Detection of cardiac right-to-left shunts by contrast-enhanced harmonic carotid duplex sonography.
OBJECTIVE
Paradoxical embolization by cardiac right-to-left shunts (RLS) is increasingly recognized as an important factor for embolic stroke. Contrast-enhanced transcranial Doppler sonography (ce-TCDS) is an established diagnostic tool for RLS detection but is frequently limited because of an inadequate temporal acoustic bone window. The purpose of this study was to determine whether extracranial sonography (ECS) using harmonic frequencies improves detection of RLS.


METHODS
Extracranial color duplex sonography using harmonic frequencies enables visualization of even single ultrasound contrast agent microbubbles because of oscillation. Patients with stroke and positive RLS findings on transesophageal echocardiography underwent a simultaneous extracranial and transcranial sonographic examination of the proximal common carotid artery (CCA) and middle cerebral artery (MCA) on the same side. A Valsalva strain was performed for 10 seconds after intravenous bolus injection of a galactose-based nontranspulmonary contrast agent. The B-mode frame sequences of the transverse plane of the CCA obtained by harmonic ECS and the ce-TCDS recordings of high-intensity transient signals from the MCA were analyzed offline.


RESULTS
In all patients with RLS, the shunts could be identified by harmonic ECS. A close correlation could be seen between the count of visualized microbubbles in the CCA and the number of high-intensity transient signals detected on ce-TCDS in the ipsilateral MCA.


CONCLUSIONS
The results of this study indicate that contrast-enhanced ultrasound harmonic imaging of the CCA using a Valsalva strain might be an optional screening tool for detection of cardiac RLS in patients with insufficient acoustic bone windows.
Draganski
Bogdan
B
Department of Neurology, University of Regensburg, Germany. b.draganski@fil.ion.ucl.ac.uk
Blersch
Wendelin
W
Holmer
Stefan
S
Koch
Horst
H
May
Arne
A
Bogdahn
Ulrich
U
Hölscher
Thilo
T
Schlachetzki
Felix
F
D002343:Carotid Artery, Internal / Q000000981:diagnostic imaging*; D003287:Contrast Media; D017548:Echocardiography, Transesophageal; D019320:Embolism, Paradoxical / Q000000981:diagnostic imaging / Q000209:etiology; D005240:Feasibility Studies; D006344:Heart Septal Defects, Atrial / Q000150:complications / Q000000981:diagnostic imaging*; D006801:Humans; D002542:Intracranial Embolism and Thrombosis / Q000000981:diagnostic imaging / Q000209:etiology; D008297:Male; D045423:Microbubbles; D008875:Middle Aged; D011134:Polysaccharides; D018709:Statistics, Nonparametric; D018615:Ultrasonography, Doppler, Color; D017585:Ultrasonography, Doppler, Transcranial
D003287:Contrast Media; D011134:Polysaccharides; C040642:SHU 454