471-33 | The Role of Transcranial Doppler In Detecting Patent Foramen Ovale-471-33

471-33

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Transcranial Doppler (TCD) ultrasound is a noninvasive and convenient method for evaluating blood flow velocity in the intracranial arteries. TCD can also be used to detect emboli, particularly through the identification of the high-intensity transient signal (HITS), which is characteristic of embolic signals. The presence of air embolic signals in the intracranial arteries after the injection of agitated saline bubbles indicates right-to-left shunting, such as that which occurs in a patent foramen ovale (PFO). Patients with cryptogenic stroke (a stroke of unclear cause) often have PFO, with prevalence ranging from 40% to 60%. TCD with agitated saline bubbles can help diagnose and confirm the significance of PFO. The recommended injectate for this procedure is 1 mL of air mixed with 9 mL of normal saline. Ultrasound contrast agents can also be used, providing similar accuracy to agitated saline bubbles. The antecubital vein is the popular injection site, while the middle cerebral artery via the temporal acoustic insonation window is the most common location for detecting air embolic signals. The Valsalva maneuver and the Müller maneuver can enhance the detection of right-to-left shunting during TCD. TCD is useful for monitoring PFO closure and can detect residual and recurrent shunting in the short and long term. The safety of TCD with agitated saline bubbles is generally high, with adverse events being rare. TCD is typically performed in combination with other cardiac-based imaging modalities to provide additional details about concomitant cardiac and great vessel abnormalities that can inform PFO treatment decisions.

Keywords

Transcranial Doppler ultrasound

blood flow velocity

intracranial arteries

emboli detection

high-intensity transient signal

air embolic signals

right-to-left shunting

patent foramen ovale

cryptogenic stroke

agitated saline bubbles