Transcranial Doppler With Microbubbles: Screening Test to Detect and Grade Right-to-Left Shunt After an Ischemic Stroke: A Literature Review.

Right-to-left shunt, mainly due to patent foramen ovale (PFO), is likely responsible for ≈5% of all ischemic strokes and 10% of those occurring in young and middle-aged adults. Randomized clinical trials demonstrated that, in selected young and middle-aged patients with otherwise cryptogenic acute ischemic stroke and high-risk PFO, percutaneous PFO closure is more effective than antiplatelet therapy alone in preventing recurrence. However, PFO is generally a benign finding and is present in about one-quarter of the population. Therefore, in clinical practice, identifying PFOs that are likely to be pathogenetic is crucial for selecting suitable patients for PFO closure to prevent recurrent stroke and to avoid potentially harmful and costly overtreatment. Contrast transthoracic echocardiography has a relatively low sensitivity in detecting PFO, whereas transesophageal echocardiography is currently considered the gold standard for PFO detection. However, it is a relatively invasive procedure and may not always be easily feasible in the subacute setting. Contrast transcranial Doppler is a noninvasive, inexpensive, accurate tool for the detection of right-to-left shunt. We conducted a literature review on the use of contrast transcranial Doppler to detect and grade right-to-left shunt after an acute ischemic stroke and present a clinical workflow proposal for young and middle-aged patients.