20) was significantly higher than that in patients with antiplatelet (9±6/30 min, n=22) (p<0.01) . HITS were frequently detected in patients fitted with mechanical valves (St. Jude Medical valve) (14.3±34.5/15 min, n=51), and the count was significantly higher than that in open heart surgery patients without mechanical valves (0.05+0.08/15 min, n=11) (p<0.01) . In the mechanical valve replacement group, the HITS count in patients with cerebral infarction after surgery (88±66/30 min, n=43) was significantly higher than that in patients without a historyof stroke (7±7, n-8) (p<0.01) . The HITS intensity in the mechanical valve replacement group (15.1+4.3 dB, n=31) was significantly greater than that in the cerebral infarction group (10.8+1.1dB, n-32) (p<0.05) . In the mechanical valve replacement group, the HITS intensity in patients with post-surgical cerebral infarction (18±3.5 dB, n8) was significantly greater than that in patients without a history of stroke (14.5±5.6 dB, n=23) (p<0.0001) . During veno-arterial extracorporeal membrane oxygenation (V-A ECMO), HITS were frequently detected (124±60/15 min, n=6), and the HITS count was negatively correlated with activated coagulation time (ACT) . HITS may therefore reflect the presence of microemboli and indicate the risk of stroke or the state of blood coagulation.