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Assessment of Right-to-Left Shunts Using Contrast Transcranial Doppler Ultrasound – Advantages and Reliability of the Method

Zhenya Marinova, Roksana Tsvetanova, Elena Ivanova, Tsvetan Popov, Antoniya Kisheva

Abstract

Introduction: It is estimated that 25-30% of the world’s population has patent foramen ovale (PFO). The majority of these people have no problems associated with this condition. However, in recent years, it has been suggested that patients with cryptogenic strokes or transient ischemic attacks (TIA) have a higher prevalence of PFO. 
Contrast transcranial Doppler (cTCD) ultrasonography is a very sensitive, noninvasive, portable technique which can be used for evaluation of right-to-left shunt (RLS) via a PFO.

Materials and Methods: In this study, a group of 19 patients, 9 males and 10 females, at a mean age 45±2 with cryptogenic ischаemic stroke were investigated by cTCD of both middle cerebral arteries (MCA). The technique is performed with intravenous application of 10 mL agitated saline without and subsequently with the Valsalva maneuver (VM).  The appearance of bubbles in the MCA is detected, thereby suggesting the diagnosis of RLS. Magnetic resonance imaging (MRI) of the brain was performed.

Results: In approximately 58% of the evaluated patients microembolic signals (MES) were detected in MCA suggesting existence of RLS, which was confirmed by transesophageal echocardiography (TEE). In 7 patients, MRI revealed multiple ischaemic lesions.

Conclusion: PFO appears more often in patients with cryptogenic stroke than in the general population. The cTCD technique has a similar sensitivity and specificity as cTEE, which is considered a standard method for detecting RLS. But while routine TEE application is often limited in patients with acute stroke because of acute illness, coagulopathy, and lack of patient cooperation, TCD is noninvasive and reportedly safe in patients with embolic stroke of undetermined source (ESUS). In summary, the availability of simple highly sensitive diagnostic techniques such as TEE and TCD for RLS assessment seems to supply a large amount of data on the relevance in the treatment of this condition and both methods must be considered complementary.


Keywords

patent foramen ovale, transcranial Doppler sonography, right-to-left shunt, stroke


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