Contrast transcranial Doppler ultrasound in the detection of right-to-leftshunts - Comparison of different procedures and different contrast agents

Background and Purpose-Cardiac right-to-left shunts can be identified by tr ansesophageal echocardiography (TEE) and by transcranial Doppler ultrasound (TCD) with the use of different contrast agents and different provocation procedures. Currently, data on an appropriate time window for the appearanc e of contrast bubbles in the TCD recording after the injection of the contr ast medium and the comparison of different provocation maneuvers to increas e right-to-left shunting are insufficient. Methods-Forty-six patients were investigated by both TEE and bilateral TCD of the middle cerebral artery. The following protocol with 6 injection mode s was applied in a randomized way: (1) injection of 10 mi, of agitated sali ne without Valsalva maneuver, (2) injection of 10 mt of agitated saline wit h Valsalva maneuver, (3) injection of 10 mt of a commercial galactose-based contrast agent (Echovist) without Valsalva maneuver, (4) injection of 10 m i, of Echovist with Valsalva maneuver, (5) injection of 10 mt of Echovist w ith standardized Valsalva maneuver, and (6) injection of 10 mi, of Echovist with coughing. Results-In 20 patients, a right-to-left shunt was demonstrated by TEE and c ontrast TCD (shunt-positive). Sixteen patients were negative in both invest igations, no patient was positive on TEE and negative on TCD, and 10 patien ts were only positive on at least 1 TCD investigation but negative during T EE. The amount of microbubbles detected in the various tests decreased in t he following order: Echovist and Valsalva maneuver, Echovist with coughing, Echovist and standardized Valsalva maneuver, saline with Valsalva maneuver , Echovist, and saline. With a time window of 20 to 25 seconds for the bubb les to appear in the TCD recording and with a sequence of first Echovist an d Valsalva maneuver and then Echovist with coughing, all shunts were reliab ly identified with a specificity of 65% compared with TEE as the traditiona l gold standard, The time of first microbubble appearance was not helpful t o distinguish between shunts detected on TEE and other shunts. Conclusions-TCD performed twice with 2 provocation maneuvers using Echovist is a sensitive method to identify cardiac right-to-left shunts also identi fied by TEE.