Transcranial Doppler signals during cerebral angiography and cardiac catheterization

Cerebral angiography is associated with a 0.45-4% risk of neurological complications and a less than 1% risk of permanent neurological deficit. Recently, air embolism has been implicated as a major cause of these complications. Cardiac catheterization is associated with a neurological complication rate of less than 1%; the predominant mechanism appears to be embolic. We used transcranial Doppler ultrasonography to detect high-intensity signals suspected to be related to air emboli, a potential cause of neurological complications in patients undergoing coronary and carotid angiography. We prospectively examined a total of 42 consecutive patients with transcranial Doppler ultrasound. Twenty-one patients underwent cerebral angiography, and 21 patients underwent cardiac catheterization. In both groups of patients, high-intensity bidirectional Doppler signals were recorded during different phases of angiography. High-intensity, longduration Doppler signals completely masking the background cardiac cycle signals were observed during machine-powered rapid injection of contrast medium with good correlation between the duration of Doppler signals and the duration of automated injection. In addition, high-intensity signals of much shorter duration were also observed during manual injection of saline or contrast medium and during catheter manipulation. In our study, the high-intensity Doppler signals recorded were identical in all patients who underwent cerebral and coronary angiography. No spontaneous emboli were seen. None of our 42 patients developed any type of neurological symptoms during or after the procedure. These high-intensity signatures do not represent air embolism exclusively; rather, they are likely a combination of turbulence in the bloodstream created during rapid injection, air emboli, and, perhaps, echogenicity of the contrast medium.