Introducing the Lucid M1 Transcranial Doppler System™

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AAN’s Guidelines for the Use of TCD

Acute Ischemic Stroke Detection

TCD is a convenient, low-cost, and rapidly repeatable test compared to MR and CT in suspected ischemic stroke. However high sensitivity and specificity are demonstrated only in the proximal anterior circulation. In a cohort of 48 patients with angiographic proven occlusion TCD had an overall sensitivity of 83% and specificity of 94%, with sensitivity optimal in the proximal ICA (94%) and MCA (93%), and significantly less in the terminal VA (56%) and BA (60%).1

Abnormal ICA, MCA, or ACA Waveform Types

Dampened signal: Pulsatile flow with normal flow acceleration and decreased MFV ( 30% difference between hemispheres); any PI values.

Blunted signal: Delayed flow acceleration with stepwise maximum velocity arrival during mid to late systole compared with contralateral side and focal decreased MFV and positive end-diastolic flow Minimal signal: Presence of a flow signal with no end diastolic flow; PI 1.2.

Absent signal: No detectable flow at 40- to 65-mm depths (toward the probe) via transtemporal window (double-checked with insonation from contralateral window across midline at depths of 80 to 100 mm).2

1 Kassab MY, Majid A, Farooq MU, et al. Transcranial Doppler: an introduction for primary care physicians. J Am Board Fam Med. 2007;20(1):65-71.
2 Demchuk, et. Al Specific Transcranial Doppler Flow Findings Related to the Presence and Site of Arterial Occlusion. Stroke. 2000;31:140-146.

Right to Left Cardiac Shunts

TCD offers a noninvasive method to assess and classify the grade of shunting through a microembolic signals (MES) grading scheme, which can also help stratify patients according to risk of stroke.1

Contrast TCD is comparable to contrast TEE for detecting right to left shunts due to PFO (Type A, Class II evidence). TEE is superior to contrast TCD since it provides direct anatomic information regarding the site and nature of the shunt or presence of an ASA. While the number of microbubbles reaching the brain can be quantified by TCD, the therapeutic impact of this additional information is unknown (Type U).2

The test is positive for right-to-left shunt if a shower of high signal material (air) is detected in the MCA by TCD five to 10 seconds after the intravenous injection of 10 mL of agitated saline. If this shower of air emboli is detected after a minute of injection, it might indicate the presence of a pulmonary shunt; a diagnosis that cannot be obtained by TEE.2

INDICATION SENSITIVITY (%) SPECIFICITY (%) REFERENCE STANDARD
Right to Left Cardiac Shunts 70-100 >95 Transesophageal echocardiography
1 Naqvi J, Yap KH, Ahmad G, Ghosh J. Transcranial Doppler ultrasound: a review of the physical principles and major applications in critical care. Int J Vasc Med. 2013;2013:629378.
2 Neurology 2004;62(9):1468

Detection of Cerebral Microemboli

TCD is probably useful to detect cerebral microembolic signals in a wide variety of cardiovascular/ cerebrovascular disorders/procedures including Coronary Artery Bypass Graft (CABG), Coronary intervention, Carotid Endarterectomy (CEA) and Trans Aortic Valve Repair (TAVR) procedures. (Type B, Class II-IV evidence). 1

INDICATION SENSITIVITY (%) SPECIFICITY (%) REFERENCE STANDARD
Cerebral Microembolization  –  – Experimental model, pathology,
magnetic resonance imaging,
neuropsychological tests

However, data at present do not support the use of TCD for diagnosis or for monitoring response to antithrombotic therapy in ischemic cerebrovascular disease in these settings (Type U).1

Microemboli traveling along an insonated vessel will appear as high intensity transient signals (HITS) on the TCD spectrum.2

1 Neurology 2004;62(9):1468
2 Kassab MY, Majid A, Farooq MU, et al. Transcranial Doppler: an introduction for primary care physicians. J Am Board Fam Med. 2007;20(1):65-71.

Subarachnoid Hemorrhage

The delayed vasospasm of the cerebral vasculature is angiographically proven in up to 70% of cases of SAH and usually occurs 4 to 17 days after hemorrhage. It has significant implications on mortality and morbidity with approximately 25% of SAH patients developing delayed ischemic deficits due to vasospasm.1

Angiography is the gold standard for detecting vasospasm but is an invasive technique and unsuited to dynamic monitoring. TCD, however, is non-invasive, portable, and able to dynamically assess vasospasm and monitor the effectiveness of intervention. Conventionally, serial TCD measurements are performed daily after SAH.1

Vasospasm following subarachnoid hemorrhage is typically associated with increase flow velocity (FV) within intracranial vessels.2

TCD identifies MCA and BA vasospasm with a high sensitivity and specificity. A systematic review of 26 studies comparing TCD with angiography found that MCA MFV >120 cm/s was 99% specific and 67% sensitive to angiographic vasospasm of ≥ 25%. In a retrospective study of 101 patients, MCA MFV >120 cm/s was 72% specific and 88% sensitive for ≥33% angiographic vasospasm with a negative predictive value (NPV) of 94% for MFV <120 cm/s. In the same study, MFV >200 cm/s was 98% specific and 27% sensitive with a positive predictive value (PPV) of 87% for angiographic vasospasm of ≥33%. Therefore, MFV <120 cm/s and >200 cm/s may accurately predict absence and presence of angiographic MCA, vasospasm, respectively. 2

Mean FV obtained by TCD was found to correlate well with the residual lumen diameter of the MCA, and it has high specificity (100%) and good sensitivity (58.6%) in diagnosing vasospasm only due to the involvement of vessels that are not evaluated by TCD at times.1

INDICATION SENSITIVITY (%) SPECIFICITY (%) REFERENCE STANDARD
Vasospasm after Spontaneous
Subarachnoid Hemorrhage
69 83 Conventional angiography
Intracranial ICA 100 97  –
MCA 100 93  –
ACA 71 85  –
1 Naqvi J, Yap KH, Ahmad G, Ghosh J. Transcranial Doppler ultrasound: a review of the physical principles and major applications in critical care. Int J Vasc Med. 2013;2013:629378.
2 Kassab MY, Majid A, Farooq MU, et al. Transcranial Doppler: an introduction for primary care physicians. J Am Board Fam Med. 2007;20(1):65-71.

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