Is Transcranial Doppler for the Detection of Venous-to-Arterial Circulation Shunts Reproducible?

Abstract

Background: We investigated the reproducibility of contrast transcranial Doppler (TCD), a safe non-invasive test for investigation of venous-to-arterial circulation shunts (v-aCS), usually patent foramen ovale, in young stroke patients. We also investigated whether microbubble contrast was reproducible and whether the addition of blood to agitated saline contrast affected the number of microbubbles produced. Methods: TCD investigation for v-aCS was repeated in 42 patients using a standardised protocol (i) by the same investigator and (ii) by a different investigator. Agitated saline was produced by mixing saline and 1 ml of air between two 10-ml syringes. The effect of adding blood and increasing the number of agitations was evaluated by microscopy examination using a haemocytometer to assess bubble numbers and sizes. Results: TCD: no difference was found in the highest microbubble count for the same investigator and between different investigators (p > 0.05). Reproducibility for the detection of v-aCS consistent with a patent foramen ovale was also good (ĸ values >0.8). Contrast: both the number of contrast mixes before injection and the presence of blood significantly increased the number of bubbles counted. On average, 18 agitations produced 1.86 (95% CI 1.62–2.13) times more bubbles than 6 agitations. Mixtures with blood produced on average 3.8 times more bubbles (3.08–4.69). The size of the bubbles was similar for all mixtures. Conclusions: Contrast TCD is reproducible and reliable for the detection of v-aCS. The addition of blood and 18 mixes rather than 6 significantly increased the number of microbubbles produced and may increase the effectiveness of microbubble contrast.

Sleep Apnea in Patients with and without a Right-to-Left Shunt

“…TCD has been demonstrated to have high sensitivity and specificity for detection of rightto-left shunting when compared to contrast transesophageal echocardiography and is superior to transthoracic echocardiography. [15][16][17][18][19][20][21][22] Transthoracic echocardiography (TTE) with agitated saline has decreased sensitivity of detecting an intracardiac shunt in OSA patients with elevated BMI and large body habitus secondary to limited acoustic windows. 13,21 Using passage of a guide wire across the atrial septum during cardiac catheterization with intracardiac echocardiography guidance as the standard for diagnosing a PFO, TCD has a 98% sensitivity for making the diagnosis of PFO.…”

“…20,23,24 For contrast, a mixture of saline, blood, and air was used, which is reported to be more effective than agitated saline alone. 15 A mixture of 8 cc normal saline combined with 0.5 cc of air and 1 cc of blood was agitated between 2 syringes connected by a 3-way stopcock and injected into the brachial vein; embolic tracks were then counted over the middle cerebral arteries. The degree of RLS was evaluated by TCD at rest and with the Valsalva maneuver at 40 mm Hg, aided by visual feedback with a manometer device.…”

“…TCD is limited by its inability to identify the location of the shunt; however, almost all right-toleft shunts are due to PFOs or small ASDs since other etiologies, such as large trans-pulmonary shunting from pulmonary AVMs, are rare (1% of TCD exams). [15][16][17][18][19][20] Compared with heart catheterization for PFO detection, TCD is more sensitive than TEE since there is a 10% false negative rate with TEE because patients cannot perform a Valsalva maneuver with a TEE probe down their esophagus. 20,[22][23][24] The patients in our study with OSA and PFO did not undergo PFO closure, which would be needed to evaluate a cause and effect relationship.…”

Can a Peripheral Artery Be Used to Detect Venous to Arterial Circulation Shunts?

“…V-aCS may also be associated with migraine [4, 5], retinal artery occlusion [6] and decompression sickness in divers [7]. Transcranial Doppler ultrasound (TCD) provides a simple, reproducible [8] non-invasive test for v-aCS with sensitivity 68–100% and specificity 70–100% for PFO detection when compared with transoesophageal echocardiography (TOE) [9, 10]. TCD has the added advantage that it is relatively non-invasive and also detects extra-cardiac shunts such as pulmonary arterio-venous malformations [11, 12].…”

Valsalva maneuver procedures in the diagnosis of right-to-left shunt by contrast-enhanced transcranial doppler using agitated saline solution with blood as a contrast agent

“…Previous studies have demonstrated that the ideal time to perform the VM is five seconds after contrast agent (CA) infusion, but these studies were done preferentially with agitated saline solution (AS) or a galactose-based CA 1,3,4 . Studies used a small sample of a patient's own blood to obtain an agitated saline solution with blood (ASb) as a means of increasing the number of microbubbles (MBs) generated compared to AS 5 . The aim of this study was to compare two different timings of the VM with the infusion of ASb as a CA.…”