title: Contrast transcranial doppler ultrasound in the detection of right-to-left shunts : time window and threshold in microbubble numbers.
abstract: OBJECTIVE
  Cardiac right-to-left shunts can be identified by transesophageal echocardiography (TEE) and by transcranial Doppler ultrasound (TCD) with the use of contrast agents and a Valsalva maneuver (VM) as provocation procedure. Currently, data on the appropriate timing of the VM, the use of a diagnostic time window, and a threshold in contrast agent microbubbles detected are insufficient.
  
  
  METHODS
  Fifty-eight patients were investigated by both TEE and bilateral TCD of the middle cerebral artery. The following protocol with injections of 10 mL of the commercial galactose-based contrast agent Echovist was applied in a randomized way: (1) no VM, (2) VM for 5 seconds starting 2 seconds after the beginning of contrast injection, (3) VM for 5 seconds starting 5 seconds after the beginning of contrast injection, (4) VM for 5 seconds starting 8 seconds after the beginning of contrast injection, and (5) repetitive short VMs in between 2 and 13 seconds after the beginning of contrast injection. In addition to the single tests, we also tested the sensitivity and specificity of combined results of the tests with VM.
  
  
  RESULTS
  In 21 patients, a right-to-left shunt was demonstrated by TEE and contrast TCD (shunt positive). Twenty-one patients were negative in both investigations, no patient was positive on TEE and negative on TCD, and 16 patients were only positive on at least 1 TCD investigation but negative during TEE. Test 3 was the most appropriate test when combined with the results of 1 of the other tests with VM. The highest sensitivities were achieved with a diagnostic time window of 40 seconds and when the presence of a single microbubble was sufficient for the diagnosis of a shunt.
  
  
  CONCLUSIONS
  TCD performed twice with 2 provocation maneuvers with Echovist is a sensitive method to identify TEE-proven cardiac right-to-left shunts. The VM should be performed for 5 seconds starting at 5 seconds after the beginning of contrast injection.
authors.affiliation: Department of Neurology, Institute for Arteriosclerosis Research, University of Münster, Münster, Germany.
authors.forename: D W
authors.initials: DW
authors.lastname: Droste
authors.forename: K
authors.initials: K
authors.lastname: Silling
authors.forename: J
authors.initials: J
authors.lastname: Stypmann
authors.forename: M
authors.initials: M
authors.lastname: Grude
authors.forename: V
authors.initials: V
authors.lastname: Kemény
authors.forename: T
authors.initials: T
authors.lastname: Wichter
authors.forename: K
authors.initials: K
authors.lastname: Kühne
authors.forename: E B
authors.initials: EB
authors.lastname: Ringelstein
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D003287:Contrast Media; D004452:Echocardiography; D005260:Female; D006344:Heart Septal Defects, Atrial / Q000000981:diagnostic imaging*; D006801:Humans; D020766:Intracranial Embolism / Q000000981:diagnostic imaging*; D008297:Male; D008875:Middle Aged; D012680:Sensitivity and Specificity; D020521:Stroke / Q000000981:diagnostic imaging*; D013997:Time Factors; D017585:Ultrasonography, Doppler, Transcranial / Q000379:methods* / Q000592:standards; D014636:Valsalva Maneuver
chemical_list: D003287:Contrast Media